The photovoltaic phenomenon was discovered in 1839 and was used for practical purposes at the end of the 1950’s in space applications powering satellites. Photovoltaic systems (P/V) can convert solar energy to electricity. A typical P/V system is composed of a P/V module or solar electricity generator and the electronic systems which manage the electricity produced by the solar array. In autonomous systems, there is also an energy storage system which uses batteries.
A typical P/V array is composed of one or more P/V modules with electrical connections between them. When the P/V modules are exposed to solar radiation, they convert around 14% of the incoming solar energy to electricity. The conversion of solar energy to electricity is quiet, reliable and does not have an impact on the environment.
Categories of on-grid photovoltaic systems
Large Grid Connected P/V Systems
Included in this category are P/V electricity production plants ranging in size from 50 kWp to several MWp which deliver the electricity directly to the grid.
Connected P/V Systems – Household Sector
This category includes P/V systems with a typical size between 1,5 kWp and 20 kW, which are installed on the roofs or facades of houses and supply electricity directly to the building. Surplus energy is sent to the grid. Again, this category comprises the largest part of the global market for P/V systems.
The benefits from incorporating P/V into buildings are:
Coincidence of summer cooling loads for buildings with the P/V system output at its maximum.
Land surface is not needed for installation.
Decentralization of energy production and local consumption of the energy produced.
The basic characteristics of P/V systems which differentiate them from other forms of renewable energy are:
Direct electricity production, even on a very small scale, for example, several tens of W or mW.
Ease of use. Small systems can be installed by users.
They can be installed in cities, incorporated into buildings where they do not visually disturb the surrounding environment.
They can be combined with other energy sources (hybrid systems).
They are scalable systems, which means that they can be expanded later on to meet users' increased needs without disposing of the original system.
They are quiet, non polluting and do not have an impact on the environment.
They are practically maintenance free.
They have a very long life and operating reliability. Manufacturers guarantee more than 25 years of good operation for their P/V generators.
Photovoltaic systems have a lot of benefits for the environment and society. Benefits for the consumer, for the energy market and for a viable development.
Solar energy is clean, inexhaustible, mild and renewable. Solar energy isn’t controlled by anyone. It’s an inexhaustible domestic energy source that provides independence, predictability and safety of the energy supply.
Photovoltaic systems which transform solar energy into power are considered to be the ideal system for energy transformation, since they use solar energy which is the most available energy source in the planet and produce power which is the most useful form of energy.
Photovoltaic systems are silent, reliable and have a long life time, the ability to expand according to any requirements, ability to store the produced power (into the grid or using batteries) and require minimum maintenance.
The environmental advantages of photovoltaic systems are unquestionable. Every kilowatt per hour, that is produced by photovoltaic systems and not by conventional fuels, saves the atmosphere from one kilogram of carbon dioxide (based on today’s energy mixture in Greece and on the average losses of Grid). A standard photovoltaic system of 1 kilowatt saves the atmosphere from 1.3 tn of carbon dioxide every year, the same amount of dioxide that would be absorbed by a 2-acre forest. It also prevents the emission of other dangerous pollutants (such as floating particals, nitric oxides, sulphur combinations, etc). The emission of carbon dioxide sets off the greenhouse effect and changes the earth’s climate, while the pollution of the atmosphere has serious repercussions on people’s health and on the environment.