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Utility Infrastructure and Asset Deferral

Premium Power's Zinc-Flow® energy storage systems enhance the reliability, stability, and operability of utilities' generation, transmission, and distribution assets through:
  • Asset Deferral: Providing load support to transmission and distribution (T&D) infrastructure, e.g. substation transformer banks, during periods of peak system demand, using energy generated off-peak.
  • Peak Demand Management: Using energy storage to shave customers' peak power draw from the grid, thus reducing the requirement for utility supplied peaking generation capacity, which is typically only used during periods of high system demand.
  • Peaking Power Supply: Reducing the need for expensive-to-operate fossil-fueled peaking generators that may operate infrequently, or displacing high-priced energy purchased from wholesale markets during periods of peak demand.
  • Energy Arbitrage: Time-shifting cheaper off-peak energy from base-loaded nuclear or fossil plants, or from variable wind and solar energy resources, to be available during daytime on-peak hours.
  • Voltage Support: Maintaining system voltage at the far ends of long radial distribution lines, especially in areas of high load growth. Energy storage also provides a source of back-up power in the event of problems with the distribution lines.
  • Ancillary Services: Frequency regulation and demand management.
Utility-scale energy storage systems will become integral parts of tomorrow's Smart Grid. Via extensive deployments of energy storage systems, the electrical grid will be more responsive to fluctuating system demands, enhancing the balance between power and energy demands, and system (generation, transmission, and distribution) capacity.

Power StationEnergy storage can significantly benefit electrical T&D networks by reducing, or deferring, capital investments. Restructuring, continued demand growth, and low investment rates have conspired to make the management of the power grid not only more difficult in recent years, but also an area of growing concern for the future. TransFlow® units designed to support T&D networks have the ability to quickly inject energy and maintain this energy flow over several hours, rather than replacing power generators' role of providing bulk-energy to the grid.

TransFlow® installations alleviate both the lack of T&D capacity and the stability problems that ensue during periods of high demand. Sited beyond a T&D bottleneck, they provide a pre-positioned source of energy, which allows the system to 'ride through' a few short-term peak demands - postponing the need for an expensive upgrade at the substation or on the line until a more sustained level of demand warrants an upgrade. An added benefit is that the power lines experience greater overall - but less intense - use and wear through reducing overloaded lines (peak power transfers that rise above rated limits incur far more wear and tear on a line than pushing additional power through the line at night when the utilization is low). Deployed throughout a utility's system, energy storage systems will also reduce the peak power generation capacity required during periods of elevated power consumption.

Providing utilities a means to better control the timing of their distribution system upgrades would be a windfall to these firms struggling to provide an ever-increasing level of reliability with diminishing resources. Because of the very wide demand needs, the loading on any particular power line can be extremely variable with a low overall utilization. Currently, whenever such power line becomes fully loaded, even for a short period of time a few times per month, the entire line's transmission capacity is then upgraded by about 1/3, a level deemed sufficient to preclude another upgrade for some time to come. Operating in this way without a storage component, the power T&D system must obviously be built-out so that it is capable of meeting the greatest demand under harsh conditions. However, as we've seen, it is not the entire system that reaches constraint, but single points in the system.

powerlinesUpwards of $13 billion is added to the capital infrastructure base each year: $3 billion in the transmission and $10 billion for the distribution market. This is needed to keep up with demand. Over the last 10 years, demand growth in the United States has increased 20%, including a shift toward higher reliability. Meanwhile, existing T&D equipment continues to age, with much of the existing infrastructure approaching or surpassing its design life. A key strength of TransFlow® units over traditional expensive capital upgrade solutions to counter reliability and capacity problems is the multi-functional capability of the unit. Often, it is not simply real power that is needed; rather, voltage control and even regulation are also required. By providing such system stability support, energy storage technologies can also help to avoid the need for more expensive power stability and control equipment. The evaluation of energy storage technologies for this purpose has been undertaken for many years with many findings in storage's favor. PG&E concluded in 1994 that a 1 MW, 2-hour duration battery storage system (10 year life) priced at $700/kW could enable the profitable deferral of one additional substation each year. In fact, TransFlow® systems can perform these tasks for a fraction of this cost.

Included in this role for Zinc-Flow® technology at the utility substation would be to provide grid-level, active power quality enhancement. This would require TransFlow® grid-scale units, able to provide rapidly altering charge and discharge cycles to improve customers' power quality. Power quality is a growing problem for United States businesses, with estimates ranging upwards of $150 billion (US DOE) each year in lost production or damaged equipment from poor power quality. Surprisingly, more than 90% of these power quality disturbances are short-term, lasting for less than 2 seconds, and 98% last for less than 30 seconds according to the Electric Power Research Institute (EPRI). Placed at a substation, a large storage system would subsume the role of substation backup power, effectively combining the two facilities in those places that deployed such a unit.

References:
Energy Storage Benefits and Market Analysis Handbook, Eyer, J., Iannucci, J., Corey, G., Sandia National Laboratories, Albuquerque, NM, 2004. Page 3. SAND2004-6177

Getting Electricity Where it is Needed, Edison Electric Institute, June 2001.

Cost Analysis for Energy Storage Systems for Electric Utility Applications, Abbas, A., Swaminthan, S., and Sen, R., Sandia National Laboratories, Albuquerque, NM, 1997,p.14, (SAND97-0443)


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