Tuesday, October 24, 2006

The Industrial Sector: Energy Use and Waste

Industrial activity occurs in facilities that manufacture products. Certain basic products, such as fats and oils, pulp and paper, chemicals, petroleum refining, and primary metals production, are intermediate components which are eventually fabricated or refined into the products actually purchased by consumers. For example, an automobile is assembled from a vast array of intermediate materials, most of which were produced elsewhere before they were shipped to the point of final fabrication and assembly. The finished automobile contains material and sub-assemblies supplied by manufacturers of steel, aluminum, copper, glass, rubber, plastic, paint, and other intermediate products.

A manufacturing corporation may operate one or more production sites. Each site features a number of structures that are arranged on a campus-like setting. The volume and form of energy required by a manufacturing site is highly varied—it depends on the type of product being made as well as the design of the production process and the structures that house those processes. A “typical” industrial facility’s layout and energy consumption may resemble this diagram:
[Click on image to enlarge]
Source: Alliance to Save Energy

The entire site (1) is a large property suitable for hosting production facilities, offices, warehousing and storage, employee parking, and infrastructure for moving materials on and off the property.

U.S. industrial power houses (2), in aggregate consume about 18 quadrillion Btu annually. Power houses organize the energy needed to transform material inputs into a finished product. Material is transformed by adding and/or subtracting heat and applying force and pressure. Energy is used for motive purposes, i.e., pumping, cutting, lifting, sifting, stirring, rotating, folding, etc. Also, energy is used to control the atmosphere in certain production facilities. The power house may host boilers, turbines, air compressors, and electricity transformers and switchgear. Boilers create steam, which is an efficient medium for transferring heat. Steam can also be used to power a turbine that generates electricity. Alternatively, electricity can be purchased from a merchant and/or utility, in which case the power house merely transforms the purchased electricity into voltages required by the facility. Electricity is also used to operate air compressors. Compressed air performs a wide variety of functions—too numerous to list here. Note that industrial power houses experience energy losses as they convert fuel to heat and power. In the U.S., those losses are, on average, equivalent to eight percent of total industrial energy purchases.

The distribution infrastructure (3) transmits steam, electricity, and compressed air to buildings that host production activities (4). Distribution system losses are characterized by leaks and radiant heat losses, which on average add up to 16 percent of energy purchases. Another 16 percent of purchased energy is lost as heat and power are converted to work in the production facilities. Some facilities recapture residual thermal energy (steam, hot water, and combustion emissions) and return it (5) for reuse by the power house. Only 60 percent of industry’s purchased energy performs useful work, yet much of that waste can be economically recaptured.



At 10:31 AM, Blogger Sean Casten said...


Great points, but I think you understate the problem. Robert Ayres has calculated that nationally, we recover only 2% of the energy we consume as useful work. (See http://www.iea.org/textbase/work/2004/eewp/Ayres-paper3.pdf for one, but far from the only example from a lifetime body of work).

This sounds striking, but consider: average US power generation efficiency is 33% and a typical lightbulb is 8% efficient. Thus we burned 26.4 units of fuel to make one unit of useful light. Other examples abound, and point out the vast potential for energy efficiency. Your schematic, which presumes that the facility is generating power onsite vastly helps this calculus by virtue of the fact that they're recovering waste heat and avoiding T&D losses, but that's the exception to the rule.

Otherwise, great stuff.

Sean Casten

At 9:26 PM, Blogger Christopher Russell said...


You are right about the volume of energy waste that accrues on BOTH sides of industry's (collective)facility fence. You refer to energy losses that are incurred in the generation, transmission, and distribution of electricity. Those losses are rolled into the electric industry's legitimate costs of doing business, and they inflate the costs-- not just of electricity-- but of all the goods whose manufacture requires electric power (that's just about everything, isn't it?)


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