Final Report: Inexpensive High Performance Continuous Ammonia MonitorEPA Contract Number: EPD16008
Title: Inexpensive High Performance Continuous Ammonia Monitor
Investigators: Pilgrim, Jeffrey S
Small Business: Vista Photonics, Inc.
EPA Contact: Richards, April
Project Period: February 1, 2016 through January 31, 2018 (Extended to January 31, 2019)
Project Amount: $300,000
RFA: Small Business Innovation Research (SBIR) - Phase II (2015) Recipients Lists
Research Category: Small Business Innovation Research (SBIR) , Air Quality and Air Toxics , SBIR - Air Monitoring and Remote Sensing
The purpose of this project was to develop an innovative inexpensive optical technology for highly sensitive , selective, rugged and portable continuous measurement of atmospheric ammonia for air pollution monitoring. The target characteristics of the proposed instrument include high selectivity to ammonia, low parts-per-billion (ppb) detection limits, fast response , good long term stability and reduced calibration requirements, robustness and portability. Estimated power draw of 25 Watts allows operating the sensor from a variety of readily available power sources. The instrument should be capable of remote data logging. In the proposed method, the ammonia concentration is measured optically using a combination of semiconductor laser technology (quantum cascade laser - QCL), wavelength modulation spectroscopy, and high-performance photoacoustic spectroscopy.
The developed prototype sensor weighs about four pounds, is smaller than a shoe box, and draws only 8 Watts. The lower power draw is attributable to the advent of a QCL product line from ThorLabs, which required much less power to control laser temperature. The ammonia sensor can resolve ammonia concentrations of 1-2 ppb with a tens of seconds response. The sensor only required a single calibration. Real time gas sampling is provided by an internal, low power, continuous flow pump. The very low power draw allows operation with camcorder batteries up to about 12 hours if line power is not available. The sensor streams data over a serial communications interface with a one second update rate. The sensor was tested in multiple applications. It was used as an indoor occupational safety monitor where background concentrations of tens of ppb were encountered. It was tested as an ammonia breath monitor where concentrations up to 600 ppb were determined. The sensor demonstrated capability to measure ammonia from both sweat and breath. Likewise, both sources of ammonia were encountered during background monitoring throughout a physical exercise event in a quasi-isolated volume where levels eventually exceeded 100 ppb. Outdoor background concentrations were measured in the tens of ppb over many days at a fixed geographical location. Finally, the portable sensor was transported to various locations in the area of a string of local dairies where background concentrations varied from 100 ppb upwind to 2500 ppb downwind.
The EPA ammonia sensor offers a compelling blend of physical and performance characteristics. It is small, lightweight, and doesn't draw much power. A few other sensors may offer better sensitivity but at significantly increased cost, size, and power. The Vista Photonics sensor does not require a sophisticated operator and has a simple display for concentration and a user friendly interface for the streamed data. Though lower than the cost of the highest performance competitor's offerings, the Vista Photonics cost remains too high, as in Phase I, for massive deployment due primarily to the laser. Laser costs need to come down by a factor of 4 to 5 for a viable offering to offset the somewhat reduced sensitivity.
The technologies developed for the EPA on this project positioned the company to offer several gas measurement solutions to difficult problems at both NASA and the US Navy. NASA has extended the basic technology into a requirement for a flight hardware development that will result in a contingency air monitor for both the Orion spacecraft and the International Space Station. The US Navy is testing prototypes for possible infusion into a fleet deployment in the emerging Columbia-class ballistic missile submarines.
These types of follow-on government contracts are best suited for the high-performance, high-value, multi-gas platforms being targeted by the company. The companyss strategic direction is in multiple species sensors for difficult measurement applications not addressable by simple off the shelf devices. There are still opportunities for single gas, QCL-based, sensor systems like the ammonia prototype once QCL pricing can be reduced by market volume and increased competition. As evidenced by this project there are new competitors coming into the QCL market with better products. The ThorLabs devices in the Phase II prototypes were markedly superior in performance and practicality to the Adtech device used in Phase I. Laser costs are still prohibitive to enable a massively deployed product but there are niche opportunities in breath monitoring and environmental monitoring at high value locations.