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HomeMy WebLinkAboutLime Village nano grid 1995Conceptual Design and Economic Evaluation of "Nano-grid"Power Generation and Distribution Systems for Lime Village,Alaska DRAFT REPORT 18 January 1995 Karin Holser Delta Institute Wasilla,Alaska George Menard InverTech Alaska (703)S¢9-G96?Trapper's Creek,Alaska Alexandra Hill ISER.University of Alaska Anchorage,Alaska George Hagerman SEASUN Power Systems Alexandria,Virginia INTRODUCTION Background Lime Village is a predominantly Den'ina Athabaskan community located on the Stony River, approximately 60 miles from its confluence with the Kuskokwim River,in the western foothills of the Alaska Range (Figure 1).The nearest other Middle Kuskokwim villages are Stony River, Sleetmute,and Red Devil.Lime Village is 120 air miles south of McGrath.which is the commercial and transportation hub of the Middle and Upper Kuskokwim region,and 180 air miles west of Anchorage.Sparrevohn Air Force Station,now partly an RCA communications facility,is located 20 air miles south of Lime Village,a six-hour round trip by dogsled or snow machine. Lime Village is one of the most geographically isolated and culturally traditional communities in Alaska.The local economy still has a large subsistence component;all villagers who are able hunt and fish,sharing with those who cannot.Most household cash income is from transfers such as Permanent Fund and village corporation dividends,as well as Social Security and disability payments.Wage employment in Lime Village is limited and seasonal.A detailed account of Lime Village's cash economy is given in Reference 1,which estimates average household income from all sources to be approximately $11,700 per year.A complete description of the subsistence economy of Lime Village,including land use and resource allocation,is given in Reference 2. The 1990 census counted 42 residents in 14 households (Reference 1).The number of occupied residences varies throughout the year due to the seasonal mobility of the villagers.This study identified 20 households that are existing or likely to be built within the next few years. i /|/ Present Energy Supply Situation Houses are heated with wood,which residents cut themselves or for their neighbors.Propane,wood,or Coleman stoves are used for cooking.Although some houses are lit by Coleman lanterns or Kerosene lamps,most have electric lights powered by personal generators.A November 1992 survey of 11 households by Alexandra Hill reported 6 households with generators (Reference 1). In July 1994,a similar survey by Ms.Hill and Karin Holser identified 9 out of 13 households with generators.The most common sizes were 650 and 1800 watts.One resident uses a 4 kW generator to power a washing machine,and another uses a 5 kW generator for a large freezer (14.8 cu.ft). The earlier survey estimated that the average household spent approximately $50 to $130 per month on energy for lighting and generators ($600 to $1,560 per year or 5%to 13%of annual income). The more recent survey indicates a similar level of expenditure.For example,one household operates a Honda 1800-watt generator 10 hours per day in the winter (primarily for lighting)and 8-10 hours per day in the summer (primarily for two 15 cu.ft freezers).This generator is reported to run 8 hours on 1.25 gallons of gasoline,a fuel consumption rate of 0.16 gallons per hour (GPH), half of its full-load rating.Assuming that the generator runs 8 hours per day,365 days per year, with a gasoline price of $4.00/gal,the annual fuel bill for this household is $1,825.Another household operates a Honda 650-watt generator 20 hours per week in the summer and 50 hours per week in the winter.This generator runs for 6 hours on 1/2-gallon of gasoline,a fuel consumption rate of .083 GPH.Assuming that this generator runs an annual average of 35 hours per week (5 hours per day),the annual fuel bill for this household is $608. Scope of This Study Two previous studies have been conducted on energy supply options that would reduce the amount of money that Lime Village residents now spend on gasoline-powered generators.The first (Reference 3)recommended a centralized diesel generation system with an annual average output of 30 kW,distributed over a village utility grid,or "micro-grid".The second study (Reference 4) recommended that each individual household have its own photovoltaic (PV)array consisting of sixteen 48-watt panels on a dual-axis tracker,a 2500-watt inverter.and a 740 ampere-hour battery, with an 1800-watt gasoline-powered generator for back-up battery charging. This report updates the previous two studies and develops a third alternative,which consists of six hybrid PV/diesel "nano-grid”systems,each serving a cluster of three or four buildings.This approach combines the economy and maintainability of a centralized micro-grid system with the supply/demand matching and modular expandability of individual household systems. The next section of this report describes the computer simulation program that was developed to model the performance of the nano-grid and individual household PV systems.The third section describes the electrical load profiles that were used as input to the model.The fourth section presents the results of trade-off studies,where the model was used to determine the optimum number of PV panels and battery storage capacity as a function of the number of households connected to a nano-grid.System maps are presented,showing the lay-out of each of the six nano- grids.The last section compares the life-cycle economics,considering both capital and operating costs,of each of the three alternatives:centralized diesel,nano-grid,and individual household. SYSTEM SIMULATION MODEL PVFORM and TMY Data PVFORMis a flat-plate photovoltaic simulation model developed by Dave Menicucci at Sandia National Laboratories.Albuquerque (SNLA),with programming support trom James Fernandez of the New Mexico Engineering Research Institute (Reterence 5).PVFORM Version 3.3,which was used for this study,incorporates an anisotropic radiation model developed by Richard Perez of the State University of New York at Albany,and a PV cell temperature model developed by Martin Fuentes of SNLA.The radiation model accounts tor direct and diffuse radiation,as well as radiation reflected from the ground,which can be significant during times of snow cover.The cell temperature model determines the combined effect of solar insolation,air temperature,and wind speed on the operating temperature and electrical output of a PV panel array,depending on the height of the array above the ground and how the panels are mounted. A variety of PV array mounting configurations can be modelled,ranging from fixed-tilt to dual-axis tracking,the latter of which was used throughout this study.Hourly weather data required as input to the model consist of four parameters:direct solar radiation (radiant energy received directly trom the sun by a surface normal to the sun's rays,as measured by a pyrheliometer),global radiation (sum of direct and diffuse radiation received on a horizontal surtace,as measured by a pyranometer),air temperature,and wind speed.The best source for such hourly input data is the ical meteorological year (TMY)data derived from the SOLMET data base.typ gical year (TMY)bbe Solent 2, In response to the Arab oil embargo of the mid-1970s and consequent interest in the development of solar energy technologies,the National Oceanic and Atmospheric Administration upgraded its solar measuring instrumentation,standardized recording procedures,rehabilitated previously collected data,and made all data available in a common format called SOLMET.The original SOLMET data base consisted of hourly solar radiation and associated weather data measured at 27 sites throughout the United States.Data from these sites were rehabilitated as required,and missing values were replaced with estimates derived from statistical models.The same estimation techniques also were used to generate complete SOLMET data for 222 additional sites,including 13 sites in Alaska. The data file for each SOLMET station contains approximately 20 years of hourly data,consisting of more than 175,000 records,spanning an entire high-density (1600 bpi)computer tape reel. Processing this quantity of data requires a large mainframe computer and a nine-track tape drive, neither of which are routinely available to most engineers and designers.In order to reduce the quantity of data to a workable amount for desktop computer applications,SNLA was contracted by the U.S.Department of Energy to develop a "typical"year of weather data to represent each SOLMET station (Reference 6). A typical meteorological year (TMY)data set for a given station is constructed from twelve months of actual data retrieved from different years within the SOLMET data base.A specific month from a particular year is selected based on how closely its weather statistics match the long-term statistics for that month over the entire 20-year period (see Reference 7 for a complete description of the selection procedure).Because the months are selected from different years,data-smoothing routines are used to avoid abrupt weather pattern changes between the last days of one month and the first days of the next. Mcgrath is the closest SOLMET station to Lime Village,and the TMY data set for that station was purchased for this study from the National Climatic Data Center in Asheville,North Carolina.The TMY for Mcgrath consists of the following specific months:Jan 62,Feb 68,Mar 75,Apr 71, May 75,Jun 68,Jul 71,Aug 64.Sep 53,Oct 63,Nov 64,and Dec 74. Flooded Lead-Acid Battery Model PVFORM Version 3.3 models a back-up generator by applying a battery equalizing charge at some user-specified interval of days,or whenever the battery state of charge falls below a user-specified level.Close examination of the PVFORM hourly output file indicates,however,that upon application of the equalizing charge,the battery is considered to be fully charged immediately at the end of the hour. In a real hybrid PV system,battery charging by the generator is not instantaneous.Rather,the charging current is typically limited to a C/10 rate or less,where C is battery capacity.For example, a 24-volt battery having a capacity of 1,500 ampere-hours (36,000 watt-hours)should be charged at a rate no higher than 3,600 watts,no matter how large the generator.This provides tor more efficient charging (by reducing battery terminal voltage elevation,thereby maximizing the charging current for a given power input),and prolongs battery life by avoiding heating and thermal distortion of the lead plates. Other important battery characteristics that are not modelled by PVFORM Version 3.3 are: ¢voltage elevation during charging and voltage depression during discharging,which influence the current flow into or out of the battery -the rate at which state of charge changes -for a given power input or drain *energy losses during charging,such as heating and water electrolysis (gassing)as a battery approaches a full state of charge *the effects of battery cell temperature on voltage elevation while charging and voltage depression while discharging Furthermore,while inverter efficiency is correctly modelled as a function of inverter load,there is no similar model for battery charger etficiency when the generator is operating. As a result of the above omissions,PYFORM does not provide a realistic estimate of the number of hours that a generator must run during the year,which in turn determines annual fuel consumption and the required generator maintenance/overhaul