Shared solar panels in sectional title, feasible?

As a retired engineer, I have dabbled with inverters and batteries for several years now, nothing very fancy, just a few trolley setups for load shedding.

I have done a lot of reading in several forums, and consider myself fairly well informed, but have no hands on experience with solar installations, just watching with awe as thousands of fellow South Africans spend big money to escape load shedding.

I have two areas that really do interest me though:

  1. The quality of the electrical installations (DB board etc) seem to leave a lot to be desired, I suspect many installations are not compliant, even though a COC was issued.
  2. Sectional title is very tricky, especially where shared roofs are involved.

I am currently a trustee in a small apartment block, which also has some commercial sections. There is a lot of roof space, but it is not going to be easy to cater for both commercial and residential needs, only the common property lighting and motorised gate would benefit from battery backup, and the ROI on investment would be difficult to justify large expense.
Most of the residents are at work during the day, very little power usage for residential during the day.

However I have been mulling over an idea, that I would like the experts to comment on.

Let’s suppose that agreement could be obtained for the body corporate to spend owners reserve funds on solar panels for the common property roof space.
It would need a proposal, a technical, and financial design, a budget etc, a special resolution, and may never get past this stage, but if it did, then my idea would be to allow owners to invest in their own batteries and inverters, according to their requirements, and tap into a shared DC busbar fed from the shared panels.

The solar power generated during the day, would be stored in owners batteries, for use by owners as they decide, during load shedding, or at night to save on electricity costs.
The commercial sections (medical suites) could use power during the day, for aircons and office use.

If there is more than enough solar power to go around, there would be no need for metering, but I have not thought this through in any detail yet.

The benefits of the above are:

  1. Economies of scale, and ease of management, having a shared solar array.
  2. No arguments over roof space, shading, maintenance etc, this would all be managed for owners by the body corporate
  3. Efficient use of excess solar power, if one user does not use his full allocation, another user can benefit.
  4. No more load shedding for those that buy in to the concept, at attractive prices.
  5. Owners will all pay for shared panels indirectly, but there would not be any special levies, just an option to spend on batteries and inverters, as needed.
  6. Savings on after hours usage of power, for lighting, and small appliances.
  7. Geyser heating, maybe, not sure of this at this stage, it would have to be carefully managed.

One thing I am sure of, is that the electrical DBs would have need an extensive redesign, which is not a bad thing.

I am thinking of using ATS devices (Automatic Transfer Switch) to automate load shedding switch over, still experimenting on this.

Is it possible to have a panel array that can be reconfigured at a central combiner box, on a patch panel basis, when it is needed to change panel setup, to meet changing user needs?

I would like to hear from the experts, your comments and advice would be welcome, even if my idea is not feasible, please tell me why!

I would much rather make this AC-coupled. Take your solar panels, put them on a couple of high-power 3-phase PV-inverters (Fronius for example). Owners can then charge their inverters from AC, like they normally do. You have no danger with DC in a home (arcing, fires, etc), rented by someone who is in many ways the lowest common denominator in terms of knowledge about electricity.

The exercise then changes into a way of allowing preferential rates (or even free) during the day, so people can run their loads and charge batteries. If the body corporate already handles metering and billing (ie, consumers don’t buy directly from another supplier), then this is a lot easier than the alternative. It merely requires a kind of smart meter per dwelling.

If you don’t want to do that, then I would still suggest an AC-connection (which is maybe only on in the day time, and billed separately) rather than messing with DC in such an environment.

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This was going to be my question. I think this is essential to simplify a complex job…

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To tackle this project I suggest that you start with the general electricity usage of the complex during the day (not including the tenants). This is a simpler exercise which will provide a gauge of what the prospects are. Many decisions still await you such as will you have backup capability or not…

Such savings are also passed on (in part, probably) to owners in the shape of lower levies. This usually gets the motion passed really quickly! Everyone loves to save a buck. You can plan a suitable saving to be passed on/reinvested in order to rebuild the fund that was dumped into this investment.

Thank you for the advice, much appreciated!

I have heard good reviews of Fronius, what features make it the preferred option for AC coupling?

From a technical viewpoint, Fronius is a premium product (also premium priced), very well built, very good warranty (extensible up to 12 years I believe), from a very reputable company, with exceptionally good software integration into other systems, by which I mean they have an excellent SunSpec implementation.

