Solar Immersion geyser controller

[cvzyl]

My Solar Immersion geyser controller arrived a while back and I had it installed last Monday. Unfortunately we've been having some $#%^ solar power weather on the West Coast recently so today was the first day I could get a clear uncluttered graph to show how it works.

This is how my system is confibured. I've got 3kW panels connected to an Infini 3kW+ unit, the inverter has a connection from the DB and all loads in the house except for the two geysers and the oven is connected on the output of the inverter. I also have a 500Ah battery bank that I discharge by 15% every night. If excess energy is available the inverter is setup to export that, which in essence then goes to the DB. If there is no other consumers (geysers or oven) on at that time it will be exported to the municipality who will get it for free as my meter does not turn backards.

The Solar Immersion unit is installed between the DB and the geysers. It can drive two geysers, sequentially, not simultaneous, I currently have it wired only to one geyser as the other is already a solar geyser. A CT clamp is installed around the incomer (connection to municipality) through which the unit senses when you start exporting. As soon as it sees export it starts to send some power to the geyser through what they call frequency modulation. I have no idea how it works. When the geyser reaches temperature the unit can then switch to the second geyser, in my case it just stops sending power.

Below is a graph of my household power today. What you will see is:
Red line is load to the house consumers, output from inverter.
Orange line is the connection between the inverter and the DB, if it goes negative the inverter is sending power back to the DB.
The blue line is the municipal supply, if it goes negative I'm sending power to the grid.
Solar starts at around 07:00, grid and inverter lines split from load which remains constant.
At 07:30 inverter and grid reach zero and the inverter starts charging the battery bank.
Battery charging continues to ramp up as solar power increases until it reaches the maximum of 1.5kW at around 10:00, then the inverter starts exporting execess energy to the DB but the blue line (grid connection) remains zero as the Solar Immersion unit starts pushing power to the geyser. Actually the measurement shows it running negative (export) by a small amount, about 50W.
This continues until around 15:15 today when the geyser reached temperature and the thermostat switched it off, then the export from the inverter goes directly to the grid as there is no other consumers on the DB that can absorb it.

So in general the area between the blue and the orange line is the amount of power soaked up by the Solar Immersion unit.

For now the system works quite well, it soaks up any excess available so I no longer donate power to the municipality. It is not a grid limiter, if the geysers cannot absorb energy the inverter will export to grid. I can now consider adding an additional 1.5kW panels as I do not have enough panels to drive another geyser and will help to cover usage better in case of cloudy weather.

Just thought I'd give a short report is someone else might find it useful.

Cobus

[___]

4 minutes ago, cvzyl said:

frequency modulation

Probably PWM -- Pulse Width Modulation. It's basically the same thing a dimmer switch does -- slice off part of the AC wave so less energy goes through -- and then modulate that so the energy you let into the geyser more or less matches what's being exported.

Or that would be my guess.

[cvzyl]

BTW, Richard Viljoen here on the forum will be importing these units. Think he plans on keeping stock. Will save you the cursing associated with importing anything through our shit fabulous Post Office.

[Richard Viljoen]

 

Here is my graph of the SolarImmersion performance.

 

The graph shows the power flow to the geyser element.

 

I have set it up to run for an hour in the morning and evenings, for rainy days etc and to make sure my wife has a hot shower in the morning... (dont get this wrong... I learnt the hard way). Most of the time, with the geyser blanket and the hot days, it runs for much less than an hour, especially the evening run.

 

The energy flow from just after 8 is the excess power going to the geyser, you can see it ramping up with the sun. I checked on the smart meter on my main incomer and it, like Cobus, shows a slight export while the SI is pushing to the geyser.

 

The dips in power shows that the unit is only pushing the excess power. I can see that it stops whenever the kettle is put on for instance.

 

Just after 12, the geyser hit temperature and the power was pushed back to the grid. The spike before 15H00 is when someone used the hot water in the kitchen and the geyser kicked in again.

