CHARACTERISTICS

The integration of dispersed generation, particularly renewable energy technologies that are intermittent generators (i.e., solar and wind power) is facilitated by dispersed energy storage systems. Energy storage systems use electricity during non-peak hours or from intermittent sources to convert water to ice or chilled water (for cooling), or to store energy in batteries. During peak periods, this stored energy can be converted back to electricity for use.

The use of these systems, in addition to filling the traditional role of meeting peak demand needs, increases overall system efficiency and reduces total system losses. A reduction in generation demand and GHG emissions results. The utilization of dispersed energy storage systems also reduces GHG emissions by allowing greater use of local low- or non-carbon fueled generation systems at the local level.

Use of dispersed storage systems will enable utilities to lower costs through deferrals of upgrades and new construction, supply new generation to customers, and improve reliability. The use of dispersed energy storage systems throughout the distribution system will improve dynamic operating capabilities and asset utilization, allowing existing generation to function more efficiently and improve the overall efficiency of the system. Emerging energy storage systems, which can be dispersed throughout the distribution system include batteries, flywheels and superconducting magnetic energy storage (SMES).

SIZE:
Uninterruptible Power Supplies and other forms of disbursed storage and generation range from a few kilowatts to several hundred kilowatts.

FEATURES:
Chilled water or battery storage systems

COST:
Installed costs of such units must be competitive with the low end of alternative forms of supply with installed costs under $450 per kW.

CURRENT USAGE:
Many companies are using dispersed energy storage systems. For instance, the U.S.-based Southern Company will begin to use dispersed energy storage (with a number of other T&D system upgrades) and expects to reduce distribution losses by about 15,000 MWh per year by the year 2000.

POTENTIAL USAGE:
Development of these systems is key to successful and widespread deployment of renewable energy systems.

ISSUES ASSOCIATED WITH IMPLEMENTING ACTION

• Dispersed energy storage equipment has a high capital cost, and low energy capacity is available from existing dispersed storage technologies.
• Energy storage systems dispersed throughout the system may require additional dispatch and control systems.
• There is a lack of planning practices that fully assess the value of dispersed storage and generation.
• Dispersed resources may not all be under the ownership of a single company. This poses challenges in the control, protection, operation, and maintenance of distribution systems.

CLIMATE CHANGE IMPACT

EMISSION EFFECT:
    

CONDITIONS FOR EMISSIONS MITIGATION:

• Unless the source of power to charge storage devices is non-carbon fueled generation, use of storage would actually increase, not decrease, emissions of greenhouse gases as the overall efficiency of a generator and a storage device is lower than the straight generator itself.

EMISSION ESTIMATE:
Varies according to fuel source of the charging device.

COST-EFFECTIVENESS:
N/A

SECONDARY EFFECTS:
Varies according to the fuel source of the charging device.

RESOURCES

• Demonstration projects underway include the Electric Power Research Institute (EPRI) Battery Storage Project at Southern California Edison; the Puerto Rico Electric Power Authority (PREPA) 10 MW battery storage system, with Sandia National Laboratories assistance on performance testing; and a Metropolitan Edison/GPU study to determine if a battery storage facility to "shave" peak load for a specific application is feasible and/or practical. This dispersed storage project would reduce transmission losses in addition to peaking requirements.
• The U.S. Department of Energy sponsors an Energy Storage program to aid in the transfer of dispersed storage technology to utility systems.
• EPRI's Engineering Handbook for Dispersed Energy Systems on Utility Distribution Systems (TR-105589) provides a summary of available information on methods and tools for evaluating dispersed energy systems from economic, reliability, and power quality perspectives. The handbook identifies the costs and benefits, integration and engineering requirements, and projected performance of expansion options and also includes general background on development, methods for including dispersed energy sources in distribution planning, and application issues such as system protection.

CONTACTS

Harza Engineering
Peter Donalek
Electric Power Systems Department
Chicago, IL
Tel: (312) 831-3170
Fax: (312) 831-3999
pdonalek@harza.com
http://www.harza.com

National Rural Electric Cooperative Association (NRECA)
James Willis
International Programs Division
Arlington, VA
Tel: (703) 907-5669
Fax: (703) 907-5532
jim.willis@nreca.org
http://www.nreca.org

U.S. Department of Energy
Russell Eaton III
Office of Project Management
Golden, CO
Tel: (303) 275-4740
Fax: (303) 275-4753
http://www.doe.gov