HomeMy WebLinkAboutSeldovia House Ground Source Heat Pump Project Design Narrative - Aug 2014 - REF Grant 7071031DESIGN NARRATIVE GROUND SOURCE HP PROJECT / SELDOLVIA HOUSE / CIHA Page 1 of 16
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DESIGN NARRATIVE
FOR
GROUND SOURCE HEAT PUMP PROJECT
TO PROVIDE SUPPLEMENTAL HEAT FOR
SPACE HEATING AND DOMESTIC HOT WATER
SELDOVIA HOUSE
COOK INLET HOUSING AUTHORITY
350 ALDER STREET, SELDOVIA, ALASKA 99663 USA
RENEWABLE ENERGY FUND ROUND 7 GRANT
FUNDED BY ALASKA ENERGY AUTHORITY
DESIGN MEMO UPDATED AUGUST 28, 2014
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TABLE OF CONTENTS
INTRODUCTION .............................................................................................................................. 3
SCOPE OF SERVICES ................................................................................................................... 3
EXISTING HEATING OIL USAGE (UPDATED THRU JUNE 2014) .............................................. 4
EXISTING ELECTRICITY USAGE .................................................................................................. 5
EXISTING HYDRONIC HEATING SYSTEM ................................................................................... 6
ADEQUACY OF EXISTING SPACE HEATING EQUIPMENT ....................................................... 7
ADEQUACY OF EXISTING DOMESTIC HOT WATER HEATING EQUIPMENT .......................... 8
NEW MECHANICAL SYSTEM CONFIGURATION WITH HEAT PUMP INTEGRATION ............. 8
ESTIMATE OF ANNUAL AND HOURLY HEATING DEMAND ..................................................... 9
EXISTING ELECTRICAL SYSTEM DESCRIPTION ..................................................................... 10
EXISTING GENERATOR CAPACITY ........................................................................................... 10
ELECTRICAL SERVICE CAPACITY ............................................................................................ 10
ELECTRICAL DESIGN CONCEPT ............................................................................................... 12
GROUND SOURCE HEAT PUMP SYSTEM EVALUATION OVERVIEW ................................... 13
VERTICAL WELL GROUND LOOPS PRELIMINARY DESIGN ............................................... 15
PROJECT ECONOMIC EVALUATION ......................................................................................... 15
VERTICAL WELL GROUND LOOPS OPINION OF PROBABLE COST ................................. 16
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INTRODUCTION
Cook Inlet Housing Authority secured the services of YourCleanEnergy LLC in May 2013 to
evaluate the potential for renewable energy sources to offset heating oil usage and cost for
Seldovia House, a 17,191 square foot existing senior housing complex with 18 residential units.
This evaluation was completed on September 13, 2013 and it concluded that ground source
heat pumps warmed by a vertical well field were a viable option to heating oil boilers. CIHA
applied for and was awarded grant funds for the project under the AEA Round VII Renewable
Energy Fund. In July 2014 CIHA secured the services of YCE in association with EDC, Inc and
Energy Efficiency Associates (EEA) to complete a design of the proposed ground source
vertical well field, and integration of new heat pumps into the existing oil boiler hydronic heating
system.
SCOPE OF SERVICES
CIHA is seeking an onsite ground source heat pump system design that has the potential to
reduce the current annual fuel oil costs at Seldovia House by at least seventy five percent
(75%). CIHA requires a construction and specification package designed to one hundred
percent (100%) completion suitable for bidding, and construction administration services during
the construction phase.
An initial site visit was conducted by the design team of Andy Baker (YCE), Kevin Hansen
(EDC), and Chuck Renfro (EEA) on July 15, 2014 to assess the existing mechanical systems,
and potential layout of the vertical well field. John Faschan (EDC) traveled to the site on July
25, 2014 to assess the existing electrical systems and determine if adequate service capacity
exists to accommodate new heat pumps.
