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The Chinese National Energy Administration has announced via the state run newspaper China Daily that they will be seeking to produce around 15 per cent of all the country’s energy by renewable means within the next 10 years.

China, despite being criticised for its heavily industrialised, polluting economy and images of Beijing obscured by dense smog during the 2008 Olympic Games, the government is taking proactive steps towards reducing carbon emissions with measures that would shame certain other attendees of the Copenhagen climate summit.

With the growing realisation of the fallibility on basing the huge Chinese economy on fossil fuel imports which could become untenable within the next 25 years, the Beijing government is planning to spend billions of dollars in investing in solar and wind farm sites in addition to research projects which could keep China at the cutting edge of green energy generation.

Renewable energy generation grew by 1 per cent in China in the last 12 months with the government hopeful that figures will grow from the present 9.9 per cent to 15 per cent by 2020. The Chinese government is keen to diversify its economy as well as its means of energy generation with the dual purpose of slowing the effects of climate change and making the economy more robust in the face of any potential fuel crises which could arise in the near future.

In spite of passing legislation designed to have an immediate impact on renewable energy uptake such as the feed-in tariff, a mechanism to incentivise investment in green technologies, government spokesman Zhang Guobao is realistic about the timescales involved in such projects. Speaking to China Daily, Zhang commented that,

“Power projects take a long time to be up and running, and we are basically allowing five years to complete them although it is a 10-year program, otherwise, the facilities cannot be put into use by 2020.”

Zhang added, “It appears that some local governments approved energy-guzzling projects during economic crisis so only by fully implementing our energy saving regulations can we realize economic growth with less energy consumption.”

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.

When thinking about renewable electricity for your home, two options spring to mind; photovoltaic panels and small wind turbines. But which one should you choose? The government has introduced a feed-in-tariff that pays a subsidized amount for the electricity they produce and the amount paid for small wind turbines is similar to that paid for small PV systems (34p/kWh compared to 41p/kWh).

The key criteria to deciding which technology will be the most profitable is the cost of producing a unit of energy from each one. For this you need to factor in the up front costs such as equipment and installation, and then look at how much energy they will produce once out there over an average year. Without going too heavily into numbers my argument is that in some instances, micro-wind turbines will have a lower cost of energy than solar panels, but for the majority of cases solar panels will be better and this can be explained by some basic science.

Without a doubt, on a large scale, wind energy is cheaper than solar. The cost of energy from large-scale wind farms is somewhere around 10p/kWh whereas the cost of energy from large-scale solar is three to four times greater at present. Big wind turbines are now very well designed products and many years of industry development means that the costs have fallen dramatically and continue to do so. Big solar farms are also rapidly reducing in cost and make a lot of sense in some locations, particularly in the many regions where wind farms are not suitable, but for now they do not compete.

On the small scale however, the economics are drastically different. As the size of a solar installation decreases, the performance falls linearly with the amount of area used, and therefore the cost of energy does not change so dramatically. In contrast, as wind turbines get smaller their performance gets disproportionately worse. This is for two mains reasons:

The first reason is that as the turbine blade length gets shorter, the ‘swept-area’ decreases quadratically. This means that if you decrease the length of a blade from 80 meters to 40 meters, the area covered by the blade decreases from 20 thousand square meters to just 5 thousand. The ‘swept-area’ determines how much wind energy the turbine can use. So when you decrease the blade length you still need all the expensive moving parts like the generator, but you get disproportionally less energy – for one big wind turbine you would need thousands of smaller ones to cover the same area. The second reason is that where you use micro-wind turbines the wind speed is generally slower. This is because most of us live in built up areas where there are other buildings nearby. These buildings disrupt the wind, making it irregular and slow. Wind speed is crucial to the effectiveness of a wind turbine, again because the energy contained in the wind is disproportional to its speed. If the wind speed drops by a factor of 2, the energy produced by a wind turbine decreases by a factor of 4. Comparing most built up areas, the average wind speed is much lower than half the wind speed found high-up in open spaces where you find most wind farms.

