Distributed Energy Resources (DER) - DER Aggregator Function

Contents

• Narrative
• Steps

Narrative

The purpose of the distributed generation aggregator activity is to enable a mechanism whereby a system operator can call on customers during peak periods of energy usage and who have backup generators to disconnect from the power grid and power themselves with their generators.

In areas with high energy costs such as New York City, load curtailment programs have been initiated where facilities can make use of on-site generators that provide back-up power and use them to supply peaking, reserve or load management capability.  In many instances, the size of the generators are in the 1 MW or so range and to make economic sense, it is necessary to aggregate multiple units together into one virtual power plant that can be dispatched as would a normal power plant by system aggregators.  The system aggregator is responsible for the collection and aggregation of DG units.  They generally have a contract to split revenues with the owners of the DG units.  The system aggregator is the point of interface to the system operator.  The system aggregator also maintains a control room and responds to calls and inquiries from the system operator before, during and after generation.  The system aggregator generally owns and maintains all communication channels to the DG units as well as all of the monitoring equipment used for performance verification.  The system aggregator is responsible for calculating settlement and verification with the system operator and distributing payments to the DG unit owners.  The DG owners maintain the DG units and usually are responsible for starting and stopping the units.

A typical scenario would be as follows.  It is August in NYC and the temperature has hit the high 90s for the third straight day.  As the system peak continues to rise, the NYISO forecasts that there could be an energy shortage the following day.  In response, the NYISO asks approved system aggregators if they could shed load.  In particular, the NYISO asks system aggregator #1 if it could supply 5 MW.  The system aggregator then contacts its customers that are under contract if they could run their generators the following day.  The system aggregator then totals the amount of expected load that is expected to be relieved from the grid the following day and submits that to the ISO.  The system aggregator will try to obtain enough willing customers so that they can reach the 5 MW goal for the day.  When the next day arrives, the system aggregator then follows up with each customer to remind them to disconnect from the power grid and to start their generators.  The system aggregator and/or system operator monitors over the Internet the output from each generator and totals them to ensure compliance with the 5 MW load.  It is important to get near what is asked for maximum revenue can be obtained and to avoid penalties.  If a generator fails to start, the system aggregator attempts to get another customer to start their generator.  At the end of the day, the generators are stopped and data is collected that is used to verify compliance and to calculate bills that go to the ISO.  The system aggregator submits the bills to the ISO and once payment is received, the corresponding revenue is sent to the DG unit owners.

 

Steps