schedule.Consequently,SEASUN Power Systems had to develop a computer model to simulate the charging and discharging of a flooded lead-acid battery system.This was not anticipated in our original proposal for this study and required considerable time and effort. Lead-acid battery characteristics incorporated into the model include cycle life and a function of cycle discharge depth and battery terminal voltage as a function of the battery's state of charge and the rate at which it is being charged or discharge.Data used for this study are shown in Figure 2. When cycle life is plotted on a base-10 logarithmic scale.it is a linear tunction of cycle depth.Thus even though only two data points were available tor Pacific Chloride batteries,these were sufficient to establish a functional relationship.Note that using the cycle-life characteristics of Pacific Chloride rather than Exide batteries provides a conservative estimate of battery life.Both brands are comparably priced. The data for battery voltage as a function of battery state of charge were taken trom Reference 8. Second-order polynomial curves were fitted to the discharging data,while third-order polynomial curves were fitted to the charging data.In both cases,the polynomial coefficients were themselves fitted as second-order polynomial functions ot the natural logarithm of the charge or discharge rate, where the rate is specified in terms of battery capacity divided by power in or out.As shown in Figure 2,the fit ot these curves to discharging data is quite good.whereas the fit to charging data becomes poorer as the battery approaches a full state of charge,particularly at high charging rates(C/5 and C/10).The typical charging regime modelled in this study calls tor a C/10 rate up to 0.85 normalized state of charge,followed by a C/20 rate,at which point the fit is much better. The rate at which a battery's state of charge changes for a given power input or drain depends on voltage,which itself depends on the state of charge.This relationship can be expressed as an ordinary differential equation.In the model developed by SEASUN Power Systems,this equation was solved numerically using a 2nd-order Runge-Kutta solution.Reference 8 reports that a 2nd- order solution is very nearly as accurate as a 4th-order solution but takes much less computer time. To validate this model,a single battery discharge-charge cycle was simulated to examine the effect of charge or discharge rate,battery temperature,and charging energy losses to heat and gassing. Results are presented in Figures 3 through 6 and explained below. Figure 3 plots cell voltage and state of charge (SOC)over time for a C/10 discharge rate and three different charging regimes:constant (C/10),2-stage (C/10 up to SOC =0.85,followed by C/20 uptofullcharge),and 3-stage,which consists of accelerated charging at a C/5 rate up to SOC =0.75, followed by the 2-stage regime described above.Note that with the constant charging regime,the charging part of the cycle takes longer (9.0 hrs)than the discharging part (7.7 hrs),even though the power in is the same as the power out.This is a consequence of the lower charging current due to voltage elevation.Also note that the 2-stage charging regime is slightly more efficient,because voltage elevation is not as great during the last two hours of charging.Likewise,the accelerated charging regime is slightly less efficient,due to increased voltage elevation during the first few hours of charging. Cycle efficiency,before accounting for gassing and heat losses,is 85%to 87%(depending on charge regime)at 78°F.At lower temperatures,cycle efficiency is significantly less (79%to 81%at 34°F). This is because electrolyte viscosity increases with decreasing temperature,lowering the rate at which charged ions move toward or away from the battery plates,leading to charge deficiency at the plates (increased voltage depression)during discharge and charge accumulation (increased voltage elevation)during charge.Thus the 2-stage charging regime takes 10.4 hours at 34°F, whereas it only takes 9.8 hrs at 78°F. With a constant charging current,a battery's state of charge does not indefinitely increase in a linear tashion but asymptotically approaches a "saturated"state,and increasing amounts of energy are lost as heat or to the electrolysis of water (gassing)in the batteries sulfuric acid solution.Over time this causes water to be lost from the battery cells,which must be periodically replaced.Since electrolysis produces hydrogen and oxygen,battery enclosures must be well ventilated and free of any ignition source. Gassing and heat losses are often reterred to as Coulombic losses,because they only occur during the charging part of the battery cycle.For this study,battery Coulombic losses were modelled using an equation from a U.S.Coast Guard report on hybrid power systems for remote aids to navigation (Reference 9),which is based on a generator charging regime that is reasonably similar to the one modelled in this study (Figure 4).The results of incorporating this equation into the single-cycle battery model are plotted in Figure 5.Cycle efficiency in this case is 78-80%at 78°F and 73-74% at 34°F. Finally,as previously stated,voltage depression while discharging is less at lower discharge rates, and this is shown in Figure 6,which models a C/40 discharge rate.Cycle efficiency is now 83-85% at 78°F and 80-81%at 34°F,signiticantly better than with a C/10 discharge rate.Thus for a given load,a larger battery may be more economical (up to a point)because of increased cycle efficiency PVGENBAT For this study,PYFORM was configured to generate a disk file listing the hourly direct-current (DC)power output of a PV panel in terms of watts per square meter of panel area.Hourly output files were generated for two different ground reflectivity conditions:snow cover (having an albedo of 0.85)and grassy tundra/meadow (having an albedo of 0.15).Snow cover was assumed to exist from November through March,while grassy tundra/meadow was assumed to exist from April through October.This is slightly conservative in estimating the amount of sunlight reflected onto the panels from the ground,since snow cover typically exists from mid-October through mid-April. The appropriate months from the PVFORM output files for each of the two different ground conditions were merged together,along with three different electrical load profiles:one for winter (November through February),one for spring and fall (March-April and September-October),and one for summer (May through August).The next section of this report describes these three seasonal load profiles. Additional parameters merged into this file are the tracker motor load (assumed to be 5 watts whenever PV array output is not zero)and the internal cell temperature of the lead-acid battery (assumed to be 34°F in the winter,56°F in the spring and fall,and 78°in the summer). The above-described file was then input to PVGENBAT,a simulation program developed by SEASUN Power Systems,incorporating the flooded lead-acid battery model described earlier and power control algorithms based on programmable charge controllers and load centers that are now available commercially. ELECTRICAL LOAD PROFILES Residential In July 1994,Karin Holser and Alexandra Hill visited Lime Village and interviewed residents regarding their present electricity use patterns and what changes they would make if more electric power was available.The predominant residential loads are lighting in the winter and freezers in the summer,although more households now have electric lights than have freezers. There are seven relatively new houses built with funding from the U.S.Department of Housing and Urban Development (HUD);two have 3 bedrooms,and five have 2 bedrooms.Each bedroom has three 13-watt compact fluorescent fixtures,for a total of 40 watts per bedroom.In addition to the bedrooms,there is a main living room with a kitchen/dining area,which has two fluorescent ceiling fixtures,each with two 40-watt tubes,for a total of 160-watts of main room lighting.There is also a compact fluorescent tixture in what originally was intended as a bathroom,but in Lime Village this room is now used as an unlighted storage closet. In addition to the seven HUD homes,five other houses were visited that had incandescent main room lighting as follows:one 175-watt lamp,two 75-watt lamps,one 75-watt lamp,two 100-watt lamps,and three 100-watt lamps (only two are used at a time).Three households had no electric lights and used kerosene lamps or Coleman lanterns. The typical profile of main room lighting throughout Lime Village is nine to twelve hours per day during the winter (3 to 4 hrs in the morning,6 to 8 hrs in the evening)and from sunset to midnight (if used at all)during the summer.Bedroom lighting is used for an hour in the morning and an hour or two at night in winter,and not at all during the summer. Five freezers were identified:one 5 cu.ft,one 10 cu.ft,one 14.8 cu.ft,and two 15 cu.ft (belonging to a single household).The 10 cu.ft freezer compressor draws 120 to 160 watts when running,and the 14.8 cu.ft draws 240 watts.No information was available on compressor run time, but the household with two 15 cu.ft freezers reported running a 1800 watt generator 8-10 hours per day in the summer,primarily to meet freezer demand. Several homes reported television (TV)usage,ranging from "occasional"to "several hours",with two households specifying 2 to 4 hours in the evening.This included one residence without electric lighting,which had a portable battery-powered TV.At least two households have video cassette recorders (VCRs).Nearly every household has a radio that in some cases is on all day. At least five households have washing machines.One is used to wash 4 to 6 loads every other day; another is used all day every 7 to 14 days.No information was available on washing machine power requirements.