What is Photovoltaic solar energy?
The word Photovoltaic (PV) is composed of two terms: Photo – Photon which means “light” and Voltaic from “Volt” which is the unit used to measure electric potential at a given point.
Photovoltaic systems use cells to convert sunlight into electricity. PV cells can be made from different so-called semiconductor materials. Today, silicon is the most widely used material, but other, usually compound (made from two or more elements) semiconductors is also used. They are silent and non-polluting, utilise a source of energy that renews itself, and require no special training.
What is a Photovoltaic system?
A photovoltaic (PV) system is a system which uses solar cells to convert light into electricity.
A PV system consists of multiple components, including cells, mechanical and electrical connections and mountings and means of regulating and/or modifying the electrical output. Due to the low voltage of an individual solar cell (typically ca. 0.5V), several cells are combined into photovoltaic modules, which are in turn connected together into an array.
PV systems can be used for homes, offices, public buildings or remote sites where grid connection is either unavailable or too expensive. PV systems can be mounted on roofs or on building facades or operate as a stand alone system. The innovative PV array technology and mounting systems means that PV can be retrofitted on existing roofs or easily incorporated as part of the building envelope at construction stage. Modern PV technology has advanced rapidly and PV is no longer restricted to square and flat panel arrays but can be curved, flexible and shaped to the building design.
“Grid connected” means that the system is connected to the electricity grid. Connection to the local electricity network allows any excess power produced to feed the electricity grid and to sell it to the utility. Such a PV system is designed to meet all or a portion of the daily energy needs. Typical on-grid applications are roof top systems on private houses.
What is a Photovoltaic system composed of?
Elements of a grid-connected PV system are: PV modules – converting sunlight into electric power, an inverter to convert direct current into alternating current, sub-construction consisting out of the mounting system, cabling and components used for electrical protection, and a meter to record the quantity of electric power fed into the grid.
Off-grid (stand-alone) systems use charge controllers instead of inverters and have a storage battery for supplying the electric energy when there is no sunlight e.g. during night hours.
How much electricity does a Photovoltaic system produce?
The electricity production of a PV system depends on external (environmental conditions) and internal (technology, layout of the system) parameters.
The efficiency of the PV module depends on:
- The size of the PV system and its technology
- The orientation of the PV module towards the sun. The optimal orientation for locations above the Ecuador is the south.
- The tilt angle or inclination of the roof. For European countries, the average optima inclination is 30-35 degrees
- The irradiance value on site
- The climate zone.
Shadows on the modules (also if they appear only at certain times of day) reduce significantly the gain of the whole system and should be avoided.
Is it worthwhile using solar energy in Europe?
Definitely! In Germany for example, the average annual solar irradiance is 1000 kWh per square metre. With efficient solar power systems, this is sufficient to generate a considerable volume of electricity and heat from solar power.
Obviously Southern regions will reach grid parity and profitability more quickly.
Hence it is worthwhile producing solar energy in Europe, not least because this makes Europe less dependent on energy imports but also because:
- The fuel is free
- It produces no noise, harmful emissions or polluting gases
- PV systems are very safe and highly reliable
- It brings electricity to remote rural areas
- The energy pay-back time of a module is constantly decreasing
- It creates thousands of jobs
- It contributes to improving the security of Europe’s energy supply.