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EXISTING HEATING OIL USAGE (UPDATED THRU JUNE 2014)
0
500
1,000
1,500
2,000
Seldovia House Monthly HeaƟng Oil Usage (gal)
Building
Heating
OIl
Heating oil for Seldovia House is supplied to CIHA by Seldovia Fuel & Lube; the delivered cost
of heating oil to CIHA in Seldovia was $5.34/gallon in June 2014. The total annual cost for
heating oil for the 2011/12 heating season (July thru June) was $54,300. The total annual
cost for heating oil for the 2013/14 heating season (July thru June) was $47,814. Heating
oil was consumed at approximately 86% AFUE in two oil boilers in the mechanical room for both
space heating and domestic hot water heating. It is estimated that approximately 85% of the
net heat from oil burn is directed to space heating load, and remaining 15% of net heat is
directed to domestic hot water heating load.
The target reduction in heating oil usage for this heat pump project is 75% of the total usage, or
approximately 7,500 gallons per year. At the current heating fuel price of $5.34/gallon, this
would equate to a savings in heating fuel expense of $40,000 per year. Electricity used for the
heat pump system and O&M costs must be subtracted from the heating fuel savings to obtain
the net annual cost savings for the heat pump project.
0
2000
4000
6000
8000
10000
12000
2011-2012 2012-2013 2013-2014
Annual HeaƟng Oil Usage - Seldovia House
Gallons
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EXISTING ELECTRICITY USAGE
Grid electricity for Seldovia House was purchased by CIHA from Homer Electric Association at
an effective rate of $0.17/KWH in June 2013. The total annual cost for electricity for the
2011/12 heating season (July thru June) was $22,811. The total annual cost for electricity
for the 2012/13 heating season (July thru June) was $21,500. The primary electric loads are
lighting, appliances (including stoves and electric dryers), and mechanical equipment for heating
and ventilating the building. The electricity provided is generated from hydro (@85%) and
natural gas (@15%) turbines in the region. For the purpose of this report, the rate of escalation
of grid electricity price is estimated to be 3% per year.
For the ground source heat pumps system, grid electricity would be used for source and load
side circulation pumps, for the heat pumps, and for heat pump controls. The economic return
over time for a ground source heat pump installation is heavily dependent on a favorable grid
electricity price and escalation in relation to the price and escalation of heating oil.
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EXISTING HYDRONIC HEATING SYSTEM
The heating system consists of two fuel-oil fired boilers rated at approximately 210,000 BTUH
each, supplying heating water to terminal units thru a set of circulating pumps operating in
primary/standby mode. The terminal units consist of individual living unit baseboards with zone
valves. Common areas, such as corridors, and kitchen are heated with cabinet unit heaters that
do not have zone valves, so heating water is continuously flowing through them, and fans are
controlled by room thermostats. Crawl spaces and utility areas are heated with horizontal unit
heaters with the same control as the cabinet unit heaters.
Domestic hot water is heated indirectly in tanks as a zone from the main heating supply,
requiring that the main system pumps run whenever hot water demand exists. The boilers are
controlled by a Tekmar 275 controller, with sensors on heating supply and return, and an
outdoor temperature sensor. The controller also receives a demand signal from the domestic
water heaters to increase the boiler temperature for water heating.
Operational problems with the existing system were noted during the site visit: The continuous
flow through unit heaters and cabinet unit heaters tends to overheat the common spaces, as the
boilers maintain a minimum temperature. It was discovered that only one of the two water
heaters had a thermostat connected to operate both zone valves, and the tank with the
operating thermostat had an inoperable zone valve. The tank with the thermostat was colder
and commanded open the zone valve (on the tank without a thermostat) in an attempt to get to
the desired temperature. As a result, the system was almost continuously calling for heat from
the boilers, and the domestic hot water was being delivered at 130° F. With only one tank
receiving heat, at higher DHW demand flows, the temperature could drop below the normal
setpoint of 110 120° F. The Tekmar controller has a capability to shut down the boilers and
circulating pumps during warmer weather, but is overridden by the nearly continual demand
from the domestic hot water system. Suggestions to correct the inoperable zone valve were
provided to the onsite building maintenance manager during the site visit.
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ADEQUACY OF EXISTING SPACE HEATING EQUIPMENT
Existing baseboard terminal units were sized for the original construction, with an output of
approximately 850 BTUH/FT with 180° F heating water. With a lower temperature heating water
(150° F provided by the heat pumps), the output would be reduced to approximately 560
BTUH/FT, or 66 percent of original capacity. Unit heaters are also similarly affected by reduced
heating water supply temperature, but because they are fan-forced heaters, the effect is
lessened. Since the building has been upgraded by a weatherization project including addition
of 1-1/2 inches of R-Max foam wall insulation, additional ceiling insulation, and replacement
windows, all of which reduce the heat losses, the existing terminal units should provide
adequate comfort heat for the building if the hydronic loop temperature is adjusted relative to
outdoor air temperature.
