Re: Solar space heating idea

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blurb box' as I shall now refer to it.
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I like that approach too, tho its not problem free. I would go flat plates /air first.

They can but its very impractical and very inefficient.

Partly cloudy yes, but qith full cloud youve got no way to concentrate the diffuse sunlight.

Steam is the true master of inefficiency and bulk.

I'd be interested to see your refs then, as figures I've always seen or calculated would suggest its a real no-no.
There are also additional problems with any steam setup due to legal issues with the high pressure boiler. Plus PV and hot air are far more reliable.
Regards, NT
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The more sun in a brighter climate the better of course, but lenses have been used that produce enough heat to make them more than feasible.

That is so, but useful heat in part cloud conditions.

Not these days. One double acting piston, the equivalent of a one stroke, which is the equivalent of a V8 is very efficient, and small. Highly efficient flash boilers containing no water, just water turned to steam rather like a powerful instantaneous gas water heater, and burners have come a along way too to improve efficiency.

No boiler with stored water required. Instant flash boilers don't have very high pressures. The technology has been around for 300 years. An internal combustion engines has a series of explosions ignited by highly volatile fuel (petrol), which is far more dangerous than a steam engine. As in the internal combustion engines, electronics can make a steamer far more efficient too.

PV? With all those inverters and batteries. You are joking of course? Hot air is more reliable. A sun tracker focusing to make hot water is also very reliable.
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Hi tech stuff is all very nice but have you checked on the price of a suntracker lately? These types of system often don't pay you back for maybe 20 years or so.
There's a lot that can be done with simple materials. You might achieve a collector efficiency of only 60% compared to maybe 80% of a vacuum tube collector or a suntracker but if it costs 1/10th the price then it could be worth it.
This is a good link:
http://www.ece.vill.edu/~nick /
The solar closet is a simple and cheap 'heat battery' to buffer the avialable solar energy so it last overnight and maybe even over several overcast days.
Having said all this, I've done some checking and active solar space heating is considered not to be viable in the UK since it is usually overcast in winter time... ah well.
Nick.
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Now that's why I'd stick to a wind power system. It's the only thing we can sort of guarantee to get more of.
What I have noticed with the wind power suggestion, is people are working on the assumption of just one turbine and blade system, yet there's nothing to stop the use of three or four smaller turbines being used to power the system.
And the price of DC to AC converters is reasonable for use of stored power. A power store today can be much smaller as well, due to current battery technology, so it can be put into the equation on any of the chosen systems. I can even charge my car battery from a reasonably priced solar panel on the dashboard of the car.
But, I'll stick to the wind power for now.
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R&D is still ongoing and the prices will drop accordingly when packaged solutions are available.

In this case use more collectors.

Sun trackers get 3 times the suns energy than flat plate collectors. So much so they are powering Stirling engines.

You will be surprised at the amount of winter sun the UK gets. It varies from area to area too: Scotland is different to Cornwall.
Active solar in the UK is viable. The solar closet can be an air heater inside a conservatory facing south.
The best setup in the UK is firstly superinsulation and elimination of cold bridges. This is essential. Porches on all outside doors acting as air locks should also be fitted. A whole south facing roof can be made into a solar collector storing heat in a large thermal store. The large surface area means it will efficient enough to gather enough hot water. Then use "very low" temperature underfloor heating. The reason for low temp is that in winter the store may not have water stored at a high temp, but hot enough for low temp underfloor heating. Also have passive solar aspects of windows, correctly sized roof overhangs for summer shading, deciduous trees, etc.
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writes

Correction...
The packaged solutions will come about when the price of fossil fuels comes to a point when these systems will seem cheap...
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There's a limit to how much cheaper it can get, it'll always be a complex motorised thing.

Indeed. This is my preferred this idea.

is the same for any collector. At the height of summer, this is about 800-1000W per square meter. A suntracker maintains alignment with sun so it's exposed area does not diminish as the sun moves. It might also be 10-20% more efficient than the cruder panels but this doesn't add up to 3 x difference...

A solar closet has a high thermal mass and high insulation. It's basically a cube shaped room. A 1 meter cube would have 10cm of (say) rockwool insulation, the rest of the space would be occupied by water filled containers which can hold a lot of heat energy. A conservatory is filled with air and even good double glazing is not a great insulator.
Nick
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It does. It magnifies the suns rays.

