Bi-Directional Inverter for Battery systems

Hi Vikram,

The Merchant Plant financial model is tricky to use because the system's output in each time step must be greater than the cleared capacity value. For a PV system that does not generate power at night, the nighttime output will never be higher than the cleared capacity value, unless it is zero. For that reason, the single value option will not work for a PV system: The cleared capacity value must vary throughout the day, or at least from night to day, to match the generation profile.

Best regards,
Paul.

Thank you Paul. I was able to to upload some sample cleared capacity hourly profiles that matched up with the generation profile. This worked fine for the PV only merchant system. I was only able to do this for the manual dispatch option for a PV-Battery merchant system, as with manual dispatch you know the hourly generation and you can use this to create the cleared capacity hourly profile.

However, we were hoping to see examples of how a PV-Battery plant merchant system would typically dispatch on its own (i.e. using the automated dispatch battery storage option). Do you have any suggestions on the best way to set this up? I'm not sure how to get the cleared capacity to be compatible with the "automated dispatch" option, since the two parameters seem to be dependent on each other...

Paul, basically we are trying to see the hourly net power output to the grid of a typical utility scale PV-Battery system. Since most of these systems coming online in the next few years seem to be merchant plants, that is the type we would like to model. 

To do this, we want to use SAM's automatic dispatch feature, which I have found difficult to use in the merchant PV-Battery plant. So for now, we are using the PPA model with a typical utility rate energy charge schedule (buy all/ sell all). we are copying the utility rate schedule and pricing into the revenue TOD schedule (price to buy electricity is same as price to sell for all time steps). To keep things simple we have only allowed charging from the system along with the "automated dispatch look ahead" option, and therefore receives full ITC. Both the solar resource and rate schedule are taken from southern California.

Does this seem like a reasonable way to use SAM to obtain hourly net power output to the grid of a typical utility scale PV-Battery system?

Hi Paul and Vikram, 

I was wondering if you managed to find a workaround for the cleared capacity to be compatible with the automated dispatch option? 
Would it be a possibility to use the merchant model in the same way as the PPA model in which the cleared capacity is set equal to the dispatched output and dispatching is optimized using the $/MWh as set in the lifetime input data (perfect price and solar forecasting)? 
In the same way ancillary service prices could be taken into account in the automated dispatch optimization option (selection between ancillary services and/or merchant based on higher price). Ideally we would set a limit on the capacity volume available for ancillary services as in many markets FRR and FCR are quite limited volume markets. I think it would also be interesting to let the user specify what the service window is. e.g. if the service window is 4 hours, the available capacity (and prices) for that ancillary service cannot change over the 4 hour blocks. This would of course mean the addition of a $/MW/h column. (pay-as-cleared and/or capacity payment). 

Apologies if I let my thoughts roam a bit and let me know if I could help,

Andreas 

Hi Andreas,

I think your approach should work: That would require modeling the system as a PPA Single Owner model first to generate the the "dispatched output" array, which you could then import to the Merchant Plant model.

We will begin work on some improvements to the Merchant Plant model to address these issues in the next few months. Please see this issue on GitHub to track that work:

github.com/NREL/SAM/issues/391

Best regards,
Paul.

Hello everyone,

I'm simulating the Merchant Plant model and i'm having the same error: " The generation is not sufficient to meet the ancillary markets requirements.".
Can you help solving this error? I tried to change the inputs, but the most i can get is a simulation without errors, but the battery isn't used at all, according to the outputs. I tried using the cleared capacity at 0, but it doesn't work either.