But they are not the only game in town. Fimer (formerly ABB) makes excellent products as well. Solis/Ginlong makes an affordable product that is quite popular. And even Huawei has a couple of large industrial units that probably deserves a look.

In terms of later integration into a battery storage system, such as Victron, you would probably look at Fronius and Fimer.

Following the excellent advice to look into AC coupled rather than DC coupled, I have been reading up on Fronius and Solis grid tied systems.

My current thinking is that a 3 phase Solis would work well, and that multiple apartments could then link into the shared AC bus, through a pre paid meter, and during the day top up their geyser and optional battery, at a Kwh rate substantially lower than the market rate.

Kind of like renting a system, the owner does not have to pay up front, all that they have to acquire is an isolator in the DB board, and a meter, then they pay a discounted rate for electricity during the day.

They can optionally also invest in a battery and inverter and benefit from battery power during load shedding, or at night.

The wiring would look like this, all the wring would be after the municipal meters, and the geysers and chargers would be be on a changeover switch or off grid.

Is this feasible?

Is this another supply to the houses (i.e your regular mains supply remains connected)

I have one additional concern, and it again depends on how the normal electrical supply is done. If the estate buys in bulk and redistributes to the houses in the estate (and handles billing, etc), then things are a lot simpler. If the houses buy from the upstream supplier directly, and you are now proposing introducing a second seller (the estate itself), then there may be legal issues with the reselling of energy.

To be specific, your big AC-coupled inverter needs to tie with a grid signal, which you will probably take from the upstream supplier. You will then resell a mixture of energy (some PV, some grid) to your downstream customers. At any time when there is insufficient PV, and you end up reselling grid power, this could have legal ramifications.

That’s why I asked if there are two supplies. Splitting the RE supply makes it a lot simpler but isn’t the end of the challenges.
How do you then manage the loads if the RE power is less than what the loads are requiring??

You could take a page from CoCTs book: As long as the overall ENERGY is less (you remain a net producer in other words), you have technically not resold anything.

So what you do, is during those times you have less RE available and you are bridging with the grid, you count two things carefully: How much energy you banked, and how much money you are willing to lose because now you are reselling more expensive grid energy at the lower RE price. When this calculation tells you it no longer makes sense, you simply cut the power. Home owner has to make arrangements if that is a problem.

Still, I would get legal advice before I do anything. Make sure you are within the stipulations of the Electricity Act of 1996 (I think?).

In some ways this reminds me of an issue in Europe, which is referred to as Greenwashing. A politically loaded pejorative term, but in technical terms: This is when you charge a battery with a mix of dirty energy and renewable energy, and then later resell the energy from the battery as if it is entirely green. Many countries have rules against that sort of thing. If you do the same sort of mitigation here, it MAY be possible to make it work.

Overall though, I have to say… the complexity of all this? Legal, technical, home owners who has no idea how things work… unless you’re already buying in bulk and resupplying to the estate, I would probably run away from this idea as fast as I could. Like in the cartoons when the character runs through a wall and there is a Wile E Coyote shaped hole in the wall… like that.

Truth be told, again assuming there is a bulk resupply agreement in place, I would just put up a few big PV inverter, meter it carefully, and end of the month, every tenant gets an equal share in the form of a rebate off the levy. Done.

I thought about this, after Plonk now also posted, my thoughts.

Each home has a meter, right? They still pay for their power.
Between Eskom and the individual meters, said grid-tied system goes in, funded by all homes.

The sun shines and the power is free for all. Sun goes down, Eskom rates for all.

What happens when some owners are out of the house daytime, and others work from home, how would one be fair all around with the big monies initially spent by all, the ones at home benefitting more with cheaper power than the ones off-site?

Or am I missing something?


You are 100% correct!
The loads would be split, 1 feed from Eskom, the other from RE


There would have to be a changeover switch so the tenant can change from cheap energy to Eskom expensive energy, as needed

I consider myself fairly well informed in matters sectional title, and this is a very tricky debate, it probably only needs 1 veto from an owner, and the whole proposal falls flat!

The alternative scenario – that owners are allowed to put up their own panels, under a conduct rule or lease type agreement is equally challenging though.

We will definitely get legal advice from experts.

Thanks so much all your input, very good advice!