I'm posting because I could not find anything on Google or this forum. If I have missed it, please link it here.

 

I have had a 15 tube evacuated 150L solar geyser setup installed that feeds my current geyser/heat pump set up.

 

The idea is to save on heating cost and have enough water to supply the house.

 

I've seen that my electricity bill never went down since the installation and I wanted to know what should I expect in terms of temperature gains from my solar geyser (with no electric heating element).

My current daily gain is around 15⁰C, with about 8⁰C losses and 1 person showering another 7-10⁰C.

This does not seem correct to me, even at this time of the year.

 

Any advice?

Edited June 30, 20242 yr by CB59

15 hours ago, CB59 said:

I'm posting because I could not find anything on Google or this forum. If I have missed it, please link it here.

 

I have had a 15 tube evacuated 150L solar geyser setup installed that feeds my current geyser/heat pump set up.

 

The idea is to save on heating cost and have enough water to supply the house.

 

I've seen that my electricity bill never went down since the installation and I wanted to know what should I expect in terms of temperature gains from my solar geyser (with no electric heating element).

My current daily gain is around 15⁰C, with about 8⁰C losses and 1 person showering another 7-10⁰C.

This does not seem correct to me, even at this time of the year.

 

Any advice?

What is the direction of the tubes on the roof? and area of installation? 

Do you have a circulation pump? 

What was your utility account in units of power per month before installation? 

Edited July 1, 20242 yr by Scorp007

1 hour ago, Scorp007 said:

What is the direction of the tubes on the roof? and area of installation? 

Do you have a circulation pump? 

What was your utility account in units of power per month before installation? 

They are due north and installed on an ibr roof with a bracket to allow slanting. Geyser above the tubes with about 45⁰ pitch (my guess, not measured).

 

I do not think I have a circulation pump (not sure how I would determine this).

 

Units were around 800-900KWh during summer and currently about 1000KWh.

43 minutes ago, CB59 said:

They are due north and installed on an ibr roof with a bracket to allow slanting. Geyser above the tubes with about 45⁰ pitch (my guess, not measured).

 

I do not think I have a circulation pump (not sure how I would determine this).

 

Units were around 800-900KWh during summer and currently about 1000KWh.

I have very little experience of solar geysers but I feel the 15° increase during the day is far below expectations. 

My guess would be at least a 200 kWh saving of your bill if in ZA. 

With geyser higher than tubes I take it a pump is not needed. 

Now over to the guys that know solar geysers to help out. 

If you get a gain of 15⁰ in the middle of winter you are doing good . The gains will be more summer time . We are offgrid but boost the geyser every day during the winter . During the summer there is a lot of days we dont boost at all .

Edited July 1, 20242 yr by Chris Louw

25 minutes ago, Chris Louw said:

If you get a gain of 15⁰ in the middle of winter you are doing good . The gains will be more summer time . We are offgrid but boost the geyser every day during the winter . During the summer there is a lot of days we dont boost at all .

Great to read a reply from someone talking out of daily use. 

If we apply figures to your experience we get to 175x15°=2625 Wh per day for a 150L geyser. This leads to about 79 kWh per month saving. My estimate was way too optimistic. 

My wrong assumption was based on the fact that solar geysers work better than PV panels from what I have read on lower irradiation days. 

Edited July 1, 20242 yr by Scorp007

3 hours ago, Chris Louw said:

If you get a gain of 15⁰ in the middle of winter you are doing good . The gains will be more summer time . We are offgrid but boost the geyser every day during the winter . During the summer there is a lot of days we dont boost at all .

That's quite interesting. It just feels like it should be more. But with what you're saying about being off grid and having to supplement, that helps in understanding my setup is not far off.

 

3 hours ago, Scorp007 said:

Great to read a reply from someone talking out of daily use. 

If we apply figures to your experience we get to 175x15°=2625 Wh per day for a 150L geyser. This leads to about 79 kWh per month saving. My estimate was way too optimistic. 

My wrong assumption was based on the fact that solar geysers work better than PV panels from what I have read on lower irradiation days. 

 

Thanks for the calculations. That helps quite a bit to put things in perspective!

On 2024/06/30 at 7:56 PM, CB59 said:

I have had a 15 tube evacuated 150L solar geyser setup installed that feeds my current geyser/heat pump set up

Something to consider is that a evacuated geyser in S.A. in summer can reach temperatures of 89 degrees celcius before its overtemperature valve opens and dumps the hot water. Feeding this heated water with such high temperature through a heatpump and into the secondary geyser might be problematic as the secondary geyser might not be able to handle 88 degree water and the heatpump might even try to cool the water down to the setpoint of say 55 degrees. I might be completely of mark but my own 200ltr evacuated geyser often in summer dumps about 50ltr of overheated water.

 

On 2024/06/30 at 7:56 PM, CB59 said:

I've seen that my electricity bill never went down since the installation and I wanted to know what should I expect in terms of temperature gains from my sol

Is it not possible that your evacuated geyser also use its element to heat water as per the timer setting? unless the element has been completely disconnected it might explain extra usage. 

55 minutes ago, Gerrie said:

Something to consider is that a evacuated geyser in S.A. in summer can reach temperatures of 89 degrees celcius before its overtemperature valve opens and dumps the hot water. Feeding this heated water with such high temperature through a heatpump and into the secondary geyser might be problematic as the secondary geyser might not be able to handle 88 degree water and the heatpump might even try to cool the water down to the setpoint of say 55 degrees. I might be completely of mark but my own 200ltr evacuated geyser often in summer dumps about 50ltr of overheated water.

 

Is it not possible that your evacuated geyser also use its element to heat water as per the timer setting? unless the element has been completely disconnected it might explain extra usage. 

Great reply Gerrie.