[Closed] Have solar panels on the roof had their heyday?

Will energy costs go up or down in the future? If your staying put look at things like the power wall and changing your thinking (washing machine and dishwasher on during the day etc.)

depends where you live. Kent I would say yes. lochaber I would say no

Solar thermal?

The FiTs have come down so much now that it's going to take a long time to repay the installation costs (which have come down too but not by as much) through energy savings alone.

One of my colleagues who got in early makes £2,500 cash a year from his. All a bit unfair and counter-intuitive really.

According to the figures on the Scottish Homebuyers Report for my house I would have to live until I was 190 to see a return on investment for solar panels on the roof!

Move to the West of Scotland and fit hydro electric turbines in the rainwater downpipes of your house...you'll never pay another leccy bill in your life.

A near neighbour of ours updated his 6 or 7 year old system last year. The doubling of the number of panels, upgrading wiring and control boxes etc would have cost him about half what the original install did (if you take all the grants out of the equation).
His original system had about 2/3rds paid for itself as far as he could work out. (It's a bit tricky to work out as the tariffs have changed a couple of times, and there's a completely new system now he's upgraded his control box)

Me, i'll get solar thermal, it's cheaper and most (more than 50%) of my energy consumption is for heating/hot water anyway.

I don't understand why wind hasn't take off for homes?

Its plenty windy where we live.

Is it just that you need to big a turbine to get enough juice? B&Q did sell them for a while.

You need a big, tall turbine, big to get enough wind, tall to get away from roof lines, trees, turbulent flow, noise.

Best left to large scale installations.

Wind would probably be space. As for feed ins etc just remind me how much generation capacity is planned to replace all the stuff going offline. With a reduction in coal and gas, escalating and volatile gas pricing and lots of capacity at end of life I'd take the gamble that self generation will become more attractive. Again with storage coming online you don't need to rely as much on fit as your using your own more not paying for other people's.

Agree with using the sun to heat water. Very simple installation and would save lots on heating water.

They have been doing this lots in Portugal for years. Friend of the family has a business out there doing just this.

Scalded my arm once when I turned the tap on.... It was about 3am. Still hot!

I was looking to buy a place where the owner had installed a few impellers in the stream to charge some car batteries which provided lighting.

Solar is pretty marginal with the current regime. We were estimated about a 20 year payback, but the panels might hardly last that long. It works out better if you use a lot of daytime electricity in the summer, but who does that?

As for wind, the power you get is just too small to be significant. Plus noise and maintenance issues.

Think the next big thing will be domestic biomass.

Chap i work with is tinkering with a home biomass "system", uses an old pellet burner thing to power a small steam turbine/generator and some other stuff, reclaims a lot of the waste heat as well. All self built and bodged up, uses half a dozen PLCs and an old PC to run it and link it into his home CH system.

Efficiency is pretty poor, but it works. Cost him virtually nothing, so despite the poor efficiency his only ongoing cost is pellets.

And his wife hates it.

Photovoltaic cells aren't particularly expensive to make.
Weather-proofing (which usually means encasing in resin), installation and certification (needed for feed-in tariff) are the expensive bits.

If you can find a way to get the installation and certification parts cheaper, it may well work out.

Agree with others that heating water is a good use.

I have a box of tricks on my PV install that works out if I have spare capacity and dumps it to my immersion heater, was only a couple of hundred quid add on and means most of my summer water heating is done by solar, but without the added plumbing cost (and possibly needing a new tank) that "wet" solar water heating would entail.

Jeff

We have 2 panels on our roof for heating water. Its brilliant. We don't have central heating so immersion heaters are our only other option. On very sunny days we've had water in the tank measuring over 85°C.
On less sunny days it heats it up to about 30° meaning the immersions have to do less.

And we are in Wales!

I'm in Scandinavia and solar is a viable option........ most of the year.

You need a big, tall turbine, big to get enough wind, tall to get away from roof lines, trees, turbulent flow, noise.

Best left to large scale installations.

Solar thermal?

I forgot about the tesla batteries..that would be ideal - use NO 'leccy from the grid..
I'll look into that.

On a side note - when I get my lad's play house built I'm going to get (from China) a little turbine and PV pack (about £150) to teach him about all this! It'll be standard for our kids, I reckon!

