solar hot water systems

[Ex- Member]

I recall last summer several members embarking on fitting solar collectors on their boats for hot water. Has any one completed this type project with any success. I have searched without luck.

 

 

I have the plans and bits required for the solar collector, I was planning on a sealed system that would heat water via the calorifier.

 

Basically a solar collector paqnel just under a s/q M, a 12 volt pump and expansion tank. In what order should this be fitted though though. Any plans of info welcome, cheers

 

 

[MtB]

I hesitate to say 'waste of effort', but cannot imagine the energy from the sun falling on one square metre being enough to heat more than a litre or so an hour at midday in high summer. I haven't doen the calcs though.

 

I'd also imagine that in winter you'd struggle to heat a litre of water a week. This is probably why no-one has posted positive, successful results.

 

 

MtB

 

 

Edit to add:

 

From Wikipedia, "Sunlight's composition at ground level, per square meter, with the sun at the zenith, is about 527 watts".

The specific heat of water is 4.184 Joules per gram per degree C.

 

So with the sun at it's zenith, a one square metre water heating solar panel can raise one ML of water by an upper limit of 527/4.184 degrees per second. That's 62 degrees C per ML per second.

 

To raise one litre through 62 degrees will take 1000 seconds. To raise, say, one litre though 31 degrees ( a more useful rise) will take 500 seconds. To raise 25 litres through 31 degrees will take 208 minutes, or 3½ hours.

 

All this assumes a solar water panel 100% efficient, no losses anywhere, and full sun. In the UK I'd guess the sun in summer is attenuated by about 50% and in winter, by about 90%, And thats when its out! So on a sunny summer's day expect your solar panel to take 7 hours to heat a small calorifier of water, or 35 hours in winter. Longer on a cloudy day...

 

No doubt I have made some howling mistakes!

Edited January 22, 2013 by Mike the Boilerman

[Bobbybass]

I designed...and installed my own system a couple of years back.

It 'evolved' to be quite complicated....with some factors I will list at the end of this.

It works really well...and at the time I published photos/diagrams on here.

I made my own collector...

 

Things I had to take care of:

Unable to use a commercial type collector as many were designed to be convection units. This is like the ones you see on houses abroad. It would have involved raising the system up every time you moored..or it would not clear bridges.

Such a system would have caused problems...as the roof would be the highest part of the boat...I could not simply harness the roof collector into my existing heating coils on the calorifier (engine..Eberspacher....) as the roof being the highest part...the heating water..would have flowed out of the top of the engine or the Eber header tank.

 

I wanted it to be easy to maintain....so I ended up with a 'closed' system with its own anti-freeze..and this runs into a second calorifer tank.

My solar calorifier tank feeds into the cold fill on the main tank.

The whole system is computer controlled from a comprehensive panel...which shows details of temperatures of roof collector and both tanks.

If the roof collector is hotter than the solar tank..it circulates the fluid through the roof..and heats the water in the solar tank. It only does this if the tank is colder...as you do not want to pump your hot water to the roof and cool it !

If the solar tank ends up more than a few degrees hotter than the main tank...a second circulation pump starts up..which pumps the hot water into the main calorifier tank...and the cooler water is returned to the bottom of the solar tank.

 

Since I installed it a couple of years back..it has worked amazingly well...and I never really touch it..it monitors and looks after itself. I occasionally hear a pump buzz from time to time...

 

I made the collector...zig zags of 10mm copper pipe...bolted to a 3mm aluminium plate..inside a box..with insulation under it...

I tried to bleed it on an overcast day..when I installed it...and BURNED MY FINGERS !!

 

I have now...reposted the diagram in the gallery.

Edited January 22, 2013 by Bobbybass

[Ex- Member]

Hi Mike

 

 

Slight error in panel size i posted, it's over a s/q meter not under.

