By Mary Ellen Ternes
Oklahoma’s record temperatures this past June, July and August motivated me to retrofit my 1950s-era, Oklahoma ranch-style house with a new geothermal energy system. We live in a great place to take advantage of this process – did you know that Oklahoma is the home of the International Ground Source Heat Pump Association? Dr. Bose at Oklahoma State University is its executive director and an industry leader. If you were ever curious about this potential power source, read on.
I wasn’t immediately sold on geothermal usage, I had to study the process and economic return before investing, but in the end, I was persuaded because geothermal power takes advantage of the earth’s constant temperature to keep my home comfortable while using less overall energy and avoiding significant spikes in power usage (clearly visible on my OG&E power report) during periods when our power plants are struggling to keep up with demand. For example, in a single hour – 4-5pm on July 9 – my home’s power usage (primarily from air conditioning) spiked up to 8.78 kilowatt hours (kWh), while on a pleasant day when I’m not utilizing major appliances like my clothes dryer, my home generally uses power at a rate of less than 1.0 kWh. Just try to appreciate the impact on our power plants when all of us are using this much power at the exact same time. I also wanted to avoid the shocking bills, and increase my home’s resale value.
The geothermal process is simple enough. Of course, for Oklahoma residential applications, we’re not talking about tapping into energy from the earth’s magma – just cooling off, or warming up, the air in your home by exchanging energy with the constant ground temperature: in the range of 55 to 60 degrees Fahrenheit. In the summer, the ground temperature feels cool, and in the winter, it feels warm.
The process involves a system of high-density polyethylene pipe, buried horizontally between four and six feet deep, or vertically down to depths of 100 to 400 feet. Read your city ordinances, though – Nichols Hills classifies these systems as wells, and limits their depths to 250 feet. The less deep the holes, the more of them to be drilled. A solution (antifreeze in water is most efficient) circulating through the pipes exchanges energy to make the indoor temperatures approach the temperatures of the earth. In other words, the liquid solution carries heat from the earth into your home in the winter, and from your home into the ground during the summer. Inside your home, the air delivery ductwork conveys the conditioned air through your home just like conventional air conditioning and heating systems.
Here is what I’m looking forward to: delightful cool air in the hottest of summers and lovely warm air in the coldest of winters, with lower and more consistent electric and gas bills and without risking the post-traumatic stress of the infamous “Summer of 2011” utility bills. So, come on, severe temperatures. We be not afraid!