Lateral thinking on storage. Getting the most when it is empty

Abstract

High penetration of cheap but non dispatchable renewable generation technologies, like Wind and PV, along with the progressive decommissioning of conventional power plants arise fundamental concerns on policy makers and electrical system operators. The main issue is whether the fleet of generation units will be able to respond to the demand needs, particularly at the times of peak demand. In addition, generation fleet consisting mostly of variable renewables will create other important concerns in terms of grid stability and affordable ramps for the backup plants. Apparently, there are only two renewable technologies that most likely have their resource ready at any time for delivery, hydro and biomass, but their possibilities to significantly increase their shares are rather limited. Some people still think that the missing piece of renewable technologies is the seasonal storage, but the true key point is not exactly this but being ready when requested. And this is precisely what STE/CSP plants in sunny countries can offer with a smart use of their invaluable treasure: the thermal storage. STE plants could respond to the request of the system operator at full nominal power at any given time, independently on whether the request is made in a sunny day or after a long row of cloudy days, just by keeping a part of the storage capacity available for this service. In sunny days of summer months there is no doubt at all regarding the availability of STE production, but in winter, autumn and spring days there is a part of the storage, which is not used in the daily charging and discharging process, that can be used as a kind of strategic reserve. This non-explored operational feature is presented here.