The term photovoltaic cogeneration is used to indicate those systems that are able to use a portion of the solar energy is not exploited in photovoltaic processes. It is known that the photovoltaic cells (PV modules or photovoltaic panel) convert into electricity only a small fraction of the solar radiation (between 6% and 15%), the rest is dispersed or is again re-radiated into space. It is therefore of thermal energy that can be recovered. We can distinguish three types of systems:
Daylighting: transparent cells which constitute an integral part of the roof or facade of the building, allowing daylight illumination environments (light radiation is recovered).
PV ventilated: very simple systems in which the rear side of the photovoltaic module is affected by a flow of air that absorbs heat from the module (by cooling and also improving the efficiency), and which is then used for the heating of buildings.
Modules hybrid PV / T (Photovoltaic / Thermal) systems in which the photovoltaic modules are tightly coupled with the heat absorber. Generally liquid cooled can be flat or concentration.
Currently have commenced commercial applications. Are ongoing research on prototypes and pilot projects of experimental facilities.
Italy is an amazing area from a geological and volcanological, due to the presence of the crust thinner and because below it sinks the platform ionic, very old and heavy, driven by the great African plate. The platform, sinking, burning and emits bubbles of magma that rise to the surface, creating the volcanic arc of the Aeolian Islands and other submarine volcanoes. In summary, the Italian peninsula and its seas are characterized by at least four major areas of underground heat:
- The first is the Tuscan, with its geothermal fields of Larderello but extends to the caldera of Bolsena, then at sea for several miles;
-The second is that of the Campi Flegrei, Campania;
-The third, very large (and still little-known part) is that of the southern Tyrrhenian Sea;
-The fourth is the channel of Sicily, in the submerged volcano Empedocles and Lampedusa.
Italy is a country geothermally warm and has potential so vast as to justify a bet and technological research is unique in the world. At stake is a continuous and virtually inexhaustible source of energy that could bring the energy independence of the nation ("The Future of Geothermal Energy" (PDF, 14.1 MB).'s MIT proves that only with deep geothermal and technologies available today we would have to cover the energy consumption of the whole earth for 4000 years with steady consumption).
Energy from biomass and agro-energy
In addition to plants cultivated, even the vegetable waste (sawdust from sawmills, waste from wood processing) and sewage of animal origin may be subjected to anaerobic fermentation (the biomass is closed in a digester in which microorganisms grow by fermentation of waste generate biogas).
The pyrolysis allows instead to obtain a biomass gas (syngas) with a calorific value equal to that of LPG that can be used in production processes which require heat (eg.: Drying), for heating of the premises or to be transformed into electrical energy. The by-product of pyrolysis is biochar (90% carbon) which, when applied to soils, is a potent fertilizer. Its high porosity makes it possible the storage of water and nutrients that remain longer available to plants; also improves soil structure and its mechanical properties. Several studies have demonstrated the positive impact that the application of biochar has on agricultural yields, reducing the need for water and fertilizer.
Is not cheaper than in Italy to develop agriculture aimed at the production of biofuels (healthier and more rational seguitare to consume even our tasty fruit and vegetables and our exceptional wines!).
Consequently, in Italy also biomass, which now account for 30% of our renewable energies, will be used in the recovery phase of processing waste rather than through an ad hoc production.
Energy from the sea
In principle it is possible to convert at least five types of energy present in the sea: that of currents, waves, tides, tidal currents and the thermal gradient between the surface and seabed. There is also the possibility to recover, by osmosis, the energy dissipated when fresh water of the rivers pouring into the sea mixes salt water. Currently there is only one system for the exploitation of the tides in France, and are being tested logging operations of wave energy potential in the United Kingdom, Norway and Japan, and the thermal gradient in the United States. The European Union has recently concluded a study that identifies some 100 sites that could be used for the production of electricity from ocean currents. In Italy it is the Strait of Messina was identified to be among the most promising sites.
Energy from the waves
Making the motion of the waves to get electricity, despite the technical difficulties, never ceases to tickle the fancy of engineers. Are the study hypothesis to concentrate and focus the waves so as to increase the height and the potential for conversion into electricity. Other assumptions include instead of using the pressure changes that occur below the surface of the sea, other use of the floats that "follow" the wave motion transferring it to appropriate generators by means of hydraulic pistons.