These two factors combine to mean that for most homeowners solar panels are the most sensible and safest option. Of course, if you live near an open space and get a lot of wind then a micro-wind turbine could be a great investment. However, if you do live near a windy open space, I would suggest trying to build as big a wind turbine as possible, as their cost effectiveness increases dramatically with size.

In a bid to prevent a shortfall in rate payments for pioneers in small scale renewable energy investment, Good Energy has promised to continue to pay its generators 15p /kWh rather than the 9p / kWh set out in the recently announced tariff legislation.

Good Energy, dealing solely in renewable energy has announced that the government’s recent tariff scheme would harm their so-called ‘pioneer’ generators who installed their renewable technology before the cut-off date of July 15, 2009. Under the new tariff regime to come into effect in the Spring of this year, these pre -July 15 customers would only be eligible for a 9p/kWh payment for units of renewable energy compared to a payment of 41.3p/ kWh for installations after this date.

In a bid to keep pioneer installors viable until when they hope the government will amend their pre July 15, 2009 rule, Good Energy will continue to pay these generators the previous 15p/kWh rate. Currently, Good Energy sees itself as a market leader in renewable energy uptake incentivisation and wants to continue awarding attractive incentives for smale scale installors of renewable energy technology. Leading the way in 2004 with their renewable energy incentive scheme HomeGen, Good Energy believe that the government’s scheme is treating long term micro-generators unfairly.

CEO of Good Energy, Juliet Davenport, announced:

“It’s outrageous that the new FiT only pays the highest reward to new generators – Good Energy believes that the early adopters of microgeneration technology should also be recognised for their pioneering attitude and taking a lead.

That’s why we’ve decided to continue paying our existing accredited HomeGen generators 15p a unit for all the electricity they generate and lobby to change the government’s mind.

It’s outrageous that the new FiT only pays the highest reward to new generators – Good Energy believes that the early adopters of microgeneration technology should also be recognised for their pioneering attitude and taking a lead. That’s why we’ve decided to continue paying our existing accredited HomeGen generators 15p a unit for all the electricity they generate and lobby to change the government’s mind.”

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We are looking for articles of around 400-500 words, and these can be published anonymously or not, depending on your preference. We cannot promise to publish all articles but will do our best. You can also let us know beforehand if you would like to write something and we will provide some early feedback.

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Solar panels fall into two main technological categories. The incubant, established tyoe are called crystalline silicon solar panels and the exciting but unproven type are known as ‘thin-film’ solar panels. To understand the advantages and disadvantage of each technology I’ll briefly explain how each type of solar panel is made. Crystalline silicon solar panels are made from 50 or so ‘solar cells’ connected together and encased in glass. Each solar cell is in fact a thin slice of large crystal of pure silicon (called an ingot). These large crystals are grown from a seed crystal surrounded by molten silicon at very high temperatures. The silicon used must first be extracted from silicon dioxide (also known as sand) and then purified to a very high level. Once the crystal is formed it can be sliced into wafers. The wafers are then specially treated to make a junction between a positive and negative type semiconductor, and then other layers such as the conductive contacts are added to make a working solar cell. This process has many steps and consumes a lot of energy. However, many companies have spent a lot of time refining the process to make it as efficient as possible so almost all parts of the process are now automated.

Thin film solar panels are made using a radically different process. The underlying physics is similar in that they still use a junction between a positive and negative doped semiconductor, however thin film solar panels have the potential to be made in much fewer steps than crystalline silicon. The idea is to take glass (or sometimes foil or plastic) and coat it directly with a series of layers, including the active semiconductor layers to produce a working solar cell. The glass is then encapsulated with a protective plastic and a second sheet of glass as protection. This process saves having to make lots of small cells and connect them together. The other advantage is that the layers are very thin, hence thin film solar cells. The active layers of the cell are only a few nanometers (billionths of a meter) compared to 0.2mm for each silicon wafer.

