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Solar geyser or more panels?


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Hi guys

 

My situation has changed since my first into post here, so I thought I would ask again. I have bought a new house in Pretoria, which I plan on being in a while, so I am ready to invest in a solar system.  New house has a pool, so I know I am in for an extra R1k electricity bill per month, plus a granny flat. These additional factors make me think that the packback period is going to be shorter and therefore a worthwhile investment. If I spend R60k investment and save just the monthly pool cost, payback is just over 5 years, happy days. (this is my simplistic projections, I'm sure savings will differ from month to month). 

Anticipated daily use of around 20kWh. 

 

My intention was to go grid-tied with a PV array.  My wife wants backup for loadshedding, just on lights and limited plugs (router and maybe TV). So I was thinking of going hybrid, with a Goodwe ES 4.6kw, around 8-12 400w odd panels (for now) and a couple of lead-acid batteries (backup only, keep cost down for now).  

 

I have three questions with my intended setup. 

  • If I am investing in a system like this, is it worthwhile to get a solar (EV or plate) geyser as well? Or should I rather invest in a couple more panels, push back more into the grid during the day and stick to Eskom via Geyserwise controller before shower time? I am purely looking at cost saving, there is an installed gas geyser as backup for SHTF days. Just installing a Geyserwise TSE saved me 30% in my current house, paid itself off in three months! So if I installed the Geyserwise anyway, is it worth putting in a dedicated solar geyser?
  • If I exceed the 4.6kw load on the Goodwe while the grid is up, will I have issues? Or is this rating for backup (battery) only and unlimited when drawing from the grid?
  • What are the alternative inverters that I should look at for my intended purpose? Should I go bigger? Backup load will literally by lights and TV, maybe the fridge.

 

Thanks, I appreciate any advice.

Cheers

Craig

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27 minutes ago, gbyleveldt said:

For heavens sake don't get the Goodwe. Go for Sunsynk rather. I have a nice big rant about it here on the forum somewhere

I see you had a challenge with an update. I also had a look at the thread on the Sunsynk, will definitely consider this, thanks! At the price point, it is appealing!

Thanks for your response!

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Just my 2c worth YMMV. I always think, if you can add more panels (your inverter can handle them) then to me this is the better way to go. Make sure your geysers are heated up during the day when the sun is powering the system. Then turn off the geysers at say 5 pm until the next day. This way if your geysers are hot by say 1 or 2 pm the solar can be used else where, maybe to charge more batteries later or what ever. With Solar geyser once the water is hot, you lose the solar "power" that you could have used. If you wanted another option maybe rather look at a heat pump but I have no experience with these.

Edited by Greglsh
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4 hours ago, Craigm said:

I am purely looking at cost saving, there is an installed gas geyser as backup for SHTF days.

In my opinion most savings could come from a solar geyser, I have a liking for the EV tube high pressure geysers because I have one myself, A solar geyser would cost the least capital layout with the highest return on investment. Installing a solar inverter needs lots of capital for rather a small return on investment. Heating a geyser with a solar inverter is also a good option if you are planning on a biggish system but you will need a decent monitoring system for those high loads so that you don't damage the batteries by overloading the system. This is a more expensive option with all the eggs in one basket.

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4 hours ago, Craigm said:

I see you had a challenge with an update. I also had a look at the thread on the Sunsynk, will definitely consider this, thanks! At the price point, it is appealing!

Thanks for your response!

The challenge was/is not the update but the non existent support. The Goodwe is a great inverter, but like anything it’s possible to have issues. The brand is only as good as those that support it. Save yourself your sanity...

Edited by gbyleveldt
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Bear in mind that if you install many panels and plan to use the power as required (e.g. to heat your geyser) you will have the challenge of managing this, especially if you want this to be automated.

As  far as solar PV for your geyser have a look at the Geyserwise Dual. It is a dedicated system (3 or 4 panels) but they have a clever system of using DC direct from the panels to heat the PTC element via a MPPT. This has to be more efficient than powering a 220V geyser element from an inverter. 

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4 hours ago, Greglsh said:

I always think, if you can add more panels (your inverter can handle them) then to me this is the better way to go.

 

With Solar geyser once the water is hot, you lose the solar "power" that you could have used.

I'm with you. You lose the potential energy that you could have used once the water is at temperature. 

 

So with the goodwe and the sunsynk, can you set the inverter to stop feeding into the grid if the net effect on the meter is a credit? For example if you go on holiday and don't consume as much as normal. More panels is better, but you can have too much will will create a problem. 

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1 hour ago, Gerrie said:

Heating a geyser with a solar inverter is also a good option if you are planning on a biggish system but you will need a decent monitoring system for those high loads so that you don't damage the batteries by overloading the system.