The solar closet uses an air heater to circulate hot air through the closet, which in turn heat the water (thermal mass) stored in large glass jars. When the house requires heat a fan runs cool air from the house through the closet and over the hot glass jars and back into the house heated.
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What is your air heater you mentioned by the way? A commercially produced one or a DIY one? I may yet look into an air heater because I reckon I can make an 8 square meter one for under 200 pounds (not including the fan - I have a spare extractor fan about 20cm diam)...
Nick
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Look at the solar closet web page. The heat generator is an air heater. It heats air.
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Re efficient steam engines:
Well, I'd be happier to trust your word on this if you could show us a ref. What you say certainly sounds good, but I would like to see it backed up.

Here you're comparing apples and oranges. Both PV and steam will produce leccy when the sun shines, and both will need either grid tie or batteries and invertor. The steamer is comparable to the PV panels only, not the PV + batts + invertors. Comparing a steam engine with PV panels, the PVs are clearly much more reliable. The externals will be similar for both forms of generator.

I think its the most reliable of all, and about the best payer too.

Fairly, but not as good as flat panel collectors. Mirror deterioration and wind damage are the major bugbears.
It was mentioned that CAT are lacking in tracking, and that if it were a good idea they'd have more of them. I'd say fixed mirrors are a good addition to PV, specifically angled to increase the light away from noon, ie when the light level falls, and specifically using greased silver mylar mirrors, which are very cheap. But AFAIK CAT doesnt have those either. CAT doesnt have everything.
Regards, NT
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wrote

A few years back some car makers were looking at steam engines in view of proposed increased emissions; no doubt their lawyers and lobbying prevented the increase. The Stirling engine link I gave mentions the vast improvements in the burners (from CH boilers mainly) giving very low emissions. As a steam engine is external combustion also, the same applies.
There is no reason not to use Stirling or steam engines in slow moving town and city utility vehicles like: buses, delivery trucks used by utility companies, etc.
A Google will bring up lots on Stirling and steam engines. Lots of work is being done on Stirling engines, with many models readily for sale.
Stirling and steam engines cannot give instant power, giving quick acceleration, as the internal combustion engines can. This can be overcome by having a Stirling/electric or air motor hybrid. The electric or air motor is only used to assist in acceleration above a certain rate. Hybrid technology is here with Honda, Toyota and now Ford.
The Stirling is imminent to use in vehicles and Combined Heat and Power (CHP). Many points keep it from vehicle use: the industry is geared up for the internal combustion engines, no energy crisis driving up fuel costs (AMC made a Stirling engine car in the 1970s and were about to produce it when the fuel crisis waned) and exhaust emissions have not yet been lowered enough to preclude the internal combustion engine.

Some people want energy autonomous homes demanding little from the environment. The Vales attempted this with partial success. The problem is generating enough electricity and storing it. It would be simpler to:
1. Construct a house that requires minimum energy demands. Superinsulate it with no thermal bridges, triple glazing and make it air tight, then concentrate on producing and storing solar hot water for DHW and CH (hopefully heating needs will be zero to minimal).
2. Have minimal electrical use by using electrical appliances that consume as little power as possible, they are available, and use cheaper, and cleaner, to run gas appliances where possible (gas ovens and tumble dryers instead of electric, washing machines that take in hot water rather than heat it itself, and the likes).
This is a far more cost effective approach for a new build, or full renovation than trying to generate electricity.
The solar closets et al, are good retrofits to existing homes with some added insulation points, as: triple glazing or double with low "e" glass, make the house as air tight as possible, draught proof the windows and doors, put over 1 foot insulation in the loft, install porches on outside doors, etc.
The more a house is insulated and air-tight the less you need to generate heat.
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open the windows, or rely on the heat recovery system, which is virtually mandatory in a air tight house.
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From: NickW ( snipped-for-privacy@bt.com)

About 35. See redrok.com. Payback is quite practical with such a tracker.
IMM replied:

35 not cheap enough then?
Nick wrote:

Exactly. You can't count on getting 60% off a flat plate, but then you dont need to. Its more liekly to drop to half that when the water's hot.

