Jump to content

Geyserworx PV geyser unit


Noobie
 Share

Recommended Posts

I dont know this system but having glanced through the website there is no reason that I can think of for it not to work. PV panels feeding an inverter with grid backup - output to the geyser - no problem.

Geyserwise do a system which I have used successfully, but Geyserwise uses a Titanium DC element whereas the Geyserworx system uses a standard AC element and so any geyser could be retro-fitted without the need for plumbing.

It would basically boil down <_< to the cost of the system and Return on Investment.

Link to comment
Share on other sites

53 minutes ago, pilotfish said:

PV panels feeding an inverter

Technically it doesn't need to be a very good inverter. It can make a square wave and the element won't care. It could even be a boost converter that makes 300VDC and it will work fine.

There are some people making little car "inverters" for charging phones, cheap nasty boost converters that actually make something like 150VDC, which is good enough for the average laptop/phone SMPS to work. So something like that, might be cheap enough to be cost effective even. :-)

Link to comment
Share on other sites

So they confirmed that you can purchase the controller separately and sent me the attached spec.

They suggested that I contact Voltex to get a price but the chap I spoke to at Voltex had never heard of it :blink: maybe that branch has never sold one of them?

The spec they send doesnt have a 4kw element geyser, would this be an issue, or does the element only pull as much power as the panels can produce? 

GeyserWorx Input_Output Specifications.pdf

Link to comment
Share on other sites

1 hour ago, Noobie said:

The spec they send doesnt have a 4kw element geyser, would this be an issue, or does the element only pull as much power as the panels can produce? 

It really depends how the device works. There is a good chance that it won't care, if it works in the way that I think it does (which is that it isn't really a inverter in the conventional sense, it is more of a DC/DC converter MPPT thing). According to that spec sheet, as I expected, the output is actually DC, on average 220VDC, in other words, it varies according to solar conditions.

It will likely (because of the slightly lower resistance) drive it at a slightly lower voltage, but the overall power output will be the same as with a different element.

I would however check with the manufacturer to be certain. It is interesting that the spec sheet recommends no larger than a 3kw element even for a 300 liter tank.

Link to comment
Share on other sites

On 2/20/2018 at 7:46 AM, pilotfish said:

I dont know this system but having glanced through the website there is no reason that I can think of for it not to work. PV panels feeding an inverter with grid backup - output to the geyser - no problem.

Geyserwise do a system which I have used successfully, but Geyserwise uses a Titanium DC element whereas the Geyserworx system uses a standard AC element and so any geyser could be retro-fitted without the need for plumbing.

It would basically boil down <_< to the cost of the system and Return on Investment.

You don't ^have^ to use the Titanium DC element. It's nice, but expensive. A normal element works with the Geyserwise equipment as well, but then you don't have the dual element functionality. 

Another, similar, product is www.geyserobot.co.za 

Link to comment
Share on other sites

3 hours ago, SilverNodashi said:

A normal element works with the Geyserwise equipment as well,

I am trying to wrap my head around how this would work...

The Geyserwise PV system works in conjunction with an MPPT produced for them by Microcaire which outputs 48v onto their DC element which is normally around 900w, so about 19A DC when sufficient PV power is available. If you have a 150L 3kW geyser and didn't change the element this element would have a resistance of around 3000/230 = 13ohms, connecting a 48v DC current to this element would result in about 3.7amps and a power of about 180W...?

Link to comment
Share on other sites

My thinking is that it the PV panels are connected in series giving the controller a high input voltage, and the controller also puts out a high voltage.

If I connected 6 x 250 panels in series I would have 1500watts at 220v DC.

Not really sure how it works, anyone out there have one installed?

Link to comment
Share on other sites

1 hour ago, pilotfish said:

I am trying to wrap my head around how this would work...

The Geyserwise PV system works in conjunction with an MPPT produced for them by Microcaire which outputs 48v onto their DC element which is normally around 900w, so about 19A DC when sufficient PV power is available. If you have a 150L 3kW geyser and didn't change the element this element would have a resistance of around 3000/230 = 13ohms, connecting a 48v DC current to this element would result in about 3.7amps and a power of about 180W...?

