This column features helpful information, innovative equipment, systems and applications utilities around the nation can use to save energy and improve service.

With rising natural gas prices, industrial and large commercial facility managers and engineers are paying closer attention to the cost of generating steam. However, there can be confusion due to different understandings of what “the cost of steam" means. Here are some different ways to look at the cost of steam production:

• Total cost includes the combined cost of fuel, operating personnel, maintenance, water treatment, insurance, equipment replacement and payments on powerplant debt service.
• Effective cost is the cost of steam delivered to a process. This increases the total cost of steam by considering losses between the powerhouse and the point of use.
• Fuel-related cost considers fuel purchases divided by the quantity of steam produced.
• Fuel cost (in $/1,000 lbs. of steam) is dependent upon fuel type and composition, unit fuel cost, boiler efficiency, feedwater temperature and steam pressure. This value can be particularly useful in tracking the efficiency of a steam system.

One fuel cost example

Steam Tables , published by the American Society of Mechanical Engineers, indicates that producing one pound of 150 psig saturated steam requires 1,078 Btus using 150 ° F feedwater. Under these conditions, with a natural gas price of $8 per MMBtu (million Btu) and a boiler efficiency of 80 percent, the fuel cost of steam production is:

$8/MMBtu x 1 MMBtu/1,000,000 Btu x 1,078 Btu/lb. x 1,000 lbs x 100/80

= $10.78/1,000 lbs.

Heat requirements for other conditions can be about 10 percent higher or lower, as shown on the DOE Tip Sheet, Benchmark the Fuel Cost of Steam Generation (pdf).

Improvements become cost-effective

The bad news is that the fuel-cost component of producing steam has dramatically increased. The good news is that many improvements that can be made to steam systems are now cost-effective. For example, a DOE energy assessment in 2002 at an Illinois manufacturing plant recommended a $70,000 boiler replacement that would have had a payback of 5.4 years. The Alliance to Save Energy now reports that the project would have a payback of only 3.7 years.

Resources for improving steam systems

DOE’s Industrial Technologies Program has an extensive collection of technical resources available to help facilities improve their industrial energy system efficiency. Fact sheets, tip sheets, optimization software, case studies, workshops and more are available at no cost through the ITP website.

In response to rising natural gas prices, ITP recently launched Save Energy Now to help manufacturers cut their energy bills, particularly through steam and process heating system efficiency improvements.

Call the Power Line at 800-769-3756 for further technical assistance or submit your questions on-line. Western's Energy Services also offers many other resources on steam system efficiency.