There are a lot of different technologies, a lot of different designs with each one, and a lot of differnet takes on them all. I definnitely wouldn't assume active solar heat is no-go - tho most systems are.
Bigwallop wrote:

system.
Planning permission. You'd have no chance.
From: IMM ( snipped-for-privacy@easy.com) too many errors to reply to.
Regards, NT
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What errors might these be?
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That's a good website. Although making it windproof would be fun. Maybe a mylar lined parabolic mirror directing extra sun into the house would be worthwhile. Directing extra light into the bathroom which is on the north side of the hosue would be good.

If my 8sqm freestanding DIY collector cost me 200 quid, it would have to produce a total of 14284 kw to pay me back. If it averages 1kw from autumn through to spring, an average of 7 hours a day, call it 250 days... that's 1750 kwh a year. That's 8 years!! Oh well, I'd just have to be thinking of the greenhouse gasses saved.
As an aside - remember my solar coil for the pool? I was forced to do as you suggested and divide it into seperate circuits because the bearings in my pump are starting to go, it sounds very noisy now. I bought 6 T-pieces and made it into 4 seperate circuits and now the water gushes out the other end instead of trickling. I shall replace the pump with a less powerful one - a 1/4 horsepower one to save leccy.
I've also bought some polythene, 36sqm for 15 quid, trouble is it's not as clear as I hoped and I may not use it, hmmm.
Cheers
Nick
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Hi

Yup. You would have glare to deal with: you'd need to direct the light up towards the ceiling. And I'd be a bit cautious about focussing the sun into one small spot, a deliberately not-really-parabola might be preferable. But I think this is basically a good way to go, you get heat and light very cheaply.
I did something similar using a flat plate mirror, just mounted it apx horizontal under the window on the outside. Doubled the light level in the room. Direct sun mainly hits carpet and furnishings, whereas reflected sun mainly hits the white ceiling, so such large light increases are quite practical. Plus you get the birds landing on it, and the cats sunbathing on it.

Are you sure? I dont know, its just that gas is more than that.

I havent done the maths here, but ave of 1/8 kW per sqm sounds much too low. I dont know what kind of collector youre considering, all I can say is big trackers can pay back according to previous calcs. But it does depend how you design them. Somewhere I've got detailed figures on this one: want me to mail them? Might be of interest.

Right. I'd be tempted to just run it slower, by using a series impedance or transformer. Sounds pretty lousy tho if its crapping out already.
Now if you turn your coil into 112 parallelled one foot long sections, you'd only need 5w of pumping :)

I reckon if you get more than 50% through it should gain you. Youre really losing a lot with an open collector. It wont matter that theres light scattering.
Wish I had the time to actually do what you are.
Regards, NT
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Not certain but FWIW, this is my source: http://www.chic-info.org.uk/electric.html

I have a 1/4 hp one on order though.

the coil is divided into 4 circuits, the flow rate is much higher but the temp gain seems the same. Perhaps it's just better conditions now (mid summer, high noon, no cloud at all). I got 10kw! If there is 800W /sqm available then from my 25sqm collector, that's an efficiency of 50%. Given this, do you think the polythene will still benefit?
Nick
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snipped-for-privacy@bt.com (NickW) wrote in message

I took a quick look, and the prices there are a fair bit off what we pay here. I'd check out your leccy and gas bills, and factor in efficiency for each heating type. Roughly speaking leccy = 100%, gas 80% efficient.

Will do.

Sounds like that one was rock bottom stuff. Have you got a filter on it btw? I just wonder if there might be something in the pump.
You may even find 1/4hp to be more than you need, in which case you can cut energy use/noise/increase life by reducing its run speed. Whats your temp rise with the 1hp pump, with the present plumbing setup and fast flow rate? It should be poss to make rough calcs from there, if youre interested in slowing it down.

Yes, definitely. Youre losing loads as it is. I'm surprised to see you getting 50% off such a collector though, I would have expected a fair bit less. Your low water output temp will be helping a lot, but plastic pipes and no cover would generally hit efficiency quite hard.
Well I'd be curious to see what happens if you ever space the pipes out and put silvered mylar underneath, and polythene on top. I reckon you'd seriously cook.
Sounds like doing the same thing for DHW has to be on the cards, thats some heat output! If you ever do I'd efficientise it as much as poss though, since water output temp would have to be high, so all those extra tweaks would be much more important.
Regards, NT
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