HomeMy WebLinkAboutThe Alaska Village Electric Load Calculator Tech Report NREL 10-2004The Alaska Village Electric
Load Calculator
October 2004 • NREL/TP-500-36824
M. Devine
University of Massachusetts Amherst
E.I. Baring-Gould
National Renewable Energy Laboratory
National Renewable Energy Laboratory
1617 Cole Boulevard, Golden, Colorado 80401-3393
303-275-3000 • www.nrel.gov
Operated for the U.S. Department of Energy
Office of Energy Efficiency and Renewable Energy
by Midwest Research Institute • Battelle
Contract No. DE-AC36-99-GO10337
National Renewable Energy Laboratory
1617 Cole Boulevard, Golden, Colorado 80401-3393
303-275-3000 • www.nrel.gov
Operated for the U.S. Department of Energy
Office of Energy Efficiency and Renewable Energy
by Midwest Research Institute • Battelle
Contract No. DE-AC36-99-GO10337
October 2004 • NREL/TP-500-36824
The Alaska Village Electric
Load Calculator
M. Devine
University of Massachusetts Amherst
E.I. Baring-Gould
National Renewable Energy Laboratory
Prepared under Task No. WER4.6002
NOTICE
This report was prepared as an account of work sponsored by an agency of the United States
government. Neither the United States government nor any agency thereof, nor any of their employees,
makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy,
completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents
that its use would not infringe privately owned rights. Reference herein to any specific commercial
product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily
constitute or imply its endorsement, recommendation, or favoring by the United States government or any
agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect
those of the United States government or any agency thereof.
Available electronically at http://www.osti.gov/bridge
Available for a processing fee to U.S. Department of Energy
and its contractors, in paper, from:
U.S. Department of Energy
Office of Scientific and Technical Information
P.O. Box 62
Oak Ridge, TN 37831-0062
phone: 865.576.8401
fax: 865.576.5728
email: mailto:reports@adonis.osti.gov
Available for sale to the public, in paper, from:
U.S. Department of Commerce
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
phone: 800.553.6847
fax: 703.605.6900
email: orders@ntis.fedworld.gov
online ordering: http://www.ntis.gov/ordering.htm
Printed on paper containing at least 50% wastepaper, including 20% postconsumer waste
iii
TABLE OF CONTENTS
INTRODUCTION ..............................................................................................................1
ANALYSIS OF ELECTRIC USAGE IN ALASKAN VILLAGES ..................................1
ALASKA VILLAGE ELECTRIC LOAD CALCULATOR...............................................2
Residential Sector Loads................................................................................................3
Village Schools..............................................................................................................4
Village Public Water System.........................................................................................6
Village Health Clinics..................................................................................................10
City and Government Sector Loads.............................................................................11
Commercial Sector Loads............................................................................................13
Communications Facilities ..........................................................................................14
Other Loads..................................................................................................................16
Daily Village Load Profiles.........................................................................................16
HOW TO USE THE ALASKA VILLAGE ELECTRIC LOAD CALCULATOR...........19
Verification of Village Electric Load Calculator Method ...........................................21
CONCLUSIONS................................................................................................................24
BIBLIOGRAPHY..............................................................................................................25
LIST OF FIGURES
Figure 1. Relative load consumption by facility type in a typical village ...........................1
Figure 2. Annual change in village electric usage by sector...............................................2
Figure 3. Energy consumption of residential sector in sample villages ..............................3
Figure 4. Seasonal electric consumption of residential sector.............................................4
Figure 5. Energy consumption of sample village schools...................................................5
Figure 6. Energy consumption of village K-12 school........................................................6
Figure 7. Energy consumption of sample Level I piped water systems. .............................7
Figure 8. Energy consumption of Level I public water systems..........................................8
Figure 9. Energy consumption of Level II public water systems........................................8
Figure 10. Energy consumption of Level II public water systems......................................9
Figure 11. Energy consumption of sample village health clinics......................................10
Figure 12. Electric consumption of village health clinics..................................................11
Figure 13. Energy consumption of sample city/government buildings.............................11
Figure 14. Energy consumption of city buildings..............................................................12
Figure 15. Energy consumption of sample commercial facilities......................................13
Figure 16. Energy consumption of commercial buildings.................................................14
Figure 17. Energy consumption of sample communications facilities..............................15
Figure 18. Energy consumption of communications sector loads.....................................16
Figure 19. Daily load profiles for Selawik, Alaska ...........................................................17
Figure 20. January daily load profile for sample villages..................................................18
Figure 21. July daily load profiles for sample villages......................................................18
iv
Figure 22. Example results from the Alaska Village Electric Load Calculator.................20
