CSP and PV plants following a demand curve

Good afternoon,

In my research, I'm comparing the financial feasibility for PV+battery storage plant against CSP+thermal storage in terms of LCOE of the produced electricity. Both plants should be designed to follow a typical electricity demand curve for a specific location (peak demand between 7PM and 9PM while base demand between 4AM and 6AM with variable intermediate demands in between).

For this purpose, I'm trying to control the output of the powerplant to follow the behavior of the demand curve in such a way that the plant gives its maximum output during the demand peak hour, and decrease the plant output to the during the base load hour to match the demand at that time. The key element to achieve this operation philosophy should be energy storage system control.

My question: how can I achieve such a plant output curve using SAM?
In CSP, I tried to alternate the turbine output fractions in the "Dispatch Control" tap in System Control section, but it doesn't really achieve the required result. In PV, I can\t seem to find where I can control the system output.

Your help is highly appreciated.

Moataz

Dear Moataz,

SAM does not allow you to control the output level of the system. It assumes that all of the power available in a given time step either goes to the building electric load, storage, or grid. The solar resource and system design parameters determine the amount of power available, and the storage dispatch inputs determine the timing of energy flow to and from storage. You can control how energy is dispatched to and from storage using the Dispatch Control inputs for CSP thermal storage and Storage Dispatch Controller inputs for PV battery storage.

You will have to do some experimentation to find a set of storage dispatch parameters that results in the system operating as close as possible to the way you want it to.

Best regards,
Paul.

Hi Moataz,

It's worth noting that battery storage within SAM is currently limited to behind-the-meter analysis, i.e, residential and commercial applications where the primary goal to is to reduce energy or demand charges on a customer bill.

The "Battery Storage" page will appear when you select a Photovoltaic case with either Residential, Commercial, or Third-Party financials. To dispatch the battery, you can from automated strategies that seek to reduce peak kW as much as possible, or manually schedule the battery to charge and discharge on a set schedule. Another option allows you to program the desired grid power target, which the battery will try to maintain.

It sounds like you may be using a utility-scale system, which may explain why you are not seeing the battery options accompanying the PV analysis. We do have plans to add batteries for these systems, likely before the end of 2017.

Thanks,
Nick

Dear Paul and Nick,

Thank you for your response. I'm currently using the detailed PV commercial model. The battery storage tap has a storage dispatch section when I'm supposed to control when the battery is charged and discharged. However, for every simulation I make, the battery never seems to discharge lower than 60% SOC during night hours although I have set the discharge allowance to 10%. I also tried the Automated grid power target and set hourly values for the load over the year. This time the battery decided not to contribute in cover the load at all (always fully charged).

There seems to be a concept that I don't understand about how battery system control is managed in SAM.

Please advise.

Moataz

Dear Moataz,
It's hard to say what might be preventing the battery from discharging further without seeing your file. Would you mind [url=mailto:sam.support@nrel.gov?subject=Battery%20discharge%20question t=_self]emailing it to me[/url]? We will not share it with anyone else or post it on the forum, unless you don't mind sharing it.
Best regards,

Paul.

Dear Moataz,

Thank you for sending the .sam file. I was able to get the battery to charge fully during the day so that the PV/Battery system has sufficient energy to meet the night-time load by changing the "PV meets load before charging battery" option to "PV charges battery before meeting load." Without that change, some of the PV power was going to meet the daytime load, and there was not sufficient power left over to fully charge the battery.

Best regards,
Paul.