Have the tank above the collector and let gravity do the circulation for you, heating the entire tanks contents via a heat exchange coil.
Every roof top in Israel when I was there about 20 years ago had such a system and the hot water was very hot. OK that climate is a bit better for this than the UK or NZ but it can be done.
I think I perfer exterior reflectors. You get the gain but with no increase in losses. You can also switch the gain off in summer. And when the light is arranged to hit the ceiling it penetrates further into the room. And finally it costs peanuts.
NT
As the water would be up to temperature after a few hundred feet, a thicker tube might be more viable?
Anyway, what I used for my little test rig was the black corrugated plastic stuff they use here for running wiring, under plaster or rendering:
The stuff is about 20 Euro for 100 meters/330 feet, in 20 mm or thereabouts, cheap enough to play with. It is either polypropylene or polyethylene, which both don't glue well. This made getting a watertight connection difficult -- I used loads of hotmelt glue. Also I had an old aluminum beer barrel that was going to be added to make a very clever and cunning water heater that would have revolutionized the water heating world, but never got around to it...
Thomas Prufer
On Sep 14, 5:43=A0pm, Jules Richardson
There are going to be a few million unemployed before long...
MBQ
And all the fat kids who need some excercise.
MBQ
Start a solar PV business.
MBQ
Now where in the world did you get the idea that 'resourceful' and 'unemployed' could be equated?
Lets face it, its the big end of party time. No more sitting around doing f*ck all in council offices. So they will end up sitting around at home doing f*ck all and watching daytime TV.
At least that way they aren't SUCH a burden on the nation..
Yes, I did wonder whether some form of heat exchanger was viable; I've not looked into what sorts of inefficiencies are inherent in such things. The only issue with tank higher than collector is that it's logical to put the collector on the roof - which makes things a little ungainly for my workshop if the tank's perched up there too. The barn's not a problem though because the roof is enormous - it'd be easy to mount panels lower down on the roof with the tank indoors and high up inside (I could potentially feed the workshop from there I suppose, although it'd mean running the water for quite a while before anything hot came through.
cheers
Jules
I suppose the bit I don't know is how things behave while the water is flowing. I just did static tests. I should probably try to find a broken water heater to use for the holding tank - that's probably easy. Finding a pump* might be harder (I can't simply find an old washing machine pump, sadly - it's all top-loading washing machines with integral pumps over here)
Interesting! I can get 'normal' 1/2' tubing here reasonably cheap - I think it was around $30 (20 pounds-ish?) for 100'. Much cheaper than copper, anyway. Only real gotcha with the stuff is that I don't know if it's any good for drinking water - but that's probably a non-issue because I'm unlikely to want to drink hot water in the workshop :-)
For the tests I did, I could join it to 1/2" copper by heating the ends first, but I'd need a more robust joint for any kind of "real" solution. Maybe a slightly-larger bit of copper with a slit in it wrapped around the joint, then a jubilee clip over the top would do it (and something to flare the ends of the copper would be nice).
cheers
Jules
Does the double glazing add anything to the heat gain - or just result in less heat loss back outside again?
cheers
J.
the latter chiefly.
Or if they have thought about it, the contracts are already owned by a subsidiary company that they created just for the purpose!
Certainly Sir. Smelting the copper and zinc from ores to make electrodes is left as an exercise for the reader.
(and that plant won't stay living for long)
Rather than standard PV panels, I wonder if a focused system might be more DIY-amenable. Build a bunch of mirrors, and focus the sunlight onto a smaller number of commercial PVs (ensuring they won't get cooked, which could be tricky). Or focus onto a vessel to boil water in a steam turbine.
Anyone have any numbers as to viability?
Theo
The inverters used for these sort of back feeding applications have to be quite smart. Firstly they need to sync to the incoming mains frequency so as to generate power in a way that will actually be exportable, and secondly they have to make sure there is no possibility of back-feeding where the supply when it is actually off. Last thing some poor lineman needs is to be sticking wires back together while plugged into your PV array!
solar furnaces work allright. And teh servos to control the mirrors are not hard to obtain. But making a CHP style steam turbine is...ambitious.
