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First Investment in Solar


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9 hours ago, Richard Mackay said:

Is there a possibility that you can overload your PV supply?

Not sure about the question ether.  RikH and I have the same inverters, and here's my take on it...

The two MPPTs on the inverter are rated at 5kW & 900V each for a total of 10kW.  I have two 4kW series strings (about 500V) so I presume they are fine.  The inverter itself can deliver 5kW at 220V and another 5kW at 48V, thereby fully utilising the 10kW of PV input.  I've heard that it's OK to exceed the maximum PV wattage rating as long as you remain within the maximum voltage limit, but I am not that guy.

In grid-tied mode it can blend utility power if the load exceeds 5kW, but in off-grid mode the 5kW load load cannot be exceeded (as I learnt by welding during a load-shedding episode!).

The battery charger is always limited to 5kW because of its 100A max rating - no grid blending is possible.

Does that make sense?

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Apologies! My question was not clear. I am trying to get my head around the way you can use all the PV power that is available all the time. Inverters will use another power source if the PV can't supply the power. This is fine for essential loads. 

wenotgood has this smart device that utilizes all the PV power available but I don't know the details. As I understand it the device determines the amount of power fed back into the grid (in a grid tie system) and will divert power to another load (geyser) to minimise power being fed back into the grid.. 

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On 2020/09/04 at 10:20 PM, Richard Mackay said:

I presume this is a grid tie system?

Hi Richard, yes it is,

As per the other posts, also had the one geyser on a Geyserwise timer which does help but is not nearly as "precise" as the Apollo Gem in using the energy that would be otherwise exported.

We also now have two geysers connected to the Apollo GEM which makes it much more worth our while.

Additionally the Apollo GEM unit can also be fitted with temp sensors, which then replaces the Geyserwise.

So if I could do it all again I will rather use the money spend on the solar heating and Geyserwise (which was a mess in our case with water leaks etc.) and just install the Apollo GEM. This way you can also save on batteries as the Geyser becomes a massive battery.

ApolloGEM.thumb.jpeg.c1b499ac5ca682f53452d2d28a80f805.jpeg

Edited by WeNotGood
correction
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On 2020/09/06 at 9:15 PM, Richard Mackay said:

As I understand it the device determines the amount of power fed back into the grid (in a grid tie system) and will divert power to another load (geyser) to minimise power being fed back into the grid.. 

Yes, spot on, it uses a current clamp and then increase the power and send it proportionally to the geyser(s) or other resistive loads as you export more or decrease it proportionally when you export less, or switch it off when there is no excess energy produced.

On the GEM you can also set an output with a threshold limit e.g. when the exported energy rise above 1kWh you can switch on a load, like your washing machine, in this case however the output will not be proportional as you cannot run the washing machine on a proportional supply.

 

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When I started looking into this option only the Solic200 and the Apollo GEM was available in SA that I was aware of.

There are many other available, especially in the UK that can do all sorts of really clever stuff, however found the GEM to be a good balance between features and price.

https://www.apollosolarelectric.co.uk/products/

Edited by WeNotGood
typo
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On the below picture it shows quite nicely how the load (Purple) to the Geysers increases and decreases with the PV production (Blue) during a cloudy day, the part circled in red where the purple line overshoots the blue, is when one of the Geysers, was set to switch on, using the Apollo GEM's timer.

ApolloGEM-Track.jpg

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On 2020/02/19 at 5:59 PM, Vleis said:

I've contacted a company that proposed the following solution:
* Sunsynk 8kW Hybrid Inverter

The possibilities you have with a hybrid inverter are a whole lot greater than the older grid tie inverters (which I have)

It's amazing how complex these systems get so one wants the maximum flexibility possible. 

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32 minutes ago, Richard Mackay said:

The possibilities you have with a hybrid inverter are a whole lot greater than the older grid tie inverters (which I have)

Units like the Apollo GEM will also work with Grid tied systems, using the geyser as the "battery" in fact that is how they were used initially in the UK market.

When they started to implement their FIT (Feed in Tarrifs) a basic energy meter was connected to the Grid Tied inverter output and it would be assumed that 50% would be exported, so you would receive 50% of what was generated irrespective of what was actually exported.

