Solar and Roofing. Getting it right.
By Dr. Kobus van Tonder, Project Manager, SolarAfrica Energy (Pty) Ltd.
We take a look at how to get solar and roofing right, without compromising the roof’s integrity. With a bit of electrical knowledge and an entrepreneurial attitude, it may seem easy enough to start a solar installation company. But you can’t simply put a solar panel on a roof and hope for the best. In a rapidly evolving industry, how do you stay ahead?
According to Dr. Joe Romm “solar employs more U.S. workers than Apple, Google, and Facebook combined. The global solar market has soared 30-fold in just nine years.”
What does the South African law have to say about installing solar panels? Unfortunately, not a lot at this stage. There is no single law regulating this part of the industry however, best practice guidelines and principles can be followed.
Health and safety is a paramount part of any installation to avoid being criminally liable. Working on rooftops with awkward 1.7m x 1m panels weighing around 25kgs each means that you should start with the working at heights approval. All workers who work at heights must use fall protection on a project and attend an approved working at heights training program.
If you are changing the physical structure of a roof you must go to the council, this applies to solar too. Starting with the roof at hand, is it a standard tile or chromadek roof? Most panels require only 100 mm clearance between the module and the roof. When installing on flat roofs, for example, there would be a fundamental change to the roof, as the panels would need to be at an incline to make the most of the sunshine.
Interestingly, the City of Cape Town requests all solar installations that, to the grid require a small scale embedded energy (SSEG) certification, regardless of whether you intend to apply for SSEG rates or not. This means that even if you do not intend to “feedback” to the grid (i.e. apply for SSEG tariff rates), you still require this certification.
Another best practice guide would be to join the South African Photovoltaic Industry Association (SAPVIA) which is a not-for-profit body consisting of active players in South Africa’s photovoltaic (PV) market who have a genuine, invested presence in the country. A new initiative is the PV Green card, which will train and educate people interested in becoming reputable solar installers in South Africa.
Before installing solar, consider the location, roof structure, and individual customer requirements. Going green is trendy and consumers’ want solar as well as cheaper electricity but they need guidance to the correct solution.
Adequate space is needed in order to install the solar modules; a rough guide is 10m2 for every kW of power required. North facing roofs are ideal in South Africa, with a tilt of approximately 25-30 degrees. Furthermore, consider the structural integrity of the roof. Although no law currently requires the structural analysis of the roof, the reasonable man test should always be a guide when attempting a solar installation. Consider all possible consequences of adding additional load to an existing structure, and if in doubt, get the help of a structural engineer to guide you on the load bearing capabilities.
Is energy security a priority or not? For those with a stable grid, selecting a solar solution without batteries would be preferable as grid-tied solar systems are less complicated and more economical to purchase but no mains power means no solar either. For those customers who have complaints with energy stability, batteries are the way to go.
Once the type of solution has been selected you must then decide three things – the type of module, the inverter, and mounting system solution.
There are different types of technologies available today that are utilised in solar panels; these are monocrystalline, polycrystalline (known simply as mono or poly) and thin film amorphous. The poly modules are the most popular technology in South Africa, but there is very little difference between mono and poly on price and technical performance. Thin film technology has better shading and high-temperature characteristics than the crystalline modules. At the end of the day, it is important to pick a reputable brand to ensure the best quality, safety standards, and on-going support.
String inverters are best suited to rooftop solar installations as they usually have multiple maximum power point tracking (MPPT) systems giving better performance. Also, power optimisers are a valuable addition if you are faced with multiple roof orientations and partial shading. Central inverters are better suited to bigger, ground mount systems as they typically only employ one MPPT system per inverter.
Installation mistakes are common, yet one of the biggest risks to a successful solar PV installation is the quality and condition of the roof. Before starting a solar installation it is best practice to complete a detailed issue report of the roof condition to protect both installer and customer. Think of it akin to a checklist the car hire companies make you sign before you drive off; are there any visible scratches or dents? If you miss something you know they will make you pay when you drop the car off later! Document all roofing issues and get sign off on this off before starting. Again, on completion do an impact report and water test and request sign off by both parties. As the last person on the roof, the comeback later for roofing damage or leaks will fall on you.
A simple flex test is always recommended. If the roof flexes under your own weight, request a professional opinion on the roof structure before going forward. Each roof is different and a structural engineer will be able to advise the integrity of the roof before proceeding.
The most damaging mistake to a system’s overall performance is shading. A simple thumb print size of shading in one corner of a single panel can lose a third of that whole strings production. There’s ‘near shading’ to avoid such as trees in the garden, a chimney or even a TV aerial, and ‘far shading’ such as skyscrapers, mountains, clouds etc. A general rule of thumb is that if a portion of the roof is shaded 70-80% of the day between 9 am and 4 pm, rather do not locate a panel in this shaded area.
Another common mistake is galvanic corrosion (also called bimetallic corrosion), where two metals don’t get on when they have contact with another, in the presence of an electrolyte. Add high humidity and a salty environment and that’s the perfect recipe for galvanic corrosion. In solar installations, this could occur where stainless steel comes in contact with aluminium. Either ensure all metals are the same where possible or use an insulating rubber so they do not touch each other.
Finally, the mounting system design should be purchased from a reputable supplier, ideally with a vast knowledge of the structural design of a roof including wind and load analysis experience. The last thing you want is a solar panel to blow off and end up in your customer’s garden or worse. A reputable supplier will know which mounting system to use for the particular roof you are working with as well as the module and inverter you have selected.
So how can you get it right when it comes to solar installations while maintaining the roof integrity? Prioritise the health and safety of your staff, work to best practice guidelines at all times, train and select reputable products. This industry is expanding and the opportunities are plentiful if you can get it right.