The integration of renewable energy in the electrical grid is challenging due to specific problems mainly related to the intermittent and non-programmable generated electric power and to the transmission of peak power levels. In the last decades, several energy storage technologies have been studied to find a solution to these issues. In particular, compressed air energy storage (CAES) plants work by pumping and storing air into a vessel or in an underground cavern when excess or low-cost electricity is available. Then when energy is needed, the pressurized air is expanded in an expansion turbine. Several CAES configurations have been proposed: diabatic, adiabatic and isothermal. The only two operating CAES plants worldwide are based on the diabatic method, but to improve the efficiency of the process the isothermal configuration seems to be the most promising. It differs from conventional CAES approaches as it employs near-isothermal compression and expansion and therefore requires heat to be removed continuously during the compression phase and added continuously during the expansion. Currently there are no commercial isothermal CAES implementations worldwide, but several methods are under investigation. In this paper, the use of phase change materials (PCM) for isothermal air expansion is discussed. Air expansion tests in presence of PCM were carried out in a high-pressure vessel in order to analyze the effect of PCM on the process. Results show that in presence of PCM near isothermal expansion conditions occur and therefore they affect positively the value of the obtainable expansion work.
Experimental investigation on the effect of phase change materials on compressed air expansion in CAES plants
CASTELLANI, BEATRICE;PRESCIUTTI, ANDREA;MORINI, ELENA;FILIPPONI, MIRKO;NICOLINI, ANDREA;ROSSI, Federico
2015
Abstract
The integration of renewable energy in the electrical grid is challenging due to specific problems mainly related to the intermittent and non-programmable generated electric power and to the transmission of peak power levels. In the last decades, several energy storage technologies have been studied to find a solution to these issues. In particular, compressed air energy storage (CAES) plants work by pumping and storing air into a vessel or in an underground cavern when excess or low-cost electricity is available. Then when energy is needed, the pressurized air is expanded in an expansion turbine. Several CAES configurations have been proposed: diabatic, adiabatic and isothermal. The only two operating CAES plants worldwide are based on the diabatic method, but to improve the efficiency of the process the isothermal configuration seems to be the most promising. It differs from conventional CAES approaches as it employs near-isothermal compression and expansion and therefore requires heat to be removed continuously during the compression phase and added continuously during the expansion. Currently there are no commercial isothermal CAES implementations worldwide, but several methods are under investigation. In this paper, the use of phase change materials (PCM) for isothermal air expansion is discussed. Air expansion tests in presence of PCM were carried out in a high-pressure vessel in order to analyze the effect of PCM on the process. Results show that in presence of PCM near isothermal expansion conditions occur and therefore they affect positively the value of the obtainable expansion work.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
