Geothermal Energy

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.

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.