McMath gets it both
The Bob McMath Secondary School could have installed a conventional heating and cooling system that would have consumed 1.2 million kilowatt hours of electricity AND 1,800 gigajoules of natural gas, for an annual energy cost of $79,000.
Or it could install a ground-coupled heat pump system that would cost less than $68,000 a year in operating costs, including the supplemental heat provided by high-efficiency natural gas condensing boilers. AND come in at 22% below budget for installation.
Richmond School District #38 elected to become one of the first institutional sites to use the Svec Spiral ground loop design (named after the inventor of the coiled pipe, Dr Otto Svec, of Canada's National Research Council). Buried horizontally, with at least 2 m of soil on top, the high-density polyethelene corkscrew requires less than one-third the footprint of conventional loop designs, for the same thermal efficiency.
Like other ground-coupled loops, the integrity of the pipe is tested both during and after installation. Each section is filled with water and pressure-tested for four hours to see if there are any leaks before the trench is back-filled over the pipe. Each separate run is joined to a header for the trip to the school, and then filled with the selected heat transfer fluid, purged of air, and operated at high pressure with no tolerance for pressure drops (which would indicate a leak). The fluid is circulated in both directions at high velocity, to ensure that both heating and cooling modes will work as planned.
The polyethelene used in ground loops is the same plastic that has been used for years to transport natural gas across the country. It is inexpensive, easy to join using industry-standard socket or butt fusions, and offers long life (some ground-coupled manufacturers place a 50-year guarantee on their loops).
The two school buildings will receive 80% of their heat from a 108 ton earth energy unit inside the facility, where it is protected from weather and vandalism to decrease maintenance problems. The balance of heat on very cold winter days, will be met through use of a supplementary natural gas condensing boiler, the school's link to conventional energy systems.
In an effort to decrease operating costs, many provincial education departments limit the amount of floor area that can be cooled. McMath will be able to utilize the ground loop to increase this level, thereby becoming one of the first schools to offer full cooling capability for education and for outside revenue sources.
"These sheets are made possible through a contribution from Natural Resources Canada."