crosspost- Indoor Solar Heated Swimming Pool

[mcfridge]

Hey guys,

I did a search on here, but I still need some help so I thought I'd post. I was thinking of putting an indoor swimming pool in my new home, and I want to compare solar heating it with natural gas. The pool would probably be 10m long x 7m wide, with a depth varying from 1m to 3m. This pool will be used all year round, and it gets damn cold up here, so I'm guessing I'll need to run some sort of antifreeze solution in the piping (propylene glycol maybe?). I've done a bit of reading on solar collectors, and I'm gonna probably use glazed flat-plate collectors, and they have to be a certain % of the size of the pool, etc. But right now I'm more concerned with the pump, piping system, and materials.

I was thinking that the antifreeze would circle through the collectors, then go to a tank where I used some sort of heat exchanger to transfer the heat to the water. Is this the best way to do this? I'm having trouble determining how much water I need to send out (i.e. the flowrate). How do I determine this? Do I need 2 pumps (one for the antifreeze, one for the water, etc)? I feel once I determine this I can find the pipe size, pump size, etc, or am I going about this all wrong?

Sorry for the long post. I know I could probably hire someone to figure this out, but what fun would that be? I'd like to do this myself (with help from you guys of course). Thanks alot.

 

[mustangs]

How cold does it get where you are?

What I've seen commonly done is to have the solar panels also drive an extra pump, and have the water pumped up to the solar panels through small well insulated piping. The piping is then run under the solar cells and the radient heat from the solar cells is also used to heat the water.

This cycle continues to run constantly and heats up the water in the pool. There is no aux. tank.

Although, I guess you could use glycol in a line and a small glycol tank to keep a stock pile of heated fluid. You would probably want to vary the concentration of the fluid though depending on how cold it gets outside.

I need more info to do about the system, sizing, temps, etc. and you would need to have two pumps, but the one that operates the pool could be used to circulate the pool water through your heat exchanger.

 

[mcfridge]

Thanks for the reply.

I'm up here in Saskatchewan, so in the winter it occasionally drops down to around -40C, so that was why I figured I'd need to use some sort of antifreeze.

If I had the piping insulated enough, would I be able to get by without using glycol & a heat exchanger?

Thanks for your help, and what other info do you need for the sizing etc?

 

[EdStainless]

Comments about solar rigs that I have seen in cold climates.
1. Yes, use antifreeze, just in case.
2. Make sure that your solar collectors are self draining.
3. Turn the solar collection pump on when the collector gets warm (use a sensor). Shut it off when the increase in temp of the solution falls below some value.
4. Using a tank with a coil in it reduces your heat transfer efficency a little, but makes the control system easier.
5. You will need gas aux heating, but you should be able to run it less.
6. You can get incident solar radiation values, maybe from the weather service. I have some old ones around that I will look for. Then you apply an efficency and a heat loss to come up with your net heating.

= = = = = = = = = = = = = = = = = = = =
Corrosion never sleeps, but it can be managed.

http://www.trenttube.com/Trent/tech_form.htm

 

[mcfridge]

So I've decided that the system won't work in the winter, but I was trying to figure out the max temp rise I could get in the winter, using either anti-freeze or water running through the collectors (I'm either going to supplement the system with a heater, or just bypass the solar all together in the winter). I know the flow rate and the initial temperature, is there a way to calculate the temperature rise? I was thinking q = mcp(deltaT), but I don't know one of the temps and the heat transfer. Can anyone help me out with this?

Chris

 

[IRstuff]

If you do a search for "insolation," there are several sites that show insolation as a function of latitude. I don't particularly remember which site it was.

But a bigger chunk of your problem will be how well insulated your pool is. Whatever you do for input power might be for naught if the thermal losses from conduction and convection and evaporation are too high.

The first thing you need to do is to determine the thermal losses from your pool, given your target temperature setpoint. Only then can you begin to determine whether your solar heater even as a chance of keeping up.

TTFN