The existing copper hydronic distribution loops that extend from the mechanical room to
terminal units throughout the building are in good shape, and will continue to deliver heat
adequately at the lower temperatures expected (130F thru 160F).
According to on site staff, since the time of weatherization, the building has been overheating in
the winter and residents have been opening windows to cool apartments. This is due in part to
the increase in wall insulation, new thermal window units, and increased ceiling insulation. Part
of this is due to the fact that the unit heaters in hallways are overheating the halls and the warm
air is drawn into apartments when residents run their exhaust fans. The ability of the
baseboards and unit heaters to keep residents comfortable is also dependent on other
variables:
Frequency that residents run their kitchen and bathroom exhaust fans and remove warm
air from their apartments.
The amount of mechanical ventilation that is exhausting warm air from the hallways.
Whether doors to the exterior are partly open in the hallways, causing a loss of warm
from the building.
Amount of open window area that residents have at the time.
The outdoor air temperature, humidity, and wind conditions.
Whether the resident is setting their individual thermostat properly in the apartment.
Similar projects in southcentral Alaska have shown that increased envelope insulation will
reduce the heat load in apartments, and that lower temperature hydronic water can be used to
maintain comfort if other factors are also managed properly. The baseboard water temperature
will be controlled by an outdoor temperature reset program at the buffer tank. At any given time,
comfort in the apartments can be maintained by modulating the buffer tank temperature up or
down between 120F and 180F. Over the year, it is anticipated that the heat pumps delivering
up to 150F will cover 55% to 75% of the heat load, with the remainder covered by the oil boiler.
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ADEQUACY OF EXISTING DOMESTIC HOT WATER HEATING EQUIPMENT
The two existing Amtrol 80 gallon indirect hot water heater tanks are nearing the useful end of
life, and will soon be replaced with SuperStore Pro SSP-80 units under the CIHA building
maintenance budget. These new tanks have high recovery rate coils to allow the lower
temperature range (130F thru 160F) of the new buffer tank to be more effective. Installing a 2.5
ton heat pump dedicated to the DHW tanks would allow replacement indirect hot water tanks to
operate with fewer occasions for assistance from the oil boiler, and little need to draw heat away
from space heating. The option for the additional DHW heat pump is included in the Final
Design Documents as an additive alternative, and is recommended if available budgets allow for
the installation.
NEW MECHANICAL SYSTEM CONFIGURATION WITH HEAT PUMP INTEGRATION
The two boilers are the same size and model. One is older than the other. The oldest should be
removed and kept as a spare in case of problems with the active boiler. Two new heat pumps,
each with 84,000 BTU/hour capacity (7 tons) will be installed to effectively replace the one oil
boiler removed. These heat pumps will operate with output temperatures ranging from 120F to
150F and associated COP ranging from 3.5 down to 2.5.
If available budget will allow, an additional smaller heat pump will be installed to maintain
domestic hot water temperatures at a minimum of 120F during normal demands. This heat
pump will be 2.5 ton capacity (30,000 BTU/hour) to provide a recovery similar to two 4,500 watt
immersion element heaters. This dedicated DHW heat pump will be connected to the ground
loop source in parallel to two larger heat pumps dedicated to space heating.
A 240 gallon buffer tank will be installed, located in the mechanical room, or in the crawl space
opposite the boiler room wall, with piping inputs from the heat sources and outputs to building
heating and separate domestic water heating. Input side heat source connections will be located
at differing elevations to take advantage of temperature stratification within the tank. Lower
temperature sources (heat pumps) will input at a lower elevation than the boiler input, and the
return to the boiler will be located higher than the return to the heat pumps to assist with boiler
thermal shock protection. Each heat source will have its own circulating pump, and the pumps
will be controlled in sequence with the heat pumps staged on before the boiler. Temperature in
the tank will be maintained by an outdoor temperature reset controller that will reduce the tank
temperature as outdoor temperature increases, which should reduce the boiler firing
requirement to colder outside temperature and to assist with domestic hot water generation.
