Electric Power from Wood Gasification Furnace - or - Cogeneration in the Basement

[cguida]

Awhile back Ugly requested ideas about how to get electric power out of his wood heat operations. There was alot of speculation about how to tap the wood gas out of a boiler before it burned, so the gas could be used in an internal combustion engine to drive a generator.

The link below is to an experiment in Germany that plugged an external combustion stirling engine into the internal ceramic conbustion chamber of a boiler, as per the attached pictues.

Pretty neat idea! I hope somebody develops it and makes it practical for the rest of us.

(broken link removed)

 

[2.beans]

fred seton is working on a bolt on turbine for his boilers. at least that what he said to me once.

 

[jebatty]

The idea is intriguing, but my intrigue is tempered by the inefficiencies in this type of co-generation, along with wondering whether using the combustible wood gas to drive the engine will leave enough combustible wood gas to provide heat for the home, and what is done to capture the waste heat from the engine. I think most co-generation revolves around first using the combustion process to drive a turbine/generator, and then using the waste heat for district energy.

The inefficiencies start with the laws of thermodynamics, which pretty much indicate that converting one form of energy to another results in about a 50% loss. Here you have the combustion inefficiency in generating wood gas, then using the wood gas to combust again to drive an engine, and then using the engine motive power to drive a generator.

 

[cguida]

Hi Jebatty,

The PDF article has pie graphs re: heat output and electric output. Seems to be about 75% heat, and 25% power generation. Since it is all in the basement, heat going into the Stirling (minus the electrical power), stays in the house. So it is not lost.

In fact, given that it is just passively tapping into the existing 'heat stream', I don't see where there are any new inefficiencies at all. Instead of having just space heat, you get space heat and power.

Where's the down-side (except, of course, for the cost of the gizmo?)

 

[Fred61]

The idea is intriguing, but my intrigue is tempered by the inefficiencies in this type of co-generation, along with wondering whether using the combustible wood gas to drive the engine will leave enough combustible wood gas to provide heat for the home, and what is done to capture the waste heat from the engine. I think most co-generation revolves around first using the combustion process to drive a turbine/generator, and then using the waste heat for district energy.

The inefficiencies start with the laws of thermodynamics, which pretty much indicate that converting one form of energy to another results in about a 50% loss. Here you have the combustion inefficiency in generating wood gas, then using the wood gas to combust again to drive an engine, and then using the engine motive power to drive a generator.

I think you may have lost track of the fact that this is a stirling engine. The combustion in the boiler doesn't change. They are simply iserting the gas chamber of the stirling into the combustion chamber and picking up some of the heat. Theoretically, there is only so much energy produced so some will go to heat for the system and some will produce electricity. My system is certainly large enough to handle more load since all the heat is not lost. Distributing the waste heat in an efficient manner could be an issue unless they have found a way to distribute through a hydronic loop. Here's a company in New Zealand that is producing a gas fired co-generation unit that installs like a dishwasher into kitchen cabinets.

http://www.whispergen.com/main/HOME/

 

[Fred61]

Just took another look at their schematic. They do have a cooling loop going to the storage tank.

 

[sweetheat]

my thoughts of a year ago have been realized by harnessing producer gas from a Gasser to power a sterling engine that can power a generator. the self sufficient germans techies take it one more step farther. can anyone post more from fred seton?sweetheat

 

[James Gautsch]

Found this site many months ago. Snoop around and view all the videos. (broken link removed)

 

[Como]

I had a look at CHP system at a recent show. These were small domestic ones that worked on Natural Gas or Propane. Very interesting if I had Natural Gas, Propane costs more than Electricty where I am so pretty pointless.

 

[peakbagger]

Once someone figures out how to make a reliable cost effective sterling engine, I expect that this will become a good option, but I havent seen any that meet the "reliable and cost effective" yet. STM engines got close on a larger scale but went bankrupt. These folks http://www.stirlingenergy.com/had better come up with one, as their whole business plan is riding on it.

