your comments please

[upup]

I am looking at a solar water heater and saw this for R15000 at 150 liter.

What do you think
www.onsunsolar.com/

 

[Sinbad]

From experience, get a solar twice as big as your electric.

 

[itareanlnotani]

I'd recommend at least 100L per person in the household for solar.

 

[upup]

noted

 

[Hemi300c]

I'd recommend at least 100L per person in the household for solar.

Yip agreed.
I've got a SolarTank geyser with controller 200lt and it cost 15.7k installed.
Pretty happy so far. But I wished I went for the 300lt.

 

[upup]

My plan is to keep the exiting geyser, and just add the solar with it.

I was thinking of using a water pump to circulate the water, but they say , pumps rubber don't last at heat (80 degrees).

 

[treeman]

My plan is to keep the exiting geyser, and just add the solar with it.

I was thinking of using a water pump to circulate the water, but they say , pumps rubber don't last at heat (80 degrees).

My solar evacuated tube geyser circulates hot water using this 12V pump

http://www.itssolar.co.za/its-system-components

Also something I am investigating is to use this element direct with PV for water heating .
http://www.nu-inc.co.za/nuthermo/nuthermo-titanium-elements/

 

[Sinbad]

My solar evacuated tube geyser circulates hot water using this 12V pump

http://www.itssolar.co.za/its-system-components

Also something I am investigating is to use this element direct with PV for water heating .
http://www.nu-inc.co.za/nuthermo/nuthermo-titanium-elements/

PV to electric to heat is hella inefficient. Your PV panels only do 25 or 30% or something.

 

[newviper]

PV to electric to heat is hella inefficient. Your PV panels only do 25 or 30% or something.

and in the winter/cloudy days?

 

[Sinbad]

and in the winter?

25 or 30% of that much less sun.

 

[newviper]

25 or 30% of that much less sun.

was meant for the tubes vs the PV and DC element

 

[Sinbad]

was meant for the tubes vs the PV and DC element

Tubes are much more efficient - and they're vacuum isolated so the outside air temperature doesn't affect them.
On cloudy days you're stuffed, whether it's tubes, flat panel or PV.

 

[treeman]

Using PV for heating geyser is a simple way to store the energy from PV rather than expensive batteries.
Despite the inefficiency, the solar panels produce 200-250watts each for 4-6 hrs day so I need something to use up the extra energy else it goes to waste. On cloudy days they make about 20% of rated. Also using PV may be simpler solution than a solar heat collector with all the plumbing and pipes and pumps etc...and these systems also break down (as i have experienced).

 

[newviper]

Tubes are much more efficient - and they're vacuum isolated so the outside air temperature doesn't affect them.
On cloudy days you're stuffed, whether it's tubes, flat panel or PV.

Yes I understand efficiency but what works better because the price is almost the same.
I believe the PV way will be better in more situations.

 

[Sinbad]

Yes I understand efficiency but what works better because the price is almost the same.
I believe the PV way will be better in more situations.

You don't want to hear what I have been saying, apparently.

Only way PV has a chance of coming close is if you use it to power a heatpump, NOT an element.

 

[newviper]

You don't want to hear what I have been saying, apparently.

Only way PV has a chance of coming close is if you use it to power a heatpump, NOT an element.

Can you please explain why not an element.
Should the 900W DC element for +-4 - 6 hours sunlight not be able to heat the water still just at a slower rate?
http://www.nu-inc.co.za/nuthermo/titanium-elements/

 

[Sinbad]

Can you please explain why not an element.
Should the 900W DC element for +-4 - 6 hours sunlight not be able to heat the water still just at a slower rate?
http://www.nu-inc.co.za/nuthermo/titanium-elements/

900W x 6 hours = 5.4kwh
Equivalent to running a standard 4kw element (how big is your geyser?) for an hour and a quarter.

You need 10kwh of energy to heat 150l up by 45 degrees. (Assuming your incoming water is 15, you want your tank to reach at least 60 degrees regularly, to kill legionella)

Heatpumps are more efficient - they put 3-4x the amount of heat energy into the water as they consume to do so. So 5.4kwh into a heatpump will do just fine in the above scenario.

 

[newviper]

900W x 6 hours = 5.4kwh
Equivalent to running a standard 4kw element (how big is your geyser?) for an hour and a quarter.

You need 10kwh of energy to heat 150l up by 45 degrees. (Assuming your incoming water is 15, you want your tank to reach at least 60 degrees regularly, to kill legionella)

Heatpumps are more efficient - they put 3-4x the amount of heat energy into the water as they consume to do so. So 5.4kwh into a heatpump will do just fine in the above scenario.

Thanks

 

[richjdavies]

This ^

Plus - evac tubes are like 80% efficient vs 20% or less for solar PV.

So to get 10kwh to heat water, you need either solar-pv plus heat-pump, or evac tubes (and make sure well insulated or you'll lose it all before morning - roof tanks are for people without roofs in my opinion!)... Or you could just buy it from the grid for R12/day (350 days/yr = 4000/year...).

Just remember lots of solar-evac tubes do run standard elements in the middle of the night, so arent zero cost.