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.
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:
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).
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.
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.
This doesn't add up. The amount of energy available per square meter 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...
An air heater?
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.
IMM, Just a quickie, because this is turning into one of your religious-type arguments, but
a: the sun tracker you mention is in NEVADA, for Pete's sake, not NEASDEN! We *started* by discussing domestic scale arrangements in this country. It needs DIRECT sunlight to work, hence their suggestion of it being useful in the desert. All large reflector-arrays I've seen to date have been in similar situations. It is very hard to focus a completely diffuse source, which is what the sun is throughout most of the year in this country. Even on only partly cloudy days you begin to reduce efficiency dramatically. There are other technologies which are much more suited to Britain's climate.
b: it is on a very large scale (25kW), when compared with domestic use (and what kind of journalistic rubbish is "25kW per second"?)
c: it involves high pressure hot gasses and doesn't look like something which could be scaled down any time soon.
d: I'm not convinced that an unsealed Stirling engine is really a Stirling engine. It sounds more like a conventional high pressure steam engine. Incidentally, are we actually talking about steam pressure cylinders, or steam turbines when referring to "normal" steam engines?
e: when you say that "virtually all" Stirlings have a piston in cylinder arrangement, I presume you are referring to an "expansion" cylinder somehow attached to the main cylinder which contains the bulk of the working fluid and the displacement piston? This is an interesting compromise and the calculations as to dimensions of this extra cylinder will have to be made very carefully in order to allow maximum heating and cooling of the working fluid which is common to it and the main cylinder.
f: are you aware that the fuel consumption and emmissions figures for Renault's dCi Diesel High Pressure Common Rail engines actually *better* those of Toyota's so-called "green" hybrid car? Ok, it was in a Renault brochure I read this, but it's scary. (We have a large - 1.9l - Renault dCi and it's fantastic. Last time I did the 400 mile round trip to see the parents I averaged 61mpg, and I wasn't trying *very* hard to be economical. The 1.9l dCi Scenic out-accellerates our 1.6l 16V Laguna too).
That was just one example, others are under R&D. The same sun actually shines in England too.
There is direct sunlight in England too.
It will point "exactly to where it should be at that particular time and date.
Yes and that is why the hybrids have never caught on in Europe. But of course there is a catch. Diesel produces particulates (soot) which is cacogenic and blackens building. Horrible stuff, and diesel engines pollute the environment in the excessive noise they produce. Nasty engines. Best avoided, and I have had two turbo diesels.
I have had one Renault in my life and hated it. Poorly made and rattly.
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.
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)...
Service intervals on our Diesel are *exactly* the same as on the petrol versions of the car: 18,000 miles or two years. Free "safety check" every year (so you don't miss MOT tests). The previous generation of engines had 12,000 miles petrol, 10,000 miles Diesel. Hardly a difference.
And, ok, nearly all Diesels these days have Turbos, but nearly all petrols these days have highly complex 16-valve systems with variable valve timing, engine management units and *spit* electrics to go wrong.
Scenic is rather more than a "taller" Megane. Define "dog". What don't you like about it?
About £35. See redrok.com. Payback is quite practical with such a tracker.
IMM replied:
packaged
£35 not cheap enough then?
Nick wrote:
price
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.
Bigwall>What I have noticed with the wind power suggestion, is people are working on
nothing to
Planning permission. You'd have no chance.
From: IMM ( snipped-for-privacy@easy.com) too many errors to reply to.
Not so long ago all diesels had 6,000 mile services when petrol was 9,000 plus. Things have improved.
There are many petrol engines that are quite simple, with 2 valves per cylinder and common fuel injection system. Diesel injection is now electronic/mechanical. Diesel are more complicated with a heavy bill if a turbo packs up.
Cheap nasty, breaks down a lot, lousy styling, lousy interior etc. Best avoided. Renault used to have advanced styling, now they make blurb boxes that looks the same as the next large auto makers blurb box.
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.
Lets have a think. Oil heating costs about 1.4 pence / kwh.
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.
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.
I havent done the maths here, but ave of 1/8 kW per sqm sounds much > too low.
Yes please.
It was making a nasty whining noise, obviously too much back pressure, I have a 1/4 hp one on order though.
I did another calc on the uncovered collector at the weekend. Now that 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?
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