At EcoBuild, the Europeans were heavily into geothermal heating, have been for years and are now very busy converting UK designers and specifiers. These experts claim that energy consumption for heating can be lowered by up to 75% by using soil or groundwater as the heat source. REHAU is another very well-known European company expert in ground source energy. They too claim the 75% heat with payback times of less than 7 years and emitting 75% less Co2 than conventional oil heating.
What we need to do now is educate and switch everyone to thinking about what’s there beneath their feet and the ‘obvious’ answer to everything. REHAU suggested that one of the good starting points might be by reference to Manfred Reuss, physicist with the Bavarian Center for Applied Energy Research, and first ask some simple questions.
Geothermal heat constantly flows from the interior of the planet and is not subject to any seasonal or climatic fluctuations. In extremely active geothermal regions, hot magma almost extends to the surface; therefore the flow of geothermal heat in these regions is accordingly greater.
How can we store geothermal heat?
The heat constantly streams from the interior of the Earth; therefore there is no need to store it.
Are any hazardous substances brought to the surface when we use this heat?
No. Geothermal heat is brought up from the ground in a closed system. There is no direct contact between the ground and the conducting medium in the pipes.
Does using geothermal heat negatively affect plant growth?
Plants only make use of the top few metres of the ground, where weather influences, such as solar radiation and rain, hold sway. At a depth of 15 metres, almost no seasonal influences are detectable and the flow of geothermal heat predominates. As the geothermal heat probe is installed at depth, it has no effect on plants. But it is best not to plant deep rooting trees above the horizontally laid connection pipes. Horizontally laid heat collector systems, laid approx. 1.20m to 1.50m deep affect plants, but, if laid correctly, this impact is relatively minor.
Heating with geothermal heat – what is important?
In a good system, the individual elements work well together. The geothermal heat probe is the most important element, and no compromises must be made as regards its quality. The stipulations of VDI regulation 4640 are helpful in this respect.
- Correct design to VDI 4640
- High-quality raw materials
- Correct backfilling
- Proper installation
Can geothermal heat be combined with solar heat?
Yes! In the warm half of the year, excess solar heat can be dissipated into the ground by geothermal heat probes. The ground is regenerated faster and, overall, soil temperature is higher over the long-term. The probes can be laid somewhat more densely, where space is in short supply on small sites. The solar collector also benefits from not standing idle during the summer months. This spares the materials and prolongs working life.
How does it work?
Heat pumps are normally used for harvesting geothermal energy from the ground. In principle, these work like fridges – heat is extracted from the fridge contents and given off to the surroundings via cooling fins. In this way, the pump extracts heat from the ground using special pipe systems (probes or collectors). This heat is given up, at a higher temperature, to another heating medium (water/air) visa heat exchangers. This heat can then be used underfloor heating in full or in part by other heating systems
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