New technology has made the business world more sensitive to the quality and availability of electricity. At the same time, reliability problems in deregulated markets have been created by:

Pre-existing regulations

The use of older, less efficient, and less reliable equipment

Heavy reliance on hydroelectric power during a period of prolonged drought Companies depend more than ever on modern electronics, which are powerful and demanding, but sensitive. Desktop computers, high-tech medical devices, and computer-controlled production line control systems demand uninter- ruptible, high-quality electrical energy to achieve the 99.9999% reliability required by their owners.

Business-to-business (b2b) and Internet companies must keep their services available on a continuous basis to meet customer demand and to keep their competitive edges. Data loss is not acceptable, and damage to sensitive equipment resulting from power disturbances can be expensive. Vital facilities, such as hospitals and many continuous processes, such as semiconductor manufacturing, can be completely disrupted by power failures. In addition, businesses face the constant need to reduce operating costs whenever possible. This includes reducing electricity use, especially during peak usage periods when rates are highest.

The traditional electric utility cannot meet the requirement for extremely reliable electrical service by high technology companies. Power disruptions caused by high winds, flooding, and tree limbs falling on power lines usually accompany storms and lightning. Winter storms can coat power lines with ice and bring down miles of lines. Vehicles hitting power poles, vandalism of substation equipment, equipment failures, and unusually high loads can also strain utility service. Utilities and plant owners can anticipate but not avoid these events. Provisions to avoid outages from these causes must be made closer to the process on the customers' premises.

On-Site Systems

On-site systems guard against lost productivity, limit damage to refrigerated inventory, and reduce safety and security concerns.

Consequently, many businesses are investing in on-site electrical power backup and generation systems to provide the missing reliability they need to operate 24/7 and to reduce costs.

On-site power solutions use small-scale generation at the energy user's site to provide power when utility power is not available. The generation plant may or not be interconnected with the utility grid, but interconnectivity is increasingly common. On-site electrical power backup and generating systems are readily available in a wide variety of designs for specific uses and specific customer applications.

The most common available systems fall into seven categories:

• Diesel-fueled reciprocating engines

• Natural gas-fueled reciprocating engines

• Small gas turbines

• Micro-turbines

• Fuel cells

• Flywheels

• Uninterruptible power supplies (UPS)

No single solution meets all needs, and no backup system can be as efficient as the large-scale power generation facilities operated by the major electrical energy producers. Large modern combined-cycle power plants deliver an electrical efficiency rating of 50-54% higher heating value (HHV)-an efficiency index based on the heating value of natural gas.

Before configuring a system, energy managers must consider the efficiency of a system and a number of other factors, including:

• How long must the system supply power during transient conditions-fractions of seconds, seconds, minutes, hours, or days?

• What types of transient conditions will likely be encountered-surges, spikes, total outages, or dips?

• What are the local ordinances on emissions and noise?

• What fuels are readily available in the area and how much do they cost?

• What are the costs of energy and of downtime?

• What are the costs added to the product and does the business remain competitive once these are factored in?

Changing one factor can often affect one or more of the others.

Diesel-fueled reciprocating engines

These are the least expensive ($300-$500 per kilowatt) types of products. They are reliable, provide an electrical efficiency of 33-42% HHV, employ proven technology, and start quickly. Diesel fuel is easily stored on-site in tanks. However, diesel engines require a lot of maintenance and create exhaust and noise that must be controlled. Traditional diesel technology has just about reached its limits, and environmental concerns may relegate them to emergency use. Cleaner burning diesel fuels, additives, or co-firing (diesel and gas) may extend the life of this source under current restrictions.

Environmental regulations will greatly influence and complicate the future of hydrocarbon fuels such as diesel. Regulations concerning the use and type of diesel units are continually changing and vary significantly from locale to locale. Experience to date reveals local ordinances generally place tough restrictions on the use of these units.

Local ordinances governing on-site fuel storage, for example, are not consistent across the United States. Local governments directly influence the style and size of both above- and below-grade tanks.

Leak detection systems are required to provide continuous feedback of flow rates and tank levels. Monolithically poured (seamless) containment walls are still required around above-ground storage tanks, and installations must include provision for the removal of the tanks when replacement is required.

Apparent visible pollutants in diesel are often regarded as more objectionable than the NOx emissions. A requirement to reduce noise levels is now commonplace when locating diesel generators near residential areas or in areas that already experience high levels of ambient noise.

Natural gas-fueled reciprocating engines

Like diesels, these generator engines are relatively inexpensive ($500 to $750 per kilowatt), reliable, and employ proven technology. They are cleaner than diesels, however. Natural gas must be piped in, and installation of a fuel gas compressor may be required if the gas line pressure is not adequate. Maintenance requirements and noise levels are high. Efficiency is about 32-43% HHV.

Natural gas engines are used for emergency generation in limited specific customer and load types. Gas-fired units often cannot start fast enough for highly sensitive loads such as computers and microelectronic manufacturing facilities, which may require generators to start in less than 20 seconds. Supplemental sources, such as UPS units, can assist in carry-through, but during energy curtailment there is a high probability that when electricity is curtailed, natural gas delivery could also come to a halt.

Environmental and noise abatement rules governing natural gas reciprocating engines require additional equipment to clean up the exhaust and reduce noise levels. These measures can make project economics difficult to justify. Cleaner burning natural gas units are more desirable in special applications. Each site, today, requires a case-by-case study.

Small gas turbines

These turbines are best suited for use in distributed generation systems as a means of controlling costs during peak usage periods or for providing additional capacity.

