Hi Soheb,
For the front-of-meter automated dispatch option, the cycle degradation penalty represents the cost of future battery replacements. In each time step, SAM calculates revenue that would be earned if the battery charges, discharges, or is idle. It then subtracts the cycle
degradation penalty from that value and attempts to dispatch the battery accordingly.
A cycle degradation of zero represents the no-cost case, where SAM would dispatch the battery without consideration of battery replacement cost. Although SAM allows you to specify a negative value, a negative value doesn't really make sense. If you find that the battery only dispatches with a negative degradation penalty value, that is an indication that the difference between the power price and cost of charging the battery is not high enough to cover the efficiency losses of cycling energy through the battery.
For a detailed description of the dispatch algorithm, see DiOrio, N.; Denholm, P.; Hobbs, W. (2020).
A Model for Evaluating the Configuration and Dispatch of PV Plus Battery Power Plants
. Applied Energy Vol 262 March 2020, which is also listed on the Battery Publications page:
sam.nrel.gov/battery-storage/battery-publications.html
Here are some suggestions for getting the battery to dispatch:
1. Try modeling your project using the PPA Single Owner financial model instead of the Merchant Plant. You can enter hourly or subhourly price data in $/kWh on the Revenue page by choosing the
Specify PPA price option and setting
PPA price to $1/kWh. Then under
Time of Delivery, choose
TOD factors by time step, click
Edit Array and import or paste the price data in $/kWh. (You can use the same approach with $/MWh price data, just set the PPA price to $0.001/kWh.)
2. In your time series price data, are there time steps where the price changes more than $1/MWh? If not, the small changes in price may not be enough to cause the battery dispatch to respond. This might be easier to explore using the Single Owner model as I describe above in #1.
3. If you stick with the Merchant Plant model, you might try using the Manual Dispatch option. You could try a single dispatch period with both charging and discharging allowed to see how the battery dispatches in response to the power prices, and then make adjustments to the battery size and perhaps the discharge to grid discharge rate.
Best regards,
Paul.
