Hi everyone,

We are making a move to have a total of 20x 455w panels with 2x 5.1KWh batts.

We thought this would be the best way to compensate for cloudy days to still be able to charge and provide the load with power. Nominal load during the day (house only) 350w, 1,3kw (with pool pump on), spikes with an additional 2kw when the kettle boils, which is often

On sunny days when batts are charged and the load is only 3,000w for example, and the panels are producing 9,000w is there any way of making use of the "wasted" power? Any chance of feeding back to grid in JHB?

Thanks so much!

Edited September 21, 20223 yr by Gavin286
more info

I would install a Smart switch to supply your Geyser with power from Solar System.

8 hours ago, Gavin286 said:

On sunny days when batts are charged and the load is only 3,000w for example, and the panels are producing 9,000w is there any way of making use of the "wasted" power?

Welcome to the stresses of self generated solar power😂. I think there are thousands of us in the same boat we don’t know what to do with the excess power. Once batteries are at 100%, geysers are on temperature and inverter set to Export “Off” I just think Eskom why?

9 hours ago, Jacques Ester said:

I would install a Smart switch to supply your Geyser with power from Solar System.

Having 9000W generated would normally heat a 150L geyser with 3kW element within 0.5 to 2hrs. This still leaves 4 or more hrs with wasted PV. The price one pays to have enough power on cloudy/rainy days.

Water heating is most definitely the most expensive item, so I would start with that. 

Do you have enough hot water after hours? Maybe install an extra 100 liter geyser inline to feed your existing geyser., but you put a timer on it and only heat it up after lunch. Good way to have a good reserve of hot water without extra cost

This way you will have tons of hot water without your main geyser coming on and using Eskom power at night

Edited September 22, 20223 yr by Operator

Thanks everyone for the replies and suggestions. I do have an element based geyser but with a solar heat exchanger so it uses minimal power to keep temps. But to have it running permanently on PV for that slight requirement is a good idea!

6 minutes ago, Gavin286 said:

Thanks everyone for the replies and suggestions. I do have an element based geyser but with a solar heat exchanger so it uses minimal power to keep temps. But to have it running permanently on PV for that slight requirement is a good idea!

TIP: Use geyser as energy storage.

I also have a Solar Water geyser.
I used the recommended GeyserWise timer schedule of turning on electricity at 4pm-6pm and 4am-6am to heat the water to 65°C.
The theory was to let the sun heat the water during the day.
If it was a cloudy day, the 4pm-6pm schedule would ensure we had hot water for the night.

I read somewhere of using your geyser as a "battery" so I recently added a 3rd early schedule at 10:30am-12:30pm.
At 10:30am, I normally have enough PV (4.5kWh) to power the house ~1kW and heat the geyser ~3kW and a little bit of head room.
The trick is to have enuf PV at 10:30am to heat water and not draw from the battery.
This uses Solar PV electricity to get the geyser to 65°C.
The the sun then further heats it in the midday+afternoon to 75°C.
Even when we use hot water in the evening, we generally don't need to heat it in the 4am-6am slot since the starting point was 75°C.
This has mostly eliminated the 4am-6am slot.

The other option is to only use hot water once per day (all bath in the evening or morning).

TL;DR: add a 10:30am-12:30pm electricity schedule to your solar geyser.

22 hours ago, Gavin286 said:

Hi everyone,

We are making a move to have a total of 20x 455w panels with 2x 5.1KWh batts.

We thought this would be the best way to compensate for cloudy days to still be able to charge and provide the load with power. Nominal load during the day (house only) 350w, 1,3kw (with pool pump on), spikes with an additional 2kw when the kettle boils, which is often

On sunny days when batts are charged and the load is only 3,000w for example, and the panels are producing 9,000w is there any way of making use of the "wasted" power? Any chance of feeding back to grid in JHB?

Thanks so much!

Good question! What about heating the pool? Is that possible? I know it's summer and maybe you're not that old but my pool is only warm enough for like a few weeks in December. I suppose a pool heating thing costs another fortune 😂

40 minutes ago, MKRandburg said:

Good question! What about heating the pool? Is that possible? I know it's summer and maybe you're not that old but my pool is only warm enough for like a few weeks in December. I suppose a pool heating thing costs another fortune 😂

That is a very good suggestion. We were considering a heat pump but decided against it BEFORE we had funds available for more panels, so we put in traditional water solar for the pool already...

45 minutes ago, MKRandburg said:

What about heating the pool?

Thats exactly what I did. Pool has been at 28 degrees since the first weekend of September.

16 minutes ago, Gavin286 said:

That is a very good suggestion. We were considering a heat pump but decided against it BEFORE we had funds available for more panels, so we put in traditional water solar for the pool already...

We had one of those but it died and we haven't replaced it but we thought seeing we're going solar we might rather get a heat pump. But probably a way aways from having excess solar... but without a battery to store it in, it might still be an option for us. Hmmm 🤔

1 minute ago, MKRandburg said:

We had one of those but it died and we haven't replaced it but we thought seeing we're going solar we might rather get a heat pump. But probably a way aways from having excess solar... but without a battery to store it in, it might still be an option for us. Hmmm 🤔

I just googled the prices... I don't think so! Because of course we have a ginormous pool, built in the 70's when water and power was considered infinite.

