With the UK government’s announcement of the introduction of the Clean Energy Cash Back system, essentially a feed-in tariff designed to attract investment in the British renewable industry, controversy has raged with solar industry insiders believing tariff rates to be too low.

It therefore comes as no surprise that the Federation of Master Builders (FMB) has also announced that they believe the tariff rate which has been set (5p/unit with a subsidy of 36.5p for units of energy generated by small scale solar and wind installations) will be too low to make the UK market competitive and have suggested a rate increase of 10p.

Speaking under the banner of the widely publicised ‘We support solar’ campaign the FMB’s announcement comes in the light of a number of criticisms aimed recently at the Department of Energy and Climate Change (DECC) legislation to be introduced in the April of next year. The FMB is being given the full backing of the National Federation of Roofing Contractors (NFRC), and Electrical Contractors’ Association (ECA) with around 16,000 building firms adding their weight to the ‘We support solar’ demands.

Feed-in tariffs are designed to offer premium, guaranteed rates to small scale producers for renewable energy which is fed in to the national grid and bought by the utility companies. In markets where they have been introduced elsewhere they have proved successful at attracting investment in new solar markets. In Germany and Spain, solar sectors have experienced booms thanks to the attractiveness of solar stocks in those countries with high returns on investment made possible by the feed-in tariff mechanism.

It is certainly considered that while the UK does not enjoy Iberian sunshine levels a strong tariff would enable the sector in the UK to take off and of course attempt to catch up with other mature markets. Some critics have argued that a strong anti-solar lobby in Westminster led by the utility companies has influenced the government’s decision to go forward with legislation which is generally accepted to be insufficient. With this in mind Liberal Democrat MP Simon Hughes stated,

“The proposed “cash back” payments are designed to dampen solar PV demand over the next three years rather than to encourage it. This mindset needs to change. Solar power can play a significant role in the “greening” of our towns and cities, while providing tens of thousands of new construction sector jobs.”

Indeed, with support among certain power brokers and pro-solar lobbies acting to add 10p to the current tariff it may well be possible to tweak the legislation, making it workable in the long term. If not, the ‘We support solar’ campaign may fail to see the fledgling UK PV sector take off.

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.

The head of the newly formed New and Renewable Energy Centre (Narec), Tim Bruton, has made the claim that if every south facing home in the United Kingdom fitted solar panels, they would generate enough electricity to meet the country’s energy needs.

Speaking ahead of Solar Flair 2009, a conference to be held in Northumberland designed to highlight key issues regarding the take up of photovoltaic (PV) energy, Bruton gave his full backing to solar energy as a way of combating climate change.

With the north-east trying to put itself forward as a future leading light in solar PV expertise, Bruton is one of many academics from the region hoping to put the north of England on the PV map. As a fellow of the Institute of Physics and a reputation for insightful publications of articles relevant to the field of solar PV, Bruton asserted that the UK is on the ‘verge of something exciting’, commenting,

“The University of Northumbria carried out a study for the Department of Trade and Industry looking at the existing south-facing buildings in the UK”, adding,

“All we have to do is take the things we have already built and put solar panels on them and we can generate all the electricity we need.”

The claims made by Bruton have been made all the more possible with the announcement by the government that 2010 will see the introduction of the Clean Energy Cash Back Scheme, essentially a solar feed-in tariff (FIT) designed to attract investment in the new industry. The scheme would work by offering small scale solar energy producers guaranteed, premium rates for energy fed back in to the national grid.

The mechanism is designed as a way of off-setting the obvious initial costs of solar panel installation and where such FITs have been introduced elsewhere, they have proved to be very effective ways of nurturing fledgling renewable sectors offering returns on investments to investors which would otherwise have been impossible. Regarding a UK solar FIT, Bruton stated.

“If you look at what has happened in Germany, Spain and California where you have the right subsidy structure from the government, the market has taken off.”

Certainly, all involved in the UK solar industry will be hopeful that the government’s controversial tariff will be sufficient to see the fulfillment of Bruton’s prophecy in the coming years.

Jeremy Leggett, head of Solar Century has predicted that solar energy will reach grid parity with energy produced by non-renewable means by 2013, seven years ahead of previous predictions. Speaking at yesterday’s ‘We Support Solar’ event, Leggett announced that with recent support given to the solar industry in the UK through legislation the price paid for solar generated electricity will reach a parity with coal produced electricity.

The concept of Grid Parity has always been the ‘holy grail’ within the solar industry with solar supporters extolling the need for government action in order to ensure that the photovoltaic (PV) industry evolves into a viable competitor to fossil fuel producers. Detractors of the notion of a possible grid parity have traditionally asserted that solar will never compete with fossil fuel energy on price because of the costs associated with installing and maintaining PV plant.

However, the recently passed feed-in tariff legislation which offers solar energy producers a premium rate for energy they feed back in to the national grid will prove to be extremely effective in attracting investment in the solar industry. Speaking about the solar naysayers among the energy industry Jeremy Leggett commented,

“The chief executive of British Petroleum said that solar will never be economically viable without technological breakthroughs. He is going down the road saying that, we say it will be on cost parity with electricity by 2013. We are going to find out who is right.”

Certainly with recent reports from America that two-thirds of the United States will achieve grid parity by 2015, the future seems to be mapping out truly in favour of solar energy on both sides of the Atlantic, a situation which won’t go unnoticed by investors looking for long term investment yields.

Also at the event, Joan Ruddock, acting as spokesperson for the Department of Energy and Climate Change (DECC) announced that the government would strive to reach its carbon reduction targets through a specific focus on “small-scale renewable technologies, such as solar PV”, going on to add,

“We know that it is not just a case of generating ideas and many of you have pushed for greater incentives, so we are introducing what is going to be called a clean energy cash back, that is much easier for ordinary people to understand than a feed-in tariff for people in these difficult economic times and it will be important to encourage people at this time.”