Energy Balance

Energy balances are the computational foundation for the most rational possible use of energy meaning that the last useful energy is confronted with the cost of the primary energy. Energy balances can depend on either calculated or existing measured values, and they are always based on a specific object or use.

The energy balance for a solar heating system is generated according to the following formula: The solar radiation is given a value of 100%; from this, about 20% is lost through reflection; the collector itself uses another 30% by heating up and reradiating its heat; another 15% is lost as radiated heat in the solar circulation system, in the storage tank, and in the potable water distribution. The useable energy, also considered the system’s efficiency, is then 35%.

The Heat Conservation Provision of 1995 expects buildings to have an energy balance, which determines the heating demand. The heating demand consists of the heat demand that is lost through walls, windows and the roof and the ventilation heating demand. Not included is heat gained internally (body and machine heat) and solar heat gain (solar radiation through south-facing windows).

The pre-calculated energy balances often deviate strongly from the actual measured values. For buildings this comes mostly from variances in individual use. In the case of very complicated energy balances, for example with national economies or single energy carriers, important factors are sometimes overlooked.

The use of solar energy is an advantage in any energy balance because the energy source is available without cost.

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