Network of International Society for Low Exergy Systems in Buildings
The necessity for an increase in the efficiency of energy utilisation in buildings is obvious and indisputable. Heating, cooling and lighting appliances in buildings make up more than one third of the worlds primary energy demand . Thus, building stock is a major contributing factor in energy related environmental problems. The growing concern of environmental problems, such as global warming, connected to the extended use of energy, implies both the importance of all kinds of so called "energy saving measures, and the necessity for an increased efficiency in all forms of energy utilisation. Both of these matters are affected by the energy efficiency of the built environment and the quality of the energy carrier in relation to the required quality of the energy. Taking into account qualitative aspects of energy leads to the introduction of the exergy concept in the comparison of systems. Energy which is entirely convertible into other types of energy is exergy (i.e. high valued energy such as electricity and mechanical workload). Energy, which has a very limited convertibility potential, such as heat close to room air temperature, is low valued energy. Low exergy heating and cooling systems use low valued energy, which is delivered by sustainable energy sources (e.g. by using heat pumps, solar collectors, either separate or linked to waste heat, energy storage, etc.). Common energy carriers, like fossil fuels, deliver high valued energy.
Future buildings should be planned to use or to be suitable for the usage of sustainable energy sources for heating and cooling, and the design of those systems should be made in regard to the building construction itself. A good level of thermal insulation and effective solar shadings are mandatory for an optimised design. One characteristic of these energy sources in focus is that only a relatively moderate temperature level can be reached, if reasonably efficient systems are desired. The development of low temperature heating and high temperature cooling systems is a necessary prerequisite for the usage of alternative and renewable energy sources. The basis for the needed energy supply is to provide occupants with a comfortable, clean and healthy environment.