(In final report,include Home Power data on washing machine energy consumption, including Wattevr Works high-efficiency motor retrofits.) A variety of small kitchen appliances (toaster,microwave,coffee maker,waffle iron,mixer)are occasionally used in some households.Power tools and power tool rechargers also are used in some homes,particularly while the generator is running a large load like a freezer or washing machine. The residential load profiles input to the simulation program are plotted in Figure 7.Main room lighting is assumed to be 160 watts (as in the HUD homes;also sufficient to power two 75-watt incandescent bulbs),on for 11 hours per day in the winter,6 hours per day in the spring and fall, and 3 hours per day in the summer. Bedroom lighting is assumed to total 40 watts (three 13-watt compact fluorescent lamps or a 40-watt incandescent bulb)for three hours in the winter,two hours in the spring and fall,and one hour in the summer.Freezer compressor energy consumption is estimated to be 400 watt-hours in the winter,600 watt-hours in the spring and fall (the advertised energy consumption of an efficient Sun-Frost 10 cu.ft freezer or 16 cu.ft refrigerator/freezer at 70°F),and 800 watt-hours in the summer.A total kitchen appliance load of 100 watt-hours is assumed at each meal;this could be a 600-watt coffee maker and a 600-watt microwave oven each running ten minutes,or a 1200-watt toaster running ten minutes).Finally,a 20-watt radio is assumed to be on all day. Two important items are missing from the basic residential load profiles of Figure 7:a television and a washing machine.TV power consumption varies greatly depending on size and make. Estimates given in Home Power magazine range from 44 watts for a 9-inch color TV to 150 watts for a 27-inch color TV.A VCR can consume up to 50 watts.In most Lime Village households, main room lighting is reduced or switched off entirely when the residents are watching TV.In order to estimate the effect of TV watching,100 watts was modelled as an optional addition to the basic residential load protile from 7:00 PM to 11:00 PM during all seasons of the year. Regarding washing machine usage,there is considerable interest among the villagers in having a community washateria,probably in the existing well house,possibly elsewhere depending on whether the water supply is relocated.Ideally this would contain two washing machines,two dryers (electric or propane,possibly augmented by waste heat from a generator),lighting,and one or two hot showers,as well as a Toyo/Monitor heater.Insufficient data were available to develop a washateria load profile,but assuming this becomesa reality,then washing machines would not be a residential load for most households,with the possible exception of three to six remote homes located upriver from the HUD tract. Several residents expressed interest in electronically controlled oil-burning radiant heaters (Toyo/Monitor).The run time of these units depends on the temperature desired,the amount of space to be heated,and the degree of home insulation and weathertightness.Such an assessment was beyond the resources available for this study,and the load profiles of Figure 7 assume that existing wood stoves would continue to be used for residential space heating. Village Office,Medical Clinic,and Church It is assumed that the community hall would be used as a meeting place for the Lime Village Traditional Council two hours per night (7:00 PM to 9:00 PM),five nights per week.The electrical load at that time would consist of the following continuous loads:a 75-watt Monitor heater,three 40-watt fluorescent ceiling fixtures (similar to the HUD homes),a 40-watt computer central processing unit (CPU),and a 50-watt computer monitor.In addition,the following intermittent loads would be on 50%of the time when the office is open:a 30-watt hard disk drive,a 10-watt fax/modem,and a 40-watt printer. The medical clinic is assumed to be open from noon until 4:00 PM Monday through Friday.Electrical loads during that time (lighting and computer)are the same as those of the village office. In addition,a fourth 40-watt fluorescent ceiling fixture would be on,and a Sun-Frost refrigerator would be used for vaccine storage,consuming 160 watt-hours per day at 70°F. The church requires only a few compact fluorescent bulbs (probably no more than 75 watts)for two hours on Sunday.This is negligible compared with the clinic load,and could be met if just one of the clinic's examining rooms was not used for one afternoon a week,which seems entirely plausible. Other Community Buildings As previously mentioned,there is considerable interest in a community washateria,which would serve as a village laundromat and shower point.This would presumably be located in the existing well house,although relocation of the water supply tarther away from the river is also being considered.In addition to the appliances already mentioned for the washateria,a submersible shallow well pump would be required to supply water to the washers and showers. The present well house is located near the village air strip,and a nano-grid designed for a washateria at this location could be sized to also provide runway lighting,which would be a major safety improvement,and to provide light and heat for the Department of Transportation maintenance shed.There are four lights in this shed,and space heaters would be needed to warm up the runway grader before starting,since the grader's engine block heaters do not work. The largest community electrical loads are the school complex and the Unicom telephone utility, both of which have their own dedicated diesel generator systems.The school system is 12 kW and the Unicom system is 8.5 kW.Each system has two identical generators,operating one at a time while the other is being serviced,with a roughly equal amount of run time on each generator. The Iditarod Area School District currently operates and maintains a 12 kW diesel system to supply power for the school and teacher's quarters.In Telida,where the school building is identical to the one in Lime Village,the School District recently switched from generating their own power to purchasing power.Telida school power purchases were 11,474 kWh in 1990-91 and 13,245 kWh in 1991-92 (Reference 1).This study assumes that with centralized diesel power generation,the Lime Village school and teacher's house would have the same average consumption as in Telida, or 12,360 kWh/yr.A description of school loads is given below. School lighting consists of 33 40-watt fluorescent lamps and 8 incandescent lamps (60 to 100 watts), for a total lighting load of at least 1800 watts.Because many homes do not have adequate lighting, school lights must be on 12 hours per day so students can do homework there at night.Because the school generator now runs continuously,lights are often left on 24 hours per day.School electronic equipment includes a 200-watt TV,a 16-watt VCR,seven computers,two to three of which are in use at any given time,a laser printer and a fax machine,as well as a copier that draws 400 watts on standby and 1360 watts when copying. The school is heated by a forced-air,oil-burning furnace.The blower motor draws 730 watts and runs continuously 24 hours per day.The burner draws 290 watts,running intermittently for a totalofabout12hoursperdayinthewinter.The power draw and run time for the furnace oil pump are unknown.Additional electrical loads at the school are a 4500-watt water heater,a submersible shallow well pump,an 11 cu.ft retrigerator/treezer,electronic ignitors for the propane stove and oven,a cotfee maker,a vaccuum cleaner,a satellite dish,and school shop equipment,including atablesaw.drill press.assorted hand power tools,and an automotive-type battery charger. The teacher's house has six rooms to light,as well a stairway,entry way,and outside light. Additional electrical loads include.washing machine,16 cu.ft refrigerator,19 cu.ft freezer, microwave oven,cotfee maker,TV/VCR,and stereo.As in the school building,the teacher's house has an oil-fired furnace and an electric water heater. In interviews conducted for this study,Unicom reports a continuous equipment load of 3.2 kW,with an additional 1.5 kW required in winter to power a 1500-watt space heater for the utility building. Unicom also claims,however,that their 8.5 kW generator has no surplus capacity.Reference 2 reports a Unicom load of 6 kW.This is assumed to be their summer peak,while their winter peak is assumed to be 7.5 kW,to account for the space heater. Reference 2 reports that Unicom's energy consumption averages 3000 to 3500 kWh per month. This study assumes that Unicom's annual electricity consumption would be in the midpoint of this range.or 39,000 kWh/yr. Except for the 240 VAC space heater and a few 120 VAC outlets,Unicom's equipment is 48 volts direct current (VDC).Considerable energy is lost in rectifying the generator's AC output,and any nano-grid designed for Unicom should power this equipment directly off a 48-volt battery. Developing load profiles tor the washateria/air strip,the school complex,and Unicom require several preliminary steps beyond the resources available for this study.The first step would be to identity specific efficiency improvements to the school complex and Unicom that would enable the existing generators to operate far fewer hours,particularly when cycled through an inverter/battery system,with or without supplemental PV generation.If the generators are not running continuously,then it may no longer be necessary to maintain two identical generators,and these might possibly be leased or sold on tavorable terms for other village nano-grids.Although these are too large for the optimized residential nano-grids,they might be suitable for the washeteria or air strip systems. Successful implementation of the residential nano-grids should greatly reduce the school's lighting and heating load,since students would then be able to do their school work at home,but this must be demonstrated before a school nano-grid can be designed.The village's decision regarding relocation of the water supply must be made before a washeteria nano-grid can be designed, particularly since building insulation and weather-tightness will influence the electrical loads associated with space and water heating.An associated issue is whether the washateria nano-grid should also include the air strip and maintenance shed.Finally,the Unicom nano-grid should consider diesel generator waste heat recovery as a means of eliminating their 1.5 kW space heater. 10 NANO-GRID OPTIMIZATION Major System Components The major electrical components of any hybrid PV system,whether for an individual household or a nano-grid,are a solar panel array,a flooded lead-acid storage battery,a gasoline or diesel AC generator,a charge controller and load management center,and a DC-AC inverter (which also contains an AC-DC rectitier for battery charging by the generator).An attractive feature of the nano-grid concept is that all of these components would be located in a pre-fabricated,insulated utility shed,specifically designed to accommodate them.Unlike individual household PV systems, there would be no potential fire or electrical safety hazards introduced into the home. While household PV systems often are configured to run a combination of DC and AC loads,each nano-grid utility building would produce AC power only.Each household would simply require an AC service entrance (mains panel)and meter,identical to what would be required for the centralized diesel alternative. It should be noted that only the seven HUD homes and one other residence in Lime Village now have internal house wiring.As with previous studies (Reterences 2 and 3),this study assumes that internal wiring and other modifications needed to utilize electric power would be borne by the property owners. The PV array modelled in the optimization study consists of BP Solar panels each having a nominal peak output of 75 watts.Panel manufacturers are moving away trom 45-to 55-watt modules,which until now have been the workhorses of the residential PV industry,towards increased production of 75-to 85-watt modules.British Petroleum's 75-watt panel has an efficiency of 12.0%,and currently offers the best value at a wholesale price of $5.00 per peak watt. Cost and weight data for PV array support structures are based on a Watt-Sun dual-axis tracker, manufactured by Array Technologies of Albuquerque,New Mexico.They have been successfully adapted to cold climates,with the most important modification being to power the tracker motor directly off the PV system's storage battery rather than its own dedicated battery pack.Watt-Sun trackers sized for BP Solar modules are available in 4-,6-,8-,12-,and 18-panel configurations. The advantages of dual-axis tracking when compared with a fixed-tilt panel mount in Alaska are evident if one compares plane-of-array insolation for the two options using the Fairbanks SOLMET data base.This has been done in Reference 6,and these plots are reproduced in Appendix A. Cost,weight,and cycle-life data for the system's flooded lead-acid storage battery are based on the Pacific Chloride brand manufactured by GNB Battery Technologies of Lombard,Illinois.They are commercially available in cell sizes ranging in capacity from 