Solar panels come in two varieties, solar photovoltaic and solar thermal. Solar PV is the technology that turns sunlight (or more precisely most light sources) into electrical energy. Solar thermal captures the heat from the Sun and the energy is transferred to heat water usually for your domestic hot water system.
As far back as 1839 was probably the birth of the idea of solar power. French physicist Alexandre-Edmond Becquerel discovered the photovoltaic effect. This basically means the discovery that when certain materials are exposed to light they generate a current.
Several other notable scientists and inventors experimented with the photovoltaic effects of different materials until in 1954 Gordon Pearson discovered silicon was a good material to use. It took over 100 years to increase the efficiency of the materials to about 6 percent.
Today there are over 30 significant solar panel manufacturers around the world. Countries such as Germany, USA, Japan and China have the most manufacturing companies.
There several types of panel being produced with varying efficiencies and different technologies just like there are many different types of car. The main types of solar panel in use and commercially available in the UK are Monocrystalline, Polycrytalline and Amphorus. The latter being the newest technology that actually covers a range of thin film solar cells. Thin film silicon cells use a fraction of the amount of silicon as crystal silicon cells.
Thin Film technologies are currently not as efficient but are becoming more so. They have the advantage of being cheaper to manufacture and are able to be made in to flexible panels to fit round curves. These newer types include copper indium gallium (di)selenide (CIGS) and cadmium telluride CdTe.
Sometimes different layers of Crystalline and non-crystalline materials are use to increase efficiency and performance. This has also lead to many new exciting innovations in solar including flexible solar panels, transparent see through solar panels, solar concentrators and dye-sensitized solar cells.
Obviously cost will be a defining factor when choosing your panel. Cost is not necessarily the best measure of value. If you bought a cheap second hand car it would initially cost less but not last as long and not be as efficient. The same is true for solar.
You should take into consideration the energy density of the panel, that is how much energy your panel can create per a given area. This is an even more important factor on smaller roofs where you may not be able to fit on as many panels.
Every manufacturer gives a guarantee with their panels. There are two types, one covering the structural performance and the other covering the power output performance. The normal guarantee is 5 years for structural ie if the panel fall apart or break. The power lifetime guarantee is usually for 25 years ie they guarantee the panel will produce electricity at a minimum 80% efficiency for 25 years.
Not all panels are created equally. When a panel is manufactured it is tested to find it's rating. Generally the same type of panel will have the same level of efficiency. However there are many different types of technology and manufacturing processes which these days can mean panels that are up to 25% efficient. The standard rating is about 12 to 18% for most types available to buy in the UK. The latest technology being used means that the panels will perform better under lower light and diffuse light conditions as experienced during the Winter months and on cloudy days. These will perform better in countries such as the UK.
Why is efficiency an important consideration? The more efficient a panel is the more sunlight it will be able to turn into electricity. This in turn means more free electricity for you and higher tariff payments if you are claiming them for yourself. If you are comparing different types when buying you should take into account their efficiencies as well as price.
One question often asked is how much do solar PV panels cost? This is a bit like asking how much does a car cost? It really depends on which one you buy. Typically you would not be looking at how much individual solar panels cost but comparing whole photovoltaic systems which include the panels, the panel roof mounts, inverter and a certified installer.
Typically systems start from around £4,000 per kW installed. Excluding the actual panels you could expect to pay around £3,000 for the inverter, mounts and installation costs. This means it is generally more cost effective to buy a larger capacity system as you are then only paying for the additional panels and mounts.
A typical installation is about 2.2kWp (kilowatt peak). Depending on the available roof space and you electricity needs a system between 1.7 and 3.7kWp could be installed.
The standard guarantee from most manufacturers is that the panel will last for 25 years. Their power output does slowly decline over time but it is generally expected that they will last for 30 years or longer under normal conditions. Some panels installed in the seventies are still working 40 years later.
It is important to note that all panels work at their best when new and become less efficient over time. Typically they drop to 80% capacity after 20 years. Newer panel technologies are expected to perfume better over longer periods and last longer.
It was in 2010 that free solar panels first became available in the UK due to the governments feed in tariff (FITs). A similar scheme had already been running in the United States since 2006 with the power purchase agreement.
The FIT's scheme means that you are paid for all the renewable energy that you create. Anyone can benefit from these payments as long as the system that you get installed is MCS certified and the installer is certified under the same scheme.
Not everyone can afford to buy their own system so there are some free solar panel installers who will provide and maintain a system at no cost to you. You will have to meet their installation requirements in order to qualify. The benefit to you is that you get free electricity for a guaranteed 25 years.
Not everyone is going to want to or be able to afford the cost of installation and others may not be eligible for the free offers. So what is the alternative to solar panels? If you want to green you energy usage on way to do this is to switch to one of the green energy suppliers in the UK. It is a lot easier than it used to be and switching to a green tariff does not necessarily mean it will cost you more as many suppliers will match prices.
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Grants & Schemes
A roof facing as far as a West-South-West (almost West facing) direction or East-South-East (almost East facing) can still potentially generate up to 90 percent of a roof facing South.
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