 

By following these construction details you will be able to build a solar panel 1500 mm by 900 mm, giving just under 13500 mm2 collector area. http://www.bigginhill.co.uk/solar.htm

 

This collector is a diy version and the guy who designs it reckons a single panel it's good to heat around 15 gallons which is our calorifier size. It won't be the main sourse of hot water, engine running will also supply hot water when applicable but we have 500 watts of solar panels as well which means we'll dramatically reduce engine running, so a solar collector makes sense as another sourse of water heating. Also It's cheap to make and install, so as i see it, nothing ventured nothing gained. Of course of little use through the winter, but we'll be running the bubble stove then which can heat the water.

 

There were some members planning much the same, I haven't been on the forum much lately so wondering if anyone finished a project.

[MtB]

Vereeee interesting Julynian!

 

MtB

[matty40s]

Dan (Smelly) was building one but has spent that much time chasing cats hasn't finished it yet when I last saw it.

[DeanS]

There's an article by a guy on a yacht in the Med...who built himself one....it's in the Boat Owner magazine in WHSmith as we speak...unless it was last months issue.

[bowten]

There's an article by a guy on a yacht in the Med...who built himself one....it's in the Boat Owner magazine in WHSmith as we speak...unless it was last months issue.

If only we lived in the med Dean,we would all have them.

[Bobbybass]

There's an article by a guy on a yacht in the Med...who built himself one....it's in the Boat Owner magazine in WHSmith as we speak...unless it was last months issue.

Only thing to watch for..(and I'm not knocking it..only being helpful) is the different arrangement in a narrow boat. We 'tend' to already have calorifier tanks stuffed with coils that heat from engine...Eber/Webasto and electric Immersion. I toyed with just getting one calorifier tank with one immersion and three heating coils..but there wouldn't be much room left for the water !....

 

There is also the 'high point' of the boat to consider...that if you try and double an Eber coil or Engine heat..the water from the roof collector will flow out of your engine...

Another point...is that if you just pump your water direct to the collector..then into your calorifer...on a cold day...you could end up with colder water filling the tank than you would get otherwise...

I opted..for the extra tank (as in the gallery) as I could put strong antifreeze in there...and just not bother with it much...or have to drain down...

I never drain down..when I leave the boat for 6 months...

 

There are easy options available..for example..

Summer before last..I met a guy with one of those Halfords..camping showers...who said is was great and less than £20. Its just a black plastic tub..that he put on his roof..and then ran a plastic hose through his bathroom window.

 

I think...'inventivness'..is the clue here..

Go and have a great time with it...and enjoy your inventiveness..

 

Bob

[smileypete]

If something ready made is better there's a relatively cheap panel on Ebay that looks alright:

 

http://www.ebay.co.uk/itm/221062045055

 

The better ones have a selective coating that doesn't re-radiate heat so easily. Also not all flat plate collectors may be mounted completely flat.

 

cheers, Pete.

~smpt~

Edited January 23, 2013 by smileypete

[Bobbybass]

If something ready made is better there's a relatively cheap panel on Ebay that looks alright:

 

http://www.ebay.co.uk/itm/221062045055

 

The better ones have a selective coating that doesn't re-radiate heat so easily. Also not all flat plate collectors may be mounted completely flat.

 

cheers, Pete.

~smpt~

That looks quite good..as making the panel with coiley pipe can be a sod...

You still have to figure though..just how you are going to get the hot water out of it..?

If you look at my comments above..it give you some things to 'ponder'...

 

As you say..some flat panels are designed to not be flat..and to use convection. I considered this..but you would have to lie it down when you move to clear bridges...

That is why..mine is 'pumped'...

I'm always interested in other ideas..maybe I overcomplicated it..?

 

Bob

Edited January 23, 2013 by Bobbybass

[OldPeculier]

The year before last I made a spiral out of this stuff, fixed it to a piece of ply and plumbed it into a 5 gallon bucket so that it would heat syphon. It was a hot day I admit but by early afternoon, the water was too hot to put your hand in.

