Optimization of Cogeneration by Seasonal Heat Storage in an Aquifer

Abstract

Aquifer Thermal Energy Storage (ATES) is a cost-effective and energy-saving technology associated with heating and cooling of buildings or districts. Particularly in combination with cogeneration systems, the overall system performance can be affected positively by storage and recovery of large quantities of thermal energy in the subsurface. ATES has developed from a demonstratio nstage to an established technology over the past decades. However, in Germany there are only three existing projects yet. Since 2010, there are plans to integrate an aquifer storage into an existing District Heating System (DHS) in Lueneburg, which is supplied by two cogeneration units. The hydrogeological conditions (e.g. water chemistry or thickness of the natural aquifer) at 450 m depth are matehing with the size of the DHS. With respect to financial aspects, seasonal energy storage in an aquifer reinforces the connection between thermal and electric energy systems due to cogeneration. Purpose of this paper is to demonstrate case studies based on energetic overall system performance considerations to evaluate future energy systems with ATES. A system comparison (with ATES and without ATES) indicates an increase of cogeneration by more than 20%. In the same way, the conventional heat production with natural gas decreases by 2.3 GWh/a while the generation of renewable electricity increases by 2.8 GWh/a.