Robust, Low-Cost, Real-Time, NOx Sensor for Optimization of Dispatchable Distributed Generation Systems

Evaluating advanced, low cost solid state sensors for monitoring NOx emissions from distributed generation

The Regents of the University of California, Irvine


Irvine, CA

Recipient Location


Senate District


Assembly District



Amount Spent



Project Status

Project Result

The project is completed. The results show that the two automotive solid state NOx sensors selected proved durable enough to perform reliably for the 6-month evaluation. The research team developed an engine control system integrated with information from the solid state NOx sensor and successfully demonstrated the ability to actively reduce NOx emissions at part load by 10%. The results show that solid state sensors represent an inexpensive and viable approach for monitoring emissions from distributed gas generation systems. This technology could potentially be implemented in California Air Resource Board's certification process for small distributed gas generators as an alternative to the existing Continuous Emission Monitoring System.

The Issue

Low emission distributed generation technologies, such as microturbines and reciprocating engines, can improve onsite resiliency and provide supplemental supply for peak demand. Deploying clean, efficient, distributed generation systems directly addresses goals stated in AB 32, SB 350, and the Clean Energy Jobs Plan. While reducing greenhouse gases and improving efficiency are vital, maintaining strict air emission standards is also important. Distributed generation systems often suffer performance degradation over time once deployed. This may lead to increased emissions of air pollutants, such as NOx. As a result, there is a need for a low cost approach to monitor emissions performance.

Project Innovation

The project tested several recently developed sensors with the capability to detect low NOx levels generated by dispatchable generation systems, such as internal combustion engines and microturbines. The proposed solution offers a cost effective means to monitor the real time emissions of the system and information that can be used to optimize system performance and maintain low emissions.

Project Benefits

The NOx sensor is based on ceramic solid-state electrochemical sensor technology, similar to an automotive oxygen sensor. Solid state NOx sensors have been developed for direct in-situ measurement of exhaust to meet stringent on-board diagnostic requirements for self-diagnosis and reporting, including required sensitivities down to parts-per-million. The NOx sensor combines existing commercial NOx sensors with newly developed electronics for use in applications such as dispatchable distributed generation (e.g., microturbines). Unlike other NOx sensors, the sensor is a simple solid state device, with a single cell and no internal diffusion chambers (electrodes directly in the flow). This gives it faster responsiveness, and makes it both more robust and easier to manufacture.

Lower Costs


The cost to add the sensor system to a given engine is estimated to be about $2,000, well below a typical current monitoring system priced above $10,000. The cost should come down further as the number of units increases.

Environmental & Public Health

Environmental Sustainability

For the estimated current 50 MW fleet of microturbine generators in California, a 10% reduction in NOx for each distributed generation device operating at partial capacity will would reduce NOx emission by 30 tons each year. Beca

Key Project Members

Project Member

Vince McDonell

Associate Director

Contact the Team