Anyone who builds their own house and is looking for climate-friendly heating should also be interested in the topic of geothermal energy. The fact that Earth is an internally hot planet is neither a secret nor a particularly new discovery. But in times of climate change, to reduce CO2 emissions, it is almost necessary to use natural geothermal energy to heat your dream home. Below you can find out exactly how it works and what you need to take into account:
HOW CLIMATE-FRIENDLY HEATING WORKS WITH GETHER HEAT
The inner core of our planet has temperatures of over 6,000 degrees Celsius. The closer we get to the Earth’s core, the hotter the Earth’s surface becomes. And the waste heat stored directly beneath the earth’s surface is, in principle, enough to heat a house.
However, surface geothermal energy must be brought to the temperature of 35-55 degrees Celsius necessary for heating or hot water production using a heat pump: In the evaporator of the heat pump, a refrigerant absorbs the geothermal heat transported there and evaporates it. The compressor, usually electrically powered, compresses the refrigerant now vapor and thus increases the temperature and pressure. In the condenser, the hot gas releases thermal energy to the heating system and then, with the support of a so-called expansion valve, condenses back into the coolant so that the cycle can start again.
THE ROLE OF “JAZ” IN GEOTHERMAL HEATING
The geothermal heat pump is more efficient the less electrical energy is required to reach the desired target temperature through compression. The ratio between the energy used and the thermal energy generated is called the annual performance factor (JAZ). A very good value, for example, is if a heat pump produces 6,750 kWh of thermal energy in a year using 1,500 kWh of electricity and therefore has a JAZ of 4.5.
The JAZ is influenced by the temperature difference between the initial temperature of the geothermal energy and the target temperature of the heating. It is therefore best to combine a geothermal system with underfloor heating, which requires a low flow temperature of 35 degrees Celsius. On the other hand, your house should be insulated as well as possible, so that high heating is not necessary from the start or, in case of particularly low outside temperatures, the water circulating in the heating circuit does not have to be further heated with an electric resistance.
HEATING OPTIONS WITH GETHER HEAT
Basically, there are four different ways to harness near-surface geothermal energy for use in a heat pump. Very often, geothermal collectors or geothermal probes transport the energy to the heat pump.
Geothermal collectors are installed horizontally in the garden at a depth between 1.20 and 1.50 meters below the surface. In pipe circuits, for example in underfloor heating, a water-antifreeze mixture (brine) circulates as a carrier fluid, which absorbs heat from the ground and transmits it to the heat pump. In principle, geothermal collectors do not use heat from inside the earth, but stored solar energy that is transferred into the ground through solar radiation or precipitation. In addition to the fact that the temperature in the ground is not constant, the disadvantage of geothermal collectors is their size. Their surface area must be approximately double the living area to be heated. This area cannot be developed and only limited planting may be permitted.
Spiral collectors or geothermal baskets, which are placed in the ground at a depth of about 4 meters, are more space-saving than geothermal heat collectors. Here geothermal heat is obtained via (coiled) pipes installed in trenches or wells usually dug with an excavator. The greater depth of the tubes ensures greater temperature stability compared to cheaper geothermal collectors.
Geothermal probes go even deeper, usually reaching 30 to 100 meters deep into the earth. As with geothermal collectors or baskets, the energy is transported to the heat pump via brine circulating in the pipes. Geothermal probes require special drilling, which is expensive and must be approved. They are generally prohibited in water protection areas and in particular hydrogeological conditions. The advantage of geothermal probes is the use of heat at an almost constant temperature coming from inside the earth, resulting in lower operating costs.
Depending on the location of your home, groundwater near the surface can also be used to harness geothermal energy. For this purpose, underground water is withdrawn via a production well, transported directly to an underground heat pump using an underwater pump and reintroduced into the water network used in a second absorption well. Groundwater heat pumps avoid heat exchanger losses of ground source heat pumps and are recommended as soon as an adequate supply of groundwater is available. The use of groundwater for geothermal purposes requires a permit under the Water Act and is generally prohibited in water protection zones and in particular hydrogeological conditions.
Apart from this, geothermal energy can also be used on a large scale, i.e. for multiple households at the same time, in geothermal systems. Some of their drilling goes several kilometers deep into the earth’s interior. At these depths the temperatures are so high that the water vapor can be used directly for the heating market through district heating networks without a heat pump. If your property offers the possibility to connect to an existing regional or local district heating network, this is the best and most economical way to use climate-friendly geothermal energy for heating and hot water preparation of your home because a heat pump is not required.
ADVANTAGES OF HEATING
By using geothermal energy to heat and produce hot water in your home, you actively contribute to climate protection. The system is emission-free and uses geothermal renewable energy source. Furthermore, geothermal heating saves space if you ignore the geothermal collector variant and the associated space requirement in the garden. Although the operation of the heat pump uses electricity. The heat pump requires no maintenance and most of the energy in the form of geothermal energy costs nothing, ensuring low running costs.
But geothermal heating offers another advantage. In addition to heating in the cold season, the system can also cool the house in the summer without incurring large costs. During warm weather, the soil temperature near the surface is cooler than the outside air temperature. In this way the colder carrier liquid from the geothermal probe or geothermal collectors can be used in summer to cool the water circulating in the heating circuit directly via a heat exchanger without compression. This means you can reduce the room temperature by up to 7 degrees Celsius.
However, geothermal system efficiency also comes at a price. Drilling a geothermal probe or groundwater well is particularly expensive, and a geothermal heat pump costs more than, for example, an air/water heat pump. Higher acquisition costs are amortized only over the operation and useful life of the system or home.
As a result, geothermal energy is particularly interesting in new buildings, where building heating and insulation can be perfectly coordinated. Your nearest construction partner will be happy to advise you on how to optimally design your dream house and equip it with a climate-friendly geothermal system.
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