525 to 1690 ampere-hours (Ah).Yuasa Exide ot Horsham,Pennsylvania,also makes a high-quality,flooded lead-acid battery for deep-cycle applications,ranging in capacity from 500 to 1750 Ah.As mentioned previously,Exide batteries have greater cycle life than Pacific Chloride,but they appear to be available only as pre-assembled batteries,which are impossible to move without a forklift.Pacific Chloride batteries are available as individual 2-volt cells,which makes them much easier to handle in a remote location. il Northern Lights generators,manufactured by Alaska Diesel Electric of Seattle,Washington,were selected for the nano-grid system.Although more expensive than Honda or Onan generators of comparable size,they have a proven track record of more than 30 years in the Alaskan bush.They utilize heavy-duty,water-cooled Lugger diesel engines that can run 20,000 to 25,000 hours before their first major overhaul.Cost and weight data for this study are based on a 5 kW model with a dry sump for extended operation between oil changes.This unit has a full-load fuel consumption of 0.51 GPH. A Honda 1800-watt gasoline-powered generator was selected for the individual household alternative,since this is the most widely used personal generator in Lime Village.When properly maintained,it is expected to have a service life of 5 years.The Honda 1800 has a full-load fuel consumption of 0.32 GPH. Trace Engineering,also of Seattle.has the deservedly best reputation for sine wave and modified sine-wave inverters for residential PV systems.As mentioned previously,these inverters also have a rectifier circuit for battery charging by the AC generator.A 4 kW model was selected for the nano-grid system,while a 1.5 kW model!was selected for the individual household system. The nano-grids would be operated.maintained,and administered in much the same way as a centralized diesel system.The customer would simply be billed based on monthly meter readings, and the power system itself would be "transparent"to the residential customer.Thus nano-grids would be quite unlike individual household PV systems,where residents must periodically check that the system is operating properly and would be responsible for adjusting the charge controller as necessary. A tremendous advantage of nano-grid systems is that monitoring and control can be accomplished remotely,by telephone link,using the Infinity-6 charge controller manufactured by Bobier Electronics of Parkersburg,West Virginia.This is also a fully functional load center,with all the safety features required by the National Electric Code,packaged together with a digital metering and control microprocessor. In addition,the Infinity-6 contains a solid-state data logger that can record voltage and current input from four different locations:PV array,generator,battery,and inverter.This will enable"real-world"validation of the computer simulation,leading to better designed and more economical systems with each generation. The Infinity-6 is sufficiently costly that it would be uneconomical for individual household systems. Instead,these would used charge controllers and load centers with digital metering,manufactured by Ananda Power Technologies of Nevada City,California. Pricing for all of the above components was supplied by Alternative Energy Engineering of Redway, California.Shipping costs were also included based on AEE shipping everything except the trackers and batteries (which would be drop-shipped from the manufacturers)to Seattle,where all components would be containerized and shipped via common carrier to Anchorage.They would then be air-freighted into Lime Village. 12 Trade-Off Results Nano-grids were sized from one to six households,searching first tor the optimal number of PV panels and then for the optimal battery capacity.These trade-otf results are plotted in Figure 8. The darkened symbols in the plots indicated the final choice for each household number.Note that for the 5-and 6-household systems,the final choice is considerably removed from the lowest-cost point;this will be explained shortly. The annual cost of the plots'vertical axis consists of two parts: *an annual capital charge,assuming that the capital cost of the previously described components (including shipping)was financed through a 20-year loan at a 10% nominal interest rate *an annual fuel charge,based on total generator run time,its full-load utilization rate .(any surplus energy not used for battery charging or household loads was assumed to be dumped into a resistive water heater for keeping the battery warm) So that the Northern Lights generators will last the entire loan period without requiring a major overhaul,run time would be limited to less than 1,000 hours per year.If each nano-grid utility building is supplied by an exterior 500-gallon fuel tank,re-tueling would only have to take place once a year,and the nano-grid system could realize the economy of bulk fuel purchases.Therefore, the price of fuel is assumed to be $3.00/gal,slightly more than paid by the School District,but considerably less than the $4.00/gal paid by individual households. As the number of PV panels in a nano-grid system increases,the generator runs less often,and the total annual cost drops.At some point,however,the capital charge for additional panels costs more than the fuel savings,and the total annual cost rises.The lowest-cost point shifts to the right as the number of households connected to the nano-grid increases.Thus the optimal number of panels is 6 for one household,12 for two households,and 18 for three or more households. Likewise,cycling the generator's output through an inverter/battery system means that the generator does not have to be run continuously to meet even light loads.and the tuel savings more than offset the capital cost of the battery.At some point,however,the capital charge for additional battery capacity costs more than the fuel saved,and the total annual cost rises.As with PV panels,the lowest-cost point shifts to the right as the number of households connected to the nano-grid increases.Optimal battery capacity is 1270 Ah for one household,1482 Ah for two,three,or four households,and 1690 Ah for tive or six households. As previously mentioned,the final battery capacity and number of PV panels chosen for the 5-and 6-household nano-grids is far to the right of the lowest-cost points.The reason for this is shown in Figure 9,which indicates the effect of adding additional battery capacity and PV panels as a nano-grid grows from one to six households. For a 4-household system,a 1482-Ah battery cycles so frequently that it would have to be replaced before the end of 20-year loan life.With a 5-household system,a 2540-Ah battery will last longer than 20 years,but a total of 24 PV panels are required if the generator is also to last 20 years before needing a major overhaul.The 6-household system requires both additional PV panels and additional battery capacity before total generator run time is reduced to an acceptable level. 13 As the number of households connected to a nano-grid increases from 1 to 3,the beneficial effect of sharing capital and fuel costs among a greater number of households more than offsets the system's increased capital and fuel charges necessary to accommodate the additional load.As the nano-grid grows beyond 3 or 4 households,this net benefit continues but is not as great. Also note that the 5-and 6-household systems do not have any generator run-time margin to accommodate four hours of 100-watt TV watching added to the basic residential load profile. Increasing the diesel generator capacity to 8 kW and stacking two 4 kW Trace inverters would provide this margin,but the additional capital charge greatly outweighs the fuel savings.Therefore, we conclude that for the weather conditions and residential load profiles of Lime Village,the optimal nano-grid size is 3 or 4 households. Lay-Out of Optimal Village Systems At 120 volts,nano-grid power can be transmitted over distances of hundreds of feet using relatively low-cost wire,which must be adequate to handle a winter evening peak household load of 480 watts (4 amps at 120 VAC).To keep transmission losses less than 2%,the maximum transmission distance is 275 ft for #10 wire,450 ft for #8 wire,and 725 ft for #6 wire. With this in mind,six nano-grids were laid out for Lime Village,and these are mapped in Figures 10 through 12.Transmission cable routes were selected to minimize the requirement for right-of- way easements across private property.Transmission distances were scaled from aerial photographs. For the two remote upriver systems (Al and A2),actual cable routes probably will be shorter than the right-angle distances shown on the map,but the map distances were used in order to be conservative when estimating the cost and shipping weight of transmission cables. 14 KINKO'S ALEXANDRIA 1D:703-739-0785 JAN 19°95 20:15 No.042 P.02 ECONOMIC COMPARISON OF THREE ALTERNATIVES Nano-Grid System Capital Cost PVGENBAT results for the optimized residential nano-grids arc given in Appendix B.Monthly total energy flows are listed for the PV array,generator,and battery along with monthly number of battery cycles,generator starts,and generator run-hours. Nano-grid capital costs are itemized in Table 1.Note that the two local villagers who will beresponsibleformonthlymaintenanceshouldbepartoftheon-site installation Jabor team for at Jcast one of the nano-grids. Individual Household System Capital Cost PVGENBAT results for the optimized individual household system are given in Appendix C,and the capital cost breakdown is given in Table 2.As with the nano-grid system,local villagers who will be responsible for monthly maintenance should be part of the on-sitc installation labor team for at least two of the household systems. Unlike the nano-grids,which can be monitorcd and adjusted remotely,the individual household systems will require on-site monitoring and periodic adjustment of the charge controller.Therefore the two villagers who will be responsible for monthly maintenance will cach require 10 hours of additional training,which is not necessary with the nano-grid system. Central Diesel System Capital Cost Capital costs for the central diesel system were taken directly from the 1992 report.by the formerAlaskaEnergyAuthority(Reference 3),and these arc itemized in Table 3.The only modification to the data from that report was reducing the AC service entrance cost from $1,000 to $200,based on vendor information gathered for the nano-grid system. It should be noted that Refcrence 3 contains no documentation of the capital costs beyond what is presented in Table 3.In particular,it is unknown whcther the "Enginccring and construction" cost includes program management and training.Likewise,it is unknown whether "Tool and equipment purchase"includes spares. The generator module is too large for a Sky Van to carry and could not be flown into Lime Village as suggested in Reference 3;rather it would have to be flown into Sparrevohn Air Force Station aboard a Icased Hercules C-131 and sledded to the village.The Stony River is too shallow for the module to be barged in. It was beyond the scope of this study to re-design the central dicscl]system.Given the lack of supporting documentation in Refcrence 3,these capital cost estimates are much less certain than those for the other two alternatives._ 1§ KINKO'S ALEXANDRIA ID:703-7393-0785 JAN 19°95 Life-Cycle Cost Comparison The annual cost for any of the energy supply altcrnatives consists of three components:a capital charge,a fuel charge,and an operation,maintenance,and