 

By my calculations, the unit pushed 3.12 kWh of solar power into my geyser for the day.

 

Would be more if I could convince everyone to shower in the evening... no chance there.

[Deonsr]

Why would you want to re-invent the wheel?

It is common knowledge that iit is cheaper to save energy than to manufacture energy. The very first thing you do is install a solar geyser in your journey towards this goal. That is why they have been designed.

I do not have the exact facts but I am sure some of the fundi's on this forum will be able to give you the figures about collecting energy from the sun, converting it to DC, charging batteries, releasing the energy from the batteries to once manufacture AC and driving a gas mongrel of a geyser element. You have cabling distance losses, dust on panel losses and the losses are enormous every time you convert something in this manufacturing line.

I can not think that the 3 kw infinty with 3,000w panels and 500Ah batteries cost you less to install than a proper 300 liter solar geyser.

 

[Richard Viljoen]

I think the advantage with the SolarImmersion and PV is that once the geyser is at temperature, you can use the rest of the power generated to save on your power bill. Something you cant do with a solar geyser. Also, if you already have a solar system (PV), the SI is significantly cheaper than a solar geyser.

One of the issues with a typical grid-tied solar PV Installation is that you can have a lot of unused solar power. The SolarImmersion is supposed to increase self consumption.

[cvzyl]

Deon, my one geyser is solar, other not. I'm not that impressed with the solar geyser anyway.

The Infini, panels and batteries were installed to power the house, convert to solar. I never said I'm doing that in lieu of installing a solar geyser. So I have the panels and inverter in any case. It's producing excess power is u send that to the electric geyser.

I'm also not using energy stored in the batteries to power the geyser. Excess energy left over after powering the house and charging batteries (I run on batteries at night, that's why I need 500Ah bank) is exported to the grid. It doesn't cost me anything to do that. And rather than donating it to the municipality I'll rather send it to my geyser thank you.

I don't want to do the debate about whether solar geysers are worthwhile, there's enough discussion on here on that already. One thing to remember though is that those panels can do more than just heat water and I can decide how to use them. The solar geyser cannot.

[DeepBass9]

Off grid tubes are way better, and much cheaper. Grid tie? Whats the payback on these heatpump and panel installations? Many years I'm sure, but a tube geyser will pay for itself in a matter of months.

[PaulF007]

I have a Low Pressure 200l Solar geyser and I must admit that , to date , I have only been impressed by it. On "Normal" days the temp goes to about 80 - 85 deg. and on bad days about 50-55 deg. Which is still perfect for shower. On rainy days like yesterday we could only get to 38 deg. So I had to run the genny for an hour to get it to 50 deg and I for one can live with that. 

If you have the spare energy and you want to use it for hot water by all means go for it.I must admit I like the idea of how they "sense" it there is power available.. Out of interest what does these units go for?

[cvzyl]

3 hours ago, DeepBass9 said:

Off grid tubes are way better, and much cheaper. Grid tie? Whats the payback on these heatpump and panel installations? Many years I'm sure, but a tube geyser will pay for itself in a matter of months.

DB, there is no way that my solar geyser installation of R17k can repay itself "in a matter of months". It saves R300 power per month so payback is more like 5 years. I didn't pay that amount myself, I was replacing a burst geyser in any case which the insurance covered and I claimed the rebate which was still available from Eskom at the time. But I wouldn't pay that outright to replace the the other geyser.

But again, for this discussion it is irrelevant. I have all the equipment already and it was bought for a different reason/motivation/excuse. I don't calculate the payback on my solar installation, it is not why I installed it. Yes, it saves me money and I try to get as much savings out of it as possible but it's sunken cost. I like the concept of solar and renewable energy, I like playing with the equipment, etc. So I have more personal payback than just the energy saving, it's also entertainment. It's sad, I know.

