It pays to employ an ORC

GE Energy and energy developer ECOS Ltd have announced that they plan to demonstrate an innovative, industrial waste-heat recovery system that can dramatically increase the efficiency and output of biogas power plants. The two companies signed the agreement during a celebration in July of the fifth anniversary of GE’s European Global Research facility in Munich, which concentrates on industrial energy efficiency research.

The demo plant is a 7.2 MW biogas facility in the eastern Slovenia town of Lendava. It will incorporate GE’s new pilot organic Rankine cycle (ORC) waste-heat recovery system for gas engines, which is designed to make on-site power plants that use natural gas, landfill gas or other waste gases more cost-attractive to build. The impetus for it comes from the increasing number of installations of cogeneration plant and renewable energy capacity intended to enhance energy security and lower regional emissions.

The ORC system allows the operator to usefully capture more of the waste heat created by the biogas plant. In the case of Bioplinarna Lendava the increased thermal output will help generate another 300 kW of power.

‘Our goal is to demonstrate that dramatic improvements in energy efficiency and output can be achieved in gas engine power plants through enhanced waste-heat recovery,’ said ECOS director and owner Jože Pavlinjek.

The pilot ORC system will be installed on one of the three GE Jenbacher J420 gas engines (photo) that have powered ECOS’ Bioplinarna Lendava plant since June 2008 and is expected to boost the unit’s electrical efficiency by five percentage points.

Organic Rankine cycle

Landfill gas and other renewable biogas projects are among the prime candidates for ORC systems, especially in countries that offer high electricity feed-in tariffs.

An ORC offers enhanced energy efficiency by utilising as a working medium an organic, high molecular mass fluid that has a lower boiling temperature than water, allowing heat recovery from lower temperature sources such as waste heat. Ultimately this heart can create steam for electricity generation, but owing to technical waste-heat recovery constraints, there have been few gas engine-based ORC applications.

This ORC technology allows, for the first time, all the waste heat from an engine’s exhaust gas and cooling cycle to be fully captured and utilised. It was developed by GE’s Munich corporate research centre and GE Energy’s Jenbacher gas engine business in Austria.

In May 2009, GE unveiled its ORegen Waste Heat Recovery System, developed with GE Oil Gas, which does a similar job in tandem with a gas turbine. When coupled with a simple-cycle gas turbine, the ORegen system generates electricity from its waste heat while consuming no additional fuel or water.