Solar energy in Israel
Is Israel located in the geographical latitude of approximately 30? N, where the probable annual solar irradiation is of about 2000 kWh for square meter. Nevertheless, it is not provided with energy natural resources; the whole electric power and the fuel of the country comes from coal and imported oil. At present, the generating capacity of electricity of the country belongs to about 6,5 GW, what represents approximately 1 kW per cápita; more this appreciation has changed in the last years as the need for electricity, in all the ambiences of the life, has increased. Opposite to this situation, therefore, it is not of surprising that Israel has transformed in pioneer in the use of the solar energy. Even more, being provided with big areas of desert (approximately 0 % of the country), it is natural that there is carried out an extensive research work and Development to allow the desert of the Néguev to provide in the future substantial quantities of energy derived from the sun.
The current use of the Solar energy
Domestic warm water
Perhaps the most current declaration of setting to work to the sun in Israel there are the solar water heaters that cover the roofs to everything long of the country. The typical domestic units consist of a 00 liters tank for the storage of the water, with isolation and a 2 square meters flat panel.
The last one gathers the solar radiation, warms the water and the raisin for his storage without need for pumping, using only the gravity force. These systems work with an annual efficiency I mediate of approximately 50 %. Therefore, is it easy to calculate that a unit like that saves his owner approximately 2.000 kWh per year in electricity costs, raising the temperature of a tank full of water in approximately 30? C over his starting point, in an average day - that is to say, warming the water to a temperature of about 50 % This means that in most of the days of the year there is no need to use the electrical unit of support (that is in all the tanks) to guarantee that the water is sufficiently warm for his use.
Bigger systems, generally with pumping, are in units of housing of big height, in some kibutzim and in several industrial plants throughout the country.
Inert solar warming of the ambience
Although Israel is considered to be commonly a "warm" country, the winters can be colds, particularly in Jerusalem and in other tall areas, including those in the desert of the Néguev. Nevertheless, the climate is ideal for the employment of the this way called inert solar warming.
Basically, this means to design a house so that it could warm itself with the winter solar beams, and, at the same time, to stay fresh in summer. The alternative form of active solar warming of the ambience, which he uses solar collectors, electrical pumping for the circulation and mantención of the heat, although it is much studied in other places of the world, is not effective in Israel for his cost due to the relative briefness of the winter station.
The basic ingredients for an inert solar house in Israel are: (1) The well isolated exterior walls of the building; (2) enough thermal mass to smooth the big changes of temperature and to provide a night accumulation; (3) an appropriate windows area in direction of the south.
The typical solar houses in the coldest parts of the country must have a wall structure that includes 1 cm. of plaster thickness inside, followed by 10 centimeters of concrete solid for the thermal accumulation, then 5 cm. of insulation with froth of polyurethane and, finally, some completion, in accordance with the codes of local construction, to protect the insulation. The roof must include 10 cm. of insulation with polyurethane and the entire area of windows in direction of the south it must be about 0 % of the surface of the apartment.
In the most warm places of the country more kidlings need windows surfaces from themselves proportionally. All the windows must be provided with exterior blinds to reduce the unwanted penetration of the solar beams in the summer. The first inert solar house in Israel was constructed by adobes dried to the sun and it is in the campus of Sde Boker of the University Ben-Gurión. Since it was finished at the end of the 70s, the basic beginning of the inert solar design has been adopted extensively by the architects of the country.
Photovoltaic rural lighting
At the moment of writing this article (1997) there is no industry that makes photovoltaic cells in Israel. This fact, along with the still relatively expensive cost of the above mentioned cells, has caused a certain scarcity in projects of photovoltaic demonstration, in spite of the ideal climatic conditions that the country offers for this technology. There exists a sector, nevertheless, in which there has been a relatively big penetration of the photovoltaic cells to the public knowledge and talks each other of the bus stops in the rural sector.
Several private businessmen import the excellent components and sell (in general to the local authorities) units of lighting that consist of a photovoltaic panel, a battery of accumulation, a lamp of of low potency and an electronic control to protect the battery. This way, the solar energy is used to illuminate the bus stops during the night.
DEMONSTRATION OF NOVEL SOLAR PROJECTS
After the industry and the Israeli government began the crisis of energy of 1974 they projected several novel solar demonstration programs. The most prominent two in the private sector were a generating solar electricity sink in the Dead Sea, and a system of industrial heating in the northwest of the Néguev. Also, the government established a big center of tests for solar demonstrations in the Néguev.
Electric power of solar saline sinks
The basic idea implies a sink of saline water, of about 2 meters deep, which is supported artificially so that his salinity grade (and consistently his thickness) is major towards the fund than in the surface. The absorption of the solar radiation at the bottom of the sink warms the water of the depths that cannot rise for his high thickness as regards the top layers.
In such a situation does the temperature of the water in the fund increase and can reach temperatures near to the 100? C. Even more, since that the sinks are very big - one of the sinks of demonstration, in Beit Haaravá, it is 250.000 square meters - this represents an enormous quantity of piled up energy. The Corporation Ormat, which was one of the pioneers of this type of sinks, developed a special turbine of low temperature that allows the warm water of the sink to turn an organic fluid into steam and this way to produce electricity. For the sink of Beit Haaravá a turbine of 5 MW was constructed.
The thermodynamic efficiency of a producing system of energy of this type, comparatively to low temperature, demands few requisites, approximately 1 % like ideal. In accordance with this, one might foresee that a sink like that produces, like average, only about 570 kWh of electric power. A turbine of 5 MW might, therefore, seem at first sight very little optimistic.
