Encouraging news in the renewable energy come from solar thermal industry that, in 2009, has experienced considerable growth and that seems destined to play an even more important in coming years.
The U.S., in fact, intend to achieve by 2020 the technology for new power plants with a total capacity of 10.3 GW of power.
Also Italy is taking decisive steps in this field, as evidenced by the recent birth of a company called Archimedes Solar Energy, which produces the key component of solar thermal power plants, pipes receptors, according to a new technology patented by ENEA.
How does a solar thermal power plants?
The English name (“concentrated solar power systems) makes a better idea of their operation. Obviously, the primary energy source is the sun, clean and renewable source for excellence. Through a parable of mirrors (which evidently reflected solar radiation), the energy is concentrated at a point (the focus of the parabola), if you put a receiver. In general, it uses thin tubes, placed focal axis, containing a fluid heat carrier. The substance inside the tube is heated to reach very high temperatures, because it exposed the effect of concentrated solar radiation.
The fluid circulates and passes by receiving a “hot tank” during an insulated container that retains heat. From here to turn the liquid goes into a heat exchanger, which transfers part of its heat to another fluid in order to generate steam. The latter will go to operate the turbines, as in traditional steam power plants. The fluid that has transferred the heat goes into another room, the “cold tank”, and then falls back into the circulation through the tube receiver.
To ensure that the radiation is actually more concentrated, the entire dish of mirrors rotates following the movement of the sun. Of course this shift is planned in detail depending on the particular day of the year.
thermodynamic energy scheme works
The first large solar thermal power plants have sprung up in the southern U.S. and particularly in the Mojave desert in California
The first large solar thermal power plants have sprung up in the southern U.S. and particularly in the Mojave desert in California, very sunny region. But in recent years the interest in this technology is widespread in Europe.
In Italy, more than 10 years, ENEA (Italian Agency for New technology, Energy and Environment) conducts research in that field with goal of achieving plant type of innovative, efficient and used in zones not Prepared by the sun too.
The institution precisely patented a new technology for the realization of manifold pipes. Structures to function normally is used when a fluid consisting of a synthetic oil, that under concentrated radiation reaches 400 ° C. Researchers ENEA (based on an idea by Carlo Rubbia) have developed a fluid consisting of molten salts can reach a temperature of 550 ° C. These include a mixture of 60% of sodium nitrate and 40% potassium nitrate, salts easily available and storable.
The manifold is covered by a selective coating (also developed in the laboratories of ENEA), which ensures maximum absorption of radiation contained in the spectrum of sunlight, while reducing the emission of infrared radiation, which prevents heat loss.
After the passage in the heat exchanger fluid drops to a temperature of about 290 ° C, and then back into the circulation. The fact that it reaches higher temperatures than the oils used in the past means that we can increase the efficiency of, or better ensure continuity of electricity even in overcast days and even into the night. During sunny days, in fact, the system stores more heat energy than they need and the “accumulated” in the “hot tank”. And when the sky is covered by clouds or the sun goes down, the plant continues to produce energy under the accumulated heat that goes with losing a certain inertia.