Thanks for your feedback. 

 

When you say a decent monitoring system, do you mean on the inverter itself? If so, would the goodwe or sunsynk suffice? 

My intended backup battery load would be small, only including lights and some small appliances. 

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1 hour ago, gbyleveldt said:

The challenge was/is not the update but the non existent support. The Goodwe is a great inverter, but like anything it’s possible to have issues. The brand is only as good as those that support it. Save yourself your sanity...

100%. I must say that based on the feedback, the sunsynk is looking mighty appealing. 

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1 hour ago, Richard Mackay said:

Bear in mind that if you install many panels and plan to use the power as required (e.g. to heat your geyser) you will have the challenge of managing this, especially if you want this to be automated.

As  far as solar PV for your geyser have a look at the Geyserwise Dual. It is a dedicated system (3 or 4 panels) but they have a clever system of using DC direct from the panels to heat the PTC element via a MPPT. This has to be more efficient than powering a 220V geyser element from an inverter. 

Do you mind elaborating on your first statement?

 

I have looked at the geyserwise pv option before, but I will give this another look in the my new context, thanks! 

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33 minutes ago, Vassen said:

However, as you are planning on inverter, I recommend just adding a few extra panels and skip the solar geyser. 

Vassen, thank you for your comprehensive response. It does resonate with me. Except the 80 degree water, crikey! My geyserwise is set for 36 degrees for my showers (a bit warmer for the wife 🤣). 

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6 minutes ago, Craigm said:

Do you mind elaborating on your first statement?

"Bear in mind that if you install many panels and plan to use the power as required (e.g. to heat your geyser) you will have the challenge of managing this, especially if you want this to be automated"

There is only a certain amount of power that is available from a RE system. (As opposed to the grid!)This is determined by if the sun is shining or how much power is already being utilized on powering loads.

So to determine if there is enough available power to power a large load like a geyser you need to determine if this power available before the load is switched on. This isn't easy..

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7 minutes ago, Richard Mackay said:

"Bear in mind that if you install many panels and plan to use the power as required (e.g. to heat your geyser) you will have the challenge of managing this, especially if you want this to be automated"

There is only a certain amount of power that is available from a RE system. (As opposed to the grid!)This is determined by if the sun is shining or how much power is already being utilized on powering loads.

So to determine if there is enough available power to power a large load like a geyser you need to determine if this power available before the load is switched on. This isn't easy..

Thanks for the explanation. I'm missing something though. Using a hybrid system means that any shortfall can be taken from the grid? So if the panels generate 2kW and my load goes up to 3kW, wouldn't the additional requirement be drawn from the grid? Am I understanding correctly? 

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19 minutes ago, Craigm said:

Thanks for the explanation. I'm missing something though. Using a hybrid system means that any shortfall can be taken from the grid? So if the panels generate 2kW and my load goes up to 3kW, wouldn't the additional requirement be drawn from the grid? Am I understanding correctly? 

Sure! But what most systems try to do is to use as much PV power as possible and not use the grid/batteries if possible. This maximises the use of PV power.

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3 minutes ago, Vassen said:

Agreed. If you don’t want to use batteries during the day to manage spikes, then it will pull from grid. If you have an analogue meter, you could use the grid as a battery. 

I've been told it's an analogue meter, but haven't seen it yet. Based on this, my intention was to use the grid as a battery, with only small lead acid battery backup for lights in loadshedding. 

In this case, load vs generation balancing would be less important, right? As the meter would spin both ways, as opposed to very slowly or not at all. 

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14 minutes ago, Craigm said:

I've been told it's an analogue meter, but haven't seen it yet. Based on this, my intention was to use the grid as a battery, with only small lead acid battery backup for lights in loadshedding. 

In this case, load vs generation balancing would be less important, right? As the meter would spin both ways, as opposed to very slowly or not at all. 

There's no problem with a grid tie system. However if you want a (legal) grid tie system in SA you will find you have picked the short straw!

We are not allowed to export more power to the grid than you draw from it. Also the rate you are compensated for feed in vs drawing is very disadvantageous. Most people these days are opting for not exporting to the grid at all. This might change but for now it isn't an option.. 

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8 hours ago, Craigm said:

When you say a decent monitoring system, do you mean on the inverter itself? If so, would the goodwe or sunsynk suffice? 

My intended backup battery load would be small, only including lights and some small appliances. 

I apologize i am talking from an Axpert point of view where lot of people prefer to use ICC monitoring to protect especially batteries. I don’t have experience with goodwe and sunsynk and don’t know how they would switch and prioritize between essential and non essential loads like when load-shedding and cloudy weather happens at the same time do they protect the batteries from being discharged too much.

