Solar energy

Solar energy. Energy produced by the sun and which is converted into useful energy by humans , either to heat something or to produce electricity .


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  • 1 Historical Review
  • 2 Principle of operation
  • 3 Solar thermal energy
  • 4 High concentration devices
  • 5 Low concentration devices
  • 6 Photovoltaic solar energy
  • 7 Solar cell
  • 8 Advantages
  • 9 Applications
  • 10 Characteristics of solar radiation in Cuba
  • 11 Curiosities
  • 12 See also
  • 13 External link
  • 14 Sources

Historical review

In 1887 Heinrich Hertz studied the emission of electromagnetic waves when sparks jump between two electrodes, when he noticed that charges jump more easily if the electrodes were illuminated by ultraviolet light . Then it was verified that the light caused the emission of electrons in the metals. This phenomenon was called an external photoelectric effect.

In the semiconductors the internal photo effect was discovered, which causes the appearance of charges in the material when it is illuminated, separating these charges generates a difference in electrical power that can be used to circulate electrical current through a circuit, illuminating a room, or operating electrical equipment, etc. and is called Photovoltaic Effect.

This was first observed in 1896 by Becquerel, and in the early 1950s scientists at the Bell Telephone Laboratories in the United States, who developed the first transistor, built the first silicon solar cell with profitable efficiency. (6%).

Since 1975 research on photovoltaic solar energy has been carried out, they have been focused on increasing the efficiency of converting solar radiation into electricity, increasing the stability of solar cells for various types of technologies and reducing their manufacturing costs and photovoltaic solar modules. Virtually all options and types of photovoltaic cells have been investigated.

Operating principle

  • There are two main ways to use solar energy:
  1. . Heat source for solar thermal systems.
  2. . Electricity source for photovoltaic solar systems.

Thermal solar energy

Thermodynamic energy – Process

Thermal solar energy, which uses the heat generated by solar radiation to produce electricity, is a valid resource both in electricity production through large power plants and in various applications for domestic use.

-The thermal power plants using solar thermal energy basically use two types of devices:

High concentration devices

They capture solar radiation through systems such as curved mirrors or parabolic disks, which are oriented towards the Sun and reflect its light by concentrating it at one point. From there the heat is transferred to a fluid, which can be water, oil, air, etc., through which the heat is transferred to a water tank, which evaporates at high temperatures, which is used to move a turbine and thus generate electricity.

Low concentration devices

They bring together several parabolic cylinders that also move with the Sun by concentrating the radiation in a pipeline that contains a fluid, which is heated and transported to a pipe network designed to minimize heat losses. These low concentration devices are the most technologically developed and are also central ones that take up less space. One of the big drawbacks of these devices is that it depends on an irregular source such as the Sun, so they need no clouds, although thermal storage systems are available.

Photovoltaic Solar Energy

Photovoltaic conversion is based on the photovoltaic effect, which consists of creating an electrical power caused by the absorption of solar radiation. To carry out this conversion, devices called solar cells are used, consisting mainly of semiconductor materials in which an internal electric field has been artificially created.

Photovoltaic process

The most used material is Silicon . These cells are connected to each other as a series circuit in order to increase the output voltage of the electricity, that is, if it will be 12 volts or 24. At the same time, several parallel circuit networks are connected to increase the capacity of electrical production that You will be able to provide the panel.

Since the type of electric current that solar panels provide is direct current, many times an inverter and / or power converter is used to transform direct current into alternating current , which is what we usually use in our homes, jobs and shops.

Solar cell

-A solar cell basically works as follows:

Photovoltaic solar cell

The photons, which come from solar radiation, hit the cell surface and are absorbed there by semiconductor materials, such as silicon. The photons hit the electrons freeing them from the atoms to which they belonged. Thus the electrons begin to circulate through the material, and thus produce electricity.

This basic operation is repeated regardless of the material used in the solar cells, as long as of course it has conductive properties and absorbs light .


  • As no type of combustion occurs, no air pollutants are generated at the point of use, nor are there any effects such as acid rain, CO2 greenhouse effect , etc.
  • Silicon, the base element for the manufacture of photovoltaic cells, is very abundant, and it is not necessary to exploit deposits intensively.
  • As it is a fundamentally local energy, it avoids tracks, cables, poles, large electrical lines are not required, and its visual impact is low, nor does it have excessively large requirements for land (1kWp can occupy between 10 and 15 m2).
  • Virtually energy is produced with total absence of noise.
  • It does not require any external supply (fuel) or relevant presence of other types of resources (water, wind).


  • Drinking water
  • Solar stoves
  • Drying
  • Evaporation
  • Distillation
  • Refrigeration

Characteristics of solar radiation in Cuba

One of the important aspects to determine the convenience of the use of solar equipment is the knowledge of the characteristics of solar radiation in the place, both its daily and hourly variation. The intensity of solar radiation in Cuba has a considerable value between 900 and 1 000 W per square meter (W / m2) when it falls perpendicularly on a surface, which means an approximate average of 400 W / m2 on the surface of the earth and more than 5 KW / h per day per square meter, as an annual average value.

