HomeMy WebLinkAboutJuneau Airport Ground Source Heat Pump Project Concept Specification - Feb 2008 - REF Grant 2195359Alaska Energy Engineering LLC
25200 Amalga Harbor Road Tel/Fax: 907.789.1226
Juneau, Alaska 99801 alaskaenergy@earthlink.net
SPECIFICATION
for
Juneau Airport Terminal Ground Source Heat Pump System
1.1 DESCRIPTION
A. System: The heating, ventilating, and air-conditioning system for the Airport Terminal will be
a ground source heat pump system (GSHP). The system will consist of a closed-loop vertical
well field, a ground loop pumping system that moves heat between the ground and the
building, and water-source heat pumps that condition the spaces within the building and supply
domestic hot water.
B. Performance: The system will supply heat at a coefficient of performance (COP) of 2.6. For
every kWh of purchased energy consumed by the heat pump compressors, 2.6 kWh of heat is
supplied to the building. The well field has a high water table and steady water flow that makes
it ideally suited for long-term heat extraction.
1.2 GEOTHERMAL GROUNDCOUPLING
A. Description: The ground couple will consist of closed-loop vertical well field and field piping
connecting the wells with the building.
B. Wells: The well field will consist of 215 wells, each 6” in diameter and 175’deep. The wells
will be cased during drilling and the casing removed during backfill operations. A ¾” HDPE
pipe loop will be placed in each well and the well backfilled with native material. Each well
loop will be pressure tested prior to backfilling. Direct ground water contact with the pipe loop
will provide very good thermal conductivity between the ground source fluid and the ground.
1. Test Well: A test well was drilled at the site in November, 2007 and the data gained will
form the basis for competitively bidding the work. While a temporary water use permit was
obtained from the Department of Natural Resources for the test well, the closed loop
system will not require permits.
C. Well Field Piping: Field piping will consist of three insulated HDPE pipe loops, each
connected to an equal number of wells. Each branch will connect to a pair of wells in series.
The piping will be laid in trenches and pressure tested prior to backfilling.
D. Site Excavation and Restoration: The well field and field piping will be installed beneath the
Commuter / Air Taxi Parking Area. The existing pavement will be removed prior to excavating
pipe trenches and drilling wells. All piping will be a minimum of 18” below the surface. Sub-
base and new paving will be installed upon completion of the field piping.
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1.3 GROUND SOURCE PUMPING SYSTEM
A. Description: Ground source pumps will circulate water between the well field and the heat
pumps located within the building.
B. Building Piping: The field piping loops will be manifolded together within the building and
connected to the building distribution piping. Piping within the building will be insulated
HDPE piping. The piping will be filled with an antifreeze solution to prevent freezing.
C. Loop Pumps: Three variable speed loop pumps will be used to provide redundancy and so the
pump capacity more closely matches the flow requirements at partial loads. Each pump will be
variable speed with the flow rate controlled by a differential pressure sensor in the building
loop.
1.4 HEAT PUMPS
A. Description: The building will be primarily heated with water-to-air heat pumps. Water-to-
water heat pumps will be used for radiant in-floor heating and for domestic hot water heating.
B. Water-to-air Heat Pumps: The building will have 61 thermal zones, each served by a water-to-
air heat pump. Each heat pump contains a fan that circulates and conditions room air as needed.
When heat or cooling is required, the heat pump compressor unit exchanges heat with the
ground source piping and transfers it with the room air stream. The heat pumps will be capable
of both heat and cooling.
1. A backup electric resistance heating coil will be installed in heat pumps located in critical
spaces to ensure heat if the compressor requires maintenance.
2. Heat pump compressors are typically on-off devices. In spaces where thermal comfort is
more critical—offices, dining, etc.—variable speed compressor will be provided to
minimize temperature fluctuations.
C. Water-to-water Heat Pumps
1. Domestic Hot Water: Two water-to-water heat pumps will produce domestic hot water for
the facility. The heat pumps will maintain a hot water storage tank at 120 F.
2. Radiant In-floor Heating System: A water-to-water heat pump will supply heating water
for in-floor radiant heat in the baggage claim lobby and high-use exterior walkway.
1.5 VENTILATION
A. A dedicated outdoor air system (DOAS) will supply code required outdoor air to each heat
pump. The DOAS will be variable air volume with the supply to each room modulated to
match actual occupancy. This system will significantly reduce ventilation air flow in the highly
variable occupancy terminal. The DOAS will have a heat recovery cell to exchange heat from
the building exhaust air to temper the outside air. The unit will also have a water-to-air heat
pump to bring the air temperature up to building temperature.
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1.6 EQUIPMENT SCHEDULE
A. The following table provides a schedule of the equipment required for the GSHP system.
Equipment Schedule
Equipment Capacity
Well field 215 wells spaced on 10’ center
Each well 175’ deep and 6” diameter
¾” HDPE closed pipe loop in each well
Well field piping Three loops of insulated HDPE piping
Ground source pumps (3) 225 gpm @ 150’ head, 15 HP, variable speed
Water-to-air heat pumps (61) 6 MBH (2); 12 MBH (26); 18 MBH (7); 24 MBH (2);
30 F EWT, 3 gpm/ton 30 MBH (14); 36 MBH (5); 60 MBH (2) ; 72 MBH (1) ;
150 MBH (2)
Water-to-water heat pump (1) 120 MBH, 30 F EWT, 3 gpm/ton
Domestic hot water heat pump (2) 120 MBH, 30 F EWT, 3 gpm/ton
Hot water storage tank 300 gallons
Dedicated outdoor air system Commercial terminal: 7,000 cfm water-to-air heat pump
with heat recovery cell; variable air volume
Commuter terminal: 3,000 cfm water-to-air heat pump
with heat recovery cell; variable air volume