Hello everyone,
I am working on a research which involves PV penetration in the grid. I have an Energy Storage System (ESS) which is rated at 25% of the PV Generation . The ESS is assumed to be connected in parallel at the same bus to PVG on the HV side.
I want to know what are the common ways to dispatch ESS in such a case?
As far as I know, the ESS can be dispatched by taking average of PV power of next hour.
However, Can the utility simply dispatch ESS to their desired value?
Thank you in advance,
Sam
Hello Sam,
See the ESS operational modes of this commercial equipment.
https://www.victronenergy.com/live/ess:ess_mode_2_and_3
Best regards, Martin
I believe there will be a Battery Management system (or equivalent for other forms of ESS,) for monitoring . You have to have an estimate of solar kWh that will be available in next 15 mts and also refer to a predicted load demand. Algorithms can decide the schedule of ESS to see that frequency and voltages remain within limit and balance of storage available after 15 mts. Load has to be adjusted in case storage has to be retained for longer hours. In solar hours, solar power should be optimally used to meet load and if possible , help the ESS.
Dear Samundra Gurung,
Your brief note leaves out an important factor in describing the system. You say your Energy Storage System (ESS) is rated at 25% of the Photovoltaic Generation (PVG) system, and that they are connected in parallel to the same bus. What you are omitting is the capacity of your ESS system – for example what matters is not only the MW input or output of the ESS, but what is its MWh capacity compared to the output of the PVG system.
Assume the PVG system has a rated output of 10 MW, so perhaps in a day it might produce 40 or 50 MWh, assuming 4 to 5 hours of peak solar irradiation (or whatever factor is relevant). You may be thinking that your ESS has a rating of 2.5 MW, but what storage capacity does it have? 2.5 MWh, or 25 MWh or 250 MWh? In the first case with a 2.5 MWh capacity, the ESS might have the ability to level out short term fluctuations such as a cloud passing over the array, while if it has a capacity of 250 MWh, then it might have the capability of replacing 25% of the peak solar system output for a period of 100 hours, and be capable of acting as backup for several rainy days of low solar irradiation.
Without that important factor it is not really possible to provide much of a response to your question about dispatch, as to whether it will function for “regulation” to level out short term fluctuation, or as a true back up system – which is what is really needed.
Best wishes with your research project.
What is the mode of operation?
one sample for autonomous mode, is:
[1] H.R. Baghaee, M. Mirsalim, G.B. Gharehpetian, H.A. Talebi, “Reliability/Cost based Multi-Objective Pareto Optimal Design of Stand-Alone Wind/PV/FC generation Microgrid System”, Energy, vol. 115, part 1, no. 1, pp. 1022–1041, Nov. 2016, DOI: 10.1016/j.energy.2016.09.007.
[2] A.K. Kaviani H.R. Baghaee, G.H. Riahy, “Optimal sizing of a stand-alone wind/photovoltaic generation unit using particle swarm optimization”, Simulation: Int. Trans. of the Society for Modeling and Simulation, vol. 89, no. 2, pp. 89-99, Feb. 2009, DOI: 10.1177/0037549708101181.
By "ways", do you mean criteria to decide on dispatch amount?
Possible dispatch criteria:
1) dispatch sufficient ESS power to peak-shave load demand:
Article Cost-benefit assessment of energy storage for utility and cu...
2) dispatch based on dynamic tariff price (if available), e.g. dispatch at higher price to earn higher tariff:
http://www.mobilityhouse.com/en/charge-your-renault-zoe-at-great-rates-and-save-money/
3) dispatch to support grid stability, i.e. dispatch as an "ancillary service".
https://en.wikipedia.org/wiki/Ancillary_services_(electric_power)
http://iesys.com/assets/news/attachments/4.-Ancillary-Services-Stage1-Appendices.pdf
Article Energy Storage System for Mitigating Voltage Unbalance on Lo...
Depending on contract signed with utility, (1)-(3) above could allow utility dispatch at "their desired value".
Local user dispatch programming for (1)-(3) is possible too, but (2) & (3) would require still require utility approval of local control settings.
For (1), dispatch control depends on whether you are peak-shaving only your own load, or utility's load.
It's also possible to have password/lockout-tagout control that allows choice of local or utility dispatch control, depending on PV/storage system size & energy authority/commission regulations.
If the storage capacity in terms of MW into hours is high , then leaving a margin for peak shaving, remaining can be scheduled and hopefully Long , medium and short term open access rules and some understanding with Utility will govern the transaction. ESS (battery based)can be an ancillary service and work exactly like a pumped storage plant if sized properly.
Since regulations in this regard are still being debated, a clear picture may emerge gradually. For example since ESS shall provide a reliability support , it should be entitled to charge for its reliability support. The charging of the ESS (battery) shall be at light loads and it shall be entitled to lower grid tariff.
Since ESS is still a costly and space consuming source it should better be a captive system of an utility used and sized and managed to improve it's service reliability , and not used as a separate Renewable energy entity.
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