DIY PV panels

various 12volt pumps to be found on ebay

Reply to
cynic
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which will take as much electricity as the typical panel generates...

Reply to
The Natural Philosopher

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Jules Richardson saying something like:

Use the heat, Luke.

Reply to
Grimly Curmudgeon

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember The Natural Philosopher saying something like:

Jesus H. Christ, you're in such a hurry to diss the idea of ANY solar solution that you don't even bother reading the post properly.

Reply to
Grimly Curmudgeon

Yeah, I did wonder about that. Battery might still be useful - I think there's some beneficial solar water heating effect during the day long before a PV panel starts doing anything much - the water wouldn't get hot until later in the day, but it would start to warm up. I keep a good battery up in the 'shop anyway for starting the lawn tractor in the vehicle shed behind, and the rest of the time it just sits there idle (and needs occasional charging), so it'd be a 'free' addition to the system.

Not sure how serious a pump it'd need, though - it'd have to be something rated for quite high duty, and might have quite a significant current draw (I suppose I could add some sort of intelligence to circulate water periodically rather than continually)

cheers

Jules

Reply to
Jules Richardson

Yeah, no argument there at all. For clarity, it was a "can it be done" question rather than an "I want to do it" one :-)

cheers

J.

Reply to
Jules Richardson

I did read it.

circulation pumps take typically 50W or so.

Reply to
The Natural Philosopher

Just the ticket:

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Reply to
Vortex7

Reply to
Huge

That's why they aren't usable for systems like this. You're talking about a domestic CH pump that assumes a plentiful supply of AC mains, doesn't care about efficiency (Hey, it's just added heat) and is pushing water around a houseful of sludged-up 15mm.

For the solar situation here, you need to circulate through the panel's resistance alone, ignoring the short lengths of fat downcomer as they're such low flow resistance. If you're using heatpipe tubes (rather than flat panel), the panel header resistance is minimal too. Some systems have such low flow resistance that more power is going to counteract their reverse thermosyphon effect than the resistance.

It also needs to be DC and not too fussy about voltage. To avoid the need for separate motors and glands, current tech is to use a brushless DC motor. This is a 3-phase inverter drive to motor without sliprings, either rare-earth magnet or induction, and it's thus easy to make the inverter accept a wide voltage input range.

These take a lot less than 50W. Under 10W is typical for best practice, where the heat store and panel are closely coupled.

Yesterday I acquired 60W of surplus solar panels, and it cost me less than a new circulator pump would do.

Reply to
Andy Dingley

No, I am talking about a 12v pump.

Even an electric toothbrush takes a few watts you know.

I know. I use these things daily, and believe me 50W is small beer. Its barely enough to fly a 12 oz aeroplane.

I very much doubt that. The controllers alone take a couple of watts just doing nuthin..

Bully for you.

Reply to
The Natural Philosopher

I was responding to the "level of effort needed". There'll be plenty of human capital to draw on, if only someone had the will to implement dome kind of workfare.

MBQ

Reply to
Man at B&Q

Dome kind?

Hmm.

I have to say that I know a few of the long term unemployed, and frankly, so long as the dole represents a lazy way to get by, that's all they will ever do. Why they are like that, I cant say, but most of them would need the equivalent of a slavemaster with a whip to do anything more than pull their trousers up.

Whenever called upon to do anything, they are far more likely to cost you money than make any.

Somehow they are in a depressing spiral of total incompetence, resentment and alienation: the more like that they get, the less useful they are.

I cant say I myself would not have been like that if the dole in my youth hadn't been anything other than the very worst alternative of all, and far less attractive than working..

Reply to
The Natural Philosopher

Reply to
Jules Richardson

The rotor is in an enclosure which requires no external shaft.

Chris

Reply to
Chris J Dixon

There's a magnetic rotor in there, on water-lubricated bearings. A rotating magnetic field is applied to this, from out in the dry bit. Only magnetic flux crosses the wet/dry boundary, no rotating shafts need to, nor electrical current.

This principle dates back to the Victorians. Although it didn't work too well back then, they recognised the simple virtues of it, if only they could get it to work.

There are two tricky bits of tech you need to do. One is a rotating magnetic field. This uses three-phase AC quite easily, or an inverter to generate it. The second is a rotor that uses either an induced current (a squirrel cage rotor) or more commonly these days for small motors, a rare-earth permanent magnet.

Reply to
Andy Dingley

Oooh. I remember dreaming up a concept* like that aged about 7 or 8, and deciding it wouldn't work very well. Nice to know it's been done (and that the Victorians got there first ;) I must have been under a rock, and have never even heard of anything like it in the many years since.

  • sort of. At that age I didn't get any further than magnets on either side of a non-magnetic chamber; electro-magnetism-wise, I hadn't done much more than the old battery, coil of wire and bloody great nail experimentation :-)

I'll have to go do some googling...

Ta!

Jules

Reply to
Jules Richardson

Most of the COTS systems I have seen use very much smaller pumps - think solar power fountain rather than CH pump. The pump circulates a small amount of water round the panel and hot water cylinder usually.

Reply to
John Rumm

There's a lowest-end pool heater, very cheap and sheddy: a coil of corrugated black pipe, filled with water and looped over a nearby roof or so. One end in the bottom of the pool. The other end sticks out of the pool by 1-2 mm, held by a floating ring. Once the water warms up, it will come out of the raised end due to the thermosyphon effect. Once the coil cools of an evening, it can't suck the water back because of the 1 mm step, and this prevents the coil cooling the pool.

Reportedly, the original float was a ring of copper wire around the pipe, with three burned-out light bulbs soldered to the ring.

Thomas Prufer

Reply to
Thomas Prufer

We were somewhere around Barstow, on the edge of the desert, when the drugs began to take hold. I remember Jules Richardson saying something like:

I'm not saying this is the answer, but rotating magnets one side of a brass wall, and a steel bar inserted in the impellor on the other side. The seal problem was a very real obstacle for uranium hexafluoride pumps during the bomb program, eventually being sorted by a solution looking for a problem - Teflon. As I was reading about it, I thought of the magnetic fix, but whether that would have worked with the very corrosive environment involved I don't know. It was just an idea - perhaps similar has actually been made to work.

Reply to
Grimly Curmudgeon

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