administrative charge.Each of these is explained below. The capital charge assumes that purchase,shipping,and installation of the systems is financedthrougha20-year loan at a 10%nominal interest rate.While the individual household systems aredesignedonlyforresidentialdemand.the othcr two alternatives powcr other loads,and the capitalchargeforeachresidenceisbasedonresidentialpeakloadrclativetothesystem-wide peak. As shown in Figure 12,one of the nano-grids (System C)powers the village office,medical clinic, and church,as well as two homes.The combined peak load of these community buildings,including heater ignition in the office and clinic (300 watts each),is 1275 watts.The winter peak load for a residence occurs during the dinner hour (sce Figure 7),and is 580 watts,assuming that a TV is also on at this time.'The total peak residential demand for 20 homes is thus 11.6 kW.The system-wide peak load is 12.875 kW,and the residential share is 11.6/12.875,or 90%. The residential share of the central diesel capital charge was calculatcd as follows.The school peak demand was assumed to be 12 kW for six months out of the ycar,and 0 kW for three summer months.Unicom's peak load was assumcd to be 7.5 kW for ninc months out of the ycar (since the heater might be used an occasional day in spring and fall),and 6 kW during the summer months. Residential peak load was assumed to be 11.6 kW for nine months out of the year,and 8.4 kW during the three summer months.The residential share of the system-wide pcak is 37%for nine months and 58%for three months.The annual weighted average is thus 43%. Fuel costs for each of the PV hybrid options were derived from the annual total run time of the generator (see Appendices B and C)and its fuel efficiency based on full-load consumption rate. Two estimatcs were made for these systcms:one for the basic load profiles of Figure 7 and one for an added 400 Wh/day associated with TV usage. For the Northern Lights nano-grid generator,fucl efficiency was calculated as 5 kW +0.51 GPH, or 9.8 kWh/gal.For the Honda individual household generator,fucl cfficiency was calculated as 1.8 kW +0.32 GPH.or 5.6 kWh/gal.For the central diesel system,fuel efficiency was assumed to be the average of those reported for the village utilities of the Mid-Kuskokwim Electric Cooperative (MKEC),which ranged from 5.5 to 7.6 kWh/gal in 1988 (Reference 10).According to Reference 11,the average MKEC residential customer consumed 2,882 kWh in 1992 (approximately 240 kWh per month)and it was assumed that household cnergy demand in Lime Village would grow to this level once a central dicscl system was in place.Note that this is nearly three times the annual avcrage demand represcnted by the basic load profiles of Figure 7. Opcration,maintcnance,and administrative costs (OM&A)for the nano-grid were calculated as follows.The generators arc assumed to last at least 20 ycars before rcquiring overhaul,so the only niaterials cost is for consumable items such as filters,anti-freczc,and lube oil.InverTech Alaska would be contracted to perform off-site monitoring and control via telephone connection to the Infinity-6.Connection time is expected to total 12 hours per month (20-30 minutes per week pernano-grid).Two villagers would be contracted for on-site maintenance,such as replacing water in the batterics and changing gencrator oil,and this is expected to requirc an hour per week for each nano-grid.Administration is expected to take a total of 30 hours per month.|ft[ar ebook 16 20:15 No.042 P.03 KINKQ'S ALEXANDRIA ID:703-739-0785 JAN 19°95 20:16 No.042 P.04 Although the office,clinic,and church have a significant share of the nano-grid system's peak powerdemand,their annual energy consumption is relatively insignificant:about 3%of system-wide annual energy,Therefore 97%of the OM&A charge is applicd to residential customers. OM&A costs for the individual household systems were calculated as follows.The generators were assumed to last 5 ycars and would require $1,000 to replace,or $200 per year of service life.The houschold systems must he inspected and maintained if they arc ta work properly for 20 years.As with the nano-grid this will be donc primarily by two local villagers.who are expected to spend an average of 30 minutes per weck in each household.They are also expectcd to spend 10 hours per month in consultation over the telephone with InverTech Alaska.InverTech Alaska also will make two trips per year 10 Lime Village,to accompany the villagers on one of their weckly inspection rounds and provide on-site troubleshooting. Unlike the other two options,individual houschold systems would not be metered or billed for the amount of clectricity they used.Residents would pay a flat monthly fee to support maintenance personnel,and 140 hours per ycar would be required to collect these fecs,pay personnel,and keep records.Residents would be responsible for buying their own generator fuel and lube oil. For the central dicscl system,generator overhaul/replaccment,consumablcs,and on-site maintenance labor costs were taken directly from Reference 3.Administrative duties are expected to take 40 hours per month.This is 10 hours per month more than the nano-grid system,to account for the overhcad associated with annual generator overhaul/rcplacement.The residential share of central dicsel system OM&A costs is based on the distribution of total annual energy usage as follows:12,640 kWh/yr by the school and teacher's quarters;39,000 kWh/yr by Unicom;and and 2,882 kWh/yr by cach residential household. The total annual charge per household for each of the three energy supply altcrnatives is plotted in Figure 13.These are itemized in pic charts,where the area of cach pie is directly proportional to the total annual charge.For the hybrid PV options,fuel charges are based on the average between the basic load profiles and the added 400 Wh/day profilcs. If capital charges arc billed to residential customers,then per household,the nano-grid option is roughly $300/yr less costly than the central diesel option and $900/yr Iess costly than the individual household option.If capital costs are paid by a grant or State appropriation,then running costs (fuel plus OM&A)are as follows:$1,282/yr per household for the nano-grid system;$1,936/yr per houschold for individual systems;and $2,037/yr per houschold for the central diesel system. With all three alternatives,more than half the OM&A costs are paid to villagcrs,as well as a small portion of the annual capital charge (installation labor).For the PV hybrid options,25-26%of thetotalannualpaymentstaysinthevillage,whereas for the central diesel system,only 21%stays in. If capital charges arc excluded,then the differences become much greater,with 44%of nano-grid running payments staying in the village,40%of individual system running payments staying in,and only 25%of central diescl running payments staying in. 17 Table 1 NANO-GRID HYBRID PV SYSTEM CAPITAL COST BREAKDOWN UNIT NO.OF TOTAL COMPONENT DESCRIPTION COST (3)UNITS COST ($) Diesei generator,120 VAC,5 kW 6,340 6 38,040 Inverter and charge controller,4 kW 3,197 6 19,182 18-panei PV array on dual-axis tracker,1.35 kW.9,118 6 54,708 1482 Ah flooded lead-acid battery,24 VDC 4,486 3 13,458 2110 Ah flooded lead-acid battery,24 VDC 6,955 3 20,865 Pre-fabricated utility building,8'x 16'floor area 6,500 6 39,000 Foundation and outfitting of utility building 600 6 3,600 Fuel tank,500 gal,with stand 900 6 5,400 PV array and utility building hook-up wire 165 6 990 Direct-burial AC service cable,3-conductor,#6 1.31/ft 1,500 ft 1,965 Direct-burial AC service cable,3-conductor,#8 0.82/ft 500 ft 410 Direct-burial AC service cable,3-conductor,#10 0.49/ft 4,500 ft 2,205 AC service entrance (mains panel,kWh meter)200 20 4,000 Spares (5 water pumps and 5 fan belts for diesel 4,175 generators,1 inverter,and 1 charge controller) Shipping (vendors to Seattle as required,containers from Seattle to 28,500 Anchorage as required,air freight from Anchorage to Lime Village) TOTAL EQUIPMENT-RELATED COST 236,498 Project management (20 hrs per system)60/hr 120 hrs 7,200 On-site field engineering (20 hrs per system)40/hr 120 hrs 4,800 On-site installation labor (100 hrs per system)20/hr 600 hrs 12,000 Field engineer air travel (1 system per trip)440/trip 6 trips 2,640 Field engineer food and lodging in Lime Village 40/day 20 days 800 (5 days first trip,3 days per later trip) TOTAL LABOR-RELATED COST 27,440 PROJECT CONTINGENCY (10%)26,394 TOTAL PROJECT COST 290,332 _17 Table 2 INDIVIDUAL HOUSEHOLD HYBRID PV SYSTEM CAPITAL COST BREAKDOWN UNIT NO.OF TOTAL COMPONENT DESCRIPTION COST ($)UNITS COST ($) Gasoline generator,120 VAC,1.8 kW 1,000 20 20,000 Inverter and charge controller.1.5 kW 1,708 20 34,160 8-panel PV array on dual-axis tracker,0.60 kW,4,535 20 90,700 1055 Ah flooded lead-acid battery,12 VDC 3,478 20 69,560 Battery safety enclosure 200 20 4,000 PV array hook-up wire '45 20 900 Spares (3 inverters,3 charge controllers)5,124 Shipping (vendors to Seattle as required,containers from Seattle to 30,908 Anchorage as required,air freight from Anchorage to Lime Village) TOTAL EQUIPMENT-RELATED COST 255,352 Project management (10 hrs per system)60/hr 200 hrs 12,000 On-site field engineering (10 hrs per system)40/hr 200 hrs 8,000 On-site installation labor (40 hrs per system)20/hr 800 hrs 16,000 Training by field engineer (20 hrs per trainee)40/hr 40 hrs 1,600 Training of two villagers (20 hrs per trainee)20/hr 40 hrs 800 Field engineer air travel (4 systems per trip)440/trip 5 trips 2,200 Field engineer food and lodging in Lime Village 40/day 27 days 1,080 (7 days first trip,5 days per later trip) TOTAL LABOR-RELATED COST 41,680 PROJECT CONTINGENCY (10%)29,703 TOTAL PROJECT COST 326,735 18 CENTRALIZED DIESEL SYSTEM CAPITAL COST BREAKDOWN Table 3 UNIT NO.OF TOTAL COMPONENT DESCRIPTION COST ($)UNITS COST (3) Diesel generators,20 kW and 40 kW,100,000 1 100,000 in 9'x9'x40'module with paralleling switchgear and fire suppression Fuel tank with secondary containment,5000 gal 15,000 1 15,000 Fuel piping 800 1 800 Generator step-up transformer,75 kVA 2,000 1 2,000 Service transformers,10 kVA 500 12 6,000 Utility poles,40/5 410 15 6,150 Cross-arms,insulators,hardware 6,500 1 6,500 Wire,primary and secondary 2,500 1 2,500 AC service entrance (mains panel,kWh meter)200 20 4,000 Shipping 28,800 TOTAL EQUIPMENT-RELATED COST 171,750 Tool and equipment purchase 6,000 Engineering and construction 99,320 On-site installation 20/hr 1,200 hrs 24,000 Travel and per diem 14,000 TOTAL LABOR-RELATED COST 143,320 PROJECT CONTINGENCY (10%)31,507 TOTAL PROJECT COST 346,577 19 Table 4 LIFE-CYCLE COST COMPARISON OF THREE ENERGY SUPPLY OPTIONS ANNUAL COST COMPONENT NANO-GRID INDIVIDUAL CENTRAL Capital Charge Project capital cost $290,332 $326,375 $346,577/yr Village capital charge (20-yr loan at 10%)$24,840/yr $27,924/yr $29,652/yr Residential share (peak load basis)90%100%43% Charge per household $1,118/yr $1,396/yr $638/yr Fuei Charge Energy supplied by AC generator 18,440 kWh/yr |12,780 kWh/yr |57,640 kWh/yr(basic residential load profile) Energy supplied by AC generator (add 400 Wh/day per household) 21,820 kWh/yr 15,880 kWh/yr Fuel consumption rate 9.8 kWh/gal 5.6 kWh/gal 6.8 kWh/gal Fuel unit cost $3.00/gal $4.00/gal $2.50/gal Charge per household (basic load profile)$282/yr $456/yr $1,060/yr Charge per household (add 400 Wh/day)$334/yr $567/yr . Operation,Maintenance,and Administration Charge Generator overhaul/replacement -0-$4,000/yr $13,682/yr Consumables (filters,lube oil,etc.)