The Spread of Geothermal Heat Pumps around the World
The nowadays application of heat pumps in the world is increasing dramatically, with Sweden taking on a leadership role when it comes to ground source heat pumps energy generation, which covers 50% of Sweden’s heating energy needs. Switzerland currently operates more than 60,000 thermal pumps, which saves up to 150,000 litres of liquid fuel, preventing the release into the atmosphere of 39,000 tonnes of carbon dioxide and 325 tonnes of carbon monoxide. The United States is producing annually more than one million of geothermal heat pumps, that is backed up by federal laws, which at the same time require the newly erected buildings to be powered by ground source heat pumps.
In Germany, as well as in the UK, part of the geothermal installation cost is covered by government funded subventions. The current estimations which forecast that the world’s oil and gas deposits would last for 40-60 years more, push the traditional fuel (oil, gas, coal) prices up, which is expected to grow in the near future. In the context of decreasing oil and gas deposits, the World Energy Committee believes that by 2020 the share of geothermal heat pumps on the market will be around 75%. All these together, point to a growing and spreading trend of using eco-friendly solutions as means for supplying heat to households, particularly by using ground heat pumps.
Ground Source Heat Pumps—All You Need To Know
To date, the ground source heat pumps systems are considered one of the most energy-efficient technologies, which are environmentally friendly and to a certain extent deliver a sense of independence from the world’s political and economic crises that are known to have a direct impact on the traditional energy sources price trends.
About three-quarters of the energy required for generating heat, the pump takes from the ground, the remaining 25% is covered by the electric power that is necessary for operating the ground source heat pump’s compressor. The heat that is being collected from the environment, specifically from the underground upper layers, is available in unlimited quantities. The ground source heat provides an environmentally safe and cost-effective household heating.
How Does a Ground Source Heat Pump Work?
A heat transfer fluid is pumped into the pipes that are laid in the ground, which is heated to a certain temperature level. Subsequently, the heated mix is passed through a heat exchanger where the collected ground energy is being converted into heat and transferred to the pump’s internal circuit. Two compressors, which are installed independently from each other would ensure a proper control over the energy conversion process, better control of the power supply, improve the pump’s working rates and increase the equipment’s reliability.
Ground Source Heat Pump Systems
As it was mentioned already, the geothermal heating system pipes are installed within the ground in close proximity to the surface, still, the installation layout might differ from one pump to another. Depending on the chosen configuration of the pipes, the ground source heat pump systems can be classified in four distinctive categories:
- Systems with horizontal ground collectors
- Systems with pumps laid at the bottom of a water reservoir
- Systems with vertical ground collectors—known as borehole heat pump systems
- Radial or directional drilling
The system is composed of a network of pipes that are laid horizontally in the ground at a depth below the soil’s freezing point, usually 1,5 m below the ground’s surface. Therefore, a system like this would require a large area in order to be installed, which is necessary to ensure a correct spacing of collector pipes as to maximise their efficiency. It has been calculated that for heating 200 square metres of property, 500 square metres of land will be needed.
In order to install the horizontal heat collectors, a large bulk excavation is needed. The pipes are placed in the ground in a similar way as the underfloor heating tubes are installed in a house, guaranteeing the extraction of an equally distributed heat. The installation of pipes requires big excavation machines, a large area and a number of professionals specialising in ditch carving. The system’s significant drawback is that once installed, it will no longer allow for planting of trees, pond or driveways construction, in the collectors’ area, whereas it has to be left spongy and free from potential root damage.
This system, by contrast to others, is quite expensive. Drilling wells, which require special equipment, would considerably push your installation costs up. Digging boreholes create a bit of a mess at the start too, since you’ll have to ensure enough space to fit in the drilling equipment and for the pipes to be carried out and placed deep into the ground. However, it requires less space than horizontal collectors, which means you can use geothermal heating for already built houses and buildings located in small areas. The depth of a borehole ranges between 15 meters and 100 meters, depending on terrain, and the holes’ diameter is usually around 15 cm.
Water Reservoir Based System
The contour of the pipes is laid in a spiral layout on the bottom of a pond, 2,5-3 meters beneath the water’s freezing layers. It is recommended, that the distance to the nearest reservoir does not exceed 100 m and that the area of the water reservoir should be at least 200 square metres. The main advantage of this system is that there is no need to perform time-consuming excavation works, but special permission for using the region’s water resources are required.
It is believed that this is the most cost-effective way to install and operate a geothermal heating pad since there is less initial investment and greater efficiency. But lakes and rivers deeper than 2 meters can’t be found everywhere, which significantly limits the application of such a system.
Radial or Directional Drilling
As an alternative to trenching, the heat pump’s tubes may be placed within the ground by mini horizontal directional drilling equipment. This technique can install pipes under backyards, driveways, gardens or other structures without disturbing them, with a price tag that often is somewhere in between of those for trenching and vertical drilling. This setup also differs from horizontal and vertical collectors systems as the loops are installed from one central box case, further reducing the ground space needed. Due to the small-scale size of the installation equipment and the ability to dig beneath existing structures, radial drilling is often put in place after the property has been built.
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