Nevertheless, what gives a singular value to the solar sinks, compared to all other technologies, is his capacity of built-in accumulation. Slow several weeks until the temperature of the sink reaches the constant state in his biggest depths, after which, whenever average major does not extract energy to itself to a valuation that 570 kWh face-value in an annual base, it is possible to obtain an energy production enormously bigger any hours than the day - generally during the periods load peaks in the morning and in the evening.
In fact it is allowed to the sink to absorb solar energy during the day, but the turbine occurs only early in the morning and in the last hours of the evening. The turbines of organic fluid of Ormat have demonstrated to have long life, partially because it is a completely sealed unit, which can find them in any place in which sources of low temperature exist and electric power is needed.
Steam for industrial processes of parabolic solar collectors
The second one big and novel solar demonstration project was one that was implying the use of parabolic searchlights to produce heat for industrial processes. This was a project that the Corporation Light carried out in a French fries factory in Shaar Hariéguev. With this intention, mirrors that were following the sun and curled to form long lines of reflecting large pans they were concentrating the light of the sun on a central pipe across which oil was pumped.
The oil warmed to the sun, to temperatures of more than 200? C, it was used to produce steam and to supply the heat needs for the plant. Similar solar collectors were used later by Light in his very famous electrical plant of 12,5 MW in Dagget, California. Once it was achieving successfully his revenue to the electric power production, Light devoted itself to the construction of six plants of energy of 30 MW, using a coreading unit of the sun of a major and enclosed size two stations of 80 MW that there included a third generation of even more big solar collectors.
All these electrical plants were constructed in California. Although the plants in the State Joined are still in full functioning, the company Light failed before managing to finish the negotiations for the installation of a similar solar station in Israel.
The National Center of Solar energy Ben-Gurión Además de the investment in two projects of the private enterprises mentioned previously, the government of Israel established, in 1985, a center of tests of solar technologies in Sde Boker, in desert of the Néguev.
The original purpose of the above mentioned center was to be able to demonstrate, in a comparative way, the diverse solar technologies that seemed promissory for the energy production in big scale. Between them there was counted a project of Light of a ring of solar warming of oil and a system of enormous parabolic large pans of mirrors designed to warm the water transforming it straight into steam instead of doing it across the stage of the warming of the oil.
Unfortunately, this system was never completed by Light and it is in Sde Boker, nowadays, like the monument to a commercial company that was on the point of generating solar energy in big scale to a truly competitive cost.
In addition to the thermal - solar demonstration systems in Sde Boker, some systems were installed fotovoltalcos so that it was possible to feed the electrical network to them. In 1991 the government entrusted to the University Ben-Gurión the task of turning the National Center of Solar energy Ben-Gurión into an establishment for the solar investigation.
Nowadays, under his new operators, the investigation in the center covers a wide topics bogey. In addition to the electric power production, the photovoltaic cells are investigated both at system level and of devices (new materials), the solar radiation is studied both from the point of view of the energy and from the environmental point of view (UV13/capa), and a series of projects in big scale, both in Sde Boker (giant parabolic plate) and in other parts of the Néguev (photovoltaic system 200 kW in the kibbutz Samar) they are in diverse stages of planning and execution.
SOLAR RESEARCH AND DEVELOPMENT IN ISRAEL
The Investigation and the solar Development is carried out in several universities and institutes of investigation along the whole country.
The Institute of Solar radiation of the Néguev was established by the Department of National Infrastructure in the 80s in cooperation with the National Center of Solar energy BenGurión and the Meteorological Service. The Institute documents the solar radiation (and other pertinent meteorological parameters) of about 10 places in the Néguev, for the purpose of identifying spaces adapted for the installation of stations of solar energy in the future and providing a database for his most efficient design.
The photovoltaic ones, in spite of counting at present with very little or no industrial support in Israel, enjoy a modest grade of governmental support because this technology can constitute the base of some of the stations of energy in the future.
Novel methods for the production of solar cells of silicone are being investigated in the Academy of Technology of Jerusalem (cells of the only crystal, of high efficiency) and in the University of Tel Aviv (thin amorphous layers of silicone). New materials of thin movies are being studied for his potential photovoltaic use in the University Ben-Gurión del Néguev (C0), in the Technological institute of Israel (Tejnión) (CdTe) and in the Scientific Institute Weizmann (WSe2).
The thermal - solar energy, another technology candidate for future energy plants, is being investigated in the University Ben-Gurión (parabolic large pans and parabolic plates) and in the Institute Weizmann (solar stove and receiving central tower), the last one with active participation of the industry. The plate of the University Ben-Gurión, which will be located in the National Center of Solar energy Ben-Gurión, will have a 400 square meters surface and it will be capable from a compilation of the solar beams up to 10.000 times.
This is a magnitude major than the concentration that is achieved in the searchlights lineares like the parabolic large pans, and therefore it will allow a wide scale of new channels of investigation.
The Receiving Central Tower of the Institute Weizmann, on the other hand, consists of a field of 64 so called mirrors "heliostat", each of them with an approximate surface of 50 square meters, which direct the beams of the sun to a cauldron or another appropriate recipient mounted in a tower of approximately 50 meters high. The combined effect of so many surfaces of mirror, focused on a relatively small central recipient, can produce obviously extremely high solar concentrations.
The tower of the Institute Weizmann must not be confused with another concept of tower that is being developed in the Tejnión. The idea implies the water pumping to the end of a very high tower (1 km or more) that is located in a desert area.
The water will evaporate and the printing created by the fall of cold and humid air will make work a turbine of special wind that is inside the tower. East, of course, is a secondary use of the solar energy, but, nevertheless, it has interesting probabilities.