DLR testing using molten salt in a solar energy plant in Portugal

• Designers from the German Aerospace Center have actually taken a vital step in the direction of using molten salt as a heat transfer medium in parabolic trough solar energy plants.

Together with the University of Evora and also industrial companions, a group from the DLR Institute of Solar Research has for the first time begun running the solar field of the Evora parabolic trough test plant in Portugal with molten salt.

This innovative technology is assisting to better decrease the expenses of operating solar thermal power plants. With their integrated storage systems, solar thermal nuclear power plant are the only technology able to create large quantities of power from solar energy around the clock.

Present cutting edge business parabolic trough power plants make use of an unique thermal oil as the heat transfer medium. The oil absorbs concentrated solar radiation gathered utilizing mirrors, converts it right into heat and transfers it by means of pipes to a heat storage unit or a steam generator to create electrical energy. The heat storage tank, loaded with molten salt, can hold the thermal energy at temperatures of approximately 560 degrees Celsius for a period of 12 hrs and launch it again when the demand for electricity rises.

The nuclear power plant requires heat exchangers to move the heat from the oil to the salt in the storage tank, however some energy is always lost throughout this transfer before it can later be exchanged power. The optimum feasible operating temperature level of the oil made use of is approximately 400 degrees Celsius, which limits the efficiency of the energy conversion. Researchers and industry are for that reason searching for methods to more boost the temperature levels in solar energy plants in order to lower the prices of electrical power generation.

One appealing method to raise temperature levels in parabolic trough power plants is to utilize molten salt not just as a heat storage medium, yet also as the heat transfer medium in the collection agency field. Depending on the composition of the molten salt, it can hold up against significantly greater temperature levels than thermal oil - as much as 565 degrees Celsius One more advantage is that the storage tanks can be filled up straight with molten salt from the solar field - removing the requirement for a heat exchanger.

In order to demonstrate this technique, the DLR Institute of Solar Study, together with the University of Evora as well as firms from Germany as well as Spain, has been constructing a solar parabolic trough examination facility making use of molten salt as its heat transfer medium. The work began in 2016 and also has occurred as part of the High Performance Solar 2 (HPS2) research project, which is moneyed by the German Federal Ministry for Economic Affairs as well as Energy (BMWi). The purpose of the project is to show that parabolic trough power plants can be operated safely as well as economically with molten.

A technical challenge when making use of molten salt as a heat transfer fluid is that heating of all the pipes is necessary. To avoid the molten salt from strengthening as the plant is filled, electrical trace home heating should be utilized to pre-heat all salt-carrying components.

Successful initial dental filling and also examination operation of the system at 300 degrees Celsius.

The collection agency components of the HelioTrough 2.0 generator from project companion TSK Flagsol, which are currently loaded with molten salt and attached to every various other, give an overall thermal output of as much as 3.5 megawatts throughout a complete size of 684 metres.

Presently, the plant operates with a ternary salt blend from the project companion Yara, which has the advantage of a lower melting temperature contrasted to a binary salt solar salt combination as well as can absorb warm up to a temperature of approximately 500 degrees Celsius. Along with its usage in solar thermal power plants for electricity generation, this salt combination is likewise of interest for solar process heat supply systems.

Starting from an initial temperature of 300 degrees Celsius, the designers wish to progressively enhance the operating temperature level approximately 500 degrees Celsius. In the coming weeks, the other components of the salt circuit will certainly be brought into operation in Evora. In addition to the two-tank storage system, this consists of the heavy steam generator and also the dimension tools.

" We are really completely satisfied with the way the first filling went. Our next goals are to get operating experience, fill up all further components with molten salt detailed as well as examination normal operations as well as also critical running circumstances," states Jana Stengler, head of the Fluid Systems Group at the DLR Institute of Solar Research Study, on the results of the first testing.

The HPS2 plant is created to likewise be run with solar salt, a combination of potassium nitrate as well as salt nitrate, to achieve even greater temperatures of up to 565 degrees Celsius. Greater temperatures in the solar area allow for higher performances in the conversion of solar power into heat as well as heat into electricity, which reduces the price of producing electrical energy.

" Power plants utilizing the technology from HPS2 can be developed more easily and also run a lot more effectively. This minimizes electrical power production costs by approximately 10 percent," claims Mark Schmitz from the project partner TSK Flagsol, underscoring the relevance of the project for future solar thermal power generation. "That is a substantial step for a solitary technical adjustment. At the same time, it makes longer storage space durations of 12 full-load hrs and even more economically possible."