Yes. But you can also install a normal / cheap 1KW element, to get something close to their suggested figures. Going a step further, you can use a bigger, normal MPPT charger, hooked up to an element to get more heat. i.e. use 2KW PV array + 40A MPPT. It probably won't be SABS approved, but then again, I wonder how many insurance companies will approve a claim + replace the same components if you use the geaserwise product. Most insurance companies nowadays replace burst geysers with solar geysers - unless you can convince them your system is better + most cost effective, and get them to go with that. 

The geyser robot works the same way but it can take more PV panels and still work with a normal geyser element. 

Link to comment
Share on other sites

47 minutes ago, Noobie said:

If I connected 6 x 250 panels in series I would have 1500watts at 220v DC.

Aaah, but that only works if the impedance is matched properly. If the element's resistance is too low (at 13Ω it is too low), it might pull the voltage right down and you'll get way less power. So you either use your own DC element that can work on the lower voltage, or you need a DC/DC converter in the middle.

The nice thing about the converter in this case is that often you don't really have to track the power point. You know roughly at what voltage the panels work best. You know the resistance of the element. So at the cost of a little early morning and late afternoon power, you can probably use a static mark/space  ratio on the converter. Technically that makes it an MPPC rather than an MPPT :-)

Link to comment
Share on other sites

1 hour ago, plonkster said:

So you either use your own DC element that can work on the lower voltage, or you need a DC/DC converter in the middle.

...which takes you back to the Geyserwise system which has a DC element and DC/DC converter (MPPT), but with the added intelligence of the Geyserwise controller which will control DC/DC converter by switching off when the water reaches temp (have you looked for a relay that will switch 48v/20amp DC?) and allow your 230v backup to heat the water at programmable times if necessary.

I have a Geyserwise (solar-thermal) and a Geyserwise (PV) on separate geysers and I must say that the solar-thermal system delivers much better results.

Link to comment
Share on other sites

2 hours ago, plonkster said:

Aaah, but that only works if the impedance is matched properly. If the element's resistance is too low (at 13Ω it is too low), it might pull the voltage right down and you'll get way less power. So you either use your own DC element that can work on the lower voltage, or you need a DC/DC converter in the middle.

The nice thing about the converter in this case is that often you don't really have to track the power point. You know roughly at what voltage the panels work best. You know the resistance of the element. So at the cost of a little early morning and late afternoon power, you can probably use a static mark/space  ratio on the converter. Technically that makes it an MPPC rather than an MPPT :-)

So if my sums are correct the AC element has a resistance/of 14,4ohms

Its a 4kw AC element running at 240V ac

P=V*I

4000/240=14,4ohms

Would that work?

 

 

Link to comment
Share on other sites

9 minutes ago, Noobie said:

Would that work?

If you are using 6 panels in series to create 1500w and 220v then you should use a 1500w element and there is no reason not to work, but how will you control the temperature? - if you put 220v DC on your normal geyser thermostat then please DONT tell your insurance broker what you did when the house burns down!!!

You will need a suitable (read heavy duty and very expensive) DC relay to switch the power when the geyser reaches temp - you could use the normal thermostat to control the relay.

Link to comment
Share on other sites

Oh hang on, you guys are talking about direct connection to an element?

The source and the load must be matched. Let's say you put 6 72-cell modules in series, so you get roughly 220VDC. They are 250W modules, so your Imp (current at max power) is around 7 amps. Isc (current short circuit) is usually very close to the same value.

Now if you use a 1500W element as @pilotfish says, then of course you're going to get very close. But if you just stuck that directly onto a 3kw element (for argument sake), then you will work at 7A * 17Ω = 120V, and you'll only get about 850W worth of heat.

And yes, he is right... you're going to need good DC switchgear.

Link to comment
Share on other sites

If I had spare pannels I still wouldn't do it. I'd rather charge more batteries or feed it back into the grid. If I had to buy pannels and charge controller etc to heat water , I'd sit myself down for a stern talking too. Buy a set of vacuum tubes and a circulation pump and run that with your solar panels and inverter. Cost wise it doesn't make sence and the evacuated tubes work extremely well.