$1,260/yr $300/yr $2,328/yr Engineer remote troubleshooting ($40/hr)$6,240/yr $4,800/yr -0- Engineer on-site troubleshooting (2 trips;-0-$2,640/yr -0- $520 travel and 20 hrs @$40/hr per trip) Villager on-site maintenance ($20/hr)$6,240/yr $13,200/yr $12,000/yr Paying personnel,record-keeping ($15/hr)$2,100/yr $2,100/yr $3,000/yr Billing,collection,ordering fuel ($15/hr)$3,300/yr -0-$4,200/yr Residential share (annual energy basis)97%100%53% Charge per household $928/yr $1,352/yr $933/yr TOTAL CHARGE PER HOUSEHOLD _ Basic residential load profile $2,328/yr $3,204/yr $2,631/yr Add 400 Wh/day per household $2,380/yr $3,315/yr " 20 KINKO'S ALEXANDRIA ID:703-759-0785 NANO=-Q@RIO PV HYBRID ($2.384/yr per hovsehold) $1,072 Capital MONEY FLOW308FuelOUTOF 364 OM&A VILLAGE 564 OMBA MONEY STAYING 46 Capital IN VILLAGE {INDIVIDUAL PV HYBRID ($3,260/yr per househoid) $1,324 Capital MONEY FLOW512FuelOUTOF 587 OM&A VILLAGE 765 OM&A MONEY STAYING 72 Capital IN VILLAGE CENTRAL DIESEL ($2,631/yr per household) $594 Capital MONEY FLOW1,060 Fuel OUT OF 424 OM&A VILLAGE STAYING 44 Capital IN VILLAGE JAN 13°95 20:17 No.042 P.O6 Figure 33 Capital (OUT) 46% Fue!(OUT)§4 Capital (iN) 13%2% ONM8BA (OUT)pe OM&A (IN) 15%24% Capital (OUT) 41% Fuel (OUT)My TU YY YY A AGLI"4 a4 A,16%MO anc Capital (IN) :2% OMBA (IN) 23% Capital (QUT) Fuel (OUT)23% 40% g Vey Yes oAOWIEIEA Canital (IN)Vip ))2%a aiteet OM&A (IN)eeSea 19% SIR SPEEDY #7372 TEL No.6841671 Jan 20,95 17:56 No.013 P.C2 CONCLUSIONS AND RECOMMENDATIONS Conclusions Of the three encrgy supply altcrnatives,che nano-grid system is the most economical from several polots of view. *Ithas the lowest total project capital cost (although it would be more expensive than the central dicscl system if additional nano-grids were built for a washeteria,the air strip,the schcol,and Unicom). *Assuming that residentia!cussomcrs pay ior their share of the capital cost,the nano- grld sysiem has the lowest total annual charge per household,saving $3(X)/yT relative to the central dicsel systern and $900/yr relative to individual PV hybrid systems. *Ifresidential customers do not have to pay capital charges,then the annual charge per houschold for running the nano-grid system would be $800/yr less than running the central diesel system and $700/yr less than running individual PV hybrid systems. *Nearly halfof the residential payments tor running the nano-grid system would stay in the village;the net Row of moncy out of the village amounts to about $720/yr per houschold,which is less than what many Lime villagers now pay to run ¢heir own personal ecncratols. The poor cconomy of individual hybrid PV systems is primarily duc to the smaller size of the gencrators,charge controllers,and invertcts (which cost more per Kilowatt),the much poorer fucl ¢cficieney of the small Honda gencrators relative 10 the Nozthern Lights diesc]sct,and lack of remote monitoring capability,which increases the cost of start-up training and annual mialnuenance. Individual hybrid PV systems also have the disadvantage of introducing baticrics inta the home (since they must be kept warm).An cnelosure is provided to eliminate the risk of clectric shock and acid burns.Nevertheless,space has to be found for such an enclosure,where ib would be accessible to visiting maintenance personnel.The mobility of the villagers in pursuit of their subsistence activities may make it difficult to schedule regular inspection visits,which would not be. a problem for the nano-grid or central dicael alternatives. One disadvantage of the central dicscl system is that the gencrator runs continuously and its fuel efficiency is very poor when the system ts Lightly loaded,duc to the fuct required simply to Idle the engine.Thus at night or in the summer,when school is out and days are much Jonger,thegencratormaybeoperatingatlessthanaquarterloadformuchofthetime.This is why theaveragefuclcfficiencyofthcMKECvillagesismuchlessthanthe10kWh/gal expected for a generator always operating at full load (such as the Northern Lights 5 kW unit). The poor coonomy of the central diesel system is largely due te the tripling of residential cncrgyconsumptionfromanannualaverageof81kWhémonthassociatedwiththebasicloadprofilcsofFigure7,to 240 kWh/month in the MKEC villages with central dlcscl systems,Because a centraldieselgencratorconsumesmorefuelperkWhwhenIightlyloadedthanitdocswhenfullyloaded,there is no incentive for energy conservation.In fact,with a lightly loaded generator,growth inelectricityconsumptionisaccompaniedbyadisproportionatclysmalicrgrowthinfaelconsumption, and ihe cost of energy actually decreases.Thus the mechanics and cconomics of a central dicacl system combine so as to encourage wasicful cncrgy usc. 22 STR SPEEDY #P3r2_TEL No.684167t Jan 20,95 17:56 No.013 P.03 Since the nano-grid will be as "lransparcnt”to the avcrage user as a central diesel system,there isthedangerthatresidentialelectricityconsumptionwillgrowbeyondtheloadprofilesusedinthis study.Unlike a central dicsel generator,however,the fucting of nano-grid generators will be much more sensitive to energy demand.In fact,due to inefficiencies in the battery/invertcr cycle, increascd demand in a nano-grid actually increases fucl consumption by more than a 1:1 ratio. For cxample,adding 400 Wh/day of TV usage to the basic load profiles of Figure 7 would amount m)an additional 146 kWh/vr per household,with a total increase of 2,290 KWh/yr for the entirevillage.'Fo meet this increase in dumand,total gencrator production in the village would inercase by 3,380 kWh (compare in Table 4);roughly a third of the gencrator's energy is lost in battery/inverter cycling.Ata production fuel cfficiency of 9.8 kWh/gal.the consumption fucl ctieiency tor this added demand would be 6.6 kWhygal. Note,however,that consumption fuel efficiency for the basic residential load profiles ix much better. At 6)kWh/month,annual demand pcr household is 972 kWh,or 20,031 kWhfyr for the entire village,Including 591 kWh/yr tor the office,clinic,and church.The cnergy produced by all of thenano-grid gencrators in the village totals 18.440 kWhyyr.Ar a production fucl ctticiency of 6.8xWh/eal,the consumption fuel efficiency for the base case is 10.6 kWh/gal.Thus PV generationnotonlyoftsctsthegenerator's hattcry/inverter cycling losses,but actually provides a net gain to the 3ystem.This suggests that a two-ticred billing structure might be appropriate,with a fucl charge -f 28e/kWh ($3.00/gal +10.6 kWh/gal)for houschold monthly usage up to 80 kWh/month,and4Se/kWh (§3.00/gal +6.6 kWh/pai)for all monthly cnergy consumpion beyond that level.Such a rate structurc would encourage conservation,which is necessary if a 20-year service life is to be realized for the generators and battcrics. This study concludes that the optimal nano-grid size is 3 to 4 houschoids.As shown in Figure 8,however,up to 6 households can bs accommodated with additional solar pancls and batterycapacity.Note that the optimal 6-houschold nano-grid can be split into two optimal 3-householdsystems,simply by moving half the battcry capacity to a new utility building,re-routing the output from one of the 18-pancl trackers to this building,and installing a ncw generator and charge controller.in this way,nano-grids can keep up with future village growth. Recommendations li Lime Village elects the residential nano-grid system as their preferred alicrnative,several issucsmustberesolvedbeforefinaldesignandconstruction.Fina!AC scrvice cable routes should be chosen and any requifed casements obtained.Plans should also be made for providing intcrna!house wiring where necessary,and for building or buying super-cfMficient refrigeratorArcezers. The village's decision regarding rclocation of the water supply must be made before a washeteria nano-gric can be designed,particularly since building insulation and weathes-tightness will influencetheelectricalloadsassociatedwithspaceandwaterhcaumg.An associatcd issue is whether the washeteria nano-grid should also include the air strip and maintenance shed. Once the residential nano-grids have operated successfully for a year,scrious consideration shouldbe:given to designing a system for the school and teacher's home.As alrcady mentioned,theschool's cnergy demand for heating and lighting will probably be reduccd as students do morc oftheirschoolworkathome.Efficiency improvements should be made throughout the schoal compicx. 23 SIR SPEEDY #73572 TEL No.8341672 Jan 20,95 17:56 No.O15 P.04 Likcwisc,a nano-grid could be designed for the Unicom utility.As mentioned before,this should be a 48 VDC system and should consider waste heat rccovery from the diescl generator to heatVnicom's building in winte:,eliminating their 1.5 kW space heater. Jn developing the final nano-grid designs,the PYVGENBAT program should be modified tu include on algorithm for partial loading of the generator.For this study it was assumed that any surplus AC generation would be dumped into a t¢sistive heating clement for warming the battcrics.It mayve,however,that waste heat recovery from the gencrator would be adcquate for this job,in which case the generator would bc rary loaded some of the timc. Another desirable program cnhancement would be to modcl GNB''s ABSOLYTE scaicd lead-acid dartcries,Which use 4 starved-electrolyte gel (Refercnce 12).Even with wasic heat recovery,there is always the danger of a flooded lead-acid battery freezing,particularly at night following a deep discharge,when electrolyte concentration is most dilutc.Expansian of the freezing electrolyte canrupturethecellcontainer.causing it to spill ance the battery thaws.CNB tests show that an 4BSOLYTE batlery that has been abusively "frozen"(water crystals forming in the electrolyte gel) can be recharged from a decp discharge condition with the battcry maintaincd at -25°F.Tesis data ziso indicate that an ABSOLYTE baccery detivers 20-40%of Its room temperature capacity at operating temperatures as low as -40°F,which is far superior to flooded lead-acid batteries,making ABSOLYTE technology a viable alternative to the costly nickclcacmium batterics that are often used in extremely cold environments. Finally,it is recommended that a pilot nano-grid be installed and operated for at lcast one year hetore the full nano-grid system is implemented.This pilot nano-grid should be System C,which would power two residences,the village office,the medical clinic,and the church. Figure 1 wpe thee 186°164°183° )a SyeeLae83° X\% aA °o %* AYES 2.3 . 2 REVELATION j-S2°Stony Rivervillage Red Devil Sleetmute SCALE 1:2,000,000 Nondaltonj=60°1 Inch equals 22 miles approx @ Sparrevohn A.F.S. ; Figure 1.Lime Village:the local and regional area -8- BATTERYLIFE(numberofcycles)Figure 2 FLOODED LEAD-ACID,DEEP-CYCLE BATTERY CHARACTERISTICS 5000 T T T & 40008 N aN NX 3000 N '\Exide NN N '9 N . ". \.'o. "'NXN N 2000 'OX |.Pacific \' \ Chloride ..a2 AN \ ' ' 'N 'ob 1000 ::4 20 35 50 65 80 CYCLE DEPTH (%)BATTERYVOLTAGE32 30 28 26 24 22 CHARGING 20 0.20 0.40 0.60 0.80 1.00 NORMALIZED STATE OF CHARGE CELLVOLTAGEANDNORMALIZEDSOC3.00 r 2.50 P 2.00 } 1.50 100 | 0.50 0.00 Figure 3 C/10 DISCHARGE RATE,NO GASSING OR HEAT LOSSES Constant (C/10) CHARGE ------2-stage (C/10,C/20)REGIME: -----_3-stage (C/5,C/10,C/20) qT T a T Ml j 3.00 [ul v ee | 78°F :1 1 QO 4 CELL VOLTAGE 1 je}4 . 7 2.50 4 0 I } i 1 4 N 4 4 2.00 r 7 1 9 1.507 : 4 < 4 NORMALIZED STATE OF CHARGE r NORMALIZED STATE OF CHARGE 4 <1.00 4 |}8 4 i 0.50 |4 +4 1 es 0.00 re L i AL 6 12 18 24 re)6 12 18 24 TIME (hours)TIME (hours) Figure 4 120%T T T T T 100%" 80%fF " 60%F-- ema Diesel load 40%+\- ee ese Charge efficiency \a(R)10020%F-.