What is geothermal energy and how to use it at home
You might have came across the expression “geothermal energy” when researching energy efficiency but failed to understand it fully. If you have some question about geothermal units and the possible domestic uses, take a look at the following info we put together to clear things out.
What is exactly the geothermal energy?
In short, geothermal energy is the heat from the earth. The shallow ground near the Earth's surface have a constant temperature of 50°–60°F, and there are some higher temperature reservoirs deep down -like hot water or steam- that can be accessed by drilling. The heat reservoirs that need to be accessed by drilling are mostly used by utilities and industries to drive generators and produce electricity, or directly circulated to various uses in buildings, roads, agriculture, and industrial plants.
How can this energy be used at home?
The shallow ground, or the upper 10 feet of the Earth, is warmer than the air above it in the winter and cooler in the summer. The geothermal heat pumps take advantage of that, to heat and cool buildings. Geothermal heat pump systems consist of three parts: the ground heat exchanger, the heat pump unit, and the air delivery system (ductwork). In the winter, pump gets the heat from the exchanger, and delivers it by the ducts.
In summer, the process is reversed, and the heat removed can also be used to heat water -instead of cooling it by the soil- providing a free source of hot water.Geothermal heat pumps need much less energy than other heating options and are more efficient than other cooling systems. They save energy and money, and it reduces air pollution, too. GHP -short for Geothermal Heat Pump- is the main component of the passive homes, and they are suitable for all size of buildings.
Installation of GHP for residential use
An accurate calculation of the heating and cooling needs is the first step of the process. If you already have the ductwork for your air-source heat pump or HVAC, you probably will just need the exchanger and the pump.
You could also choose a dual-source heat pump, that combines the best of both systems. These equipments are more efficient than air-source units, but less efficient than a pure geothermal. The main advantage of dual-source systems is that they cost much less to install than a single geothermal unit, and is still an energy efficiency improvement.
A good contractor can tell you which one is best -considering your current setting- and the viability of the heat exchanger -the outside pipes-, considering the terrain your home is built in.
Cost, incentives and savings of GHP
A GHP is more expensive than other heating and cooling systems, no need to lie here, but the return on the investment is amazingly fast. According to Energy.Gov calculations, you may recoup your initial investment in two to ten years just through lower utility bills. If the new whole system, or only a retrofit, is included in a mortgage, the investment will produce a positive cash flow from the beginning. Consult with your bank or mortgage company about that particular home improvement, focused on energy efficiency.
On most US states -and especially in California- there are plenty of incentive programs for energy efficiency and renewable energy conversion, from rebates to tax credit. Check Energy.gov, DSIRE database and Energy Upgrade for the latest programs. Also most major contractor companies have financing options that make that upgrade very affordable.
Heating and cooling your home generates the biggest spend in utility bills annually, so converting to a more energy efficient option can save you loads every year. GHP is a super efficient system and uses clean energy, so it must be an option to consider if you plan to upgrade your current equipment.