Rooftop solar rules, OK?

February 6th, 2017, Published in Articles: EE Publishers, Articles: Vector


Mike Rycroft, EE Publishers

With all the attention focused on the REI4P and the haggling over final signing off, it is often forgotten that there is a market sector which is independent of government plans, uses private finance, and is growing at an astounding rate, namely commercial and residential rooftop solar.

An industry database estimates the total number of rooftop installations at over 40 000 with a combined capacity of 248 MW. This is small compared to the REI4P capacity, but represents a large number of installations and a significant workforce. The increase in rooftop solar has been driven by a number of factors, not the least of them the increase in the price of grid electricity, and the load shedding experienced in recent years. Solar PV is fast becoming an affordable and economic source of reliable power, both for commercial and residential users, but the market is changing fast, and we must keep up with developments if we are to benefit fully from the technology.

One area where we are lagging behind is the optimisation and full utilisation of the potential of rooftop solar, particularly in the residential sector. There are many developments worldwide which move rooftop solar away from the basic grid connected system used to reduce grid consumption, to an advanced energy management system, even at residential level. Last year saw the introduction of the Tesla and other home storage systems into this country, but the uptake has been very slow, apparently.

Perhaps it can be attributed to the previous and still lingering obsession with nett-metering and residential feed-in tariffs, based on the false assumption that the municipalities would pay inflated rates for electricity delivered to the distribution network, either under a nett-metering scheme or a feed-in tariff system. The low prices prevailing for the utility solar plants under the REI4P system have put an end to any possibility that a distributor will pay more for local generated electricity than what it can be purchased for from the utility, or more for PV electricity than what the retail sale price is. At a recent workshop on solar pricing, one delegate was adamant in his determination to profit from selling excess PV power to the grid. The fact that this would increase the price to other users seems to have bypassed him, driven by the profit motive.

There is a growing realisation in other countries, especially where time-of-use tariffs are applied, that it is more beneficial to store your excess generation during the daylight hours and use it for own consumption during periods of high tariffs, than to sell it to the grid.  This essentially amounts to buying back cheap electricity from yourself. A recent exhibition featured a full residential-scale hybrid system, complete with batteries and grid interface, which was housed in a very elegant standard cabinet, and which could simply be coupled to the grid, main board, and PV systems without complications. Not that one would want such a unit in your lounge, but it would fit nicely in the garage, and does not need external battery units or inverters, and could also be coupled intelligently to domestic IT devices.

Other developments involve over-the-fence, behind-the-meter trading of stored energy within a community, which I think is something far in the future for us. But we are starting to see another facet taking root, namely community solar, where the solar array and associated storage, are owned or shared by a community. Granted, this is limited at the moment to commercial properties, where the owner provides the solar system, and provides the electricity to tenants. Notable in at least one commercial park in JHB, the parking lot outside a large shopping mall in Tshwane, and most notably, the medical centres of a national health services provider. How the system is owned and operated I am not sure, but one could imagine a co-operative type of ownership among tenants as part of the lease contract.

The possibilities of community solar and storage become attractive when one considers the large number of residential complexes and estates in this country. Common property is jointly owned anyway, so the potential for community solar should not pose too many legal difficulties and, in many high-density complexes, the rooftop is common property, opening a huge possibility for shared solar PV. One could consider that PV with storage could provide the street lighting and other common areas such as swimming pool pumps of such complexes with cheap electricity, as a starting point towards community solar.

With the number of rooftop installations increasing comes the concern about quality of installations and training for installers. To the best of my knowledge, there is no specific wiring code available in SA covering rooftop solar, which as a behind-the-meter installation must comply with the code, although I have been informed that the SABS 0142 work group is hard at work with completing the amendment to the wiring code to accommodate this. There are numerous other countries codes that can be referred to but are not legal in this country. The American code is very advanced in this respect.

Solar PV has moved far from the original systems based on 12, 24 or even 48 V, and it is common now to have rooftop systems operating at hundreds or even thousands of volt DC. DC is just as lethal as AC at this level, and is also very good at establishing and sustaining arcs. Numerous cases from other countries of rooftop fires highlight the fact that electrocution is not the only danger, and damage to property is a reality of substandard installations.

With such a rapidly growing market comes the danger of unqualified installers, DIY installations, and substandard and counterfeit equipment. We recently discovered counterfeit panels at an installation belonging to a charity organisation, which had an impressive looking label at the back claiming compliance and a rating of 300 W, whereas the size of the panel showed that it could only have been of the order of 150 W. In addition the front of the panel showed numerous delamination tracks. This was obviously a relabelled reject and it was a great pity that this found its way into a charity installation.

The industry is making great strides in training PV installers, and there are numerous courses on offer, but there does not seem to be an industry standard of competence that could be applied, something which the DoL, which controls electrical training standards, should take up. Without an applicable section of the wiring code to set the standard, this is something of an enigma.

The coming years are likely to see even more developments taking place, not all of which will be suitable for South Africa. We saw this year the launch of solar tiles for houses in the USA, but whether such a concept would take off here is questionable, and there are no doubt many others, such as solar windows, in the pipeline. I doubt whether any will surpass the basic product in cost-effectiveness, and I could be wrong, but it is fairly certain that there will be tremendous growth in basic rooftop solar systems in the future.

With all these rooftop solar systems around, one wonders who cleans the panels. Many rooftops are inaccessible with normal access equipment, and few owners will have the specialised cleaning equipment required, so this is job for professionals. A quick search of the internet reveals that there is only company in the whole country advertising panel cleaning services. Is this a business opportunity going begging?

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  • James Barbour

    It appears that engineers and scientists are trained differently.

    A scientist is trained not to prove something but to disprove it – simply because the second is easier than the first – which, in fact, (for the empirical sciences) is impossible.

    Engineers, it would appear, do not know who Karl Popper was. True he was a complex person (who isn’t!) but in the context of science we remember him for the way we do science. It is important to understand: “Scientists don’t prove things, they disprove them”.

    Have you discovered a cure for some disease – let’s call it “stupidity”? Then a scientist don’t set out out to “prove’ that your cure eliminates stupidity. Instead, that scientist designs an experiment that is based on the statement “My cure does not eliminate stupidity”. The experiment will (hopefully!) disprove the latter statement.

    When the experiment produces evidence which destroys the latter statement, your name is in the list for a Nobel Prize.

    Engineers have this curious belief that “batteries solve the problem of the intermittency of wind and solar power generators”. That “batteries” (I include the likes of pumped storage) do not is easily established with a Popperian thought experiment.

    Assume you have a system which has storage for x hours. Will that system deal with a state where there is no generation for x+1 hours? Put another way” “Does storage solve the problem of intermittent power generation”?

    If you know who Karl Popper was and what his contribution to Science was you have no problem in understanding why engineers needs to be trained to be scientists.

    Batteries do not solve the problem of the intermittency of wind and solar generators. Don’t ask an engineer, ask a scientist. They understand the contribution Karl Popper made to how humans accumulate knowledge.

    • Andrew Fraser

      This argument is a little short-sighted. A similar argument could be used for almost any engineering problem and solution.

      For example, a hypothetical climbing rope has a breaking strain of 5000N, we can’t argue that this climbing rope is not a safety solution for a 100kg climber because it could fail for a 501kg climber.

      If energy storage is sufficient to overcome intermittency of wind and solar generation to the level where it is equivalent to the supply from fossil fuel and nuclear generation, then it can be said that it is a valid solution to the problem.

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