The important point of all this is that the manufacturing cost of thin film solar cells has the potential to be significantly lower than crystalline silicon. Unfortunately, there are some catches. Firstly, they are not as efficient as crystalline silicon. Crystalline silicon reaches 16 – 18% efficiency in modern solar panels, whereas the most efficient thin film solar panels on the market today  are under 11%. The next drawback is reliability. Thin film solar panels have had less time to prove themselves and have been known to suffer from degradation meaning that their performance gets significantly worse over time.

Despite these drawbacks, several companies have managed to become very successful in manufacturing thin film solar cells. The most notable is called First Solar who are now one of the top two largest solar panels manufacturers in the world and have a significant advantage over rivals due to their low manufacturing costs. First solar make thin film solar cells made from cadmium telluride, one of a number of semiconductor materials that can be used for thin films. First Solar’s panels are less efficient but are very popular for large scale solar installations because of their low cost.

Before the financial crisis, when silicon was in short supply and very expensive, all thin film solar panels were a good idea. First Solar could not produce enough and billions were invested in a large number of thin film solar companies aiming to follow in their footsteps. Now that the silicon shortage is over and the price of crystalline silicon solar panels has fallen, the environment for thin film solar cells is more challenging. First Solar will remain a strong player as they have managed to get to high volume and have a reliable production process. Many of the 200+ start-ups hoping to replicate their success will struggle however. For thin film solar cells there are a wide range of different manufacturing processes and materials that can be used, and there is still a lot of research being done to improve our understanding of the underlying physics. This means that there is a lot of opportunity to invent a ‘unique’ technology and start a company but only the best thin film solar companies will make it however. They have to show not only that their technology is efficient and reliable, but also demonstrate that large scale production is feasible and low-cost. Many ideas that look good on paper or in the lab turn out to be impractical when it comes to volume manufacturing.

At present, it seems like crystalline silicon will retain a strong market share for the foreseeable future (it current represents 80-90% of the market) but I believe that eventually certain thin film technologies will begin to displace crystalline silicon. There is a lot of potential for efficiency improvement in thin film, as well as lower manufacturing cost. Some technologies, particularly that usce solution processing are really very exciting.

What does this mean for the UK solar industry? Very little actually. I would expect over 90% of the UK market will be crystalline silicon for a long time. The reason is that the UK market will be dominated by smaller rooftop applications (partly due to the structure of the feed.in tariff as discussed last week). In such space-constrained applications you want to use the most efficient technology to maximize the energy generated from the available area. For now, this means always choosing crystalline silicon as it’s efficiency is significantly above any thin film solar panel out there.

Keep an eye out for breakthroughs in solar technology as some are surely bound to occur, but beating high quality crystalline silicon solar panels made in China for cost, efficiency and reliability is not easy.

As a follow up to the recent article on inverters, I thought it would be a good idea to warn you that if you wanted to buy an inverter in time for Christmas I’m afraid you’re out of luck. As result of the huge demand for residential PV systems Germany described on this site below, it is virtually impossible to find an inverter of any size or manufacturer in the whole of Europe at the moment.

The big manufacturers; SMA, Fronius, Mastervolt and the like are all completely sold out and are unclear when their next shipments can be made. Wholesellers are operating on a first come first serve basis and taking orders three months in advance. This means that if you were thinking of installing a PV system in the next few months but haven’t ordered your equipment yet you’d better get a move on. We’ve even heard reports of SMA shipping inverters to German customers without LCD displays in efforts to meet demand. (apparently the displays will be delivered in a few months time when they can be clipped on).

I guess the shortage is a good sign that the solar industry is alive and kicking. However if the feed-in-tariff is announced in the UK soon and it turns out to be a good one, there’s going to be a lot of frustrated people out there unable get involved for the lack of an inverter.

