The World's #1 Renewable Energy Network for News, Information, and Companies.

Capturing Waste Heat with Organic Rankine Cycle Systems

Waste heat and low-temperature geothermal are hot sources of renewable energy that get a boost from Organic Rankine Cycle (ORC) systems.

In Brisbane, Australia, a 240-kW ORC unit at a timber plant will soon harvest heat from an existing biomass burner and generate electricity to power kilns for drying lumber. Similar ORC systems are becoming killer add-ons for other heat-based renewable energy plants, including concentrating solar and utility-scale geothermal systems.

“People are realizing now that, if you throw away heat, you’re throwing away money,” said David Paul, international business development manager for Pratt & Whitney, which designed the system for the Gympie Timber Company in Australia.

Typical geothermal systems generate electricity when water-based steam at high temperatures powers turbines. An ORC system uses a different fluid, such as thermal oil or silicon-based oil, which powers turbines at lower temperatures than those required for steam. ORC power plants have been known to generate power from geothermal sources with temperatures as low as 73.3ºC (165ºF) in Alaska. Utility-scale geothermal plants with steam turbines typically require water temperatures in excess of 350ºF.

The ability to use lower temperature fluids make the ORC systems ideal for harvesting heat from industrial exhaust systems. They are typically configured with the following components:

  • Heat source – This can be a geothermal water well, exhaust from an industrial facility, or heat from a biomass furnace or concentrating solar power system.
  • Thermal oil – This intermediary component transfers heat from the source to the ORC unit.
  • Rankine cycle  – Oil from the thermal oil system warms oil in the ORC unit, creating temperatures high enough to power a turbine.

Pratt & Whitney is among the growing number of companies trying to introduce ORC en mass to the United States market. ORC systems have been generating heat and electricity with woody biomass sources for 20 years overseas. Europeans have embraced combined heat and power (CHP) ORC plants (such as the one in Australia) because they can operate with at to 85 percent efficiencies.

“When you look at the stacks on a nuclear plant or coal plant, they’re releasing all that excess heat into the atmosphere, so they’re only 20 to 30% efficient,” said Bob Larson, CEO of Pennsylvania-based 1st Renewable Energy Technologies. “An ORC captures that excess heat, making 85% efficiencies possible.”

Europe has 120 to 150 ORC CHP plants with capacities of multiple megawatts. Many use waste wood as biomass feed sources. Larson said environmental concerns, coupled with high fuel costs, jump-started Europe’s investments in ORC plants in the 1980s. His company has formed a partnership with Maxxtech AG, one of Europe’s leading ORC manufacturers, to target the American market, where cement plants and other industrial facilities have been capturing waste heat for years.

Paul said Pratt & Whitney has received a notable increase in inquiries about ORCs as waste heat has become a hot topic over the past year. The company, a division of United Technologies, recently sold a unit to the city of Albany, New York. Similar systems are also marketed by geothermal heavyweight Ormat Technologies Inc.

Challenges remain in expanding ORC use in the United States, especially when retrofitting at industrial plants. In many configurations, the ORC itself is only 50% of the total installation costs, which include heat transfer equipment and condensers to cool the systems.

“A lot of times there have to be incentives in place [to make the economics work],” Paul said.

Incentive programs have helped his company’s ORC business expand to in India, Thailand and Indonesia.

Pratt & Whitney spokesman Bryan Kidder said its systems run $1,000 to $2,000 per kW. Larson said his CHP ORC systems can cost $925 kW compared to $5,000 to $7,000 per kW for other forms of renewable energy.

Larson envisions a time when Americans might install relatively small (2 to 5 MW) distributed ORC plants that provide heat and power to regional districts while operating independently of large transmission lines.  He believes smaller, distributed plants are more efficient and could take advantage of ORC technology more sustainably.

“There’s talk about 50 MW biomass plants in the U.S., but you kind of shoot yourself in the foot if you need to truck in biomass from 100 miles out just to fuel [the plant],” he said. “Smaller plants allow for more sustainable forestry.”


UK Parliament Clean Energy Leaders

UK Government Names Clean Energy Cabinet Members

David Appleyard, Contributing Editor With the UK general election now over and a majority Conservative Party government in place, the re-elected Prime Minister David Cameron has now named key members of the government charged with steering the UK’s clean energ...

Coast to Coast and Across the Electric System, Microgrids Provide Benefits to All

Dick Munson, Environmental Defense Fund At the most obvious level, microgrids could disrupt today’s utilities and their regulated-monopoly business model, because they challenge the centralized paradigm. In a nutshell, microgrids are localized power grids that ha...
Alaska Airlines Biofuel

Alaska Airlines, Gevo To Demonstrate Renewable Alcohol-to-Jet Fuel

Jim Lane, Biofuels Digest

In Colorado, Gevo and Alaska Airlines announced a strategic alliance to purchase Gevo’s renewable jet fuel and fly the first-ever commercial flight on alcohol-to-jet fuel (ATJ).

Germany wind turbines. Credit: Shutterstock.

Germany's Powerhouse Feels Pinch of Merkel’s Shift to Renewables

Tino Andresen, Bloomberg North Rhine-Westphalia, the German state that’s home to utilities RWE AG and EON SE, is losing its standing as the country’s powerhouse as wind and solar energy begin to displace conventional sources. Electricity consumers ...
Robert Crowe is a technical writer and reporter based in San Antonio, Texas. He has written for Bloomberg, the Houston Chronicle, Boston Herald,, San Antonio Express-News, Dallas Business Journal, and other publications. He ...


Volume 18, Issue 3


To register for our free
e-Newsletters, subscribe today:


Tweet the Editors! @megcichon @jennrunyon



Using Grid data analytics to protect revenue, reduce network losses...

Schneider Electric and Awesense have combined expertise to develop integ...

National Geothermal Summit 2015

The Geothermal Energy Association (GEA) is pleased to be holding its fif...

Energy Storage USA 2015

Energy Storage USA is the leading conference in the United States focuse...


Helping Small Businesses Visualize Savings

    What does a small business owner care about? Most are run...

Get Into Your Prospect's Shoes

    It may sound simple, but one of the best strategies for d...

The Question Trilogy

    It’s crucial to learn what your prospect needs from...


Renewable Energy: Subscribe Now

Solar Energy: Subscribe Now

Wind Energy: Subscribe Now

Geothermal Energy: Subscribe Now

Bioenergy: Subscribe Now