As the amount of solar on the grid has gone up, so too has the opportunity for utility scale solar PV plants to participate in the real time energy market. In California, that’s accomplished through a system called CAISO ADS.
The California Independent System Operator (CAISO) regulatory committee developed the Automated Dispatch System (ADS) to communicate real time dispatch instructions to energy market participants. This functionality allows utility scale plants in California, including solar PV, to bid into the real time energy market.
CAISO ADS is essentially a web-based messaging system that sends out dispatch commands. It replaced the old telephone and EMS-based methods of dispatching imbalance energy in the real time market.
It all comes down to money. Energy generators can realize financial incentives from CAISO by receiving and reacting to ADS instructions for real time power generation requirements. These include accepting commands for more power at a higher bid price, or accepting curtailment requests to support grid reliability.
This gives energy generators far more flexibility. If you are a generator and don’t participate in the real time market, you’re paid a set amount depending on the “day ahead schedule” for your kilowatt or megawatt generation. By getting into the ADS market, you can supplement that. Let’s say that you bid into the market yesterday at $10 a megawatt. If prices are up today and you have reserve, you can capture that extra money by ramping up to meet CAISO demand.
The CAISO ADS User Guide and the ADS section of the CAISO Business Practice Manual (BPM) contain in-depth information about how the system works and the participation requirements.
The first step is to apply for the ADS system. This is often done at the same time as the other paperwork for starting with CAISO. If you are granted participation, you build a log-in and receive a security certificate that allows you to securely connect to the CAISO ADS web services server.
CAISO sends out dispatches, called DOTs (Dispatch Operating Targets), typically every five minutes. They’re displayed through the CAISO ADS web client using a GUI (Graphical User Interface). Participating plants must monitor these requests and react accordingly by adjusting SCADA parameters to meet the requirements. This must be done within minutes and adhere to ramping requirements.
This requires a plant operator to continuously monitor the web GUI. The operator must watch the screen, get the new setpoint, go over to the control system for the plant, and adjust the settings accordingly.
If you’re thinking that sounds like a lot of manual work for what’s called an automated dispatch system, you’re right. It may be automated on CAISO’s side, but they’ve yet to automate it on the operator side. The ADS isn’t integrated into the plant’s SCADA system.
This takes many solar plants by surprise when they first sign up for the CAISO ADS system. They assume that the process will be automated (and no wonder, from the name)...but it’s not.
The good news is that there is a way to automate the process.
One of our engineers at Nor-Cal, Ambrish Ambekar, developed open source coding that enables automatic awareness and acceptance of ADS requests. Nor-Cal’s code seamlessly integrates with any local SCADA system to automatically perform all required changes to meet CAISO ADS requests. It also eliminates the possibility of operator error.
In other words, it truly automates the ADS process. Solar PV plant operators don’t have to sit in front of a screen and babysit the system all day long. They have time to monitor other things and take care of business, without having to worry about tracking that DOT every five minutes.
While there are a few ADS solutions on the market that do something similar, the coding and implementation requires purchase. We’ve elected to release our ADS facilitation solution as free open source code. We want to make the renewable power generation industry stronger by making it easier for solar PV plants to participate in the real time market.
The code can be implemented on any host computer that is at site level on the same land as the solar site controllers. In other words, on a computer that’s at the solar facility. The computer must have the CAISO security certificate code embedded in it.
With the proper CAISO generated certificate and code installation on a site’s SCADA or Historian server, real-time dispatch instructions will automatically make plant changes as necessary to meet the power demands of CAISO.
The Nor-Cal CAISO ADS solution is currently in use at over 10 solar plants in California, including the Tranquility site and several ConEd sites.
The open source code can be downloaded free of charge here.
If you’d like more information about this topic, or are interested in speaking with Nor-Cal regarding open source code implementation and how we may help you, please contact us.