The ESR/FF Instrument is another example of a Directed Development project. A rudimentary version of the Input/Loss Method required high accuracy measurements of combustion effluents. Although the current Input/Loss Method corrects effluent measurements using a discovered fuel parameter and statistical methods (a non-direct method, see the Part IV paper), in the 1980s direct measurements were required with laboratory-grade accuracy. No such instrument was available, and certainly not available for a power plant environment such as found at the Mohave Generating Station, site of much of the early effort. The conditions at Mohave were indeed severe: summer-time temperatures could easily exceed 122^oF (50^oC), with flue gas opacity greater than 25% through a 30 foot (9 meter) duct. Note that the US Environmental Protection Agency has never require absolute accuracy of power plant pollutants, only relative. Faced with such difficulties, and believing in the importance of Input/Loss to the coal-fired industry, Exergetic Systems developed its own cross-stack instrument, the ESR/FF.

The ESR/FF Instrument was in-situ, consisting of a Detector Instrument and a Source Instrument mounted on opposite sides of the flue duct. ESR/FF measured with great accuracy (less than ±0.1% absolute resolution) the concentrations of CO₂ and H₂O. Additionally, the concentrations of CO, SO₂, SO₃, NO and NO₂ were also detected, as was opacity. The first functionality of ESR/FF was its ability to satisfy all EPA effluent requirements. Its second functionality was to support the, then current, Input/Loss Method.

The Source Instrument housed an infrared (IR) source, its optics and electronics. The IR source was a 1700^o Kelvin graphite lamp used to deliver adequate flux to the Detector Instrument given a highly sooted medium. The IR beam was optically interrupted using a 2250 rpm shutter. Both Source and Detector units were pressurized with ultra clean, dry air for the purpose of eliminating moisture and contaminants from the instrument cavities. A valve body provided interface between a flange and the instruments. The valve body contained a sapphire window kept clean using a continuous air cone within which a secondary stream of ionized air prevented static buildup from holding dirt particles. The unit?s temperatures were controlled using thermoelectric coolers.

The Detector Instrument employed a lead-selenide detector, sensitive to radiation between 1000 to 6000 nanometers and operating at -30^oC using a 3-stage Peltier Cooler with a metering thermistor and pre-amplifier. Such cooling was required to achieve maximum sensitivity and to guard against detection of ambient temperature affects. Calibration assured that the source lamp?s blackbody characteristics were preserved. All Detector unit optics were gold coated. To achieve spectral absorption, the IR signal was passed through a dispersive Continuous Variable Optical filter. The detector signal was routed through coaxial cable and specially shielded circuit traces to a D/A Converter, and then to a conditioned cabinet housing the Data Acquisition Interface (motherboard) and Instrument Computer.

Directed Development leading to the ESR/FF resulted in installing eight systems, the issuing of US Patents 5306209 and 5327356, and publishing critically reviewed papers in Applied Optics (vol.35, no.3, pp.351-363) and in Applied Spectroscopy (vol.47, no.4, pp.479-488). In 1995 the then owner of Exergetic Systems, a subsidiary of San Diego Gas & Electric, was failing, cutting support. Although since 1995 Exergetic Systems has been an employee-owned company, the spirit which created ESR/FF continues.

 

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