Flue Gas Energy Recovery

The University of Idaho Steam plant switched to a biomass fired boiler in the 1980's which increased steam capacity and replace the existing coal and natural gas boilers. These boilers produce a large amount of waste flue gas heat that our team is tasked with recovering and using to produce electricity.

Background
The Steam Plant:
 * The University of Idaho Steam plant is full of hot surfaces that constantly put out heat. Our teams goal is to capture this waste heat by a device that utilizes Thermoelectric Generators (TEGs) to produce an output voltage via a Temperature difference.

What is a Thermoelectric Generator(TEG):

 * A device that utilizes heat flux to produce electricity
 * Constructed of n-type and p-type semiconductors formed into thermocouples
 * Common efficiency between 5% to 9%
 * For max efficiency ΔT must be around 518 F

How a TEG works:

 * Operate according to the Seebeck Effect.
 * Temperature difference across thermoelectric material can be converted directly into electrical power



Heat Transfer equations

 * Conduction: q=-k(ΔT/Δz)
 * k=thermal conductivity, T=temperature (°C or K), z=thickness


 * Free convection: q=hA(T_surf-T_ambient)
 * h=heat transfer coefficient, A=area, T=temperature


 * Radiation: q=σ*ξ*A*(((T_1)^4)-((T_2)^4))
 * σ=5.67e-8(W/(m^2 K^4)), ξ=emissivity (unitless), A=area, T=temperature(Kelvin)

Circuit Equations

 * OHMS Law: V = I*R
 * Power: P = V*I = (I^2)*(R) = (V^2)/R
 * V=voltage(Volts)
 * I=current(Amps)
 * R=resistance(Ohms)
 * P=power(Watts)

Design Goal

 * Be able to be applied to a wide variety of surfaces
 * Maximize efficiency of the TEG by increasing the ΔT
 * Minimize impact to existing structure or surface it is applied to
 * Operate with little annual maintenance
 * Apply to surfaces with a Temperature that is steady state
 * Design an optimal way to provide the Cold side for the TEG

Design Specifications

 * Desired TEG Wattage output (estimate): 40W
 * Temperature range (based on applied surface):
 * 1.Wood boiler exhaust: T_out=278°F to 285°F
 * 2.Wood boiler flash hopper: T_out=500°F
 * 3.Wood boiler outlet: T_out=280°F to 300°F
 * 4.Wood boiler bottom ash hopper=250°F to 350°F
 * Q necessary=500 to 800 Watts

Meeting Minutes

 * [[Media:Minutes 9-15-16.pdf| September 15th 2016 ]]
 * [[Media:Minutes 9-21-16.pdf| September 21th 2016 ]]
 * [[Media:Minutes 9-28-16.pdf| September 28th 2016 ]]
 * [[Media:Minutes 10-5-16.pdf| October 5th 2016 ]]
 * [[Media:Minutes 10-12-16.pdf| October 12st 2016 ]]
 * [[Media:Minutes 10-19-16.pdf| October 19th 2016 ]]
 * [[Media:Minutes 11-2-16.pdf| September 2nd 2016 ]]