The United States’ industrial sector, which includes both manufacturing and agriculture, consumes about a third of the nation’s end-use energy – more than any other sector in the country. The total for the sector has declined since its peak in the mid 1990s, reflecting the increasing prevalence of energy management and efficiency strategies. Yet many industrial facilities are still letting useful energy fly right out the window, sometimes literally.
In nearly every facility we visit, we find leaks in compressed air systems, oversized or inefficient equipment drawing too much power, and wasted heat energy going out exhaust vents and up stacks.
That last finding can be particularly significant for companies looking to reduce energy use, because waste heat is a very versatile resource. Recapturing heat for reuse, a process generally called thermal energy recovery or heat energy recovery, is becoming an essential part of an effective energy management strategy. And industrial facilities have a wide range of possible uses for recovered thermal energy.
Recovered heat can be used for a variety of industrial processes including preheating boiler feedwater and combustion air, power or steam generation, space heating, and process water preheating. Recycling energy already present in facility systems is emission-free and less costly than replacing equipment or system components.
“Free” energy can mean big savings
According to the U.S. Department of Energy, facilities employing a waste heat recovery system can reduce their energy consumption anywhere from 5% to 30%. This idea has been borne out over and over again in our experience. We worked with a client to install a condensing economizer, a type of heat exchanger that recaptures more energy than a conventional exchanger, to take what had been lost heat and transfer the energy to the facility’s boiler feedwater tank, hot water storage tank, and other process units. The recovered heat replaces supplemental power, saving tens of thousands of dollars and reducing carbon emissions by more than 500 tons.
In another case, a water bottling plant was spending approximately $250,000 a year to pre-heat the water it was bottling in order to prevent condensation on the filled bottles from causing quality issues and weakening corrugated shipping packaging. Woodard & Curran found that the heat generated by the facility’s air compressors and process chillers was more than sufficient to preheat the incoming spring water.
The system saves the client millions of BTUs, giving the project a simple payback period of less than four years. In the first year of operations, the plant’s natural gas usage went down 39% despite a production increase of 8%.
For a sector that consumes more energy than any other, thermal recovery is saving facilities money and giving new life to the old environmental adage: reduce, reuse, and recycle.