Posts tagged with: solar products

A big issue for solar and wind energy is that the power they deliver is not constant. Unlike coal or nuclear power stations which produce a steady stream of power whatever the weather, wind and solar suffer from extreme fluctuations. For wind energy, a drop in wind speed can mean a 90% power loss over a large area in just a few seconds.

For solar energy, there are many different types of fluctuations. In the UK for instance, winter months produce only a quarter of the amount of energy as summer months. Obviously solar energy production takes place only between dawn and dusk, and even during the day, clouds can cause major fluctuations in solar energy output. These fluctuations make it hard for electricity grid operators to really use renewable energy since they need to guarantee power is delivered 100% of the time.

At the moment, because renewable energy makes up such a small component of our electricity generation in the UK these fluctuations are irrelevant. However as the proportion of renewables connected to the grid increases these effects will eventually become more significant. In southern Germany, where solar energy makes up over 4% of the electricity generated and at times represents 30% of the electricity on the grid, energy companies are starting to think carefully about how to use this resource most effectively.

Several can be done to decrease the impact from these fluctuations in renewable energy:

The first thing is to have a strong and efficient electricity grid. This is the case in Germany where energy can be efficiently and almost instantaneously moved from one part of the grid to another. This means that when there is a surplus of energy in one part of the country, energy can be transported at very short notice to where there is an energy deficit. Interestingly, as the amount of solar energy in a country increases, short term fluctuations caused by clouds are “ironed out” as shaded solar panels in one region are compensated for by unshaded solar panels in another.

In addition, as some of you may have heard, there is something called a ‘smart grid’ in development. This term is used to refer to lots of different things but on its most basic level it implies that energy demand can be controlled in some way. This could be very helpful for renewable energy since energy demand can be matched to when there is an abundance of solar energy in the middle of the day.

Another tool that can be used is prediction mechanisms. Using weather forecasting and remote monitoring, the amount of solar energy expected can be predicted. Providing this information to energy companies allows them to use various forms of reserve energy such as gas turbines or hydroelectricity which can be turned on and off in a matter of minutes.

The ultimate solution though, is to find a cheap means of storing energy. This would make all the fluctuations from renewable energy irrelevant. Researchers around the world are busy working on a wide range of different energy storage technologies. One of the most familiar ways of storing energy is to use a battery. Regular alkaline batteries are far too expensive and not durable enough to be used on a large scale, but there is huge number of new types of battery being worked on that could soon bring the cost down dramatically.

Besides batteries, there is a wide range of other technologies in development that could all be used to store renewable energy. Examples of these include; compressed-air energy storage, pumped hydro-electricity, molten-salt, fly-wheels and hydrogen, to name a few. Of course each technology has advantages and disadvantages, but it remains that we have a number of potential solutions for storing renewable energy. So the fact that the sun doesn’t always shine is certainly not a reason not to support solar energy.

The much debated, tweeted, blogged and indeed refreshing government legislation, the feed-in tariff, which is to become reality on April 1 could transform micro-generation from cottage industry to nationwide norm within the next few years according to Steven Harris. Harris, as head of low carbon technologies at the Energy Savings Trust (EST) believes that with the tariff legislation in place, the UK will be in good shape to see a large scale uptake of renewable technologies, something which he believes only a few years ago would have been incomprehensible.

“The poor old cottage industry of renewable energy will not know what’s hit it. People could be forgiven for waiting to install these technologies up until this point, but once the tariff comes in, things could change rapidly,” states Harris who certainly knows how difficult it has been to bring about a change in attitudes towards the viabilty and importance of green technologies.

Harris who along with his colleague Bill Dunstar created the BedZed village project featuring carbon neutral housing in the Surrey commuter town of Wallington ten years ago can easily recall the derision which green ideas were met with at the time. The project which was shortlisted for the Stirling Prize in 2003 highlighted the potential feasibility of sustainable materials and carbon neutral building at a time when such ideas were far from the mainstream. Harris recalls,

“It’s amazing when you sit in meetings now; people are saying exactly the same stuff that was laughed at when we were starting BedZed. Back then, things such as using reclaimed materials, sustainability assessments, local sourcing, having an ecological footprint… they were just not on the construction agenda, let alone the housing agenda.”