Figure 23. Estimated hourly electric load in Brevig Mission............................................20
Figure 24. Brevig Mission 2003 estimate versus actual consumption ..............................21
Figure 25. Village Electric Load Calculator results for the village of Toksook Bay ........22
Figure 26. Village Electric Load Calculator results for the village of Mekoryuk.............22
Figure 27. Village Electric Load Calculator results for the village of Kiana ....................23
Figure 28. Load calculator model verification – village of Selawik..................................24
LIST OF TABLES
Table 1. Electric Consumption of Residential Sector..........................................................4
Table 2. Energy Consumption of K-12 Schools..................................................................5
Table 3. Energy Consumption of Level I Public Water Systems........................................7
Table 4. Energy Consumption of Level II Public Water Systems.......................................9
Table 5. Electric Consumption for Village Health Clinics................................................10
Table 6. Electric Consumption of City and Government Buildings..................................12
Table 7. Electric Consumption of Commercial Facilities..................................................13
Table 8. Energy Consumption of Communications Sector ...............................................15
Table 9. Electric Load Calculator Inputs for Brevig Mission............................................19
Table 10. Village Electric Load Calculator Inputs for the Village of Toksook Bay.........21
Table 11. Village Electric Load Calculator Inputs for the Village of Mekoryuk..............22
Table 12. Village Electric Load Calculator Inputs for the Village of Kiana .....................23
Table 13. Load Calculator Inputs for Selawik...................................................................24
1
INTRODUCTION
About a quarter of Alaska’s population of 640,000 live in isolated villages scattered across the
state. More than 118 independent utilities provide electricity to Alaska’s geographically,
economically, and culturally diverse range of communities (Alaska Energy Authority, 2003).
Alaska’s rugged terrain and lack of roadway systems make supplying its rural communities with
electricity a challenge. Most of these communities are powered by diesel minigrids of up to 3
megawatts (MW) in capacity. As the electric demand in these villages continues to grow, many
of the power plant complexes are in need of major upgrades. Due to the high operation and
maintenance costs of diesel systems, as well as the environmental hazards associated with diesel
generators, some villages are investigating the possibility of integrating wind energy into the
existing diesel power system.
As part of designing a village electric power system, the present and future electric loads must be
defined, including both seasonal and daily usage patterns. However, in many cases, detailed
electric load information is not readily available. NREL developed the Alaska Village Electric
Load Calculator to help estimate the electricity requirements in a village given basic information
about the types of facilities located within the community. The purpose of this report is to
explain how the load calculator was developed and to provide instructions on its use so that
organizations can then use this model to calculate expected electrical energy usage.
The Alaska Village Electric Cooperative (AVEC), a nonprofit rural electric utility based in
Anchorage, operates about 50 power stations serving remote villages ranging in size from 100 to
1,100 residents. Much of the data used in this analysis was provided by AVEC and this paper
will use those villages as examples. However, the Alaska Village Electric Load Calculator can
also be applied to non-AVEC villages in Alaska and other similar remote arctic communities.
ANALYSIS OF ELECTRIC USAGE IN ALASKAN VILLAGES
To begin the electric load analysis, the electric consumption from a number of communities was
broken down into its primary components: residential sector, schools, commercial sector, public
water system, city/ government buildings, communications facilities, and the health clinic.
Figure 1 shows the relative size of each of those sectors from one of the villages.
Figure 1. Relative load consumption by facility type in a typical village.
2
The residential sector is the largest consumer group, followed by the school. The commercial
sector makes up about 10% of the village electric consumption and typically includes a general
store, hardware store, and a number of restaurants. Figure 2 shows the annual growth in energy
demand from each sector that makes up AVEC’s customer base. These data are valuable as they
provide insight to the primary load growth areas within a community.
Figure 2. Annual change in village electric usage by sector.
The residential sector, generally the largest load sector, increases at a gradual rate of about 4%
per year through general consumption increases and new housing connections. The expansion of
municipal services, schools, and commercial applications provide large and highly variable load
increases to a community. Due to funding processes of facility expansion, both municipal and
school expansions are widely known and can be planned into power systems needs accordingly,
thus limiting surprise impacts. Expansion of commercial loads is not easy to plan for and could
quickly change the energy needs of a community. However, commercial loads generally make up
less than 15% of a community’s total load, and thus large increases will have a limited impact
compared to the residential and municipal loads that make up the remaining 85% of a
community’s electricity needs.
ALASKA VILLAGE ELECTRIC LOAD CALCULATOR
The electric use patterns of each consumer sector was investigated in detail based on the electric
utility records. The consumption patterns were then incorporated into the Alaska Village Electric
Load Calculator, which adds up the various load profiles within a village using a building block
approach. This report describes the method used to create the building blocks for each consumer
sector and the procedure for using the calculator to determine hourly electric load data.
Throughout this analysis the energy consumption of certain loads has been normalized by the
population within each community. This allows easy comparisons between communities of
various sizes and also acts as a reasonable baseline for community level services and energy use.
