HomeMy WebLinkAboutschematic narrative and drawingAlaska Energy Engineering LLC
25200 Amalga Harbor Road Tel/Fax: 907.789.1226
Juneau, Alaska 99801 alaskaenergy@earthlink.net
SCHEMATIC NARRATIVE
for
Haines Assisted Living Facility
Ground Source Heat Pump System
1.1 INTRODUCTION
A. The following narrative provides a conceptual description of a ground source heat pump
system for the Haines Assisted Living Facility in Haines, Alaska. The narrative is an
attachment to an Alaska Energy Authority grant application. Items specific to Section 4.3.1 of
the grant application can be found in the following locations:
1. A description of renewable energy technology specific to project location: Section 1.3.
2. Optimum installed capacity: Section 1.4A and Section 1.5B.
3. Anticipated capacity factor: Not applicable
4. Anticipated annual generation: Not applicable.
5. Anticipated barriers: None
6. Basic integration concept: Entire narrative.
7. Delivery methods: Section 1.4.
B. A schematic diagram of the proposed ground source heat pump system is attached.
1.2 DESCRIPTION
A. System: The Haines Assisted Living will consist of two similar buildings. The heating system
for each building 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 produce hydronic heating water and
domestic hot water.
B. Performance: The system will supply heat at a coefficient of performance (COP) of 2.1. For
every kWh of purchased energy consumed for the heat pump compressors and system pumps,
2.1 kWh of heat is supplied to the building.
1.3 GEOTHERMAL GROUND COUPLING
A. Description: The ground couple will consist of closed-loop vertical well field and field piping
connecting the wells with the two buildings.
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B. Wells: The well field will consist of 142 wells, each 6” in diameter and 125’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 thermo conductive grout.
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.
C. Well Field Piping: Field piping will consist of six insulated HDPE pipe loops, three for each
building, 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 between the
two buildings. All piping will be a minimum of 18” below the surface. The surface will be
paved and landscaped for resident use.
1.4 GROUND SOURCE PUMPING SYSTEM
A. Description: Each building will have ground loop pumps that circulate water between the well
field and the heat pumps located within the building. The well field is sized for 100% of the
heating load and 50% of the domestic hot water load. During periods of really cold weather
when the well field load is maximized, the electric hot water heater will provide supplemental
domestic hot water heat if needed. This sizing is optimal for the facility as it significantly
decreases the construction costs the well field size will shifting only 6% of the heating load to
supplemental electric heat.
B. Building Piping: The well field pipe loops will be manifolded together within the building and
connected to the heating and domestic water heat pumps. Piping within the building will be
insulated HDPE piping. The piping will be filled with an antifreeze solution to prevent
freezing.
C. Loop Pumps: Each building will have two variable speed loop pumps that circulate ground
source water through the heat pumps. The pumps will variable speed for energy efficiency and
sized for 100% redundancy.
1.5 HEAT PUMPS
A. Description: Water-to-water heat pumps will produce hydronic heating water and domestic ho
water in each building.
B. Water-to-Water Heat Pumps
1. Heating System: Each building will have two water-to-water heat pumps that produce
hydronic heating water. The heat pumps are sized at 75% of the design load so that one
may carry the load if the other is down for maintenance. The heating water will be stored in
an heating water storage tank. The tank will have electric heating coils that will provide
backup heat when the heat pumps require maintenance. The hydronic heating water will
supply an in-floor radiant heating system and heating coils in the ventilation and makeup
air units.
2. Domestic Hot Water: Each building will have a water-to-water heat pump that produces
domestic hot water. The heat pump is optimally to supply the peak hot water demand. The
hot water will be storage in an electric hot water heater that will provide supplemental hot
water heating during cold weather when the well field is at maximum output.
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1.6 VENTILATION
A. Each building will be ventilated by a heat recovery ventilator that supplies the occupied spaces
and draws exhaust air from toilets, janitor closets, laundry, and the kitchen. The kitchen will
have a make-up air fan and exhaust fan serving the kitchen hood.
1.7 EQUIPMENT SCHEDULE
A. The following table provides a schedule of the equipment required for the GSHP system.
Ground Source Heating System Equipment Schedule
Equipment Capacity
Well field 142 wells spaced on 12’ center
Each well 125’ deep and 6” diameter
¾” HDPE closed pipe loop in each well
Well field piping Three loops of insulated HDPE piping per building
Ground source pumps (4) 175 gpm @ 77’ head, 7.5 HP, variable speed
Water-to-water heat pump (4) 210 MBH, 30°F EWT, 3 gpm/ton
Load pumps (4) 35 gpm @ 35’ head, 3/4 HP
Heating storage tank 200 gallons, stainless steel
Building pumps (4) 20 gpm @ 40’ head, 1/2 HP
Domestic hot water heat pump (2) 120 MBH, 30°F EWT, 3 gpm/ton
DHW pumps (2) 35 gpm @ 20’ head, 1/2 HP
Hot water storage tank (4) 120 gallons electric hot water heater