Earth River Geothermal

The Earth River company of Annapolis designs and installs ground source heat pumps for buildings. Average systems cost about $14,000 after all rebates and subsidies are accounted for, and can pay for themselves in as little as five years through savings on electric and heating bills.

Installation consists of burying a length of high-density polyethylene tubing underground near a building, and connecting both ends of that tube to an above-ground reversible heat pump. If you’re reading this and you are already familiar enough with geothermal technology, skip the next few paragraphs.

A heat pump is a machine that takes heat from one area, and moves it into another area. The central air conditioning systems in many buildings use what’s called an air source heat pump. In the summer, these take heat from the air indoors, and move it into the air outside, acting to cool the air inside while warming the outside air. The process can be reversed in the winter.

In a ground source heat pump, heat is moved between indoor air and water that’s circulated underground. For two significant reasons, a ground-source heat pump works more efficiently than an air source heat pump, and so costs less money to operate.

First: water has better thermal conductivity than air. This means that if you had a gallon of water and a gallon of air, both at equal temperatures and pressures, and you put them each in a pot over a fire, the water would heat up faster than the air.

Second: the temperature of the ground past a depth of about 4 feet is nearly constant all year. As water travels through the tubing, it’s brought to the same temperature as the ground – about 57 degrees farenheit in Maryland. Because this temperature is already (relatively) close to the temperature we desire for our indoor air, the heat pump doesn’t have to work as hard to get the same result. It doesn’t have as steep a hill to climb.

Indoor air, drinking and bathing water, or anything else can be heated or cooled by this system.

There may still be applications for this technology that remain unfound or largely unpracticed. Earth River is unique in offering to tie in their systems with radiant heat flooring, which they claim makes radiant heat affordable for the average home.

The company has the versatility of offering both horizontal and vertical wells: underground tubing can be buried under a wide, shallow trench, or a deep hole that only takes up a few square yards at the surface. The second option keeps geothermal available to buildings on smaller plots of land. Earth River has installed systems in places ranging from Baltimore to the Washington D.C. metro area, and the company does a complete job of hiring and directing subcontractors for the digging, plumbing, and HVAC work. As a result, they say their subcontractors have begun hiring new employees.