Solar photovoltaic panel installations on both residential and commercial rooftops can pose several challenges especially where limited roof space is available or where the owner wishes to maximise the power generated on the roof. A proper design based on a 3 dimensional layout of the whole system should always be done before the actual installation is carried out to ensure that the installation is done within local planning authority guidelines and is safe to clean, maintain adverse and is able to withstand adverse weather conditions. Shading analysis should also form part of the design so that the system will have minimal shading effects from any objects in the vicinity in order to maximise the system’s generation.
Planning Authority Regulations
When a client applies for a feed in tariff for a photovoltaic system with REWS (Regulator for Energy & Water Services), the client is agreeing to adhere to the local ny deviations from the guidelines, such as installing a PV system on a canopy or shifting the photovoltaic system over 1m above the roof’s level requires planning permission. This is done through a DNO (Development Notification Order) application or a Planning Summary application which is usually submitted by an architect. Once the permit is issued by the planning authority, this is submitted with the REWS application. Failure to possess the necessary permits can result in fines and the dismantling of the system.
Proper design begins with a site visit by an energy specialist who takes dimensions and pictures of the roof and also takes a note of obstacles that can potentially create shading. Using advanced CAD software, the photovoltaic installer can than produce 3D layout designs in order to ensure that the best location, orientation, elevation and structure for the photovoltaic panels is found. Ideally, PV modules should be free from any shading between 09:00 and 15:00 on the 21st December (the shortest day of the year) in order to maximize the generation. The software calculates the amount of shading produced by nearby objects on each individual photovoltaic panel and can determine accurately the annual yield generated from the system. The client can also view different layouts and scenarios and any items that would require shifting on the roof such as water tanks, aircon units, satellite dishes and solar water heaters in order to optimise the performance can be visualised beforehand. The photovoltaic system’s shading analysis is a crucial design step that cannot be skipped if the client wants to know how the system will perform.
Wind loading effects and mounting structure
It is a known fact that the windspeeds across the Maltese islands have been on the increase and the Force 9 hurricane in February 2019 caused a lot of damage to photovoltaic systems that were not adequately protected against wind loading. Photovoltaic panels typically weigh around 20Kg which is not a lot considering that they have an effective surface area of around 1.8m2. The ideal orientation for a photovoltaic system is inclined and facing south which means that the predominant northern winds hit the panels over this large surface which can cause the panels to overturn, fly off or get dragged across the roof. Each roof and locality has different wind loading characteristics and the right type of structure, ballast, windbreakers and additional anchoring solutions should be utilized in order to guarantee that the whole system can withstand windspeeds of up to Force 12. The structure manufacturer should be able to provide wind loading studies with a recommended ballast plan, design certification and warranties. Again, this should form part of the overall system design. Given that the whole of the Maltese islands are considered to be a coastal zone, the mounting structure should be made of an aluminium marine grade alloy or at least anodised aluminium which is resistant to salt corrosion. Mounting structures made out of metals such as galvanised steel often end up getting corroded in the long run and should never be in direct contact with the photovoltaic panels which have an aluminium frame as this will result in galvanic erosion. All nuts and bolts utilised should also be made from high grade stainless steel.
Maintenance & Cleaning
Every photovoltaic system requires maintenance every one or two years and cleaning typically around four times a year. In order to ensure that the maintenance and cleaning are performed safely, adequate space for access should be included in the design of the system. Where necessary, railings, walls, guards and other additional boundaries should be recommended in order to achieve a comfortable level of safety for both owner and installer.
Cabling & Earthing
The photovoltaic modules are connected to the system’s solar inverter through DC cabling and the solar inverter is in turn connected near the client’s consumption meter with AC cabling. Moreover, all the photovoltaic system’s components are connected to earth in order to protect the system and occupants against faults and surges. The size of the cabling used depends on the lengths of these cables so it is important to have an idea beforehand which routes these cables will pass through and follow the required standards in terms of the type of cables and anchoring methods employed.
The location and type of solar inverter is also an important consideration and ideally, this should be installed externally on a north facing wall with easy access to the DC & AC isolators next to it so that the system can be shutdown safely when thunderstorms are approaching. Nowadays most solar inverters can connect to the Internet for remote monitoring, alerting and remote support via wifi connectivity so the wifi signal should also be strong at this location.
Ask us for help
To conclude, a good photovoltaic installation requires proper design and planning and as daunting as it might seem, using the services of a professional will guarantee that your solar investment will perform as expected. For more information on designing and planning you roof for a new photovoltaic installation, contact one of our representatives today for a free onsite visit on 20102121 or leave a message on our contact us page and we’ll get back to you ourselves.