The variation from one place to another in the country is not significant, due to its geographical position, stretched from east to west and between 20º and 23º north latitude.
Nor is the variation between summer and winter as significant as in other countries, so in Cuba solar radiation can be used anywhere and at any time of the year.

Unlike the dry continental countries, the cloudiness in Cuba is very high, mainly due to the seas that surround it. Diffuse radiation has an average value greater than 40%. The average number of cloudy days per month is greater than 10, although it is difficult to find a day that the Sun does not rise even for a moment.

The greatest insolation occurs from 10 am to 2 pm solar time, that is, approximately, from 10:30 am to 2:30 pm in Havana (11:30 am to 3:30 pm, summer time) and from 10 am at 2 pm in Santiago de Cuba (11 am to 3 pm summer time). The Cuban climate is also accompanied by high humidity and frequent rains from May to October.


1.- The largest solar power plant in the world is located in Portugal, in the town of Amareleja, known as the Portuguese town where the sun warms the most, the plant has more than 262,000 photovoltaic panels installed. The plant will produce up to 93 gigawatt per year, a power that will allow thousands of homes to be supplied with energy.

2.- Japan’s largest shipping company, Nippon Yusen, ensures that it will soon install solar panels on one of its largest ships, which by the end of this year will already sail the seas partially moved by this energy source. The capacity of these panels will be 40 KW and will save more than 6 percent in fuel, as well as between 1 and 2 percent of polluting emissions into the atmosphere (20,000 tons of C02 per year).

3.- Halcón Solar photovoltaic boat.The presentation of the photovoltaic boat, built in Cuba, to national tourism managers was held in the waters of the Hanabanilla reservoir, on August 13, 2001, and for six months it served the tourists from the hotel facility of the place in long journeys of contemplation, with very favorable technical results and great acceptance.
In perspective, conditions are created to link towns with difficult access by waterway, and various requests for tourism are studied, since due to its characteristics it is appropriate for tourist and recreational activities of high environmental sensitivity, in which it is not possible use traditional motor boating.

4.- Photovoltaic Solar Energy in cars. Private cars that incorporate photovoltaic solar energy continue to come onto the market. This time, it is the American brand of electric cars ZAP. Your Xebra Xero model, pictured, is sold with the option of a 150 Watt rooftop photovoltaic module. Using photovoltaic power to power your electric motor also has a positive impact on lengthening battery life. and the zero use of fuels.

5.- The solar plane crosses Europe. The European skies have already welcomed the Sunseeker II, the only manned solar plane in the world, which has just started a journey through different countries in Europe with the aim of breaking a record. The tour started in mid-April in Zurich (Switzerland), where the airplane has spent almost a year doing training flights and perfecting the systems. From there, Eric Raymond, a pilot, crossed Switzerland crossing the Mattehorn or Matterhorn, the best-known mountain in the Alps located on the border with Italy, until reaching Turin, before returning to Switzerland.
A second stage will take the plane to the Dolomites, the best-known mountain range in Austria, Hungary and Slovenia. After a stellar appearance at the World Air Games in Turin, where she will fly with the Icare II, a solar plane from the University of Stuttgart, she will head to Spain.
It reaches heights of up to 4,500 meters and speeds of 65 kilometers per hour.

6.- In Cuba, radiant energy from the sun of around 2000 KW / h is received in a year, that is, between 5 and 6 KW / h each day.

7.- In each square meter of Cuban territory, an amount of solar energy equivalent to 0.5 Kg of oil is received daily.

8.- On very clear and cloud-free days, approximately 30% of terrestrial radiation is lost by reflection into space and by dispersion and absorption in the layers of the atmosphere. Ozone absorbs ultraviolet and CO2 and water vapor.

9.- How much energy is consumed in Cuba for water heating?
If we assume that only 5% of Cuban families heat 2 liters a day per person, for 300 days a year, with electricity, oil, kerosene or gas, it would be equivalent to a consumption of 15,000 tons of oil.

10.- The sundial of Plaza Martiana, in Las Tunas, built on a horizontal surface, is possibly one of those built in Cuba, the one with the most originality, since the Sun indicates, with its change in declination according to the day of year, the most significant biographical events in the life of José Martí. But the most interesting element of this watch is that every May 19, at two thirty in the afternoon (time when the Apostle fell), the sunlight reflected by a mirror illuminates the countenance of the Master, recalling his desire to die facing the Sun.
11.- It is recognized that the first design of a solar chimney was made by the Spanish Isidoro Cabanyes in 1903. Later, in 1931, the German Hanns Gunther designed a power plant that used a solar chimney.

In 1975, Roberto Lucier carried out important patents on the subject, and in 1982, in Manzanares, Spain, the first power plant with a useful social power solar chimney was built, with 50 KW of power, 195 m height, tower diameter 10 m and the solar energy collection area with a diameter of 240 m. Currently the largest project in execution is in New South Wales , Australia , a gigantic chimney with a height of 1000 m, 150 m in diameter and a solar energy collection area with 5 km in diameter, with a capacity of 200 MW , using 32 6.25 MW turbines.


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