\+ O%il ]I i {\ 0 0.2 0.4 06 08 1.0 1.2 X;=Battery state of charge CELLVOLTAGEANDNORMALIZEDSOC3.00 [ 2.50 r 2.00 1.50 r 100} 0.50 0.00 Figure 5 C/10 DISCHARGE RATE,WITH GASSING &HEAT LOSSES Constant (C/10) CHARGE REGIME:-----2-stage (C/10,C/20) ------3-stage (C/5,C/10,C/20) CELL VOLTAGE 2.50 eeeSeoeSeenOeeeeeee2.00 1.50 7 NORMALIZED STATE OF CHARGE NORMALIZED STATE OF CHARGE 1.00 0.50 CELLVOLTAGEANDNORMALIZEDSOCTIME (hours)TIME (hours) 24 CELLVOLTAGEANDNORMALIZEDSOC3.00 [ 2.50 r 2.00 r 150 100 | 0.50 0.00 Figure 6 C/40 DISCHARGE RATE,WITH GASSING &HEAT LOSSES Constant (C/10) CHARGE ------2-stage (C/10,C/20)REGIME:9 "--- 3-stage (C/5,C/10,C/20) CELL VOLTAGE NORMALIZED STATE OF CHARGE 2.50 2.00 1.50 NORMALIZED STATE OF CHARGE 1.00 0.50 CELLVOLTAGEANDNORMALIZEDSOC4s 0.00 puny an an Gare i rm 1 24 36 48 ie)12 24 36 48 TIME (hours)TIME (hours) LOAD(watts)LOAD(watts)LOAD(watts)Figure 7 USE VARIES WITH SEASON USE PATTERN CONSTANT Freezer compressor Kitchen appliances ESS Bedroom lighting [_]Radio WM Main room lighting May,Jun,Jul,Aug:2.24 kWh/day 8 10 12 14 16 18 20 22 24 Sep.Oct,Mar,Apr:2.56 kWh/day Nov,Dec,Jan,Feb:3.20 kWh/day 8 10 12 14 16 18 20 22 24 HOUR (24 =11:00PM to midnight) ANNUALCOST($/yr)6000 5000 4000 3000 2000 Figure 8 NUMBER OF HOUSEHOLDS CONNECTED TO SYSTEM o 4 o 2 A 3 o 4 Vv #5 9 6 +r --6000 T ey ]rf 360 \ re) 2964 L 'o oO q_-O0-®24 7 O-0 9-e7ro9-0o-a-9 5000 i \2540 9 \yVO-_- a Vv II 4 >18 ©wy'a on?4 Coe a \ -et 4000 +°4090-94?2110 be '99-06-00 4 O A18a A &1482 1 O a4 asAad,]7 aa}1 5 1482 4 a4 -4 1 5 3000 q 0oOZon"4 Oo O 1270 |$12 eoa|< 6 | -oanLOt45lon-q-2.-O|0-@-0 |=g Pe-0 J r Battery 1 2000 r | capacity J ['(Ah) d No.of PV panels i re Pas cereee L 1000 ro meet L L re 10 20 30 40 (0)1000 2000 3000 4000 NUMBER OF PV PANELS BATTERY CAPACITY (Ah) Figure 9 >40 yrs rn rneeoe ee eeaeeee eeeea piesecard ” eat . EES kee eefuelchargeic3cCc< Es Annual capital charge eae RERCRRERS105 | Sos Sh || ™:eeSSS | Re t | oe pe aPL po bP pesadosartorsartire retard [e) wo oO w)oO [e) oO Oole) [e) Oo [e) [e) a 8 8 28828888 (SJA) Ball AYBLLIvea (44/S4u) AWIL NOYYOLVYSNAD (4A/$) GQIOHSSNOH Yad 1LSOD IWNANNV oe) 6 6 6 18 24 24 36 36 1NO.HOUSEHOLDS: 18 18 18 181812126NO.PV PANELS: BATTERY AH: Recideure planed SHEPHERDaoruuderconstruchorHE sa seeeeee AC gerute wire , (410 except wher.otherwise jnralicatted ) O Utility é wuld ag ee TT igen seme eS Hah x STONY Soo! [J Rick &SAMY Art &BaARBAPA RIVER 150° -#¢ STONY 600° NORA Acexice RIVE KR. SMITTY BeRBY S¥sTEemM AZ SANOK &Tia WILLIAMS to) 3/0 Sytrent Al OTangry serw ce uyre othe VISE ined icatecl ) [rvpert 7 boundenrles (#10 except where AC 42 KATHERINE Rosey Figure 11 WALT ER MOEN EIL B2SYSTEM Toss sss ( veaeeeceecuseeneees fore w> im Va |: 3: : te rn ot weno Qo 33 ha|: =0 vacecenseseseccetes : 7EEODan é Q . iA HRS) S on LO!g 5 ) w " | FRED &LISA cree”SN * ./>4,'. "on \/'S ',me t . '\/\Oe ,2.30 :WS . t. *' ' ., .ar .4 System C \ran eS PAULA'ws,On'\NX *,aN Bosgy ''"Aerie 4'ag!eo ' '-7 'a .ee ;r note !Y .\:; \ee '"Mey ' °,4 \VONGA awe Fi "ata .¢aa ':270',' \'7 a a rae :;' .&v aN .KW WAN,Vil FE /oe ''. ;ot fo:.M4ADRONE N ;7 .OFFICE \\<Y tos EMA L ; ''.220'./an 4 mK\AN av \NOW ' '¢/ .4 .Xs S :' ;LS ooxs bs Sst ' ¢cumpeo'5 ,-\|.ao ,' ;:.\\in wero TX./30 :"\''°'', mc '(thy 'Iso':']?:' ., : N oT \|ed Soy :'At :§ , ; ;¢1 |Oo systeat p(J MIKA *),ar \.'raCHVACHeg,270'\HC ;:re ,ost a oO tithe_eee Proper?houndanes z a'oe .ef Sie BGY Us ,300 ',oeececose AC service wire A LO LUTHER ao / putt ce me ' ,("10 aye )i "2 ,van KATHER PIE 'O Unity burldrns ZIaan3iyCo ee te S ALPENDIX A FAIRBANKS,AK TMY /SOLMET INSOLATION PREDICTIONS "AUG SEP OCT NOV DECJULJUN"MAR APR MAY"FEB 2+ 0 8 6 4 2 (AVG/,W/HM) NOLIYIOSNI TVNYON TVLOL JQNINIMOL sikrY-IvhA 169 JAN PLI/ELTFIXEDTILTINSOLATION(KWH/M"/DAY)FAIRBANKS,AK TMY /SOLMET INSOLATION PREDICTIONS JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC APPENDIX \s Number of PV panels:18 (1.35 kWp)5 kW GENERATOR NO.HOUSEHOLDS:2 C Battery amp-hrs:1482 (2-stage charging regime)aSystemcapitalcost:$25,550 ($6,340 for generator,$3,197 for PCU,$9,118 for PV panels,$4,486 for batteries,$2,409 for shipping) ANNUAL SUMMARY FOR DIFFERENT SPECIFIED CYCLE DEPTHS Spec.Avg.Battery Battery Battery PV PV PV PV Diesel Diesel Diesel Diesel No.of EFFICIENCY Annual Cycle Cycle Cycles Life kWh to kWh to kwh to kwh to Total kWh to kwh to kWh to Total Diesel Cost Depth Depth per yr (yrs)AC Load AC Load Battery Surplus kWh AC Load Battery Surplus Hours Starts Ext Int ($/yr) 20%20%160 24.5 1,995 867 1,016 0 1,884 457 3,155 3,233 1,369 150 63%57%4,281 30%29%119 27.5 2,021 876 1,008 0 1,884 426 2,862 2,177 1,093 108 70%60%3,858 40%39%97 27.6 2,156 885 999 0 1,884 290 2,823 1,806 984 89 73%63%3,692 50%48%76 29.1 2,143 890 994 0 1,884 297 2,590 1,433 864 70 77%=66%3,508 60%54%69 27.3 2,180 884 999 0 1,884 268 2,513 1,360 828 61 77%=67%3,453 70%66%58 26.1 2,217 881 1,003 fe)1,884 237 2,411 1,202 770 52 79%69%3,364 *80%7%49 24.7 2,185 890 993 0 1,884 257 2,293 1,030 716 45 81%71%3,281 #Indicates 100-watt TV load from 1900 to 2300 added to basic residential load. C Indicates that system also powers medical clinic and village office. Annual cost consists of capital charge (only for major components Listed above,and based on 10%nominal interest rate over 20-yr period) and fuel charge (based on consumption rate of 0.51 gal/hr and fuel price of $3.00 per gallon). MONTHLY SUMMARY FOR *SPECIFIED CYCLE DEPTH AC No.of Avg.Battery PV PV PV PV Diesel Diesel Diesel Diesel No.of Gal.of Load Battery Cycle kWh to kWh to kWh to kwh to Total kwh to kwh to kWh to Total Diesel Diesel Month (kWh)=Cycles Depth AC Load AC Load Battery Surplus kWh AC Load Battery Surplus Hours Starts Fuel Jan 299 7 81%251 12 10 0 23 52 362 147 V2 7 57 Feb 270 6 81%203 48 55 0 102 35 298 147 %6 6 49 Mar 259 2 82%170 102 130 0 232 6 93 61 32 2 16 Apr 251 3 52%138 126 165 0 292 4 51 25 16 1 8 May 239 1 10%125 132 152 0 284 0 0 0 0 0 0 Jun 232 0 0%122 127 148 0 275 0 ie]0 0 0 0 Jul 239 3 74%147 106 108 0 214 4 99 47 30 2 15 Aug 239 2 81%150 95 94 0 189 12 99 39 30 2 15 Sep 251 4 81%178 74 77 0 151 16 198 101 63 4 32 Oct 259 6 81%209 44 36 0 81 23 307 145 95 6 48 Nov 289 7 81%245 23 16 0 39 38 371 161 114 7 58 Dec 299 8 81%246 2 1 0 3 67 416 157 128 8 65 Number of PV panels: Battery amp-hrs: System capital cost: 18 1482 $25,550 (1.35 kWp) (2-stage charging regime);a($6,340 for generator,$3,197 for PCU,$9,118 for PV panels,$4,486 for batteries,$2,409 for shipping) 5 kW GENERATOR ANNUAL SUMMARY FOR DIFFERENT SPECIFIED CYCLE DEPTHS Spec.Avg.Battery Battery Battery PV PY PV Diesel Cycle Cycle Cycles Life kWh to kWh to kWh to kWh to Total kwh to Depth Depth =per yr (yrs)AC Load AC Load Battery Surplus kWh AC Load 20%20%192 20.4 2,326 864 1,019 0 1,884 445 30%30%127 25.3 2,239 889 994 ie]1,884 503 40%39%108 24.5 2,408 894 989 0 1,884 340 50%50%85 25.3 2,415 880 1,003 0 1,884 346 60%58%72 24.9 2,389 886 998 0 1,884 366 70%71%63 22.6 2,504 886 997 0 1,884 257 %*80%77%56 21.5 2,462 876 1,008 0 1,884 306 NO.HOUSEHOLDS:24C Diesel Diesel Diesel No.of EFFICIENCY Annual kWh to kWh to Total Diesel Cost Battery Surplus Hours Starts Ext Int ($/yr) 3,844 4,086 1,675 186 60%55%4,749 3,262 2,399 1,233 122 70%61%4,072 3,307 2,178 1,165 103 72%62%3,968 3,050 1,704 1,020 84 76%=65%3,747 2,850 1,520 947 69 Th =«60%3,635 2,884 1,489 926 63 77% =68%3,603 2,677 1,207 838 53 80%70%3,468 #Indicates 100-watt TV load from 1900 to 2300 added to basic residential load. C Indicates that system also powers medical clinic and village office.Annual cost consists of capital charge (only for major components Listed above,and based on 10%nominal interest rate over 20-yr period) and fuel charge (based on consumption rate of 0.51 gal/hr and fuel price of $3.00 per gallon). MONTHLY SUMMARY FOR *SPECIFIED CYCLE DEPTH AC No.of Avg.Battery PV PV PV PV Diesel Diesel Diesel Diesel No.of Gal.of Load Battery Cycle kWh to kWh to kWh to kWh to Total kWh to kWh to kwh to Total Diesel Diesel Month (kWh)=Cycles Depth AC Load AC Load Battery Surplus kWh AC Load Battery Surplus Hours Starts Fuel Jan 324 8 81%280 13 10 0 23 50 423 167 128 8 65 Feb 292 6 82%223 50 52 0 102 37 305 138 96 6 49 Mar 284 3 81%190 100 131 0 232 14 149 77 48 3 24 Apr 275 3 60%158 125 167 0 292 11 93 51 31 2 16 May 264 2 42%151 130 154 0 284 3 43 29 15 1 8 Jun 256 1 2h 147 127 148 0 275 0 0 0 0 0 0 Jul 264 2 81%172 102 V2 0 214 9 103 53 34 3 17 Aug 264 4 81%170 93 96 0 189 20 180 91 57 3 29 Sep 275 4 82%201 74 77 0 151 19 199 102 64 4 33 Oct 284 7 81%231 40 41 0 81 32 345 167 109 7 56 Nov 313 7 81%256 20 18 0 39 55 383 147 118 8 60 Dec 324 9 81%283 2 1 0 3 57 453 185 138 8 70 Number of PV panels:18 (1.35 kp)5 kW GENERATOR NO.HOUSEHOLDS:3 Battery amp-hrs:1482 (2-stage charging regime) ;aSystemcapitalcost:$25,550 ($6,340 for generator,$3,197 for PCU,$9,118 for PV panels,$4,486 for batteries,$2,409 for shipping) ANNUAL SUMMARY FOR DIFFERENT SPECIFIED CYCLE DEPTHS Spec.Avg.Battery Battery Battery PV PV PV PV Diesel Diesel Diesel Diesel No.of EFFICIENCY Annual Cycle Cycle Cycles Life kWh to kWh to kWh to kWh to Total kWh to kWh to kwh to Total Diesel Cost Depth Depth per yr (yrs)AC Load AC Load Battery Surplus kWh AC Load Battery Surplus Hours Starts Ext Int ($/yr) 20%20%159 24.7 2,010 693 1,191 0 1,884 403 3,050 3,187 1,328 146 63%55%4,218 30%28%115 28.7 2,040 708 1,175 ie)1,884 362 2,718 2,110 1,038 101 70%59%3,774 40%37%96 28.6 2,135 713 1,171 0 1,884 270 2,658 1,717 929 84 74%(61%3,607 50%44%82 28.7 2,137 712 1,171 0 1,884 267 2,436 1,382 817 67 77%=64%3,436 60%51%71 27.9 2,140 714 1,170 0 1,884 263 2,328 1,265 771 56 78%65%3,366 70%59%61 27.0 2,153 704 1,179 0 1,884 259 2,202 1,108 714 48 80%67%3,278 *80%67%53 25.8 2,167 716 1,168 0 1,884 236 928 655 41 B2%69%3,1882,112 #Indicates 100-watt TV load from 1900 to 2300 added to basic residential load. C Indicates that system also powers medical clinic and village office. Annual cost consists of capital charge (only for major components Listed above,and based on 10%nominal interest rate over 20-yr period) and fuel charge (based on consumption rate of 0.51 gal/hr and fuel price of $3.00 per gallon). MONTHLY SUMMARY FOR *SPECIFIED CYCLE DEPTH AC No.of Avg.Battery PV PY PV Diesel Diesel Diesel Diesel No.of Gal.of Load Battery Cycle kWh to kWh to kWh to kWh to Total kWh to kwh to kWh to Total Diesel Diesel Month (kWh)Cycles Depth AC Load AC Load Battery Surplus kWh AC Load Battery Surplus Hours Starts Fuel Jan 298 7 82%255 9 14 0 23 52 367 451 114 7 58 Feb 269 6 81%228 29 73 0 102 30 301 149 96 6 49 Mar 238 1 81%181 68 164 0 232 6 53 21 16 1 8 Apr 230 5 31%151 94 198 0 292 3 49 23 15 1 8 May 208 3 22%109 115 169 0 284 0 0 0 0 0 0 Jun 202 4 18%102 115 160 0 275 0 0 0 0 0 0 Jul 208 2 43%124 97 117 0 214 3 44 28 15 1 8 Aug 208 2 80%133 85 104 0 189 5 94 51 30 2 15 Sep 230 3 81%176 55 95 0 151 15 150 69 47 3 24 Oct 238 5 81%201 30 51 0 81 23 256 116 79 5 40 Nov 288 7 82%249 17 21 0 39 41 373 151 113 7 58 Dec 298 8 82%258 2 1 0 3 56 425 169 130 8 66 Number of PV panels:18 (1.35 kWp)5 kW GENERATOR NO.HOUSEHOLDS:34 Battery amp-hrs:1482 (2-stage charging regime);System capital cost:$25,550 ($6,340 for generator,$3,197 for PCU,$9,118 for PV panels,$4,486 for batteries,$2,409 for shipping) ANNUAL SUMMARY FOR DIFFERENT SPECIFIED CYCLE DEPTHS Spec.Avg.Battery Battery Battery PV PV PV PV Diesel Diesel Diesel Diesel No.of EFFICIENCY Annual Cycle Cycle Cycles Life kWh to kWh to kWh to kWh to Total kWh to kWh to kWh to Total Diesel Cost Depth Depth per yr (yrs)AC Load AC Load Sattery Surplus kwh AC Load Battery Surplus Hours Starts Ext Int ($/yr) 20%20%197 19.9 2,410 684 1,199 0 1,884 479 3,825 4,105 1,682 186 60%54%4,759 30%29%136 23.8 2,424 706 1,177 0 1,884 445 3,363 2,591 1,280 127 69%=59%4,144 40%40%105 25.0 2,491 710 1,173 