Archive for Downsizer For an ethical approach to consumption
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Lorrainelovesplants
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dilemmaI would like to get solar panel on our house - this would reduce our electric bill and help save the planet.
The only bit of our house that points the right direction has a flat roof - which we would like to convert to an apex roof. We have had an architect round and been to see building control. We estimate that gettingt the structure up and watertight will cost about £3000. (John will do a lot of the work himself).
We dont have the money really, but could scrape it together. The solar panels would be a scheme - run to the sun probably,
BUT
this would mean getting the thing up before April to get the current FIT.
Dilemma - Is it really worth(financially) all the hassle?
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Katieowl
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You'd have to buy the panel on top? Not sure if you don't 'really have the money' you should risk it. Supposing something else came up that you 'had' to afford? Is that a likely scenario? It takes a long enough time to recoup the cost of installation anyway, without another three grand on top.
I feel your pain on wanting to reduce your electric bill though 
Kate
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gz
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Don't you have to use an approved installer to get FIT ?
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Lorrainelovesplants
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yes, it would be a proper installer.
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Jb
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My initial thought is probably not worth it.
Solar PV panels are about 20% efficient at maximum. Halve that for night time and halve it again for the fact that most of the time it's not pointed directly at the sun and half it again to allow for off days, losses etc (as you can tell this is a _very rough_ calculation)
So solar PV generates about 25W /m2 or over the course of a year about 200 KWh / m2.
Electricity is about 15p / KWh so that's about £30 / m2 per year.
How much do the solar panels cost?
Evacuated tube solar systems might be better.
Solar PV should be a good option but not until the panel costs fall a lot more.
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Jb
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Oh and beware of some of the schemes they depend on feed in tariffs which could fall in future and which also leave you effectively renting out your roof space to someone on a long term which can be a problem if and when you need to move.
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RichardW
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My initial thought is probably not worth it.
Solar PV panels are about 20% efficient at maximum. Halve that for night time and halve it again for the fact that most of the time it's not pointed directly at the sun and half it again to allow for off days, losses etc (as you can tell this is a _very rough_ calculation)
So solar PV generates about 25W /m2 or over the course of a year about 200 KWh / m2.
Electricity is about 15p / KWh so that's about £30 / m2 per year.
How much do the solar panels cost?
Evacuated tube solar systems might be better.
Solar PV should be a good option but not until the panel costs fall a lot more. |
Your assumptions are so far out I dont know where to start.
Forget efficiency per m2. It is just not relevant unless space is worth more than the increased cost of high efficiency panels.
Roughly each kWp of array will make 1000kwh per year.
That is worth £ 433 in FIT's payments for production plus £33 for deemed export plus the saving on not importing any power used onsite say £48 if you use 400 units. Thats £514 per year which is inflation linked so will rise most years for the next 25 years.
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Nick
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http://www.moneysavingexpert.com/utilities/free-solar-panels
This just arrived in my mail. Don't know if it's accurate, or useful, but it is fairly clear.
Rich, you're fairly knowledgeable, is it on the money?
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Jb
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My initial thought is probably not worth it.
Solar PV panels are about 20% efficient at maximum. Halve that for night time and halve it again for the fact that most of the time it's not pointed directly at the sun and half it again to allow for off days, losses etc (as you can tell this is a _very rough_ calculation)
So solar PV generates about 25W /m2 or over the course of a year about 200 KWh / m2.
Electricity is about 15p / KWh so that's about £30 / m2 per year.
How much do the solar panels cost?
Evacuated tube solar systems might be better.
Solar PV should be a good option but not until the panel costs fall a lot more. |
Your assumptions are so far out I dont know where to start.
Forget efficiency per m2. It is just not relevant unless space is worth more than the increased cost of high efficiency panels.
Roughly each kWp of array will make 1000kwh per year.
That is worth £ 433 in FIT's payments for production plus £33 for deemed export plus the saving on not importing any power used onsite say £48 if you use 400 units. Thats £514 per year which is inflation linked so will rise most years for the next 25 years.
Not saying you're wrong but which of my assumptions was so far out?
Solar panel efficiency (from here) suggests efficiency in the range of 9% to 15% so I was a little generous there.
It is night half the time (pretty sure on that assumption 
)
Tilting a plane around a circle means that the average area presented to a point is 2/pi of the plane's area. (I rounded to 50% for convenience)
Incident solar radiation is 1400 J / m2 / s (I remembered that as 1000)
Use 50% for system efficiency and that gets us down to 33 W / m2 and my ultra quick calculation said 25 W/m2.
Cost per square metre does matter because you need to buy so many square metres of solar panel, for example Kyocera's panels work out as about £350 - £400 / m2.