Outputs from the buffer tank will also have separate circulation pumps, allowing the building
heating and domestic water heating to be independently controlled and prevent the domestic
water heating demand from affecting the building heating. The building heating pumps will be
capable of shutting down completely in warm weather (above 65F), reducing overheating of the
building common spaces.
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Heating terminals (cabinet unit heaters and unit heaters) could be upgraded to add zone valves
for better control (that feature was shown on the 2007 upgrade project drawing set for two new
cabinet unit heaters on the first floor, but was apparently not implemented for others.) With zone
valves on all terminal units, pressure controlled variable speed circulation pumps would provide
additional energy savings when few terminal units were calling for heat by slowing down to
maintain only minimum required pressure for the reduced flow.
A Project Schematic that illustrates the proposed heat pump integration is included in the
Drawings on sheet G-2, and specific piping details are shown on Sheet M-2.
ESTIMATE OF ANNUAL AND HOURLY HEATING DEMAND
Using both AKWarm software and GeoLink software from Water Furnace, rough estimates of
both peak hourly and annual heating loads for the building were estimated. It should be noted
that a detailed commercial level energy audit of the facility has not been performed within the
scope of these service. From the modeling, a peak hourly space heating winter design load of
300,000 BTU/hour is estimated, and an annual space heating demand of 750 MMBTU is
estimated.
The domestic hot water demand is roughly estimated to be 18 persons x 20 gal/per/day, with a
temperature increase from 40F to 125F. This equates to an annual hot water heating demand
of 93 MMBTU. Thus the total annual heat demand of the building is estimated to be 843
MMBTU (750 MMBTU + 93 MMBTU) with 89% of this annual demand being space heating
and 11% being domestic hot water heating.
The actual annual fuel usage in the heating season (July to June) of 2011/12, 2012/13 and
2013/14 has averaged 10,000 gallons of year which is equivalent to 1,126 MMBTU/year at 84%
boiler efficiency. The actual fuel usage is higher than the model predictions most likely due to
factors that include residents leaving windows open and ventilation rates being higher than
model predictions.
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EXISTING ELECTRICAL SYSTEM DESCRIPTION
The building has a 600A, 240/120V, single-phase, 3-wire electrical service that is served
underground from a pad-mount, 50kVA Homer Electric Association transformer #11951. The
service equipment is mounted on the north end of the building and consists of a 600A main
fused disconnect switch and a bank of twenty (20) meter/main devices. There are sixteen 70A
rated and two 100A rated meter/mains for the 18 tenant apartments. There is one 200A rated
meter/main for the common areas and one blank meter space.
The 200A met -feeds
-fed through a
260A, 240V, 2-pole, single-phase, automatic transfer switch, ASCO Cat. #J07ATSA20260F50C.
It serves the facilities critical loads and is provided with standby power from a 35kVA, 240/120V,
n hallway on the opposite side of the wall
-
the first floor.
EXISTING GENERATOR CAPACITY
The existing generator is 35kVA, 146A rated, but it is currently limited by a 100A, 2-pole circuit
breaker on its output. This effectively limits the generator capacity to 24.0kVA. The RSA
generator of 29.6 kVA and a demand load of 24.1kVA. These drawings do not include
additional circuits that were added to circuits #2, 26, 28, 30 & 32. Circuit #30,32 is a two-pole,
50A circuit. Circuits #26, 28, 30 & 32 were not identified on the panel schedule.
Each of the proposed new heat pumps include two compressors each with 23.7A full load
ampere ratings at 230V. One heat pump adds 23.7 x 230 x 2 = 10.9kVA of demand load.
Adding this to the current generator demand load of 24.1kVA gives 35kVA of total demand load.
This does not take into account the demand load of the un-identified circuits that were added or
capacity to support the new heat pumps without removing other critical loads. One possibility is
to remove the kitchen range and/or oven loads from standby generator if the heat pumps are
deemed more critical.
