The only problem is I am not loving the thought of maintenance costs.
So I have some ideas and some questions:
Firstly, it uses power to heat and filter the water, so reducing this to a minimum should increase efficiency. I am thinking I can time the on/off using one of the new wemo switches from Belkin. But I figured turning it off too much means the pool would get too cold and I would have to spend lots to reheat it. So:
We have a hard cover, but I read on a US website that you should have a floating blanket too, so I thought maybe I could make one out of say 4 layers of bubble wrap duct-taped together? Any thoughts about thermal efficiency and longevity certainly cheaper than buying one at ~$400?
One of the longevity questions is using chemicals, I have had a look on the intertubes and there is a guy in Akaroa selling ozone filters on trademe and on his website www.aquazone.org.nz. Any thoughts about whether these are good?
Thirdly, because it has been hot in Wellington and there is a roof over the spa I could put a solar collector on the roof. On the whirlpool.com.au forums I read about some principles of swimming pool solar heating, which said to use large diameter hose to and from the roof and small diameter hose on the roof to minimise heat loss during transfer and maximise heat gain on the roof respectively. I looked at the fountain pumps available and thought there is bound to be some thermal siphon effect. Could I get away with a 0.9 maximum height pump if I start a siphon (manually) and add in the thermal siphon effect? The actual height of the head will be about 2-2.5 metres.
Obviously I want a cut off for all this, so I was thinking the wemo option is probably to simplistic unless all run off the same relay or I buy more than one or they all run at the same time during the day? The alternative is a arduino to power some relays for which I probably need a temp sensor for the roof heating. I have one in the garage but I think this is going to be much more cludgy.