Readers letters
In the News section of the November 2011 you presented a view from Labour that cutting the subsidy would put up to 25,000 jobs in UK on the dole. It is a great shame that later on in the magazine you did not cover the costs of PV and why these cuts are sensible when the details are looked into closely.
I would suggest an article to follow should be something like this:
Solar PV panels and how they work for us
A pint of milk in the supermarket costs 38 pence would you pay £5.42 for it? No? Well that is what the Department of Energy and Climate Change set up for us to buy "green" electricity from PV in April 2010 under Ed Miliband instead of buying electricity from a conventional power station.
There are now 250,000 small scale PV panels mounted round the country and that has been employing an extra 25,000 people all adding to our electricity bills for the next 25 years. A typical installation has to be installed by a MCS Certified Installer. This company has to be registered and have passed all the requirements to ensure that they check out the suitability of the roof structure, the loadings on the roof and the correct attachments for the type of tile. They also have to be certified to install an electrical system with voltages up to 400v DC and the requirements to connect the system to the incoming supply. Typically an installation has 16 panels, an inverter, the correct isolation switches, and a meter that records the output of the PV system on which the owner gets paid. This system is rated at 3.6kW and costs about £13,000 to install. The materials cost about £4,000, a days labour for 5 men at £60 per hour for 8 hours is £2,400 and the rest covers the Companies overheads and profit. The 3.6kW is the maximum size that can be installed without a study done by the local electricity company and a special meter being installed to show electricity in and out of the distribution system. On a bright sunny day when our PV is generating its full 3.6kW and the owner is not using any electricity, the Inverter has to raise the voltage high enough to push power back into the distribution system. If the local transformer supplies voltage at 245 volts already then the Inverter has to raise the voltage to 260 volts to feed back. This is the tripping voltage and the system shuts down. Multiple PV systems in your immediate area will fluctuate the voltage in your house.
Let us look at a PV panel. The sun shines at about 800 W/m2 in the middle of UK. The panel converts 14% of this to electrical power. The other 86% goes to heat up the panel. When the panels get too hot their efficiencies drop off. The other fact is that the PV panels are connected in series parallel and the output of the whole panel is only achieved if there is no shade on part of it from chimney stacks or trees. If the panels are fixed on the roof at the best angle for midday summer sun then this gives off 3.6 kW. At all other times there is a reduction of output. When the sun is at an angle then the power drops off dramatically. In the winter the sun angle is much lower and the rays have to pass through twice as much atmosphere and so the maximum power drops to 1.8 kW. If there is cloud cover it can drop the power to 150 W at midday in the winter or even nothing. Even with a sunny evening a clear sky and very bright, if the sun is not touching the panels there is no power. When the PV system has no direct line of sight to the sun and and at night they consume 20 W of power all the time.
Nearly half the power generated is produced in May , June and July, the other half is during the remaining 9 months. Our 3.6 kW system can produce 440kWh in say May. The arrangement for payment set up in April 2010 are 43.3p/kWh for every unit produced and a further 3.1p/kWh for half the units assuming the owner is not using all the units and these are going back into the grid. The 3.1p/kWh is of course the price the Electricity Company buys it from the large power stations averaged over the year. In December our system is lucky to produce 60 kWh. Of course this is the time of the year when most power is needed and at night the 250,000 PV units are all using 20W each to keep the inverters going.
So if we convert this electricity to money we are producing 2,675 kWh of electricity and that gives an income of £1,200 per year and a payback of 11 years. This is now considered far too generous which is why there has been a cut back of the 43.3 p to 21p on 12 Dec 2011. What is startling is that if the 2,675 kWh was bought from the local large power station it would only cost £83. The adverts in the papers are very misleading as they always talk about "free electricity" that is to the owner of the panels provided the PV generates about a third of his usage of electricity. The awful fact is that those without PV are subsidising the owner £1,117 per year on their electricity bills on £83 of green electricity generated. No wonder the electricity prices are climbing so fast and fuel poverty is spreading in British households.
It is worth mentioning that the PV subsidy will be paid for 25 years, the panels start to reduce in efficiency and the 14% will drop to about 11%. The panels cost about £130 and practically none are made in this country. The panels are mounted in aluminium and the cables connecting them are aluminium. The aluminium rails and brackets the PV panels are mounted on are all made abroad as we closed our last aluminium manufacturer in Wales in the winter of 2010. The Inverters are mostly made outside UK, they cost about £1,500 and have an average like of 12 years. I suspect this life is shorter than it should be because electronic equipment does not like to be too hot and companies tend to mount the inverter in the attic which overheats in the summer.
Guarantees are deceptive as some components are guaranteed by the manufacturer and some by the companies fitting the kit. If the PV industry winds down fast a lot of these companies set up to install PV will disappear with the guarantees. As new types of panels are made it will be difficult to replace a faulty panel in the middle of a run of 8 in a few years time. One area of weakness has been the brackets through the roof tiles have been flexing and cracking tiles and slates causing rain leaks. Repairs of this type may well require scaffolding as panels will have to be removed to get at the leaks. House insurance may be unwilling to cover this work especially if the home owner does not own the PV system and has rented out his roof.
So is PV in Britain a good idea when we have so much cloud? The maximum power is available in the summer when the electricity demand is at its lowest. Sun radiation is a fraction of that available in the tropics. Most people have installed PV as the Bank interest rate is so low they get a much better return on their £13,000 investment. No-one who has looked into it thoroughly believes this green energy is worth it. It is surprising it was even put forward by the Labour party as it benefits the wealthy and also surprising it has taken so long to cut it back. What is even worse is a third of our investment goes to overseas industry. Nobody has worked out the CO2 expended in making, shipping and mounting a set of PV panels and when the CO2 neutral date would be but at least the manufacturing CO2 emissions don't count against UK's emissions so that's all right.
Mike Travers, Saline, Fife
Next letter: Naive question