Pebble bed regenerator and storage system for high temperature use

The situation on the energy market in the EU countries, especially in Germany, is in a changing process. An increasing amount of wind and solar power plants is feeding renewable, but fluctuating energy into the grid especially in Germany. Thus balancing power is needed. Combined heat and power plants (CHPs) are mostly operating heat driven at the moment. Fraunhofer UMSICHT is researching a new concept of external superheating for CHP with biomass and waste fuels for increasing electrical efficiency and additional storage option for decoupling heat and power generation in order to supply the electrical grid with power on demand. Therefore the main component for this superheating concept, the so-called Pebble-Heater, has been developed. It is a pebble bed regenerator and storage system for high temperatures, which can be used in combined heat and power plants (CHPs). Theoretical examination of the Pebble-Heater performance has been accomplished at the test facilities of Fraunhofer UMSICHT during the last years. Especially the temperature profile inside the pebble bed has been simulated. The results of the Pebble-Heater test rig with a storage capacity of approximately 80 kW h at temperatures up to 1200 °C are presented in this paper. The temperature profile inside the pebble bed combined with a low pressure drop have shown the potential to implement the Pebble-Heater for high temperature usage.

► Pebble-Heater as high temperature storage for temperatures up to 1200 °C.
► Use of bulk materials for sensible heat storage.
► Examination of temperature profile in a pebble bed.
► High thermal efficiency up to 95% for gaseous media.
► Low pressure drop due to radial flow direction in Pebble-Heater.