One of these
big 1.5 metre babies will happily produce 60-75 watts an hour during sunshine
www.barden-uk.com/solara-rigid-glass-solar-panels....l
Inverter here
www.barden-uk.com/studer-xpc-inverter-charger-comb...l
You will need to be able to isolate out the fan system from the mains with some kind of switching gear (manual will do) when you shut up shop. (ie switch mains off , then switch in your solar power system)
Bit of a job getting 1.5 metres of glass solar panel to france tho!
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< Ulla>
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No problem with 1.5m length on the roof bars. I might even plug it in and save on diesel on the way down - LOL.
Any idea of the power calculations though ? I presume a watt is a watt is a watt whatever the voltage. How might you determine / calculate losses with 12v lead acid batteries, inverters etc.
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a watt is a watt, but the amps (current) is not
at low voltages (ie mains or less) our only enemy for losses and heat dispersal is amps
Watts=Volts x amps
so your 43 watts of mains power = .2 amps
and your same 43 watts via a 12v battery/inverter is 4.0 amps on the battery side
(all approx)
either is very small beer, so for this exercise losses are not worth bothering about you only need to worry about watts, and both that panel and inverter have watts to spare
Now dont forget that your battery is only being charged during daylight, and your fans are drawing 24 hours.
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< Ulla>
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There's a couple of other issues to consider here.
The fans will have a high current draw until they start moving.
The inverter will have a maximum output current and if you try and draw more than that then it may, depending on how it's designed, turn off the output.
So if the fans want to draw more current when you turn on the inverter than the inverter can supply then they won't start.
As far as how much power you get out of a solar panel, be very aware that its spec'd in bright sunshine, which happens rarely.
The inverter efficiency will be spec'd on its data sheet. You need to read and understand the data sheets of all that you're looking at.
Have you considered using a 12V fan rather than a mains powered one?
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I read often, only post occasionally
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The inverter is 1100 watts, the panel is rated at 125 watts peak, a 12v car battery can produce heaps of watts at surge (cranking currents are massive) so at least so we have ample "surge" here, but you are right to mention it.
mind this lot aint cheap. the powerful panel is 600 quid and the inverter 800 quid. one of the cheap car inverters (a 600 watt one for 35 quid) will probably do the job. Beauty of those is that they cut out if the volts full, but I dont know if they need to be manually reset when the volts climbs again.
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< Ulla>
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Thanks so far - this is beginning to look like it might be a goer. A 12v fan is not on my list at present because the mains set-up exists and I'm hoping a simple (??) isolater / transfer switch will do. But then, a completely independent set up with new vents (so now 2 per room) and a new hole in the roof might be OK but all that will come at a cost too. Maybe instead I could just keep the vents / ducting etc. and just change the motor so it's always run on 12v ???
As I said before, I don't know a lot, but surely the current draw on a measly little fan won't be more than say a TV or laptop which these inverters are supposed to be capable of running.
As long as the system was self-starting it wouldn't matter if it didn't run from time to time (e.g. at night or when very cloudy).
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Ouch ! - £700 all-in plus a DIY fit. It seems the panel is the costly bit, but if the "free supply" could be hijacked for other uses it still might be a possibility.
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I think solar panels are cheaper in France - try to find a french supplier. You may even benefit from the tax rebate on renewable energy installs.
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You might need some form of regulator between the solar panel and whatever device you put downstrem of it - in sunlight, solar cells tend to behave as near ideal current sources.
This means that they will try their best to drive that current through whatever you connect - if that something charges up, and its resistance builds, the solar panel can build up to damagingly high voltages - or it might boil your battery dry!
I think it's good to build in some headroom in the solar panel capacity - dull days, dirt building up on the cover glass, etc.
But, this also means that the regulator design must also cope with a worst case of a really sunny day, spotless clean cover glass, and a fully charged battery - i.e., with nowhere else for the current to go than being dissipated in the regulator.
Number_Cruncher
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How do all those costs compare with just leaving the mains on and disconnecting everything apart from the fan?
I take it you are meaning a wall mounted xpelair type fan? There would be no point in having a ceiling or floor mounted fan in an empty house if no air was coming in from outside?
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2007 Seat Altea XL 2.0 TDI (140) Stylance
2005 Skoda Fabia vrS
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How do all those costs compare with just leaving the mains on and disconnecting everything apart from the fan?
Yes, whay not mains? Is it for financial or environmental reasons?
The solar panels will take many many years to pay for themselves financially and even longer in carbon terms.
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If the house is left empty for a number of months, its safer to turn off the mains. INdeed it might even be an insurance requirement.
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< Ulla>
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Honda recently announced a solar power initiative:
world.honda.com/news/2007/c070612HondaSoltec/
The RRP quoted on there for a 125W Honda panel equates to £271 inc tax (£257 excl) which compares to £680 on links above for the SM500S.
How you get them from Japan is another question - I can't find anyone importing them as yet. However, for £400 it might be worth jumping through a few hoops.
www.helpsavetheclimate.com/solar.html#a2 gives a solar insolation (sic) of about 1100kWh per annum where I live. At an efficiency of around 12.5%, these panels would generate 165kWh per annum = approx £13.75. so a 22 year payback at the suggested price plus VAT. Not quite there, but getting closer to being worthwhile as an alternative power source.