Link to comment
Share on other sites

On 2/24/2018 at 8:02 PM, seant said:

If I had spare pannels I still wouldn't do it. I'd rather charge more batteries or feed it back into the grid. If I had to buy pannels and charge controller etc to heat water , I'd sit myself down for a stern talking too. Buy a set of vacuum tubes and a circulation pump and run that with your solar panels and inverter. Cost wise it doesn't make sence and the evacuated tubes work extremely well.

Now you're Talking @The Terrible Triplett language ;)

At about R20 for a geyser + plumbing + controller,  it was cheaper to add more PV to my existing system and let it power the 2KW geyser element in the afternoons from 14:00, when we don't use as much PV energy anymore. And I don't have to worry about it boiling over in summer and wasting water unnecessarily. 

Link to comment
Share on other sites

23 minutes ago, SilverNodashi said:

Now you're Talking @The Terrible Triplett language ;)

You are indeed correct.

My case was simple, the tubes where much cheaper than solar panels and at the time hotwater systems where Eskom subsidized.

Going towards a decade now, not one day of trouble with the EV tubes, pump or geyser. No overheating nothing. 

If ever the system does have to be replaced, I will connect the geyser to my then bigger VICTRON inverter with a couple of extra panels to boot. 

It is proven that EV tubes are much more efficient than PV panels, unless you have a solar system already, then the costs are much more favourable for adding a few more panels using the same inverter, just put in a 2kw element.

BUT ... having said that ...

If you are in based in the Western Cape you have to keep in mind that under clouds, in winter, EV tubes preform much better than any PV system.

 

Link to comment
Share on other sites

20 minutes ago, The Terrible Triplett said:

then the costs are much more favourable for adding a few more panels using the same inverter

Indeed. Adding another 2Kwp of PV costs what now... about 13k-15k? Throw in another MPPT perhaps if you're out of capacity, that's 20k. You can get cheap solar water heating rigs for about that price... the operative word being cheap.

We may indeed be at the crossroads where it makes sense even if you don't have an existing PV system.

Link to comment
Share on other sites

Just now, seant said:

Gauteng

It's so funny that you guys have that problem more than we do these days... Funny is the wrong word actually, it's tragic. It's funny tragic. What do you call it when you experience Schadenfreude in your own situation? :-)

(I'm also still mildly amused that English has no word for Schadenfreude. And Afrikaans does).

Link to comment
Share on other sites

On 2/26/2018 at 1:43 PM, The Terrible Triplett said:

You are indeed correct.

My case was simple, the tubes where much cheaper than solar panels and at the time hotwater systems where Eskom subsidized.

Going towards a decade now, not one day of trouble with the EV tubes, pump or geyser. No overheating nothing. 

If ever the system does have to be replaced, I will connect the geyser to my then bigger VICTRON inverter with a couple of extra panels to boot. 

It is proven that EV tubes are much more efficient than PV panels, unless you have a solar system already, then the costs are much more favourable for adding a few more panels using the same inverter, just put in a 2kw element.

BUT ... having said that ...

If you are in based in the Western Cape you have to keep in mind that under clouds, in winter, EV tubes preform much better than any PV system.

 

So I am sitting at the airport, enjoying the crisp view of Table Mountain and thinking, I should have tried to come and visit, but time is against me. 

Everyone's needs differ, and thus most system designs will differ as well to fit perfectly in those needs. I live next to a dam and have seen water pipes burst in winter (we get bad frost sometimes) and I also often hear a neighbor's geyser blow off steam. A friend's gran cannot get into the shower without adding a lot of cold water. Another guy had 2nd degree burns first morning in the shower (geyser is probably 1m away from shower head). So for some it works, for some not. I prefer the flexibility and control of PV heated water

Link to comment
Share on other sites

29 minutes ago, SilverNodashi said:

So I am sitting at the airport, enjoying the crisp view of Table Mountain ...

Welcome ... hope you saved water, or brought your own!? :D

True as you say, all needs differ and not all all systems are equal. I was lucky from all I have heard.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...