Advantages from the integration of the Heating, Cooling and Power supply systems into one flexible energy supply system.

摘要

Today the supply of electric power is vital for the infrastructure in almost any society. Also, in many countries the supply of heat and cold are essential for the wellbeing of most inhabitants, though many different solutions to this problem exist. During the last decade in particular the electricity supply system has undergone many changes due to the deregulation of the market but also due to a public and political pressure to produce the power in more renewable and sustainable ways. Considering that many power production plants have not even closely reached their expected technical life time, typically between 25 and 40 years, the turmoil has had major economic consequences for the plant owners. In the years to come it is to be expected that even more renewable energy (RE) in the form of windmills, Photo Voltaic (PV), Solar Collectors (SC), geothermal and biomass will appear as production units in both the heat and the power grids. Such units are typically less controllable than conventional production units based on, say, coal but they will find their way. In Denmark, more than 30% of the annual electricity production comes from windmills; there have been periods in time where the production from wind mills has covered more than 100 % of the consumption and the power system still has not tripped. Many large cities have a long tradition of operating city-wide district heating (DH) systems. In high density areas a DH system makes sense as a convenient way of heat supply. In Denmark, DH systems are common and even in cities as small as 1000 inhabitants most of them living in detached houses it is typical with a consumer owned district heating system. Before the oil- crises in the 1970th , most of those systems were oil-fired. Since 1979 oil has been replaced by various other heat sources like surplus heat from Combined Heat and Power Plants (CHP), gas engines or various types of biomass (straw, wood chips or waste). In densely populated regions, large heat transmission systems have been established. The extension of the distribution grids and the transmission systems have been optimized to the benefit of the society and the consumers. In this paper we show that a system approach is a (or maybe the only) possible way to increase the robustness of both the power system and the heat supply system to a degree where they both can cope with large amounts of RE in a cost efficient way. One very important component for this to work is the thermal energy storages, which can store hot or cold water for several hours, weeks or even inter seasonal.