SOLAR-Power-Plants Description of the different types of solar power plants Photovoltaic: Is by far the most widely used technology. Technical basics: The photoelectric effect of solar cells is used to convert energy. These cells are connected to form so-called solar-modules. The electricity generated can be used directly, fed into electricity grids or stored in accumulators. Before being fed into AC power grids, the generated DC voltage is converted by an inverter. The system consisting of solar modules and the other components (inverter, power line) is called a photovoltaic-system. Advantages over thermo-solar power plants: It is the simplest form of solar power generation. Due to the high production numbers, the prices are extremely reduced Very inexpensive electricity generation Simple installation Easy maintenance Disadvantages compared to thermo-solar power plants: The main disadvantage is that they are not 24/7 (base-load capable). Electricity generation is only possible when the sun is shining. In contrast to thermo-solar plants, which store the energy for night-time operation in simple heat storage tanks, the storage of electrical energy is extremely complex and expensive. Today, it is only practised in smaller systems, such as domestic systems, but true 24/7 operation is not possible for large systems. In order to maintain grid stability, only parallel operation with base-load capable power plants is possible, which guarantee the fluctuations and night-time electricity generation. A weakness of the photovoltaic modules is the loss of efficiency at high temperatures. The dark blue cells heat up extremely in the desert climate, which not only impairs the efficiency, but also the service life. The constantly rising temperatures will further accelerate these disadvantages when used in desert areas. Extreme dependence on China.80% of photovoltaic modules now come from China.Due to the scarcity of polysilicone as a raw material, this figure could rise to 95%. Extreme land demand. Tower-Power-Plants: Tower power plants belong to the group of solar power plants that generate electricity by concentrating solar energy and producing steam. In tower power plants, so-called heliostat mirrors, which are positioned around a high tower, reflect sunlight onto a point on the receiver of the tower. The extreme concentration creates over 1,000° Celsius at the receiver. This heat is used to generate steam, as in all steam power plants. Advantages of tower power plants: When using thermal storage, the power plants are base-load capable - 24/7 operation is possible. When cooling with sea water, sea water can be desalinated with evaporation plants. Disadvantages of tower power plants: Extremely complex and expensive. The receiver tower must be as high as possible so that the heliostat mirrors can be positioned close together without shading each other. Each individual heliostat requires an extremely stable pylon on which it is mounted. The very stable anchoring is necessary because the heliostat has to be aligned very precisely to a point on the tower. This point is sometimes over 100m away, so the slightest deviation defocuses the heliostat! A heliostat is a free-standing mirror with a large wind-attack surface. After a sandstorm it may be necessary to recalibrate all mirrors. Each heliostat needs not only a very firm anchorage, but also a robust mechanism that precisely aligns the heliostat in 3 orbits and constantly tracks the sun. To ensure precise alignment, each individual heliostat requires a complex electronic control system and expensive digital motors. The cost of automatic control is enormous and each of the individual heliostats needs its own tracking system. The maintenance effort is enormous, because elaborate mechanical drives are subject to the necessity of constant maintenance in order to function properly in the desert. Considerable effort and water consumption when cleaning the heliostats Every single heliostat has to be driven by tanker and washed down manually. Extreme cleaning and maintenance effort for a tower-power-plant with 392MW means the maintenance and cleaning of more than 300,000 individual heliostat-mirrors! In order to keep the cleaning costs within reasonable limits, the maintenance intervals are extended, which is very much to the detriment of efficiency. Substantial space requirements A 310 MW plant requires over 3km 2 of space The material requirements of steel, glass and concrete are very high and so is the carbon footprint. Another major problem is the receiver system at the top of the tower. Temperatures far in excess of 1000° Celsius are generated here. This enormous energy density must be transferred to the heat transfer system - a great technical challenge! Very expensive is the tower with over 150m height We are convinced that tower power plants are the worst solution for thermosolar power plants. Trough power plants Trough power plants are the most widely used concentration thermal-solar power plants. Technical basics: The mirror is curved like a trough and thus concentrates the solar energy in a receiver placed centrally in front of the mirror. The receiver consists of a steel tube in which the steam is formed. The steel tube is surrounded by a glass tube in which a vacuum prevails (insulating can effect). The evacuated glass tube prevents the thermal dissipation of heat energy from the steel tube. The trough mirrors move around the longitudinal axis and thus follow the sun. Advantages of trough power plants: Relatively simple mechanical construction Years of experience Good efficiency Equipped with heat storage, base load capable (24/7) With system cooling with sea water and equipped with evaporator systems, large quantities of fresh water can be produced using the waste heat. Simple system operation Disadvantages of trough power plants: Complex, expensive mirror-field construction Very high maintenance costs Highly susceptible to wind due to the bulky mirror geometry. Extremely difficult and costly to clean Very high water consumption for cleaning Automatic cleaning only possible with great difficulty In order not to make the mechanical movement apparatus too heavy, the mirror substructure is very filigree and therefore easy to decalibrate and susceptible to mechanical damage. The mirror arrays require constant maintenance and repair, which is a very significant cost factor. The receiver tube follows the sun together with the mirrors, it is a dynamically suspended receiver. In order to have them move, their connecting elements must be articulated. Ensuring the tightness at an extreme steam pressure and a temperature of over 500°Celsius is a big challenge and a constant repair job! Fresnel power plants Fresnel power plants are, unjustly, the least perished of the power plant types. Technical basics: The mirror surface of Fresnel power plants are flat linear mirrors. The mirrors are usually 60 cm wide and 6 m long. They are arranged side by side and rotate around the longitudinal axis. The receiver tube hovers centrally about 6m above the mirrors. A so-called secondary mirror is mounted above the receiver tube, which captures the solar rays that do not hit the receiver tube and directs them onto the receiver tube in a focussed manner. Advantages of Fresnel power plants: The mechanical construction of the mirror field is very simple. The drive of the mirror tracking system is also not very complex. The flat design of the mirror surface offers only a very small surface area for strong winds to attack. The receiver is statically mounted, thus eliminating the need for sensitive moving connections. The flat design makes them ideal for standing on. The cleaning can be done fully automatically due to the flat mirror geometry. Disadvantages of Fresnel power plants: In comparison with the tower and trough power plants, there are exclusive advantages! DESERT-VISION multifunctional Thermo-Solar Power Plants Much more than a Thermo -Solar Power Plant!
Problem: Moving steam (500°C / 110bar) leading elements
Trough power-plants
Tower power-plant
DESERT-VISION power-plants
Fresnel power-plant
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