Other normalization techniques were investigated; however, normalization by total community
population provided the most promising results. Some loads, such as the communication sector,
which are not dependent on the size of a community have not been normalized.
3
Residential Sector Loads
The residential sector generally makes up about 45% of a village’s total electric consumption.
Electric loads found in typical homes include lighting, a color TV, electric stove, refrigerator,
forced air fan, and a clock radio. Homes with piped water may have electric heat tape to prevent
water mains from freezing. More modern homes might have a computer, washer and dryer,
satellite dish, microwave, and additional lights and television sets (Vallee, 2003). The more
modern homes will use as much as 1,000 kilowatt-hours (kWh) or more a month; however, the
majority of village homes use 200 to 400 kWh per month.
It is difficult to characterize the monthly electric consumption of the residential sector because
billing information for individual consumers is not readily available. However, the energy
consumption of the residential sector in six different villages was obtained for the three months of
November 2002, April 2003, and July 2003. The results are shown in Figure 3. The data points
for the remaining nine months were estimated based on the seasonal shape of the total village
load profile. The resulting average seasonal electric load profile for the residential sector is also
shown in Figure 3.
Figure 3. Energy consumption of residential sector in sample villages
To determine why some villages have a higher per capita residential electric consumption than
other villages, characteristics relating to the residential sector in each village were gathered.
Statistics from the 2000 U.S. Census, such as people per household, unemployment rate, percent
of population below poverty, and per capita income, were chosen because they were readily
available and could easily be compared with other villages (Department of Community and
Economic Development, 2003). Comparing the community statistics to the per capita energy
consumption of each village, it seemed that the median household income most closely correlated
to the level of energy use. This assumption coincides with reports concluding that economic
growth is directly related to an increase in household energy consumption. As the level of
household income increases, residents often purchase larger housing units and additional
appliances, leading to increased energy consumption (Energy Information Administration, 2004).
4
The average median household income for remote villages in AVEC’s service territory is about
$31,500. Based on this median, Table 1 divides the residential sector into three income
categories.
Table 1. Electric Consumption of Residential Sector
Category: Low Medium High
Median Household
Income: Less than $25,000 $25,000 to $35,000 More than
$35,000
Monthly
Consumption
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
(kWh/person/mo.)
89
84
88
78
65
58
55
62
68
70
72
81
(kWh/person/mo.)
118
105
110
96
90
84
82
92
101
105
109
115
(kWh/person/mo.)
159
142
146
128
123
121
121
129
141
147
150
155
Figure 4. Seasonal electric consumption of residential sector.
The values listed in Table 1 and shown in Figure 4 serve as the building block for the residential
sector to be included in the Alaska Village Electric Load Calculator.
Village Schools
As the largest individual consumer of electricity in a village, the local school has a great impact
on the total village electric load profile. The electric consumption of eight village schools from
1998 through June 2003 was observed to have a similar seasonal load pattern. An average year of
per capita electric consumption of each school is shown in Figure 5.
5
Figure 5. Energy consumption of sample village schools.
The variation in electric consumption between schools is due to the type of electrical equipment
available in the building as well as the hours of operation. Kasigluk has two school buildings, a
P-12 and a K-12. Combining their electric usage, they use more electricity per capita than the
other villages. The Brevig Mission school is in the mid range of electric consumption per capita.
Major loads within the school include air handling units, an electric dryer, water pumps for the
hot water radiator system, and kitchen appliances. For safety reasons, all ovens in the cafeteria
use electricity rather than propane. Heat is provided by oil-fired furnaces. The building,
particularly the gym and library, is used in the evenings and weekends for after school programs
and community meetings but is used very little in the summer (Davis, 2003). The Scammon Bay,
Togiak, and Toksook Bay schools are all located in maritime climates with limited electric
heating loads. To distinguish among the range of electric use between schools, these facilities are
divided into three categories, as described in Table 2.
Table 2. Energy Consumption of K-12 Schools
Category: Low Medium High
Characteristics:
Located in southern/
maritime climate
region, uses propane or
gas for heating and
cooking.
Average school with air
handling units and
some electrical
appliances.
Located in the arctic climate
region, has its own septic
system, uses electric heaters
and stoves, or more than one
building.
Monthly
Consumption
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
(kWh/person/month)
38.8
42.0
43.6
38.6
28.7
12.7
14.8
21.6
32.5
43.9
42.0
42.3
(kWh/person/month)
58.5
59.9
58.2
56.1
46.1
28.2
27.4
40.5
51.2
59.7
61.1
58.7
(kWh/person/month)
73.4
78.6
79.4
70.8
71.3
45.3
41.5
56.2
71.5
81.4
84.8
78.8
6
The monthly energy consumption of the different categories of schools is listed in Table 2 and
shown in Figure 6. These values serve as the building block for the school sector in the Alaska
Village Electric Load Calculator.
