Energy storage is one of the most attractive options for mitigating the impact of intermittent renewable energy generation on the electricity grid. This is demonstrated by the efforts currently being made by different sectors.
Projects:
PROTERMOELEC
Prototype and modeling of packed-beds integrated in thermal systems for electricity storage. Financing entity: Spanish Research Agency. Total budget: 250.000 € for TE4S group.
Among the alternatives, PTES (Pumped Thermal Energy Storage) technology seems promising for balancing the grid. It has the advantages of storing at high energy density with high efficiency (60%) and a relatively low cost per unit of energy (LCOS lower than batteries). It could reach power in the order of 100 MW, with storage capacity of about 10 hours (500 MWh). Investment costs are moderate compared to other technologies, and there are no geographical restrictions such as for hydro pumping or CAES (Compressed Air Energy Storage).
PTES systems store electricity when there is generation surplus (valley prices) and deliver it back when demand is high. They are charged by a heat pump cycle (reverse Brayton), storing the energy in TWO sources (one hot at the compressor outlet, and one cold at the expander outlet). To recover the energy, the cycle operates as a closed Brayton cycle. Thermal storage is carried out in rock beds, for being economical. In the first stage of the project, the study will focus on the implementation of a PTES prototype (5 kW, some hours of storage) and the analysis of the dynamic operation of the packed-beds, duly instrumented. In a second stage, design will be optimized based on techno-economic considerations and lessons learned to minimize LCOS.
Modelling and New Designs in Stratified Water Accumulators
Modelling of large erected stratified water tanks (hot and cold). Numerical simulations and optimization of the inlet diffusers. Funding entity (private contractor): ARANER TECNOLOGÍAS, S.L. Total budget: 24.000 € (2015).
Modelling of a thermal storage battery
2-D numerical modelling of heat storage in solid rocks thermal batteries. Geometry optimization under non-stationary hot gases flux. Funding entity (private contractor): PROMAT, S.L. Total budget: 6.000 € (2015).
Patents:
Procedimiento y sistema de almacenamiento de energía
A Lecuona, PA Rodríguez, JI Nogueira, M Legrand, R Ventas, MC Rodríguez Hidalgo. N. de solicitud: P201430907 País de prioridad: España Fecha de prioridad: 13/06/2014. Entidad titular: Universidad Carlos III (90%) y Universidad Politécnica de Madrid (10%).