the difference in O2 partial pressures on the two sides of a zirconium or palladium wafer or oxide cell. An air-powered aspirator draws gas samples past sensors providing independent and continuous percent-by-volume measurement of O2 and in some cases CO. CO spectroscopic analyzers, which sample the entire gas stream by shining a beam of infrared light across the stack and averaging CO concentration across most of the stack and measuring it. A CO-sensitive filter and a non-CO-sensitive filter are set on a rotating wheel and pass alternately across the source to allow alternate measurement and reference infrared impulses. CO2 analyzers, which are commonly used for equipment of all sizes. In the smallest applications, a flue gas sample is pumped into a container with a fluid, such as pyrite, that expands in proportion to the amount of

2 present. Scaled to the exhaust gas temperature this measurement indicates combustion efficiency. Large boiler systems use systems such as non-dispersive-infrared photometers.

Flue-gas analyzers are either extractive or in-situ. These terms refer to the manner in which the gas sample is delivered to the analyzer. Extractive units draw a sample out the stack, condition, and then transport the sample for remote analysis. In-situ analyzers expose the sampling apparatus directly to the flue gas and measurement combines a light source shining across the stack with a receiver/analyzer. They use absorption spectroscopy and measure ultraviolet, visible, and infrared portions of the optical spectrum. Detection of the absorbed frequencies in the spectrum from a narrow-band source identifies the constituents and their concentrations.

Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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