With the introduction of the feed-in tariff at the beginning of next month the situation has changed dramatically for micro-generation projects such as BedZed pioneered by Harris and Dunstar. The tariff will offer small-scale generators of green energy guaranteed, premium rates for energy fed-back in to the national grid and will thereby seek to offset the obvious costs involved in installing renewable technologies. With annual returns of £500 expected for households with solar PV installed, the industry is hopeful that the solar industry has the potential to take off with the backing of the tariff.

Steven Harris certainly believes that solar micro-generation could become widespread with the tariff mechanism incentivising investment and see the BedZed project become reality within the next decade.

“Solar technology has really moved forward. In China, it’s illegal not to put thermal solar on your roof, but they have the advantage of a totalitarian state. The fact that they have to manufacture panels for billions of people has really driven down the cost of solar. I know when we first started BedZed, the payback on a panel was around 75 years; now it’s about 12.”

Unfortunately it is necessary for me to respond to a recent article by George Monbiot in the Guardian criticising the UK feed in tariff. Since the article misses key points that would have influenced the conclusions made, I take this opportunity address the author’s primary arguments.

The purpose of a feed-in-tariff is to encourage investment and grow the micro-generation industry. Economies of scale and technology improvements then lead to cost-reductions, meaning that the subsidies can be reduced and eventually removed. This is exactly what is happening in Germany and many other European countries. In Germany, whilst there is some debate over how much the feed-in-tariff should be reduced, the solar industry agrees that it should be decreased faster than was originally planned due to the recent dramatic falls in PV system prices. The tariff reductions are a testament to the policy’s success, not its failure, and no-one believes it should not have been introduced in the first place.

Monbiot failed to mention that Germany’s solar industry currently employs over 60,000 people, turns over €10bn a year and generates significant tax revenues. The industry is expected to grow even with significant feed in tariff reductions and southern Germany currently produces close to 5% of its total electricity demand (the amount of solar energy in Germany has grown by almost a factor of 10 since 2006). The cost of the feed in tariff to energy consumers is just a few Euros per year per household.

Many other countries have followed Germany’s success in recent years such that the UK is the last remaining major European economy without a feed-in-tariff. Consequently, the cost of PV in the UK is still extremely high in comparison with our neighbours. Experience from Europe has shown that the downward cost trajectory for PV is very steep once the industry begins to grow, and cost competitiveness with conventional energy prices is predicted to be achieved across much of Europe in the next two years. This is why the UK needs to be aggressive with its feed-in-tariff – so it can catch up and reduce the subsidy sooner.

Monbiot astonishingly unqualifies his comparison of large-scale energy generation with micro-generation. The consumer price of electricity costs upto four times as much as the wholesale price of electricity. Therefore micro-generation, which is produced at the point of consumption, has a much easier cost target than large-scale generation to be economically competitive. Micro-generation is much closer to being economically viable than Monbiot makes to believe.

Furthermore, no-one is saying that micro-generation should replace large-scale wind, it is a valuable addition. Nor is anyone saying we should prioritise micro-generation over energy efficiency measures such as insulation. Obviously its cheaper to save CO2 by improve improving inefficiencies than to install clean energy generation, but if we are to eliminate the majority of our carbon emissions, both efficiency and clean generation are required. Insulation will be fitted wherever possible in UK buildings, why wait until this process has finished before dealing with renewables?

Monbiot also argues that PV only makes sense in southern California. The average insolation (sunniness level) is around 1.9 times higher in Southern California than in the UK. This means that yes, you have more sun in California than here, but not by an order of magnitude. The amount of sunlight that hits buildings in the UK is still 6 times the amount of energy used within those buildings and Germany’s irradiation level is very similar to ours.

I imagine that Monbiot was joking about the possibility of people fraudulently claiming the feed-in-tariff but it is worth noting that such a fraud would not be possible given the checks that are in place and since it has not been seen in any other country with a feed in tariff, why should it be seen in the UK?

In summary, Monbiot does not seem to understand what has been happening in Europe during the last few years. The feed-in-tariff has been shown to be one of the few successful mechanisms for boosting renewable energy generation and fighting climate change. I hope that his misunderstanding does not serve to hold the UK back any further than we already are.

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.