If it is really a problem I'll just run some cold water into the tank. Or cover the collector with a shiny reflector to shield it.
Since my last post I've thought of another brilliant wheeze: A galvanised dustbin. These are available from Wilko and elsewhere and are dirt cheap. If it's too tall, then I can cut it down to size with tin snips. The lid will still fit.
MM
On Sun, 22 Jun 2008 14:58:23 +0100 someone who may be MM wrote this:-
Are you around all the time during daylight to do this?
Just had a look - I'll bet they are expensive!! (No prices stated is a dead giveaway.) With all new technologies one has to find the "Ryanair" version, as too many suppliers will be jumping on the bandwagon and ripping people off, especially those with no DIY skills who have to trust tradespeople entirely. I tend not to, in principle, although, rarely, I am pleasantly surprised, like receiving a Christmas present one actually wants. I always start from the basis that a company is trying to sell me something that I could get elsewhere in a similar design for much less. My watchword is: IKEA!
Yes, I have studied numerous designs and watched some YouTube vids. Now is the time for hands-on experimentation, which is where I'm at.
Re your comment about steam, this system will be open, therefore there won't be any pressure build up. Also, the whole device is mounted outside the house, with the collector on a slant against the south-facing wall and the tank mounted above it, probably on 4" x 4" fence posts. Maybe I'm lucky in my back garden being a real sun trap. It does get incredibly hot during the summer (not today because it's so windy right now).
MM
I will have to see. If it isn't adequate, I'll add another 3m. Only £6.74 from B & Q and I take my pipe cutter with me so that the bus driver lets me on the bus with it.
The circulation is automatic, on the thermo-syphon principle, like a car radiator. Many old cars had no water pump.
Surely it gets flushed each time I empty it to use the hot water and it is replenished with cold?
MM
But the point both Dave and I were making is that a tank (whatever sort) not suitable for boiling water must not be allowed to boil. Which you could do manually - but what if you just happen to miss the temperature going past the critical point?
Designed systems have mechanisms to avoid accidental scalding. Take care.
Yes. I'm retired. If I go off somewhere on a very hot day, I'll just shield the collector so that the temperature is reduced. I won't need the hot water anyway if I'm away. Actually, I have designed the whole system to be unclipped easily for putting away during winter.
MM
"FFS"? Is this really necessary?
MM
So a galvanised tank such as used in lofts should be ideal? Or must I worry about chemical reaction between hot water and zinc?
I expect many more people are killed or badly scalded in ordinary domestic baths than are ever hurt during solar hot water experiments. Mind you, getting up on a roof carrying acres of garden hose might mean a few broken arms and legs when they fall off.
MM
It makes more sense than using something that is not designed for the job. I don't understand your approach to making a solar collector and hot water store.
FWIW, my first experiment was with a 1 metre square single-panel radiator. I painted the radiator with matt black using a high temperature paint, and built an enclosure using aluminium extrusions and aluminium sheet. I insulated the rear of the panel using urethane foam and fitted a glass sheet to the front of the panel. Connections to the top and bottom of the panel were done using hose tails.
This used as a thermal syphon or in conjunction with a 12V pump and 20W solar panel set up to recirculate water provided enough hot water for three people to shower and wash dishes/clothes. One a clear sunny day the temperature of the water got high enough to soften the hose used and to deform the first container I used. I changed to using a polypropylene container which is the sort of "plastic" container referred to by Hansen, which melts at 130°C and is therefore safeish to use with solar hot water. Polypropylene is an expensive material and if I had to pay for the container it would have been a silly price. The container had a screw lid wich I fitted with a vent and I insulted the body of the container.
If you don't have a tank with a lid, you will lose heat almost as fast as you collect it by evaporation from the surface of the water. If you don't have insulation the tank will cool rapidly. Your "serpent" is woefully undersized and IMO you have done little or no research before starting your project.
Other than it being neither enclosed not insulated you mean?
I'd be more worried about the reaction betweeen oxygen and steel.
I'd better just shoot myself then! ;)
MM
How about just getting a clue?
On Sun, 22 Jun 2008 15:25:06 +0100 someone who may be MM wrote this:-
Lucky you.
If you are interested in solar projects and have the time then the It's Not Easy Being Green forums have a thread on building a clone of the Solartwin.
On Sun, 22 Jun 2008 15:12:43 +0100 someone who may be MM wrote this:-
Four figures I believe. However, they do claim to reduce a number of disadvantages of normal thermal stores. Whether the price is worth the result is a matter of personal prejudice.
"Navitron Ltd is committed to providing low cost alternative energy solutions to the consumer and small business. For far too long, some companies have made huge profits from solar energy scams, ridiculously over-priced double-glazing units and funny magnets you stick in your hot water tank to ward off evil spirits! Don't get us wrong: We're a profit-making organisation; just not a profiteering one."
In essence you are building an "african" water heater, of which an example is . The steam vent on the right hand side of the cylinder is necessary and steam comes out of it even in the UK.
One of the disadvantages of a thermo-syphon design is that if the collector overheats more water will flow to the collector, to be turned into steam. The steam then bubbles up to the vent and more water flows to the collector. One of the advantages of pumped designs is that if the collector overheats the limited amount of water in the collector is turned into steam. This forms a steam bubble which goes a little way along the pipes and then stops. When the sun goes down water flows into the collector again and, provided the collector is robust enough, operation then continues as normal.
If you do this put the vent through the roof so that you don't introduce dampness into the loft.
If you are going to build a solar assisted HW system use a plausible design readily obtainable from C.A.T. and others.
What might you suppose I am trying to do here?
MM
I reckon solar heating is still seen, in Britain at least, as quirky, expensive, "designer" -- and there will be much exploitation going on, no doubt. As ever, no guidance from the Brown mob. Germany is far and away ahead, AGAIN!
Hey! They can be my friend!
The tank is going to be mounted outside on the wall next to my small annexe, where I have sink facilities. Nothing is going to be installed in the house. I even take the cold water from the garden tap.
MM
This is not going to be anything other than a standalone solar water heater. It will not be hooked into the house water system (apart from a connector on the garden tap). It will be dismantled in the autumn and only brought out again in the spring. The design I am following is a hybrid of many on the internet. Simple, straightforward, built largely of discarded stuff, thus dirt cheap. Many people would probably be able to make one for free with the contents of their rummage bin.
MM
At the moment demonstrating absence of same.
If you spent your =A313.48 on garden hosepipe you'd get way more heat. Cover it with polythene to give reasonable stagnation temp, lengthen the season and make it heat faster.
Yes, but it never circulates as well as pumped.
yes, but only if you empty both tank and pipe fully. I'm not sure how you're going to achieve that.
Freecycle might get you free hose. Almost any colour works, green, yellow etc. Using copper wont help.
NT
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