Lessons in building a 120-Watt thermoelectric wood stove

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