Integrated focal solar receiver with thermal storage with COFALIT – RESCOFIS

The device we are aiming to develop in RESCOFIS is made of a high temperature solar collector, an efficient thermal storage system, and a modified thermal insulating wall structure, that shall be able to resist thermally and mechanically to the cyclic behavior of the system. Our method to study this system will take place in three phases:

- A first functional analysis in order to make all the a priori efficient technical choices.
- A study coupling modelization software with an experimental device for each of our three aforementioned sub-functions, in order to separately optimize them.
- A last testing phase on a semi-industrial pilot device in order to validate the interaction between those sub-functions, while operating under a real solar cycle.

The solar collector and thermal storage will be made of a non-structured granular porous media, disposed in pebble bed. This media will be composed of materials produced by waste retreatment process. It allows us to keep a compact system, a low cost, while still being durable and green. The thermal fluid used to charge and discharge the thermal storage is atmospheric air, chosen for its cost, its stability at high temperature level, and its ecologic strengths.

Our first results allow to demonstrate the feasibility of the concept with a 1kW solar lamp: a 450°C hot air was produced. The importance of several technical parameters has been shown, and the production of a 600°C hot air should be possible on a semi-industrial pilot with a higher power level. Some last optimizations are yet to be finalized before designing, realizing and testing these pilot devices

As soon as our tests on the semi-industrial pilot devices are finished and positive, we should be able to design an industrial demonstrator which would allows us to standardize this kind of product for local applications.
The choice of an adapted thermo-electric converter has yet to be made, in order to obtain the best efficiency depending on the desired power level.

A poster was presented at JNES 2015, and a communication has been accepted at JITh 2015. Both communications concern the experimental studies about the solar collector part of the system, and the thermal storage part. Those studies were made using appropriated laboratory experimental devices.
RESCOFIS has been cited in a conference IDHELIO gave at the 9th Day of Research and Industry, presenting activities in the energy storage sector and chaired by ICAM Toulouse.

The RESCOFIS project (solar receiver integrated with thermal storage under focal concentration) aims to develop a solar receiver integrated with a thermal storage applied to Beam Down micro CSP power plants. The target market is aimed towards the small solar power plants for the 24/24 decentralized generation of electricity in the range of 10 to 100 kWe. The receiver and the thermal storage are based on a COFALIT granular bed passed by a stream of air at atmospheric pressure in order to reach temperatures up to 600 ° C. As the system is designed to be coupled with a Rankine cycle through a secondary heat exchanger, further developments will open the market of medium power CSP plants using Brayton cycles.
The RESCOFIS project, planned over a period of three years, deals with the development of design and analysis tools describing the concept of a receiver/storage particle bed. In the process, an experimental set-up of about 20 kWhth will be used to validate the key components of the receiver/storage and clear the underlying scientific and technological uncertainties. Finally, a 1:10 pilot scale system will be realized in order to validate the whole process during charge and discharge phases as well as direct valorization of the hot air with a heat exchanger powering a Rankine cycle.
The receiver and storage unit will be developed with an objective of versatility and standardization to promote easy industrial and commercial deployment.
One of the strength of the receiver/storage system developed in the RESCOFIS project is the use of air as a working fluid and COFALIT as a storage material for a low cost, low environmental impact and available solution. Implementation traversed bed is simple and ensures a good energy efficiency and exergy. Furthermore, the compact and simple design of RESCOFIS will ensures a good overall efficiency as well as a simplified installation and easier operation of the solar power plant.
The RESCOFIS project is supported by the IDHELIO Company based in Albi and a partnership between EUROPLASMA, supplier of the COFALIT material, the RAPSODEE laboratory, specialized in the study of solar thermal processes and which will provide its solar experimental Beam Down facility and the ICAM for its expertise in mechanical and material engineering applied to the study of the particle bed/envelope interactions.
In addition, the project is guided by a follow-up committee.