Steven Harris Wants to Hear from You — 24 Comments

  1. Hello is there a way for us small farmers to utilize some of bio gas designs that families and farms use in places like India. They use both the energy and the waste from these old school low tech to improve their lives and soil. Any ideas or sites thanks

  2. Hello Steve,
    I am wondering about Solar Stirling engines and / or thermal Batteries. I have a small stream on my 3/4 ac. lot on a NE aspect. The watere is only knee deep so I don’t think there is enough head for micro hydro. The sun hits the water enought that during summer the surface tempeture of the suronding stones can get prety hot. The cool end of the drive could come from the creek. I would like to hear your thoughts.

  3. i want to know about being able to build a pump for water using a low flow/low fall stream. my stream is not this bad but it’s not great. thanks

  4. I would like to know about low power LED lighting. I am building a house this year and I have a high ceiling in the great room and would like to put in long lasting energy efficient lighting. However I know that LED’s are low voltage DC devices. Would there be a way to run a string of them on one AC-to-DC converter?

  5. Question for Steve: is it possible to run a diesel engine on biogas or would it damage the engine? Another question if you have time. I have been contemplating using an old style 8 ft diameter satellite dish to make a solar concentrator to make steam. How/what is the best way to make a passive solar tracker?

    Thanks Steve and thanks Jack for getting Steve on TSP!

  6. On the issue of wood gas, which types of fast growing wood that work with coppicing will produce the greatest energy output? I’m assuming things like Black Locust with a very fast growing, dense wood would be preferable, but I’ve also heard that the resins in conifers make the gases they produce more readily combustible. Are some types of wood better for heat, and others better for generators (or any engine)?

    Since pyrolosis isn’t limited to vegetation, what are your thoughts on the burning of household wastes? Since the resulting gasses are being burned, it should be cleaner than burning a pile of trash in an open field, with fewer odors. Is this a viable way to get energy back from trash? If so, what materials are best suited, and which should be avoided?


  7. I’m DEFINITELY interested in converting a natural gas generator to running on woodgas, but I also definitely don’t want to ruin a high-dollar generator by not taking something into account.

    Q: Which book of Steve’s addresses building a wood gasifier and hooking up a generator?

    Comment: For folks with the ability to store wood chips, get in touch with your local “tree guy” and ask him if he needs a place to dump his chipped wood. It has a lot of uses. I plan on turning it into electricity if all goes well.

  8. What would be the best type of heater to heat a greenhouse to at least thirty-five degrees Fahrenheit overnight when the outside air temperature might get down to twenty-six degrees for four or five hours?

    All the heaters out there out there seem designed to boil water in X-minutes, and run out of fuel quickly in comparison to what’s needed for this application — which is just enough heat to keep the enclosed space warm for several hours. I would rather not have to get up in the middle of the night to feed it.

    In previous years I have relied on electric heat which is costly, and could also be unreliable. I would love to hear your suggestions.

    Tampa, FL

  9. Hey Jack/Steve,

    I am interested in a device that combines Rocket Stove, Hot Water Heater & any “waste heat” generates Steam that in turn runs an alternator to generate electricity. Is it possible? Is there such a device?

  10. I ordered USH2 Hydrogen Car and Multi-Fuel DVD, Should be interesting…

    Very nice guest on the show on a topic I’ve been researching for years.

  11. How about a gasifier sized for 5-15 hp motor. Something to fit on a small trailer to power a small quad/large lawn mower or welder/genset. I would like to mount this genset:
    on a small trailer with a wood gas generator for portable power. I can use the quad/tractor to transport the trailer, than power the genset once it’s on location. It can weld, run power tools with brushed motors, run some lights or charge batteries to run an inverter. I have it on LP, but wood gas should make a nice cheap, sustainable set up. Thanks

  12. I am looking to build a wood gasifier that will run a 5000 watt generator that will charge a bank of batteries that i could use as a source of power in a outage or to plug a small portion of my appliances into, any tips above what is in your book?.

