The increased uptake of solar PV on commercial buildings has created a battle for roof space.
If it’s a new building space issues can be resolved in the planning stage but retrofitting solar or air conditioning requires a solid understanding of both technologies, according to Brian England, the national chairman of the Solar Energy Industries Association (SEIA).
He said solar PV panels are typically installed in long series strings of between 10-20 panels with voltages in the 400Vdc to 800Vdc range.
“These voltages are dangerous, and DC voltages of this order are more dangerous than the same voltage in AC so it is critical to ensure live cables are not disconnected or broken,” England said.
“Parts of the solar system should be shutdown prior to commencing any work near panels; shutdown procedures are located alongside the inverters and for more recent installations there will be DC circuit breakers adjacent to the PV strings.”
This is just one of a number of issues that need to be taken into account. For example shading of a panel, or even part of a panel in a string, can affect the entire string.
“That is why its important when sighting additional equipment on the roof such as extra vents or air conditioning condensers and cooling towers, it is important to liaise with the solar company responsible for the installation,” England warned.
“This will ensure a good outcome because the sun can cast a long shadow.”
Also, when exhaust vents pump hot air or gases onto the roof space this can heat up the solar panels.
“Most PV panels actually lose performance as they heat up, as much as 25 per cent during summer, which is why its important to minimise heating of panels to optimise solar performance,” he said.
“Some exhaust vents carry dust which can deposit over the panels providing in effect a partial shading. Sometimes this will wash off with rain but it often means the building owner is forced into a solar panel cleaning contract to maintain system performance.”
England said some condensers and cooling towers may be given a performance improvement if protected from direct sun.
If this is the case then panels can be mounted on frames that provide some shading.
Ventilation of the equipment is another consideration to ensure there is plenty of air movement.
When installing a solar system at Parliament House in Canberra, Todae Solar and Silex Solar undertook a pilot to study the issues associated with the integration of photovoltaic power generation into the building’s existing infrastructure.
The solution had to factor in performance, design consistency, ease of maintenance, building integration and aesthetics.
The 43.3kW capacity was delivered as a combination of two systems - 7.77kW on the roof of the Gardeners’ compound and 35.52kW on the roof of the Senate wing.