Concentrating solar power
The panels solar concentration systems are able to concentrate solar rays to a receiver of contained dimensions through a system of reflective mirrors. The thermal energy obtained from the concentration of solar radiation is used to heat a heat transfer fluid, force-generating steam, and then electricity. Concentration systems are also known as Concentrating Solar Power (CSP). Compared to solar panels concentrating solar power (CSP) have several advantages:
- Lower costs (the cost of production moves on reflective surfaces, which are cheaper than photovoltaic or micro collector)
-Higher returns (convective losses in solar-thermal conversion is proportional to the surface of the receiver, which, being more limited in concentration technology compared to that of the collectors, allows you to achieve higher returns)
When it comes to wind instinctively think the wind farms, giant towers, blades and noise. The applications of wind technologies, in fact, still sore combine with distributed generation if we did not take into consideration the minieolico. A plant minielico complete up to 5 kW coast 5-7000 € / kW. An investment of this type connected to the national transmission grid allows, depending on the speed of connection, to avoid the purchase of energy or to create income from the sale of the latter. In the table below we provide a rough estimate of the energy that could produce wind turbines for various average values of wind speed, the savings compared to the bill ENEL and the time required to pay back the initial investment.
The economic return becomes interesting for average speeds greater than 5 m / sec or higher specifications for manufacturability at 1750 h / year. The accounts of the table were made considering only the market price of a kWh, ie without taking into account the public incentives. With the new energy bill the GSE (Energy Services Manager) would have to pay € 0.3 per kWh produced. The total savings would reach then 0,3 € / kWh.
The Energy Descent
"When the amount of bits and watt - that is, information and energy - embedded in industrial goods produced in mass exceeds a certain threshold, which inevitably generate an abundance impoverished. This abundance is often too limited to be shared, or destroys Freedoms and rights of the weak. " Since Ivan Illich wrote these words a lot of critical attention has been paid to the growth of the energy consumed by humanity. The awareness of the social and environmental damage due to excessive growth of energy consumption is slowly spreading. For more than a century chimneys and steaming locomotives were the symbol of progress. Even today it is believed that there can be a high level of well-being without a high primary energy consumption and that we are still far from the critical threshold where energy consumption and welfare are in conflict. Yet already in 1896 the Nobel Prize Svante Arrhenius had calculated very realistically possible climatic consequences of the rapid transfer of our coal mines into the atmosphere as CO2 (increase the natural greenhouse effect). Subsequently has been observed that even the nuclear and hydroelectric energy techniques involve significant, though different, human and environmental costs. Even the parks of wind turbines that spread in Italy begin to encounter the resistance of some citizens and administrators because they produce drawbacks. Photovoltaic and solar thermal panels directly generate fewer problems, but their economic and environmental costs of production and disposal as well as the area you require, you make it impossible for unlimited use. Is emerging critical attention not only to quality, but above all to the absolute amount of energy used. Even in the technical culture and its social implications emerges as a principle well known to those who study living things and their habitats, "there is no free meal in nature" (translation: in nature there are no free meals). As indispensable today, it is therefore insufficient merely to distinguish between energy dirtier or more "clean". Also spread the illusion that they can really exist clean energy seems the best way to evade the real problem. See for example the intense advertising campaign "Methane is nature." For the economist Jeremy Rifkin any future accessibility of clean energy sources, safe, cheap or even free alter so many incalculable balances Bio-geo-upon which life on Earth, including human life. According to the German physicist Hans-Peter Dürr, efforts should be made soon towards a 1.5 kW, where an adjustment of the technological structures but also social ones allows to create wealth while consuming less than 1.5 kW of primary energy per capita per day . It is a relatively small amount when you consider that equates to only electric current consumption of a refrigerator or a kW is the energy required to lift a 75 kg person from sea level to the summit of Mont Blanc.
Quality of information
A former faculty of each community, to distinguish between hierarchically disinformation, information, knowledge, culture and wisdom, seems to come less today. We know more and more, we understand less and less, one observer put it. Yet the industrial systems of communication and their concentrations are increasing indiscriminate issuance of any information, without any qualitative hierarchy or, more often, even inverting the priorities of this hierarchy that we have indicated. More often a message is useless or harmful and is more widespread. Our information try to shed light on many clichés, we try to give you guidance on what is really useful to people and what is instead the result of manipulation and source of profit for those who make clean energy its Trojan horse to continue to speculate.
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