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Energy Storage: It's Not Just Load Leveling Anymore

Fortnightly Magazine - August 1998

Hybrid renewable systems integrate photovoltaics or wind power with storage and generator sets for grid independent and remote power applications. Larger systems may be used at distribution sites to meet peak loads while smaller systems may be used for residential applications. It's anticipated that hybrid renewable systems also will become more widely used for grid-tied applications.

Development Barriers, Research Initiatives

Despite the advances in energy storage, many barriers still exist for product commercialization. Consider three primary roadblocks:

n System integration, including power electronics;

n Need for improved energy storage and power conversion components (batteries, flywheels, superconducting magnets, etc.); and

n Compelling the quantification of the value of energy storage.

The majority of operating energy storage is in the form of battery energy storage (BES) that relies on flooded lead-acid and valve regulated lead-acid (VRLA) battery technology. A recent Frost & Sullivan market analysis indicated significant potential for BES technology in the U.S. %n5%n There are about 60 MWh of lead-acid batteries in electricity delivery installations in the U.S. In 1995, one MWh was added for PV applications. Every year, that number increases with growth in the photovoltaics market. %n6%n There are about 5 MWh of the more advanced VRLA batteries installed in demonstration projects in Alaska and California.

Perhaps the most important technical and business barrier is refinement of integrated systems for unmanned, turnkey operations. This step will require sophisticated system engineering of available energy storage products. These systems integration issues relate to distributed technologies such as photovoltaics, fuel cells and hybrid power systems. Improved electronics and controls are critical, including high-power, fast-switching, inexpensive, and reliable power conversion electronics.

Much progress remains to be made to improve the critical energy storage component. In particular, the reliability of energy storage and power conversion components must be improved so that the "up-time" for systems reaches electric utility industry standards. Parasitic losses need to be reduced. In some cases the round trip efficiency of the energy storage component needs to be increased to reduce the costs for charging the energy storage system. Flywheel rotors, superconducting magnets and ultracapacitors are just now emerging from research laboratories and being incorporated into integrated systems. Some technologies need significant manufacturing engineering. Only then can they be used in high-volume production so that costs can be reduced to competitive levels. Recent progress in superconducting magnetic energy storage and flywheel energy storage has made these technologies increasingly viable energy storage options in the U.S.

The value of storage has proven difficult to quantify, and as a result, recovered value for existing energy storage projects in the U.S. has been lower than expected. This means that larger volume production has been slow to materialize. Costs have remained relatively high. Battery systems, for example, including controls and electronics, typically cost $1,000 per kW. The industry goal is to reduce that cost to $400 per kW. With a commercial market for electricity, however, the real value of energy storage should become apparent to users.

The Department of Energy with the Sandia National Laboratories collaborate with industry in cost-shared projects that will increase the efficiency