Plainville keeps it simple
The concept of transferring heat from the earth's surface is an economic and environmental choice for schools, but reducing the load before installing the heating source remains the best investment for saving money.
At Plainville Public School in Northumberland, the single-story country school has average insulation (R-16 in the walls and R-20 in the roof). Lighting uses standard flourescent fixtures with energy saving ballasts. There is no energy management system; control of the mechanical system is performed by simple thermostatic controllers.
But the school's energy consumption is less than 94,000 kWh for lighting and power, and less than 210,000 of kWh (equvalent) for all heating, ventilation, and air conditioning demand.
On a square foot basis, Plainville consumes 4 kWh for lighting/power, and just over 9 kWh/ft² for heating, for a total of 13.2 kWh per square foot. In terms of electric peak, it is 96 kW for the school, or just over 4 W/ft².
The operating costs: $23.20 /ft² for all mechanical costs (including plumbing, site servicing, etc), and $9.15 /ft² for electrical (including fire alarm, site servicing, etc).
A common experience in Canadian and U-S schools that have installed ground-coupled systems is the low level of maintenance. Filters need to be cleaned on a regular basis to maximize return air flow, and loops need periodic flushing to remove residue and entrained air. While an earth energy system provides greatest savings when it is minimally sized to the load, the industry norm in institutional and commercial sites is to design for moderate over-sizing. This practice allows for thermal recovery in the ground loop collection area, and reduces the strain on components. Also, it provides a form of redundancy should a compressor or circulating pump fail.
Plainville is one of more than 60 schools across Ontario that have installed earth-coupled heat pumps to provide full heating, cooling and DHW demand. In addition to low operating and maintenance costs (and often the lowest first cost), school officials are impressed with the lack of combustion technology, which eliminates the need for fuel storage, chimneys, CO2 venting, and the potential for vandalism and accidents.
"These sheets are made possible through a contribution from Natural Resources Canada."