[Guest]

12 minutes ago, cvzyl said:

I like the concept of solar and renewable energy, I like playing with the equipment, etc. So I have more personal payback than just the energy saving, it's also entertainment. It's sad, I know.

Gee die man 'n Bell's, sommer 'n dubbel!

No, it is NOT sad, the ROI ito personal gratification? Priceless.

[DeepBass9]

But a R3k low pressure geyser would be paid back in 10 months in that case. I guess that's the difference between off grid where you have to make it work, and entertaining yourself with fancy equipment.... 

[___]

18 minutes ago, cvzyl said:

DB, there is no way that my solar geyser installation of R17k can repay itself "in a matter of months".

When I installed mine in 2011, it was to replace a burst electrical unit. Got 5.5k out of insurance and 6.5k out of the old Eskom rebate that was in place back then. Unit itself was around 14k back then. So it was 2k down... what a bargain! That paid for itself in a matter of months, it really did :-)

2 years later I re-installed an electrical geyser and turned it into a pre-feed system because I didn't have enough hot water or roof space. That sucked up around 6k, so technically I have to subtract that from the original equation, accept that 8k was really what I had to invest into that, and then... well... still not doing to badly, somewhere between 2 and 3 years.

I really don't know why we have these debates about which is better. If your objective is to make as much hot water as possible in the most efficient manner possible, you cannot possibly argue that doing it with PV is better. As others have pointed out in the past, you literally make ten times as much hot water with the flat panel or tubes. The solar geyser is undeniably better for this purpose... and there lies the rub: FOR THIS PURPOSE! If that is your objective, perhaps even your only objective.

But that is precisely not the case for some people here. It is not their only objective.

 I still think a hybrid approach is the way to go. Make at least some of your hot water in the most efficient way possible. You already know the minimum amount per day you need to keep the wife happy and the kids clean...

:-)

[Richard Viljoen]

2 minutes ago, TinkerBoy said:

If I knew what I know now I would not have wasted my money with the tubes (for our needs). I agree it all depended on your requirement. There is no one answer to all. So all we are saying is that you have to look at your requirements. We want hot water any time any condition. Tubes make a lot of hot water only when the sun is out. Heat pump makes hot water any time and we have the PV panels anyway. Thus for me the tubes was a waste. I should have just gone grid tied a lot sooner. It all depends what you have and what you want / need.

Agreed. If you have the PV anyway, reducing your power bill, but have some excess solar power or a mismatch between solar production and the load, then this system probably makes sense.

[___]

It depends somewhat on cost as well. If money (for installation and equipment) was no object, if all you wanted was the smallest possibly monthly bill, if putting Eskom out of (at least your own) business is your thing... then you'd go with some kind of combination I'd think. Given that we can't do that, because most of us don't have a money tree in the back yard, I completely understand the issue: Looking at the 18k you spent this side and thinking... man oh man... should have spent more of that on the other side.

It's like the old days when we partitioned our Unix servers, before the technology made it easier to resize on the fly. You'd always end up with too much space in one area and too little somewhere else. Changing requirements meant you never knew how it would turn out.

As for myself, the 14k spent on the solar geyser was worth it and I would do it again, even without the rebate. It gives me no trouble, and I get free hot water at least half the year. I'm actually seriously considering adding the other legs no, that is to say, also adding a heat pump, and then later also driving that with PV. If I did it again today, would I still install the solar geyser first? Absolutely.

[Guest]

23 minutes ago, plonkster said:

would I still install the solar geyser first? Absolutely.

+1 on that after +-6 years of no trouble.

Only use maybe 30 days a year Eskom to heat water. Obviously with some serious changes in habits in the household. 

[Guest]

20 minutes ago, TinkerBoy said:

I did not want to have to change any habits.

Ditto - different strokes for different folks.

Changes needed was small, no policing at all once the people understood why. For us it is about saving resources, teaching the young ones that money does not grow on trees and you need to think about scarce resources like water and that it is a luxury to have hot water for most of the world. So they need to respect it.

