Autonomy outage probability output metrics

HI--

Wondering if there is any SAM literature explaining the output metrics "Hours of autonomy during grid outage probabilities." What is included in the SAM help doc is somewhat limited.

Thanks,

Henry

Hi Henry,

SAM's grid outage feature is available for systems with battery storage. It based on REopt's "Resilience" feature described in Section 18.5 of the REopt User Manual: reopt.nrel.gov/tool/reopt-user-manual.pdf .

There are two options for grid outages:

For Meet critical load during outage time steps, you specify a critical load and the times when outages occur. SAM runs the simulation over the analysis period. During periods with no grid outage, it dispatches the battery based on the parameters you specify on the Battery Dispatch page. When it encounters a grid outage, it temporarily dispatches the battery to meet the outage, and then returns to the original battery dispatch strategy.

For this option, the relevant outputs (in addition to the usual battery state of charge, electricity to load from battery, electricity to load from system, etc.) are:

• Grid outage in this timestep
• Critical load in this timestep
• Critical load unmet in this timestep
• Critical load energy (Year 1 and monthly)
• Critical load energy unmet (Year 1 and monthly)
• Critical load unmet percentage (Year 1 and monthly)

For Calculate hours of autonomy for a hypothetical outage, SAM calculates the number of hours your system design would meet the load without any power from the grid. To do this, SAM runs the normal simulation plus a series of simulations starting at each time step of the year to see how many time steps the system can meet the load with no grid power. It then reports "hours of autonomy" metrics to indicate the minimum, maximum, and average length of power outage that the system can meet the load. Depending on your system design, this calculation takes longer than a normal simulation because it requires starting a new simulation for each time step.

The outputs for this option the outputs include "Hours of autonomy" in the label:Single value

• Hours of autonomy during grid outage (min, avg, max): A count of the number of hours the system was able to meet the load without the grid.
• Hours of autonomy during grid outage critical load met (kWh): The total load met by the battery and system over the hours of grid outage.

Data: xxxx values (all starting with "Hours of autonomy during grid outage"), these are statistical outputs you can use to evaluate the system design's ability to meet potential grid outages. They show the probability that the system can meet outages of different lengths. You can export these to a spreadsheet or other software for plotting, or use SAM's Graphs tab on the Results page for plotting:

• Cumulative probabilities
• Hour list from min to max
• Probabilities
• Survival function

SAM also displays the "Autonomy During Grid Outages" on the Summary tab. Here's in a example of how you could create a similar graph on the Graphs tab:

 

Best regards,
Paul.

Thank you, Paul. Definitely interested in a possible webinar on this subject!