CHAPTER 4 - SPACE HEATING APPLICATIONS HISTORY AND ACTIVE SYSTEMS

Abstract

This chapter discusses the history of active systems of space heating applications. The term solar house first became familiar when architects began to use large, south-facing windows to let the lower slanting rays of the winter sun penetrate into the back of the room. There was no real distinction made between the active systems (using pumps or fans to circulate heat) and passive solar houses. It was noticed that while fuel was saved during the day, it was not possible to store the solar energy and that at night and during cloudy days the heat loss was so great that there was a relatively small saving on fuel during the entire heating season. The chapter describes the principles of the heat pump. By supplying energy to the heat pump, heat is transferred from a low temperature region to a higher temperature region. The earliest applications were in refrigeration, where the food is maintained at a temperature lower than the surroundings, while heat is rejected from the refrigerator to the surroundings by the means of an external heat exchanger. The coefficient of performance (COP) of a heat pump is defined as the ratio of the energy output to the input. The energy output appears as useful heat at a higher temperature than the surroundings while the energy input is supplied by electricity or the direct use of fossil fuels. The total energy input to the system includes the natural energy from the environment. More useful energy at the higher temperature is obtained from the system than was supplied to it through the use of electricity or fossil fuels.