EDIT: And when guests arrive and stay for a night or a week, we use Eskom - more important to have a jol than to worry about R10. 

[Deonsr]

I've had my 300L solar geyser for 6 years now. The geyser burst after 4 years and was replaced under guarantee - no costs. I had to switch the element it on 4 times during this period when we had a family weekend. Other than that the best feeling to shower in hot water whwnever I want to. Best investment made ever. God helps those that help themselves. He gave us the sun above and the water below. He expects from us to bring the two together. I pump the water from my borehole with power I generate with my PV and heats it up with the sun. I run two households and use 320 units of council electricity to for all my water and electricity needs. It is possible.

 

[___]

50 minutes ago, TinkerBoy said:

I don't want to play police man all the time.

Which is probably reason number 1 why I changed all the lights to LED.

Now I yell at the kids about the fridge... because they open the door, and then it hangs open while they decide...

[Guest]

Don't let me start!!!

Teenagers / young adults shower for an hour or fill the bath to the brim, twice or more per day.
Leave all the lights on, LED's or not.
Computers run 24/7 with no-one near them.
TV + DSTV + media center on and no-one is watching.
Heater on with shorts and a T-shirt ...

No need to police them. (cwl)

[Jaco De Jongh]

Reading this just makes me realize how blessed the guys with the bigger arrays and Inverters are. Its seems like a costly exercise to convert the geyser to a solar geyser.

Since I did my R500 1kw geyser modification, I never needed Eskom to heat up my water again, not even on a overcast day. The PV produces the 1 KW with ease. 

+1 to @cvzyl for utilizing the access power on the feed side during export. Well done, it reduces the watts into your premises significantly. Its nice to be able to use your inverter both ways for your OWN load.  EDIT: Not everybody would have seen that possibility. 

[cvzyl]

14 minutes ago, Jaco de Jongh said:

Its nice to be able to use your inverter both ways for your OWN load.

Yes, my grid consumption is now less than 1kWh per day. 

[PaulF007]

The  only beef I have with heating  your geasers (Except when it is extra power) with solar panels is that the only time that you will have extra is on normal day and then my R 6500 geaser will push well into the 80 degrees. On bad weather days they are much of the much ..

But as is was said before , your money - your choice and that I respect!

[Fritz]

Heating your geyser with PV's makes room for a more flexible/adaptable/multi-functional/upgrade-able.. etc etc ....  solar system in my view. 

[___]

Possible analogy. On my father's farm there are three boreholes that are close enough to the main power line to be powered electrically. If you decide that you want to use solar power to pump water, you have one of two options: You can either replace the pumps with solar pumps and their own solar arrays... OR, you can fit a GTI at home base and pump water during the day using your surplus power.

If you go with the first approach, you get slightly better efficiency (not much, but lets grant that to make the analogy work), and you can pump water even when the power is off, but when the dam/tank is full... than the power made by those panels go to waste. If you go with the second approach, slightly more overhead, conversion losses, can't pump when the power is out, but the advantages are 1) flexibility: use the power for other things, 2) panel theft is minimised as they are close to home where you can watch them.

Pick your poison.

I have another strange idea lurking in the back of my mind: Using a solar geyser to provide heat for the tumble dryer. If you don't want to scale down on that luxury for example. Or you have kids and you rather spend money on drying the clothes than money on several sets of clothes that they just grow out of. Anyway, those are my excuses for using 3kwh - 5kwh a day on a dryer. Now with a 100 liter solar geyser, I make that much by noon. Probably go with 150 liter to account for losses. It can also be a low-pressure model, so it's really cheap to put in. If I then use the heat from that through a heat exchanger to make hot air for my dryer, would you say that is better bang for back than putting up another 2kwp of PV panels?

Once again, probably depends. Do I have anything else I can do with 2kwp of panels? Well, not really. Do I need an excuse to start another pet project? You betcha!... :-)