System expense figure

from Wikipedia, the free encyclopedia

The system expenditure figure (symbol ) describes the ratio of primary energy expenditure to the desired benefit ( energy requirement ) of an entire system for space heating, ventilation and hot water heating.

The system expenditure figure indicates the energetic efficiency of the entire energy supply chain, from the extraction of natural resources to the transfer of heat by radiators or other heat exchangers. The lower its value, the more efficiently the system works. It is mentioned for the first time with DIN 4701-10. Since the EnEV 2012 came into force, DIN V 18599 can also be used to determine any building-specific useful output. In residential buildings as well as in non-residential buildings in which electrical energy, e.g. B. by photovoltaics, generated or actively cooled (e.g. with refrigeration machines), this method takes into account the proportion of free and also less emissions producing energy conversion processes.

The system expenditure figure depends on the type of fuel used , the use of regenerative energy sources, the losses of the heat generator and distribution and the auxiliary energy required (ventilation, pumps, etc.).

example

For buildings of the same type, location and equipment, for example, system expenditure figures of 1.5 were determined. In order to produce the energy required for heating, cooling and hot water, an additional 50% of the primary energy has to be used (not because the building uses 50% too much, but to compensate for real system losses)

System expense figures depend on many factors and are therefore not easily comparable between different buildings. Forecasts and calculations are therefore subject to uncertainties. With a small number of system costs, energy losses due to a low insulation standard can be compensated for in terms of primary energy.

In DIN V 18599 (valid since the EnEV 2014 came into force), the calculation method for determining property-related system expense figures has been redefined. This calculation method applies to non-residential buildings as well as to residential buildings if electricity is generated in or on the building.

In the future, income from photovoltaics, solar thermal energy and heat recovery technologies will be weighted more heavily, so that the lowest system expenditure figures can be achieved with the use of the appropriate system technology. Depending on the thermal insulation standard and the size of the heated area, almost 85% of electrical energy can be generated over the course of a year with the aid of photoelectric collectors than electrical energy is required to generate the heat required.

The use of electrical energy from conventional sources is weighted less heavily (and thus influencing the system expenditure figures), since the proportion of electrical power from wind power and photovoltaics is continuously increasing.

Web links