Figure 6. Energy consumption of village K-12 school.
Village Public Water System
Village public water systems include any facilities that supply water to a community and that
dispose of wastewater. There are many factors influencing the electric consumption of a public
water system, including the size of the population served, the level of treatment of the water and
wastewater, the method of distribution, and the climate. For the purposes of this report, village
public water systems are split into two groups – those that have the capacity to provide complete
plumbing to all or most residents, and those that do not.
Level I public water systems provide piped water and sewer to all city buildings and most homes.
These systems usually have above-ground water mains, which need to be protected from freezing.
Options include heating the water mains with electric heat tape, using a boiler to heat a glycol
loop that runs through the water distribution system, or continuously pumping the water through a
closed-loop distribution system. Figure 7 shows sample seasonal electric load profiles of Level I
public water systems in seven different villages normalized by village population.
7
Figure 7. Energy consumption of sample Level I piped water systems.
Even within this grouping, there is a significant amount of variation in electric usage throughout
the year. This range in electric use is influenced by the use of electricity to provide heat, the
pumping requirements of the facility, and the number of buildings served. The facilities that
consume the most electricity per capita (Emmonak, Selawik, and Brevig Mission) use electricity
for heating water mains. Chevak uses a gas-fired glycol loop to keep pipes from freezing, and
Kiana has buried water and sewer mains. Togiak and Toksook Bay are the southernmost
facilities, which do not have a threat of freezing water mains. Toksook Bay also has a gravity
piped system with limited pump requirements. To distinguish among the range of Level I public
water systems, these facilities are further divided into three categories based on electricity usage,
as described in Table 3.
Table 3. Energy Consumption of Level I Public Water Systems
Category: Low Medium High
Typical
Characteristics:
Not all buildings or homes
are connected. Gravity
sewer system or surface
water source (less pumping
load). No electric heat.
Most buildings and
homes are connected to
piped water and sewer.
No electric heat.
Circulating water and
vacuum sewer system.
All buildings and homes
serviced. Arctic climate/
electric heat tape on
pipes.
Monthly
Consumption
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
(kWh /person/month)
13.2
11.0
12.0
10.3
7.9
5.4
4.5
4.4
4.9
7.0
10.8
13.1
(kWh/person/month)
23.1
23.6
21.4
20.2
19.2
14.5
13.7
13.3
14.9
19.2
20.0
23.8
(kWh/person/month)
36.3
32.6
38.2
34.2
30.2
17.7
20.3
21.6
20.8
31.1
34.4
35.4
8
Figure 8 illustrates the monthly electric consumption of each category of Level I public water
system listed in Table 3.
Figure 8. Energy consumption of Level I public water systems
In Level II public water systems, water is pumped from a well or surface source, treated, and
stored in an insulated tank. The water is supplied to a central washeteria where residents can
collect water, bathe, and do laundry. Electric loads at these water treatment/washeteria facilities
include pumps, washing machines and dryers, lights, and sometimes an electric sauna. In some
villages, piped water is provided only to the school or health clinic. Level II systems do not treat
wastewater; instead, each resident collects their wastewater in five-gallon “honey buckets” and
hauls them to a sewage lagoon to be dumped. Almost half of Alaska’s 200 native villages have
this type of system where residents do not have running water or flush toilets in their homes
(Rural Alaska Sanitation Coalition website, 2003). Figure 9 shows seasonal electric load profiles
of several sample Level II systems.
Figure 9. Energy consumption of Level II public water systems.
The range in electric use among Level II systems is influenced primarily by the types of services
available in the washeteria and by the climate. For example, Stebbins is the most modern facility,
offering electric saunas in addition to electric washers, propane dryers, and showers. Kivalina
provides piped water to the health clinic, which accounts for its increased consumption per capita.
It is also the northernmost facility, which requires electric heat tape to keep pipes from freezing.
9
Eek, Nunapitchuk, and Toksook Bay are all located in the southwestern area of the state, which
rarely experiences temperatures below freezing and thus have minimal electric heating
requirements. To distinguish among the range of Level II public water systems, these facilities
are further divided into two categories, as described in Table 4.
Table 4. Energy Consumption of Level II Public Water Systems
Category: Low High
Typical
Characteristics:
Water comes from
surface source.
Limited washeteria
facilities. Limited use
of heat tape.
Water pumped from well or from a long
distance surface source. Washeteria has
electric saunas, electric dryers, or
extended hours of operation. Extensive
use of heat tape.
Monthly
Consumption
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
(kWh/person/month)
7.2
5.0
5.4
4.6
4.3
3.6
4.6
5.0
5.3
6.2
6.7
6.8
(kWh/person/month)
11.8
10.0
11.3
9.9
8.8
6.8
7.6
8.2
8.0
11.0
11.5
13.3
Figure 10. Energy consumption of Level II public water systems.
