46 THE BUILDING CONSERVATION DIRECTORY 2025 CATHEDRAL COMMUNICATIONS PV FIRE RISKS and HERITAGE BUILDINGS JIM GLOCKLING AT THE heart of assuring the longterm security and viability of many listed buildings is their adaptability to meet the comfort and energy efficiency expectations of modern homes. This was discussed in detail by Martina Pacifici in her very good article entitled ‘Retrofit: passive and active strategies for upgrading energy performance while holding embodied carbon’ in the 2024 edition of the BCD. Amongst the potential active strategies are solar photovoltaic (PV) panels, common now on many new buildings, easily retrofitted to older ones, but less common on anything listed, although that might be about to change. From first-hand experience I can tell you that the benefits are great. I have a modest 6kW system mounted on the rear roof of my 1840s house which has greatly reduced our energy bills since its installation. It supplies what the house is using at any given time with any excess directed to charge batteries for night-time use; when these are full it charges my electric car; when that is satisfied it heats the water tank; and only after all local storage is sated will it sell energy back to the grid. Economically they make sense too, with purchase and installation prices plunging, payback times shortening and government incentives forthcoming. Having extolled their virtues and the role they may play in saving the planet, it may seem distasteful to move on to discuss the potential risk challenges that they present, particularly in respect of fire. It is important to note that fires in PV systems are rare events but even so, the difference between their installation on heritage buildings and any other is that even small statistical risks become important when the object at risk is irreplaceable. Fire, after all, is responsible for the greatest loss of heritage throughout all history, and the focus of attention should be on ensuring that these buildings are protected for future generations to enjoy. To understand the risks entailed, it is important to understand the component parts of a typical PV system. PV modules are typically made of a thin layer of semi-conducting material between a sheet of glass and a polymer resin/ glass backing. When exposed to daylight, the semi-conducting material produces electricity. Each PV panel typically covers an area of 1.7–2.5 sq m producing about 300–500 watts of peak DC power. Panels are arranged into arrays to most effectively capture the sun’s energy. PV cable is a bespoke product for PV systems. It is typically flexible, multistranded, double-insulated protected cable, used to connect the PV strings to the inverter; it can be in lengths from a few
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