Photovoltaics (PV)

What is it?

Photovoltaics means converting sun's radiant energy directly to electricity using semiconductors that feature the photovoltaic effect (in which the electrons of the semiconductor material absorb the incoming radiant energy, becoming free to move in the material and thereby increasing the material's electric conductivity).

The term "photovoltaic" is a combination of the Greek word for light "photos" and the name of the electromotive force "volt".

How can I benefit from it?

With a wisely chosen PV-system you can cover a major fraction of your annual electricity expenses (just check out the simulation)! The ability to produce solar electricity is of course highly dependent on your location but electricity consumption is typically somewhat constant throughout the year, so major savings in summertime can be achieved also in northern locations.

Operating a domestic PV-system is simple and doesn't require special expertise. By utilizing solar electricity you will become a forerunner in the field of energy efficiency and you will set an example to everyone around you.

How does it work?

Solar electricity is generated within photovoltaic modules which are comprised of many interconnected solar cells. A solar cell is the basic generation unit of solar electricity, in which the photovoltaic effect occurs. It is a thin, flat "wafer" of light sensitive semiconducting material. The two faces of the wafer have been chemically manipulated and are therefore separated by what is known as a p-n junction. When illuminating the p-n junction the electric field caused by the junction itself causes the accumulation of positive and negative charge on different sides of the junction creating a voltage. The voltage applied across the p-n junction will allow electric current to flow in one direction but not in the other.

The number of individual solar cells connected in series and parallel determines the voltage, current and the power produced by the photovoltaic module in given circumstances. Modules can further be connected together to form a solar array with desired properties.

A simple grid connected solar electricity system consists of a solar array (or several arrays), an inverter (with which the produced direct current (DC) is converted to alternating current (AC) with the properties of the local electric grid) and connecting wires. The inverter must have a power rating that corresponds to the system size. The electricity produced can either be used or fed to the grid. The grid acts as a storage medium and depending on the local electricity provider the user may be able to sell the produced excess electricity to the grid.

An off-grid solar electricity system will require more components. When no grid is available the produced electricity must be stored into batteries. To protect the batteries from overcharging a charge controller needs to be connected between the solar array and the batteries. To minimize losses, the storage unit can be optimized to meet the requirements set by the load and the solar arrays used. If the load uses direct current, an inverter is not needed (but in case of different size DC-loads a DC-to-DC converter will be necessary). In absence of an inverter the system will however require a charge controller between the storage unit and the load to ensure the batteries do not deep discharge. If there is an AC-load in the system, an inverter is needed between the storage unit and the load. Most of the modern inverters have built-in charge controllers so in this case no extra controller needs to be connected in series with the inverter. Off-grid system sizing is based on the loads and the time of autonomy, that is the time the system must be able to operate without incoming solar radiation.

Like with all electrical applications introducing a PV-system to your house requires professional installation services. You may also want to consult professionals about optimizing the system to your needs, but you can also easily get a realistic idea of the potential to produce solar energy at your location by running simulations in Solar Arena!

Global effects

Introducing PV-power to the world on a large scale will significantly lower the emissions caused by the carbon based energy production methods today. Unlike for fossil fuel technologies the future of PV seems bright as the most used PV resource silicon is abundant in the world. Like with solar thermal heating the popularity of photovoltaics has thus far been limited by the required individual effort, energy legislation and above all general unawareness. Our goal is to bring the products, services and up-to-date knowledge about solar energy to everyone in a clear and simple way and to boost the solar markets to a new era.