Waste Heat Recovery: The Next Wave of Clean Tech
by Jason Gold

There is a growing clean energy technology geared towards the manufacturing mill, which has gained traction in the forest products industry: waste heat recovery.

Waste heat recovery integrates easily into existing mill infrastructures and employs a process called the organic Rankine cycle (ORC), which has been around since the 1960s. ORC units capture heat that is currently being released into the atmosphere from biomass, natural gas, or waste fired boilers and converts it into useable CO2-free electricity. While this technology has a small footprint (approximately the size of a tractor-trailer flatbed), it helps forest products companies maximize the efficiency of existing investments and resources (Figure 1.)

John Ryan, Region Energy Manager at Weyerhaeuser, describes waste heat recovery as "technology that is designed to produce clean energy, while reducing emissions and lowering a plant's electricity bill."

Weyerhaeuser is currently working with KGRA Energy on installing an 800kW system in its Greenville, NC lumber mill. In order to tap into Weyerhaeuser's wasted heat, an ORC system will be installed within the mill's biomass-based thermal drying system. Heat will then be recovered from the kiln, where cut lumber enters the drying process. Estimates have shown that the kiln will output enough waste heat to generate 4.5 million kWh of CO2-free electricity per year for the facility. And all of this comes from a technology that can fit on the back of a flatbed truck.

KGRA Energy is currently working on the development of a 10MW organic Rankine cycle (ORC) project at a newsprint and linerboard mill that will recover the facility's waste heat and convert it into useable CO2-free electricity. The installation is slated to break ground in Q1 of 2012.

AN UNLIMITED MARKET
The market for waste heat recovery is virtually limitless. According to researchers at University California Berkley, the U.S. currently consumes about 100 quadrillion BTUs of energy per year. However, between 55 and 60 quadrillion BTUs are currently vented into the atmosphere as waste heat. With ORC technology, these emissions are harnessed on-site to generate useable CO2-free electricity that is fed directly back into a manufacturing process. Forest products operations are especially well-suited for waste heat recovery systems since they use large amounts of electricity and maintain consistent waste heat streams with temperatures between 400° and 800°F.

ORC employs environmentally benign refrigerants in a closed loop system that turns waste heat into useable electricity. Given its relative simplicity, carbon neutrality and diminutive physical footprint, ORC is one of the most inexpensive sources of renewable power generation. Also, its high utilization rate (95%) far eclipses the 25% - 35% utilization rates seen in other renewable technologies, such as solar and wind.

Recycled Energy Development conducted an analysis of Department of Energy data, finding that waste heat energy was one of the cheapest energy sources per megawatt hour (Figure 2). Currently, the capital upfront cost of waste heat recovery technology is approximately $3 million for a 1MW project. But the relative cost continues to decrease as the project grows larger, making waste heat cheaper than any other current new energy generation.

A wave of new project development activity has occurred as a result of rising energy costs and growing environmental concern. Recent improvements in the ORC manufacturing process have made the systems modular, customizable, and easily deployed. Also, the rise of independent project managers has also hastened adoption; allowing mills to focus on energy savings while project managers design, engineer, construct and operate the plants.

Waste heat recovery delivers a win-win clean energy solution. By tapping into existing but unused energy sources, forest products companies reduce energy spending, reduce carbon footprints and reduce dependence on non-renewable sources of energy. And that's why waste heat is about to become a lot more relevant.

Jason Gold is the Chief Executive Officer of KGRA Energy, LP, a developer of electricity generation projects that harvest waste heat to create clean, renewable energy. Contact him at: info@kgraenergy.com.

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