Storing energy and controlling the electricity grid using high-performance buildings
It is mainly during periods of strong wind in winter that the German electricity grid provides an over-supply of electricity, which results in very low or even negative prices at the electricity exchange. The aim of the research study is to develop concepts for »Buildings heated by wind-power«, which are heated during periods of strong wind only. The thermal energy stored inside these buildings can be provided for such a long time that practically no additional energy is needed for DHW and space heating purposes.
The climate in Northern Germany is analyzed, typical back-up power periods (1 to 2 weeks) are identified. The stock of existing buildings is analyzed; a typical single-family home and a typical office building (i.e. one new building and one retrofitted building in each category) are defined. The amount of thermal energy required by these four buildings during the back-up power periods (when no wind is available) is then determined using transient building simulation software (WUFI® Plus). A matrix of potentially expedient combinations of technical building systems (generator, storage facility, control/emission) is prepared. For each of these combinations, the theoretical storage capacity is calculated and compared to the demand of the specific building (Fig. 1). Only those combinations of buildings/ technical systems are eligible that promise to be economically efficient and cover the demand for wind power by more than 80 percent. Subsequently, the selected combinations will undergo detailed dynamic simulations (in conjunction with the associated building services systems) to be compared and evaluated in terms of wind power coverage, environmental criteria and life-cycle costs (LCA).
To become economically feasible, such solutions require highly energy-efficient residential buildings and low electricity prices. Large water tanks and thermal activation of building components seem to be expedient storage solutions. Regarding thermal activation of building components, further work is necessary to optimize the control strategies (based on weather forecasts, for instance). A central, electrically heated high-temperature rock bed storage (Fig. 2) - comparable to a night-storage heater - seems to be another promising option with technical and economic potential.