Energy profile and use of solar energy in Poland
2.3. USE OF SOLAR ENERGY IN POLAND 41
active solar system is expected to operate only during the heating season (i.e. from October to April), the optimum inclination angle for solar collector surface should be in range from 55◦ up to 60◦. According to Wisniewski et al. [180] a surface of the solar collector should be tilted at the angle of 40◦, when an active solar system is expected to operate continuously throughout the year. Moreover, to maximize the performance of solar collectors, it is recommended to move the absorbing surface slightly to the south east (10–15◦) in warm months and to the south west (10◦) during the heating season.
The present state of the solar energy use in the Polish building sector is dis-proportional to an existing potential for solar heat applications; less than 8 PJ of about 3000 PJ of the heat used for annual heating purposes is produced by active solar heating systems [41]. The total surface area of solar collectors under operation in 2010 in Poland was only 655890 m2. At the same time, the area of 13824000 m2 was under operation in Germany [60]. A significant limitation in the state of the development of solar technologies as compared to countries with similar solar radia-tion condiradia-tions, is a consequence of the coal energy lobby, standards of architecture designs, investment costs and common opinion that solar technologies are not effi-cient under Polish climate conditions. Among the above-mentioned limitations, the reasonable barriers are, however, the interference into the building aesthetics and investment costs. The application of solar collectors is not aesthetically acceptable in many cases [25, 168]. The economic efficiency expressed by the payback time of active solar heating system investments can be equal up to 16 years [41]. Neverthe-less, the Polish market of solar technologies grows over recent time [60]. The forecast (assuming a realization of the solar energy promotion scenario) for 2020 and 2030 of the use of solar active heating systems in Poland is given in Table 2.1.
Table 2.1: Forecast for active solar thermal system use in Poland [36]
Solar thermal energy use
In general, the use of the solar energy in Poland concerns mainly the solar active systems in the form of a stand-alone or roof-mounted flat plate or vacuum solar collectors, in which the fluid flow is forced by mechanical device. These systems are
mostly used to heat the water for domestic purposes. Chwieduk [41] indicated that the use of solar collectors in Poland to support DHW systems is effective during spring and summer, especially from May to the end of August. In this time, the total hot water demands can be fulfilled on average of 80–100 %. The use of the solar energy in Poland should be, however, more focused on the space-heating systems since there are already available technologies, such as the floor and wall heating, which require a much lower operating temperature than the operating temperature of DHW systems. Moreover, due to a radical decrease of the heat demand in res-idential buildings, many new heating technologies based on very-low-temperature heat sources, e.g. Thermal Barrier (Section 3.3.2.4), were developed. These tech-nologies give an opportunity to develop and implement novel, very cheap and of simple structure solar collectors which overcomes above-mentioned limitations to widespread the use of solar technologies. The promotion and implementation of such solar collectors should be a major target in the future.
2.4 Summary
The availability of the solar energy in Poland is similar as in most of European countries. The approximated annual amount of the available solar energy in the entire country is almost 400 times more than the total amount of the heat energy used for annual heating purposes. Hence, it can be concluded that there exist a great potential for solar systems in the Polish building sector. One should notice, that the solar energy availability and heat demand for the space heating are opposite in time. Therefore, the use of the solar energy for the space heating under Polish climate conditions requires a seasonal HS system.
The total surface area of solar collectors in operation in 2010 in Poland was over 21 times lower as compared to Germany. The use of the solar energy in Poland is related mainly to active solar energy technologies dedicated to support DHW systems. Less than 0.3 % of the heat used for annual space-heating purposes is provided by active solar technologies. A disproportion between the existing potential and use of the solar energy is a consequence of the strong coal energy lobby, standards in architectural designing, high investment costs and common opinion that solar technologies are not efficient under Polish climate conditions. Except of the last argument (which is wrong) the interference into the building aesthetics and high investment costs are real barriers for solar technologies in Poland. Therefore, an implementation of novel, cheap and simple solar collectors should be a major target in the future.
2.4. SUMMARY 43
The concept of HSC (Chapter 4) is characterized by a low cost and lack of in-terference into the building aesthetics. In view of these advantages over stand-alone or roof-mounted conventional solar collectors, it can be concluded that there is a great potential for applications of HSC to supply space-heating systems based on very-low-temperature heat sources dedicated for residential houses characterized by a low heat demand and also to support DHW systems. Therefore, the evaluation of the HSC performance during a year-round operation under Polish climate conditions is desired.