Geothermal energy is heat derived within the sub-surface of the earth. It is thermal energy generated and stored in the Earth. Thermal energy is the energy that determines the temperature of matter. Geothermal energy can be used for heating and cooling purposes in homes, businesses, or schools, or can be harnessed to generate clean electricity.
For homes and businesses, most geothermal systems will be geothermal heat pumps. Geothermal heat pumps (GHPs), also known as ground-source heat pumps, can heat, cool, and even supply hot water to a home by transferring heat to or from the ground. This technology has been keeping consumers comfortable for more than 75+ years and can cut energy bills by up to 65% compared to traditional HVAC units.
Geothermal energy provides a significant share of electricity demand in countries like Iceland, El Salvador, New Zealand, Kenya, and Philippines and more than 90% of heating demand in Iceland. The main advantages are that it is not dependent on weather conditions.
Geothermal power is cost-effective, reliable, sustainable, and environmentally friendly. Technological advances have expanded the range and size of viable resources, especially for applications such as home heating, opening a potential for widespread exploitation. Geothermal technologies for direct uses like heating, hot water (heat pumps), greenhouses, and for other residential or commercial applications are widely used today.
Geothermal Pool Heating
Pools are almost a necessity for many homes, and certainly for resorts and hotels. It’s not uncommon for pools in recreational centers to expend $50,000 per year for fuel to heat a pool. The typical methods by which a pool is normally heated include: Fossil fuel (combustion heat), Solar collectors (solar-thermal), Electric resistance, or Heat pump (either “air sourced” or “geothermal sourced”)
Fossil fuel heating for pools and spas is an old favorite. First cost is relatively low, but that comes at a higher price environmentally (high greenhouse gas or “GHG” emissions) and depending on the fuel source, it can cost quite a bit of money.
The most energy efficient and renewable source for pool heating is solar-thermal, but solar is dependent upon the cooperation of the weather. Cloudy and cool days can mean a cold pool, and may require need for backup heating sources much of the year.
Electric resistance heating consumes electricity as it heats up electrodes or heating elements over which the water passes, providing a clean and safe water heating alternative, but resistance heating can be pretty expensive (energy-wise).
Water source equipment provides the best way to capture waste heat. The rejected heat from a water sourced heat pump may easily be made available to other systems in need of heating BTUs, like a swimming pool. This can be accomplished passively through an exchanger, or actively through a pool heat pump.
Geo Pool Heating?
Geothermal Pool Heat Pump Advantages
- Unaffected by external temperatures
- Can be used year-round
- Pipe system maximizes heat generation efficiency
- Cheaper to operate than gas and electric resistance heaters
Geothermal Pool Heat Pump Disadvantages
- Complex and expensive installation
- Complex repairs (underground heating source)
Geothermal Heat Pumps or Ground Source Heat Pumps
A geothermal heat pump (GHP) or ground source heat pump (GSHP) is a central heating and/or cooling system that transfers heat to or from the ground. It uses the earth all the time, without any intermittency, as a heat source (in the winter) or a heat sink (in the summer). This design takes advantage of the moderate temperatures in the ground to boost efficiency and reduce the operational costs of heating and cooling systems, and may be combined with solar heating to form a geosolar system with even greater efficiency. They are also known by other names, including geoexchange, earth-coupled, earth energy systems. The engineering and scientific communities prefer the terms “geoexchange” or “ground source heat pumps” to avoid confusion with traditional geothermal power, which uses a high temperature heat source to generate electricity. Ground source heat pumps harvest heat absorbed at the Earth’s surface from solar energy.
Like a refrigerator or air conditioner, these systems use a heat pump to force the transfer of heat from the ground. Heat pumps can transfer heat from a cool space to a warm space, against the natural direction of flow, or they can enhance the natural flow of heat from a warm area to a cool one. The core of the heat pump is a loop of refrigerant pumped through a vapor-compression refrigeration cycle that moves heat. Air-source heat pumps are typically more efficient at heating than pure electric heaters, even when extracting heat from cold winter air, although efficiencies begin dropping significantly as outside air temperatures drop below 41 °F. A ground source heat pump exchanges heat with the ground. This is much more energy-efficient because underground temperatures are more stable than air temperatures through the year. Seasonal variations drop off with depth and disappear below 23 ft to 39 ft due to thermal inertia.
- Setup costs are higher than for conventional systems, but the difference is usually returned in energy savings in 3 to 10 years.
- Geothermal heat pump systems are reasonably warranted by manufacturers, and their working life is estimated at 25 years for inside components and 50+ years for the ground loop.
- Like a cave, the shallow ground temperature is warmer than the air above during the winter and cooler than the air in the summer.
- A ground source heat pump extracts ground heat in the winter (for heating) and transfers heat back into the ground in the summer (for cooling).
- Some systems are designed to operate in one mode only, heating or cooling, depending on climate.
- Geothermal heat pumps can operate in any climate—hot or cold—because of the earth’s constant underground temperature (from 45° to 75° F depending on location). In fact, millions of GHP systems are already heating and cooling homes and businesses worldwide, and that includes all 50 U.S. states.
- Think of GHPs as a long-term investment. They’re built to last and have extremely long life spans. Expect to get around 25 years out of GHP indoor components (i.e. the heat pump) and 50-plus years for ground loops.
- Although installation costs can be up to several times more expensive, GHPs are up to 65% more efficient than traditional HVAC units and pay themselves back over time in energy savings—typically within 10 years.
- GHPs are more energy efficient than traditional HVAC systems and can help lighten the load on the electric grid, especially during summer peak demand. In addition, they can help reduce carbon emissions thanks to their high efficiency.
- There are four basic types of ground loop systems.
- Three of these — horizontal, vertical, and pond/lake — are closed-loop systems.
- The fourth type of system is the open-loop option.
- Which one of these is best depends on the climate, soil conditions, available land, and local installation costs at the site.
- All of these approaches can be used for residential and commercial building applications.
- Hybrid systems using several different geothermal resources, or a combination of a geothermal resource with outdoor air (i.e., a cooling tower), are another technology option. Hybrid approaches are particularly effective where cooling needs are significantly larger than heating needs.