Ground Source Heat Pump Systems Case Studies
5th Town Cheese plant maintains balance
5th Town Cheese plant maintains balance
The heat pump design at 5th Town Cheese in Picton, Prince Edward County on Lake Ontario, takes advantage of the fact that the plant needs both heating and cooling year round, either for the building or cheese making. Energy use in Canadian residential buildings is dominated by their heating requirements. They require a net extraction of heat from the ground heat exchanger (GHX) field, which results in the field’s long term cooling. But in a commercial or industrial application where significant heat is rejected from the building or process, that rejected heat can help maintain the temperature of the GHX field over the long term.
The 5th Town Cheese plant is designed to process 3,000 kilograms of cheese per day, requiring about 2,000 litres of hot domestic water per day for washing the equipment, milk piping and tanks.
At the same time, the water-cooled refrigeration equipment for walk-in coolers and refrigerated display cases rejects about 10 kW of heat, which can be used to heat water.
The water-to-water-to-ground heat pump system is based on a nominal 12-Ton IceKube heat pump from Manitoba. Its cooling capacity is 34 kW at 7C chilled water temperature; its heating capacity is 41 kW at 43C. The heat pump simultaneously feeds the heating water piping and chilled water piping, each with a 450-L thermal storage and buffer tank.
The building is heated and cooled with radiant concrete slabs and hydronic fan coils, using water mixed to the appropriate temperature in the mechanical room and distributed in a two-pipe configuration. The 350-m2 building is extremely energy efficient and needs only 20 kW of space heating and 10 kW (2.7 T) of cooling.
Fresh from the cheese making room, cheese rounds are moved down a tunnel into two underground concrete aging caves, controlled at about 12-15C and 90% relative humidity. Space temperatures are maintained by radiant tubing cast into the cave floors and walls, and humidity is controlled with chilled water coils and ventilation.
When the total requirements for heat in the system match the cooling needs, the heat pump can simply transfer the energy from one load to the other. When there is a difference in load, the heat pump extracts or rejects the balance of the heat to the 380-m2 ground heat exchanger, a horizontal slinky field (see above) which is set directly on the limestone bedrock and backfilled to 2-m depth.
Thermal connectivity was enhanced by bedding the GHX tubing in lean concrete directly on the washed surface of the rock. The horizontal GHX is a closely-spaced grid of 20-mm diameter polyethylene tubing arranged in 1-m diameter overlapping loops, sized with commercially available software. Although there are few GHX slinky fields in Canada, Enermodal has found them to be a practical alternative to vertical boreholes, especially in bedrock geology.
The 5th Town system has been operating since summer 2008. This spring the plant and retail outlet was the first industrial building to achieve LEED Platinum certification.
Mechanical, electrical, geothermal design, LEED energy andcommissioning: Enermodal Engineering (Richard Lay, P. Eng.,Tim Dietrich, P. Eng.). Architect: Francis Lapointe. Contractors: Peter Knudsen construction, Adams Plumbing
Savings At Sisters Of St. Joseph
Chorley & Bisset/Caneta Research
The Sisters of St Joseph New Residence in London, Ontario, is a four-storey, 12,000-m2 nursing and rest home completed in 2007. The building uses a closed loop geothermal system for nearly all of its heating and cooling needs. It achieved a LEED Gold rating, with energy consumption predicted to be 46% better than a building matching to the Model National Energy Code for Buildings.
The geothermal system absorbs energy from the ground, which is then used to provide space heating and cooling for the building, as well as heating for the central ventilation air systems. During the cooling season, the system rejects energy to the ground from these systems. The geothermal field consists of 63, 90-m deep boreholes, each with a 150-mm diameter steel casing, high performance grout and a 25-mm polyethylene tubing loop. A pair of circulating pumps move water through the field and back to the building.
A second pair of pumps circulates water through an indoor piping loop that supplies water-to-air heat pumps for space heating and cooling, and water-to-water heat pumps that generate heating and cooling water for the ventilation systems. The two loops are connected together in a primary/ secondary arrangement, which allows the use of a different flow rate for each loop.
Pump energy was reduced by adding on/off control valves to the heat pumps and variable frequency drives to the indoor pumps.
