SOLAR ENERGY – PERSPECTIVES, TENDENCIES AND CHALLENGES IN ROMANIA C. Zaharia and L. Costachescu “Gheorghe Asachi” Technical University of Iasi, Faculty of Chemical Engineering and Environmental Protection, department of Environmental Engineering and Management, D.Mangeron Blvd, no.71A, 700050-Iasi, Romania E-mail: czah@ch.tuiasi.ro The renewable technologies are now available to make partially the transition away from today’s coal and oil-based energy system to commercial development of renewable energy in Europe. This paper examines some of the European policy reforms in the field of solar energy, together with the perspectives and tendencies in Romania to develop the production and commercial use of the solar energy as a widely available, abundant, free and unpollutant renewable energy. Centralized solar power stations in different countries had proven to be extremely unreliable and expensive to maintain; repairs frequently depend upon obtaining the service of expert technicians from the manufacturing company in the donor country. The challenge for development of solar energy in Romania is to find applications which are economically justifiable, socially appropriate, and technically sustainable. At present, this means applications which are of high value, remote, low electricity demand and part of a network that can provide adequate repair and maintenance services. In this context, efforts must be done and the commercial use of solar energy together with the other renewable energies (e.g., hydroelectric energy, wind energy, biomass energy, geothermal energy, etc.) instead of coal or oil-based energy will allow the 20 % reduction in carbon emissions and the stabilization of atmospheric CO 2 concentrations. Keywords: solar energy, solar thermal device, photovoltaic device, perspectives, Romania 1. THEORETICAL POTENTIAL OF SOLAR ENERGY SYSTEMS The solar energy continuously supplies the earth surface. Each year 5.4 million exajoules of solar energy are received into the superior layers of atmosphere. A share of 30% of the solar energy is reflected back to space, 45% is converted to low temperature heat adding up to the heat balance of our planet, and 25% is converted in the earth’s atmosphere for evaporation of water, for wind and wave energy, and marine currents (Kuhne and Aulich, 1993 [1]). There are only 2.5 millions of exajoules that reach the earth surface, higher than the whole energy used by humanity into 1990. The higher part of this energy is transformed into heat and absorbed by oceans and atmosphere, the other part is used into chemical process on the earth. The only relevant chemical process harvesting solar energy is photosynthesis. The energy converted and stored this way accounts for less than a 0.1% of the original solar energy, yet it is essential to all plant and animal life on earth. Our energy-intensive industries are ruled by energy economy rather than by issues of ecology. An extensive consumption of cheap fossil fuels has long been favoured, and questions of how to cope with consequences have not been answered adequately. These days, the worries of global warming were substituted 19% of fossil fuels with renewable and nuclear power. However, with world energy consumption rising further at an increasing rate, a drastic increase in efforts to implement renewable technologies is considered indispensable (Czakainski and Michaelis, 1989 [2]). A typical value for the solar energy on the earth’s surface is about 1500 kWh/m 2 per year (pa). In the northern part of Europe or Canada some 1100 kWh/m 2 pa may be expected, and in large area of the USA, Africa and Australia values exceeding an average of 2200 kWh/m 2 pa are not uncommon (Kuhne and Aulich, 1993 [1]). There are considered the variations of radiative power during the course of the seasons, and during the day/night cycle and local meteorological conditions. For Romania, the solar energy corresponds to values between 1000 - 1300 kWh/m 2 pa, from which can be collected only 600 – 800 kWh/m 2 pa. The solar energy on the earth can be captured and converted into other energy forms. There are known four ways to convert the solar energy into useful energy using different technical methods of capture, accumulation, concentration, storage and valorisation of insolation (Costachescu, 2007 [3]) such as: - photomechanical conversion – kinetic energy (mechanical work); - photothermic conversion – heat generation (e.g., thermomechanical conversion into pumping station or mechanoelectric generator, thermoelectric conversion for electricity, thermoionic conversion for electricity, chemical energy for electricity or chemical storage); - photochemical conversion – chemical energy (e.g., thermochemical conversion for chemical storage, combustion cells for electricity, photosynthesis for green life); - photoelectric conversion – electric energy. Heat generation currently account for about 45% of the commercial energy consumption in the world and about 35% in EU, yet it corresponds to only a small fraction of the theoretical potential for low temperature solar thermal systems. It is relatively simple to construct solar heat collectors having a utilization of solar radiation exceeding 10% conversion efficiency. The theoretical potential for the implementation of solar technologies exceeds heat demand by several orders of magnitude (Kuhle and Aulich, 1993 [1]). The situation of traffic sector is somewhat more difficult. The electrical power produced if the cars were covered totally by solar cell would not be sufficient for cruising even at moderate speed (for 3 m 2 of solar collector with