V
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>> so a 22 year payback at the suggested price plus VAT. >>
What about the carbon payback, it can be even longer.
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cheddar: "What about the carbon payback, it can be even longer."
What is a "carbon payback"? And what relevance does it have to the thread?
V
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I think he means the carbon footprint of making, packing, distributing and getting rid of them when they are dead.
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< Ulla>
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Thanks, AE, in that case, it's a pretty ill-though out statement, as twenty seconds of calculation will work out.
There's no way of accurately calculating the use of Carbon, but I'd suspect it's a damned sight less than 22 years. Over 22 years, my calculations have the things producing 3MWh (3000 kWh) of electricity.
Thus, unless they burn enough carbon to make 3MWh, it's going to be negative in terms of carbon.
Anyway, what that has to do with financial payback, I don't know. What I do know is that once it's cheap enough, solar power will overtake any other form of power. Simple economics will stop people whingeing on about fashionable old carbon, because it'll be irrelevant.
V
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More info for those who might want to know:
It IS an insurance requirement, as is turning off the water supply and draining down all the water. The fairly commonly used french VMC system is not an expelair fan in a wall, it comprises a large plastic box in the loft/roof space with a fan in it and a 150mm exhaust port leading to the open air through the roof. The box has 4 input ports each 80mm diameter and one 100mm with ducting leading from the appropriate places. In theory the 100mm one comes from the kitchen, 80mm from a bathroom/wc and the others from any other rooms you fancy. This type of system is usually kept running 24/7. You can buy more fancy models with more power for use with more rooms, but ours is only for a WC, a bathroom and a WC/shower room. By leaving doors open when we're away, continous running of the system should leave the house less damp and musty when we arrive. We've got window vents in the glass behind the closed wooden shutters, but the 700mm+ stone walls with no DPC still do a very good job of keeping the place damp-ish, but after a few days of normal use and the log fire roaring away, things settle down nicely and the place feels dry. I want that dry feeling in the house the minute I unlock the door after a couple of months away.
But do I want to pay £700 for it?
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Despite the American bias, this site gives some good info;
www.kyocerasolar.com/solar/index.html
What they refer to as a controller, is what I was describing as a regulator higher up this thread.
Number_Cruncher
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Can't you get a local to come in and warm things up for you before your arrival?
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I read often, only post occasionally
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Dont forget that you need either a "leisure or traction" type battery (deep discharge) as opposed to a "starter" battery,
Billy
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"Can't you get a local to come in and warm things up for you before your arrival?" said spikeyhead.
Well of course I could, but I like to be independent if possible and this ventilation thing is really a 24/7 business. At first, before we made any attempts to ventilate we had green mould on the surface of the woodwork. I guess it may have been preservative leeching out or maybe just green bacteria. Whatever - I don't want to see or smell it again.
It ain't like the holiday homes abroad TV shows I assure you.
In summary, this solar power idea looked like a reasonable thing to research. I haven't even taken a good look at web sites yet. But what with £600 panels, a mains isolator, a regulater, inverter and fancy battery leading up to £750 - £1000 all-in plus DIY sourcing and fitting I'm not so sure. It certainly shows that living off the grid isn't the easy option.
My next question will be about a battery powered electronic timer plant irrigation system from a very large water butt collecting water from a huge barn roof - but I'll leave that one for later.
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My next question
Hello Dulwich Estate. Have you thought about a passive wind driven fan extractor, such as those you see on top of enclosed vans? You could have a wind driven positive pressure fan at the base of the property to force ventilate the house, and another suction extractor fan in the roof space to extract the stale air.
Re payback times: Vin said " these panels would generate 165kWh per annum = approx £13.75. so a 22 year payback at the suggested price plus VAT. "
That is presumably based on a simple division, and is OK for a quick guestimate. Full financial payback calculations for such installations ought to include the real rate (that is price increase minus opportunity cost interest ) of inflation in the price of the fuel in France (electricity in this example), the cost of repairs and maintenace of the equipment.
Other complications are the cost of the capital, if the money has been borrowed compared to the opportunity cost of "investing" the money elsewhere on a different project. Taking account of all such other inputs in to the calculation, then unless energy costs increase at a large real rate, the payback time for this solar panel is going to very very long indeed.
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>>My next question will be about a battery powered electronic timer plant irrigation system =but I'll leave that one for later<<
You probably knew somebody would fall for it - didn't you! ;-)
matbe you need something along these lines, depending how many plants you have?
tinyurl.com/27rgnq
billy
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"Have you thought about a passive wind driven fan extractor, such as those you see on top of enclosed vans? You could have a wind driven positive pressure fan at the base of the property to force ventilate the house, and another suction extractor fan in the roof space to extract the stale air."
Not yet jbif. My first thought was just to CHEAPLY adapt what's there already.
But I now need to go away and have a lie down after which a long ponder about all the suggestions is required ! I'm even looking at those small solar powered fans used in boats but they're probably too small.
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