Figure 10 illustrates the energy consumption of the two categories of Level II public water
systems. The monthly electric use values listed in Table 3 and Table 4 serve as the building
block for the public water systems in the Alaska Village Electric Load Calculator. The electric
consumption of public water systems can vary drastically from village to village. Most villages
begin with a basic Level II system and gradually move towards a high Level I system as funding
becomes available.
10
Village Health Clinics
Each village typically operates a local health clinic staffed by community health aids. Regional
clinics located in St. Mary’s, Emmonak, Kiana, and Unalakeet, serve surrounding communities
with a physician assistant or nurse practitioner. Patients requiring special care are flown to
Anchorage or hospitals located in the hub cities of Kotzebue, Bethel, Nome, and Dillingham
(Maniilaq Association, 2003). The per capita electric consumption of nine sample health clinics
is shown in Figure 11.
Figure 11. Energy consumption of sample village health clinics.
The distinction between electric requirements in regional and local health clinics is clear; regional
clinics consume nearly six times more electricity per capita than local clinics. It should be noted
that only one year of data was available from the Kiana regional clinic so it is unknown if the
drop in consumption during July is typical. It is assumed that the actual consumption is closer to
9 kWh per person during July. The health clinic sector for rural villages is divided into two
categories, as described in Table 5.
Table 5. Electric Consumption for Village Health Clinics
Category: Local clinic Regional clinic
Monthly Consumption
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
(kWh/person/month)
1.9
1.7
1.9
1.7
1.5
1.4
1.3
1.3
1.4
1.7
1.7
1.8
(kWh/person/month)
12.9
11.7
12.0
12.0
11.6
11.2
10.6
11.9
11.0
12.8
11.8
13.4
11
Figure 12. Electric consumption of village health clinics.
The monthly electric consumption of the local and regional health clinics is listed in Table 5 and
illustrated in Figure 12. These values serve as the building block for the health clinic sector used
in the Alaska Village Electric Load Calculator.
City and Government Sector Loads
The city and government sector, which includes city offices, post offices, native tribal offices, and
community centers, makes up about 20% of a village’s electric use. Seasonal electric load
profiles of sample city/government buildings are shown in Figure 13.
Figure 13. Energy consumption of sample city/government buildings.
12
To distinguish among the range of electric use between city facilities, these loads are divided into
two electric use categories, as described in Table 6. The total city/government load in a village
can be made up of a number of buildings from each category. Note that the monthly
consumption is not normalized by city population as with other sectors, because the electric use
of these facilities is not as dependent on population.
Table 6. Electric Consumption of City and Government Buildings
Category: Small Large
Examples: Post office, city office,
native office, FAA, DOT
Gymnasium, community
center, large city office
Monthly
Consumption
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
(kWh/month)
774
781
837
913
720
592
544
564
595
686
706
692
(kWh/month)
2279
2198
2183
2035
1556
1299
1205
1468
1410
1768
1664
2330
Figure 14. Energy consumption of city buildings.
The monthly electric consumption of the typical city facilities is listed in Table 6 and illustrated
in Figure 14. These values make up the building block for the each city/government building in
the Alaska Village Electric Load Calculator.
13
Commercial Sector Loads
The commercial sector makes up about 15% of a village’s electricity consumption. Most villages
have one general store, while larger villages have up to four different stores. The commercial
sector also consists of various business offices and warehouses. The per capita electric load
profile for six sample commercial facilities is shown in Figure 15.
Figure 15. Energy consumption of sample commercial facilities.
To distinguish among the range of electric use between commercial facilities, these loads are
divided into two categories, as described in Table 7. Note that the monthly electric consumption
is not normalized by population as with other sectors, because the energy use in these facilities is
not dependent on community size.
Table 7. Electric Consumption of Commercial Facilities
Category: Small Business Large Commercial
Examples: Office, restaurant,
specialty store
Hardware store, native store, general
store, warehouse, construction company
Monthly Consumption
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
(kWh/month)
2,363
2,108
2,520
2,083
2,151
1,875
1,988
2,081
2,053
2,394
2,226
2,291
(kWh/month)
9,653
9,022
9,473
8,875
8,579
8,070
8,533
8,925
9,150
10,581
10,208
10,732
14
The monthly electric consumption of typical commercial facilities is summarized in Table 7 and
illustrated in Figure 16. One of these load profiles is added for each commercial facility in a
village to make up the building block for the commercial sector that is used in the Alaska Village
Electric Load Calculator.
Figure 16. Energy consumption of commercial buildings.
It is important to note that the seasonal profile for these commercial facilities is fairly steady.
Most, but not all, commercial facilities seem to follow this pattern. For example, fish-processing
plants have their peak use in the summer and use considerably less electricity in the winter. As
data from these facilities were not available, the electric use of unique commercial facilities such
as these would need to be added to the Village Electric Load Calculator separately.
