Total U.S. cost evaluation of low-weight tension-based photovoltaic flat-roof mounted racking

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  • B.T. Wittbrodt & J.M. Pearce. Total U.S. cost evaluation of low-weight tension-based photovoltaic flat-roof mounted racking. Solar Energy 117 (2015), 89–98. DOI: 10.1016/j.solener.2015.04.026 open access



The economics in the U.S. of solar photovoltaic (PV) systems is changing rapidly as the cost per unit power of PV modules has dropped quickly. These costs reductions have two important results: marked decrease in levelized cost of electricity (LCOE) into ranges competitive or better than traditional electricity-generation technologies and the economic role of racking has been gaining prominence relative to that of modules. As the relative importance of costs of PV racking has been marginal historically, there has been relatively little progress on reducing the materials and costs associated with it, which has caused racking to contribute to a significant portion of costs of entire PV systems. In order to overcome this challenge this study investigates a novel low-weight PV racking system for commercial rooftops based on crossed cables (X-wires) and compares it to racking systems already available on the market on capital costs, labor costs for installation, and technical specifications such as adaptability and power packing factor. The results of over 80% cost reduction and 33% increase in power density are presented and conclusions are drawn about the potential for tension-based racking systems to further reduce total PV systems costs on commercial flat roof tops resulting in LCOE savings of $0.01–$0.02/kW h.


  • Solar photovoltaic (PV) costs falling rapidly, racking costs are not.
  • PV racking contributes a significant portion of cost for PV systems.
  • Investigated low-weight PV racking system for commercial rooftops.
  • System based on crossed cables (X-wires).
  • Found over 80% cost reduction and 33% increase in energy density.

X-Wire Racking System

Fig 1: Closeup of joints
Fig 2: How to wire a 3 by 3 array
Fig 3: Finished system

See also

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