As the second anniversary of 9/11 passed, Americans marked national progress along a number of fronts. Airport security enhancements are seen and felt daily by thousands of travelers, Vice President Dick Cheney's exact whereabouts at any given moment are well obscured, schoolchildren practice lockdowns and other emergency drills on a regular basis, and of course we all have our stash of duct tape on hand at home in the event of a chemical or biological attack.

Progress in the area of national energy security is less clear-cut, however. Though not perpetrated by saboteurs, this summer's largest blackout ever has caused state, local, and federal government officials, utility staff, and regulators to reexamine physical plant and operations for weak links. It has also stimulated renewed interest in the advantages that today's distributed energy (DE) technologies offer to power users, local utility distribution systems, and the electricity grid at the state, regional, and national levels.

DE technologies allow businesses, plants, and residences to remain lit, heated and cooled, and operational when the grid hiccups or fails. They possess significant advantages in efficiency and environmental performance over conventional technologiesæadvantages that translate to meaningful cost savings for energy customers. DE technologies offer attractive alternatives to building expensive (and exposed) electricity distribution infrastructure. In fact, each new DE installation improves the situation of not only the energy customer using the system's output but the surrounding community as well.

The array of currently available and under-development DE technologies and systems is truly impressive, and the benefits to be gained from widespread adoption are even more so. The DE industry works vigorously to heighten awareness about DE technologies and their benefits on the part of policy-makers, regulators, permitting agencies, power users, and the general public to help energy customers and the nation realize these benefits.

The purpose of this publication, and of this column in particular, is to build your awareness of DE technologies and how they can help you enhance the reliability and reduce the cost of the power on which your operations and facilities depend. Appearing in each issue of DISTRIBUTED ENERGY, this column will highlight a different technology or set of technologies, the applications for which it is suited, the specific benefits it offers, and where and how customers are deploying it.

Have you been thinking about how convenient it might be to have a cache of stored electricity at your site? Wondering whether your facility could benefit from free solar energy? Questioning how DE systems would interface with your existing equipment and building controls? I encourage you to e-mail me proactively with your questions and information needs, as specific or general as they might be. With your input, I can tailor each column to provide a high return on your investment in reading it.

Your reactions and opinions are vital to manufacturers, energy service companies, the federal government, and others who are striving to bring the DE products and services you need to your doorstep. If you have comments on what appears in this space, send your thoughts my way to see your issues addressed here.

As a conversation starter, I'm devoting the remainder of this space to a brief look at some DE technologies and surrounding critical issues. I hope to hear from you soon!

Distributed power generation technologies devised to date fall into five major categories: steam turbines, industrial (gas) turbines, microturbines, reciprocating engines, and fuel cells. This equipment can operate on a stand-alone basis to supply electricity to a facility, a group of facilities, a campus, or a microgrid, or it can be coupled with heat-recovery equipment for combined heat and power (CHP—also known as cooling, heating, and power) applications. CHP systems recover heat thrown off by power generation units and use it to produce steam, hot water, or chilled water that in turn supplies space conditioning systems or industrial process equipment.

A majority of the existing potential for CHP nationally falls into the smaller, building-size applications. The table below summarizes technical, economic, and environmental basics for the technologies commonly used in building systems.

Issues that can impede or enhance your ability to specify, install, and operate this equipment at your facilities are legal, technical, economic, and environmental in nature. Examples include rules and costs associated with interconnecting the equipment with the local electric utility grid; whether the system triggers federal emissions review procedures; the types of state and local permits required, as well as associated permitting processes; and the equipment's size, shape, weight, and maintenance schedule. The DE community is quite passionate in its commitment to establishing the best possible environment for DE and is increasingly successful in leveraging public and private resources to address the spectrum of issues.

Fuels are another hot topic, with instabilities in natural-gas prices and electricity deregulation combining to give power users major headaches, or worse. Natural gas is the favored fuel for many DE power generation technologies—but it is also the favored fuel for new central power plants, which represent a much less efficient use of this premier fuel. Renewables, such as wind, solar, and biomass, are just beginning to gain a foothold in DE and appear to offer much promise as systems for targeted applications are developed and refined.

	Cost and Performance of Distributed Generation Technologies for CHP Systems

Hybrid power systems combine different power generation devices or two or more fuels for the same device. When integrated, these systems overcome limitations inherent when components operate separately. Hybrid power systems offer lower fossil fuel emissions and continuous power generation for times when intermittent renewable resources, such as wind and solar, are unavailable. These systems are finding their way into high-visibility demonstration sites around the country.

Thermally activated technologies operate wholly or partially on heat energy. When integrated with onsite power generation equipment, they provide what is in effect “free” space conditioning. Absorption chillers produce chilled or heated water for air conditioning or space heating purposes. They operate by absorbing water vapor into, and then releasing it out of, a chemical solution. Desiccant dehumidifiers use a drying agent to remove water from the air streams that condition building space. Desiccant units can work in concert with chillers or conventional air-conditioning systems to significantly increase energy system efficiency by allowing chillers to cool low-moisture air.

Both absorption chillers and desiccant dehumidifiers can be powered directly by waste heat from an onsite generating unit, by steam, or by natural gas. They can also operate using heat thrown off by engine-driven chillers, which are essentially conventional chillers driven by a reciprocating engine instead of an electric motor. In a renewable-energy configuration, solar concentrators/chiller systems can use sunlight as a load-following fuel source to meet afternoon cooling demand, with solar energy collectors powering an absorption chiller.

Energy storage devices include those that store electricity directly, such as batteries and flywheels, and those that turn electricity into storable thermal energy—for example, in the form of ice or crystal solutions. Batteries, flywheels, and other uninterruptible power supply (UPS) devices are critical for facilities that cannot tolerate even split-second losses of power. Thermal storage is attractive for facilities that can use cheap, off-peak electricity to make chilled water to supply air conditioning during on-peak periods. Critical issues for users of both types of systems are primarily technical and economic; size, weight, cost, and how much power can be stored represent potential obstacles. UPS and thermal storage systems can be integrated with the onsite power generation and thermally activated equipment described above in a variety of configurations to meet facility energy needs.

Finally, industry teams are developing and offering packaged CHP systems that combine formerly separate power generation and thermally activated components into one streamlined unit with simplified controls. These preengineered systems can cut CHP system capital costs and reduce installation time significantly, with designs that are modular and created to be easily replicable.

CJ CÓROVA is a consultant with D&R International's Clean Energy Systems Team in Silver Spring, MD. She previously served as vice president of market development for the American Gas Association and as publisher of EnergySolutions magazine. She can be reached at cordovacj@hotmail.com.

DE - Nov/Dec 2003