OPTO-ELECTRONICS REVIEW 12(1), 13–20 (2004)
Solar energy utilisation
Institute of Fundamental Technological Research, Polish Academy of Sciences 21 Œwiêtokrzyska Str., 00 049 Warsaw, Poland
Solar energy can be used by man in a planned direct way. There are two fundamental methods of solar energy conversion: photothermal and photoelectric. The paper is dealing with the analysis of photothermal conversion in the high latitude countries. Different types of solar active and passive systems are considered. The more reliable the solar system and the higher the temperature requirements, the required technology is more modern and sophisticated, and the construction of the system, together with the automatic control, is more complicated. The degree of complexity depends on the function of the system and required mode of its operation. In the case of solar space heating in high latitude countries, it is evident that thermal performance of solar source is not coherent with the heat demand. Therefore the use of solar energy requires a special upgrading, e.g. in a form of a heat pump or seasonal storage. However, the best idea for efficient use of solar energy is to design a building in a proper way, including the passive systems. The architecture is crucial for the energy balance of a building and it should assure proper use of environment, improving solar energy gains in winter and protecting inside of the building against solar overheating in summer.
Keywords: photothermal conversion of solar radiation, solar active heating systems, heat pumps, solar passive systems, solar architecture, availability of solar radiation, isorads.
1. Planned direct methods of utilization of solar
– solar stills for distilling water.
• Passive low temperature solar heating (cooling) sys-
Solar energy can be used by man in a planned direct or indirect way. In the case of indirect utilization of solar energy we consider the use of renewable energies which are secondary
effects of solar energy [1,2], i.e., wind energy, hydro energy, ocean energy, and secondary energy from photosynthetic process that is mostly connected with the use of biomass and biofuels. Using solar energy in the direct way we can apply
two fundamental methods of energy conversion:
• photothermal conversion of energy of solar radiation;
• photoelectric conversion of energy of solar radiation.
Applying a photothermal conversion of solar radiation
energy  we consider usually the following systems:
• Active low temperature solar water and air heating or
cooling systems, which includes;
– solar water heating systems with flat plate or vacuum solar collectors, – solar air heaters, including crop driers,
– solar space cooling systems coupled with sorption
– solar ponds, which are solar collectors and heat
stores at the same time. They comprise several layers of salty water. With the increase of depth the salinity (density) increases, convection is suppressed, and the bottom layer is the hottest,
• High temperature solar systems with solar concentra-
Opto-Electron. Rev., 12, no. 1, 2004
tems, which constitute solar architecture [4,5];
tors, in which a working fluid can drive a conventional
heat engine to produce mechanical work and if necessary electricity (in this case we consider electric power systems as described below);
Electric power systems. They utilize collectors with
concentrators, which achieve temperature high enough
to operate a heat engine to generate electricity. These
– electric power system with the distributed concentrating collectors. The collectors transfer the gained solar heat to a working fluid, then the working fluid
circulating through an every collector is gathered at
the central power station. If the working fluid is
steam, it is used directly in a steam turbine. The
working fluid could be also a...