DrP

Got one on the roof of the van, works great when wild camping.

http://www.soltechenergy.com/en/product/soltech-sigma

That's one thing that pinged up on my searches for solar thermal. We'll need a new roof at some point in the next 5-10 years. We'll possibly do this, budget allowing. You'd probably only need the accumulator and some sort of control system to connect it to your existing radiator set up.

I reckon we'd need a bigger reservoir to connect to our system.

when I get my lad's play house built I'm going to get (from China) a little turbine and PV pack (about £150)

Careful, only use it in a cake tin, you don't want to burn his play house down 😉

had a look into this sort of stuff.

Basically you need to spend >20k to get any tangible benefit. The wind turbines were done by witch mag a while ago and wernt worth the outlay.

insulation was the best bang per buck.

If your staying put look at things like the power wall

Have you seen what they cost?

Doubt you'd make your money back in years....

It works out better if you use a lot of daytime electricity in the summer, but who does that?

We average about 75p/day on leccy.....

solar PV can still be worth doing but you wont be getting 'rich' off it. if you use a lot of leccy during the day then you'll benefit most.

You shouldn't be paying much more than £4-5K for a 4kW system installed on a standard roof.

until we get smart meters that can measure(and allow you to be paid for) your export then sticking excess into a hot water tank is a good thing. sort of.
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as for domestic solar thermal - depends what fuel you'd be replacing, and how much hot water you use. There are loads of ways to maximise the benefits of solar year round but they all need reasonably bespoke heating systems (think underfloor heating, a mix of heat sources and a very well insulated house) but for a standard solar panel/hot water tank setup, the numbers are something like the following:

a 210 litre cylinder needs 13.5kW hours to heat to 60degC. a properly sized solar thermal system (approx 4msq of flat plate collector) will do this, on average, half the year. that's 13.5 x 180 kWh = 2430 kWh of energy per year.

if you are on gas, you'll be paying about 3.5p per kwh - that's a saving of [u]£85[/u] a year.

oil at 5p/kwh saves you £120, LPG approx £145

ubnless you DIY, you aren't going to get a decent system installed, with cylinder change, for less than £3K. you can do the sums.

you will cut your carbon footprint, you will feel slightly better for doing that, you wont save money.

What is the best sort of setup if you want to combine a solar thermal rooftop system with your household hot water system?
I'm about to replace my boiler and I'm wondering if I should be looking at this option...

There are a tiny number of new build estates with solar panels built into the roof, rather than mounted on top. I think this is the way to go, minimising the expensive installation as all the scaffolding and whatnot is up already and there's work going on anyway. It's disappointing that the government scrapped the tighter regulations on home efficiency as this would be much more common otherwise.

I'd quite like some for our house, but I'm under no illusion that it would give any financial return; our leccy bill is pretty tiny anyway, so it would just be because I'm a hippy who would like to help stop getting our energy by pumping it out of the ground.

you will cut your carbon footprint, you will feel slightly better for doing that, you wont save money.

But if you include the CAPEX CO2 cost of the extra HW etc, then you'll have to wait a few years before you start cutting your total carbon footprint through lower OPEX CO2.

Hmm..maybe i'm just trying to fuel (chuckle) the 'feel good' part of my concious..
When we had the loft done there's tonnes of insulation as per new BRs, and LED lights throughout.

Maybe this is a non starter unless there's bigger incentives...

Time to chuck another manatee on the log burner...

DrP

Time to chuck another manatee on the log burner...

You Monster!

Do you know how much CO2 is released into the environment when you burn a manatee??

Environmentally sustainable dugong would be a better option.

Manatee's are rubbish - you need an Elephant Seal to get a decent calorific output.

I don't understand why wind hasn't take off for homes?

Its plenty windy where we live.

It's because although it is comparatively windy, the amount of energy you can extract from the wind is still lower than what you can get from solar panels (yes, even somewhere like Britain)

Wind turbines (even decent sized ones) in built up areas don't generate enough energy to offset the carbon dioxide generated building and installing them, so are completely pointless.*

*This was the case a couple of years ago anyway, I would imagine one day we'll be good enough at making them that this is no longer the case.

Now they've stuck the offshore wind farms up off the coast of Worthing, I might install a wind turbine actually.
Not sure why they needed more wind farms - it's windy enough here already without farming more....

DrP

Not sure why they needed more wind farms - it's windy enough here already without farming more...

EU quotas, although now we're leaving they might just let all the wind die.....

