Serene Lea Farms – Geoexchange System

Print This Page

The need

When the Stobbe family bought Serene Lea Farm – a 100-year-old farm with 140 dairy cows near Mara in south-central B.C. – they undertook to construct a brand-new dairy farm using the best technology and products available. The Stobbes wanted to make the farm as environmentally sound as possible, while keeping long-term labour and energy costs under control.

The area where the farm is located, as well as the nature of dairy farming itself, poses specific heating and cooling needs:

• Seasonal temperatures range from 30°C in the summer to -30°C in the winter,
• The farm includes a 469-square-metre home as well as 1051-square-metre barn with milking parlour, offices and mechanical room,
• Each cow produces 1,000 BTUs of heat plus a great deal of moisture, so the barn requires dehumidification as well as cooling in the summer,
• The barn floor must have in-floor heating to prevent water lines from freezing and to aid in clean-up, and
• To meet health and safety regulations, milk must be cooled from 32°C to 1°C as quickly as possible.

The Stobbe family wanted a heating and cooling energy source that would be environmentally responsible, have a viable payback period and use less energy than a conventional system. Because natural gas service was not available in their area, their energy choices were limited. The Stobbes decided that a geoexchange system was their best option.

The technology

Geoexchange systems take advantage of the sun's energy stored in the ground, where the earth's temperature remains at about 12° C throughout the year. In the winter, heat pumps are used to extract heat from the ground or ground water and transfer it into buildings for space heating or hot water heating. In the summer, the heat pumps reverse the process, removing heat from the building and returning it back to the ground, thus cooling the building. In other words, the ground or water acts as a heat source in winter and a heat sink in summer.

A geothermal heat pump system consists of pipes buried in the ground, a heat exchanger and ductwork into the building. The series of pipes, commonly called a "loop," is buried in the ground, either vertically or horizontally, near or beneath the building. The loop circulates a fluid (water, or a mixture of water and antifreeze) that absorbs heat from, or relinquishes heat to, the surrounding soil, depending on whether the ambient air is colder or warmer than the soil.

The project

Jim Croken of Okanagan Geothermal Ltd. was the prime contractor and project manager on the project, with engineer Jeff Quibell doing preliminary project planning and feasibility work, and Ralph Salm of Geofurnace contributing installation expertise.

Okanagan Geothermal designed a closed horizontal ground loop for a 20-ton load with 40 tons of heat pumps. This design was used because it has lower capital costs and, because of its careful design, achieves a balance in removing and restoring the earth's heat. The loop was buried away from the farm buildings in an adjacent field.

The system is fully automated and can be monitored at any time from the computer system in the office or home. The circulation system has automated valving complete with backup pumps if required.

A dehumidifier was installed in the barn. Heat recaptured from the dehumidification process is dumped back into the closed loop and contributes to heating the remaining barn space, offices and mechanical room. Dehumidification makes the heating and cooling more efficient.

The installation at Serene Lea Farm took six months, and the Stobbes' goals were accomplished on time and on budget. Serene Lea Farm is the only dairy farm in Canada with year-round heating and cooling provided by geothermal energy.

The benefits

Operating cost savings

Serene Lea Farm's geoexchange system uses about 40% less energy than a conventional system. Capital costs ($130,000) were about the same as for a fossil fuel boiler system; however, the geoexchange system provides air conditioning, while the conventional system costs do not include cooling. When air conditioning costs are included, the geoexchange system saves $8,400 a year, providing a six-year payback at current energy rates.

Improved safety and product quality

Normally it takes about an hour to cool milk, but the geoexchange system cools the milk much more quickly. As a result, the farm achieves an improved, safer product by eliminating bacteria that flourish at higher temperatures.

Enhanced comfort

The heating and air conditioning of the barn create a more comfortable environment for the cows, resulting in a consistently better product. In addition, the cows' drinking water is preheated to 21°C using reclaimed energy from the system, thus conserving the animals' body heat.

Environmental and social benefits

An advantage of geoexchange systems is that they work by concentrating naturally existing heat, rather than by producing heat through the combustion of fossil fuels, thus reducing greenhouse gas emissions.