Geo-exchange

Perhaps you saw the recent article in the Chronicle about geothermal energy.  We're doing something a bit different -- geo-exchange.

What is this and why are we doing it?  Geo-exchange uses the temperature of the earth to provide cooling and heating. If you drill into the soil below us the temperature of the mud is about 70F.  So when you pump water downthere it comes back up at 70F. You use that water just like the freon from a heat-pump; in summer you use it to cool air to 70F and in winter you can heat air up to 70F. If you want it colder you need a chiller to bring the temperature down a little bit more -- we will have one of those. In winter you heat it a bit more, if needed (we've got that too).  Our units and common house then use the same forced air AC equipment that's currently inside a home to heat and cool.  

In our very first phase of construction we drilled 62 holes 300 feet deep to access this source.

Why? According to the Department of Energy's Oak Ridge National Lab Geo-Exchange is one of best ways to improve energy efficiency and to reduce energy demand and load on the grid: “This analysis found that GHPs have a tremendous impact on electric power systems by reducing the requirements in capacity, generation, and transmission, as well as carbon emissions.”  That saves money: we estimate that our electric bills may be roughly 40% lower than with regular AC. Plus, less noise: we won't have 30+ AC units on the roof making noise at night.

Returning to the Chronicle article, geothermal is the term for drilling a very deep hole to a source of very high heat, let's say a mile down and 400F or 500F temperature. Water pumped  down comes back as superheated steam which is used to run turbines and generate electricity. This is even better than windmills or solar panels, because it works 24 hours a day regardless of the weather. Iceland gets about 1/4th of its electricity that way, Kenya hopes to generate 50% of its electricity from geothermal by 2030. It's the only nice thing about living near a volcano I can think of.