Discussion in 'Motoring Related Discussion' started by Tony Dyson, Oct 11, 2019.
could try this. if u have plenty of sun !
in my experience making the most of solar energy seemed to involve a few drums or avgas and a generally southerly heading !!!!
Generally it's best to use a direct thermal solar heater (as opposed to PV panels with controllers, inverters, batteries and heat pumps).
Something like these:
You can build your own with black painted copper pipe and chromed half pipes (set the black pipes at the focus for the half pipes) but ideally the whole assembly needs to be in a vacuum to maintain efficiency.
If by "more consistent output under variable real world conditions." you mean it works better in the shade then yes I've already conceded that point and your example of a low demand requirement in persistent shade is a good example.
Where is the pool, Reykjavik or Rhodes?
What is the volume of water in the pool?
How many degrees C would you want to raise the temperature of the water?
England 60,000 litres 10 degrees centigrade.
Looking to purchase something a little less homespun.
Cigarette packet calculations indicate you will need around 30m² of Evacuated Tube Solar Thermal panels south facing at optimum angles, to raise and maintain a 10° C increase in the UK, there are many variables but I need to go out today so can explain further later.
That is certainly feasible as to the size, direction and angle, thank you.
So by way of explanation of the above:
It takes 4,200 J to raise the temperature of 1 kg of water by 1°C.
∴ (Joules x Total volume of water in kG x Target temp rise in °C) = Total Energy required in J.
4,200 x 60,000 x 10 = 2,520,000,000 J Divide by 3.6e+6 for conversion to kWH, = 700
Looking at my calcs of yesterday morning, I omitted to include the target 10°C temp rise which realistically has just blown this method of heating right out of the water! So to speak My apologies for raising your hopes.
The Annual Energy output of this type of water heating in Northern Europe is around 2.5kWH/m²/Day, if you’re on the South Coast of England you could use 3kWH but you can halve these figures for the winter Months!
Due to winter temperatures and the threat of freezing, this would also need to be an indirect system with antifreeze used in the primary circuit and a Calorifier utilised with further losses, to heat the pool water.
The construction of the swimming pool is going to have a huge influence on the energy required to initially heat and maintain design temperatures as the heat losses from such a large body of water can be significant if adequate insulation isn’t provided which will need to maintain a core temperature of say 15°C for comfortable swimming at 25°C. I would be interested to know how you get on with your project, I believe Ground/Air Source Heat Pumps will be a more practical alternative.
Not necessarily. The tubes themselves are evacuated so should be ok as there is minimal head transfer from the heated water to/from the outside across the vacuum.
The vulnerable point is where the tubes join the remainder of the pipework, however if water flow is sufficient and the pipework is fully lagged the heat from the water in the system should prevent issues.
You could even use a PV panel to run the pump (with associated batteries to support overnight).
most places here use air source
While I understand what you're saying, I think you would find it at best difficult to find a Manufacturer/Installer to guarantee a water based system wouldn't freeze in winter in the UK? I think the estimated losses and additional cost would be worth peace of mind as well?
ETA And one hell of a pump to circulate 60 Tonnes of water?
Yes I think Air or Ground source will be a better option.
It's an indoor pool so heat loss should be fairly controllable for the pool itself.
That just leaves circulation of the water. The standard filter pump the pool already has should suffice as long as it can pump a sufficient head of water. Typically tat would require 4 to 6 PV panels depending on pump.
It will be interesting to see what proposals the pool designers come up with for a solution?
One other consideration is that direct solar efficiency is typically around 4 times higher than PV. The best DS is around 90% efficient compared to the very best of PV at sub 50%.
To run the entire setup from PV will need a large PV array.
Another cigarette packet calc would indicate a PV array of 72 kWH to heat the 60 T body of water over 10 Days would consist of 288 Panels making up 500m² surface area installed and costing between £100-£120K, Solar PV in the UK is also a non-starter.
At the moment we have a fairly new 40 KW system boiler going through a pahlen heat exchanger.
It raises the water around 1 degree every two hours this is an average with winter & summer variances.
Something must be off in your calculations I think.
Going to a pool heating ASHP supplier they say a 23kW Air Source heat pump is suitable for up to 110 cubic metres (110k litres). That would mean you could probably get away with 15kW. Assuming an efficiency of 2:1 that's 7.5kW of PV.
At 7.5kW using 300W panels makes for 13 panels. Add in all the support gubbins and it's about £15k.
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