The role of the inverter is often overlooked in a photovoltaic system. Kept inside in the attic or in a closet, it is not the most visible part of a system but it performs a critical role and makes up large component of the equipment costs. The inverter is the hub that converts the direct current produced by the solar panels into alternating current suitable for the UK grid.

In a typical residential photovoltaic system, solar panels are connected in a ‘string,’ which means they are connected together in series so that the voltage of each module adds up. The positive and negative ends of the string are connected to the inverter which then does two main things:

Firstly, the inverter applies the optimum voltage across all the solar panels in the string. In order to extract the maximum energy from a solar panel you need to apply to certain voltage across it. The easy way to understand this is by remembering that power equals current times voltage. Current will still flow out of the solar panel if there is no voltage across it, but it won’t be able to provide energy. If too much voltage is applied to the solar panel then you lose current coming out of the solar panel, so the optimum voltage is somewhere in between. It is the inverter’s job to keep the solar panels at this optimum voltage. This is quite tricky since the optimum voltage changes with the temperature of the solar panels. To cope with this there is a special algorithm built into the inverter called ‘maximum power point tracking’, which makes continual adjustments to the voltage to ensure the most energy is got out of the system.

The second important job of the inverter is to convert the direct current produced by the solar panels into alternating current suitable for the mains electricity grid. In the UK, the mains frequency is 50Hz so the inverter must make sure that the electricity it supplies is matched to this frequency so that it can be used by other appliances in your house or be sold to your energy supplier.

Inverters are very common, for example your laptop charger uses an inverter to convert mains 50Hz electricity into direct current for your computer (this partly explains why laptop chargers are so expensive though I still think it’s a rip-off), and there are some very good solar inverters already out there. The largest manufacturer of solar inverters is called SMA, which enjoys a +30% market share worldwide (their line of residential solar inverters is called the ‘SunnyBoy’). Other big manufacturers are Kaco, Xantrex, Danfoss and Mastervolt to name a few. These inverters work well, so what are the developments on the horizon that make inverters interesting?

One issue is efficiency. Most commercial inverters are around 97% efficient, which is pretty good, but it still means that you lose 3% of all the energy you produce converting it from DC to AC. Increasing efficiency to 99% would increase the return on investment of your solar system and give a real competitive advantage. Several manufacturers claim to be close to offering new, super-high efficiency products.
The next issue is reliability. Most inverters are guaranteed for 10 years, which although is not bad, its only half the guaranteed lifetime of solar panels. This means consumers must allow for replacing the inverter at least once when financing a solar project. If inverters could be guaranteed for 20 years, it would mean consumers could feel comfortable knowing that the system will operate under guarantee for its entire lifetime until the whole thing needs replacing. Inverter manufacturers have been striving to improve reliability of their systems and products guaranteed for 20 years should be on the market soon. As a side point; proving 20 year reliability is very hard to do without actually waiting 20 years, and there is an entire field of study devoted to ‘accelerated stress testing’ of these products.

Another set of new features is how information is displayed. Many inverters come with an optional WebBox that allows you to view the performance of your solar system online. Some inverters now even come with iPhone apps so you can watch your solar energy production on-the-go, importantly show your friends in the pub. These types of innovations will keep coming so keep an eye out if this is something that interests you.

Perhaps the most radical development for inverters is the ‘micro-inverter’. Basically this means having not one big inverter but lots of smaller ones attached to each solar panel. This has several advantages. Firstly, it can improve the performance of the system significantly. Going back to the maximum power point tracking feature mentioned above, a normal inverter has trouble if not all the solar panels are performing the same. Solar panels could be at different temperatures to each other or just have different performance from factory errors. By using micro-inverters you can ensure that each solar panel is being operated at its own optimum voltage. Another issue is to do with shading. If one solar panel in a string is shaded or performing badly, it acts like a big resistor and dramatically reduces the performance of the whole system. Using micro-inverters isolates the performance of each solar panel so that power loss from shading is minimized. Enphase Energy, a leading manufacturer of micro-inverters in California claims that these features can lead to an improvement of up to 25% better energy output.

