Energy for concerned consumers



Photovoltaic Systems


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 P/V Systems

The main categories of P/V systems are as follows:

Consumer products (1 mW – 100 Wp)
The systems in this category are used in small scale applications, such as mobile homes, recreational boats, garden lighting, refrigeration and for products such as small portable computers, lanterns, etc.

Autonomous or microgrid systems (100Wp – 200kWp).
This category includes electricity generation systems for homes and small villages which are not grid connected. They are also used for:

Supplying electricity to monasteries

Desalination/pumping/purification of water

Outdoor lighting systems for roads, parks, airports, etc.

Telecommunication systems, remote measurement, and alarms.

Traffic control systems for roads, shipping, air navigation, etc.

Agricultural applications such as water pumping, aquaculture, refrigeration for agricultural products and medicines, etc.

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.

Also, P/V arrays can be used as part of the structure of buildings, if they are designed properly. In this way the economic effectiveness of the system can be increased because the cost of ordinary building materials is avoided.

Characteristics of P/V Systems

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.

The user's energy independence is the greatest advantage of P/V systems. The value of the energy produced by P/V systems is comparable today to the price for peak power which power producers charge their customers.

P/V systems can play an important role in so-called Distributed Power Generation, which is the new development model for modern energy systems for production, transmission and distribution of electricity. The diversification of energy production which P/V systems can provide in combination with considerable reduction of dependence on oil and preventing further environmental pollution, can stimulate economic development in the new energy landscape which is now coming into being in developed countries.

Factors Influencing the Development of P/V in Greece

The International Market for P/V Systems

P/V Systems Applications in Greece