Return to Lopez Labs Home Page

2018 Next Generation Woodstove Design Challenge

on The National Mall, Washington, D.C.

November 9 - 13, 2018




Photo credit: Jim Schalles


The MHA Tech Committee organized a 5 person testing team to send to the event.
We brought 3 complete Condar PM sampling systems, and conducted a total of 15 three hour test runs over the course of  5 days. We were tasked with combustion testing of the thermoelectric stoves. Brookhaven National Laboratory had responsibility for testing the automated stoves, with funding help from NYSERDA.


Tesla S being charged by a MES pellet boiler with a 5kW electric output.





Maine Energy Systems AutoPellet boiler with optional Stirling engine generator add-on was a highlight. They were there by special invitation as a demo, since boilers were not elible for the competition..
They have a unique achievement in having brought CHP (combined heat and power) down to a near-domestic scale on a semi-commercial level. The unit is expensive at the moment, but they are commercially available in Europe and have logged many hours on them at client sites. This is the first time I have seen this combination of user friendly, real world proofed, and domestic scale electric power output from pellets.




Stack gas analysis graph.
Low stack temperature (250 F), very low oxygen (O2, blue line) and low carbon monoxide (CO) means high efficiency.


Wittus automated downdrafting cordwood prototype stove is optimized for electricity production by using water cooling  of the TEG (thermoelectric) cells. It also has a catalyst in the lower chamber.


View from the rear. On each side is a large bank of water radiators.


Startup sequence. Smoke is visible at 11:20 am at startup. By 11:23, no smoke is visible.  Shortly afterwards only steam is coming out of the stack, as evidenced by the lack of the plume that is visible on startup.


Segments of the burn had the lowest CO I have ever seen (it actually got to 0 for a few seconds).
Low stack temperature, low excess air (O2), super high efficiency. Producing 218 watts of TEG (thermoelectric) power (rear screen).


Stack gas graph. We lost data from minutes 40 to 65. We interpolated the lost data, as shown by the flat lines.
The 3 reloads are clearly visible as big dips in the blue oxygen line.
This was a trial of a shortened version of the new Integrated Duty Cycle (IDC) testing protocol under development by NESCAUM to better simulate real world use in cordwood testing.
Therefore, the particulate numbers are not directly comparable with EPA laboratory certification numbers, which one might expect to be lower.


PM and CO are were the same range as we have measured on masonry heaters with the Austrian eco-labelled firebox.



We spent several months developing and testing this automated controller for our Condar portable dilution tunnel PM emissions sampler. It lessened the work load on our crews to a much easier oversight function for the equipment, rather than  manually having to adjust the flow control for the sampler over each 3 hour test period.


Testing the 3 new controllers at the MHA Lab in Shawville, Quebec, prior to the event.


Arriving at the tent on The National Mall. Equipment travelled from sites in Quebec, Massachusetts, Minnesota, and Maryland. "Some assembly required"
Photo credit: Kittner for Brookhaven National Lab


Assembling a Tulikivi demonstration heater, that was used to keep the overnight security crews warm during some chilly weather. It travelled from the Tulikivi US distribution distribution warehouse in Charlottesville, VA.


Testing team from Brookhaven National Laboratory setting up their equipment.


Open to the public and testing in full swing.
Check out this great article about the public's impressions at the event.
Photo credit: Kittner for Brookhaven National Lab




Mark Seymour and Ron Pihl setting up our equipment on the Kd3 downdrafting thermoelectric stove.


Location of the 3 holes drilled into the stack for:
- Condar portable PM sampler
- stack pressure reference port
- Testo 330-2 flue gas sampling probe


It has a very innovative hot side heat exchanger scheme for the TEG's. After the downdrafting flame finishes combustion and turns the corner, a thick copper fin that is directly in the gas path is joined to an aluminum plate that is out of the gas path. 


Setting up a demonstation test on the Swiss OekoSolve electrostatic precipitator.






Demonstration of 30,000 Volt plasma cloud arcing over to a piece of firewood.


Daniel Jud from Oekosolve checks the Testo readings
Photo credit: Kittner for Brookhaven National Lab


We ran 2 Condar samplers, switching them on and off at 6 minute intervals, in synch with the precipitator. The old technology stove was quite dirty, as shown by the yellow strong smelling organics on both filters. The PM reduction on the precipitator "on"  filter on the right was around 50%.
Test Report


NY State Dept. of Health brought along a real-time nano particle counter. It has a cutoff at 1 micron (1/1000 of a millimeter), and counts down to the nanometer range. It showed a reduction in the 80% range of nano particles when the precipitator was turned on.


