Re: Solar panels
 

Hi Bil

This is on youtube may give you some hints as there are a number of comments as to use of materials rtc.

http://www.youtube.com/watch?v=kXXOwfZA2Rk

Jim

Re: Solar panels
 

Thanks Jim.

The parabolics are fairly hard to draw out accurately, this guy is doing a simple semicircular one, but the problem is that it gives a less focussed beam, so that can reduce yield.

The interesting thing to look up is to do with catenaries. These are faux parabolas, created in the way that a chain hangs between two points. If the ratio of width to depth of the loop is 4:1, a catenary has a shape very close to a parabola, I think, (and also will focus light a bit less perfectly.)

On the other hand, it is capable of putting the beam onto the same spot, no matter where it comes from. That would be useful when building a static array that can't track the sun.

As has been pointed out, these create a powerful beam and need to be treated with respect. I would also suggest that the focus pipes be made out of a single tube. Soldered joints would be melted in a flash should the water drain out, and I'm not 100 % sure of the melting point of copper even.

All needs to be researched before starting. I used to melt lead airgun slugs with a 9" lens, so bear that in mind.

Re: Solar panels
 

Hi Jdr,
Thanks for your defence..... But
The company I work for supplies all approved systems for swimming pools that means approved firstly within Europe and also by the company so we can visit bars without fear of being lynched or chased out of town :ohmy:

Happy to advise you about what to look for and how to do it whether you do it that way or not is up to you and if I don't know, I know a man who does.

Regards, Dave

Re: Solar panels
 

Hi Bil
Simple method of drawing a parabola is to use the 2 pins and a pencil method. First developed by Johannes Kepler some 400 years ago. I remember we had to do this when we were doing dish theory.

http://mathforum.org/~sanders/geomet...9Parabola.html

Jim

Re: Solar panels
 

I just noticed a British lady had trouble with her immigrant workers in Murcia They had no tea making facilities on site, So being a true Brit she had built the item you see in the Pic below in order to provide hot tea brewing water.. I notice the kettle to the left of the group so evidence of a recent brew maybe. Like the builders always say....Nowt like a cuppa to wash down the lama sandwiches. :beer::beer::beer:

Re: Solar panels
 

Soory if I wrongly branded you as a solar installer . Tell me, these regulations re fitting solar items (not photo voltaics). What sort of things do they cover please?

Re: Solar panels
 

Thanks for that. That looks a simpler method than I have seen elsewhere. The parabolas do give a very tight focus, but the system I am thinking of (for reasons of being broke) need to be very cost effective. I want to get one of those little laser pointers and have a play with a catenary curve, because a parabolic trough will only give a good result when pointed at the sun, and a catenary is alleged to keep the focus constant (even tho it is a fuzzier focus, and obviously will diminish a little as the sun tracks), and that will save me the cost of a tracking system.

Re: Solar panels
 

Basically it's the safety aspects of the system venting 100°C hotb water into the pool, if you could imagine someone standing in front of the water return jet and the solar system decides to het the pool, the valve changes position and boiling water is pumped into the pool the return is in the shallow end and most likely place for children and elderly, children are attracted to the jets.
So it is simply a heat exchanger should be between the Solar system and the pool water - make sure it is a titanium heat exchanger or titanium and plastic as some of them are nowadays.

Regulations for heatpumps: cable suitable for the electrical load fed from it's own suply breaker, Unit connected to a Local copper earth stake, local electrical isolation switch within sight of the heatpump.

Regards, Dave

Re: Solar panels
 

Ah, that explains it. A baffle or something would make enormous sense.Me, I am looking at providing hot water for the house, so the problems there are no more than apply to water supplied by the boiler. I plan to feed the hot water tank with a header tank plus a heat relief pipe venting into said header, which was the system I used in our old house in the UK.

Re: Solar panels
 

Hot water systems require a tyemperature controlled combiner valve to regulate the hot water temperature delivered to the tap, shower etc.

Solar systems can get very hot and it's possible to get steam

Regards, Dave

Re: Solar panels
 

Let's face it, they can boil away quite merrily. There are some systems in France that melt steel.

Re: Solar panels
 

I`ve seen overheating melt the solder out the joints on copper pipework, but melt steel is a bit over the mark innit. ;-))

Re: Solar panels
 

Enough solar energy per sq foot, and you could melt titanium.

Re: Solar panels
 

Come on bil get a grip, we are talking water systems here, not ruddy laser guns.
Too much heat in an unsealed system will cause the water to steam out the vent and may melt the solder in copper fittings or melt the plastic pipes nearest the heat source.
To much in a sealed system would blow the pressure valve or the pipework at the weakest point then could possibly melt the solder in the fittings or the plastic pipes nearest the heat source.

Re: Solar panels
 

Well, be fair. I was merely pointing out that the only difference between melting metal, and warming water is the amount of sunlight falling on unit area of pipework.

Commen sense has to be used. The troughs should not be TOO big, the focal pipes should be one piece, and pressure must be vented, for example in the way I suggested. There must be no plastic pipes in the 'hot zone' and it is adviseable to connect panels with connectors to allow for hea induced movement.

Basically, if someone isn't bright enough to work all that out then they really shouldn't mess with it.