|Distributed Energy Storage (DES) demonstration with GM Volt battery pack and ABB PQF inverter. Source: GM. Click to enlarge.|
In conjunction with the Plug-in 2011 event in Raleigh, NC, GM and ABB demonstrated a lab prototype of a distributed energy storage (DES) system that combines Volt battery technology and a proven grid-tied electric power inverter.
Earlier this year, General Motors signed a definitive agreement with ABB Group to identify joint research and development projects that would reuse Chevrolet Volt battery systems, which will have up to 70% of life remaining after their automotive use is exhausted. (Earlier post.) Using Volt battery cells, the ABB and GM team is building a prototype system for 25-kilowatt/50-kWh applications, about the same power consumption of five US homes or small retail and industrial facilities.
Our target during this project has always been a field demonstration, putting it out in the field with used batteries and appropriate electronics to support the grid. The first step toward this field demo is to build a lab prototype. We took a production battery, a production inverter, made the necessary modifications and found that it could perform the function needed.
There are essentially three elements in the application: the grid, the utility company, the consumer—the new part is the battery. This could be an asset owned by the utility. If the consumer wants to consume a lot of power, the utility could choose to deliver it from the battery. The utility can control how it delivers power to the consumer, either from its own generator or possibly from stored energy in the battery. At the lab, we made a set up that demonstrates exactly this.
The Volt battery is charged and discharged according to a use profile appropriate to the application. The next step is adding an additional function—backup power—in a scenario where if the utility is unable to deliver power it can use the battery to support the consumer.—Sandeep Bala, ABB Power Electronics R&D Engineer
The GM/ABB system could store electricity from the grid during times of low usage to be used during periods of peak demand, saving customers and utilities money. The battery packs could also be used as back-up power sources during outages and brownouts. Recent research conducted by GM predicts that secondary use of 33 Volt batteries would have enough storage capacity to power up to 50 homes for about four hours during a power outage.
ABB has determined its existing power quality filter (PQF) inverter can be used to charge and discharge the Volt battery pack to take full advantage of the system and enable utilities to reduce the cost of peak load conditions. The system can also reduce utilities’ needs for power control, protection and additional monitoring equipment. The team will soon test the system for back-up power applications.
|Role of the PQF filter. Click to enlarge.|
There are three significant sources of poor power quality caused by a variety of loads in customer installations, notes ABB: harmonic pollution; load imbalance resulting in voltage imbalance and phase to neutral voltage; and reactive power.
ABB PQF active filters can be applied to small, medium or large applications and are suitable for both industrial and commercial installations. They provide harmonic mitigation, load balancing and step-less reactive power control for inductive and capacitive loads.
An ABB PQF active filter is power-electronics-based electrical equipment that is installed parallel to the polluting loads. It monitors the line current harmonics, as well as the customer requirements programmed by the user. It can then generate for each harmonic frequency a compensation current in perfect phase opposition to the polluting current. The two harmonics effectively cancel each other out so that the feeding transformer sees a clean sine wave.
Our tests so far have shown the viability of the GM-ABB solution in the laboratory and they have provided valuable experience to overcome the technical challenges. We are making plans now for the next major step – testing a larger prototype on an actual electric distribution system.—Pablo Rosenfeld, ABB’s program manager for Distributed Energy Storage Medium Voltage Power Products
As part of sharpening its focus on reuse and recycling, GM has appointed Pablo Valencia to the new position of senior manager for Battery Lifecycle Management. Valencia and his team will focus on assuring battery systems used in future Chevrolet, Buick, GMC and Cadillac vehicles provide environmental and societal benefits beyond their use in the vehicle. Single-source responsibility assures the design of future battery systems is compatible with reuse and recycling applications.