ELECTRICAL SERVICE CAPACITY
There is no demand metering on the existing building so the demand load for the building is
estimated as follows:
Lighting Load: 17,000 sq-ft x 3VA = 51.0kVA
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Small Appliance Circuit Load: 2/unit x 18units x 1.5kVA = 54.0kVA
Laundry Circuit Load: 1/unit x 18 units x 1.5 kVA = 27.0kVA
Subtotal = 132.0kVA
Demand Factor: First 3kVA @ 100% = 3.0kVA
3-120kVA @ 35% = 40.9kVA
120-132kVA @ 25% = 3.0kVA
Subtotal A = 46.9kVA
Dryer Load: Assume 5kW/unit x 18 units = 90.0kVA
40% demand factor (NEC Table 220.54) x 0.40
Subtotal B = 36.0kVA
Range Loads: Assume 5kW/unit x 18 units = 90.0kVA
28% demand factor (NEC Table 220.55 Column B) x 0.28
Subtotal C = 25.2 kVA
House Loads: From RSA record drawing E0.1 dated 04/23/07 = 20.4kVA
Subtotal D = 20.4kVA
Additional Heat Pump Loads:
Two heat pumps w/ 2ea compressors 2 x 2 x 23.7A x 230V = 21.8kVA
Boiler circulation pump, assume 1Hp 8A x 230V = 1.8kVA
Source/load circ pumps, assume 1Hp ea 4 x 8A x 230V = 7.2kVA
Water heater circ pump, assume 1/2HP 9.8A x 115V = 1.1kVA
Remove one boiler 1/2HP 9.8A x 115V = -1.1kVA
Subtotal E = 30.8kVA
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Total Service Demand Load: A+B+C+D+E = 159.3kVA
159.3kVA = 663.7amps @ 240V
Therefore, service size of 600A is exceeded with the new heat pump demand loads.
ELECTRICAL DESIGN CONCEPT
Based on the preliminary design calculations a new electrical service will be installed that is
dedicated to the heat pump system. The service would be 200A, 240/120V single-phase and
would include a new meter/main adjacent to the existing service equipment. It is assumed at
this point that any upgrades to the HEA pad-mount transformer that are required will be
provided by HEA at no cost.
A new panelboard will be installed to serve the new loads. Since the existing mechanical room
is very crowded, the new panelboard is proposed to be located in the storage room on the
opposite side of the south mechanical room wall. The heat pumps would not be provided with
generator standby power, but the one remaining boiler will remain on standby power.
Various instruments will be installed to help monitor and assess the performance of the heat
pump system. At a minimum, the following instruments will be provided:
Heat pump load side - flow transmitter, temperature transmitter (supply & return).
Buffer tank temperature transmitter
Electric powermeter
It is intended that the various instruments will be connected to a data collector that has a web
based server function so that the system parameters can be monitored via the internet. A
hardwired Cat 6 Ethernet connection will be provided between the data collector and the
existing network switch in the Seldovia House manager s office.
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GROUND SOURCE HEAT PUMP SYSTEM EVALUATION OVERVIEW
Opportunity exists at the Seldovia House site for using the existing soil and rock mass below the
parking area as a year round heat source for space heating. It was determined in the
September 2013 YCE Evaluation that vertical wells under the parking area were a viable option
for ground source heat pumps.
Ground Source Heat Pump Design Fundamentals A ground source heat pump system
creates hot water (@42F) heat energy that is
stored in the earth. A series of HDPE pipe loops that circulate thru the soil and /or rock mass in
a vertical arrangement transfer heat from the earth into a methanol/water mixture that is piped to
the source side of the heat pumps. The size of the soil/rock mass intercepted, and the soil/rock
heat conductivity determines how much heat can be extracted from the ground loops each
month of the year. On the load side of the heat pump, hot water is used for both space heating
and for domestic hot water heating. The heat pump system will operate in parallel with one of
the existing conventional heating oil boilers; the other boiler will be removed. The heat pump
system will heat a buffer tank of water
system. Over the year the heating oil savings become more significant than the electrical
energy used by the heat pump and this difference can make the system cost effective.
Sizing Of Ground Source Loops, Heat Pump, And Buffer Tank - The minimum target for the
ground source heat pump system to achieve is at least 75% of the buildings projected annual
heating load. The optimal size heat pump to achieve that performance is one that is 14 tons
capacity. Two units of 7 tons capacity are recommended for redundancy. For the purpose of
this evaluation, the heat pump recommended is Water Furnace NHW Series 7 Ton unit (or
equal); this unit is high efficiency and can lift from 120F to 150F on the load side, using ground
loop temperatures on the source side. The average efficiency of the unit for the project
conditions is estimated to be a COP of 2.69. The heat pumps will work to keep a 240 gallon
buffer tank at a temperature ranging from 120F to 150F as its volume is circulated thru the
building hydronic system. When outdoor air temperatures force heating load greater than heat
pump capacity, the one oil boiler will fire to supplement as required.
