Solar Geyser - Why not?

[richjdavies]

Only thing to add... A solar geyser will produce much more heater per meter than a DC solar panel.
I.e. best Solar PV is about 20% efficient -- so 1kWh of sun -- 0.2kWh of electricity. Whereas solar heat is more like 80%. This means if you plug it straight into your geyser (i.e. not use a heat pump) you'd need 4x the square meterage of solarPV than you would with solar vacuum tubes.

Problem is the solar geyser means you have a big radiator on your roof losing energy all day and night too... So the 4x gathering heat ends up being much less as a full system over time. Bad solar geysers can be net negative (particularly as they have elements that kick in in the morning... So if you don't use water at the right time you might end up basically heating your roof with electricity with no net gain in hot water!)

I'd say those DC panel kits are not great to be honest. Bet they are second rate panels and so when you go full blown solar you'll still replace the panels.

In short -- if you go solar heat -- then make sure it's a good install and monitor your element usage, maybe even changing your hot water usage patterns. If you go solar PV, I'd shy away from the Converter kits myself. Better to wait and save and go full blown solar into your whole house.

Best investment -- making sure your geyser is as efficient as it can be!

 

[SauRoNZA]

Only thing to add... A solar geyser will produce much more heater per meter than a DC solar panel.
I.e. best Solar PV is about 20% efficient -- so 1kWh of sun -- 0.2kWh of electricity. Whereas solar heat is more like 80%. This means if you plug it straight into your geyser (i.e. not use a heat pump) you'd need 4x the square meterage of solarPV than you would with solar vacuum tubes.

Problem is the solar geyser means you have a big radiator on your roof losing energy all day and night too... So the 4x gathering heat ends up being much less as a full system over time. Bad solar geysers can be net negative (particularly as they have elements that kick in in the morning... So if you don't use water at the right time you might end up basically heating your roof with electricity with no net gain in hot water!)

I'd say those DC panel kits are not great to be honest. Bet they are second rate panels and so when you go full blown solar you'll still replace the panels.

In short -- if you go solar heat -- then make sure it's a good install and monitor your element usage, maybe even changing your hot water usage patterns. If you go solar PV, I'd shy away from the Converter kits myself. Better to wait and save and go full blown solar into your whole house.

Best investment -- making sure your geyser is as efficient as it can be!

How do you measure 1kWh of sun?

Are you saying a 500W panel only generates 100W of energy?

 

[Speedster]

How do you measure 1kWh of sun?

Are you saying a 500W panel only generates 100W of energy?

No, I think he's talking about the panel efficiency i.e. how good is the panel at converting irradiance into electricity / heat. Solar geysers are certainly far more efficient (i.t.o. energy generated per m2), but not necessarily cost effective.

 

[dj_jyno]

I would go for solar. At our previous house with a 300L geyser and evacuated tubes, from October to March the geyser element would virtually never switch on.

 

[richjdavies]

How do you measure 1kWh of sun?

Are you saying a 500W panel only generates 100W of energy?

All panels are rated by the power they produce when they get sunlight of 1kW/sqm. This is a nice ball park figure, but actually you get more than that at midday in SA!

So a 500W panel like below. It it 2.1m X 1.1m =2.3sqm. 500W / 2.3sqm = 210W / sqm.
210W electrical power from 1000W of Sun (all per sqm)
That's exactly what it says in the spec sheet - 21% efficiency!

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[GrootVoet]

So before deciding which way to go consider the following.

• How much warm water would you like to store, the more you use the larger you want to go.
• Flat plate or tubes, tubes are better at heating but they also overhead much faster so if you live in the middle of the Karoo maybe not tubes. Then you also can get fancy with oil filled coils that is expensive and need maintenance.
• Do you keep your existing geyser and just add a panel with a pump or do you add a second geyser. In the second config where do put your element.
• Properly most important in my opinion is what is your usage pattern. You want to use warm water from the solar geyser while the sun is shinning. If you only shower once a day early morning you likely would need to heat with electricity because overnight things cool down unless you have good isolation.

In my case we use warm water twice a day, in the evening when we use the water heated during the day and in the morning where we need to heat water because we used all the warm water already. In the summer this is less of an issue.

So do your homework, lots of info and opinions available online.

 

[GrootVoet]

Nope- was said only using 2kWH LESS per day.. so basically was a waste of money. R5 per day saving - R150 per month R1800 per year - so 10 Years to break even, and solar systems also require maintenance and often repairs after a few years.

