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Principles of Solar Energy

Updated on April 6, 2011


Solar energy means energy, heat or electricity is produced directly using the energy radiated from the Sun (renewable energy) to Earth.


At any time the Sun on the Earth sends 1367 watts per square meter.


Solar energy is the one normally used by autotrophic organisms, ie those that perform photosynthesis, also called "vegetable". Other living organisms instead exploit the chemical energy derived from plants (or other bodies which in turn feed on plants), and also take advantage of solar power, albeit indirectly.


Taking into account the fact that the Earth is a sphere that rotates moreover, the average solar radiation, the European latitudes, about 200 watts per square meter. Multiplying this average power per square meter for the land surface of the hemisphere from moment to moment in the sun you get a power greater than 50 million GW (a GW - gigawatts - is about the average power of a large power plant).


The amount of solar energy that reaches the Earth's soil is so huge, about ten thousand times greater than all the energy used by humanity as a whole, but not concentrated in the sense that it is necessary to collect energy from very large areas to have significant amounts , and quite difficult to convert into energy that is easily exploitable with acceptable efficiencies. Products needed for its operation generally high cost of making solar power much cheaper than other methods of generating energy. The development of technologies that can make economic use of solar energy is a very active area of research but, for now, did not have revolutionary results.


Solar energy can be used to generate electricity (photovoltaic) or to generate heat (solar thermal). There are three main technologies to transform energy into usable energy from the sun:

The solar panel uses sunlight to heat a liquid with special features, contained in its interior, which transfers heat through a heat exchanger, water contained in a storage tank.

Concentrating solar panel uses a series of parabolic mirrors to concentrate the linear structure to sunlight on a receiver tube in which flows a fluid or a series of flat mirrors that focus the beams at the end of a tower in which there is a boiler filled with salts which melt in the heat. In both cases the "receiving apparatus" is heated to very high temperatures (400 ° C ~ 600 ° C)

The solar panel uses the special properties of semiconductor elements to produce electrical energy when stimulated by light.

Solar panel

Thermal collectors can be natural or forced circulation, the first use of the liquid in the panels to allow the circulation of heat within the system panel. In this case, the tank containing the heat exchanger should be higher than the panel.

The forced circulation systems use a pump that circulates the fluid within the exchanger and panel when the temperature of the fluid within the panel is higher than that inside the tank, which in this case, located below the panels. Such systems are more complex in terms of controls and equipment used (pumps, temperature sensors, three-way valves, control), but allow you to place the tank, even large, where practically you will, for example, on the ground and not on the roof where weight problems are difficult to place.


The solar panels convert sunlight directly into electricity. These panels take advantage of the photoelectric effect and have a conversion efficiency of up to 32.5% in cells lab. In practice, once the modules from the cells and the modules and panels when assembled on site, the average efficiency is about 12%. These panels, with no moving parts or other things, require very little maintenance: in essence only be cleaned periodically. The estimated lifetime of the solar panels is about 30 years. The main defects of these systems are the cost of the panels and the storage of energy.

The second obvious problem with this kind of system is that energy is produced only during daylight hours and is not suitable for any situation, being a form of energy electricity hardly accumulate in large quantities. It should be noted however that the production of solar energy is more precisely at times of highest demand, ie during the day and in the warm seasons, during which can compensate for the increase in consumption due to ventilation and air conditioning.

Thanks to legislation that provides economic incentives for photovoltaics and the possibility of selling the energy produced in excess to the operator of the transmission system, Germany is in first place in Europe for the electric power produced by solar energy: the amount represents 1, 0% of German energy and therefore is now totally inadequate to support the growing trend of energy demand (in Germany the primary source of electricity generation is coal, which covers approximately 43%, while second is the nuclear almost 23%).




Currently solar panels are used to provide hot water (solar thermal) and heating to homes and small ensembles. You tried to build solar power plants, using turbines, convert the stored heat into electricity, but these experiments have failed substantially to the low yield of these power relationships with high operating costs and the interruption of electricity supply (but see As for the panels that the concentration of last generation). The photovoltaic panels are used mainly to power devices away from electrical networks (space probes, the phone repeaters in the mountains, etc.) or with reduced energy requirements so that a connection to the grid would be uneconomical (light road signs, parking meters, etc.) and improper from an organizational perspective. Obviously, these devices must be equipped with batteries that can accumulate the electricity produced in excess during the day to power the equipment at night and during cloudy periods.


On April 8, 2010 is off to Switzerland on Solar Impulse HB-SIA, the first solar-powered plane.


With current technology photovoltaic panels are also sensitive to infrared radiation (invisible) of solar radiation and therefore produce power even in case of cloudy weather and rain. The amount of energy delivered is variable and unpredictable, this discontinuity makes it difficult to meet demand at all times current, less than a production with a wide safety margin above the peak annual demand.


So are solar and wind energy plants provide intermittent intermittently, but since the peak of production of solar energy systems in the summer it can offset the increased domestic demand due to air conditioners. The installation of photovoltaic panels has had its greatest development in Germany thanks to favorable legislation for which the producer sells the excess energy to the electricity supplier, which buys it at the same price per kWh. In practice, the city pays the bill the difference between what consumers and provides the body electric. If it is positive, get a credit. Similar legislation was recently introduced in Italy: in fact, September 19, 2005 came into force on the so-called "tariff", DL 387/2003 (transposing the European Directive 2001/77/EC).


Solar power provides only 0.1% of the power produced in German  and is therefore not a primary source of energy policy. The wind energy is less expensive (per kWh), but is probably not able to create similar employment levels.




Currently, most studies focus on new generations of solar cells with greater efficiency than current or photovoltaic cells with an efficiency similar to that of cells present but much cheaper. Studies point to the most ambitious construction of orbiting solar power stations. These plants should be collected directly from sunlight in space and transmit the power input to Earth by microwave or laser beams. Current construction projects such as {} comprising the installation of prototypes of these plants in the coming years.


Are being tested prototypes of solar cogeneration systems in which there is the simultaneous production of electricity and heat.


All over the world are currently studying new technologies and new ways to exploit the sun's energy to create the first true solar power plants include for example (CRS Central Receiver System) (eg project PS10) and the solar tower Australian made dall'EnviroMission Ltd of Melbourne.


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    • profile image

      anjana m m 

      2 years ago

      Solar energy its great and very useful to everyone

    • profile image


      3 years ago

      superb solar energy is very interesting

    • profile image


      4 years ago

      oh that's a great thing

    • profile image


      4 years ago

      ohhh solar energy its great that everything in the world is having the access to us it

    • stephhicks68 profile image

      Stephanie Hicks 

      7 years ago from Bend, Oregon

      Great overview of solar energy! I publish a lot on the topic and not everyone understand how it works, especially the difference between PV power and CSP. Rated up!

    • Ryan-Palmsy profile image

      Ryan Palmer 

      7 years ago from In a Galaxy far, far away

      it's a shame governments love to tax everything, and solar energy is so hard to tax. it'd be nice to see more clean energy that isn't going to run out at any time in the future! very useful!

    • Lita C. Malicdem profile image

      Lita C. Malicdem 

      7 years ago from Philippines

      Thank you for reiterating here the benefits of solar energy. It is free but resourcing it for our energy consumption sounds difficult yet this time. However, noble efforts of energy experts in many countries all over the world gives humanity hope. Let's trust and pray that finally, people can tame the sun's energy for good use. Useful, vote up!

    • Stigma31 profile image


      7 years ago from Kingston, ON

      Solar Power is the safest and purest of energies. The sun is an invaluable source and will not die for 1000's of lifetimes. This is going to be the power of the future. Voting up!


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