 

When we are camping we usually leave a couple of black painted 2 litre lemonade bottles in the sun for washing up water. (dont screw the lods down tight!)

 

And dont forget solar cooking. Currys and caseroles done on top of the boat for free.

Edited January 23, 2013 by OldPeculier

[Bobbybass]

The year before last I made a spiral out of this stuff, fixed it to a piece of ply and plumbed it into a 5 gallon bucket so that it would heat syphon. It was a hot day I admit but by early afternoon, the water was too hot to put your hand in.

 

When we are camping we usually leave a couple of black painted 2 litre lemonade bottles in the sun for washing up water. (dont screw the lods down tight!)

 

And dont forget solar cooking. Currys and caseroles done on top of the boat for free.

Some people I know in Spain...have plumbed a couple of hundred feet of that into the cold feed of their hot water tank. It just hangs on the wall outside the house like any other hose. Most days..the hot water never gets cold...as the tank always fills with hot...via the hose.

I guess..it must hold quite a few gallons..?

Edited January 23, 2013 by Bobbybass

[Ex- Member]

All input appreciated, cheers all

 

That solar collector on e-bay is temping, alhough I have all the bits to make my own mostly using leftovers from the boat build.

 

I think a sealed system with anttifreeze will be the way to go using a 12v pump and expansion tank, I can use the calorifier coil we currently use for the diesel stove. I'm thinking of plumbing it in such a way that I can switch from solar to stove using a lever type valve which I can' remember the name of, it allows switching without losing pressure in either system.

 

I'm no interestted in piping hot water, hot enough for a shower is ample and hot enough for a normal wash in the twin tub washing machine.

[Bobbybass]

All input appreciated, cheers all

 

That solar collector on e-bay is temping, alhough I have all the bits to make my own mostly using leftovers from the boat build.

 

I think a sealed system with anttifreeze will be the way to go using a 12v pump and expansion tank, I can use the calorifier coil we currently use for the diesel stove. I'm thinking of plumbing it in such a way that I can switch from solar to stove using a lever type valve which I can' remember the name of, it allows switching without losing pressure in either system.

 

I'm no interestted in piping hot water, hot enough for a shower is ample and hot enough for a normal wash in the twin tub washing machine.

 

Hi...

Sounds fine...

You don't actually need 'pressure' in the solar side of the system. I have a small plastic food box..the type with the snap down seal lid....that is on the roof..

The pump is under the bed...so the pump puts the fluid to the roof...it goes through the cell...and then it flows into the box...the pick up pipe being in the bottom...so there is always a little air gap in the top of the box. There is no pressure in the system....as the pump draws the fluid down from the box...and thus it doesn't need bleeding these days.

 

Having a 'spare' calorifer coil is handy.

 

I do not know..your own setup...so please don't criticise..but...you have to make sure there is no 'header' tank on your existing stove....that the water could flow back from the roof box..and overfill it. It is also handy..to have automatic control that the roof doesn't circulate if the roof cell is colder than your tank..or you will cool your hot water...is it called..a solar comparator..?...no actually..I think its a solar differential controller..?

 

Some handy 'bits' here....

 

http://www.solarproject.co.uk/

Edited January 23, 2013 by Bobbybass

[DHutch]

I designed...and installed my own system a couple of years back.

It 'evolved' to be quite complicated....with some factors I will list at the end of this.

It works really well...and at the time I published photos/diagrams on here.

I made my own collector...

Ive just been lead here by your images in the gallery (three photos, link to the first here) and find it very interesting. We almost always have the boat in steam when we're on it, and as such hot water is one thing we are never short of, but it looks a good system. Ive used one of the gravity fed systems you talk of when in Turkey for a week and it work very well, we could get up on the roof and look at it up close, and it was remarkably crude, right down to the non weather protected terminals on the immersion heater that would get laughed out of the UK but it worked a treat and could reheat its water (ten of use showering) in an hour or so.