To date, no additional heating energy from the boiler plant has been required to back up the geothermal system. Extensive monitoring over two years has shown the building has used significantly less energy than predicted by the energy models.
Mechanical/electrical design: Chorley & Bisset (Derek B. Vakarus,P. Eng., Greg Cygalski, P. Eng.); Geothermal borefield design:Caneta Research. Architect: Cornerstone.
Hybrid Geothermal-Solar System For B. C. Winery
Bains Leslie Engineering
At the Burrowing Owl Estate Winery in Oliver, located in B. C.’s southern Okanagan Valley, a ground source heat pump system is combined with a solar energy system. It serves a shop, restaurant, 11-room guest house and a swimming pool in a recent addition to the main winery. The hybrid system supplies space heating and cooling, and domestic hot water. It also supplies 90C temperature water for cleaning the wine casks in the underground cellars.
In this desert climate, the solar array collects plenty of excess heat during the hot summers. The heat is stored in a ground loop both short-term for use at night, and long-term
for use in the winter. The ground loop has 30 holes drilled 60m deep, while the solar array consists of 30 collectors feeding eight water tanks with a total capacity of 3,600 litres.
A Sonja SR-20 computerized solar control system orchestrates the whole system, sending hot and cold water between the tanks to supply different needs around the building.
The system allows the new annex to be almost self sufficient in terms of heating energy.
Mechanical-electrical engineers: Bains Leslie Engineering. Solarcollector system: Swiss Solar Tech. Geothermal system: GeoTility.
Seawater District Cooling In Dartmouth
High Performance Energy Systems
On the Dartmouth side of Halifax Harbour, one of the first projects in the world to combine direct cooling using seawater with underground thermal energy storage is being completed.
The project provides air-conditioning to a complex of five buildings known as Alderney Gate. The buildings amount to 36,650 sq. ft., and include a theatre, government offices and a ferry terminal. In early April, engineers said they were making final adjustments to the systems’ controls.
For most of the year the buildings will be cooled directly using seawater pumped from the harbour. The water is pumped through an underground titanium heat exchanger or “GeoEnergy Vault,” and the cold energy is transferred to a separate fresh water loop for distribution into a district piping system.
From late August to October, however, the ocean water is not cold enough to provide the building’s air-conditioning. As a solution, High Performance Energy Systems designed a borehole field that stores cold energy during the winter months for use during the summer.
The Advanced Coaxial Energy Storage system consists of 120 boreholes drilled 300 metres deep below a parking lot. The boreholes are 11
5 mm in diameter with an inner sealed plastic tube and an outer casing of steel. The de-sign is said to be 300% more efficient than traditional U-tube boreholes.
Speedy Installation At Wal-Mart
Below the parking lot of the Wal-Mart store that opened in Burlington, Ontario this January lies 15 kilometres of piping as part of an innovative closed loop geothermal heating and cooling system.
Wal-Mart is “committed to being green,” and intends to roll out prototypical stores that are 30% more energy efficient than the norm. Besides the geothermal system, the Burlington store’s energy saving features include capturing heat from the refrigerators to heat the store, LED lighting, daylighting, and a white reflective roof.
Nuno Duarte, P. Eng. of Stantec explains that the geothermal piping was laid using a “Spider Plow,” which furrows the pipe into the ground and saves excavating. The pipe was laid over six days, creating a horizontal field on two levels at 2.3 m and 1.7 m. The Spider Plow had to be transported from Calgary, but the saving in excavation time offset this cost. Until now the plows have mostly been used for laying gas lines and other utilities.
Inside the 10,220-m2 space, Duarte explains, the system includes modular chillers, where the reversing cycle between heating and cooling occurs via the water piping system rather than using heat pumps to reverse the refrigeration cycle internally.
A “roll-out radiant mat” was used for the hydronic floor heating and cooling system. The mats incorporate PEX compression fittings, isolated to the fused pipe headers. They are rolled out in 10-ft. x 200-ft. (3 m x 61 m) standard lengths. The concrete is then poured on top.
Geothermal & HVAC design: Stantec (Nuno Duarte, P. Eng.).Refrigeration: Cobalt Engineering. Architect: Petroff Partnership.Electrical: Ellard Willson Engineering. Geothermal contractor:Groundheat International. Suppliers: Uponor (radiant floor); Multistack (chillers).