The design for direct steam generation, which was implemented commercially for the first time at TSE 1, offers the advantage of using solar radiation to heat water directly in an absorber tube, which produces the steam required to run the turbine. After developing and testing this design at three test and pilot facilities with the help of experts from the German Aerospace Centre, Solarlite GmbH is now implementing it in commercial projects.
Solarlite’s technology is particularly environmentally-friendly and efficient.
Because the technology uses water instead of the commonly used thermal oil as a heat transfer fluid, components such as heat exchangers are not needed. But most importantly, direct steam generation allows higher operating temperatures of up to 500°C, in contrast to the 395°C made possible using thermal oil. For that reason, parabolic trough plants are clearly more efficient and thus better performers in the long run. Not to mention, these power plants are especially environmentally-friendly because they do not require thermal oil, an expensive and dangerous component in limited supply. Lower CO2 emissions are another noteworthy feature: 964 t/year less than oil and 1,258 t/year less than coal.
Simple solar field design, complex controls
Direct steam generation requires a complex control and regulating system to control and maintain the pressure and temperature. Solarlite uses a combination of recirculation and injection technology. That way, steam is continuously reintroduced into the water cycle so that the pressure remains stable. TSE 1 has an operating temperature of 330°C with a pressure of 30 bars. “We are already working on developing this technology further. Our current project, the TSE 2 power plant, will reach an operating temperature of 400°C with 40 bars," says Joachim Krüger, CEO of Solarlite GmbH.
In the joint research project known as “Duke” that is supported by the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, Solarlite GmbH and the German Aerospace Centre are testing a new version of direct steam generation that will make it possible to cut energy costs even more.
Solar thermal power plants with great potential
In collaboration with Thai Solar Energy Co., Ltd., the investor and operator of TSE 1 and TSE2, Solarlite GmbH is planning to build a total of 15 power plants with a combined output of 135 MW. Joachim Krüger explains: “Solar thermal power plants use the sun as an energy source in a very efficient way. They are definitely at least 25% more efficient than photovoltaic power plants.”
The efficiency of parabolic trough plants can be further increased in, for example, co-generation applications with simultaneous electricity and thermal energy usage, or when energy storage solutions are integrated. In addition, there is potential for hybrid solutions with other renewable energy sources. “This technology has a broad range of applications. The fact that energy costs can be reduced over the long term and that we can free ourselves from fluctuating prices are real opportunities for industry," adds Joachim Krüger.
Solarlite GmbH develops and builds decentralized concentrating solar-thermal parabolic trough plants (CSP – Concentrated Solar Power) for combined heat and power generation (steam, thermal energy and power). These power plants have an electrical output in the range of 500 kWe up to more than 30 MWe. Solarlite is globally the only supplier of parabolic trough plants that can be used in different applications such as electricity production or for the stand-alone electricity consumption of small and medium-sized industrial facilities. Compared to traditional parabolic trough collectors that use thermal oil and an additional heat exchanger, the direct steam generation implemented by Solarlite is more efficient, less expensive and more environmentally friendly. Solarlite was founded in 2007 by Joachim Krüger.