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

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

Voltage Regulation


Overview:

The Tegulator TGPR-CON-SYS-2 Diversion Charge Controller is an inexpensive solution for regulating the charge for your lead acid battery while providing a voltage and current display to determine charge rate.



Specifications:

The TE-BC-VA-12V features a boost/buck regulator that limits the voltage to 14.4 V DC to charge lead acid batteries. The diversion circuit will turn on and operate at 10 V DC. The controller can handle inputs as high 30 V DC. It also has reverse polarity protection to prevent your battery from discharging back into the thermoelectric generator.

Charging will begin once the diversion circuits input reaches 10 VDC. The max voltage the diversion circuit can handle is 30 VDC. You can run DC devices directly off the output, however if the load is in excess of what the TEG is generating it will automatically disconnect the load.

The Diversion Charge Controller displays voltage, current, power and watts hours logged. Simply hit the reset button on the screen to reset the watt hours logged. (Info from tegmart.com)

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)

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 ]]