The ultimate answer is that such things are more effectively done using big centralised plant.
Domestic power generation is almost a complete waste of time.
Possible things I have investigated that look vaguely proising inlude the following
- Domestic heat pumps. These are well able to make a significant difference. Even at 3:1 power figures, that puts electrical heating sub fuel heating cost wise. And assuming say 85% efficiency of a gas boiler and 65% efficiency of a CCGT set and 95% efficiency of a transmission system, will lead to a overall halving of carbon fuel burnt for heating.. and a *running* cost of about 60% of gas or oil boilers. Sadly te capital cost of a heat pump and a heating system designed to utilise lots of warm water rather than a little hot water, makes it devilishly expensive to install, but still, lots of it its DIY able.
- Simple heat bank to utilise off peak electricity and also possibly with aforesaid heat pump. A few cubic meters of hot water in an insulated tank is capable of holding an enormous amount of heat. Enough for several days if you can utilise *warm* as opposed to *hot* water.
Since off peak electricity is largely nuclear, with a bit of pretty efficient coal, this also makes for a better carbon footprint.
- massive bank of car batteries and a UPS. This can take off peak and store it for daytime use. Sadly it looks no better than cost neutral. But its worth thinking about at least for critical loads: split the wiring into battery backed ad non battery backed, so you can at least have lights, computers and a heating system running, and even keep fridges going when the lights go out as the wind drops and the windmills shut down.
But apart from these, and insulation, the key thing to realise, is that there is nothing electrical you can generate domestically that cant be better and more efficiently done at a power station.
That is less true of CHP on a metropolitan scale though. Combined waste burning, domestic or institutional hot water, and a bit of steam turbine on the back is actually the most successful 'renewable' energy there is.
Every hospital should have a crematorium and waste burning facility hooked up to their heating and electrical systems :-)
Fairly good I think at least while the delta T is high.
Take a look at the more modern integrated tank/panel units they are not as basic as the ones I linked to but would be harder to home brew.
... and every major data centre should have an associated block of flats to take the water from the aircon.
It's scary how much hot air we blow out of the back of our office, and not to the houses next door.
Andy
... and the kids will but upset by the big electrode-holes in their veggies :-)
I doubt they're cheap, though.
Yes, hard to find off-the-shelf turbine parts. Car/truck turbos seem to be about the only thing DIY-accessible that are capable of operating at high speed, and then there are probably issues with hooking an alternator to it all - and it all being exactly the right sort of size for the given application.
I think it depends on what your natural abundant resources are (wind, solar, tidal, local geology etc.) and what donor odds and ends you can readily get hold of to make it cost-effective. And then it's probably not going to scale, because of limited parts supply.
(it's a bit like the "run your diesel engine on veggie oil" thing I suppose - the game's changed a lot in the last decade)
Yes, certainly DIYable, although at least here a DIY approach won't net you any of the attractive rebates (and might raise questions with your house insurer).
Air-source no good here due to climate, ground-source is OK. Electricity around here is pretty cheap too, so electric-derived heat stacks up well against other sources such as propane. Wood's the real winner on a small scale, if you don't mind the effort.
Wonder how easy it is to recycle a bunch of dead car batteries into a few good ones? In most cases they seem to have a duff cell or two rather than the whole lot going bad. Never heard of anyone trying it, though.
Agreed - but I think there is some potential for 'cheaper', so long as you're running select devices and not trying to run the entire house that way. It's not rocket science, but nor is it trivial to do - and what works for one person won't necessarily work for the next.
Been reading a lot about wood gasifiers recently. Not entirely 'green', though. I rather want to build one, but maybe I should wait until a suitable alternator falls into my lap so I can make it actually *do* something :-)
We used to joke about that with Addies - "oh, look, they're burning the bodies again today". Used to see a lot of thick smoke out of their chimney on certain days...
cheers
Jules
Reminds me of the rats feeding cats etc "business opportunity".. a version of it goes a bit like:
Or something in 12 Volts, and a small PV panle to circulate. No battery, just a direct connection, then it'll only pump when the sun is heating the water...
Thomas Prufer
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