Case Studies - Photovoltaic (PV) Survey on a Grain Store

Project Description
  • 15th October 2019

The Aim

ThermoSurvey was asked by Fowler Fortescue Chartered Surveyors to conduct a photovoltiac thermal survey using thermal cameras on aerial assets  to survey a PV array on a grainstore to ensure that the client was getting the most out of the array.

Grain Store

The Case

The array was installed on the roof of the grain store in 2011 and as a result was receiving £0.38 per unit in Feed It Tariffs (FITS), which is one of the most generous.

On a blustery  late summer’s day ThermoSurvey used the Matrice 210 drone equipped with both thermal and digital cameras to conduct the  thermal survey which showed up a number of issues. Back at the office the analysis indicated that there were three sets of problems. First was that there were 6 strings that were not live (about 20%). Second, that there were modules that had evidence of Potential Induced Degridation ( PID) which is effectively a current leakage caused by the delamination of the module; which cannot be rectified. Further investigation techniques would be required, such as photoilluminescence, to confirm this.

Damaged strings on the array.

And third was lichen growth that was growing over a part of the array. This indicated lack of effective cleaning and the problem can create up to 30% loss of modular yield. Once removed the lichen creates a permenant stain so should be removed as quickly as possible.

The financial implications of the string issue was that the owner was losing just under £9,000 per year which would be over £151,000 for the rest of the array’s working life.

The client is now looking at the warrenties as both the strings and PID should be covered by the installer and manfacturer.




Fowler Foretescue were very happy with the survey results and are currently in discussions with the installer in order to rectify the problems with minimum of costs.