Solar Panels

Better places to look for answers would either be the In My Home board or on the Utilities board.

A quick search shows that Fuel & other heating has some good threads there, including a sticky on grants, so I'll move you across.

kittiwoz wrote:

I did a module on renewable energy sources as part of my degree and also looked at domestic power generation as part of a module on future planning.

Basically photovoltaics are too expensive and not efficient enough to produce a pay back inside the life-time of the product. I expect that technological improvements and mass manufacturing efficiency will see them start to become viable in about 10 to 20 years from now with them becoming a comon sight in 30 to 50 years.

Solar hot water heaters are much cheaper to install. They use simple technology and are more efficient. You can get a grant towards installation costs and are likely to see a pay-back in a few years.

Wind power is really coming into it's own right now and I predict a surge in uptake which will make domestic windturbines a common site in 5 to 10 years time. Once a lot of homes have existing grid connections put in place for wind turbines it will pave the way for pV cells.

I wrote a more detailed answer to a similar question here. This is another similar thread.

ITV news today had a few minutes about a house that they are sponsoring(I think). The roof panels and system cost £12,000 and they got a grant of £6k towards that. The wattmeter held by the owner showed that it was producing 293 watts!!! Enough said.

Interested in your comments on solar water heaters and pay-back term. Could you please give some approx figures on which that prediction is made.

As you might have read in the thread(you gave a link to) I have not seen any figures that show it is viable.

My contention is that the average family spend £100-£150pa on domestic hot water. Most sources I have read believe that an average system will save approx 50% of those costs. So £50-75pa.

Leaving out the cowboys who operate in this field, I think we are talking £3000+ (after grants) to have a system fitted?

Just the cost of borrowing £3000 will be in the order of £180pa before you consider paying for the system, then there is the cost of running the pump and servicing and anti-freeze etc.

Obviously you have the technical knowledge and if any of my figures or logic is flawed, please let me know.

I really would welcome a 'grown up' discussion on the economics of solar heating.

The panels cost from £2,000 to £3,000 for a flat plate collector and £3,500 to £5,000 for evacuated tube. You can get a £400 grant on top of that. A DIY job would be from about £1500 to £2500.

However the main reason for the difference is that I overestimated the typical cost of domestic hot water significantly. I made an estimate based on our energy bills over the past few years. I guessed that water heating proabably accounted for about 1/3 of the bill. I've just found some info on the net which suggests a value of 20% would be more typical and this would equate to £138. This means a total annual fuel bill of £690. So I would also have over estimated because our annual spend is a lot higher than that. I think I would have been basing that on an £900pa energy bill, 1/3 of which on water heating with a 60% saving provided by solar water heating and factoring in the £400 grant.

If you are only paying £100 to £150 a year for your hot water then it's not going to be worth it. However if you use a lot of hot water it would be worth considering. Also if you live in Scotland you get a larger grant (30% of the installed cost) which might make it worthwhile.

Actually wind turbines are just starting to become viable for most people about now. Between the rising cost of fuel and the falling cost of the turbines with increased productions this is a technology which is ripe to take off. They will probably be better value in a few years time. In ten years they will be a common sight. I'd put money on it. Sorry about the dodgy data re. solar DHW but the following figures are good; sourced from respected publications, the EST and ClearSkies websites and the Swift Turbine data sheet:

Renewable Devices has developed the roof mounted "Swift Turbine". This typically provides 2,000-3,000kWh of energy per year. They cost £5,000 when they were launched but this is expected to drop to about £2,000 by the end of the year due to increased production. You have to contact them to find out the current cost but with a grant for 30% of the cost available from the Clear Skies Initiative you would make your money back on an initial cost of £5,000 in 14 years and on £2,000 in 5.6 years assuming a saving of £250 a year.

With regard to the cut in speed and speed at which power is rated it is clear you have no concept of what are normal wind speeds so I will try to enlighten you without getting into too much technical detail. This machine reaches rated power at 12.5m/s, this is very typical of the speeds at which power is rated for wind turbines. It is as you say equivalent to 28 mph or Beaufort 6. This is described as follows: "Strong breeze; large branches in motion, whistling heard in telegraph wires, umbrellas used with difficulty." The cut in speed of 2.3m/s is equivalent to 5mph or Beaufort 2 described as a "light breeze; wind felt on face, leaves rustle, ordinary vanes moved by wind". I hope you can now see that these wind speeds are quite appropriate for a land based wind turbine.

The figure 2,000kWh to 3,000kWh is the result of testing. It says "up to" because the 3,000kWh was achieved at a test site in Edinburgh. The lower figure gives an idea of what to expect in less windy areas. You will see that it is very far from the figure which would be arrived at by simply assuming constant operation at the rated power (1.5kW * 8760hrs = 13140kWhrs). I have assumed 2,500kWh at a price of 10p per kWh which is not unreasonable.

You are correct in saying that I have factored in the available grant, which is reasonable since the machine is designed to meet the specifications of the grant, and also that I have not considered the cost of borrowing. Also I have assumed a constant energy price and have not taken consideration of the reduced value of future money. This is because the figures are only intended to demonstrate that this is a technology which is becoming financialy viable, not as a detailed cost benefit analysis. If I was trying to provide that I would have to know how much they cost, whether you would have to borrow some or all of the money and how much interest you would be charged. I think you are asking too much, frankly.

Please note that I have only said that they are "starting to become viable" and that I clearly stated that my figures are "with a grant for 30% of the cost" and "assuming a saving of £250 a year." I have also said that I expect the price to be reduced as a result of mass manufacture in a couple of years.

Finally while you may have "strong reservations about their claims" other people are happy with them. They signed a three year £9m deal with Scottish and Southern Electric in 2004. As reported in the IMechE publication "Professional Engineering", vol 17, no 19, published 10/11/04, production numbers were then "running in low batches of 15 to 20, but will be ramped up to 2,000 within the three years." Hence the expected price reduction.