Excess renewable electrical energy for district heat

With European countries such as Germany and Denmark moving to very high levels (80 & 100% by 2050) of renewable energy for all energy uses there will be increasing periods of excess production of renewable electrical energy. Stockage of this energy as potential electrical energy e.g. pumped hydro, etc. is very costly, and round trip efficiency is reduced and should be minimized. But storage as heat in District Heating for use in buildings where there is demand is significantly less costly. Whilst the quality of the electrical energy is degraded, high voltage grid MW sized heat pumps would maximize efficiency whilst not wasting excess renewable electricity.

Use of solar heat for district heating has been increasing in Denmark and Germany in recent years. The systems usually include interseasonal thermal energy storage for a consistent heat output day to day and between summer and winter. Good examples are in Braedstrup and Marstal, Denmark. These systems have been incrementally expanded to supply 10% and 40% of their villages' annual space heating needs. The solar-thermal panels are ground-mounted in fields. The heat storage is, respectively, in a borehole cluster and a pit storage. In Alberta, Canada the Drake Landing Solar Community has achieved a world record 97% annual solar fraction for heating needs, using solar-thermal panels on the garage roofs and thermal storage in a borehole cluster.

Дата добавления: 2015-08-03