The thing is my geyser usage before the solar was not that much, I did not know that. So my savings after solar was not as expected. Also during winter here in the Cape the solar on its own is not sufficient.

 

[SlinkyMike]

Three consecutive overcast days.

 

[Speedster]

Nope- was said only using 2kWH LESS per day.. so basically was a waste of money. R5 per day saving - R150 per month R1800 per year - so 10 Years to break even, and solar systems also require maintenance and often repairs after a few years.

Is using less per day not saving? Do I need to replace my dictionary?

 

[Stokstert]

Do you guys rely solely on the solar to heat the water or do you have a timer or boost from the grid?

I don't need to boost my solar geyser winter or summer except on a rainy day when we have less than 3 to 4hrs of sun.
Since the installation 138 months ago, we used 3857 kWh which gives an average usage per month of 27,9 units. This is more or less 10% of the original cost per month.
The usage is measured by an OWL meter connected from day one.
Our power usage before the installation was between 250 and 300 units per month, metered for twelve months before the installation.
The Geyser Wise controls boosting on rainy days.
The installation cost of ~R24k was subsidized by Eskom with ~R12k.

 

[richjdavies]

So... Step 1.
Understand how much your geyser actually uses.
Get a CBI WiFi timer, and it will tell you.
When you are away for a weekend or something check how much it used.
That will tell you if it's a leakage or standing loss problem or a usage problem.

 

[RudderVator]

I think we've sung this chorus 1000 times. And they still don't listen...

Plenty people seem to find it really difficult to even understand the difference between water solar panels and PV panels for electricity.

To them solar means solar.

 

[richjdavies]

Plenty people seem to find it really difficult to even understand the difference between water solar panels and PV panels for electricity.

To them solar means solar.

It's slightly deeper than that.

It's "I have this problem"...
Can I chuck money at it and salesman will be honest with me and my problem will go away
Great!

Unfortunately the world doesn't work that way. There's plenty of people who will take your money and overpromise. For most people it's just too much effort to understand their situation, as it involves maths and stuff...
But mybbers ain't normal people!

Hurrah!

 

[Andrew001]

Sure this is my setup.

I paid R30k to pop those solar geysers in a year before I went solar (happened sooner than expected)

That R30k cost more than my entire solar array and would benefit the whole house.

I specifically said if you going full solar DONT get the solar geyser. As you cant in your case the solar geyser is fine.

View attachment 1362793

That brick trim around the windows!

 

[Snyper564]

That brick trim around the windows!

haha the house came like that next years problem

one renovation at a time

 

[Mike Hoxbig]

haha the house came like that next years problem

one renovation at a time

Do the burglar bars as well. I never understood why people put it on the tiny windows that open, but leave the giant fixed window exposed. If they're armed, they're going to break that thing, they don't care if you hear it...

 

[noxibox]

Do you guys rely solely on the solar to heat the water or do you have a timer or boost from the grid?

We use some electricity for water heating for the three months of winter. The rest of the year it is entirely heated by the sun. We use the same target temperature all year round and hot water usage is about the same regardless of the time of year.

 

[Spizz]

We use some electricity for water heating for the three months of winter. The rest of the year it is entirely heated by the sun. We use the same target temperature all year round and hot water usage is about the same regardless of the time of year.

Thanks for the info. I've been getting used to our habits and have tops up for an hour at 7pm and an hour at 5am. That has been diminishing a little just now with the warmer weather so interesting to see how this pans pout now.

But I've got loadshedding from 2 till 4.30 this afternoon and it's a beautiful sunny day. Going to run the hot water down at 1.45 as I'm still panicking a little about the collector getting too hot.

 

[Speedster]

Thanks for the info. I've been getting used to our habits and have tops up for an hour at 7pm and an hour at 5am. That has been diminishing a little just now with the warmer weather so interesting to see how this pans pout now.

But I've got loadshedding from 2 till 4.30 this afternoon and it's a beautiful sunny day. Going to run the hot water down at 1.45 as I'm still panicking a little about the collector getting too hot.

Cold water in the geyser won't affect the collector temp. You need the water in the collector to circulate to avoid over heating.

 

[Snyper564]

Thanks for the info. I've been getting used to our habits and have tops up for an hour at 7pm and an hour at 5am. That has been diminishing a little just now with the warmer weather so interesting to see how this pans pout now.

But I've got loadshedding from 2 till 4.30 this afternoon and it's a beautiful sunny day. Going to run the hot water down at 1.45 as I'm still panicking a little about the collector getting too hot.

if this time of year is concerning for you December is going to be a nightmare for you...