Posts tagged with: solar panel

Solar panels are by far the most expensive item in a solar panel installation. Understanding the features that differentiate a good solar panel from a bad one is not so straightforward. In several instalments I’d like to give a guide to each of the key criteria to look out for. I will try keep it as simple as possible but it is something that many people ask me about so I think it isn’t a bad idea to discuss these issues in some depth.

First of all I’d like to discuss solar panel efficiency. This defines how effective a solar panel is in converting sunlight into electricity for a given surface area. The advantage of having a higher efficiency solar panel is that you can get more power out of a small available area. For this reason, high efficiency solar panels are normally priced at a premium and targeted at the domestic market where space is most constrained. High efficiency does not necessarily mean better quality or reliability however – these issues are covered later. Nor does higher efficiency mean better value; in many cases lower efficiency panels are used because they are more cost-effective in places where space utilisation is not so critical.

First of all, how do you find out the efficiency of a solar panel? It’s easy to find out this out for yourself. Remember that the power of a solar panel is given by the power you get out under ‘standard test conditions.’ This means the output is measure when the panel is exposed to a very bright light with an intensity of 1000 Watts per square meter (1000W/m2) at a temperature of 25oC. This is normally expressed in Watts (e.g. 185W or 230W etc) and is the power you will get when the sun is very strong. You can then multiply the module length and width (which is shown on the datasheet) to get the module area. By taking the module power in Watts and the standard test conditions of 1000W/m2 you can determine the module efficiency as follows;

Efficiency = power out / power in = module power / (width x length x 1000W/m2)

When evaluating solar panel efficiency its important to be aware that each solar cell has an efficiency higher than that of the whole solar panel (or module) due to empty space. Therefore make sure to find out which value you are looking at.

In general solar panels you will come across in the UK will be made of silicon (I have discussed thin film panels previously) so the discussion here will focus on these. The highest efficiency silicon solar panels on the market today are between 17% and 18% efficient. The efficiency of silicon solar panels is increasing due to R&D, but improvements are incremental and slow because there are a number of fundamental limitations to the efficiency of silicon solar cells which mean that any drastic improvements in the near future are unlikely. Perhaps I will describe those limitations in another article.

The main factor you will come across that affects module efficiency is whether the module is mono or multi-crystalline. In English this means that the solar cells can easy be made from mono or multi-crystalline silicon. Mono crystalline solar cells consist of a slice of a single, very pure silicon crystal and hence are very efficient due to few defects. Multi-crystalline solar cells, which comprise multiple crystals, are around 1-2% less efficient but are generally more cost-effective to produce. Personally I think it generally makes sense to use mono-crystalline cells for domestic installations where space is at a premium and multi-crystalline cells for larger installations.

Another factor that can affect efficiency is anti-reflective coatings. These are becoming more and more common. Nearly all solar cells have texturing directly on top of them that reduces reflection and now many solar panels come with anti-reflective glass. This generally consists of a textured glass that can be seen as a speckled pattern if you look closely. The improvement of anti-reflective coatings is hard to determine, although some manufacturers claim energy yield enhancements of over 5 percent.

When installing a solar panel system your ultimate goal should always be to get the best return on your investment, which means getting the most power for the lowest price without risking reliability and is dependent on many factors besides efficiency. Whilst there are a number of other technologies on the horizon that can be used to improve efficiency by small amounts, nothing will create a drastic change overnight. Prices of solar panels will continue to fall rapidly as production volume increases (in the same way as many other technology products such as computer memory) but these price falls will be matched by reductions in the feed-in tariff. Therefore don’t worry that installing today’s technology risks being superseded by a miracle solar panel tomorrow. Working in the industry gives you pretty good insight as to what is coming down the line.

The sun shone upon the festival goers at Glastonbury last week with usual scenes of rain and mud put on hold as thousands flocked to that corner of Somerset. With sunburn and dehydration an obvious risk for the crowds, the UV rays would have proved a welcome sight for Michael Eavis who plans to build the biggest solar farm in the UK. Eavis, the founder of Glastonbury festival hopes to take advantage of the recently introduced feed-in tariff to earn money for the energy he generates on the site.

The plan will consist of 1500sqm of panels at a cost of £550,000 on Pilton Farm and will be situated on the cow shed dubbed ‘Mootel’. With an obvious substantial outlay involved in the construction of the 1100 panels, Eavis will utilize the feed-in tariff to generate an income based on the units of energy his solar farm produces.

