[caption id="attachment_51980" align="alignright" width="400" caption="Drilling trucks and equipment designed to separate mud from drilling water for recycling are part of the process for installing a ground loop field for commercial or residential customers."][/caption]
NORTH BAY -- With high heating oil, propane and electricity prices, more commercial and residential building owners -- as well as municipalities and school systems -- are considering geothermal ground source heating and cooling as an alternative.
Interest in this energy-efficient, environmentally clean and cost-effective technology is also on the rise due to 2010 CalGreen building code requirements (Part 11, of the California Code of Regulations, Title 24) mandating a reduction of greenhouse gases by 3 million metric tons by 2020.
[caption id="attachment_51981" align="alignleft" width="315" caption="Heat exchange pumps above ground extract energy from water to provide building heat in winter and cooling in summer."][/caption]
“There are some 15,000 to 20,000 operating geothermal systems in Pacific Northwest service areas and perhaps half as many more in California,” according to John Geyer, a geothermal consultant and certified geothermal designer in Vancouver, Wash. “The national growth rate is between 10 and 15 percent a year.”
“The key to geothermal heating and cooling’s 300 percent to 500 percent efficiency, relative to grid power consumed and operating cost savings, is that grid power is only used to drive the loop-water circulating pump, the refrigeration compressor and the forced air blowing fan. External fuel is not used to create or dissipate heat.”
Geothermal heat exchange systems cost two-thirds less to operate compared with propane or fuel oil costs per year -- with no harmful emissions.
They also offer the fastest payback -- less than five years to 10 years -- among energy-saving systems such as fuel cells and solar, and have the longest life cycle, up to 50 years. Geothermal can reduce energy loads by up to 30 percent to 60 percent.
According to industry statistics from www.geoexchange.org, heat pump shipments have jumped from fewer than 11,000 units in 1983 to 112,000 units shipped in 2011.
Legislation passed by Congress in 2009 offers homeowners a federal tax credit of 30 percent of any geothermal system installed by Dec. 31, 2016, and commercial projects may deduct 10 percent. Both credits apply toward defraying equipment and installation costs.
This form of geothermal energy is not to be confused with electricity produced at the Geysers when natural steam (or steam resulting from water injected into deep wells to reach hot rock layers above lava), rises to the surface to power turbines.
Instead, geoexchange technology uses a field of subterranean tubing, called a ground loop, to extract low-grade heat energy from water circulated underground, taking advantage of the earth’s near constant temperature of 55 to 65 degrees Fahrenheit.
The ground acts as a heat source warming a building in winter, and a heat sink to provide cooling in summer, with the aid of a water source heat pump, called a heat exchanger, on the surface.
Loops can be installed horizontally or vertically underground or on the surface in a pond, lake or irrigation water holding tanks.
A major North Bay geothermal installation was completed in March at the Buck Institute for Research on Aging in Novato.
PAE Engineering was the consulting firm under contract to Trison Construction for the Buck project. Some 325 bores were drilled to a depth of 400 feet containing miles of high-density polyethylene tubing one to 1.25 inches in diameter.