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An Electric Utility Perspective on Applications of Electricity Storage for Distributed Generation Workshop on Advances in Electricity Storage in Support of Distributed Renewable Energy Based Systems Monday, May 10, 2004 Hyatt Regency Waikiki. Bradley R. Williams, PE
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An Electric Utility Perspective on Applications of Electricity Storage for Distributed GenerationWorkshop on Advances in Electricity Storage in Support of Distributed Renewable Energy Based Systems Monday, May 10, 2004 Hyatt Regency Waikiki
Bradley R. Williams, PE
Director, Power Delivery Business Technology
PacifiCorp, Portland, OR
DGUtility Distribution Applications best Suited to Distributed Electricity Storage
Power quality and reliability
Energy management applications
Spinning and standby reserve
Load factor increase
Integration of renewables
100-MW and above
Vanadium Redox Batteries are a type of energy storage system (“VRB-ESS”) - flow batteries capable of storing electrical energy and deploying it back to the grid when required.
The VRB-ESS is charged like any other battery, but the energy is stored by chemical changes to the electrolyte. The electrolyte is a solution of ionic forms of vanadium in a dilute sulfuric acid that are electrochemically oxidized or reduced to store the energy. The acidity level of the electrolyte is no greater than a conventional car battery.
The electrolyte is pumped from separate plastic storage tanks across proton exchange membranes in the cell stacks, creating a current. The reaction is reversible, allowing the battery to be charged, discharged, and recharged with high efficiency.
Castle Valley VRB System
The battery provides DC power. Therefore, an inverter is used to convert it to alternating current when it is returned to the electric delivery system.
Also involved: control, monitoring, and temperature regulation systems
V2+ and V3+
V4+ and V5+
- dc Power +
Vanadium sulfates in H2SO4
V2+ V3+ + e- 
V5+ + e- V4+ 
Using a VRB can smooth the power supplied, making it more constant
The VRB can provide reactive energy through the AC/DC converter
The VRB is an environmentally friendly alternative to diesel generators and larger lead acid batteries
BRenewable Energy Applications
Wind output is variable so capacity is discounted by > 75%
VRB can firm supply and increase capacity and efficiency
renewable energy source
Generator (1,000kW 6 hours/day 320days/y) –1,920,000kWh/year
VRB-ESS 1,000 kW 1,000kVAR for 6 hours storage
NPV = $5.6million
ROI AT = 23%
Profile Without Storage
Profile With Storage
Courtesy Regenesys – Mr. Mark Kuntz