We like the vanadium redox flow battery from VRB Power Systems, Inc - so much in fact, that we asked to become a sales affiliate a couple of years ago.  This energy storage system offers multiple options for service and I suggest the following as a potential application.  This is the first installment of at least two posts. Your thoughts and comments are welcome.

Situation: Consider a semi-conductor industrial manufacturer with a nearly flat load of 7.5 MW 24/7.  This plant needs good power quality - a shut down due to a power quality event can cost $500,000 per hour in scrap and downtime.  To avoid curtailment and rolling blackouts during the California Energy Crisis of 2001, this plant invested $1.6 million to construct a pad and connections for 10 MW of mobile diesel generators.  Rental of the generators cost $400,000.

This plant also has a dedicated 33kV line to the utility substation to improve power quality and reliability.  In spite of all this, they still had a two hour outage in May due to a short circuit at the sub.

Solution:  A proposed solution to their problem is a 5MW VRB ESS (energy storage system) with 4 - 8 hours of storage (20 - 40 MWhrs) and advanced power conditioning system, located on the customer side of the utility meter.

UPS:  The ESS is warranted to over generate 50% for 10 minutes each hour, allowing it to provide full facility coverage (7.5 MW) to protect against transient power quality events.  In fact, the VRB-ESS is capable of providing a short-term power output of approximately 5 times nominal for periods of 1 minute in every hour (handy for large motor startups). The response time for this is virtually instantaneous of the order of 5 milliseconds. The PCS has to be rated accordingly.

Emergency Power:  With the storage in the system, the industrial customer has hours of power to ride through short-term curtailments and allow for orderly shut-down in case of a long term emergency. 

Why the VRB?:  One could argue that any large lead acid battery UPS or flywheel and diesel generator system could provide the same benefits - why the VRB?  Cost, life cycle, disposal, and environment are a few of the issues in favor of the VRB.

Cost:  I'll provide more information on this topic in my next post, but much of the cost of the system can be subsidized by selling energy services to the regional grid operator - the California Independent System Operator (CAISO).  This UPS can pay for itself!

Life Cycle:  Without going into technical detail, this system has a life of 25 years or more without degradation from repeated use.  This is a feature of flow battery technology.  More information on flow batteries in general can be found at Wickepedia.  The Wickpedia link to vanadium flow batteries is here... Life is extended by replacing the proton exchange membrane in the energy cell in years 12-15.  The electrolyte does not degrade or wear out.  In addition, the system needs very little maintenance and is designed to be monitored remotely.  By comparison, lead acid batteries and diesel gensets require extensive maintenance and on-site monitoring.

Disposal:  The electrolyte does not need to be replaced, so disposal is not an issue.  No lead, cadmium or other hazardous metals are involved.

Environment:  The system does not generate emissions, unlike a diesel generator - which has to be fired up every month for maintenance.  In fact, in the next post, we'll see how the ESS reduces emissions from grid connected power generators by 70%.  The ESS is a clean tech system - no disposal, no hazardous metals, and GHG emission reduction.

Next:  In the next post, I'll explain how the system can pay for itself, how it can be used to integrate renewable energy, why the utility likes it, and what some of the challenges are to installation.