Free solar power system. Is it a scam?

jimbms

Cardew wrote: »

There have been a number of posts about 'harvesting' more of the generated electricity.

I wonder how much extra power you can save in the battery bank and then use in 12v lighting? 500 watts a day averaged over the year?

If so that is approx 200kWh a year - say £20 a year?

I wonder how much it would cost to rig up a charging circuit with batteries and run a 12volt circuit to the lights in your house - bearing in mind that many will not feel qualified to carry out this task - earthing etc.

As for the cost I could not be sure as I designed and built the circuit myself. But in saying that my profession is a building management systems design engineer and I have done many 12v and 24v lighting systems and the savings are superb, you need to consider that electricity you get from the grid is at most 35% efficient when it gets to you which is reflected in charges, whereas solar and wind power has a 70% rating on average, (of course the best way would be for us all to be able to produce methane by digesters using our waste and energy crops then use cogeneration via a CHP) now without going in to details why, calculation cannot be made using standard Kwh due to the facts that we are using DC circuits and they types of lighting is different in many ways so what gives the output of an equivelent 100w on a 240v AC circuit can in some cases have a pull of less than 5w on a 24v DC circuit. As for qualifications, that is a very grey area due to the fact you are using DC circuits and low voltage and the current IEE regs concerning domestic circuits of such are very vague (but wont be in the next edition). But all things considered it is not just about savings, as stated doing it local is more efficient and for evey Kwh generated locally you would need to generate almost 2Kwh at a power station. Anyway I could go on and on on this so I will shut up now.

Cardew

jimbms wrote: »

As for the cost I could not be sure as I designed and built the circuit myself. But in saying that my profession is a building management systems design engineer and I have done many 12v and 24v lighting systems and the savings are superb, you need to consider that electricity you get from the grid is at most 35% efficient when it gets to you which is reflected in charges, whereas solar and wind power has a 70% rating on average, (of course the best way would be for us all to be able to produce methane by digesters using our waste and energy crops then use cogeneration via a CHP) now without going in to details why, calculation cannot be made using standard Kwh due to the facts that we are using DC circuits and they types of lighting is different in many ways so what gives the output of an equivelent 100w on a 240v AC circuit can in some cases have a pull of less than 5w on a 24v DC circuit. As for qualifications, that is a very grey area due to the fact you are using DC circuits and low voltage and the current IEE regs concerning domestic circuits of such are very vague (but wont be in the next edition). But all things considered it is not just about savings, as stated doing it local is more efficient and for evey Kwh generated locally you would need to generate almost 2Kwh at a power station. Anyway I could go on and on on this so I will shut up now.

Sorry don't understand your post, particularly this section(and I would add that I am a Chartered Electrical engineer - so you can go into detail!!)

now without going in to details why, calculation cannot be made using standard Kwh due to the facts that we are using DC circuits and they types of lighting is different in many ways so what gives the output of an equivelent 100w on a 240v AC circuit can in some cases have a pull of less than 5w on a 24v DC circuit

I am not sure if you are referring to Power Factor or low power DC lighting(e.g. LED)

Why can't calculations be made using 'standard kWH'?

Power factor is not a problem in domestic situations as we are billed for kWh not kVA.

You obviously can have DC lighting powered from your mains AC voltage. So taking a specific consumption for your DC lights, say 0.1kWh, from your solar produced power, then you just save 0.1kWh from your mains electricity bill.

The savings using LED lighting would be minimal - a couple of pounds a year.

jimbms

As stated the point is not just the savings it is also we need to use more efficient generation i.e. local co-generation at 90% efficiency is far better for us than centralised individual generation at 60% efficiency. as you very well know in many commercial places lighting can be 70% of the energy consumption but this can be dropped to at least 30% if more efficient dali type lighting and 24v systems based on natural generation are used. For me I would say a vertical turbine is a lot more efficient tha photovoltaic cells due to the facts a 30Kw blade would take less space than cells and also in most places the chances of enough wind are far greater than sunshine and that is not even counting you also get nightime generation.

Cardew

jimbms wrote: »

as you very well know in many commercial places lighting can be 70% of the energy consumption but this can be dropped to at least 30% if more efficient dali type lighting and 24v systems based on natural generation are used..

I really can't see the relevance of that statement; you can drop the consumption demands of lighting in many ways.

However this discussion was started by you explaining that you utilize more of the solar generated power by having a battery bank and using DC lighting.

