Submersible centrifugal pumps

These pumps are used in geothermal plants to convey hot water to the earth's surface. The water is accelerated and pumped up by a rotating wheel. Submersible centrifugal pumps pump up to 150 litres of water per second. Depending on the head of the deep water, they are suspended at a depth of several hundred metres. One pump unit is up to 35 metres long, costing several hundred thousand euros. BakerHughes is currently the market leader for these special feed pumps. In development projects they strive for a service life of 3 years per pump.

CIGS solar cells

CIGS solar cells consist of a layer of copper, indium, gallium and selenium (abbreviated to CIS or CIGS) that is only a few micrometres thick. During production, this absorber layer and other contact and intermediate layers are deposited on glass sheets in integrated processes. A second glass plate is then added and the solar module is complete.

Maintenance costs

Experts estimate that servicing and maintenance account for up to a quarter of the costs of offshore wind farms, while the turbines themselves account for around a third. By way of comparison: On land the costs of the turbines account for two thirds of the total costs, while the proportion of costs due to servicing and maintenance is in the low, single-digit percentage range.

Calculating the yield

Operators can use a simulation programme to calculate the possible yield of a renewable power plant project at a specific location. The tool plans how the plant must be constructed and designed to feed the targeted amount of electricity into the grid. Plant constructors can check whether a power plant powered exclusively by wind or solar energy or a hybrid power plant makes sense.

Deep geothermal

In Germany, deep geothermal refers to the borehole extraction of geothermal at depths greater than 400 metres and temperatures over 20 degrees Celsius. Deep geothermal uses either natural hot water resources or heat stored in the rock. Both can be used to generate heat and electricity. Germany’s deep geothermal sector currently has eight power plants for electricity production and five combined heat and power plants for heat and electricity production. (Figures from the German Geothermal Association)

Heat transfer fluid

"Molten salt" power plants use molten salt, which can be heated to 565 degrees Celsius, as a heat transfer fluid. However, the melt can solidify if its temperature falls below about 245 degrees Celsius. Intelligent operating strategies are necessary to prevent this. In an emergency, the solar array heating ensures the necessary operational reliability, and the liquid salt can also be emptied into well-insulated containers and stored temporarily.

Power plant safety

Frequent starts and transitions to partial-load operation place loads on conventional coal-fired and natural gas-fired power plants. The components are exposed to frequent temperature changes of several hundred degrees. The technical regulations for power plants evaluate the fatigue loads on components purely mathematically. If a power plant component exceeds the allowable value of 100 per cent for fatigue, the test conditions are intensified. The regulations are now being adapted. They allow for differentiated, operation-accompanying investigation methods.

Funding programme

Since 2017, 15 research projects have been investigating bioenergy plants that work flexibly and across sectors. The German Federal Ministry for Economic Affairs and Energy made 6 million euros available for this purpose as part of the Biomass Energy Use funding programme. One focus of the research projects is on the combined generation of electricity and heat in small-scale CHP systems (useful heat around 100 kilowatt thermal). It is intended that energy from biomass shall play a balancing role in the transformation of the energy system and link different sectors such as...

Water flow power

Ocean current power plants work according to a similar principle to wind turbines. Turbines with a free flow around them use sufficiently strong water currents to generate electricity. There are nevertheless significant differences: because water has a higher density, the power produced by water flow at a given speed is a thousand times higher than power produced by air flow. That’s why rather gently flowing tidal currents are sufficient for producing electricity. By comparison, underwater rotors have to be able to absorb enormous bending moments.

Powerful laser

One of the most powerful lasers is used in geothermal energy. It has an output power of 30,000 watts. Laser beams used in industry are more than ten times less powerful with output powers ranging between 2,000 and 3,000 watts. These lasers are used to weld and liquefy steel. In geothermal drilling, the laser beams loosen the crystals in the stone. This creates cracks in the rock. The porous material can then be broken more easily and quickly with a mechanical drill.

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