Other benefits of micro-inverters include the elimination of dangerous high voltage DC cabling on the roof, which can reduce fire and electrocution risks. (Another side point; some micro-inverter products are not actually micro-inverters, but they perform maximum power point tracking at each solar panel and then the AC:DC conversion at a central point.)

Currently, there is not a single micro-inverter product available in the UK. This is because it is still a new technology and the UK is such an insignificant market that it is not of interest to manufacturers rushing to bring their products to commercialization. That being said, the success of companies like Enphase in California, and the spate of companies following in their footsteps, means that it won’t be long before they become a real option, even in the UK.

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…

Good question. There is a huge amount of innovation happening everywhere in renewable energy and although solar technology has evolved rapidly in the last few years there is still a long way to go. There are lots of different aspects of a photovoltaic system that can be improved, and I will cover as many of them as I can on these pages.

First of all though, what is the basis on which we can judge these improvements? What is the ultimate goal here? Everyone can have their own opinion, but my ambition is to see solar energy compete economically with conventional energy sources, and for that to happen requires just one thing, lower cost of energy. Now you can get to lower cost of energy either by reducing the cost of the solar energy system or by increasing the amount of energy you get out of it. As we shall see, people everywhere are coming up with a lot of cool technology to go down both of these routes, but lets start with a company that I like called Nanosolar, who may eventually make the key step that makes solar power cheaper than coal.

First a bit of background: Solar panels are the most expensive part of a Solar electricity system, making up between half to two thirds of all the upfront costs. Most solar panels (sometimes called photovoltaic panels) are made from 50 or so ‘solar cells’ which are thin slices of silicon crystals specially treated so that they can turn sunlight into electricity. Its basically the same process that’s used to make electronic chips, which is fine for making tiny things that go inside your computer, but quite expensive for covering a small fraction of the earth’s surface with. Therefore a phenomenal amount of research has and is being done to find cheaper alternatives. So far the leading candidate for a replacement is the called ‘thin-film’ solar cell. In this case you start with flat panel of material such as glass, and coat the whole thing in a series of super-thin electronic layers that convert the sunlight into electricity. This process is cheaper than making normal silicon panels, however they are not as efficient at producing electricity.

Nanosolar are a frontrunner in developing thin film solar panels and are taking the technology to the next level. Most makers of thin-film solar panels need to use big vacuum chambers to deposit the semiconductor and can only process one panel at a time. Not so Nanosolar; they’ve cleverly developed a special electronic ink that they can literally ‘print’ onto big rolls of flexible metal sheets. Their factory in Silicon Valley looks very similar to a newspaper printing press – it’s much more suited to covering large areas.

When running at full speed the printing press should be able to cover XX football fields a day. Once the electronic layers have been printed on the foil they are cut into 6-inch squares and flown to another, newly opened factory in Germany where they are laid out into modules sandwiched in glass. Nanosolar claim their process is much cheaper than existing manufacturers out there, so cheap that it doesn’t matter that their panels are less efficient than traditional silicon solar panels. If this is really true be good news for consumers in the future, as Nanosolar could significantly bring down the price of solar panels.

Its not all plain-sailing for the US company however. They’ve been working on their process for nearly ten years and so far spent around half a billion dollars and have very little in the way of earnings. They’ll have to sell a lot of solar panels before their investors can start to relax. As with all new technologies, it takes time for customers to overcome reliability concerns, so getting to high sales volumes may take a bit of time.

Whether it’s Nanosolar that succeeds or one of the few dozen other firms pursuing similar strategies is not so important. What is important is that technology makes solar power economically viable without subsidies, and as we shall discuss on this blog, there are a lot of people out there dedicated to making that happen.