Franks said:
So really, this brings me back to my point from the other thread. If we wanted a real life comparison of pellet stoves in order to see if this technology does what it says. (without me saying "well this guy went from 6 tons to 4 tons etc) a lab test really wouldnt cut it? We are waiting on the Webmaster to arrange such a test. How do you determine Lbs of fuel in x heat into the room as an equation? If the Europa is designed to use 30-40% less fuel than a typical pellet stove, how do you prove it? My simplified idea was to have 2 rooms, same size, same construction. Install a Europa in one and a different stove in the other, set the thermostats on 70 and see how much fuel each stove uses to maintain the temps over a week long period. If stove A uses 8 bags and the Europa uses 5.5 bags and the test can be run multiple times with similar results, that would settle the matter, wouldnt it?
I'm hoping BDPVT can chime in here since he seems to be able to cut thru all this mumbo jumbo. Like I said before, if I'm wrong..I'm wrong. I'd rather find out I'm wrong sooner than later.
As far as folks that bought stoves from me so far, they are all heating their homes with a tiny amount of fuel. This makes them happy. I don't have a single Europa customer that buys more than 3 tons of fuel per year. (we have to see after this year if that stays the same) The folks that swapped out the ole "drop pellets in a tray with holes in it" stove with the Europas are reporting much less fuel usage. So, even though I may be off on my understanding of the number, we do have a bunch of very happy customers thus far.
BDPVT, I passed along your response to Claude and I'll post here when he gets back to me.
Fair enough Franks. Let me attempt to cut through all the hype that manufacturers love to throw around to confuse the consumer.The pellet stove net efficiency rating published by manufacturers is a combined rating which includes combustion efficiency, electrical efficiency and heat transfer efficiency. Pellet stoves mostly burn at over 98% combustion efficiency, and the electrical efficiency is about 99%. Assume, for the sake of argument, that the heat transfer efficiency of a pellet stove is 60%. If you add up 98%, 99% and say 60%, you get 257. Divide that figure by three to get the overall efficiency and it comes out at 85.7%.
78% is the EPA’s assumed default efficiency for a pellet stove’s overall performance. Its clear then, that the heat transfer efficiency of pellet stoves is often less than 60%. The published Btu rating of a pellet stove relates to its combustion efficiency. This is a measure of the heat produced from burning fuel. It does not directly relate to heat available to the home as some of it disappears up the flue.
One pound of hardwood pellets will produce around 8,200 BTU’s. Softwood pellets slightly more. As combustion efficiency is so good in pellet stoves, this figure is very close to the actual heat ‘input’ of the stove. So take a stove with a published rating of 40,000 BTU/hr. Divide 40,000 by 8,200 and you see that at that output, the stove is burning 4.8 lbs. of pellets an hour. This ‘heat input rating’ is the main figure we have for assessing the capability of a pellet stove.
As well as assuming an efficiency of 78% for pellet stoves, the EPA also stipulates that they produce particulate emissions of less than 2.5 grams per hour to be approved. Tests for this must be carried out at an independent testing laboratory such as Omni. To be exempt, a pellet stove must have an air to fuel combustion ratio of more than 35:1.
From the above heat transfer efficiency figures, it’s clear that there must be a wide range of heat exchanger efficiencies in pellet stoves. Claims of heat transfer efficiencies much higher than 70% seem to be beyond the practical limitations of the Laws of Thermodynamics.
To be effective a heat exchanger must have a large surface area, and the stove must direct turbulent air evenly over that area. Bottom line? A pellet stove's ability to heat your home is only as good as the efficiency of its heat exchange system. The data below was copied from the Paromax website. It is an apples to oranges comparision. Most EPA certified pellet stoves have net efficiency similar to the Europa. I am not knocking the product, seems like a great design, just can't support the hype with the facts.
Net Efficiency (%)
Conventional wood stove
54%
Catalytic wood stove
68%
Non-certified pellet stove
33.4% to 70.5%
Paromax Certified pellet stove
86%
Masonary heater
54% to 65%