Re: Solar space heating idea

Ah Ha !! Very Interesting Nick. The only thing with this is, will it work in a British winter ? This system would be great for hot air heating during the winter months, but do we get enough sunny days to make it viable ?

Me thinks me needs more research into this subject.

I may be back.

Reply to
BigWallop
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Well, in the link I posted the guy's system produces an average of

0.25 kw from a collector of size 2.8 sqm on an "overcast winters day". I don't know where he lives but it's snowing there!

I guess the main benefit will be in spring and autumn where the central heating will hopefully not come on much at all. Come the middle of winter, I'm sure it will be on a lot.

However, I was looking at my site this morning and realised that the garage roof might get shaded in the winter when the sun is low. It gets sun all day in the summer...

Here is a photo of the site (looking east so the garage is north of the house):

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I might have to rethink :-(

If it's a non starter, I'll see if I can persuade the wife to have removable panels on the ground at the front of the house...

Nick

Reply to
NickW

It looks loverly Sir, and I am now jealous. I live in an Edinburgh Tenement, but have to say that these houses are very cosy all year round. Not to hot in the summer and well insulated for the winter months.

I see what you mean about the garage being in the shade, and the picture was taken on quite a clear day which is ideal for your idea. So it may have to be portable panels out the back door.

What the neighbours and I have done here, is put a small wind generator on the roof, shhh, don't tell anyone 'cause it needs planning permission, which runs the door entry system and a light at the bottom of the stairs, from a rechargeable car battery system, that's how small it is. If we'd gone down the, so called, correct route, we'd have had a big electric meter and fuse blocks right at the bottom of the stairs or someone running cables through the common stair to one of the houses, and no one here wanted that. So the pyro' runs down the outside of the building and up to the front door, and it only cost me a day a year to check that it's all OK. Which it has been now since 19 dot and a bit.

Have you thought about going with a wind turbine ? Nothing to huge, just something that would give enough power to run your hot water tank and maybe a few outside lights at night from a battery storage system. It would help cut at least something off the bills a bit. In the picture it looks like the perfect spot for a small turbine not to far away from the back of the house, and disguised by the trees in the background.

Reply to
BigWallop

Current prices mean that small wind turbines are not economically viable. I'm not taling about a tiny thing that generates a few W, I'm talking about a big one which produces enough power to power a hot water tank.

Reply to
Grunff

Hi

Good one.

Regards, NT

Reply to
N. Thornton

I have considered a wind turbine... there are plans for DIY ones which don't cost too much. I have also been thinking about direct drive heat producing ones, ie: convert the kinetic energy into heat using a heat pump or stirling engine rather than into electricity first. This would remove the efficiency loss of converting to electricity and also produce something like 2-3 times more heat that the kinetic energy taken to drive it.

Solar thermal however, I think should be exploited first as it seems to yield the big numbers for something as simple as heating air. I worked out at the weekend that I have enough space for an 8 square meter freestanding collector on the south side of my house. Hopefully enough to average 1.6kw during daylight hours during the winter.

BTW: you can get sizeable grants for solar/wind/hydro projects (yes, even on a domestic scale). The only downside is that you must have an approved system (not homemade!) and it must be installed by an approved installer who will cheerfully jack up his labour cost to eat up your grant. I know this because I got a quote to have solar matting installed for my pool and the guy wanted to charge me 1000 quid for a :-(

Regards

Nick.

Reply to
NickW

Last time I did calcs for wind to heat the figures were incredibly bad. Since solar thermal can actually pay its way and more, it is the clear choice. There is also the fact that its silent, safe, virtually maintenance free, and can go most places. OTOH wind turbines rarely get planning.

Regards, NT

Reply to
N. Thornton

Air heaters are very efficient. have one on the back wall of a conservatory with the heat rising into the house, or loft and ducted down.

What is very efficient and economical, is a sun tracker focusing the sun via lenses onto a heat exchanger and producing very hot water. These can also produce steam and run a small steam or Stirling engine/generator. Even in cloudy weather very hot useful water can be produced. Steam or Stirling engines can be very small for high large torque. There is research in the USA on sun trackers/heat generators for CHP applications, or cogen as the Yanks say, and it appears more cost effective and efficient than most other methods: PV cells, flat plate collectors, etc.

