Would you believe that an environmental advocate hired a drill rig to help reduce global warming pollution? No, I wasn’t drilling for oil or gas, or burying my carbon dioxide (hmmm). I was installing a geothermal system for my home.
The geothermal system design we chose actually provides us with three services: cooling, heating and an improvement in the efficiency of our existing solar hot water system. It will play a key role in getting our home closer to net zero energy. The goal was to replace our gas furnace and our older air conditioning (AC) unit with the most efficient heat and air system on the market. We chose the WaterFurnace Envision unit from WaterFurnace.
My power comes from TVA through Knoxville Utility Board (KUB) and in 2008, TVA claimed to produce 672 tons of CO2 for every gigawatt hour. So we must get to pounds of CO2 per kWh — a number we can understand.
For heating, given that we have replaced a natural gas furnace that was about 90% efficient with the geo unit, we will look at the fuel switch from therms (gas) to kWh (electricity). There are 29.3 kWh per therm, so replacing one therm (100,000 BTUs) = (11.7 lbs CO2) with 29.3 kWh of TVA electricity (100,000 BTUs)= (39.26 lbs CO2) does not on the surface look like a good deal for the environment.
But remember that this Envision geo unit uses over 5 times less energy, so we should divide the number by 5 and this would give you 7.85 lbs of CO2 per 100,000 BTUs. We would also anticipate that part of the time, the solar PV panels will run the system, although how much solar we generate in the winter months is yet to be determined. It is safe to assume that the 7.85 lbs of CO2 per 100,000 BTUs will be lower from the solar running the system in the daylight.
The cooling is going to be a large jump because we retired the 10 SEER electric unit. While it’s a little like comparing apple and oranges, this unit has a 30 EER rating, which would be about a 34 SEER. Again this will be significantly more efficient. The bottom line: I believe this unit will cut our carbon footprint for both heating and cooling, save us money in the long run, and is more comfortable for living (humidity, sound).
The 3 ton unit with the vertical drilling was approximately $23,000. These units are subject to the 30% Federal tax credit. We received a loan from our local power company to allow payment of up to $12,500 on our bill. I’m unclear on the “payback” timeframe until we see the performance in our home and usage, but my guess at right now: about 10 years given the amount of power we use, it would be less for people with heavier use patterns.
So why go geo? We are decreasing our carbon and other air pollution, contributing less to mountain top removal mining, and coal ash from burning coal, or nuclear waste piling up at reactor sites, and hot water which gets dumped into our rivers from running nuclear power plants. Its an investment in our home and a better world, so drill baby drill…..
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