The assessment of the potential bifacial gain remains a challenge, with the industry yet to reach a consensus for a methodology to produce a bankable energy yield assessment. Available solar energy modelling tools incorporate bifacial PV module capabilities, however they adopt simplified models for representing rear-side irradiation conditions, at the cost of increased modelling uncertainty.

Alternatively, 3D CAD and ray-tracing software can be used for detailed modelling of bifacial PV array geometries, and of the complex rear-side irradiance. Ray-tracing methods, which are computationally expensive and complex, are yet to be implemented in commercially available PV modelling tools, although have been the subject of research.

Mott MacDonald developed its own solution for bifacial PV modelling, integrating ray-tracing software, industry-standard modelling tools, and algorithms developed in house. The solution, which has been validated against data obtained from several operational testbeds, yielded relative differences on an energy yield-basis of up to a maximum of 0.6% from field-obtained data. This compares favourably against industry standard software which, utilizing a view-factor model, yielded relative differences of up to -7% under default settings.

Mott MacDonald’s solution for performance modelling of bifacial PV projects provides lower uncertainty yield estimates, with reduced risk for project developers, lenders and investors. To date we have applied our methodology to produce bankable energy yield assessments for bifacial PV projects of more than 1,000 MW in five countries, including as part of the project financing of the 296MW Potrero project (Mexico), one of the world’s largest bifacial PV developments, and one of the largest merchant PV projects worldwide.