Tests to prove reliability of large-scale solar PV




California ISO, First Solar, National Renewable Energy Laboratory (NREL)


California ISO - CAISO, the US National Renewable Energy Laboratory - NREL and solar PV solutions company, First Solar demonstrated how large-scale solar resources can provide essential reliability services to the grid, which have traditionally been offered by conventional power plants. A series of technical tests conducted on a 300 MW PV plant showcased the role of advanced controls in leveraging the solar energy’s value and contributing to grid stability.  



  • Most extensive testing and demonstration of reliability services involving PV generation ever conducted in the world
  • Reducing the need for conventional power plants to provide reliability services
  • More accurate ramping of PV plant’s power output compared to conventional power plants
  • Cost savings through eliminating the need for voltage control devices after sunset
  • Smart inverter technology combined with advanced plant controls allowing multiple PV resources to operate as a single resource  



Besides replication in any large-scale PV power plant in the world, the practice is also applicable for clustered PV resources (assuming appropriate power aggregation and availability of communications and controls). Additionally, to further enhance system flexibility, storage can be easily incorporated into the concept.  


Main information:

By 2030, utilities in California are required by state law to produce 50% of their electricity sales from renewable energy sources. To reach this goal, California grid operators need to find additional ways to maintain grid reliability and balance generation and load with increased levels of variable renewable generation. Demonstrating today that additional ways are feasible is instrumental in achieving the state’s broader objective of a resilient, reliable, low-carbon grid.  

For this purpose, CAISO in collaboration with NREL and First Solar, conducted various tests in order to demonstrate the PV plant’s capability to provide upwards/downwards ramping of its power output, frequency response and voltage control.  

Since some PV plants already can provide these necessary reliability services, the practice could be implemented as soon as the regulatory environment allows renewable resources to be equitably compensated with conventional plants.  


Additional information:

  • Practice’s partners: CAISO (California’s grid operator), NREL (leading U.S. federal research centre on renewable energies), First Solar (vertically integrated large-scale PV utility)  
  • CAISO plans a broad stakeholder outreach effort with industry to identify barriers with PV resources providing reliability service


RGI gratefully acknowledges the EU LIFE funding support:

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Funded by the European Union. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the LIFE Programme. Neither the European Union nor the granting authority can be held responsible for them.