Report from CSPPLAZA
Fraunhofer is Europe’s largest application-oriented research organization.
On CSPPLAZA2015 annual Conference held by CSPPLAZA, Dr. Tom Fluri – Head of Group Solar Thermal Power Plants and High Temperature Storage, at Fraunhofer Institute for Solar System ISE , gave a presentation titled “Freeze Protection Strategies for Line Focusing Systems with Mloten Slat as Heat Transfer Fluid”. Recently, CSPPLAZA had a interview with Dr. Tom Fluri, regarding issues about LTM(lower- melting -point) Salt.
photo: Dr. Tom Fluri gives presentation on CPC 2015
CSPPLAZA: In your opinion, what are the main reasons for the inexistence of any large scale commercial projects with line focusing systems using molten salt as heat transfer fluid?
Tom: It is mainly an issue of risk perception by the investors. Some very significant experience has been gained mainlyby ENEA/ENEL in Italy for parabolic trough and Novatec Solar in Spain for linear Fresnel. To achieve attractive financial conditions for future commercial projects, a large demonstration is now required for linear Fresnel.
CSPPLAZA: Related institutes make R&D and demonstration for molten-salt technology in parabolic trough and fresnel linear Fresnel technology. Which one of the two types is easier to make breakthrough in commercial application? Which one enjoys a more promising future prospect?
Tom: While Fresnel has some technical advantages, e.g. absence of moving joints in piping and higher concentration ratio, there are currently only few companies pushing this concept into the market. If parabolic trough technology providers manage to bring down cost, I think it will be more successful due to its higher optical efficiency and its higher market penetration.Linear Fresnel may compensate for the lower efficiency through higher cost reduction potential.
CSPPLAZA: In your presentation on CPC 2015, you mentioned two types of lower-melting point salt Hitec and HitecXL. So who is the manufacturer of the two products?
Tom: Hitec and HitecXL are mixtures of three components which are usually supplied by different companies.
CSPPLAZA: Are there any applied examples of them?
Tom: Hitechas been used in the Themis plant, a central receiver system.
CSPPLAZA: One significant disadvantage of lower-melting point salt is its high cost. So are there any solutions to cost reduction?
Tom: To my knowledge lower-melting point salts are not significantly more costly than solar salt.
CSPPLAZA: What are your suggestions on production of lower-melting point salt product?
Tom: The components of the mixtures should not require big efforts to comply with environmental protection regulations,should be compatible with steel, should be available at a reasonable cost and should have an acceptable viscosity at low temperatures.
CSPPLAZA: One technical difficulty for parabolic trough is the requirement for temperature resistance ability of receiver: bearing a temp. ＞500℃. So currently, are there mature collecting products that can bear such temp.?
Tom: The acceptable temperature range is determined by the performance and the durability of the selective coating. Currently there are high-temperature receivers suited for molten salt application in the market supplied from leading manufacturers. They have been tested in existing projects,.
CSPPLAZA: I learned that you are involved in research of collector. How far is it for the receiver products to enter commercial application?
Tom: The Archimede Plant in Siciliy is a first commercial plant.
CSPPLAZA: It is said that the issues of freeze protection for line focusing system is a matter of economic feasibility, rather than technical matter. How do you see such saying?
Tom: Gas use may be an economic barrier but can be reduced by adequate measures, such as using heat from the storage as presented earlier.
CSPPLAZA: In your presentation, you mentioned four measures for freeze protection: LMT salt mixture, high yield collector, alternative heating source and drainage. Are all four of them feasible in practical projects?”
Tom: For large plants drainage may be difficult to implement, but the other three are valid proposals also for commercial projects.
CSPPLAZA: In china, you have conducted cooperation with Royal Tech CSP, how about the specific field of your cooperation?
Tom: We support Royal Tech with our experience in CSP yield assessments for parabolic trough, linear Fresnel and tower technology with different kinds of HTF, like molten salt, synthetic oil and direct steam generation. Together we offer yield assessments to other players in China. By using a simulation tool sourced from our cooperation, we calculate the energy yield of CSP plants with different configurations, evaluate the economy and provide a comprehensive assessment report to our clients.
CSPPLAZA: In terms of your LMT salt as solution to freeze protection, how do you cooperate with Chinese customers in this aspect?
Tom: We can offer support in system simulation and optimization to identify the most suitable solution for their projects.
CSPPLAZA: In what levels and aspects are you intending to cooperate with Chinese customers?
Tom: Yield assessments are our focus at this point in the Chinese market. Eventually we hope to see more transcontinental R&D collaborations between European industry and Chinese players. We could offer our R&D services to such collaborations ranging from joint component development to system simulation and optimization.
CSPPLAZA: Firstly, I would like to congratulate on your moving to a bigger lab dedicated to investigation of molten salt components (inauguration on 2nd July 2015). Compared to the former lab, what has been improved in this new lab?
Tom: We are now able to operate at higher temperatures of up to 550 °C to investigate sensible heat storage concepts and components. Commissioning of this high temperature loop will start shortly. Previously we focused on the development of PCM storage for direct steam generating CSP plants, an activity we would also like to pursue in the future.
CSPPLAZA: And what about your keys and emphases on heat storage research in the future?
Tom: We are proud to be part of the recently kicked-off EU project ORC-PLUS, in which we will assess and optimize the performance of single-tank storage solutions in our lab and in a demonstration plant in Morocco.