Reply to
IMM

Can I ask a couple of questions?

1: If suntrackers are so efficient, why is it that the only one at the Centre for Alternative Technology is about 25 years old? Why haven't they installed more? Is it perhaps that the reflectors are a waste of time?

2: Are you *sure* Stirling engines have high torque? The ones I've seen certainly don't - they are very efficient, but only when operating high speed/low torque.

Just interested :-)

Hwyl!

M.

Reply to
Martin Angove

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

Reply to
N. Thornton

Lots have happened in 25 years. Do a Goggle on sun trackers. There are some off the shelf versions from the USA.

Specifically steam engines have high torque at low speeds. Steam trucks, which were built up to WW2, never had gear boxes the torque was so high. The highest torque is at stall speed. A team engines does not idle; the old steam trucks just opened up the steam and off she went at an amazing speed for the time. The problem with steam engines is condensing the steam back to water, otherwise the steam has to be released and water used at high rates. Stirling's do not have that problem. So using steam and having a guaranteed cool condenser, such as a large thermal store, may be feasible. Seam engines are used in ships still with a guaranteed endless supply of cool sea water to guarantee the steam turns back to water. The most efficient steam engines are the marine variety , which have been made far more efficient over the past 15 years or so. The cooling problem applies also to Stirling's, which are used in French and Swedish submarines also using cold seas water to cool. The engines are super quiet and virtually vibration free.

R&D using sun trackers using Stirling's and steam engines, and focusing on a metal water filled sphere to produce steam/hot water is going on. many keen armatures using their own home built equipment have reported excellent results.

Reply to
IMM

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.

Reply to
IMM

[...]

The point I think I was making was that they tend to get the best/most efficient stuff at CAT eventually, and will try (almost) anything in the meantime. Unless something's happened since I was last there, the only sun tracker is this 25 year old thing. If they were so good (in this climate perhaps) then *surely* CAT would have installed a couple more up to date versions? I can understand how they might fractionally increase the efficiency of a system where direct sunlight is the norm, but where diffuse light is the norm (i.e. here) where do you aim your device? On top of that you've the extra mechanicals to maintain, and the extra energy required to cause the thing to track.

[snip the rest which interested parties have probably already read]

I understand that steam engines have high torque - but as far as I understand it, a Stirling engine is *not* a steam engine, though I suppose steam could be used as the heat source.

Unlike a steam engine, the cylinder is sealed.

Unlike a steam engine, the "working piston" isn't actually *in* the cylinder, it is merely attached to it. In models it is often a sheet of rubber, though I see no reason why a piston shouldn't be used.

Unlike a (modern) steam engine, the working fluid in the cylinder (air) must be heated *and* cooled in order to complete one full cycle.

Can you post me some web references to the Stirling steam engine? I'm very interested in the technology since coming across that boiler which uses a Stirling engine on the exhaust to generate electricity. One thing I don't quite understand about that thing though is whether it'd actually get much use in a modern highly insulated house :-)

Hwyl!

M.

Reply to
Martin Angove

Trackers have been fixed on sphere that contain the water. they swivel around the ball while focusing the intense suns rays.

I never actually said a Stirling was steam engine. It is a "heat" engine. There are many variations of the Stirling sing differeing gasses to expand. It has in common with "piston" steam engine: eternal combustion (very eco) and a heat and cooling source.

I most yes. the early versions (1830ish) were not. There is also a rotary (wankle type) of Stirling engine.

Virtually all usable Stirling's have a piston in cylinder arrangement.

The working fluid can be air, but the more efficient versions uses various more efficient gasses.

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I'm very interested in the technology since

Not available yet.

The unit actually has a burner playing on the Stirling, which has a free wheeling piston with no crank, being the only moving part. The gasses pass through a heat exchanger, Another supplementary burner is used to boost to hot water output.

On existing poorly insulated homes the Stirling boiler is feasible. Any excess electricity produced passes to the grid via a two-way meter.

Reply to
IMM

British Gas to launch individual CHP boiler for homes

British Gas has announced that it is developing a household boiler that generates both heat and electricity, which will increase energy efficiency and cut costs for customers, allowing them to sell excess electricity back to the Grid.