Think of the baby robins footflaps!
How will they [s]die smashing into the ground[/s] fly away safely?

re opex capex and the savings numbers quoted and ruthlessly barging past he OP with total disregard.

It kind of depends where you are in terms of your current system.

If Project Divorce and Bankruptcy goes ahead we'll be buying an old farm house currently heated by LPG with approx 0 inches of insulation and several pitches of roof that currently give direct ventilation and hydration access. From this starting point a complete refit with thermal stores running from solar theraml, wood burner and a small oil fired reserve makes economic sense producing both hot water AND space heating. But this is at the far end of the spectrum.

As can be seen from my other post on the subject solar hasn't had its day just yet, storage battery technology is giving it a 2nd lease of life at least down here in sunny Kent.

for a standard solar panel/hot water tank setup, the numbers are something like the following:

a 210 litre cylinder needs 13.5kW hours to heat to 60degC. a properly sized solar thermal system (approx 4msq of flat plate collector) will do this, on average, half the year. that's 13.5 x 180 kWh = 2430 kWh of energy per year.

if you are on gas, you'll be paying about 3.5p per kwh - that's a saving of £85 a year.

oil at 5p/kwh saves you £120, LPG approx £145

ubnless you DIY, you aren't going to get a decent system installed, with cylinder change, for less than £3K. you can do the sums.

you will cut your carbon footprint, you will feel slightly better for doing that, you wont save money.

THis is exactly what I reckon my DIY system is saving us, I put 20 vacuum tube collectors on the roof facing SW and in high June we get 160 litres of water at 60c, which pre-heats the water entering the main house cylinder. It was a simple system to install and cost me about.... £850! So, ten years.

, storage battery technology is giving it a 2nd lease of life at least down here in sunny Kent.

I'd like to see a full cost analysis inc CAPEX costs for that. Given most Li-ion packs are only rated for 500 cycles, you could be replacing the batteries before you've paid them off....

Just ordered PV cells for the house. With the current FIT alone it will take 12 years to recoup the investment, with energy bill savings more like 6 years. It helps that we have space for a 4kW system pointing directly South for this.

We're not really doing it for the cost, more for the fact that they'll repay their CO2 cost in about 2.5 - 3 years.

I don't understand why saving the planet (and reducing costs)has to have a capitol cost recovery element, you buy a car/bike, you lose money, you never think oh how many bus/train fares I've saved.

You buy the battery which sits in the garage alongside the expensive road/xc/dh bike and feel better about yourself, smug actually, until the error messages start and you discover the company that installed it closed the day after you signed off on your installation.

Then Tesla come along and announce their 650b version of your 26"Battery.

I don't understand why saving the planet (and reducing costs)has to have a capitol cost recovery element, you buy a car/bike, you lose money, you never think oh how many bus/train fares I've saved.

The difference is that the car/bike etc allow you to do something that you can't do without them. Most folks can still get plenty of electricity to their house without panels/batteries etc so there needs to be a different incentive.

I don't understand why saving the planet (and reducing costs)has to have a capitol cost recovery element

Because if you don't consider the energy cost of the CAPEX, you're just fooling yourself. If you buy a system which took 15 tonnes of CO2 to make, but save only 1/2 tonne of CO a year, then it will take 30 years before you're break even in CO2. If the system only last 25 years, you've done no good at all and just increased your carbon footprint.

But replacing like for like will have an energy capex too, so they need to consider that too.

But replacing like for like will have an energy capex too, so they need to consider that too.

of course...

But unless the existing system has died, leaving it alone is probably the best thing to do even if it's very inefficient.

A Pv panel will generate enough energy to cover its carbon capes in about a year.

Post grad thesis on this subject about 6 years ago by a colleague of mine.

A Pv panel will generate enough energy to cover its carbon capes in about a year.

If that were true, it should also break even without the FIT tariff in the same time. The fact they don't break even financially, for years (even with subsidies), suggests they won't break even in CO2 very quickly either (as most of the cost of buying one is the energy cost of making it and transporting it etc).