Although viewed by many large electric utilities as competition, the widespread use of distributed generation systems could free up power grids and reduce the need for utilities to cut power to their customers during periods of heavy demand. There are approximately 1000 small gas turbines installed in the Unites States, although the exact number is not available since no permits are required for these units. However, as specific applications for this technology are identified and test results are tabulated, more complete data will become available in the next 12 to 18 months.

Gas turbines are relatively inexpensive ($500-$1,000 per kilowatt), reliable, and the technology is proven. Maintenance and emissions are lower than gas or diesel reciprocating technology. However, electrical efficiency is low at about 22-35% HHV, and they are noisy. A fuel gas compressor is usually required.

Micro-turbines

Micro-turbines are small versions of the turbines used by electric generation companies and some commercial enterprises. These units (30-500 kilowatts [kW]) are quiet and have low predicted maintenance. Electrical efficiency is low-about 22-30% HHV. They are expensive at $1000 to $2000 per kilowatt. Micro-turbines are still considered an emerging technology that fits into niche markets where "free fuel" such as biogas from landfill or digester gas is available. They can operate on fuels with low-energy content with low emissions. A Southern California landfill application showed NOx emissions of just 1.6 ppm. Another specialized application is oil and gas recovery where micro-turbines are eliminating highly polluting flares by converting unprocessed casing gas with up to 7% H2S.

Fuel cells

Fuel cells have been compared to batteries that can be refueled. They produce electricity from gasoline, methane, ethanol, or hydrogen. They operate quietly with very low emissions, but are expensive to manufacture. Electrical efficiency is low at 28-35% HHV, but the technology is still maturing. Currently, 250 kilovolt-ampere (kVA) units are the most efficient size, making fuel cells a specialized market solution today. While fuel cells show promise, they are yet unproven and depend on ongoing technological innovations to ensure their eventual economic viability.

Uninterruptible Power Supplies

UPS systems are most popular for critical equipment such as medical, telecommunications, and servers used for business-to-business and web solutions. Businesses using this equipment require readily available electrical backup.

UPS systems can generally support 5-9 minutes (min) of carry-through power instantaneously and can be stacked to provide longer periods of backup. Some telecom hotels connect the units in parallel to obtain up to 18 min of backup in the event of main power loss.

UPS maintenance costs include battery, capacitor and rectifier replacements, and the cost of battery disposal. Battery costs alone can represent up to 60-70% of the complete UPS system cost every five to seven years. The cost of a complete system is approximately $300/kVA. Battery replacement frequency depends on how deeply the batteries have been depleted and how quickly the current is drawn from the batteries during the depletion.

Flywheel UPSs are classified as battery-less systems. They spin constantly, with an occasional "bump" from an electric motor to maintain speed. They are well suited for applications that require a few seconds carry through and where the risk for power loss is low.

There are two main types of flywheel systems-low-speed and high-speed. Low speed flywheels normally spin at 7000 revolutions per minute (rpm), and provide 3 to 7 seconds (s) of carry through-useful for momentary interruptions experienced in local power sources. Recharging usually takes about 20 min. The low-speed units require less maintenance than the high-speed units. The mass of the wheel and the constant rotation will generally produce bearing problems such as wear and vibration.

High-speed flywheels are less common. They spin up to 100,000 rpm and use a lighter polycarbonate flywheel. The energy contained within the unit is available for 2 to 5 s to carry through specific pieces of delicate equipment during very short power disturbances. These units are expensive, and maintenance costs are difficult to predict -from low thousands of dollars per incident for minor maintenance to tens of thousands of dollars for bearing replacements and even more for flywheel replacement.

Cogeneration

Small factories and commercial businesses such as hotels, restaurants, and residential care facilities can use their generators in a cogeneration system to combine their need for electricity and thermal energy. Cogeneration projects use the heat recovered from cooling generators to heat processes or for heating or cooling facilities. A high thermal load will improve system efficiencies to 70 to 80%. Project value is increased and system economics substantially improved.

Power for Tomorrow

Paralleling the utility grid to achieve the required high-nines of reliability is becoming more common. However, the necessary reverse current, voltage, frequency and interlocking protection schemes (when required) are becoming more complex due to the shifting of the source load to remote locales. Although the role of distribution companies is somewhat reduced in today's environment, the need for higher quality power, which requires more intensive review and a larger scale of integration, has increased.

The emerging method of power service is to take a single point of feed from the local utility, filter and ensure 9 to 18 min of UPS carry through, and provide complete site power back-up with diesel or gas generators.

The system senses loss of grid power, starting the back-up power supply and automatically transfers to stand-alone mode, restoring power to the facility. When grid power returns, the sequence is reversed, returning the system to its normal operating state. Diesels are used when the starting requirement is 7 min, and gas is used when 20 to 30 s is required.

The reliability of facility power distribution circuits can be improved by using dual-power distribution feeds to internal substations. Redundant facilities such as this will be required for more facilities in the future, especially for the e-business world. This solution is available now.

Future Trends

The control systems linking these distributed generations sites together must do more than just "monitor" the site equipment. Energy managers may require control of the generators in order to support other business solutions. With full site redundant generators, the peak can be adjusted by paralleling generators and timing the sequence of operation.

Historically, controlling a distributed generation scheme was an expensive solution. Today, this type of control is technologically and economically feasible through the use of dedicated telecom circuits, VPN (virtual private networks), or on-demand dial-up. Seven years ago a dedicated T1 circuit operating at 1.544 megabytes per second (Mb/s) cost about $1100 per month. Today a DSL circuit through an Internet service provider supplying 748 Mb/s costs about $75 per month, depending on features and variations in service provider pricing. With this cost reduction, "global" control is as easy as calling your neighbor, and in today's environment a neighbor is a relative term.