An Introduction To Photovoltaic Systems

A solar photovoltaic system is designed to generate electricity by turning sunlight into electrical power. There are several components in any PV system with the simplest being a small 12 volt solar panel connected to an electrical device such as a 12 volt fan. As the suns light hits the panels a current is generated which then powers the fan. A battery could be added to this simple system so that the power generated is used to charge the battery.

In practice this type of simple system would not be of much use, if a battery was being used in this type of set up usually a charge controller would be added to prevent over or undercharging. A switch may be added so that you could turn the fan on and off and usually a casing would be designed for the system to stop the delicate parts from being exposed to the elements.

How photovoltaic systems work

Photovoltaic systems are designed to provide useful energy to run electrical systems. This may be in a home, on a boat or even a motor home or caravan. Essentially photovoltaic solar panels work the same way no matter how the system is designed. The power house of any system are the photovoltaic cells, a series of cells is used to make up the solar panel most people recognise.

A solar cell is made of from silicon, silicon wafers are usually connected in series to create a more powerful current. As the silicon and the metals used to create the junctions and connections are quite delicate they are encapsulated into a module which most people refer to as a solar panel.

Silicon has special properties that allow it to generate an electrical current when exposed to light, typically sunlight. The light (photons) are absorbed by the silicon material dislodging electrons from their atoms allowing them to move through the silicon which generates the current.

PV systems only work when the front of the panels where the silicon cells are exposed (under a protective glass surface) are exposed to light. The light source can be any but it is generally the sun as this is the strongest free source of light energy. The brighter the light the more electricity will be produced; solar photovoltaic panels work when exposed to light and not heat. They produce the most power when the sun is shining (direct light) but will still work when it is overcast or cloudy (diffuse or indirect light).

Renewable energy

Photovoltaics are part of a group of systems that generate renewable energy. Renewables include other technologies such as wind turbines that produce electricity from the wind. Solar PV and wind power work well together and you will often see road signs with a solar panel and small wind turbines that generate the electricity for the sign. It is usually either sunny or windy so whilst one may not be working or not working to full capacity the other usually is.

Types of solar photovoltaic system

There are different types of solar photovoltaic system that are designed for different situations and different geographical locations. The most common types are the polycrystalline and monocrystalline types of solar panel. These can be recognised by their rectangular shape and dark blue or black coloured surface. Another type is the never thin film technologies which can literally be any shape but tend to be rectangular. This group of technologies include the flexible type that can be adhered to arched, cylindrical or other non-flat surfaces.

Additionally there are also the solar PV-T panels that combine solar thermal with solar photovoltaic technology. The idea behind this type of combined system is to create a more efficient use of limited roof space and increase solar PV efficiency as the thermal part of the panel keeps the photovoltaic part of the panel at a lower operating temperature.

Photovoltaic roof tiles

Most solar installations use the traditional rectangular panels that are fixed to the roof above the existing roof tiles. This is generally the most cost effective option for retrofitting panels to the roofs of homes, businesses and industrial building. There is a move towards what has been termed BIPV (built-in photovoltaics) which integrates the technology into the fabric of the building. On new builds this reduces the cost of materials as the photovoltaic technology acts as both the panel and the outer fabric of the building.

One of the most popular domestic BIPV renewable technology is the photovoltaic roof tile. This is essentially a small panel designed to act like a roof tile and be a direct replacement for the tile. The PV tiles can then be used in place of traditional slate or concrete tiles. These are usually used on new builds or when an old roof needs replacing as the solar tiles are slightly more expensive than traditional panels so the costs can be offset as fewer roof tiles are needed where solar tiles are used.

How much do photovoltaic systems cost?

I have extensively covered solar panel cost and how much are solar panels. The cost is going to vary dependant on the size of the installation, the larger the install the higher the cost. System size for domestic use are measured in kilowatts and tend to range in size up to just under 4kWp, the reason the figure is just under 4kWp is because the cut of point for the higher feed-in tariff payments is below this figure.

Most people will tend to look at the price of the photovoltaic systems installation that includes the complete price including installation. Most people tend not to do their own DIY solar system as it means they will not be able to claim the solar grants. You have to have an MCS accredited system installed by an MCS qualified installer in order to claim the feed-in tariff payments.

Solar PV systems are more cost effective the larger the system is so a system nearer the higher end of system sizes designed for residential properties have a lower cost per watt or kilowatt. The reason for this is not due to economies of scale, you won't get any discount for such a low quantity purchase of panels. Instead to cost effectiveness comes from the fact that there are other fixed costs such as the scaffolding, labour costs and cost of the solar inverter, solar panel fixings, wiring and other parts needed for a working system. As you have already paid for the fixed costs of the system adding additional panels will only add a small percentage to the overall costs.

For the largest system you can expect to pay anywhere from £14,000 fully inclusive. A smaller system tend to be in the £4 - 6,000 range. You will however only get the most competitively priced system if you compare prices by getting at least 3 quotes. Recent research I did for the site found that you could easily save 40% by comparing solar prices and in some cases up to 70%.