Wind energy integration with thermal energy storage

Abstract

Thermal energy storage is the present and future of the widespread integration and sustainability of renewable energy in this era of energy transition and a solution to the balance in energy demand and supply at different peak levels. A wind energy system combined with thermal energy storage deals with one of the major challenges in the use of wind and other renewable energy sources, that is, their variability.

This work had two main focus, the first was to optimise a time and size scale for thermal energy storage options, that is, hot water sensible heat storage, latent heat storage with PCMs and thermochemical heat storage. Research was carried out into the various storage options to determine relevant factors such as their storage capacities, power, efficiencies, storage periods and potential costs. The optimization results indicated that for medium to long term storage applications (days to months) with low storage capacities hot water sensible heat storage is more suitable, for short to long term storage applications (hours to months) with high storage capacities latent heat storage using PCMs is more suitable and for short to medium term storage applications (hours to days) with even high storage capacities thermochemical heat storage is more suitable.

The second focus was to determine a liquid storage material that will be the most suitable thermal storage material in terms of energy storage capacity, storage volume/size, and storage cost. This analysis was made for water (Hot water), thermal oil (Therminol VP-1) and molten salt (Hitec salt) based on a 117.3 MW Metsälä wind farm in Kristiinankaupunki, Finalnd. The analysis of the material properties such as minimum and maximum temperature, volume, density, specific heat capacity and cost per/kWh indicated that interms of storage capacity, storage volume/size and storage cost, molten salt (Hitec) is the most suitable thermal storage material among the three materials analysed.