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January 2014: PHOTOVOLTAIC (PV) SOLAR PANELS

Photovoltaics (PV) is the generation of electrical power by conversion of solar radiation directly to electricity through the photovoltaic effect exhibited by semiconductor materials. Initial costs to produce PV panels remain relatively high, but as technologies are improved and demand increases, costs are falling. PV power generation is growing - currently behind hydro-electric and wind power generation, but steadily closing the gap.

To form a PV solar panel, individual solar cells are mounted onto a flat panel and individual cells on a panel are electrically connected. The entire panel is then encased in glass, providing protection for the fragile cells. As the electrical output of an individual PV panel is relatively small, the panels are further interconnected to form an array. Very large plants may generate 300+ megawatts of power using arrays comprised of 100,000+ individual panels, and covering 1000+ acres. Small PV arrays may fit on the roof of residential dwelling. Arrays of all sizes in between may be found.

For most PV panel installations the Return On Investment (ROI) is difficult to justify, except for the availability of tax and rebate incentives offered by federal state and local jurisdictions for the installation and continued operation of these facilities. Thanks to governmental incentives, it is not uncommon to find installations of relatively small size in commercial and industrial facilities such as office buildings, parking garages, industrial plants and municipal facilities. Many of these are located on rooftops, where space is available and the visual effects minimal. Some are located in ground based arrays if space is available and visual objections can be met. These systems seldom have the ability to meet the full power demand of the facility, but are installed to defray local utility electric costs. Many installations further increase ROI by delivering and selling any excess electrical generation back to the utility.

The most evident property loss prevention concerns for PV arrays are related to natural causes including wind, hail, snow, ice, earthquake, lightning and fire exposure. Below is a list and brief discussion of these hazards and design elements, which should be considered when installing a PV array.

Fire is normally the greatest property loss prevention concern; however fire is not generally a major concern for PV panel installations. Most PV panel installations are constructed of non-combustible materials, but this should not be taken as a given, as manufacturers can and do use insulations, plastics and cushioning materials which are combustible. To consider PV panels as non-contributing to fire, the manufacturer should have completed testing by a qualified third party, using recognized testing methods as appropriate.

Wind design is an obvious concern, as PV panel arrays create a large surface area subject to wind uplift. Installations in coastal areas are clearly a major concern. Care and attention should be paid to the methods of attachment and the wind uplift resistance required. This is particularly true for installations on top of roofs, and even more so for pre-existing roofs where the original design did not contemplate the addition of these components.

Hail damage is a serious concern for the fragile PV components held within a glass encased PV panel. FM Global’s Data Sheet 1-34 shows more than half of the continental US is subject to severe exposure from damaging hailstorms. Solar panels should be rated for hail, with a minimum rating of Class 4 (2 in. diameter) recommended for areas rated as severe exposure.

Snow and ice loading on PV panels will impose additional weight loads, which may stress panels or the underlying structure. This can be of concern for some ground based installations, but is a much greater concern for rooftop installations. Therefore additional loads imposed by ice loading and snow drifting should be calculated for rooftop installations. The roof structural load capacity should be confirmed to be capable of handling the loading imposed both by the weight of the panel installation as well as additional live load weights temporarily imposed by snow and ice loading.

Earthquake. In areas subject to seismic damage, PV panels should be designed with earthquake resistance as documented by testing to meet appropriate performance levels. This should also extend to cabling, connections and wear points, which can be stressed during differential movement between adjacent panels during an earthquake.

Lightning. As in any electrical installation, lightning damage to sensitive electrical components is a concern which should be recognized in initial design. Lightning arrestors, surge suppression, grounding and bonding systems should be provided for transformer, inverter, power electronics and control systems. Testing of these prevention systems should be performed at least annually.

Transformers. In larger installations, transformers will be present and may contain combustible mineral oils for electrical insulation. As with any transformer installation, containment diking, isolation, spacing and fire protection should be considered during the design process.

Exposure. PV panel arrays should consider exposure from any adjacent features. This can include buildings, structures, transformers, wooded land, and flood prone waters. The obvious solution is for site facilities components to appropriately avoid exposure from both external and internal sources.

Inspection. PV panel arrays should be routinely visually inspected to confirm that there is no evidence of significant damage such as cracked glass, broken connections, buckled members, broken/missing bolts, etc. which could result in further damage if left unattended.

Photovoltaics is a growing field, as these installations become more common in commercial power generation, as well as in industrial and commercial facilities where they are utilized to offset commercial power costs. If you have, or are planning to install a photovoltaic system, Risk Logic Inc. can assist in evaluating any concerns with respect to property loss exposure for pre-existing or new construction projects.