The feed-in tariff works by offering a guaranteed, premium rate for the units of renewable energy produced by the solar panels be they fed-back into the national grid or simply consumed by the owner of the farm. Eavis’ system for example expects to generate around 200 kilowatts of electricity a year generating £45,000 in income from the tariff, enough to pay for the installation in six years. With a 25 year lifetime of the project, Eavis can hope to generate a healthy profit once the high cost of the installation is recovered.

Although Michael Eavis is investing £50,000 of his own money into the solar farm, the rest is being invested by Triodos Bank who specialize in green investments. Eavis, explaining why he chose to invest his money in solar power stated,

“I’ve been planning this for a long time but the Gulf of Mexico oil spill has brought home just how urgent it is that we move to renewable electricity. We have already bought all the recycled fat from chip shops that we can find to run the generators during the festival and we wanted to create a permanent source of renewable energy. It makes sense to use some of the massive amount of free energy that comes from the sun.”

Energy company E.ON has announced that they will me making full use of the Clean Energy Cash Back scheme in bringing in a solar offering to its customers. The Cash Back scheme which came into effect on April 1 is essentially a feed-in tariff system offering small scale renewable generators cash for money used on site and better rates for money fed-in to the national grid.

E.ON plan to utilize the newly introduced legislation in order to offer their customers what they term the ‘SolarSaver’ scheme, a consultation, survey and installation service for solar photovoltaic products.

E.ON hope that their SolarSaver scheme will act as a sound investment product over 25 for its customers with expectations that it would take just 12 years to break even with 13 subsequent years of profit on the project.

According to the energy company, they claim that this projection is based on the fact that a 2.1kW solar kit costs around £11,350 and would be capable of generating around 1.5kWh p/a. Homeowners would expect to save in excess of £24,000 over the project’s lifespan with the added bonus of helping to offset their carbon footprint on fossil fuel energy savings.

A turnkey product is expected with E.ON stating that their solution will offer homeowners advice on the suitability of their home for solar paneling, consultancy for application of planning applications and advice for customers about entitlement to grants and other government schemes.

Phil Gilbert, spokesman for the SolarSaver scheme announced,

“We’ve all got a role to play in bringing down our carbon footprint and we’re helping our customers do that. With the long term benefit provided by the new Feed-in Tariff they’ll even make money back.

Adding, “This will be the first of many exciting new propositions we’ll have for our customers, giving them the power to produce their own heat and electricity from lower carbon sources.”

For full information about similar investment schemes offered through please visit:

If you’ve ever carried a solar panel you’ll know that they’re pretty heavy (about 25kg for a 1.5sqm panel), and if you add on the racking that’s required it makes things even heavier. This is a bit of a problem for roofs that can’t support large weights, and for the installers who have to get the stuff up there.

As with many things in life however, technology has a solution on the way. In this case the solution comes in the form of flexible solar panels. This new type of solar panel doesn’t use glass as the supporting material; it uses transparent, flexible plastic sheets. They can be rolled up like carpets and unfurled across a low-sloping roof. This process is much quicker and easier than normal solar panel installation. The solar panels just need to be tacked down at the edges, rather than have heavy metal racking bolted into the frame of the roof. The material is also light enough so that any roof can support its weight.

This technology is spreading quickly but has yet to win dominance in the market. This is for several reasons. Firstly – only one company in the world is making flexible solar panels in large volumes. That company is UniSolar, based in Michigan, USA. UniSolar have developed their own proprietary process for depositing thin-film solar cells (see discussion “REF TO previous article”) on flexible plastic sheets.

In order to increase efficiency of the panels, their design in fact uses three solar cells stacked one on top of the other. Each solar cell responds to a different part of the sun’s spectrum so it maximizes the amount of energy converted to electricity. Despite this compmexity, these solar panels are significantly less efficient than traditional, crystalline silicon solar panels. They are made from ‘amorphous’ silicon and are currently around 6-8 percent efficient, compared to 16 percent for crystalline silicon panels. This means you have to cover a larger area of the roof.

A number of companies claim to have more efficient versions of the technology on the way. Companies such as US based Advent Solar, claim to have flexible solar panels that will soon reach over 10 percent efficiency while other companies, such as G24 Innovations in Wales claim to have lower manufacturing costs for this technology.

Given the success of UniSolar with their low efficiency and complex design, any company that can make an improvement is likely to have success with flexible solar panels. Let’s wait and see…