we are currently making a study about the electrical efficiency of generator. how can we calculate the electrical efficiency? we made gasifier for small engine system. how can we determine the power input in the generator? thanks for reply
There are charts that get you the BTU output pr wieght. Figure out what the species of wood you are running is BTU wise by wieght. Then test run pr hour running a static load kW wise. Calculate how many BTU’s used by the amount weight consumed during testing. You can then convert the kW output to BTU’s and then put this against the amount of fuel consumed. Hope that makes sense
Just did a quick calculation. If your fuel is equivalent to 5500 BTU’s pr pound and it takes 3 lbs pr hour to produce 1 kW/hr; one kW/hr is equivalent to roughly 3412 BTU’s. So this gets us to roughly 20.67% efficiency at 3 lbs pr kW/hr
Efficiency is a very interesting number in alot of ways. I agree with what Matt has said above with one addition which is to add a measurement of how dry the wood is. The amount of humidity in wood has a major impact on how it burns.
But in a purely philosophical argument the deck is stacked against wood compared to gas or diesel. I see this mostly in heating. If you compare a wood gasification boiler to an oil boiler they both have very similar efficiency rating but in reality the wood boiler is working with the raw fuel found in nature. But the oil furnace is dealing with a highly refined product. I would like to see the efficiency from raw fuel to final energy considered but that is a much harder number to develop. I guess I would call that a total life cycle efficiency. But to me that would be the fair efficiency comparison. Otherwise you would have to compare the efficiency of the wood gas at a cool temperature to the efficiency of the gasoline or diesel fuel. That would look like a silly number because you can’t buy a bottle full of wood gas but that is the fair comparison point in my mind because both are the same finial product going into the motor.
Then there is one last thing to keep in mind. The motor on the generator has alot of engineering with gas or diesel in mind as the fuel source. The same can’t be said about wood gas it is being used in a motor designed for a different fuel. I mention this as a warning simply to point out that there is alot more room for improvement in efficency of wood gas that doesn’t exist with diesel or gas but would require extensive research and development.
My point is it depends on what you are trying to get out of an efficiency number how you calculate it. There is the old saying figures don’t lie but liars can figure.
Another thing to consider. I have seen a thread in here talking about how to capture the waste heat from gasification and the generator for home heating or some other usage. This is one way to improve the efficiency per btu of wood fuel heat. Now if this same metric was use from crude oil to kilowatt of electricity produced diesel wouldn’t look very good because there is alot of energy used to extract and refine crude oil. Then there is the cost of transportation of the fuel to the point of final consumption. The wood I burn travels less then 1 mile to get to my stove. I have to transport any diesel fuel or gas I burn about 10 miles myself to get from the pump to my house. And who knows how far that fuel has traveled to get to the gas station probably half way around the world in some cases. I will stop before I get into the hidden costs of diesel and gas which governments pay. I will just say it bothers me greatly to think about how much military force is used world wide to secure “cheap” oil based fuel for us.
OK I have finished my rant. Hopefully there was something useful in there.
To be fair you can not compare woodgas coming from the plant to other fuels. If you compare in this way, then you need to factor in extracting the fossil fuels and then the refining process. If we look at this way, that 20% efficiency starts to look very good!!
Excellent post DanNH.
Mr C. A. your question is relevant in a limited sense.
The answer is useful in “selling” the use of a woodgasifier generator system to someone. Investors. Institutions. Powers-That-Be. Even selling the use to yourself. Or your spouse (the hardest sell by far!!)
This question has also been asked and presented as a monetary cost comparison per kilowatt-hour.
Two excellent readable articles here on the DOW in the library section discuss much efficiencies and costs:
World Bank Technical Paper 296
UN, FAO 72 Report
These show clearly that as long as oil and coal energy resources can be made market available; investors, institutions, decision-powers-that-be will always pull out of woodgas systems developments and use.
ONLY one parochial school in Micronesia, and one religious colony in Uruguay followed through the developmental set-backs to real did-use electrical generation systems.
The Freedom/Local Energy Independence factors; hard to math out, were the reasons for their persistent successes.
So say these reports.
J-I-C Steve Unruh
Thanks Steve. Being new here I was hoping it would be well received. As you can guess energy independence is sort of a hot button topic with me. Probably true with most people here. I am better then most people but have a long ways to go. At this pont it is time and money holding me back. I am hoping to go off the power grid next summer don’t know if I can really swing that or not.
yes on the part about engine design. The goes for Flex fuel cars, these cars are killing ethanol, as those engines are only capable fo running it but are far from designed to run it. Everything changes in ethanol engine; ignition timing, fuel runners. cam overlap timing,valving, valve sizing. If you ran gasoline in an engine designed for ethanol it would ping and detonate. Ethanol also carries some of its own oxygen and turboing can really add some advantages there. I think a wood gas engine would be quite similar to an ethanol designed engine as they share similar burn rates and octane ratings.
The newer e85 vehicles are better. IIRC they will automatically adjust based on density of the fuel. I can’t remember if they just advance/retard the ignition, or if they just reduce how much fuel is injected, but they are more efficient then the first gen vehicles.
We used to use methanol to fuel our home brew drag racers. As far as I can tell, there isn’t much difference between methanol and ethanol as a motor fuel source. (Ethanol has a slightly higher btu value per gallon than methanol, I think). Anyway, we did that because we could get faster quarter mile times with methanol in a given engine. All we did was to open up the main jets on the carburetors and, maybe make a spark timing change (or maybe not).
My point is that the engine did NOT loose any performance, quite the contrary.
(Let’s not get into the unique dangers of methanol. I think we all know about that).
Usually mucking around with the compression ratio will help as well. Apparently Nissan developed a variable compression engine.