photovoltaic solar energy
La energía solar fotovoltaica consiste en la obtención de electricidad[30] directamente a partir de la radiación solar mediante un dispositivo semiconductor denominado célula fotovoltaica, o bien mediante una deposición de metales sobre un sustrato denominada célula solar de película fina.[31].
Photovoltaic solar panels
A photovoltaic panel consists of an association of cells, encapsulated in two layers of EVA (ethylene-vinyl-acetate), between a front sheet of glass and a back layer of a thermoplastic polymer (usually tedlar).[32] This assembly is framed in an aluminum structure with the aim of increasing the mechanical resistance of the assembly and facilitating the anchoring of the module to the support structures.[32].
The most commonly used cells in photovoltaic panels are silicon, and can be divided into three subcategories:
The standardized parameter to classify the power of a photovoltaic panel is called peak power, and corresponds to the maximum power that the module can deliver under standardized conditions, which are:
Typical efficiencies of a polycrystalline silicon photovoltaic cell range between 14%-20%. For monocrystalline silicon cells, the values range between 15%-21%.[36][37] The highest are achieved with low-temperature thermal solar collectors (which can reach 70% efficiency in the transfer of solar to thermal energy).
Photovoltaic solar panels do not produce heat that can be reused - although there are lines of research on hybrid panels that allow the generation of electrical and thermal energy simultaneously. However, they are very appropriate for rural electrification projects in areas that do not have an electrical grid, simple rooftop installations and photovoltaic self-consumption.
Development of photovoltaic solar energy in the world
Due to the growing demand for renewable energy, the manufacturing of solar cells and photovoltaic installations has advanced considerably in recent years.[38]
[39] Photovoltaic solar energy was traditionally used since its popularization in the late 1970s to power countless autonomous devices, to supply shelters or houses isolated from the electrical grid, but above all, increasingly in recent years,[40] to produce electricity on a large scale through distribution networks, either by injection into the grid or for domestic self-consumption.
Germany is, along with Japan, China and the United States, one of the countries where photovoltaics is experiencing the most rapid growth. By the end of 2015, nearly 230 GW of photovoltaic power had been installed worldwide,[41] making photovoltaics the third most important source of renewable energy in terms of installed capacity globally, after hydroelectric and wind energy, and already represents a significant fraction of the electricity mix in the European Union, covering on average 3.5% of electricity demand and reaching 7% in peak periods. production.[41].
The considerable installed power in Germany (38 GW in 2014) has set several records in recent years. In June 2014, it produced up to 50.6% of all the country's electricity demand during a single day, reaching an instantaneous power above 24 GW,[42][43][44] which is equivalent to the generating power of almost 25 nuclear power plants working at full capacity.[45].
Photovoltaic self-consumption and grid parity
Photovoltaic self-consumption consists of the small-scale individual production of electricity for one's own consumption, through solar panels. This can be complemented with the net balance. This production scheme, which allows electricity consumption to be offset by what is generated by a photovoltaic installation at times of lower consumption, has already been successfully implemented in many countries. It was proposed in Spain by the photovoltaic association ASIF to promote renewable electricity without the need for additional financial support.[48] The net balance was in the project phase by the IDAE.[49] and has been included in the Renewable Energy Plan 2011-2020[50] and Royal Decree 1699/2011, of November 18, which regulates the connection to the grid of electrical energy production facilities of small power.[51].
To encourage the development of technology with a view to achieving grid parity - equalizing the price of obtaining energy to that of other currently more economical sources - there are production bonuses, which guarantee a fixed purchase price by the electrical network. This is the case of Germany, Italy or Spain. This incentive scheme has already borne fruit, bringing the costs of photovoltaic energy below the sales price of traditional electricity in a growing number of regions.
The energy of the future
According to Greenpeace reports, photovoltaics will be able to supply electricity to two-thirds of the world's population in 2030.[52] And according to a study published in 2007 by the World Energy Council, by the year 2100, 70% of the energy consumed will be of solar origin.[53].
On the other hand, some countries, such as Tokelau, an archipelago located in the Pacific Ocean, do not have an electricity mix, since they obtain all the electricity they need from the sun.[54] The country is made up of about 125 islets that cover an area of 10 km² and has about 1,500 inhabitants.[55] The geographical location of the archipelago makes the use of fossil fuels comparatively much more expensive and difficult to implement. maintain than a photovoltaic system.
The Tokelau facility is an example that other countries in Oceania have already taken note of. In fact, the neighboring Cook Islands and the Tuvalu archipelago also intend to be completely supplied with renewable energy by 2020.[54].
Net balance and costs
Photovoltaic self-consumption consists of the small-scale individual production of electricity for one's own consumption, through renewable electricity equipment (photovoltaic solar panels, wind turbines), some of which are self-installable. It can be complemented with the net balance in autonomous installations or facilitate energy independence (disconnected installations).[56][57].
The net balance allows the excess produced by a self-consumption system to be poured into the electrical grid in order to be able to use that excess at another time. In this way, the electric company that provides the electricity when the demand is higher than the production of the self-consumption system, will deduct the excesses discharged into the network consumption from the bill.
In recent years, due to the growing rise of small renewable energy installations, self-consumption with net balance has begun to be regulated in various countries around the world, being a reality in countries such as Germany, Italy, Denmark, Japan, Australia, the United States, Canada and Mexico, among others, due in part to the constant drop in the cost of photovoltaic modules. To help achieve this goal, many countries are also launching grants, subsidies[58] or tax aid to help citizens and companies finance these types of facilities.
In 2013, the price of solar modules had fallen by 80% in 5 years, putting solar energy for the first time in a competitive position with the price of electricity paid by the consumer in a good number of sunny countries. The average cost of electricity generation from solar photovoltaic energy is already competitive with that of conventional energy sources in a growing list of countries,[59] particularly when considering the time of generation of such energy, as electricity is usually more expensive during the day.[60] There has been stiff competition in the production chain, and further falls in the cost of photovoltaic energy are expected in the coming years, posing a growing threat to the dominance of solar-based generation sources. fossil energies.[61] As time goes by, renewable generation technologies are generally cheaper,[62][63] while fossil energies become more expensive:.
In 2011, the cost of photovoltaics had fallen well below that of nuclear energy, and is expected to continue falling:[65].
The trend is for prices to decrease further over time once photovoltaic components have entered a clear and direct industrial phase.[67].