You now appear to be attributing a reduction in the power taken by your DC lighting, to solar panels - which is incorrect. The same reduction in power consumption would occur if your DC lighting was powered by the AC mains(via transformers)

Anyone with DC lighting who used a similar setup - battery bank, seperate DC lighting circuit - would save pennies; perhaps a pound or two a year.
I suspect a layman would have to spend £hundreds for batteries and installing such a system. That is neither money saving, or 'green'.

jimbms

I did say it would also involve looking at the way you use the power etc, this would also include maximum use of reflective materials. Dropping voltage and changing from AC to DC can never be as efficient as generating at the correct voltage and type and is only useful when it needs to be transmitted over distances. On a final not I did state that a combination of wind and solar is best. If you need more detailed info I suggest you use google as I tend to get bored very easy of repeated posts.

martint123

Any thoughts on funding an installation yourself and pocketing all the FiT yourself?
e.g. http://www.tescohomeefficiency.com/solar-electricity-price-examples/

mysterons

Well first thing that springs to mind is you're going to need the cash as opposed to this thread where a company is offering to install for free as long as they collect the FIT's and you reap any electricity produced if you can use it immediately.
If you check the Feed In Tarrifs Announced thread you'll see I already started the ball rolling with Tesco but it's proving hard going, a month passed and still no sign of a site visit. They have now sent me a flyer to claim a voucher for £500 off the cost of the Tesco PV install which I suspect is to keep me interested and not start looking elsewhere.
One thing that bothers me is the statement everyone is using that 'you will be deemed to export half the total generation' of your panels. That looks really good to me as I would no doubt consume all the energy produced. The killer would be if somewhere along the line the electricity supply company decide to install something that determines what you're really exporting and only pays you FIT's for that amount effectively wiping out any return.

martint123

I also got the Tesco flyer and had never shown interest in it, so I guess everyone has got one??
I think that the generation tariff is fairly well cast in stone for 25 years and will always be separate from the Sell-back tariff. I took the "half export" to mean that you get the full generation all the time by what you generate and instead of measuring what you actually feed back for the smaller tariff, they work on an industry average value.
Otherwise the company in this post would be in deep doo-doo if income depended on usage.

Cardew

mysterons wrote: »

One thing that bothers me is the statement everyone is using that 'you will be deemed to export half the total generation' of your panels. That looks really good to me as I would no doubt consume all the energy produced. The killer would be if somewhere along the line the electricity supply company decide to install something that determines what you're really exporting and only pays you FIT's for that amount effectively wiping out any return.

I think you have misunderstood the FIT system.

If it is your own system, you get the FIT(41.3p) for every kWh your panels produce, regardless of you using all of that electricity in the house, or none at all. So if your panels produce, say, 2,000kWh you will get £826.

The 'deemed to export half the total generation' is for an additional payment of 3p per kWh for anything you don't use in the house - so in the case above you would get 1,000kWh x 3p = £30 on top of the £826.

Obviously the more electricity you can consume in the house, the greater the benefit as you save around 10p/kWh.

It would be virtually impossible to 'consume all the energy produced' in the house as you believe. You cannot 'match' the solar electricity produced to your electricity demand. Most people seem to be able to use 40% to 50%.

noncom_2

EDIT - Crossed Posts With Cardew Above

mysterons wrote: »

One thing that bothers me is the statement everyone is using that 'you will be deemed to export half the total generation' of your panels. That looks really good to me as I would no doubt consume all the energy produced. The killer would be if somewhere along the line the electricity supply company decide to install something that determines what you're really exporting and only pays you FIT's for that amount effectively wiping out any return.

The biggest part of the Feed In Tariff is paid for every unit GENERATED - so that's 41.3p per kWh even if you use it all yourself.

Assuming you do use every unit you generate in your own home, the bulk of the FIT payment would still be paid to you. All you would lose out on is the extra 3p per unit exported. If the energy company assumes you're exporting 50%, then from a typical 3kW peak system generating, say, 2500 kWh per year, you'd get paid 2500 times 41.3p for generation, which is just over £1000, plus 1250 times 3p for the export, which comes to £37.50. If the company then fits a meter and decides that you're not actually exporting any, all you will lose is that £37.50. On the bright side, for every unit you use that you would otherwise have had to buy from the grid, you're saving whatever you pay your supplier per unit (typically 10-14p).

I hope I've explained that OK.