Communications Facilities
Most villages have phone, cable, and internet service, although not all homes are connected. The
monthly electric consumption of sample communication service providers in six different villages
is shown in Figure 17.
15
Figure 17. Energy consumption of sample communications facilities.
The electric load of the communications service providers is relatively steady throughout the
year. The communications sector is divided into two categories: basic and advanced, as detailed
in Table 8. Note that the energy consumption is not normalized by population.
Table 8. Energy Consumption of Communications Sector
Category: Basic Advanced
Characteristics: Internet and/or
cable
Internet, cable,
radio tower
Monthly Consumption
Jan
Feb
Mar
Apr
May
June
July
Aug
Sept
Oct
Nov
Dec
(kWh/month)
2,303
2,060
2,202
1,975
1,919
1,860
1,807
1,800
1,707
1,882
2,032
2,204
(kWh/month)
6,870
5,996
6,870
6,502
6,373
6,698
6,231
6,371
6,204
5,927
5,363
7,552
The monthly energy consumption of the different types of communications facilities is listed in
Table 8 and illustrated in Figure 18. These values serve as the building block for the
communications sector that is used in the Alaska Village Electric Load Calculator.
16
Figure 18. Energy consumption of communications sector loads.
Other Loads
Other loads within a village may include an armory, streetlights, and churches. These electric
loads are estimated to add about 3% – 7% to the total village load. An option for specifying the
amount of other loads is included in the Village Electric Load Calculator. The value that is input
depends on the number of additional facilities in the village that are not accounted for in the
community sectors described previously.
Daily Village Load Profiles
Similar to the process described above, a daily load profile analysis can be performed that
separates the primary loads and looks at the daily changes in these loads. At the time of this
writing, time series data were not available for specific electricity consumers. Instead, what
follows is an analysis of the daily electric load profiles for eight different villages for which high
quality data were available. The villages are: Selawik, Chevak, Kiana, Gambell, Ambler,
Noorvik, Scammon Bay, and New Stuyahok. Each of these communities is a different size and
provides different levels of community services. The goal is to use this information, along with
knowledge of the seasonal load profiles described in the previous sections, to make general
estimates as to the electric usage in a typical Alaskan village. This information will then be
incorporated into the Alaska Village Electric Load Calculator to obtain an hourly electric load
data set.
The data used in this analysis were obtained from power stations where AVEC recorded the
instantaneous electric load once every 15 minutes. The four data points within each hour were
averaged to create an hourly electric load profile for each year. Figure 19 displays the daily
electric load profiles of an average day in each month for the village of Selawik. These daily
profiles were created by averaging each hour over every day of the month.
17
Figure 19. Daily load profiles for Selawik, Alaska.
As one would expect, the daily load profile for the community depends on the season. Villages
consume more electricity per capita throughout the day during the winter months than in the
summer months, due primarily to increased lighting and electric heating loads. However, while
the magnitude of the load fluctuates from summer to winter, the shape of the profile changes
little. The difference is that on winter days, there tends to be two peaks – one around 11:00 a.m.
and the other around 6:00 p.m., while on the summer days, the load remains fairly constant
between those hours. Also, the range between the minimum and peak load of the day is
shallower during the summer months than the winter months.
Comparing the shape of the daily profiles between villages results in clear similarities. To
demonstrate this, the hourly electric load values for the eight villages are normalized by village
population. Then each hourly value was divided by the peak load of the day so that each load
profile peaks at a value of 1. Figure 20 compares the January daily load profiles for the eight
different communities, and Figure 21 compares the July daily load profiles. It is important to
note that the shape of the profile in each month is similar between villages. The villages
represent a range of size, location, and community characteristics, yet the pattern of electric usage
throughout the day is comparable. Therefore, it is expected that the shape of the daily profile in
one village can be used to create a reasonable estimate of the daily profile in another village.
18
Figure 20. January daily load profile for sample villages.
Figure 21. July daily load profiles for sample villages.
In each graph there is a divergence in energy usage during the early hours of the day. This is
most likely due to the level of street lighting in the village and the use of electric heat tape on
water mains. Selawik, located in the northernmost part of Alaska, represents a village that has a
higher demand for early morning heating and lighting loads, even during summer months.
Scammon Bay, located along the southern coast of Alaska, represents a village that has a lower
demand for heating and lighting in the early morning hours. The hourly electric use patterns from
these two villages can be used to create hourly load data for other villages. The magnitude of the
daily profiles is adjusted by scaling the profile up or down depending on the monthly electric
consumption determined from the seasonal load profile described in the previous section.
19
HOW TO USE THE ALASKA VILLAGE ELECTRIC
LOAD CALCULATOR
There are two steps to using the Alaska Village Electric Load Calculator: 1) estimate the total
seasonal electric load profile for the village, and 2) use the seasonal profile to adjust each month
of hourly electric data from a representative village. An example of how to use the load
calculator is shown below for the village of Brevig Mission.
