Periodic Reporting for period 2 - AMADEUS (Next GenerAtion MateriAls and Solid State DevicEs for Ultra High Temperature Energy Storage and Conversion)
Berichtszeitraum: 2019-01-01 bis 2019-12-31
The targeted breakthrough of AMADEUS project is to develop novel materials and devices that enable energy storage and conversion at ultra-high temperatures, well beyond 1000 ºC. For this, AMADEUS is investigating phase change materials (PCM) based on silicon-boron binary (Si-B) and ternary (Si-B-X) alloys, with potential to surpass 2 MJ/kg of energy density. The most relevant technological challenges concerning the use of these materials are also being investigated, such as the refractory linings of the container, advanced thermal insulation casing, and hybrid thermionic-photovoltaic (TIPV) converters able to produce electricity from heat at those ultra-high temperatures.
Concerning the development of a TIPV energy converter, the different constitutive elements have been individually developed and optimized. First, an emitter able to effectively radiate electrons has been accomplished by depositing thin layers of lanthanum hexaboride (LaB6) on tantalum substrates, resulting in work function of 2.6 eV and thermionic current density of 1.5 A/cm2 at 1650 °C. Ultra-thin (~ 1 nm) BaF2 layers on semiconductor substrates have resulted in very low work function of 2.1 eV. These layers will be eventually deposited on the PV cell to enable the collection of electrons. The PV cell and the emitter will be separated by micron-gap distances by means of ZrO2 micro-spacers, which have already demonstrated both thermal and electrical insulation. PV cells based on GaAs and InGaAs semiconductors have been manufactured, demonstrating open-circuit voltages beyond 1 V (for GaAs) and 0.5 V (for InGaAs), as well as photogenerated current densities as high as 60 A/cm2 (for InGaAs). Both two-terminal and three-terminal PV devices have been fabricated, which will eventually lead to two different proof of concept experiments. To characterize the converters at high temperatures, new vacuum systems have been developed. Preliminary experiments in one of these systems have been able to demonstrate a voltage boost of TIPV with respect to a reference device using a non-PV p-type GaAs anode. This PV enhancement represents the first proof of concept of a TIPV converter. Current activities are directed towards the integration of all these optimized elements in a final device. Very preliminary results indicate that the use of micro-spacers and the incorporation of BaF2 coatings are able to effectively produce an increment of the operation voltage, as expected.
Owing to the novelty of the concepts involved and the challenges addressed, this project aims at initiating research on a radically novel technology for energy storage, establishing its proof-of-principle. Thus, it is the aim of this project positioning this technology in the future roadmaps of energy storage, together with other well-known solutions such as batteries, super-capacitors, fly-wheels, etc. This technology has the potential of providing one of the highest energy density storage solutions. Hence, it is aimed at causing an impact on several sectors of the economy, such as energy generation (new generation of solar thermal power plants) and transmission (enlarging the share capacity of other renewable energies and reducing the transmission and distribution costs by facilitating more efficient grid management).