If that were true, it should also break even without the FIT tariff in the same time. The fact they don't break even financially, for years (even with subsidies), suggests they won't break even in CO2 very quickly either (as most of the cost of buying one is the energy cost of making it and transporting it etc).

not really - the financial cost of production is very different to the carbon cost of production. there's no profit element in carbon terms - there's huge financial profits on PV panels.

there is a spread in terms of the carbon cost - a norwegian panel like the REC range will be made using lovely carbon free hydro power, a similar chinese panel will have a much greater carbon content.

having said that, a quick google failed to turn the reference i had recalled, but others suggest 2.5-5 years (see CAT, US doEnergy)

But unless the existing system has died, leaving it alone is probably the best thing to do even if it's very inefficient.

That's worth repeating.

Get the full life cycle from the existing installation before it's even worth starting to think about getting a fancy efficient replacement.

A Pv panel will generate enough energy to cover its carbon capes in about a year.

At what latitude? Granted, on the equator, there's a lot of sun.

IIRC the Chinese panels currently being installed north of the Med have a tough time breaking even over their lifetime. Produced using massively dirty electricity, shipped long distances, lower efficiency, shorter lifetime / reliability levels, vis-a-vis expensive European panels with their higher cash cost.

We have had solar panels for the last three years.

Installation cost was £7000 for a 4kw system, with a device which also heats the water during the day.

Our electricity bill has dropped by about £200 a year.

We usually get paid about £800 a year tax free from the FIT.

This year has been the worst of the three years in terms of energy generated, the sun seems to have gone away.

I look at it this way.

I've spent the £7000, and if I had bought a more expensive car, then that money would have depreciated and the car would be losing value and costing me money.

At least this way , my £7000 is providing me with approx £1000 of income each year.
I'm happy with it.

not really - the financial cost of production is very different to the carbon cost of production. there's no profit element in carbon terms - there's huge financial profits on PV panels.

Is that the case?

PV panels is a pretty competitive market, so I would expect the net margin to be 5-10% at best.

The gross cost of making one, shipping & installing will be pretty close to the energy cost which is directly proportional to the CO2 cost.

The energy produced by the panel and it's saving is a saving from not buying energy off the grip which is directly proportional to the CO2 saving.

So if they were break even in CO2 in under a year, I'd expect break even in £ around a similar period (within a factor of 2 ish).

A domestic installation with a FIT rate of the real energy cost exported (ie no subsidy) would take 20ish years to break even. So I can't see how the CO2 can break even in under a year...

NB I'm not for or against PV, just interested in the Maths...

There's a lot of mixing units here.
£ are not directly linked to tonnes of CO2

Panels are quite cheap. Cells even cheaper (repeating what I said about weatherproofing).
Installation and certification are the big expenses.

FIT don't pay as much as you buy a kWh, so you can't say that the £ are linked to the CO2 for lots of reasons.

£ are not directly linked to tonnes of CO2

It should be roughly proportional overall as most of the cost of doing something is the energy cost involved (in our petro economy)...

I realise it's a back of the fag packet analysis, hence I'd love to see the real numbers end to end inc all manufacture, installation and transport costs etc for a domestic installation.

FIT don't pay as much as you buy a kWh, so you can't say that the £ are linked to the CO2 for lots of reasons.

I thought the FIT rate was more than you buy (or used to be) - or was it set at 50% assuming you used half and exported half?

Some maths:
https://info.cat.org.uk/questions/pv/what-energy-and-carbon-payback-time-pv-panels-uk/

The gross cost of making one, shipping & installing will be pretty close to the energy cost which is directly proportional to the CO2 cost.

The guy we spoke to said that about half the £££ cost of the install is manpower, scaffolding and fixtures/fittings - pretty hard to account for in terms of carbon cost.

Some maths:

No maths, just a few single summary numbers.

The thing which will make a big difference is do they just consider the CO2 cost of a panel or the gross cost of shipping it from China to the UK, storing it, having a local company drive and buy it from a warehouse, store it again, then transport it again to site and install. All of which bump up the cost form a few £ in china to costing £100s installed on a roof (and also bump up the CO2 cost).

Hence, why large scale solar farms make much more sense.

No maths, just a few single summary numbers.

(in our petro economy)

Denis99, sure it's great if you can get a 14% return annually. But the current FIT doesn't do that, it's not close. I could have put £7000 on the roof and got about 4% per year and in 20 years the system is (probably) knackered before I even get my money back. Or else I could have bought ARM shares and doubled my money in 6 months, which is what I actually did 🙂

i'm going to backtrack a bit and admit a mistake - i said the pv panel recouped its carbon capex in a year - sorry, i should have said its energy cost. The carbon cost varies by so many factors as pointed out by smart cookies above that i doubt you could ever have a 'one size fits all' carbon payback figure.