Step 1 is to estimate the village seasonal load profile by adding the profiles of each of the
individual sectors described previously. Table 9 summarizes the village characteristics that
determine which category of each community sector that the Village Electric Load Calculator
uses.
Table 9. Electric Load Calculator Inputs for Brevig Mission
Village Characteristics Value
Population 314
# of Small Businesses 2
# of Large Commercial
Businesses 0
# of Community Buildings 2
# of Government Offices 1
Median Household Income Low
K-12 School High
Public Water System Level 1 High
Health Clinic Local
Communications Basic
Other Loads 5%
20
The monthly electric consumption of each community sector that makes up the total village load
profile for Brevig Mission is shown in Figure 22.
Figure 22. Example results from the Alaska Village Electric Load Calculator.
The Second step in using the Alaska Village Electric Load Calculator is to create the daily
electric load data set. Because Brevig Mission is located in northern Alaska, a year of hourly data
measured from the village of Selawik (also located in northern Alaska) is used as a baseline. The
hourly values are then scaled up or down so that the total energy use for each month matches the
values estimated from the Village Electric Load Calculator in Step 1. The resulting hourly data
set is shown in Figure 23.
Figure 23. Estimated hourly electric load in Brevig Mission.
21
Verification of Village Electric Load Calculator Method
Figure 24 shows the estimated electric load profile determined from the load calculator method
versus the actual load profile from billing records for the village of Brevig Mission, Alaska.
Figure 24. Brevig Mission 2003 estimate versus actual consumption.
On average, the Village Electric Load Calculator underestimates the actual consumption by 9%.
Figures 25 through 27 show other village examples comparing the estimated load with actual
data. Each example shows a table of the load calculator inputs and a graph of the results. The
graph includes the electric consumption of the community facilities that make up the estimated
village load, a line showing the actual measured village consumption, and the percent difference
between the estimated and actual load for each month.
Table 10. Village Electric Load Calculator Inputs for the Village of Toksook Bay
Village Characteristic Value Village
Characteristic Value
Population 550 K-12 School Medium
# of Small Businesses 3 Public Water System Level II Low
# of Large Commercial
Businesses 0 Health Clinic Local
# of Community Buildings 2 Communications Basic
# of Government Offices 3 Other Loads 1%
Median Household Income Medium
22
Figure 25. Village Electric Load Calculator results for the village of Toksook Bay.
The average error between the estimated load and actual load is 8%.
Table 11. Village Electric Load Calculator Inputs for the Village of Mekoryuk
Figure 26. Village Electric Load Calculator results for the village of Mekoryuk.
Village Characteristic Value Village
Characteristic Value
Population 204 K-12 School Medium
# of Small Businesses 3 Public Water System Level I Medium
# of Large Commercial Businesses 1 Health Clinic Local
# of Community Buildings 1 Communications Basic
# of Government Offices 5 Other Loads 5%
Median Household Income Medium
23
The average error between the estimated load and actual load is 8%.
Table 12. Village Electric Load Calculator Inputs for the Village of Kiana
Figure 27. Village Electric Load Calculator results for the village of Kiana.
The average error between the estimated electric load and the actual electric load for the Kiana
example is 9%.
To evaluate the ability of the Village Electric Load Calculator to predict an increase in energy
consumption due to the addition of a facility in a community, we used the village of Selawik.
Selawik completed a series of construction projects between 1996 and 2001: a piped water and
sewer system project was begun in 1997 and completed in 2000, a village health clinic was
constructed in 1997, and a new K-12 school came online in 2000. The Village Electric Load
Calculator is used to estimate both the 1996 and the 2001 seasonal load profiles, given the
facilities that were available in Selawik at those times. The inputs that were used in the Electric
Load Calculator for each year are shown in Table 13.
Village Characteristic Value Village Characteristic Value
Population 400 K-12 School High
# of Small Businesses 4 Public Water System Level I High
# of Large Commercial Businesses 2 Health Clinic Local
# of Community Buildings 1 Communications Basic
# of Government Offices 3 Other Loads 5%
Median Household Income High
24
Table 13. Load Calculator Inputs for Selawik
Village Characteristics 1996 2001
Population 665 772
# of Small Businesses 3 4
# of Large Commercial Businesses 2 2
# of Community Buildings 1 1
# of Government Offices 3 4
Median Household Income Medium Medium
K-12 School Medium High
Public Water System Level II Low Level I High
Health Clinic Local Local
Communications Basic Basic
Other Loads 3% 5%
The estimated results are graphed in Figure 28 along with the actual energy consumption
determined from utility records.
Figure 28. Load calculator model verification – village of Selawik.
