Adaptive Low Emission Microturbine for Renewable Fuels

This page last reviewed January 22, 2010

University of California at Irvine

Technology and Innovation
The technology is an Active Combustion Control System (ACCS) with a novel feedback sensor implemented on a microturbine generator (MTG). The ACCS uses a sensor, control logic, and variable geometry injectors to provide control of combustor fuel / air ratio independent of generator load. The first innovative feature of the proposed work is the extension of a concept previously demonstrated on a natural gas-fired system to alternative fuels (i.e., non-fossil fuels). This is an important step to enabling fuel flexibility while minimizing pollutant emissions. Previous work conducted at UC illustrated that CO emissions from and engine stability in a microturbine engine was strongly influenced by the fuel composition. A second major innovation is the application of a non-intrusive ion-based sensor for monitoring the combustion process inside the engine in real time to allow for closed loop control of combustor chemistry (i.e., NOx, CO, and combustor stability) as ambient conditions, load, and fuel composition vary.

Emission Benefit
The extent of emissions benefit will depend in part upon the availability of opportunity fuels. Readily available fuels include landfill gas and gases produced by anaerobic digestion (e.g., wastewater treatment or livestock waste management operations).

A specific benefit is estimated here for landfill gas in California that is currently vented or flared (~97MW worth of gas). In this case, the technology development can provide emissions reductions in two ways. First, by facilitating deployment of low emission, reliable engines, gases that would otherwise be vented or flared are used to generate electricity and offset the need for power generation from other sources. This would offset some 175,000 cubic feet per hour of methane containing gas, which has over 20 times the global warming potential that CO2 does. Second, by adapting the performance of the microturbine generator to minimize pollutant emissions regardless of ambient conditions, fuel composition, and engine load, emissions of CO will be reduced by a factor of 4 and NOx by 25 percent to 50 percent compared to a microturbine without this technology. This would translate into ~1,275 tons/yr CO savings. This is an example for just one alternative fuel market.

Co-firing natural gas with alternative fuels may also be of interest. In this case, the technology proposed can help to minimize emissions for any mixture of natural gas and alterative fuel without any modification to the engine or the fuel injectors.

Project Description
The project consists of three major tasks. The first task is associated with the refinement of the active combustion control system (ACCS) previously demonstra-ted in a modified MTG at the test facility at UC Irvine. The refinements include adopting Woodward ion-sensing technology to the variable geometry fuel injection developed by the UCICL in conjunction with Capstone Turbine Corporation. Once the refined injector concept has been designed and fabricated, it will be used in a microturbine generator at the UCICL and its emissions performance will be characterized along with the ion-sensor signal as a function of load and fuel composition. Next, this performance map will be used to develop the control logic which will then be integrated into the microturbine generator control system. The operation of the novel MTG will then be verified along with the ability of the ACCS to respond to fuel composition changes and minimize emissions.

The second task is associated with preparation of a site at a landfill where existing MTGs are operating. The novel MTG will be transferred to the landfill site and its performance monitored for six to seven months including comparison of emissions with and without the technology developed in the project.

The third task is the documentation of the project in a final report and the preparation of a commercialization status report that outlines the remaining steps to bring the demonstrated technology to a product.

Funding Source Funding Amount

ICAT $215,000
Grantee $136,975
3rd Parties $236,000