    Alittle background to the question i live next to a sawmill and have access to large amounts of sawdust that are a nuisance to the sawmill operator, my idea is to run this gasifier with sawdust as fuel to create woodgas that i could run a 5000 watt generator to charge a bank of batteries (with inverter) that would be my backup power for essential power needs in the case of power outage and other times as a way to cut my grid usage by wiring a seperate line of 120v into a room or two to run small things in the house, i ordered your book “Hydrogen Generator Gases for Vehicles and Engines: Volumes 3 and 4” as beginning to my plans for such a system just wondering if you had any tips for this specific application.

    Also any rough guidelines on how many pounds of wood waste (chips, dust, ect.) it takes to create the energy equivalency of a gallon of gasoline?.

    Thanks Steven for any input you might have and thanks Jack for bringing this topic to our attention.

    • @Samuel ,

      Based on these 3 sites and a bit of math:

      Gasoline has ~114000 btu/gal, so at 6 lb/gal that works out to 19,000 btu/lb.

      Wood btu’s vary based on resinous and density, but lets use an average of 8500 btu/lb.

      19,000 / 8500 = 2.24

      On average you’ll need around 2.24 times more wood than gasoline, by weight. Wood however also varies in density. Based on the specific gravity chart, a rough average of common hardwoods such as maple and ash, shows a similar average weight per cubic foot to gasoline.

      So, in conclusion, a 55 gallon drum of sawdust should give you roughly the equivalent of 24 gallons of gasoline.

      • Appreciate the response those estimates are actually better then i would have guessed and i think in a few months i will give it a go, i am going to have to document this project when i do it so i can post it to youtube, my brother is in the lumber industry and disposal of sawdust is a problem for alot of operations to the point where some pay people to haul it away, this could be a great way to get free fuel.

      • I have a 50 kw gasifier and have been studying the subject for about 3 years now. In actual practice with vehicle based gasifiers the typical real wood to gas ratio tends to be 16 – 20 lbs of wood to a gallon of gas. The main issue you run into once you deal with tars is fuel prep, gasifiers can be very fussy on the fuel you feed them especially concerning particle size and moisture content. I have not seen anyone gasify saw dust the problem you will run into is bridging of the fuel over the combustion zone and slagging. There are a quite a few people who have been able to make gasifiers run on pellets, but that is also very difficult do to the same reasons and is limited to smaller gasifiers. I am not saying it cant be done I am sure it can be, but you probably be better off planning on chunking wood into small blocks at least for your first gasifier.

  13. I think 24 gals is very generous. There’s a lot of air in between the wood chips/sawdust. My guess would be more like 5-10 gals. I read about them, but have no hands on so it’s just my best guess.

    • @Mike
      I think your correct. I completely overlooked density of wood /vs/ density of sawdust. Thanks for finding my error.

      Let me revise a bit then…

      Per these 2 sites:

      Gasoline has a specific gravity of 737, where sawdust is only 210. Now I know the sawdust number would be an average or approximation, but it should give us a rough estimate.

      737 / 210 = ~3.5

      So, sawdust is ~3.5 times less dense than gasoline. Now, factor in, you’ll already need ~2.25 times more wood for the same btu as gasoline…

      3.5 X 2.25 = 7.875

      This means sawdust is going to take up 7.875 times more volume that the same weight of gasoline, to produce the same btu’s

      Now back to my original 55 gallon drum of sawdust estimation, I failed at the last time.

      55 / 7.875 = 6.98

      So, instead of my original estimation, it looks like a 55 gallon drum of sawdust works out to be the thermal equivalent to ~7 gallons of gasoline.

      As far as Samuel’s original question, ~2.25 lb of wood has the same energy potential as 1 lb of gasoline, but converting wood to gas in its original state is hard to do without a large, well made, wood gasifier. Most gasifiers I’ve seen that aren’t a commercial model, use sawdust, chips or pellets for fuel.