The growing appeal of rooftop PV

by Ofentse Sefolo
The growing appeal of rooftop PV

Installing a rooftop solar photovoltaic (PV) system was for many years considered as an expensive luxury for those seeking to limit their environmental footprint, but this is no longer the case. Drastic reductions in the cost of solar panels, coupled with rising electricity tariffs and uncertainty of supply, have made solar PV increasingly attractive to both residential and commercial energy users.
One of the reasons that PV is so popular in the residential space is that it is relatively inexpensive and quick to install. “There are professional installers who will install from 1kWp (four panels) to over 1MW (over 4 000 panels) on a roof and most residential installations can be completed in a day or two,” says South African Photovoltaic Industry chairman, Davin Chown.

How big should you go?
Household systems typically range between 2kWp and 10kWp, and businesses typically from 10kWp to over 1MW, depending on their load profile and the space available. 1kWp is the number of kW per hour produced when a PV system is operating at its optimum capacity. In other words, a PV system of 3kWp working at its optimum capacity will produce 3kWh of electricity in an hour.

The universal standard for household rooftop PV installations is around 4kWp and four panels will deliver roughly 1kW. “These ‘solar generators’ are a much lower risk than the complex, high-voltage large installations, and can often be installed in a single day,” notes Richard Douglas of The Green Way Solar.

Installation and maintenance
Solar PV can be installed on north-, east- and west-facing rooftops, although the design becomes more important as the load profile increases.

“Solar PV needs little maintenance – you’ll just need to keep the panels relatively clean and make sure trees don’t begin to overshadow them,” states Douglas. “Panels have a performance guarantee of 25 years and quality panels could even last longer.”

Talking money
Frank Spencer of Consolidated Power Projects Energy Solutions says the cost per kWh of rooftop solar varies depending on the size of the installation, the site solar irradiation, and the cost and term of financing.

“You can expect the cost of a kWh to be in the range of R0,80 to R1,20/kWh. In broad terms means that systems start at about R20 000/kWp and this could drop to as low as R10 000 – R15 000/kWp for larger installations,” says Spencer.

This means that you can expect to pay between R40 000 and R50 000 for a small installation of 2kWp of solar modules that will provide approximately 10kWh of energy per day, which is sufficient to power a small household.

The 1MWp solar photovoltaic (PV) installation on the roof of the Woolworths
Distribution Centre in Midrand, Gauteng.
Courtesy of Solareff

2 things to consider
There are two main aspects that need to be considered when installing and operating a rooftop PV system: The physical wiring and installation, and how the system interfaces with the grid.

For small-scale uses, safety and reliability are paramount, so it is important to ensure that your installer is a qualified solar PV service technician. “The growth in rooftop PV is really encouraging, but the flip side is that we have seen an increase in the ‘bakkie brigade’ – small-scale contractors who may not be suitably qualified to install a PV system or able to guarantee their workmanship,” warns Chown.

Embedded generation
Another challenge is a lack of national regulations, guidelines and standards that govern embedded generation and connecting to the grid. This is expected to change over the next year with the adoption of the recently published NRS 049-2 or Smart Meter Standard that regulates feed-in tariffs, and the finalisation of SANS 10142-3 standards, which regulate the low-voltage wiring code for embedded generators.

Major metros such as Cape Town and Tshwane, as well as several smaller municipalities, have already put in place systems to allow embedded generation, but from a residential perspective, Chown says feed-in tariffs remain in their infancy. “Although some of these municipalities allow you to feed your excess to the grid, this is at a very low rate. At the moment feed-in tariffs are mostly for commercial and industrial use, but this will change as soon as the new small-scale embedded generation regulations are finalised.”

Who is taking advantage?
Solar PV systems have been extremely popular with shopping centres and retailers who are able to take advantage of their significant physical footprint. The agri-processing sector has also seen a significant uptake of PV with a host of pack houses having installed sizeable amounts of their own generation facilities via rooftop solar PV.

Apart from the benefit of being less reliant on the grid and less exposed to future electricity tariff increases, PV is also increasingly cost-effective for commercial users. “If you are a commercial or industrial user, you can lower your peak kVA, which will result in a lower price per kWh on total electricity purchased. Most major municipalities will also pay you a feed-in tariff for the kWh you export to the grid,” Douglas concludes.

Full thanks and acknowledgement are given to the South African Photovoltaic Industry Association for this article.

PV GreenCard
The PV GreenCard is the first industry-wide, standardised PV licensing system and registration process, serving as a national “as built” report that should be issued with every small-scale solar PV installation.

“Up until now there has been no industry-wide, standardised PV licensing system or registration process, so we developed the PV GreenCard as a means to promote quality and safe solar PV installations within the industry,” explained South African Photovoltaic Industry Association (SAPVIA) CEO, Mike Levington.

Once a PV GreenCard certified installer completes a new rooftop system, the client will be issued with an electronic PV GreenCard document. This e-document will confirm that the installer is suitably qualified and has complied with all the relevant standards and guidelines in the field of PV system design and installation. Accredited installers will also be added to a SAPVIA-recommended PV installer database.

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