Dean Kamen of Segway fame has been working on Sterling engines for longer than Segways, he has a had a couple of prototypes out in the field, plus a lot of good PR on 60 minutes a few years ago, but to date, no real production units. Last thing I heard he was working with Think Electric cars to develop a Sterling engine for hybrid auto use. Sunpower used to have a prototype wood generator for sale but theri website doesnt mention it anymore.

There are several European Sterlings that have been linked to in previous posts but I dont know if any of them are in mass production.

 

[cguida]

This is the Industrial Scale WoodChip version -- not all that large (35kw electric output), but probably bigger than most basements can accomodate. Maybe it should go in an outbuilding around the back someplace. I'm afraid to ask what it might cost...

http://www.sd.econtent.dk/

 

[webbie]

This is something that has been talked about forever - and actually some bigwigs in our industry have fantasized about working on it.

I did some cursory research and concluded that the efficiency level of most existing technologies would make it VERY difficult to do this on a small scale. For it to be of real value, an efficiency of 50% or more would have to be achieved. I'm guessing at that because we can beat that by a lot with the best THERMAL designs....and also that the cost of the equipment would be high and have to be figured in, etc.

Years ago there were some solid state devices that you could clip to your woodstove and generate a small amt of electric with. Maybe someday the solar PV business will throw off some similar technology that works on radiant heat wavelengths. Given a free standing stove, this might make sense because you are simply capturing a small part of the heat being thrown off (at a high efficiency) and what you are not capturing is heating the house anyway.

For now, I'm afraid, larger scale is the way to go.

 

[Delta-T]

Craig, i know some research is being done relative to converting solar active materials into IR. I beleive their are variations on the Fullerine carbon molecule that can do this, but at present the efficiency is below even the PV efficiencies. The big plus is that Fullerine technology is cheap and easy. I don't expect sterling tech to ever really take off. Its been around since before steam and there are still no real broadbase applications. I know the Swedes have a nuclear sub that uses a sterling and then condenses for a closed loop to remove steam emissions (stealth, woo hoo). I belive Kamen's set up was designed to power cell phone repeaters and weren't designed for efficiency, rather they were designed to allow the use of just about any fuel available. I heard that 3rd world countries were the target market. We all know that its more important to have cell phone than clean water.

 

[cguida]

Just for the recdord, the Danish woodchip (25-55%moisture) implimentation (35kwectric/140kw heat) costs a mere 290 thousand Euros, -- about $377k dollars.

Maybe when I get my tax refund....

 

[cguida]

forgot the pictures...

 

[steam man]

As mentioned above I'd like to see a thermoelectric generator put on a boiler to at least generate enough electricity to power its own pump(s) and controls. Here's a link to one idea: (broken link removed to http://www.popularmechanics.com/science/earth/4243793.html)

Mike

 

[akal60]

the problem with wood gas in a gasification boiler most probably would be keeping the point that you removed the gas in the reduction zone, if not you end up with tar gas that will be hard to filter and destroy your engine ,I am working with the Allpower g.e.k. a kit that is sold online to work out most problems in producing clean fuel gas. the headaches are fuel bridging too damp fuel chips, too much tar in the gas, steady fuel feed for proper gasification. a unit designed for boiler use would be hard put to make clean fuel gas.g.e.k. has a Honda accord driving around Oakland California, also many people have run generators up to 5.5kw from them. do a Google for Allpower and see for yourself, it's quite interesting they have a wikki and forum too.

 

[cguida]

When I first heard about the German experiment, I had no very clear idea of what a Stirling engine was. It took me a while to realize that this is an External combustion engine, and thus side-steps all the problems of dirty gas. And since it is all in the basement, it also side-steps all the efficiency concerns since (engine) heat is all still in the house, and thus not wasted. The External Combustion feature allows the engine to take advantage of a wood gas boiler's best feature -- the small, very hot gas combustion area. The engine can tap into the heat without goofing up the gas stream or the combustion.

