Abstract
European industry accounts for approximately 20% of total European CO2 emissions, with heat demand representing one of the largest energy consumers. Solar thermal collectors offer an efficient renewable alternative to fossil fuels to cover the heat demand. However, due to the temporal mismatch between the solar thermal generation and process heat generation a thermal storage is needed to maximize the renewable utilization. This article presents a novel optimization framework for integrating an ideal heat storage with solar thermal systems in multiperiod heat exchanger network synthesis. We derive an analytical approach to optimize the heat storage by using physical insights from Pinch Analysis: heat can only charge the storage below the lowest pinch point in a given period and discharge above the highest pinch point. We show both how to do it for a storage of infinite size and of finite size, and that the infinite size storage is much more efficient to solve. The approach is validated using real industrial data from a lubricant plant and optimizing the implementation of solar thermal at the plant. By increasing the size of the storage more of the solar thermal heat is utilized, however, the increase in utilization becomes smaller as the storage becomes larger. While 100% solar thermal heat utilisation requires a storage size of 1040 kWh, 90% utilisation can be reached with a storage of 250 kWh, compared to only 70% without a storage.