The wind turbines were done by witch mag a while ago and wernt worth the outlay.

Probably a biased report as they interfered with their broomsticks.
I'm here all week.

captain - you are right about current fits.....

4kw system will generate ~3200kwh/annum. fits is 4.25p, export is 4.91 deemed on 50% of generation. you'll get

£136 Fits (3200 x 4.25p)
£78 export (3200 x 50% x 4.91p)
£208 saved off energy bill (assuming you use 50% at 13.5p)
£56 if you push excess to hot water tank and offset gas usage (1600 x 3.5p)
£480/annum.

dennis got in at the 21p fit rate IIRC. i did it at the start so get 49p right now. 🙂

theres a pretty good calulator here.

[url= http://www.pvfitcalculator.energysavingtrust.org.uk/ ]EST PV Fit calculator[/url]

[quote="footflaps"]Given most Li-ion packs are only rated for 500 cycles, you could be replacing the batteries before you've paid them off....500? This is where smart charging and optimised conditioning cycles comes in.

If you just bang in current to 100% and empty it down to cut out (about 3.0v per cell from what i can remember) you might only get 500 cycles, and a hot battery. Thinking a bit more technically, running it from 3.6v to 95% full and keeping the temperature controlled (fans, refrigeration, whatever) might loose a chunk on capacity and efficiency (or you'll need a bigger battery to get the same capacity) but you can (easily) get to a couple of thousand cycles before capacity (that 95% threshold) is limited by any drop offs in battery performance. And at least another 1000 before it needs replacing.

Having a bigger battery might cost more, but the long term gain is well worth it, especially as you're effectively unlimited on space and weight, same goes for posh charging equipment and cooling gear. You can steal the excess heat too.

I got mine and the one before that and the one before that without any consideration for CAPEX I did it because I can and if feels the 'right' thing to do. I'm not going to lecture y'all about the carbon footprints of your bikes, cars, white goods, kitchens, log burners, wifes shoes, handbags, jewellery, your plasma telly's the ridiculous wages you encourage by watching soccer, which is just as nonesensical as concerning yourselves with the potential or lack of investment these systems afford, they exist and every kw I generate means I don't pay the robbing bastard French and I can feel in some small way I'm doing my bit to counter the excesses of others, that is all really. One day I shall get a wind machine if I could find someone knowledgable enough to link it into my battery system and if I could come right off the grid entirely, wouldn't I be a happy bunny?

This blogpost quotes a study which claims that for temperate latitudes more energy is produced making solar panels than they produce over their lifetime. Then of course the CO2 of production is in the atmosphere now while the CO2 savings will only accrue over the next 20 years or so.

http://euanmearns.com/the-energy-return-of-solar-pv/

You need a big, tall turbine, big to get enough wind, tall to get away from roof lines, trees, turbulent flow, noise.

I grew up on a cattle ranch in Nebraska and we didn't have electric power lines onto the ranch until I was about 5 or so. We had a wind-charger mounted on about a 50 foot tower that fed a big bank of batteries. Wasn't great, but did provide enough power to run lights, etc. for a few hours each evening. God, am I getting old or what? 🙄

Bizarrely I'm off to Nebraska after Christmas as the power company I work for is based there.

But the install costs, and reading about the FIT dropping and dropping, make me think 'is it worth it'?

Thinking a bit more technically, running it from 3.6v to 95% full and keeping the temperature controlled (fans, refrigeration, whatever) might loose a chunk on capacity and efficiency (or you'll need a bigger battery to get the same capacity) but you can (easily) get to a couple of thousand cycles before capacity

100% DoD 300–500
50% DoD 1,200–1,500
25% DoD 2,000–2,500
10% DoD 3,750–4,700

(table from battery university site)

I think that figures out to get around 50% better total capacity over usable battery life, by using 50% discharge cycles.

95% full is way too much, BTW - charge cutoff at about 80% [4.05V ish] for maximum life, drain down to 30%. Rinse, repeat.

Temperature control isn't that big a deal for continuous use. Its a problem for long term storage, if that's part of your use pattern, but for daily cycling like this? Might as well forget about it. The battery will become warm internally from charging & discharging anyway. Incidentally, running a refrigerator to maintain battery temperature to improve battery life by a % or two? You just shot your carbon footprint in the foot...