The load calculator estimation method is typically within 8% of the actual electric usage for both
years. The largest discrepancy occurs in December of 2001, when the actual usage was 24%
more than the estimated usage.
CONCLUSIONS
Based on an analysis of electrical use in a number of rural Alaskan communities, this report
presented a method to estimate the hourly electrical usage in a village -- one of the key pieces of
information required to conduct any detailed power system analysis. Using the Alaska Village
Electric Load Calculator method, one can build upon existing knowledge of expansion plans for
different communities or estimate the energy usage of non-electrified communities by simply
adding the different expected electric loads in a building block approach. Several examples were
given, which result in estimations within an average of 10% accuracy. The Village Electric Load
Calculator method of estimating village electric loads can serve as a useful guideline for power
system designers and utility planners.
25
BIBLIOGRAPHY
Alaska Village Electric Cooperative (AVEC). <http://www.avec.org>.
Alaska Energy Authority (AEA). <http://www.aidea.org/aea.htm>. Accessed Aug. 2003.
Coward, Mark. Hooper Bay City Office. Personal interview. May 2004.
Department of Community and Economic Development (DCED). Alaska Community Database.
<http://www.dced.state.ak.us/cbd/commdb/CF_BLOCK.htm>. Accessed June 2003 –
Aug 2004.
Davis, John. Bering Strait School District. E-mail correspondence. August 2003.
Energy Information Administration (EIA). “World Energy Use and Carbon Dioxide Emissions
1980-2001.” <http://www.eia.doe.gov>. May 2004.
Maniilaq Association. <http://maniilaq.org>. Accessed August 2003.
Petrie, Brent. Manager of Special Projects and Key Accounts. Alaska Village Electric
Cooperative. Personal correspondence. June 2003 – Aug 2004.
Rural Alaska Sanitation Coalition. <http://www.anhb.org/sub/rasc>. Accessed August 2003.
Rural Alaska Project Identification and Delivery System (RAPIDS). Department of Community
and Economic Development.
<http://www.dced.state.ak.us/cbd/commdb/CF_BLOCK.htm>. Accessed June to Aug
2004.
Vallee, Randy. Assistant Manager of Operations and Maintenance. Alaska Village Electric
Cooperative. E-mail correspondence. June 2003 and August 2004.
F1147-E(05/2004)
REPORT DOCUMENTATION PAGE Form Approved
OMB No. 0704-0188
The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources,
gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this
collection of information, including suggestions for reducing the burden, to Department of Defense, Executive Services and Communications Directorate (0704-0188). Respondents
should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a
currently valid OMB control number.
PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION.
1. REPORT DATE (DD-MM-YYYY)
October 2004
2. REPORT TYPE
Technical Report
3. DATES COVERED (From - To)
5a. CONTRACT NUMBER
DE-AC36-99-GO10337
5b. GRANT NUMBER
4. TITLE AND SUBTITLE
The Alaska Village Electric Load Calculator
5c. PROGRAM ELEMENT NUMBER
5d. PROJECT NUMBER
NREL/TP-500-36824
5e. TASK NUMBER
WER4.6002
6. AUTHOR(S)
M. Devine; E.I. Baring-Gould
5f. WORK UNIT NUMBER
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)
National Renewable Energy Laboratory
1617 Cole Blvd.
Golden, CO 80401-3393
8. PERFORMING ORGANIZATION
REPORT NUMBER
NREL/TP-500-36824
10. SPONSOR/MONITOR'S ACRONYM(S)
NREL
9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)
11. SPONSORING/MONITORING
AGENCY REPORT NUMBER
12. DISTRIBUTION AVAILABILITY STATEMENT
National Technical Information Service
U.S. Department of Commerce
5285 Port Royal Road
Springfield, VA 22161
13. SUPPLEMENTARY NOTES
14. ABSTRACT (Maximum 200 Words)
As part of designing a village electric power system, the present and future electric loads must be defined, including
both seasonal and daily usage patterns. However, in many cases, detailed electric load information is not readily
available. NREL developed the Alaska Village Electric Load Calculator to help estimate the electricity requirements
in a village given basic information about the types of facilities located within the community. The purpose of this
report is to explain how the load calculator was developed and to provide instructions on its use so that organizations
can then use this model to calculate expected electrical energy usage.
15. SUBJECT TERMS
wind energy; distributed energy; Alaska; load calculator; village electric power system;
16. SECURITY CLASSIFICATION OF: 19a. NAME OF RESPONSIBLE PERSON
a. REPORT
Unclassified
b. ABSTRACT
Unclassified
c. THIS PAGE
Unclassified
17. LIMITATION
OF ABSTRACT
UL
18. NUMBER
OF PAGES
19b. TELEPONE NUMBER (Include area code)
Standard Form 298 (Rev. 8/98)
Prescribed by ANSI Std. Z39.18