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Lessons in building a 120-Watt thermoelectric wood stove

Posted by Earth Stove on August 31, 2017 with No Commentsas , , , , ,

Guest Blog: We are reposting a 2012 blog from Instructables by Tecwyn Twmffatt at Goat Industries. It describes an early effort to build a thermoelectric wood stove.  This blog is part of a series of blogs providing information for the 2018 Wood Stove Design Challenge.

Introduction: Thermoelectric Power Generation (TEG) 

These videos document my first attempts at generating electricity from a thermoelectric peltier device in 2012. The TEG that I used is a high powered unit able to withstand high temperatures and specially made for electricity generation. In terms of instructions, I don't think many people would want to build the 10 TEG system as it was ridiculously expensive, so I'm putting in a section for creating the 1 TEG arrangement, which is relatively easy and low cost.

Step 1: Part 2 of 3 

 


A ten unit Thermoelectric generator system is shown being constructed and then fitted to a wood burner. The theoretical maximum output is 200 watts. The video shows how the generator was put together and how the wood burner was modified to get maximum heat through the TEGs. The TEGs themselves are able to withstand a constant 325 degrees C on the hot side and require plenty of heat to get the 20 watts that each of them are capable of producing.

Step 2: Part 3 of 3 

 


In part 3 we successfully generate a significant amount of energy from the woodburning stove. In the first session, a circulation pump, a fan and 10 x 10 watt flood lights are powered up. In the second session, we attempt to get a more balanced load wired up to the tegs and measure a noticable increase in power output. The 10 tegs are wired up in 2 parallel strings and, from the manufacturer's specification, the optimum output voltage is 14.4v . The nearest that we manage is 13.8v, at which we generate 120 watts. The specifications suggest that 200 watts is possible when the load is matched.

Step 3: Full Playlist


31 Minutes of Thermoelectric video heaven!

Step 4: Creating the 1 TEG Generator


Here we are going to build the single TEG generator shown in the first video.

Step 5: Tools and Equipment  


Parts: 
Thermoelectric power generator TEG module (GM250 449 )
...... buy direct from China at: www.thermonamic.com/
Aluminium block 102 x 115 x 20 mm
Steel block 102 x 115 x 10 mm
1/4" BSP blanks x 6 of
1/4" BSP male stud push fit pneumatic fittings for 10 mm pipe x 2 of (See photo above)
5 mm Hex bolts x 40 mm x 2 of
25 litre water butt
OD 10 mm ID 8 mm nylon pneumatic pipe
12V water pump
12V LEDs, 1 watt x 20 of Tools:  1/4" threading tap
5 mm metric coarse threading tap
Drill 11.5 mm
Drill 5.5 mm
Drill 4.2 mm
Drill press
Torque wrench
MIG welder
Plasma cutter / Grinder with cutting discs
GM250-449-10-12.pdf

Step 6: Drilling and Tapping the Cooling Block


Use the engineering drawing to produce internal coolant passage ways in the aluminium block. I ended up drilling all the way through to the other side and using more of the 1/4" blanks. Connect the 1/4" pipe fittings to the block and plumb in the pump. Add antifreeze to the water in the water butt if it's likely to get cold at all. To create a 'sandwich' with the hot block (steel block), the TEG and the cooling block, drill and tap holes in the steel block for the 5mm bolts. Weld the hot block into the side of the wood burner and recreate the TEG sandwich, tightening the bolts up with a torque wrench (see attached file). Connect up LEDs on the TEG, turn on the pump, light the wood burner and off you go!
TEGinstallationandspecifications01.pdf

Step 7: 10 TEG Layout



If you really must build the 10 TEG generator, the photo above shows what is involved. I have got CAD drawings, PCB drawings etc. If anybody is interested. Not for the faint hearted! PCB 03.pcb
PCB 01.zip
CAD files 02.zip Heated Up!

Adventures in masonry stove testing from 1988 to 2017

Posted by Earth Stove on August 26, 2017 with No Commentsas , , , , , ,
by Norbert Senf, 
Chair of the Masonry Heater Association Technical Committee

Left to right: Mark Champion (in his 
VT test lab), Boris Kukolj (Tulikivi), 
Chris Prior (MHA President), Norbert 
Senf (blog author)  and Jean Francois 
Vachon (soapstone supplier). 
Photo credit: Mark Seymour.

EPA started regulating wood burning stoves for particulate (PM) emissions in 1988. Regulation was limited to airtight heating stoves. Masonry heaters were not regulated, the stated reason being that they were likely to be clean burning.