The ground source loops are designed to provide the optimal heat transfer from the earth into
HDPE buried horizontal loops or vertical loops in deep wells. The limiting factor for vertical
wells is their proximity to existing surface structures/features and to each other; a minimum of
ten foot spacing between vertical wells is recommended.
The best strategy for success with buried HDPE ground source loops is to locate them in high
conductivity wet soils or in bedrock. Groundwater has twice the heat capacity of rock or soil and
if there is ground water migration thru the loop field, this can ensure that the target heat capacity
is met year when that groundwater is present. Conversely, a soil matrix with high clay content
that is relatively dry can provide poor conductivity of heat in to the HDPE ground loops.
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Existing Subsurface Geology - The State of Alaska Department of Natural Resources
maintains a database of well logs that were submitted for water rights. 58 water wells have
been drilled in Seldovia, but most of them are in geologically dissimilar areas, and do not
provide much guidance for what might be found at Seldovia House. The USGS geological map
of Seldovia shows that the geology in the vicinity of Seldovia House is dominated by basalt and
cherts--potentially metamorphosed. The beds of these units dip to the west at 80 degrees.
What this means is that because the beds are so steeply dipped, the well logs of one well that is
either to the east or west of the site by even a short distance may encounter entirely different
rock units.
The closest well found in the data base was approximately 1/2 mile to the west. It encountered
bedrock at 8 feet, similar to at Seldovia House, and then entered a wet rock unit for 20 feet.
The static water level was at 8 feet, and the temperature in October 1985 was 39F. No more
notes are made of if the drilling encountered water further down or not. No notes were made of
fractured rock--only hard or soft rock. This does not mean that water was not found or that
fractured zones were not found, only that no notes were made. Further to the west, the
sediment gets progressively thicker and gives little indication of what would be found on site.
Anticipated Permitting For GSHP Vertical Wells - The State Of Alaska Department Of
Natural Resources (DNR) public information center advised YCE that a permits is needed for
vertical wells only if the owner is staking a water right. As the GSHP will not be extracting water
from the ground, no water right is needed.
The State of Alaska Department Of Environment & Conservation - Division of Water--Permitting
Department Groundwater c/o Charlie Palmer, advised YCE that no permits would be required
for a GSHP project, as no agency has statutory authority. He did supply some
recommendations for projects.
1. A survey for public water systems should be conducted, as projects should not be within 200
feet of a public water system. (Seldovia receives its water from a lake above town).
2. He suggested that propylene glycol be used instead of ethylene glycol--he did say that
methanol-based antifreeze (like Environol) would be okay.
3. Wells should adhere to ANSI AWWA A100-97 Appendix H, sect. 4.10 for cementing.
4. A driller certified by the National Groundwater Association and IGSHPA should be chosen.
5. Bentonite grout should be inserted from the bottom of the well under pressure and put in
place as the casing is removed so that aren't any voids in the grout.
6. A leak detection system should be put in place--he recommended a pressure gauge or some
other relatively simple method.
7. At least 2" of bentonite should be around the piping to isolate any potential fluid leaks in the
pipe.
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VERTICAL WELL GROUND LOOPS PRELIMINARY DESIGN
The parking area for Seldovia House has adequate open space for a vertical rotary percussion
drilling rig to set up and install a field of up to ten
There are several contractors in Alaska who can mobilize to Seldovia and drill vertical
geothermal wells. According to test boring logs taken at the site in 1978, bedrock is estimated to
be between 5ft and 20ft below the ground surface; the bedrock is tilting steeply to the north.
The parking area has a number of existing features that restrict the location of both vertical
wells, and manifold trenching. A row of large spruce trees on the adjacent property have roots
in the ground and canopy overhead that can interfere with construction. An existing sewer
lateral crosses under the center of the parking area. An existing concrete loading pad is in front
of the building. Vertical wells must be kept a safe distance from the building and the property
line.
