Solar pump for DIY Solar heater

[eds]

I'm looking to find a small solar powered pump to power a DIY solar heater for my pond.

My idea is this.

I will sit a small pump in the last chamber of my filter connected to a solar panel. When the sun comes out the pump will start working and will pump water through 12mm black tubing. The tubing will run to the solar panel which will just be the same 12mm black tubing snaked around behind a spare window I have with an insulated back to keep the heat in the air gap. When the sun goes in the pump will stop and because of the way I'll arrange the pipes the water should drain out of the pipes leaving them empty.

What I'm thinking is that using the solar pump will solve the 'when it comes on and goes off' issue as well as free power! In other words it will only come on when the sun is out and strong enough to heat the water and as soon as the sun goes in it will turn off and not chill the water!

However for this to work I need a pump that's just big enough to pump water around the tubing and also that doesn't have a battery to retain the charge. Does anyone have any experience of these water feature solar pumps? I was looking at this one, http://www.watergardeningdirect.com/aca ... tures.html" onclick="window.open(this.href);return false;

Any advice/ideas/opinion? Will it work do you think?

[Chagoiboy]

Ive thought about this also. Not sure how useful that solar pump will be.. maybe someone knows their output.
If not then maybe a 240v pump with some kind of light sensing switch?

[eds]

Ive thought about this also. Not sure how useful that solar pump will be.. maybe someone knows their output.
If not then maybe a 240v pump with some kind of light sensing switch?

Well that's part of the trick really - I'm hoping the small, cheap, solar pump will only just be powerful enough to push a decent trickle through the pipe so it has time to heat up. If I got too good a pump then the water wouldn't have much contact time in the pipe. I just need one that's strong enough to pump the water trough all that pipe.

[fishyfingers]

Solartwin is a company which makes solar pannels based on the same principal, using a photovolatic panal to generate power to pump water around the system. Their system retains the water in the pipes and it might be worth visiting their site and even talking to some of their tech people.
Pump issues will start with head height of tubing etc and it may be of benifit to fit non return v/v to your tubing.
http://www.solartwin.com/?gclid=CNaukvb ... 2AodPw6jLw
good luck keep us posted

[kayoss]

Hi Ed

Have you thought about investigating a 12v option?

Maplins sell a range of 12v solar panels and "Whale" and "Waterra" make 12v pumps for a range of uses from boats and caravans or pumping water from wells up to about 25-30m deep - fairly low flow rates, but that's what you want.

Cheers

[Dave Collins]

Don't fit a non-return valve, if the sun doesn't come out for a few days then the bacteria in the water will have time to multiply before the sun comes out again and dumps the toxic soup into your pond. Hey presto, no Koi. Believe me, I've done it and am not proud.

Dave

[eds]

Cheers for the advice guys. Solar twin stuff looks expensive!!! I was hoping for a simple, lowish tech approach!

Definitely no non-return valve - I want it to empty every time the pump goes off to prevent it overheating and bacteria building up. Have you made your own solar panel then Dave? Any pics?

Bob, those sound like a great idea. Will investigate!

[stuart t]

Hi Ed,

someone I know is planning to do just such a thing using the smallest central heating pump you can get.

rgds

stuart

[netsukekoi]

An alternative to an open pipe that is empty when not 'heating' is a closed loop, half in the solar panel and half in the filter bay. When the sun is out, the small solar pump will circulate the water and when it is not it won't - but the head and pump capacity will be much less of an issue (although ideally the 'heat exchanger' half ought to be stainless steel pipe of similar inorder to release the heat into the pond.

This approach also has the advantage that any nasties in the pipe stay in the pipe.

[Chagoiboy]

I noticed a lot of the solar pump kits use batteries. So these ones wont achieve what you're after. Trouble is the ones ive seen that directly drive the pump from the panel seem very low output, i wouldnt bet on them being able to circulate up onto the shed roof for example. Maybe a fish tank powerhead type pump - 240v and down to pretty low outputs... light sensing switch.. im off to browse rs and maplins lol.

[eds]

Cheers again guys. Stuart we'll have to have a chat about it next weekend I think!!!!

I agree a closed loop might reduce head but it'll complicate things - I'm after a K.I.S.S. system!

I'm thinking of putting this solar panel onto the decking above my filter chamber so the static head will only be about 1m. Might have to just buy the cheap pump and try it as the more expensive pumps all come with batteries which, as you said, won't work properly.

[Casper Chapman]

By using solar to heat your pond, could you end up with vast temperature variations during day/night. I realise you get this with normal sun on the pond, but possibly not to the extent you may have?

[eds]

By using solar to heat your pond, could you end up with vast temperature variations during day/night. I realise you get this with normal sun on the pond, but possibly not to the extent you may have?

Possibly but I'm hoping that with the inefficiency of the system I'm planning, the low flow rate and the size of my pond it will only slowly raise the temperature so rapid swings won't be a problem. I reckon if the water coming out is 5 degrees warmer than when it went in I will b doing well and if it's only trickling out then it won't be moving more than the pond volume every day, even on really sunny summer days.

[eds]

Right it's looking like Bob's option of a panel and a caravan water pump is going to be the ticket!

I now need some advice from the more electrical savvy of you guys!

I reckon this would be a good choice of panel as it will be mounted outside all year, http://www.maplin.co.uk/Module.aspx?Mod ... &U=strat15" onclick="window.open(this.href);return false;

And I reckon this will be the best pump to get, http://www.leisureshopdirect.com/carava ... p1002.aspx" onclick="window.open(this.href);return false;

Or this,
http://www.campervanaccessories.co.uk/w ... 2cdec88aad" onclick="window.open(this.href);return false;

Either way is that all I need? Do I have to use a battery or some other convertor/capacitor or can I just connect them directly? Bit clueless when I move away from standard electrics to be honest!!!!

[Chagoiboy]

you wont be able to run that pump straight from the solar cell. Its 12v 2.4amp. The cell puts out max 16v 390ma. Also states you need a battery.
So how will you turn it off at night? you could have a timer which you keep changing i suppose...
I looked into the light sensitive switch for running a 240v pump, not as easy as i thought, youd need a LDR switch (light/dark/relay) which the ones ive seen need a 12v input but can switch a 240v supply.., they sell a 12v supply for the relay with it for not many pennies.

LDR switch - http://www.quasarelectronics.com/3079b- ... eresis.htm" onclick="window.open(this.href);return false;
12v supply for it - http://www.quasarelectronics.com/psu445 ... 1000ma.htm" onclick="window.open(this.href);return false; - or you could have your solar panel and battery to provide the 12v supply for the LDR.
Use with any 240v pump up to 5amp (1200w). Will switch on at dawn, off at dusk.