Geothermal Energy – What’s in a Name?

Recently, use of the term “geothermal energy” has become somewhat confusing. For the longest time, geothermal energy implied deep-seated, super hot (+180˚C) water, brought to the surface to provide heat for space heating or electricity generation. It is the energy behind geysers and hot springs. Think Old Faithful and Banff Hot Springs.

But with the advent of heat pumps, shallower, much cooler water could be used for space heating. Purists insisted on calling the new technology “earth energy”, or “geo exchange” or “ground-source energy”. The debate intensified to just short of rioting in the streets, but new subdivisions, advertised as economical and environmentally friendly due to “geothermal heating”, sprang up across the country. And people oblivious to the debate began to see geothermal only as a method of home heating that involved heat pumps and a bit of tubing.

So which side is right? Etymologically speaking, they both are. The term geothermal is derived from two Greek words: geo, meaning earth; and thermos, meaning heat. Earth heat. There is no reference to either temperature or depth.

Practically speaking, there is a big difference. In most parts of Canada, deep geothermal requires wells more than five kilometres deep, and that is prohibitively expensive for someone who just wants to heat their home. And shallow geothermal can’t deliver the heat required to create steam to drive turbines, so it won’t be used by utilities.

Regardless of what you consider is the real geothermal, both are among the cleanest sources of energy, and, over the long term, economical.