A layout of the vertical well field that accommodates the various restrictions is provided in the
Drawings on Sheet G-3.
PROJECT ECONOMIC EVALUATION
tical well will yield an estimated energy gain of 1.4 tons
(16,800 BTU/hour) of heat pump capacity, thus the total energy gain for the ten wells will be 14
tons (168,000 BTU/hour). The proposed 2.5 ton domestic hot water heat pump will produce up
to 30,000 BTU/hour. The current annual fuel usage is an average of 10,000 gallons/year which
is equivalent to 1,126 MMBTU/year at 84% boiler efficiency. With an annual average heat pump
capacity factor of 50%, the total annual heat pump output will be 844 MMBTU, or 75% of the
total annual heating load (space + DHW) for the building. This is equivalent to approximately
7,500 gallons of heating oil displaced per year. Given the variables that may affect the actual
heat load, it is estimated that fuel savings may range from 5,500 gallons/year to 7,500
gallons/year.
At the current price of $5.34/gal this is a savings of heating oil cost of $40,000 per year.
The payback on this system is driven by the projected escalation of heating oil price that is
typically taken to be a minimum 6% per year.
The estimated budget cost of the installed vertical well ground source heat pump system is
$243,220 including 10 wells, HDPE ground piping and manifold, copper piping inside
mechanical room, pipe insulation, two 7 ton heat pumps, 240 gallon buffer tank, and basic
controls. The total installed cost of the project, including materials shipping, engineering,
and contingency is estimated to be $362,805. The Net Present Worth payback of the
proposed vertical well ground source heat pump system is estimated to be 11.2 years.
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VERTICAL WELL GROUND LOOPS OPINION OF PROBABLE COST
SELDOVIA HOUSE - VERTICAL WELL GSHP SYSTEM - OPINION OF PROBABLE COST - DESIGN MEMO
System Sizing = 75% of Annual Space HeaƟng Load
by: A. Baker, PE YourCleanEnergy LLC 8/28/14
Installed Installed
Item DescripƟon QuanƟty Unit Unit Cost Total Cost
Drilling Contractor Mobilization 1 LS $14,100 $14,100
Drill 6" dia x 300 ft deep vertical wells (10 total)3000 Lin ft $30 $90,000
Install and grout 1" Dia HDPE Ground Loop Piping 6500 lin ft $2 $13,000
3ft wide x 6 ft deep trench, excavate & backfill 120 lin ft $80 $9,600
2" Dia Reverse Return HDPE Send & Return Manifold 200 lin ft $22 $4,400
Compact & Restore Gravel Pkg Area (96'x36')80 sq yd $40 $3,200
2" HDPE Send & Return Piping (Manifold to HP)210 lin ft $22 $4,620
Mechanical Contractor Mob/Demob 1 LS $4,000 $4,000
Remove existing boiler & Amtrol tanks 1 LS $2,000 $2,000
Hi Efficiency W/W Heat Pump (7 Ton)2 each $12,000 $24,000
240 gallon insulated buffer tank 1 each $6,000 $6,000
Loop Pump & Controls (Source)2 each $1,200 $2,400
Loop Pump & Controls (Load Side)2 each $3,000 $6,000
Piping, Valves, Pipe Insulation In Mech Room 1 LS $12,000 $12,000
Labor For Mechanical Installation 1 LS $8,000 $8,000
200 Amp Electrical Service, Panel & Wiring 1 LS $24,500 $24,500
Instrumentation & Monitoring Equipment 1 LS $15,400 $15,400
Total For Equipment & InstallaƟon $243,220
Engineering Design of Heat Pump System (16%)0.162 $39,402
Construction Inspection By Engineer (3%)0.03 $7,297
Construction Contingency (10%)0.1 $24,322
CIHA PM & Admin (20%) - In Kind Match 0.2 $48,644
Total Installed Cost $362,884
Add Alt - Dedicated HP For DHW
Hi Efficiency W/W Heat Pump (2.5 Ton)1 each $6,000 $6,000
Loop Pump & Controls (Source)1 each $1,200 $1,200
Loop Pump & Controls (Load Side)1 each $3,000 $3,000
Misc Piping & Installation Labor 1 each $3,000 $3,000
Electrical & Controls 1 LS $3,000 $3,000
$16,200