 

My current house and first is I expect a bit of a 'stop gap' and has a combi boiler but in future I hope to built or heavily renovate a house and do some inventing/innovating as you call it.

 

I have also considered fitting a water reusing system to our boats bath, as while we can heat as much water as we like as hot as we like, we only hold 80 gallons on board and It would be quite nice to be able to have a wash, to get clean, and then switch it over to use the grey waste as the cold feed, topped up with heat from the hot, which we could heat up very hot to reduce the lost volume.

 

 

Daniel

[Ex- Member]

Hi...

Sounds fine...

You don't actually need 'pressure' in the solar side of the system. I have a small plastic food box..the type with the snap down seal lid....that is on the roof..

The pump is under the bed...so the pump puts the fluid to the roof...it goes through the cell...and then it flows into the box...the pick up pipe being in the bottom...so there is always a little air gap in the top of the box. There is no pressure in the system....as the pump draws the fluid down from the box...and thus it doesn't need bleeding these days.

 

Having a 'spare' calorifer coil is handy.

 

I do not know..your own setup...so please don't criticise..but...you have to make sure there is no 'header' tank on your existing stove....that the water could flow back from the roof box..and overfill it. It is also handy..to have automatic control that the roof doesn't circulate if the roof cell is colder than your tank..or you will cool your hot water...is it called..a solar comparator..?...no actually..I think its a solar differential controller..?

 

Some handy 'bits' here....

 

http://www.solarproject.co.uk/

 

 

That's very interesting cheers. Our central heating system is a sealed pressured system which runs at 1.5 bar. It does circulate through thwe calorifier and I propose sharing the coil using a Y type valve which allows simple selection of either heating source. I've seen this valve on a couple of boats before, basically a diverter, as one is shut off the other opens.

 

Not having pressure is good. You can fit a time switch on the 12v pump so water only circulates during the daylight hours I recall a non return valve being used can stop cold water returning to the calorifire ore ensure folw in one direction only. I'm not completely sure in what order this should all be though LOL I'l consider any set up though although a permanant system is preferred that can be left free of attention through the winter.

[Bobbybass]

That's very interesting cheers. Our central heating system is a sealed pressured system which runs at 1.5 bar. It does circulate through thwe calorifier and I propose sharing the coil using a Y type valve which allows simple selection of either heating source. I've seen this valve on a couple of boats before, basically a diverter, as one is shut off the other opens.

 

Not having pressure is good. You can fit a time switch on the 12v pump so water only circulates during the daylight hours I recall a non return valve being used can stop cold water returning to the calorifire ore ensure folw in one direction only. I'm not completely sure in what order this should all be though LOL I'l consider any set up though although a permanant system is preferred that can be left free of attention through the winter.

 

Hi..me again...

 

I would recommend the differential switch on the 12 volt pump...

Otherwise..if you switch it all in the daytime..you may heat up the water nicely..then the sun goes in...and the pump then carries on circulating your..now hot..water to the roof to cool down !.

If the sun stays in..you will come back to nice cold water..

 

If you look at the www.solarproject.co.uk site...there is a simple version of this available..or they sometimes come up on Ebay if you type in differential controller.

It just has a temperature probe for your roof panel..and another for your tank. When the roof panel is 'X' number of degrees hotter than the tank..it starts the pump. I have the sophisticated controller that they advertise....but only because I have a second pump system.

Edited January 23, 2013 by Bobbybass

[Ex- Member]

Hi..me again...

 

I would recommend the differential switch on the 12 volt pump...

Otherwise..if you switch it all in the daytime..you may heat up the water nicely..then the sun goes in...and the pump then carries on circulating your..now hot..water to the roof to cool down !.

If the sun stays in..you will come back to nice cold water..

 

If you look at the www.solarproject.co.uk site...there is a simple version of this available..or they sometimes come up on Ebay if you type in differential controller.

It just has a temperature probe for your roof panel..and another for your tank. When the roof panel is 'X' number of degrees hotter than the tank..it starts the pump. I have the sophisticated controller that they advertise....but only because I have a second pump system.

