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Direct energy conversion in combination with Concentrating Solar Energy (CSP) is a promising combination to go to higher efficiencies. The Alkali Metal Energy Converter (AMTEC) is such a device developed several years ago at KIT-INR. The ATEFA (AMTEC Test Facility) is aimed at further investigation and development of AMTEC converter. ATEFA is designed to operate in a wide temperature range of 600 – 900 °C and up to 0.5 bar overpressure (see Figure 1). For safety reasons the facility is sheathed by stainless steel.

The AMTEC test cell is divided through the BASE (ceramic electrolyte) in two main regions. The inner side of the BASE tube is filled up with liquid sodium, which serves as anode, and heated up to high temperatures 600 – 800 °C. At the moment AMTEC cell and facility are under construction and will be ready in autumn 2015 for the first measuring campaign.

On the way to obtain a mature design of the AMTEC converter for the industry, still many aspects need to be investigated and optimized. The two primer drawbacks of the cell are i) low cell efficiency (~ 20 %) in contrast to the high theoretical efficiency (~ 40 %) and ii) fast power degradation in time. Both are strongly bound to electrolyte and cathode. The electrolyte is responsible for ~ 60 % of the power loss while the electrode is in charge of the ~ 20 %. Regarding the cell efficiency, a fundamental part is lost through heat radiation and conduction. The ion conductivity of the BASE needs to be likewise taken into consideration as well as the electrical losses in electrode, current-collector and leads. Furthermore, alternative solutions need to be found for the joining between the ceramic BASE and the metallic structure of the cell. The junction must withstand temperatures of 800 – 1000 °C in a corrosive medium, which is an issue that has not been solved yet for long-standing cells.

The main objectives of the project are:

  • Regain of know-how available at INR (~ 10 years of experience in testing several AMTEC prototypes)
  • Design and construction of the AMTEC test cell and ATEFA facility
  • Development of a ceramic-metal joining for high temperatures (800 – 1000 °C)
  • Study and test surface coating materials on BASE (electrodes)
  • Study and test current collector structures / materials
  • Thermo-mechanical analysis of AMTEC cell
  • Analysis of the electrochemical properties of AMTEC cell
  • Study of electrical performance of AMTEC cell
  • Development of a data acquisition and control system for ATEFA



[1] W. Hering, R. Stieglitz, Th. Wetzel, “Application of liquid metals for solar energy systems”, EPJ Web of Conferences 33, 03003 (2012).

[2] A. Onea, N. Diez de los Rios, W. Hering, R. Stieglitz, P. Moster, “Direct energy conversion using liquid metals”, EPJ Web of Conferences 79, 03010 (2014).