To do a bit of clarity among the many items very inaccurate appeared on the net these days, today I speak of the recent invention of Ripasso , a company engaged in green technologies that would put in place a new system for harness the sun’s rays.
The draft Ripasso Energy AB , a Swedish company, it combines two very known as the parabolic mirror and the Stirling engine , both inexpensive compared the photovoltaic cells or compared to the same solar concentrators.
Unenedo these two technologies than two centuries ago, you can get a much higher energy yield , up to 32% , compared to traditional photovoltaic that, depending on the quality, generates between 9% and 14% yield.
In addition, compared to photovoltaic systems, the area occupied at the same power is greatly reduced. With photovoltaic systems, on average, it is needed 8 square meters for each actual kilovwatt power.
But be careful, we are talking about solar energy and photovoltaic.
In the photovoltaic, cells employ a physical principle that converts sunlight directly into electricity by the inherent capacity of the photovoltaic cells.
In a concentrating solar plant, it is used the thermal factor, present in a greater and easier-to-use thanks to a mirror concentrates sunlight in a specific point to get then, through the accumulation of thermal energy (heat), a potential converts into energy through various processes.
As we have seen, the solar concentrators They are more profitable than the photovoltaic. In the United States, they have been made several mega plant, financed in part by Google and Apple, as the project SolarCity and Ivanpah Solar, a solar thermal plant by 392 MW.
The project Archimedes, tested many years ago in Sicily, exploited minerals to absorb heat during the day, ensuring the production of electricity at night.
We now return to the project Ripasso.
Ripasso is a CSP plant made up of 2 elements or parabolic mirrors and Stirling engine.
The parabolic mirrors have a diameter of 12 meters for a total area of 104 square meters of glass, with rates of 95% and refraction an equivalent power of 1 kW per square meter.
The mirrors are motorized to follow the sun and always remain so at maximum efficiency that we select to repair the plant from excessive wind. Exploit the possibility of going to follow the sun 360 degrees on both axes.
About the solar tracking system, there is also an Italian product made in Vicenza, consisting of a biaxial solar tracker called Ray 90 (Click here for more information).
The huge surface is able to withstand wind up to 45 meters per second, something to consider given that most of the plants are installed in desert areas or semi-desert.
As indicated by the same company, are needed just 2 hectares of area for each MW of power and the entire system does not use water as a conductive element, which usually requires considerable costs.
The Stirling engine
The Stirling engine, which as the gasoline engine has a reduced efficiency equal to 40%, exploits the pressure gas heated up to 720 degrees and 200 bar pressure to move the turbine or a piston. It is often used in landfills, also Italian, to convert the biogas generated from waste buried into electrical energy.Its operation is simple: it is a closed cycle engine, usually in pressure, which uses the heat to generate a thermal differential inside the mechanism that then allows it to move a piston. Not having combustion chamber, the engine components are not subject to rapid wear as it happens in car engines.
Having few components under stress, the system requires little maintenance and is kept operating for over 25 years , with a rate of decline on the yield very limited.
How Ripasso CSP?
As you can see from the picture , the system is modular and consists of a large convex mirror that concetra the solar rays in a box containing a Stirling engine. A Stirling engine uses a gas heated to generate the pressure needed to run an internal rotor, a little like the wind rotors.
The experimental system was installed in South Africa in the Kalahari desert. Among the points of strength, that it can be assembled on site due to the fact that its realization is not particularly complex.
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