Ancillary services for the electrical grid by waste heat

This paper proposes a method to provide ancillary services to the electrical grid with waste heat recovery. The thermal flexibility needed to provide variable electrical output is provided by connecting the thermal source to a thermal grid and a thermal storage unit. Large capacity low heat grade thermal storages are cheaper and more readily available than large capacity electrical storage solutions, and hence thermal storage is preferable.In this paper, the dimensions of a low temperature thermal storage buffer to balance the variability of a wind- or solar plant is determined. It is calculated that a spherical storage tank of 25 m diameter and 90–130 °C would be sufficient to balance the unpredictability of a 100 MW plant of either solar- or wind energy.