Blueprint for future solar tower power plants to accelerate development
In the future, solar thermal power plants with integrated storage facilities can take over the task of baseload supply from coal-fired power plants in sunny regions. In order to accelerate the deployment of solar thermal power plants, DLR and German partner companies from industry have designed a solar tower power plant which can serve as a blueprint for future solar power tower plant projects.
Power plants with thermal storage also supply solar power at night
Green electricity is an essential part of the energy transition. But solar radiation fluctuates and is not available at night. With the increasing share of fluctuating energy sources like solar and wind in energy systems, the importance of energy storage and demand-based power generation is therefore growing.
In solar thermal tower power plants, up to several tens of thousands of mirrors redirect solar radiation to the top of a tower. A special heat transfer medium, for example molten salt, absorbs the concentrated solar energy in the form of heat. It conducts the heat from the top of the tower to a connected steam power plant or to heat storage tanks filled with liquid salt. The power plant can extract the hot salt at any time and can use the stored heat to drive the steam turbine to generate electricity.
Solar tower systems offer higher potential
Compared to the more widespread parabolic trough systems using thermal oil, solar tower systems offer higher potential due to the higher possible temperatures of the heat transfer medium salt, especially in the utilisation of thermal storage and achievable conversion efficiencies from heat to electricity.When the sun is shining, photovoltaic systems can produce solar power at a lower cost than solar thermal systems with integrated heat storage. During periods without sun, solar thermal power plants are superior to them because, at the current state of the art, it is cheaper to store thermal energy in liquid salt than to store large amounts of electricity in batteries. They are a valuable complementary addition to PV plants without storage.
In designing the blueprint, the team of engineers and researchers therefore chose a solar tower plant and considered two typical modes of operation after sunset:
1. The power unit produces electricity from sunset and operates at full load until sunrise the next day, provided that the storage system can deliver sufficient heat. (night operation)
2. The power plant unit starts at sunset and operates at full load until midnight or until the storage tank is empty. (peaker operation)Based on these basic scenarios, planning companies can adapt the operating mode to the specific site and for specific power plant projects.
Quality "Made in Germany" for power plants worldwide
In their concept study, the energy experts from MAN Energy Solutions SE, sbp sonne GmbH, Steinmüller Engineering GmbH and Tractebel Engineering GmbH developed a power plant that is technically, economically and ecologically superior to previous solutions. The subsystems of the power plant come from German manufacturers.
The project team members contributed their respective expertise to design the best possible subsystems. This approach was based on the idea that the most economical plant consists of the most economical subsystems - provided that they are integrated into the overall system in the best possible way and that the system is adapted to the respective demand.
Concept study results
The company sbp Sonne GmbH calculated that a mirror field with a total mirror area of 1.5 square kilometers would be the most economical for the power plant. At sites suitable for solar tower systems, this field size is sufficient to supply a solar receiver with 700 megawatts of thermal output with solar radiation.
MAN Energy Solutions SE recommends a turbine with an electrical output of 200 megawatts that can be started and stopped daily for the power plant unit. Using yield calculations for the reference power plant at the example site in Morocco, researchers from DLR calculated which heat storage size would enable the lowest electricity generation costs. Steinmüller Engineering GmbH designed the steam generator and Tractebel Engineering GmbH was responsible for BOP, buildings, risk analysis and bankability.
Project manager Jürgen Dersch from the DLR Institute of Solar Research: "This blueprint is intended to support project development companies and future power plant owners in planning and designing power plants and preparing tender documents. At the same time, it demonstrates the expertise of the industry partners involved." These are reasons why the German Federal Ministry for Economic Affairs and Energy funded the study.
The calculated costs for nighttime electricity range from 8.9 to 12.4 eurocents per kilowatt-hour for operating the system from sunset to sunrise and from 13 to 18.2 eurocents for peaker operation. The range of values results from different assumptions for financing and lifetime. The higher electricity production costs of the system for peaker operation are due to the fact that it requires two power plant blocks with 200 megawatts each. The system designed for complete night-time operation, on the other hand, manages with just one power plant block.
The final report of the study is available for download in DLR’s electronic library elib.
Multifocus Tower at "DLR Institut für Solarforschung" in Juelich
At the Juelich Multifocus Tower testing of an innovative solar tower receiver is about to begin. By using molten salt as heat transfer media in the solar receiver, higher operating temperatures are achieved, reducing the cost of electricity generation.
"Our receiver is designed for an outlet temperature of 600° C. So the design goes well beyond the state of the art of 565° C. We now want to demonstrate this temperature in practice," says project manager Miriam Ebert, explaining one of the key features of the new prototype. The solar receiver manufactured by MAN Energy Solutions was installed on the first test level of the multifocus tower. The towers’ infrastructure allows the system to be tested under conditions similar to those of a real solar power plant. The goal of the project is to further improve the economics of molten salt receivers and thus the overall power plant. Christian Schuhbauer, Head of New Technologies in Deggendorf, explains the importance of this work: "The tests enable us to make a solid economic assessment of the technology. We will be able to use the results in the bidding process for commercial projects with molten salt solar receivers."
|Customer:||DLR German Aerospace Center|
|Customer type:||Research Center|
|Application:||Solar Tower Receiver|
|Location of installation:||Jülich, Germany|
|MAN's work scope:||Equipment supply|