The doom and gloom of the British winter in January, while not particularly cold, certainly lacks the solar energy you would expect to generate enough electricity from solar panels. Planning to make the most of scant solar resources, a manufacturer of what are considered the most efficient solar units on the market has announced that they have received MCS accreditation and are ready to install in the UK.

The Microgeneration Certification Scheme (MCS) accreditation is required before manufacturers can release their panels onto the UK market. Currently operational across the rest of continental Europe, the HIT series of pv cells produced by SANYO are a leader in energy conversion with a rate of around 21.6 per cent. This makes them a world leader in energy conversion efficiency and will certainly make them a sought after commodity throughout the British solar market.

The highly efficient HIT cells will operate under the feed-in tariff in the UK. The feed-in tariff is legislation which guarantees a fixed, premium rate for units of energy both used and fed back into the grid by solar micro-generators of less than 5kw. This means that British consumers will be able to benefit from increased revenues from solar panels able to generate more units of energy than competitor modules under the same solar conditions. The new panels which will become available from the 31^st March 2011 will also mean that less roof space is required to generate energy, broadening the scope of households where solar installations are a viable option.

With the recent announcement that a number of foreign solar manufacturers are preparing to invest in the UK in order to take advantage of the feed-in tariff, the arrival of the HIT solar modules highlights how crucial the tariff legislation is in encouraging investment in our burgeoning renewable market. With the boost this will give to the economy in an already struggling manufacturing sector and job creation in green energy, hopefully Cameron’s government will take this on board and continue to give their backing to the legislation which makes UK solar energy viable in the long term.

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The winter months have brought lots of snowfalls, or as they are known in the world of solar energy, ‘shading events.’ You might be forgiven for wondering what exactly happens to the performance of solar panels when they are covered in snow, or anything else for that matter.

Shading is a big issue for solar arrays. A small amount of shading on one solar panel can result in a big power loss for the entire system. This is because of how they are connected together; a solar panel is made of a number of solar cells connected in series. Each solar cell has a current of around 8 Amps and a small voltage of 0.6V or so when under full sunlight. For those who remember their physics classes from school, this means that when they are connected in series the voltages add up but the current stays equal. Solar panels are then connected together in series to make a string, so the current still stays the same (on large arrays multiple strings are connected in parallel).

What this means is that if one solar panel, or even one cell of one solar panel is affected, it will affect all the others. When a cell is shaded its output current decreases, which means the current for all the other cells and modules is also limited. So one small patch of shade can disproportionately reduce the power output of the whole system.
This effect can be limited by a number of means.

The best way is to make sure your solar panels are not going to be shaded in the first place. This should be checked as part of the site survey, conducted by your MCS accredited installer. You should ensure that nothing will shade the modules during the middle of the day, when your system should be producing the most energy. Shading can be checked using a special design tools that show the path of the sun behind various shading objects. This can be either a lens that shows the horizon and path of the sun in front of you, or a full design software package that uses photographs of the surroundings.

With snow it does help to clear it off. But there isn’t usually much sun when its snowing, and if the sun does come out, the snow melts pretty quickly.

If you cannot eliminate shading as is often the case in built up areas, there are several technologies that can limit the effect of it. Many solar panels now include bypass diodes that disconnect groups of solar cells if they are shaded. It is fairly crude but often works well. When you buy solar panels make sure to ask about bypass diodes.

A second technology that is not available yet in Europe but soon will be is distributed conversion. Here, rather than have power electronics (like the inverter) positioned all in one place, you have some electronics placed on each module. This allows each module to operate independently. One company in the US called Enphase claims this technology increases power output by upto 25 percent.

These are all things to bear in mind when buying a photovoltaic system.