Petri Penttinen

European Union climate goals aim to increase waste incineration instead of landfills. Incineration of waste increases the mismatch between heat production and consumption since waste is generated constantly but energy demand varies significantly between seasons. Seasonal energy storage is suggested to alleviate this mismatch. However, traditional seasonal storage options have not been cost-effective investments for energy companies. This paper explores the feasibility of a large cavern thermal energy storage in a large district heating system with waste incineration. First, 62 one-year optimisations for seasonal storage with varying size and power were conducted to determine the economic performance of the system. Second, the annual system emissions were estimated. The results show that even small capacity seasonal storage reduces system emissions significantly. Return on investment for the most profitable storage with a capacity of 90 GWh and power of 200 MW range between 3.6% and 9.4%, and the investment varies between EUR 43–112 M depending on costs. Seasonal energy storages are still not as profitable as traditional energy investments. This might change due to growing waste heat recovery and the rising cost of carbon emissions. Further research is needed into new business models for implementing large seasonal storages.

Demand side management can add flexibility to a district heating (DH) system by balancing the customer’s hourly fluctuating heat demand. The aim of this study is to analyze how different demand side management control strategies, implemented into different customer segments, impact DH production. A city scale heat demand model is constructed from the hourly heat consumption data of different customer segments. This model is used to build several demand side management scenarios to examine the effect of them on both, the heat producer, and the customers. The simulations are run for three different-sized DH systems, representing typical DH systems in Finland, in order to understand how the demand side management implementations affect the production. The findings imply that the demand side management strategy must be built individually for each specific DH system; the changing consumption profiles of different customer segments should be taken into consideration. The results show that the value of demand side management for a DH companies remains low (less than 2% in cost savings), having an effect mostly upon the medium loads without any significant decrease in annual peak heat loads. Also, the findings reflect that the DH pricing models should be developed to make demand side management more attractive to DH customers.