These proportional Geyser outpust systems were then used to uses as much of the generated PV as possible while being paid for a 50% export.

They have since started to roll out smart meters so that trick no longer works everywhere, the units are still useful however.

 

Edited by WeNotGood
correction
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2 hours ago, WeNotGood said:

Hi Richard, yes it is,

As per the other posts, also had the one geyser on a Geyserwise timer which does help but is not nearly as "precise" as the Apollo Gem in using the energy that would be otherwise exported.

We also now have two geysers connected to the Apollo GEM which makes it much more worth our while.

Additionally the Apollo GEM unit can also be fitted with temp sensors, which then replaces the Geyserwise.

So if I could do it all again I will rather use the money spend on the solar heating and Geyserwise (which was a mess in our case with water leaks etc.) and just install the Apollo GEM. This way you can also save on batteries as the Geyser becomes a massive battery.

Thanks for this. This is a tricky topic (not helped by the powers that be at CoCT!)

You don't specify which Geyserwise system you have. I was impressed by their Dual system that uses a mains element and a PTC element that is powered by 3 or 4 PV panels. It's a clever system that uses DC to heat the water (and a MPPT). So it's more efficient not having PV power converted into AC before it's used to heat the water.

The only thing that put me off is that you can't easily redeploy the PV panels when the water is hot.. (But the jury is still out as to whether I buy one)  

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Also looked at their system with the PTC element for the second Geyser (which is in a flat, attached to the house we rent out).

We have the Geyserwise Delta T, with the circulation pump, which is another pain during load shedding as the pump did not work during loadshedding.

The advantage of the Apollo GEM and similar is that you can really get the maximum out of your system in term of self use, before we had the Apollo GEM our self use was around 50% during summer and 70-80% during winter, now it is >90% during winter and expect it to be >70% during the summer.

From other people's replies re CoCT, they do ironically seem to be more of a hindrance than a help, especially with getting people weaned of Escom but then again it is probably in their own interest to restrict people as much as possible when it comes to renewable energy.

With the limits CoCT impose it may be difficult to fully optimise a system, but CoCt restrictions aside, knowing what I do now,  I would not consider a Geyserwise again but rather increase the capacity of the PV system with a Apollo GEM or equivalent and/or add battery storage with the Geyserwise money or even another Geyser in series to be heated with the excess energy.

Edited by WeNotGood
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1 hour ago, WeNotGood said:

From other people's replies re CoCT, they do ironically seem to be more of a hindrance than a help, especially with getting people weaned of Escom but then again it is probably in their own interest to restrict people as much as possible when it comes to renewable energy.

I cannot follow the reasoning of CoCT. I don't know if they have tried too hard to explain why they impose the restrictions they do. (My suspicion is that it's bureaucracy at work!) Other countries that had a massive increase in solar PV systems (due mainly to incentives) resulted in an oversupply of power into the grid during bright sunlight conditions. This has the undesirable effect of making the grid unstable.

There's no way we are experiencing this phenomenon so I'm still waiting patiently to hear the low down..

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There surely are many excuses being proposed as reasons 🙂

On a Macro level, having many residential SSEG's (Small Scale Embedded Generators) that contribute to the grid during the day will alleviate some pressure on ESKOM and allow industry to use the additional capacity to help grow the economy out of the current mess.

Having some of these SSEG's storing the energy in batteries and warm water for later use will alleviate pressure on the grid during peak time's, especially in the evening.

For now ESKOM is like a speed limiter on the economy, the moment there is economic growth we get load shedding.

SA is a big country and with many SSEG's spread out across the country something like an overcast day in one area will be offset by sunshine somewhere else. There is even sunshine in the East of the country while it is still dark in the West in the mornings and the opposite in the evenings, "spreading out the daylight" so to speak.

But again, many excuses (i.e. reasons) why it will (or can)l not work, in SA.

Edited by WeNotGood
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48 minutes ago, Richard Mackay said:

Other countries that had a massive increase in solar PV systems (due mainly to incentives) resulted in an oversupply of power into the grid during bright sunlight conditions.

You could monitor this real time for the UK if you wanted, hovering over the graphs will show the percentage contribution of the different energy sources, quite fascinating:

https://gridwatch.co.uk/

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