 

Cheers Bobby

 

Of course I didn't think of that I'll take a look at the site some more. It will also save energy, cheers

 

 

 

 

ETA, yeah some great devices from there, great link cheers.

Edited January 23, 2013 by Julynian

[lewisericeric]

I asked about this last year but was quickly dismissed as it being a waste of time and just to use the immersion heater early in the morning whereby the solar panels would then recharge the panels by early afternoon ....

 

Still interested in something like this....with only a calorifier and no need in summer to have the engine on at all (690w solar array) except to heat water this would be really good for me...

[Bobbybass]

Here you go...a differential controller...and change out of £23 !!!

 

http://www.ebay.co.uk/itm/12VDC-SOLAR-WATER-HEATING-PUMP-CONTROLLER-WITH-TEMPERATURE-SENSORS-AND-RELAY-/271139906776?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item3f2132a4d8

 

Cheers Bobby

 

Of course I didn't think of that I'll take a look at the site some more. It will also save energy, cheers

 

ETA, yeah some great devices from there, great link cheers.

 

Looky looky !!!

 

http://www.ebay.co.uk/itm/12VDC-SOLAR-WATER-HEATING-PUMP-CONTROLLER-WITH-TEMPERATURE-SENSORS-AND-RELAY-/271139906776?pt=UK_Home_Garden_Hearing_Cooling_Air&hash=item3f2132a4d8

[PaulJ]

As a matter of interest how hot do the collectors get- say in comparison with a dark coloured roof on a sunny day?

I have often wondered if you could run pipes internally (and in the insulation) although obviously this is not feasible as a retro fit and would need doing at fit out or refit stage.

I know I have been unable to kneel on a roof on a hot day so that must make for some decent hot water? Would have the added advantage of cooling the roof too.

[smileypete]

That looks quite good..as making the panel with coiley pipe can be a sod...

You still have to figure though..just how you are going to get the hot water out of it..?

If you look at my comments above..it give you some things to 'ponder'...

 

As you say..some flat panels are designed to not be flat..and to use convection. I considered this..but you would have to lie it down when you move to clear bridges...

That is why..mine is 'pumped'...

I'm always interested in other ideas..maybe I overcomplicated it..?

I'd have thought it'd be connected the usual way, with a small pump and differential thermostat. Run the pump off a small PV panel so it varies speed with the strength of the sun.

 

Using small dia well insulated tubes between panel and calorifier would help performance, but with a large highly efficient panel it'd also be good to have some sort of heat dump and a thermostatic valve to keep things from overheating.

 

Noticed that some flat panels say they need to be between 20° and 90°, not sure if that's due to performance reasons or what. In winter it'd be good to have some way of tilting the panel up toward the sun.

 

cheers, Pete.

~smpt~

[ditchcrawler]

I asked about this last year but was quickly dismissed as it being a waste of time and just to use the immersion heater early in the morning whereby the solar panels would then recharge the panels by early afternoon ....

 

Still interested in something like this....with only a calorifier and no need in summer to have the engine on at all (690w solar array) except to heat water this would be really good for me...

are you running your immersion heater off the inverter then?

[Ex- Member]

Here you go...a differential controller...and change out of £23 !!!

 

http://www.ebay.co.u...=item3f2132a4d8

 

 

 

Looky looky !!!

 

http://www.ebay.co.u...=item3f2132a4d8

 

 

 

Hi Bobby

 

 

 

Cheers for the links, I've bough suff from REUK before and it's been very reliable so might well go for rhat unit.

 

I have a lot of 10mm copper tube left coiled and inend to use that inside the collector, the collector will be placed almost directly above the calorifier, what would you recommend is the best tubing to use to feed and return tto unit. Possibly this stuff from http://www.solarproject.co.uk/page2.html

 

SP20 Coloured Silicon Pipe 12mm OD (2.5mm wall) £3 for 1 metre