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7 hours ago, Richard Mackay said:

Sure! But what most systems try to do is to use as much PV power as possible and not use the grid/batteries if possible. This maximises the use of PV power.

Using excess PV power to heat your geyser is a non essential load. i.e. it can be done as and when there is available PV power. It is also a form of energy storage. Have a look at this thread which discusses this; 

 

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8 hours ago, Richard Mackay said:

Bear in mind that if you install many panels and plan to use the power as required (e.g. to heat your geyser) you will have the challenge of managing this, especially if you want this to be automated"

I agree with Richard this is the part where switching the geyser on and off is quite a challenge and to do this without interfering too much with essential loads.

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59 minutes ago, Richard Mackay said:

Using excess PV power to heat your geyser is a non essential load. i.e. it can be done as and when there is available PV power. It is also a form of energy storage. Have a look at this thread which discusses this; 

 

Thanks for the link Richard. I understand the theory, but the practical implementation is tripping me up. The automation and tinkering is above my competence (I should have studied engineering instead of finance 😂).

I now understand your previous automation comment. I would need an automated solution as I would not be able to monitor and manually switch things on and off. Plus my wife might be a little upset if I forgot 😂

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8 hours ago, Richard Mackay said:

There's no problem with a grid tie system. However if you want a (legal) grid tie system in SA you will find you have picked the short straw!

We are not allowed to export more power to the grid than you draw from it. Also the rate you are compensated for feed in vs drawing is very disadvantageous. Most people these days are opting for not exporting to the grid at all. This might change but for now it isn't an option.. 

Thanks Richard. For this reason, I do not want to overspec the number of panels. I would need to establish my load patterns first and flatten them as much as possible and aim for zero grid consumption during the day. Any feedback to the grid I would consider "bonus" and am not factoring it in to my payback/breakeven point calculations. 

Its easy enough to add panels later on if necessary. 

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2 minutes ago, Craigm said:

Thanks Richard. For this reason, I do not want to overspec the number of panels. I would need to establish my load patterns first and flatten them as much as possible and aim for zero grid consumption during the day. Any feedback to the grid I would consider "bonus" and am not factoring it in to my payback/breakeven point calculations. 

Its easy enough to add panels later on if necessary. 

What some grid tie users do is to detect any power being fed into the grid and then to throttle the inverter output power to limit this. It does seem a bit daft I agree but it's to get around the obstacles that the utilities have implemented (for what reason I still have to fully comprehend..) 

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2 hours ago, Craigm said:

Thanks Richard. For this reason, I do not want to overspec the number of panels. I would need to establish my load patterns first and flatten them as much as possible and aim for zero grid consumption during the day. Any feedback to the grid I would consider "bonus" and am not factoring it in to my payback/breakeven point calculations. 

Its easy enough to add panels later on if necessary. 

Flip side of the argument is that, with more panels, you have more power earlier in the morning and later in the afternoon. Also, on cloudy days, there's more potential PV available. All else being equal, adding extra PV panels to a system is cheap for the benefit. Futhermore, if you using a blending type inverter (Goodwe**gasp**, Sunsync), it can feed power to non-essential loads (like pool pump or geyser), even if you set grid export to zero. The trick is to set these high consumers to draw power during daytime when PV is at a peak. So, you get the benefit of PV on non-essentials without having to connect these to the backup side of the inverter. Even if there's not enough PV for a certain device on the non-essential side, the balance of what's available can still be fed to the non-essentials and the shortfall from the grid, automagically. This significance of this took me a while to comprehend, but it's this capability that sets the expensive inverters apart from the cheap ones.

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I did Not read all the replies if I say something that has been said then it just confirms 

1. Get the best inverter you can afford. No less than 5kw. 

2. Get Lithium Battery and skip the AGM or lead acids. I know it is only for backup but I can promise you that this is a better investment.

3. Get the maximum amount of panels your inverter can use. Or get a popular wattage like the 330w or something you know you will be able to get more off.

4. Ensure you have enough sun lots of people forget this part. I have a house in Pretoria with huge trees that my wife dis not allow me to cut down. With 9 panels i struggled to make 2kw. I moved to cape town and the same 9 panels push over 2,5kw from about 10-4. i make close to 12kwh a day.

5. Place as much of your house over to the solar- forget about the load shedding backup nonsense- I save around R800 pm on a small 2,4kw inverter. When I was in Pretoria my pool pump 1,2kw use to run from 10-2 on the inverter, If i wanted to use the Borehole i just switch off the pool pump. 

If you spend R100k and then save R800pm then it will take 10 years to pay back the system. 

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