GEK Wiki / 2x 10 hr Workshop Power Pallet Run
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2x 10 hr Workshop Power Pallet Run

Page history last edited by bk 12 years, 7 months ago


For our June 2010 workshop, we ran the Power Pallet for two consecutive 10 hour periods. We generally ran the Power Pallet at the low end of its potential output over these runs. Post-run tear down photos are posted in the forum gallery.



T_tred - temperature at top of reduction (constriction)

T_bred - temperature at bottom of reduction (below bell)

T_pyro_in - temperature of exhaust gas entering Pyrocoil

T_pyro_out - temperature of exhaust gas exiting Pyrocoil

T_gas_out - temperature of produced gas exiting drying bucket

T_lid - temperature of the lid on the Pyrocoil

P_reactor - pressure at reactor manometer tap

P_comb - pressure near combustion, taken through ignition port

P_filter - pressure at top of filter barrel

P ratio - ratio of P_comb/P_reactor to indicate reduction bell packing

Lambda - oxygen sensor reading (Lambda of 1 is a stoichometric mixture)

Auger - fuel switch state (in graphs below, red is auger switched on)


Energy Output

Power output from the genset was monitored via the GCU using circuitry described here.

Load on the Power Pallet consisted primarily of various resistive loads. Some of these loads had thermostats which caused the alternating power consumption (output) shown in the data logs.



x-axis in hours. Oscillation of real power output caused by thermostat cycling on heater dump loads.

Saturday Fuel Flow 

Fuel flow through the reactor was consistent with no bridging. Auger duty cycle over entire run cycle, including refill downtime, was 19%.


Duty cycle of the auger over the run. Generated with a 10-minute window running average. Slowed fuel consumption is evident at points when engine was turned off (indicated by a high lambda value)


Saturday Run Statistics

Softwood chips, -1" +1/4" mesh, estimated moisture content 10-15%
Datalog Duration
10.5 hrs
Generation Duration 9.1 hrs
Power Generated
33.1 kWh
Average Power Output While Generating
3.6 kW  
Auger Duty Cycle


Saturday Run Fuel Consumption

Rigorous measurement of fuel mass flow was not conducted during this run. However, estimates for fuel consumed over the run range from 63.1-78 kg. Yielding a power output per mass of fuel of 1.9-2.3 kg/kWh (wet). It should be noted this figure includes fuel consumption during refilling, and fuel consumed towards engine friction losses while running at low load (e.g. fuel consumption per kWh will go down with high power output). 


Saturday Run Gas Analysis Results

Means and 95% confidence range for measured gases (c), calculated density, and calculated heating value. 

H2 [%]
18.7 +/- 4  
CO [%]
22.7 +/- 4.3  
CO2 [%]
9.6 +/- 3.1  
CH4 [%]
3 +/- 1.8  
O2 [%] 1.3 +/- 0.5
Density (dry) [kg/m3] a 1.02 +/- 0.04



HHV (dry) [MJ/Nm3] b


6.6 +/- 0.7

177 +/- 19



a - Dry gas density (calculated based on measured gas percentages and remainder assumed to be nitrogen) at 20°C, 1 atm

b - Calculated using HHVs for CO, CH4, and H2 taken from Handbook of Biomass Downdraft Gasifier Engine Systems (T.B. Reed and A. Das)

c - Data collected with a gas analyzer provided by Tom Jopson. Means and values calculated from 827 data points (2.5 hours) where oxygen was less than 2.5% (to exclude data where air was in the sample line). Sampling started at ~5 hours 40 minutes into the run.




Sunday Run Statistics

 Walnut shells, wood chips  
Datalog Duration
10.6 hrs
Generation Duration 9.27 hrs
Power Generated
8 kWh
Average Power Output While Generating
865 W
Auger Duty Cycle (entire run)



Scatter plot of P_comb vs. real power. Data from Saturday run.


The time series plots show a reasonable correlation between P_comb and the power output of the genset. The pressure at P_comb is governed by the amount of incoming air that enters through the air lines/nozzles. At higher power, the genset requires more producer gas, and the gasifier draws in more air. P_reactor shows very poor correlation with power output, since much of the pressure drop is governed by packing of the reduction bell (which appears to be very high during this run). This suggests P_comb could provide a rough measure of incoming air flow.


Real Time Datalog Visualization

Data from the reactor was plotted in real time using Gnuplot on a Mac (how to configure gnuplot and datalogging: forum post)

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