What Is Solar Energy?
Solar energy is the energy associated with solar radiation and represents the main source of energy on Earth.
From this energy, it is derived more or less directly from almost all other sources of energy available to man, such as fossil fuels, wind energy, tidal or wave energy, hydroelectric energy, energy from the biomass The only exceptions are nuclear energy, geothermal energy and tidal energy. It can be used directly for energy purposes to produce heat or electricity with various types of systems.
From the energy point of view, it is an alternative energy to classic fossil fuels, it is considered a renewable energy. Solar energy can be properly exploited through different technologies and for different purposes, even if in technological versions that do not include energy storage.
Solar installations suffer the variability and intermittency of production or complete non-programmability due to day-night cycles and cloudy days.
Solar energy utilization technologies
Today, solar energy is generally understood as the energy that people themselves generate with their technology directly from solar radiation. This is currently happening in Western Europe in two main ways:
- The most used application is through solar panels with photovoltaic cells. Photovoltaic panels convert light directly into electricity.
- Another way to take advantage of solar radiation is thermal solar energy, where sunlight is converted into thermal energy. This conversion is done by solar water heaters or solar collectors.
- Passive solar energy Passive solar energy systems are characterized by the use of solar energy if no external energy input. For example, architectural designs that allow maximum solar radiation in winter and that avoid excessive heat in summer.
The term solar panels is used for both methods. Anyway, the design is noticeably different depending on what type of solar technology is going to be used:
The solar thermal panel uses solar rays to heat a liquid with special characteristics, contained inside, that transfers heat, through a heat exchanger, to the water contained in a storage tank. In these cos the thermodynamics plays a fundamental role.
The photovoltaic panel exploits the properties of particular semiconductor elements to produce electrical energy when subjected to solar radiation. Thanks to the so-called photovoltaic effect, solar exposure causes the movement of electrons from a component (usually silicon), generating a continuous electric current.
There is also the concentration solar panel that uses a series of parabolic mirrors with a linear structure. The objective of these mirrors is to transport the sun's rays over a receiving tube that circulates a heat transfer fluid or a series of flat mirrors that concentrate the rays at the end of a tower. In both cases, the receiving device is heated to very high temperatures (400 ° C ~ 600 ° C).
Solar energy applications
Currently, solar panels are used to supply domestic hot water (solar thermal energy) and heating to homes and small building complexes. Solar power plants have been built that, using steam turbines, convert stored heat into electricity. However, these prototypes have not found wide application due to the low performance of these power plants compared to the high administration costs and the discontinuity of the electricity supply.
Photovoltaic panels are used in isolated solar systems to power devices away from electrical networks (space probes, high-altitude telephone repeaters, etc.). They are also used in applications with such low energy demands that a connection to the electricity grid would not be economical (light signals, parking meters, etc.) Obviously, these devices must be equipped with accumulators capable of accumulating the excess electricity produced during the day to power the equipment during the night and during cloudy periods, usually solar batteries.
They are also used in large systems connected to the network, although the amount of energy supplied is variable in both daily and seasonal conditions and, therefore, is difficult to predict and not programmable. This discontinuity makes it difficult to meet the demand for electricity at any time, except for production with a wide margin of safety above the annual demand peaks. However, being the peak of production of solar power plants in the summer, it manages to compensate for the greater internal demand due to air conditioners.
Advantages and disadvantages
The main criticisms or inconveniences about the use of solar energy are attributable to the costs, efficiency and intrinsic characteristic of the intermittence or non-programmability of this energy source compared to conventional energy sources, since it is directly affected by the cloud cover and the total absence during the night. In addition, a large amount of energy is needed to produce photovoltaic panels, often using non- renewable energy sources such as coal.
On the other hand, we must consider the advantages of solar energy. Its advocates support a reduction in costs and an increase in efficiency in the near future due to economies of scale and the technological improvement of future solar systems. Regarding the absence of this energy source during the night, they also point out that the maximum peak of electricity consumption is actually reached during the day, that is, during the maximum production of solar energy.
Last review: October 3, 2019