OWB with gasification vs. tarm or eko gasifier

[knteriele]

What is the efficiency rate of an OWB/gasifier compared to a tarm or EKO?

 

[WoodNotOil]

It depends on the specific model of OWB gasifier you are talking about. This site:

http://www.gototalenergy.com/OutdoorEkoLineBoilers.htm

Claims that the new outdoor EKO has a 90% efficiency. Most gasifiers fall in the 80-90% efficiency range. That is where you want to be. You need to use seasoned wood in any gasifier to realize that actual level of efficiency.

 

[Nofossil]

It depends on the specific model of OWB gasifier you are talking about. This site:

http://www.gototalenergy.com/OutdoorEkoLineBoilers.htm

Claims that the new outdoor EKO has a 90% efficiency. Most gasifiers fall in the 80-90% efficiency range. That is where you want to be. You need to use seasoned wood in any gasifier to realize that actual level of efficiency.

I haven't seen performance data on OWB gasifiers. The OWB market seems to have a lot of dealers and maybe manufacturers as well who hide the technical details behind a cloud of marketing dust. I'm not sure that all OWBs that appear to claim gasification actually perform as a gasifier. Actual efficiency tests are hard to come by. In comparison, the EKO publishes detailed test results performed by an independent (and government certified) lab.

I hope this situation improves. There's no reason that OWBs could not be high-efficiency gasifiers, but right now I think it's hard to make an informed decision.

 

[Eric Johnson]

That's really not a "new EKO outdoor" boiler. It's a regular EKO (looks like a 40 to me) put into an insulated box for outdoor use, by the dealer. I presume it works just fine, but it's not part of the EKO product line that I'm aware of.

 

[webbie]

As nofossil says, there is a lot of marketing speak in the selling of most products today. Unfortunately, there are no standards here which must be tested to. That means - in effect - that manufacturers and dealers can claim whatever they want.

It pays to assume actual efficiencies are MUCH lower than advertised on virtually all wood and pellet burning appliances - with the exception perhaps being the European pellet units that have been tested over there.

As an example, Nofossil has carefully tested his EKO gasifier, and I don't think he has gotten a total system efficiency of over 60%. As guesswork, this would mean a regular indoor boiler is probably 35-40 and a standard OWB closer to 25%.

Bringing the boiler outside and adding piping to the system would seem to lower the overall efficiency, but not by too much if everything was properly done. As to the newer EPA OWB, given the massive fireboxes I would have a hard time believing that they match up in system performance to a smaller firebox, but perhaps NF can comment on this. My "old school" point of view was that larger fireboxes are less efficient when used at the same BTU input as a smaller box.

I hope that someday we will have some real tests for these systems....but for now it is buyer beware.

 

[Nofossil]

As an example, Nofossil has carefully tested his EKO gasifier, and I don't think he has gotten a total system efficiency of over 60%. As guesswork, this would mean a regular indoor boiler is probably 35-40 and a standard OWB closer to 25%.

As to the newer EPA OWB, given the massive fireboxes I would have a hard time believing that they match up in system performance to a smaller firebox, but perhaps NF can comment on this. My "old school" point of view was that larger fireboxes are less efficient when used at the same BTU input as a smaller box.

I hope that someday we will have some real tests for these systems....but for now it is buyer beware.

Keep in mind that I used a very stringent criteria for efficiency, not giving credit for heat loss from the boiler itself or from any plumbing, even though those heat losses still heat my house. Looking at the wood consumption vs. previous oild consumption by degree day, I get an overall efficiency more like 70% (vs the claimed and tested 85%).

The European boilers are tested, but not always under conditions that you would be likely to encounter. The EKO 80 was tested with a cold water inlet temp of 130 and a flow rate of 35gpm, for instance. It did hit 90% operating that way, though.

I'd be extraordinarily skeptical until there are true independent tests. Any boiler installed outdoors will be less efficient because you will lose heat to the outside from the boiler and the buried lines. The EKO 80 at full output loses 5600 BTU/hr through the jacket at room temperature. It would lose the same amount, or very close to it, at idle. It would presumably lose more if it were in a colder environment. I could see it losing 10% or more of the output.