I have a neighbor who deals in wood chips by the ton. If somebody out there would kindly equip me with 290 thousand euros, I'd be happy to run a demonstration project. In fact better still, make it 480 thousand Euros for thhe 2 generator version. That way we could leave our computers on all night. Thanks very much!

 

[pybyr]

the problem with wood gas in a gasification boiler most probably would be keeping the point that you removed the gas in the reduction zone, if not you end up with tar gas that will be hard to filter and destroy your engine ,I am working with the Allpower g.e.k. a kit that is sold online to work out most problems in producing clean fuel gas. the headaches are fuel bridging too damp fuel chips, too much tar in the gas, steady fuel feed for proper gasification. a unit designed for boiler use would be hard put to make clean fuel gas.g.e.k. has a Honda accord driving around Oakland California, also many people have run generators up to 5.5kw from them. do a Google for Allpower and see for yourself, it's quite interesting they have a wikki and forum too.

The GEK looks really interesting, but I'd never want a producer gas generator in or connected to living space- since one of the major components of producer gas is carbon monoxide.

Please _do_ keep me/ us posted on your experiments with the GEK.

 

[2.beans]

i think fred setons was to heat oil to heat water to steam to turn the turbine then use your house/storage to cool the water.

 

[canyon]

Great thread!
There is another potential version for cogeneration that is now used for small scale (relatively) geothermal up here in Alaska at Chena Hot Springs. I'm not sure what it is called, but Bernie (an owner) explained it to me once with technical drawings and what I understand is the turbine is run in the evaporation expansion zone venturi area of a refrigeration/heat pump cycle. Bernie was all excited about the possibilities of cogeneration with a scaled down version for wood stoves/boilers or even automobile exhaust piping , but I haven't heard anything since (although it could be because he has a lot of irons in the fire,bad pun intended).

 

[peakbagger]

The Chena system is an Organic Rankine cycle. It uses a low temperature hot spring for a heat source and a local river for cooling. Unfortunately it is a very inefficient process that converts about 10% of the incoming heat into electricity and the remaining 90% warms up the river. The fuel is free but the equipment isnt and the equipment needed needs to b e very large due to the low efficiency. There is a limitation with the system that the heat rejection source needs to be a cool as possible, in a lot of areas of the US it would be hard to hit during summer. It works like a normal steam power plant but uses a lower boiling point liquid than water.

So think of the practicality of burning 10 cords of wood for every 1 cord equivalent of electricity and end up having 9 cords of warm 80 degree max temp water to heat with.

 

[canyon]

Cogeneration or CHP isn't necessarily only about the power or efficiency of generating it. If you have a boiler that you are firing for heat in the winter and a way to tap a portion of the high temp heat post combustion it could be wildly inefficient in generating that power from heat if you can still use the rest of the heat. The Chena hot springs is relatively cool as far as geothermal goes. In a boiler at the proper location we could be taking a little bit of a lot hotter temperature. The temperature differential might not be such an issue for part of the winter when it is cold out. Plus, There could be a use for the heat absorbed by the "cooling" medium so the efficiency calculation gets a little complex. To have a small amount of electricity when firing a boiler could be key to offset the lack of solar power in the winter. Just thought for the theoretical/tinkering types of which I am kin to.

 

[sparke]

I have not read this whole thread so pardon me if I re-post some info. The technology of using wood gas to run internal combustion engines has been around since WW2. I have been studying this for a while. I also know people in the building stages of a wood boiler/ generator combination unit. they have those type units running in Europe.

Here are a few links I have in my bookmarks:

http://www.gengas.nu/byggbes/11.shtml This is the same design put out by FEMA I think.

http://www.vedbil.se/dagbok/mera/indexe.shtml A car and farming equipment that runs on wood gas. All home made.

(broken link removed to http://victorygasworks.ning.com/) Sales, informational, and a community of DIY's

(broken link removed) FEMA literature.

 

[Dune]

Thanks for posting these Sparke. I have seen some newer tech, but this is a good reminder.