2 minutes ago, MKRandburg said:

We had one of those but it died and we haven't replaced it but we thought seeing we're going solar we might rather get a heat pump. But probably a way aways from having excess solar... but without a battery to store it in, it might still be an option for us. Hmmm 🤔

If you're wanting to go the heat pump route, I would recommend Fourways Online. They were very helpful and interested in helping me even though I didn't end up buying anything from them. Here is a link to what I was looking at: https://fourwaysonline.com/product/12kw-alliance-inverter-swimming-pool-heat-pump/

Instead of adding heating, why not add more cooling? At least the types of loads where your demand increases with greater sunshine. Like aircons everywhere. Or some extra fridges and freezers and open a neighbourhood food storage service?

If you're Rockefeller, then an EV and enough battery storage to maximize energy production and transfer to the EV, when the EV's back in your motorpool at home 🙂

On 2022/09/21 at 8:30 PM, Scorp007 said:

Having 9000W generated would normally heat a 150L geyser with 3kW element within 0.5 to 2hrs. This still leaves 4 or more hrs with wasted PV. The price one pays to have enough power on cloudy/rainy days.

This is a very good point. You need to not think about when the sun is shining, but about when the sun ISN'T shining. As @Scorp007 says, having excess on clear days means you have some headroom for overcast days.

Also your panels won't produce 9000W all the time. They will peak at that, but as the afternoon proceeds you will see their output dropping off.

Don't count your chickens before they hatch. Get that system installed and observe it for a while, and make sure you really do have that excess available. In my case this was easy because we have a 2nd geyser that we never use, so I waited until the batteries were charged on a nice clear day, and then turned that geyser on. The load forces the system to start drawing more PV, so I got a good idea of what was available.

Something else I thought about. Hot water should normally be just one of our daily loads. Once we have covered them and the battery is charged - is this not the point that we can say we have excess PV available. This means starting to dump the excess into the geyser is already taken care of.

Just a thought 🤔🤔🤔

Edited September 23, 20223 yr by Scorp007

I've been thinking of changing the battery to on grid discharge to a DOD of 80+%, if the weather forecast for the next day is sunny.  If forecast  = cloudy/rain set to 40% DOD discharge.  The intention is to create "space" to charge the battery with "excess" power.

15 minutes ago, BGb said:

I've been thinking of changing the battery to on grid discharge to a DOD of 80+%, if the weather forecast for the next day is sunny.  If forecast  = cloudy/rain set to 40% DOD discharge.  The intention is to create "space" to charge the battery with "excess" power.

Makes sense. It might get tiresome to keep watching the weather though.

Check out this solution I am developing. Link

GitHub

GitHub - pietermullertrust/Geysermen: Control Deye/SunSyn...

Control Deye/SunSynck Inverters to monitor and dump excess solar power created into geysers - pietermullertrust/Geysermen

Adding an air conditioner or three to your house would soak up quite a lot of excess power whilst keeping your house nice and cool in summer, or nice and hot in winter... I'm planning on doing just this before next spring...

Damn... who would have thought before installing PV that we would be looking for ways to use more electricity, and not less... 😁

I ponder this from time to time. Most days I have power to spare.

Now on the plus side this means that my inverter is not taking much stress, which can only be a good thing.

But it seems to me that the best use of this surplus electricity (since it would cost me money to feed it back in to the grid) is to charge another battery. Then I have more power at night, more in reserve for cloudy days or when there's an outage.

1 hour ago, Bobster. said:

I ponder this from time to time. Most days I have power to spare.

Now on the plus side this means that my inverter is not taking much stress, which can only be a good thing.

But it seems to me that the best use of this surplus electricity (since it would cost me money to feed it back in to the grid) is to charge another battery. Then I have more power at night, more in reserve for cloudy days or when there's an outage.

Just to use the wasted PV to cover the 10 or so bad days in summer has the worst ROI. It's just like most nice to have items. One thinks you really need it at the time of buying.

If one looks at my winter yields they are close to the good summer days as it means my battery is just fully charged a hour later.

In your case it could mean you just end the night at 80+% compared to now? depending on your current battery size.

It's a vicious cycle. Produce too much PV and search for ways to spend it, then you cannot produce enough anymore to feed the new sources, so you expand the PV.

Battery is the most sound, it means you saved the PV IF you need it later for whatever reason, but this is only if money allows. I have not adjusted our power usage at all or our ways of doing things, thanks to large batteries, and we do not use the grid at all. So if you are currently using the grid at all, then this is the best.

If you want to really use the PV, you would need smart devices. Mine goes like this.

Home usage supplied first, then the batteries, and if the PV production is more than 1kw, turn on the geyser, if that is heated (smart device amps are 0), turn on the pool, just before PV tapers off, turn on the sprinklers.

I still lose around 10-20kw a day, but it's room for expansion later.

Edited May 30, 20251 yr by Pho3niX90