0 1,884 380 3,199 2,161 1,148 101 72%61%3,942 50%48%91 24.3 2,537 702 1,182 0 1,884 344 3,035 1,806 1,037 84 74%64%3,773 60%60%69 25.4 2,493 708 1,176 0 1,884 379 2,821 1,480 936 68 77%=66%3,618 70%71%61 23.3 2,568 704 1,180 (0)1,884 314 2,764 1,407 897 60 78%=68%3,558 *80%79%56 21.2 2,595 703 1,180 0 1,884 289 2,704 1,288 856 54 79%=69%3,496 #Indicates 100-watt TV load from 1900 to 2300 added to basic residential load. C Indicates that system also powers medical clinic and village office. Annual cost consists of capital charge (only for major components Listed above,and based on 10%nominal interest rate over 20-yr period) and fuel charge (based on consumption rate of 0.51 gal/hr and fuel price of $3.00 per gallon). MONTHLY SUMMARY FOR *SPECIFIED CYCLE DEPTH AC No.of Avg.Battery PV PV PV PV Diesel Diesel Diesel Diesel No.of Gal.of Load Battery Cycle kWh to kWh to kWh to kwh to Total kWh to kWh to kwh to Total Diesel Diesel Month (kWh)=Cycles Depth AC Load AC Load Battery Surplus kWh AC Load Battery Surplus Hours Starts Fuel Jan 335 9 81%298 9 14 0 23 50 468 202 144 9 73 Feb 302 6 82%256 29 73 0 102 39 307 134 96 6 49 Mar 275 4 82%215 62 170 0 232 19 178 123 64 4 33 Apr 266 4 45%186 89 202 0 292 11 85 60 31 2 16 May 246 0 0%148 115 169 0 284 0 0 0 0 0 0 Jun 238 0 0%138 116 159 0 275 0 0 0 0 0 0 Jul 246 2 80%159 97 117 0 214 7 88 95 30 2 15 Aug 246 2 81%170 86 104 0 189 7 99 49 32 3 16 Sep 266 5 81%210 54 96 0 151 21 244 120 76 4 39 Oct 275 6 80%235 29 52 0 81 30 294 146 94 6 48 Nov 324 8 81%276 15 23 0 39 55 414 171 128 8 65 Dec 335 10 81%304 2 1 0 3 51 528 227 161 10 82 Number of PV panels:18 (1.35 kWp)5 kW GENERATOR NO.HOUSEHOLDS:4 Battery amp-hrs:2110 (2-stage charging regime);a System capital cost:$28,731 {$6,340 for generator,$3,197 for PCU,$9,118 for PV panels,$6,955 for batteries,$3,121 for shipping) ANNUAL SUMMARY FOR DIFFERENT SPECIFIED CYCLE DEPTHS Spec.Avg.Battery Battery Battery PV PV PV PV Diesel Diesel Diesel Diesel No.of EFFICIENCY Annual Cycle Cycle Cycles Life kWh to kWh to kwh to kWh to Total kwh to kWh to kWh to Total Diesel Cost Depth Depth per yr (yrs)AC Load AC Load Battery Surplus kWh AC Load Battery Surplus Hours Starts Ext Int ($/yr) 20%21%155 25.0 2,765 804 1,079 0 1,884 591 4,756 1,963 1,462 156 79%54K 4,695 30%31%108 29.2 2,806 822 1,062 0 1,884 537 4,200 1,473 1,242 109 82%59%4,358 40%41%88 29.3 2,910 825 1,059 0 1,884 437 4,030 1,068 1,107 88 86%61%4,152 50%51%71 29.7 2,890 811 1,073 0 1,884 469 3,714 897 4,016 71 87%64%4,013 60%61%62 28.0 2,981 811 1,073 0 1,884 384 3,714 777 975 62 89%65%3,950 70%70%55 26.2 2,949 809 1,075 0 1,884 416 3,531 698 929 54 89%67%3,879 *80%81%47 24.5 2,999 806 1,078 0 1,884 373 3,412 655 888 47 90%69%3,817 #Indicates 100-watt TV load from 1900 to 2300 added to basic residential load. C Indicates that system also powers medical clinic and village office. Annual cost consists of capital charge (only for major components Listed above,and based on 10%nominal interest rate over 20-yr period) and fuel charge (based on consumption rate of 0.51 gal/hr and fuel price of $3.00 per galton). MONTHLY SUMMARY FOR *SPECIFIED CYCLE DEPTH AC No.of Avg.Battery PV PV PV PV Diesel Diesel Diesel Load Battery Cycle kWh to kWh to kWh to kWh to Total kWh to kWh to kWh to Month (kWh)=Cycles Depth AC Load AC Load Battery Surplus kWh AC Load Battery Surplus Jan 397 7 82%348 9 14 0 23 68 524 83 Feb 358 6 82%296 32 71 0 102 58 430 77 Mar 317 3 82%242 78 153 0 232 21 216 39 Apr 307 1 81%215 110 181 0 292 6 65 19 May 278 1 81%165 129 154 0 284 4 57 23 Jun 269 0 0%156 134 142 0 275 0 0 0 Jul 278 2 80%178 109 104 0 214 11 138 31 Aug 278 3 81%192 90 99 0 189 15 195 59 Sep 307 4 81%237 63 88 0 151 30 283 67 Oct 317 5 81%276 33 48 ie]81 32 359 69 Nov 384 7 82%340 16 23 0 39 58 525 92 Dec 397 8 82%353 2 1 0 3 71 619 95 Diesel No.of Gal.of Total Diesel Diesel Hours Starts Fuel 135 7 69 113 6 58 55 3 28 18 41 9 17 1 9 0 0 0 36 2 18 54 3 28 76 4 39 92 5 47 135 7 69 157 8 80 Number of PV panels: Battery amp-hrs: System capital cost: 18 2110 $28,731 a1.35 kWp) (2-stage charging regime) ;-($6,340 for generator,$3,197 for PCU,$9,118 for PV panels,$6,955 for batteries,$3,121 for shipping) 5 kW GENERATOR ANNUAL SUMMARY FOR DIFFERENT SPECIFIED CYCLE DEPTHS NO.HOUSEHOLDS:4# Spec.Avg.Battery Battery Battery PV PV PV PV Diesel Diesel Diesel Diesel No.of EFFICIENCY Annual Cycle Cycle Cycles Life kWh to kWh to kWh to kwh to Total kWh to kwh to kWh to Total Diesel Cost Depth Depth per yr (yrs)AC Load AC Load'Battery Surplus kWh AC Load Battery Surplus Hours Starts Ext Int ($/yr) 20%21%187 20.6 3,210 784 1,100 0 1,884 797 5,731 2,427 4,791 187 78%53%5,198 30%31%139 22.8 3,304 794 1,089 0 1,884 698 5,187 1,816 1,540 138 81%58%4,814 40%41%108 23.8 3,401 807 1,077 0 1,884 600 4,900 1,391 1,378 109 84%61%4,566 50%51%88 24.0 3,400 803 1,081 0 1,884 603 4,582 1,086 1,254 89 87%=63%4,377 60%61%75 23.0 3,404 799 1,085 0 1,884 602 4,399 974 1,195 75 88%65%4,286 70%71%68 20.7 3,538 792 1,092 ie)1,884 486 4,493 935 1,183 68 88%65%4,268 *80%81%59 19.7 3,491 789 1,095 0 1,884 532 4,229 794 1,111 59 89%67%4,158 #Indicates 100-watt TV load from 1900 to 2300 added to basic residential load. C Indicates that system also powers medical clinic and village office. Annual cost consists of capital charge (only for major components listed above,and based on 10%nominal interest rate over 20-yr period) and fuel charge (based on consumption rate of 0.51 gal/hr and fuel price of $3.00 per gallon). MONTHLY SUMMARY FOR *SPECIFIED CYCLE DEPTH AC No.of Avg.Battery PV PV PV PV Diesel Diesel Diesel Diesel No.of Gal.of Load Battery Cycle kWh to kWh to kWh to kWh to Total kWh to kWh to kWh to Total Diesel DieselMonth(kWh)=Cycles Depth AC Load AC Load Battery Surplus kWh AC Load Battery 'Surplus Hours Starts Fuel Jan 446 8 81%391 10 13 0 23 79 604 9 156 8 80 Feb 403 6 81%331 35 68 0 102 69 452 79 121 7 62 Mar 367 5 81%294 70 161 0 232 32 318 85 86 4 44 Apr 355 2 81%258 108 184 0 292 19 132 24 35 2 18 May 327 2 81%212 128 156 0 284 1 127 36 35 2 18 Jun 317 2 82%199 130 145 0 275 12 139 30 36 2 18 Jul 327 3 81%227 105 109 0 214 19 194 47 52 3 27 Aug 327 3 81%233 94 95 0 189 23 224 47 60 4 31 Sep 355 5 81%289 62 88 ie]151 32 340 73 88 4 45 Oct 367 6 82%302 31 50 0 81 61 492 77 127 7 65 Nov 432 8 81%365 14 24 0 39 8&5 546 94 145 8 74 Dec 446 9 81%388 2 1 0 3 89 661 105 170 8 87 APPENDIX C No.of Honda Starts NO.HOUSEHOLDS: EFFICIENCY Ext Int 1H Annual Cost ($/yr) 92% 93% 95% 97% 97% 96% 54% 59% 63% 67% 69% 70% Number of PV panels:8 (0.60 kWp)1.8 kW GENERATOR Battery amp-hrs:1055 (2-stage charging regime)System capital cost:$12,246 ($1,000 for generator,$1,708 for PCU,$4,535 for PV panels,$3,478 for batteries,$1,525 for shipping) ANNUAL SUMMARY FOR DIFFERENT SPECIFIED CYCLE DEPTHS Spec.Avg.Battery Battery Battery PV PV PV PV Honda Honda Honda Honda Cycle Cycle Cycles Life kWh to kWh to kwh to kwh to Total kWh to kWh to kwh to Total Depth Depth per yr (yrs)AC Load AC Load Battery Surplus kwh AC Load Battery Surplus Hours 20%19%87 40.0 859 288 550 0 837 83 1,147 181 784 30%29%61 40.0 861 287 550 0 837 81 968 136 659 40%38%47 40.0 863 286 551 0 837 81 852 91 569 50%47%36 40.0 872 287 550 0 837 72 758 59 496 60%55%31 40.0 883 287 550 it)837 61 726 51 465 70%63%27 40.0 885 287 550 0 837 60 694 58 451 *80%71%25 40.0 887 287 550 0 837 58 685 51 441 97%=71% 2,051 1,891 1,776 1,680 1,643 1,625 1,612 #Indicates 100-watt TV load from 1900 to 2300 added to basic residential load. C Indicates that system also powers medical clinic and village office. Annual cost consists of capital charge (only for major components Listed above,and based on 10%nominal interest rate over 20-yr period) and fuel charge (based on consumption rate of 0.32 gal/hr and fuel price of $4.00 per gallon). MONTHLY SUMMARY FOR *SPECIFIED CYCLE DEPTH AC No.of Avg.Battery PV PV PV PV Honda Honda Honda Honda No.of Gal.of Load Battery Cycle kWh to kWh to kwh to kWh to Total kWh to kWh to kWh to Total Honda Honda Month (kWh)=Cycles Depth AC Load AC Load Battery Surplus kwh AC Load Battery Surplus Hours Starts Fuel Jan 112 4 81%105 4 6 0 10 12 133 10 86 4 28 Feb 101 3 81%8&9 12 34 0 46 9 96 6 62 3 20 Mar 92 ,0 0%75 27 76 0 103 ie)0 0 0 0 0 Apr 8&9 "4 56%62 37 93 0 130 0 0 0 0 0 0 May 82 1 3%47 44 82 ie)126 0 0 0 0 0 0 Jun 79 1 22%43 46 76 0 122 ie)0 0 0 0 ie] Jul 82 1 1%52 40 55 0 95 Oo 0 ie)0 0 0 Aug 82 1 80%57 33 51 0 84 2 28 4 19 1 6 Sep 89 1 81%73 23 44 0 67 2 32 3 21 1 7 Oct 92 3 81%83 12 24 i)36 6 95 8 61 3 20 Nov 108 4 80%99 6 11 0 17 12 131 10 85 4 27 Dec 112 5 81%105 1 0 0 1 15 168 10 107 5 34 \\\>. Row mole /o/b m\nati ng porods of Now deword)Cradio!)CHS hes/lay ),Elin phe hitelen <p S€hy Ady-Corda]sy ete in av fie sell,Aicodveteged by pod fodawned Number of PV panels:8 (0.60 kWp)1.8 kW GENERATOR NO.HOUSEHOLDS:1 Battery amp-hrs:1055 (2-stage charging regime); System capital cost:$12,246 ($1,000 for generator,$1,708 for PCU,$4,535 for PV panels,$3,478 for batteries,$1,525 for shipping) ANNUAL SUMMARY FOR DIFFERENT SPECIFIED CYCLE DEPTHS Spec.Avg.Battery Battery Battery PV PV PV PV Honda Honda Honda Honda No.of EFFICIENCY Annual Cycle Cycle Cycles Life kWh to kwh to kWh to kWh to Total kWh to kWh to kWh to Total Honda Cost Depth Depth per yr (yrs)AC Load AC Load Battery Surplus kWh AC Load Battery Surplus Hours Starts Ext Int ($/yr) 20%19%76 40.0 731 286 552 0 837 65 949 154 649 66 92%52%1,878 30%28%52 40.0 742 285 552 0 837 56 783 105 524 45 94%58%1,718 40%36%40 40.0 745 287 550 0 837 51 708 77 465 34 95%61%1,643 50%44%32 40.0 737 288 549 0 837 58 641 50 416 27 97%=63%1,580 60%51%29 40.0 750 287 550 0 837 46 624 51 401 23 97%=64%1,561 70%58%26 40.0 755 285 553 0 837 43 603 52 388 21 97%66%1,544 *80%64%23 40.0 755 288 549 0 837 41 560 38 355 7 97%=68%1,502 #Indicates 100-watt TV load from 1900 to 2300 added to basic residential load. C Indicates that system also powers medical clinic and village office. Annual cost consists of capital charge (only for major components listed above,and based on 10%nominal interest rate over 20-yr period) and fuel charge (based on consumption rate of 0.32 gal/hr and fuel price of $4.00 per gallon). MONTHLY SUMMARY FOR *SPECIFIED CYCLE DEPTH AC No.of Avg.Battery PV PV PV PV Honda Honda Honda Honda No.of Gal.of Load Battery Cycle kWh to kWh to kwh to kWh to Total kWh to kWh to kWh to Total Honda Honda Month (kWh)=Cycles Depth AC Load AC Load Battery Surplus kWh AC Load Battery Surplus Hours Starts Fuel Jan 99 3 80%94 4 6 0 10 10 122 7 78 4 25 Feb 90 3 80%81 13 33 0 46 5 76 7 48 2 45 Mar 79 0 0%62 27 76 0 103 0 0 0 0 0 0 Apr 77 ,1 50%49 37 93 0 130 0 0 0 0 0 0 May 69 "2 9%35 44 82 0 126 0 0 0 0 0 0 Jun 67 3 o%31 45 77 0 122 0 0 0 0 0 ) Jul 69 0 0%39 40 55 0 95 0 0 0 0 0 0 Aug 69 0 0%45 35 50 0 84 0 0 0 0 0 0 Sep 77 1 80%61 24 43 0 67 2 33 2 20 1 6 Oct 79 2 81%73 12 24 0 36 4 65 5 41 2 13 Nov 96 4 80%87 6 11 0 17 11 131 9 84 4 27 Dec 99 4 80%98 1 0 0 1 10 133 8 84 4 27 p é 7 ELE ene Lo,none -vio Ge ,|higher Ther vestdent jel we cod f syste,;Pl6-Ls demadBy cerbal oes we by v enach roded hodle,Loy hene-gyid tyson”w es PI -NL geyor tov [azt 20 Vos be;Oveyr Jee |™ceded ° Pho - Canta]diese |cyte i.boeed OK Sy hy heyrestelerdialerevqyVS°Compartey ples to J ages ) Vi.TL Whe]P 4.5 bk |7412 Be |/get =Or 2y.lpet Le bet [197000Bt No nde °6.6 khk|34/3 pe [ae =O15gellpdud[ias 000 2, contrad?&EERMbyi2 OLE 7 13 000 re -Conacdey carta gone vaton wf wate Loot foyworketeriettp-orbyezeo:Uvfeir bo Com pare cystem tht preducevedtlyyeryingcontin§of eke.Corsider-coxtval Sec!cyte.wi /Latery tovage?-Use waite heat From cortral sydten in ebss tion -ler=Design frerzers te vse OA why Resible?_What ly lng term goal! h ray UG-@$P