Thermal behaviour of a heated building under random weather condition in Warsaw

The paper discusses thermal analysis methodology applied to buildings, in which the stochastic nature of the external and internal forces is concerned. The forces are as follows: ambient temperature, solar radiation and heating or cooling load. The principle of superposition is applied to the deterministic and the random components for the concerned weather parameters as well as the state variables. The weather model, which has been constructed, is indispensable in determining the thermal behaviour of a building stochastically. The stochastic weather model expresses the joined and mutual influence of the external temperature and solar radiation on the buildingʹs thermal performance. This stochastic approach, presented in the paper, to a simple example is applied, just for the verification purposes. Computer simulations of a heat loss process for a simple two-node dynamic model of a heated building have been carried out. The heating system is either controlled or works without that device. At first, heating installation has been working either constantly or intermittently. As a result of numerical computation, the distribution of mean indoor temperature and heating load has been obtained, as well as their standard deviations. But in order to evaluate the influence of solar direct gains on a roomʹs heat balance the same computer simulations have been carried out for the single forcing function—the external temperature. Moreover, to underline the effect of solar radiation on the roomʹs temperature the heating installation has been turned off and the inner temperature is settled only as the result of weather condition. With regard to those simulations—time history of mean room temperature as well as its standard deviations has been computed. The identification procedure of the weather parameters has been based on a 10-year meteorological data for Warsaw.