Feed in tariff is far more generous than I thought. (which might be a bad thing as it could lead to accusations that solar PV doesn't justify itself in the same way that German wind turbines are accused of being cost effective but bit energy effective)
Nicky cigreen
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how long do PV panels last?
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Bebo
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how long do PV panels last? |
The ones we're getting have a 25year manufacturers guarantee. The other bits of the system have varying guarantees on them.
Lorrainelovesplants
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Nick
tried to read this....cant open....what do I do?
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sean
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It's a link to MSE. I think you may have to sign up to get access to the full report. At a wild guess.
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Lorrainelovesplants
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Read the MSE link....
I think we will sit tight till the solar thermal FIT - this is the one that we think will benefit us most.
I cant justify spending money at the mo, and even though I could take out a loan to part finance apexing the roof and buying solar panels. I cant justify waiting 25 years to see the profit.
yes, i will still have to apex the roof in the next year or so, but Ill have to deal with it.
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bagpuss
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It's a link to MSE. I think you may have to sign up to get access to the full report. At a wild guess. |
shouldn't of thought so, not generally the way MSE works
Dee J
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Not sure where the cost of the pitched roof comes into the scheme.... I'm sure converting from flat to pitched roof is a good idea when it comes to weather resistance and insulation, but it's not necessary for solar pv. There are plenty of arrangements for securing pv panels at the correct pitch and orientation over a flat roof.
Dee
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pyrotech
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I think Richards estimates are pretty damn close to fact, We've a 2.96 kwp array and last year it generated april-march just over 3000Kwh and earned more than 10% of its installation cost under FIT scheme.
The panels are roof mounted and about 5%'s off of true south.
Can I suggest you use one of the calculators say :
http://info.cat.org.uk/solarcalculator
or
http://rredc.nrel.gov/solar/calculators/PVWATTS/version1/
I used them to good effect when planning.
But remember the difference in production between summer and winter is vast.....
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Lorrainelovesplants
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Have decided to hold offon the project - I cant afford to do the pitched roof at the mo (but it does need done in the next year or so, as will be time to renew flat roof covering anyway).
Ive never really accepted that solar electric is 'there' yet, due mainly to all the concversations and info on here and in magazines.
I'd rather wait to get solar thermal.
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Mutton
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Mentioning my favourite solar panel website again (solar thermal mostly)
www.builditsolar.com
Lots of DIY designs and in some cases extended test results. Sounds like your OH is good on building things, so take a look. Brings cost down sharply.
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Lorrainelovesplants
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Thanks Mutton - he is very handy (and has plumbing & water regs). He put all our LPG central heating in when we moved here, and our woodburner with back boiler, so the solar was the next logical step.
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RichardW
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Not saying you're wrong but which of my assumptions was so far out?
Solar panel efficiency (from here) suggests efficiency in the range of 9% to 15% so I was a little generous there.
It is night half the time (pretty sure on that assumption )
Tilting a plane around a circle means that the average area presented to a point is 2/pi of the plane's area. (I rounded to 50% for convenience)
Incident solar radiation is 1400 J / m2 / s (I remembered that as 1000)
Use 50% for system efficiency and that gets us down to 33 W / m2 and my ultra quick calculation said 25 W/m2.
Cost per square metre does matter because you need to buy so many square metres of solar panel, for example Kyocera's panels work out as about £350 - £400 / m2.
Feed in tariff is far more generous than I thought. (which might be a bad thing as it could lead to accusations that solar PV doesn't justify itself in the same way that German wind turbines are accused of being cost effective but bit energy effective) |
Efficiency per m2 does not matter. You dont buy by the m2 you buy by the watt. As long as you have the space to fit it its not an issue if your 1kwp array is 8m2 or even 20m2 (well apart from the cost of the fixing kit & time to fit will be bigger).
No its not night time for 50% of the time. Well not for PV any way. Its much longer. My best ever day had the equivalent of just over 5 hours of full production. I also have plenty of days that have little or no production.
System efficiency will be much more than 50% & 33w per m2. My system is rated at 121watts out per m2. We do actually see that level too not all the time but often enough.
But again its not important as you buy by the watt not area.
Use your numbers to see what an array will produce per year. I tried roughly & got a measly 125kwh per 1kwp array size. That is almost out to a factor of 10.
Have decided to hold offon the project - I cant afford to do the pitched roof at the mo (but it does need done in the next year or so, as will be time to renew flat roof covering anyway).
Ive never really accepted that solar electric is 'there' yet, due mainly to all the concversations and info on here and in magazines.
I'd rather wait to get solar thermal.
Waiting till next year for PV could be a big mistake. The rates will be going down. Once you are on a rate it stays the same (plus inflation increases) for the term of the FITs.
Waiting for the RHI is very sensible. It is still all pie in the sky.
Nick, if thats a link to the same thing some one linked to a few days ago then yes he has hit it square on.
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