Impact of Emergency Diesel Generator Reliability on Microgrids and Building-Tied Systems

Research output: Contribution to journalArticlepeer-review

20 Scopus Citations


Microgrids are an emerging alternative as an energy backup system for critical electric loads and have improved performance compared to the traditional architecture where a single emergency diesel generator is tied to an individual building. Both architectures are dependent on the reliability of their individual generators and a quantitative and realistic comparison of the overall system reliability of the two architectures is lacking. Using recently published work on emergency diesel generator finite reliability, a quantitative methodology is presented to compare the reliability of a microgrid architecture based on centralized emergency diesel generators to the traditional approach of generators tied to individual buildings. Three system reliability performance metrics are calculated as a function of outage duration: (1) probability to meet 100% of the critical load; (2) expected fraction of lost load; and (3) probability to meet the highest priority critical loads. It is shown that stand-alone building-tied emergency diesel generators systems, even when two emergency diesel generators are used per building, cannot provide the reliability required to sustain critical loads for a grid outage lasting multiple days. Due to their network configuration and ability to share load, diesel generator-based microgrid configurations are estimated to have ≥ 93% probability of powering all buildings for a 2-week outage there the individual building-tied emergency diesel generator architecture has a ≤20% probability. Microgrids do present other susceptibilities that are site specific and should be considered including vulnerabilities associated with the on-campus distribution system and cybersecurity.

Original languageAmerican English
Article number116437
Number of pages11
JournalApplied Energy
StatePublished - 2021

Bibliographical note

Publisher Copyright:
© 2021 Elsevier Ltd

NREL Publication Number

  • NREL/JA-5C00-76599


  • Emergency diesel generators
  • Energy resilience
  • Generator reliability
  • Microgrid reliability
  • Microgrids
  • Reliability


Dive into the research topics of 'Impact of Emergency Diesel Generator Reliability on Microgrids and Building-Tied Systems'. Together they form a unique fingerprint.

Cite this