Solar panel to heat hot tub

TheBraes

Hi
can anyone advise re installation of solar panel or small wind turbine to create enough power to heat our hot tub? Our bills are reasonable except when we have the hot tub on. My husband thinks there must be a way to install solar or wind power linked to this one appliance without having to sell back to grid etc. Any suggestions are welcome. Many thanks 😊

QrizB

Unless you live on a hilltop or an oil rig, a wind turbine is unlikely to be a worthwhile investment.

How much heat does your hot tub need, and how often do you run it?

matelodave

You need to do a few sums to work out how much energy you require.

What size is the tub (ie how much water does it hold?
What size in kw is the heater
What temperature are you heating it from to how hot do you want it and how long do you want it to stay hot.

When do you use it - you wont get much energy from solar at this time of the year and non at all at night and, as said above, you wont get much from a wind turbine unless it's a big one with plenty of space around it.

THB the cheapest way to heat a hot ub is probably with a heat pump, but as with solar or wind, the outlay probably wont be worthwhile or payback within a reasonable amount of time, so you'd need to explore the costs of a heating solution and compare it with the cost of using leccy from the mains.

lohr500

Depending on your hot tub design, you may be able to graft in an external wood burning heater circuit to boost the temperature.
But I suspect unless you are using a massive amount of electricity to heat it, then it wouldn't be cost effective.
And it would mean planning ahead to light the burner in advance to get the temperature up to a reasonable level. 

Do an eBay search on item 294237832902 for an idea on what I am talking about.

I did wonder about something similar for our hot tub but decided it would be more hassle than it was worth!!

Reed_Richards

The only advantage of using solar panels exclusively to heat your hot tub is that you might be able to feed the output directly to the hot tub without the need for an inverter, and that might save you £500 or more.  But then you would need some sort of manually operated changeover and isolation switch so you could heat the hot tub from the mains when necessary (i.e if the sun is not shining).  So in order to save yourself a bit of money you would be sacrificing the flexibility to use your solar electricity fro anything in your house that needed it.  I doubt that that would be worthwhile.  

lohr500

I guess the challenge with feeding a DC supply into the hot tub system will be the electronics and determining which elements of the pump/heater/control modules run on what voltages and which run on AC and DC.
Another possibility could be a DIY wet solar system, diverting the pump supply to a solar water panel. But it would need manual or automatic valve control to shut off the flow to the panel when it wasn't capable of increasing the temperature.  

As per matelodave's comments, I do know that heat pumps are used on some commercial hot tub installations. Rotospa for example, offer a heat pump option. Some detail here :  https://www.rotospa.co.uk/hot-tubs-for-holiday-parks/powersmart-heat-pumps/
Trouble is, they charge £3k for the 8.8Kw heat pump, so with their projected savings of £521 per year, it is going to take close to 6 years to break even. And with a domestic hot tub there is no need to drain down and refill each week, so their cost saving is overstated as there would be less reheating of cold water in a newly filled tub.

mnbvcxz

Yes matching voltages of solar panels to heating elements might be trickier than it first appears. But perhaps you are cleverer with electricity than I. And saying that I see bimblesolar have a 600w 12v heating element. Not sure I would wish to sit in a container of water next to one, but....
https://www.bimblesolar.com/12v-600w-screw-in-water-heater


Putting a clear cover over the hot tub might let sun in but keep heat from escaping?

If you are into Heath Robinson diy solar water thermal panels come around second hand quite cheaply if you are patient. Much better efficiency than electric, about four times as efficient for the same space. If you were able to put one lower down than the hot tub you might be able to siphon the water into one and then the hot water would rise back up into the hot tub, possibly for less that £100 if you were able to do the pipes yourself. If siphon is not convenient then you would need a little pump and sensors.

You could make a basic one by coiling a black hose pipe up flat on an insulated board with a clear panel/sheet over the top. The water would then heat up in the hose. 

Small wind turbines are really quite expensive what what they do. 

good luck

TheBraes

Thanks to everyone for your comments. 😊