In Europe, only carbon monoxide (CO) emissions were regulated. CO is easy to measure, however PM can be very tricky. Wood smoke includes  compounds that will only be captured by a filter if you cool them down and condense them. This is done in the laboratory by mixing them with air in a dilution tunnel, and this is thought to simulate what happens in the ambient air in the real world.
State and county air quality authorities soon started to address wood smoke, and would often pass a generic local regulation that banned all appliances except those that were EPA certified. We, the fledgling Masonry Heater Association (MHA), decided to seek EPA certification.
Although we “knew” that masonry heaters were cleaner even than EPA stoves, nobody had ever measured the PM on one with the dilution tunnel method. With funding help from the Wood Heating Alliance (now HPBA), we were able to participate in a $ 100,000.00 test method development project for masonry fireplaces and masonry heaters. The project took place at Virginia Polytechnic Institute (VPI) in 1989 and was headed by Dr. Dennis Jaasma.
The results were interesting, with some surprises. EPA did not accept the proposed test method. We immediately realized that we needed do a lot more testing,  and that we would need to develop the capability to do it ourselves.
We were fortunate in being able to arrange for training with OMNI-Test, one of the leading EPA-accredited certification testing laboratories, then and now. OMNI developed a training session for us that took place in September 1996. It included presentations by regulators, an emission chemistry expert (Dr. Jim Houck),  and laboratory testing personnel. Dr. Stockton (Skip) Barnett showed us the low cost portable dilution tunnel that he invented, known as the Condar. He developed it while working for the Condar Company. It was widely used at the time by the major stove manufacturers for in-house testing to develop their certified  stoves.

The attached Powerpoint, Repeatability of Cordwood Combustion Particulate Measurements,  presents a summary of the work we have done at the Masonry Heater Association to calibrate the Condar against the EPA Method 5G laboratory dilution tunnel. It includes a close look at the PM testing repeatability issues,  a major discussion point over the years. We have recently completed 2 cordwood studies, using very carefully matched loads in a masonry heater. Repeatability was within plus or minus 15% – 25%, depending on the ignition method. With crib fueling, we were able to get within 10% repeatability on PM, and within 1.5% repeatability on CO.

Heated Up!

Opinions of top wood stove industry insiders revealed in 1998 interviews

Posted by Earth Stove on August 5, 2017 with No Commentsas , , , , , , ,

The late Paul Tiegs, one of thegreatest authorities on wood stoves, conducted the interviews for the EPA.  Long before the regulatory debate about wood stoves heated up in the 2010s, the EPA commissioned a series of fascinating interviews with the top wood stove experts in the country on a host of technical and policy issues.  […]

Vacuum left after one of nation’s top stove regulators and experts retires

Posted by Earth Stove on July 20, 2017 with No Commentsas , , , , , , ,

When Rod Tinnemore was invited to speak about wood stoves, he didn’t sound like a regulator.  He spoke his mind, he made people laugh and he was never at a loss for words.  Rod was in charge of wood heater regulations in Washington State, the state with the toughest regulations in the country.  By the […]

New York adds efficiency requirement to pellet stove incentive program

Posted by Earth Stove on July 14, 2017 with No Commentsas , , , , , , ,

This month, New York became the first state in the country to set a minimum efficiency requirement in an ongoing pellet stove incentive program.  The State will now only provide its $ 1,500 – $ 2,000 rebates to pellet stoves that are listed as 70% efficiency (HHV) or higher on the EPA’s list of certified […]

Could a Thermoelectric Wood Stove Pay for Itself?

Posted by Earth Stove on July 13, 2017 with No Commentsas , , , ,

By Ken Adler, AGH Senior Technical Advisor Payback calculations are common in the residential solar photovoltaic industry where homeowners want to know how long it will take for them to recoup their initial investment. If you purchase panels outright, payback periods depend on a variety of factors including a utility’s price for electricity, tax incentives, […]

Are we ready for the 100% renewable energy movement?

Posted by Earth Stove on July 11, 2017 with No Commentsas , , , ,

by John Ackerly, President of the Alliance for Green Heatreprinted from Biomass Magazine Many in the biomass heating movement bemoan warm winters, low fossil fuel prices and the slow pace of conversions to biomass heating systems.  But systems are being put in place to adopt renewable heating and that we can be part of, but […]

HPBA lawsuit extended again in hopes of renewed talks with EPA

Posted by Earth Stove on June 30, 2017 with No Commentsas , , , , , ,

The US Court of Appeals for the DC Circuit agreed to yet another extension to the lawsuit brought by the Hearth Patio & Barbecue Association (HPBA) and the Pellet Fuel Institute (PFI) against portions of the EPA’s 2015 residential wood heater regulations. HPBA “hopes to be back in talks with the EPA” said Rachel Feinstein, […]

The Alliance for Green Heat pursues retailers advertising uncertified wood furnaces

Posted by Earth Stove on June 27, 2017 with No Commentsas , , , , , , , ,

Six of the nine retailers AGH contacted stopped advertising uncertified furnaces within two weeks Indoor furnaces are usually in the basement, but can be in a garage.  Eitheroption often leads to better fuel storagepractices than outdoor boilers andgreatly reduces jacket losses. On May 15, 2017, EPA regulations took effect that required all wood furnaces to include […]

Coal Heating in the United States

Posted by Earth Stove on June 18, 2017 with No Commentsas , , ,

By John Ackerly & Melissa Bollman Alliance for Green Heat This paper was prepared for the Warsaw Stove Summit which brought AGH and scores of experts in coal and wood heating from 19 countries to Poland in May 2017. SummaryThe US Census Bureau estimates that approximately 127,000 households used coal as a primary heating fuel […]