The new combined heat and power (CHP) boilers, developed by MicroGen Energy, a subsidiary of BG Group plc, will result in increased energy efficiency, says the company. Normally, only 37% of electricity that is generated at a power station and transferred to customers via the grid is used. However, the new boilers will have an efficiency of around 90% or more, cutting fossil fuel use and reducing the need for gas imports, a British Gas spokesperson told edie. One million of the boilers would be the equivalent to Sizewell B.

The system uses a Stirling engine, invented by the Reverend Robert Sterling in 1816. The pistons are the only moving parts of the engine, which uses gas bearings to minimise wear. The engine is a sealed unit with no requirement for regular servicing or maintenance, says MicroGen. The Stirling engine generates both heat and electricity and additional heat needs are met by a supplementary burner.

The boilers will produce a baseload of 1.1kW, which is sufficient to run most domestic appliances during the day, and any excess is then sold back to the Grid. At times of peak electricity use, the household will have to buy extra electricity, and will receive a net electricity bill at the end of the quarter.

It is also estimated that they will reduce an average household electricity bill by around 25%, and will cut a home?s annual carbon dioxide emissions by about 1.5 tonnes and nitrous oxides emissions by an average of 40%.

?This could herald the biggest change in British homes since the introduction of gas central heating in the 1960s and 70s,? said John Shears, Commercial Director of British Gas. According to Steven Evans, Chief Executive Officer of MicrGen, the prospect of the new technology is already arousing a great deal of interest in the market.

An added benefit, says British Gas, will be for homeowners subject to power cuts, as they will guarantee continued heat and electricity.

The CHP boilers are currently undergoing tests by British Gas, and the first boilers will be available commercially by late 2004/early 2005, said the British Gas spokesperson.

Reply to
IMM

Some info: Associated Press

1/13/2003 02:15 pm

A solar power demonstration program is making UNLV a hot spot for research into tapping the sun in the southern Nevada desert as an alternative for the nation's energy needs.

"UNLV is quickly becoming one of the leading solar researchers in the country,"said Mary Jane Hale, a senior engineer for the National Renewable Energy Lab in Golden, Colo."And then you have this great solar resource there in southern Nevada."

UNLV researchers are trying to find an affordable way to generate energy using the sun's power, and a parabolic dish array at the edge of the campus helps to spotlight the program.

Two mirrored dishes track the sun, focusing light energy on a tube filled with hydrogen gas that heats and drives the pistons of a Stirling engine.

The unit has been in operation for about a year. It produces 25 kilowatts of power, or enough power for 250 100-watt lightbulbs, every second.

If testing is successful, the technology might justify the cost of putting solar collectors on Bureau of Land Management property in the desert.

Sen. Harry Reid, D-Nev., helped secure $1 million in federal funds in 2002 for the UNLV research program. The University of Nevada, Reno got $1 million of research money for geothermal energy.

However, the technology is expensive, and the nation has resisted alternatives to fossil fuels.

Other solar technologies also are being tested, including a Duke Energy project in Boulder City that uses oil, not hydrogen, to power the engine.

"What we have is a (presidential) administration right now that's not really high on this kind of stuff,"said Bob Boehm, director of UNLV's Center for Energy Research."They are high on oil."

The dishes soak up 30 percent of the sun's rays _ three times as much as conventional solar panels. It would cost the average user triple the price of traditional power sources, according to NREL officials.

But with continued research and use of the technology, costs are expected to go down, officials said.

UNLV's renewable energy program is also training experts in a field where there aren't many experts to go around, Boehm said.

The hope is that UNLV's projects will help make the state a Mecca not only for the collection of energy but also the manufacturing of energy collectors, Boehm said.

"It's not unreasonable that this could lead to some sort of industry here,"he said."We are in a prime location for using the sun and manufacturing these types of things."

Reply to
IMM

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:

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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.

Reply to
NickW

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.

Reply to
BigWallop

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.

Reply to
IMM

In article , IMM writes

Correction...

The packaged solutions will come about when the price of fossil fuels comes to a point when these systems will seem cheap...

Reply to
tony sayer

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