The U.S. Environmental Protection Agency’s (EPA’s) plan to regulate carbon emissions is just the latest challenge facing the U.S. electric power system. Technological innovation is disrupting old ways of doing business and accelerating grid modernization. Earlier this year, AEE released Advanced Energy Technologies for Greenhouse Gas Reduction, a report detailing the use, application, and benefits of 40 specific advanced energy technologies and services. This post is one in a series drawn from the technology profiles within that report.
Waste Energy Recovery (WER) describes any process in which energy that would typically be “thrown away” is captured and put to use (for this reason, WER is sometimes also called recycled energy). In broad terms, there are three types of waste energy sources suitable for recovery and conversion to electricity: waste heat, excess pressure in steam and other industrial process streams that is normally dissipated, and residual fuel value in industrial process streams (purge gases, off-gases, etc.). WER can be used to generate electricity or to produce useful thermal energy for industrial processes. The amount and type of useful energy produced depends on the nature of the process.
Some specific examples of WER that generate electricity include waste heat recovery (WHR) from industrial processes and boilers, WHR from mainline natural gas pipeline compressor stations (used in organic Rankine cycle plants), pressure recovery from industrial steam use, pressure recovery from non-steam, high-pressure industrial processes, and pressure recovery from natural gas pipeline pressure-letdown stations. One example of WER in action is the Port Arthur Steam project in Texas, which produces high pressure steam from heat recovered from petroleum coke calcining kilns. Most of the steam is sold to a neighboring refinery, which displaces natural gas use at the refinery. The rest of the steam is used to produce 4-5 MW of electricity used at the calcining facility.
With the industrial sector accounting for approximately one third of all energy used in the United States, there is ample opportunity for WER to reduce energy usage. During industrial processes, 20% to 50% of the energy is ultimately lost to waste. WER can improve efficiency of industrial processes by as much as 10% to 50%, depending on the process, while generating electricity that can be used onsite. WER both increases efficiency and displaces the need for purchased fuels and electricity, thus resulting in avoided emissions.