In this paper we are going to briefly study the issues of the solar energy, the usage of passive and active solar systems, the ways of their application, their advantages and disadvantages if compared to each other.
Solar energy might me used for heating not only water, but space as well. There are two types of solar-heating systems ”“ active and passive, which can also be combined. In general active systems are more expensive and complex to be build, but for retrofitting a building active systems are the only source of solar energy.
Passive solar space heating systems are based on special design features, like for example very big windows from the south side and special materials used for floors and walls for absorbing the warmth during the day and giving it out during the night (Baker, 2003). Very often passive solar systems are used for greenhouses. There are three main types of passive solar systems: direct gain, indirect gain, an isolated gain. The first one is the simplest, as it just stores and releases the energy for heating. The second one is also based on the usage of stored sun energy but by the material, which is usually between the sun and the space for heating, for example walls. Finally the third type collects the sun energy, isolated from the living space, for example in a separate room, then heated air naturally goes to the rest of the rooms. In comparison to active solar systems, passive systems need much less costs for maintenance and operating, certainly under the conditions of their constant optimization for better performance. “Energy conservation reduces the needed size of any renewable or conventional energy system, and greatly enhances the economics, so it must be performed first.”¯ (Baker, 2003).
Active solar heating systems are built with the help of collectors for absorption of solar radiation and electric pumps for later distribution of the heat. The energy-storage systems allow them to produce heat even when the sun is not shining. There are two major types of active systems, based either on liquid or air heat transfer medium in their collectors (Swartman, 2005). Air based systems are often used for heating the water at homes during summertime.
Active solar systems have their advantages over the passive ones. Due to their pumps or fans they have sufficiently higher solar savings, but as it was already mentioned these systems are more expensive. There is also the so-called hybrid approache developed, which allows to use photovoltaics for producing power for fans and pumps.
Started from 1900s people started to use the sun energy, certainly the sun was the source of interior light, but then it was substituted by electric lamps, as more improved source of light. However, later attempts to apply sunlight with the help of lens collectors or reflective light pipes were done. Later on the technology of hybrid solar lighting was developed. It is able to collect sunlight and through optical fibers sends it into a building , where “sensors keep the room at a steady lighting level by adjusting the electric lights based on the sunlight available”¯ (Swartman, 2005).
Thus solar and electric powers are used in combination. The efficiency of the process roots from lack of energy conversions.
Overall, although this is evident, that development of artificial energy sources was a huge step for mankind, but on the other hand, due to growth of their costs there is evident necessity in further development of alternative sources of energy with high potential and efficiency, but lower costs. The constant availability of solar energy and the fact, that it is environment friendly, should also be taken into consideration.