Mark Seymour and Jim Schalles prep the chimney on a stove with the VcV (Venturi-Controlled Valve) from New Zealand. It provides automated primary and secondary air control, without electronics or power requirements.


A thin metal disc slides on a rod. Gravity holds the air supply open. As the stove warms up and draft builds up, the disc is pulled up the rod by air pressure, and finds a balance point. There is a separate valve on the primary and secondary air supplies.


Aprovecho Integrated Stove




A 14' hose connects the Condar to a Kenmore vacuum sitting outside the tent. The Kenmore is controlled by MHA's new automated Condar controller.


Ben Myren did the fueling on the TE (thermolelectric) stoves. Here he starts up the prototype rocket stove from Aprovecho. It is designed for a specific application in China, and has air cooled TEG modules with a large cooling fin area. It also features an OekoSolve electrostatic precipitator on the exhaust.


A bit of help was needed from the blue alcohol gel in the cup next to Ben.








Stack gas analysis graph automatically generated by the Testo EasyHeat data logging software.



Normalized graph in MHA standard format, for comparison purposes with other tests.
Note the blue O2 line is very close to 20%, indicating very high excess air on this run.


Condar spreadsheet summary. Compare with Run 2, below.



Normalized graph for run #2. The first hour of data was lost due to a computer glitch.



Condar summary.
The electrostatic precipitator was not functioning in Run 1.  
Run 2 had the precipitator operating and has lower PM.
Run 1 had high excess air and high CO, so was a different type of burn. 


SBI entered a prototype fireplace stove that was completely automated, based on 2 simple sensors - flue temperature and door open/closed. A sophisticated logic board regulates 2 air control motors to keep the stack temperature constant and boost the fire on a cold start. Their stove also had the best fire viewing of all the stoves in the event.


Automated stoves judge Mark Knaebe lights the SBI fireplace stove for a testing run.
Mark is a United States Forest Service scientist at the Forest Products Research Laboratory in Madison, Wisconsin.


We tested the stove simultaneously with Brookhaven for 1 run. However, on the Saturday morning it was super windy. The Condar controller depends on measuring chimney pressure accurately, and this was virtually impossible  due to large fluctuations. The PM number was 2X the BNL (Brookhaven) number. On two other runs with calmer weather, on the Wittus  and the VcV stoves, we had good agreement.


Thermoelectric expert Fred Leavitt of Vulcan Energy used commercially available TEGs by Hi-Z, and adapted the gravity feed Wiseway pellet stove to get an output up to 130 watts. He won second place in the thermoelectric category.





Tulikivi's North American head Boris Kukolj discusses masonry heaters and the NSPS with EPA's Rochelle Boyd.


Jonathan Male, head of U.S. Department of Energy's (DOE) Bioenergy Technologies Office, and a lead sponsor of the Challenge, addressing the teams. DOE was very pleased with the event. Alliance for Green Heat was able to engage them to now include residential biomass heating in their programmatic work.
Biomass is the second largest source of renewable energy in the United States, ahead of solar and wind. 
Domestic heating accounts for 25% of biomass use


Rebecca Trojanowski from Brookhaven National Laboratory presented the First Place award in both categories (automated and thermoelectric) to the Wittus team, from Denmark and Germany.


I had the pleasure of presenting the Innovation Award at the closing ceremonies. It went to Stove Builders International (SBI) a major Canadian Company based in Quebec. They showed a prototype fireplace stove that was completely automated, based on 2 simple sensors - flue temperature and door open/closed. A sophisticated logic board regulates 2 air control motors to keep the stack temperature constant and boost the fire on a cold start. Their stove also had the best fire viewing of all the stoves in the event. It also won 2nd place overall in the automated category.


The "People's Choice" Award went to the 509Fab stove. It features self feeding pressed logs, and has high efficiency and very low PM and CO, see Condar summary below:


MHA Testing Team enjoying some stored heat.
Left to right: Ron Pihl, Jim Schalles, Norbert Senf, Mark Seymour, Boris Kukolj.




This page was updated on December 12, 2018
This page was created on  November 18, 2018