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Heating water from PV system


Tony Swash

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9 minutes ago, DeepBass9 said:

two 150l tube geysers

what is a tube geyser :ph34r: pardon my ignorance... if it is a solar geyser heated with vacuum tubes i would say you are going over-board with the heat exchange idea in as far as ROI is concerned, not?

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2 minutes ago, gabriel said:

what is a tube geyser :ph34r: pardon my ignorance... if it is a solar geyser heated with vacuum tubes i would say you are going over-board with the heat exchange idea in as far as ROI is concerned, not?

EV tube geyser.

Not really, it will mean that I will have hot water on cold overcast winters days, which is priceless! Also it is just some piping and lagging so I can probably build it for about R1000.

Edited by DeepBass9
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5 minutes ago, gabriel said:

just take care of possible hail storms, i see you guys had a tornado in 2016... tubes are great, but not for hail

I've had tube geysers on our cottages for years, I currently have 5 installed and have not lost a tube to hail ever, and we have had some heavy hail, so that is not really a consideration. A tube costs about R100 so cheap to replace if you do break one.

Edited by DeepBass9
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3 hours ago, DeepBass9 said:

Not 10x better. A 30k geyser wont make water 10x hotter than a R3k geyser, neither will it last 10x longer.

My neighbor had the opposite experience. One of his houses had a cheap solar geyer, their main house had a much more expensive one. The more expensive geyser gave less trouble, had to be serviced less frequent and, he said, it produced hotted water throughout the year. The houses are about 2km apart. 

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1 hour ago, SilverNodashi said:

produced hotted water throughout the year

I can also confirm that. I have a system that cost me around 14k. It's a fibreglass tank (X-stream) with a locally made flat-panel collector (made in Kleinmond apparently). Works brilliantly in summer and does most of the work between October and April. From May to September you see an uptick in electricity use.

A colleague installed a solar geyser maybe 6 months later. Spent about 28k on it. His makes hot water through the year. Flat panel... not even EV-tube.

Now I still think there is a price/performance balance somewhere. At some point, the extra 10k you pay does not buy you enough extra hot water/electricity savings for it to be worth it. Which is why I like the heatbox idea. Do half or more of the work with the sun... finish it up with a bit of electricity (which can be PV-derived).

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5 hours ago, plonkster said:

I can also confirm that. I have a system that cost me around 14k. It's a fibreglass tank (X-stream) with a locally made flat-panel collector (made in Kleinmond apparently). Works brilliantly in summer and does most of the work between October and April. From May to September you see an uptick in electricity use.

A colleague installed a solar geyser maybe 6 months later. Spent about 28k on it. His makes hot water through the year. Flat panel... not even EV-tube.

Now I still think there is a price/performance balance somewhere. At some point, the extra 10k you pay does not buy you enough extra hot water/electricity savings for it to be worth it. Which is why I like the heatbox idea. Do half or more of the work with the sun... finish it up with a bit of electricity (which can be PV-derived).

At R30k I could still retrofit a 300L geyser and have some change. And I don't need to worry about extra plumbing or wasting hot steam in summers. 

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On 2019/03/13 at 11:11 AM, gabriel said:

... tubes are great, but not for hail

If it happens it is an insurance claim. 🙂 

Just check with your broker / insurer.

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  • 3 weeks later...
On 2019/03/12 at 8:37 AM, SilverNodashi said:

Unless you have free excess PV power to re-purpose for water heating. A cheap solar geyser will cost say R17,000+ A decent one with long lifespan will set you back about R30k. 

I already had the inverter solar panels and batteries in place for electrical usage. And now I am use excess, unused, wasted solar energy. My geyser doesn't run off batteries though, it's straight from PV - > 220V through the inverter. Even with the losses, how is that more expensive than thermal water heating? 

Hi there

Newbie seeking advice

I currently have a system in place 3.96 solar array, with 9.6kw battery back up, 5 kW goodwe inverter. Please can you let me know if I need a seperate DB board or another inverter to run my geyser straight from my PV and not batteries.

You also mentioned changing the geyser element. Kindly tell me the steps.

I'm told that to max PV usage the geyser must be connected to battery back up alternatively I have to use Eskom directly only.

This seriously drains my batteries when cloudy, sometimes no night back up at all. Ideally I would like to use excess power to supplement grid feed and not battery. Is this possible?

At least this way I still have my full battery for night use configured to 70%DOD.

I would appreciate all advice as I don't know what to do.

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Yeah I know😬 but I want to know what my options are to minimise grid usage for now:

In the interim, can excess power to supplied to support the geyser without the battery being involved? Is there a setting etc? Or is that not possible?

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8 hours ago, xinath said:

Newbie seeking advice

the guys here will be able to give you a lot of advice - some of the advice is already in older posts so youll have to dig a bit - but you will have to spell out exactly what you have in place at present as well as your wants and needs [take note the latter differ from each other] - also state what you have done so far to cut your electricity consumption, i.e. replace light bulbs, use less warm water etc 😃

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Thank you Gabriel, I have mentioned what system I have right now hybrid 5kw goodwe, 3.96 solar and 9.6 pylon.

I don't have additional cash right now to change to solar geyser, however I want to know what I can do to minimise the use of the grid to power my electric geyser😬

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8 hours ago, xinath said:

Hi there

Newbie seeking advice

I currently have a system in place 3.96 solar array, with 9.6kw battery back up, 5 kW goodwe inverter. Please can you let me know if I need a seperate DB board or another inverter to run my geyser straight from my PV and not batteries.

You also mentioned changing the geyser element. Kindly tell me the steps.

I'm told that to max PV usage the geyser must be connected to battery back up alternatively I have to use Eskom directly only.

This seriously drains my batteries when cloudy, sometimes no night back up at all. Ideally I would like to use excess power to supplement grid feed and not battery. Is this possible?

At least this way I still have my full battery for night use configured to 70%DOD.

I would appreciate all advice as I don't know what to do.

I currently have a 2KW PTC element (works more efficient than a normal element) in my geyser, with a Geyserwise timer running from 14:00 to 18:00. The water is generally 58 degrees by roughly 16:30 and then it switches off.

I would move the geyser feed to the other phase so it can run off excess solar which is fed from the Goodwe during the day, presuming your DB board is already split in two. Or does the Goodwe run your whole house?

To change the element, get in the roof, switch off your geyser, drain the geyser and remove the element, and replace with a new one. I would caution though, that you might need a plumber if your house has a geyser COC, or if you really feel uncertain about this. 

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11 minutes ago, xinath said:

In the interim, can excess power to supplied to support the geyser without the battery being involved?

it seems your geyser is wired to your pv system - no comments as to the genius who did it - 1st will be to get it back to grid OR get a 1kw element in there and setting the timer for good sunlight hours [or manual if you have a cloudy day] if it still is on the pv with a 1kw element. now that this load is taken care of i am sure your batteries will carry you through a patch of load shedding if you don't stress them out.

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5 minutes ago, xinath said:

however I want to know what I can do to minimise the use of the grid to power my electric geyser

I guess the best you can do is to put the geyser on a timer and program the Goodwe not to use the batteries during the time the geyser is on. The best time for the geyser to heat would be early afternoon when the batteries are fully charged. I would also change the element to a 1 or 2 kW type.  

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