Resilience in HOMER Grid allows you to investigate the savings and autonomy enhancements from adding renewable generation and/or storage to a grid-connected system with a backup generator. HOMER Grid Resilience can estimate the fuel savings and reduction in operating costs. Based on the frequency you specify for the outage (“Outage occurs every…”) HOMER Grid will calculate the effect of the outages on your system’s COE and NPC. In this way, HOMER Grid can model the reduced running costs during an outage and count this as another revenue stream for renewable generation and/or storage on site.
When you calculate results in HOMER Grid, it runs the normal simulations and optimizations modeled with no outages, plus it performs an extra simulation with the outage period that you specify for each system design. HOMER calculates the operating costs for the “no-outage” simulation and for the “with-outage” simulation and computes the cash flows as a weighted average depending on the probability of the resilience outage happening in any given year (one divided by the value specified for the “Outage occurs every…”).
HOMER requires you to include a backup generator capable of serving the critical load. Scheduled forced-off periods for the generator are ignored during an outage. You can use the generator maintenance schedule, but the downtime must be set to zero for each maintenance item. HOMER Grid doesn’t run a stochastic analysis of system reliability in a disaster scenario. There is no unmet load associated with a resilience simulation. Any unmet load due to generator downtime in HOMER’s simulation would be coincidental and would not be a useful result.