Optimizing Vehicle Fleet and Assignment for Concentrating Solar Power Plant Heliostat Washing

Jesse Wales, Alexander Zolan, Alexandra Newmans, Michael Wagner

Research output: Contribution to journalArticlepeer-review

1 Scopus Citations


Concentrating solar power central-receiver plants use thousands of sun-tracking mirrors, i.e., heliostats, to reflect sunlight to a central receiver, which collects and uses the heat to generate electricity. Over time, soiling reduces the reflectivity of the heliostats and, therefore, the efficiency of the system. Current industry practice sends vehicles to wash heliostats in an ad hoc fashion. We present a mixed-integer nonlinear program that determines wash vehicle fleet size, mix, and assignment of wash crews to heliostats to minimize the sum of (i) the revenues lost due to heliostat soiling, (ii) the costs of hiring wash crews and operating the vehicles, and (iii) the costs of purchasing wash vehicles. We establish conditions for convexity of the objective function, and then propose a decomposition method that enables near-optimal solutions to the wash vehicle fleet sizing and assignment problem on the order of a couple of minutes. These solutions yield hundreds of thousands of dollars in savings per year over current industry practices.

Original languageAmerican English
Pages (from-to)550-562
Number of pages13
JournalIISE Transactions
Issue number6
StatePublished - 2022

Bibliographical note

Publisher Copyright:
© Copyright © 2021 “IISE”.

NREL Publication Number

  • NREL/JA-5700-77919


  • concentrating solar power
  • decomposition
  • Fleet sizing
  • mixed-integer nonlinear programming
  • operations and maintenance optimization
  • vehicle assignment


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