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Domenick
Damn, another brain-fart! Use cheap Vodka.
How much ethanol is too much
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Pinecone
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As stated, rubbing alcohol is isopropanol.
It is specifically allowed in my plane up to 1% to deal with water contamination. Other models of the same make allow up to 3%. No idea why the difference.
GaryM
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Gary M
Propyl alcohol generally implies it is 1-propanol, with the hydroxyl at the end of the three-carbon chain. Isopropyl alcohol is 2-propanol, with the hydroxyl on the middle carbon. Not that it is particularly relevant to the discussion at hand.
My references say the opposite: ethanol has about 72% of the energy that gasoline does.
Ethanol: 82,800 BTU / gallon. Gasoline: 114,500 BTU / gallon.
Gasoline gallon equivalent - Wikipedia
Agreed here. Blending ethanol into gasoline does not provide net environmental benefits and has significant costs. Ethanol blending mandates serve mainly political purposes, not engineering or environmental benefits.
chemgeek
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When I was teaching a course on "Energy and Society," one of my favorite quotes was from Al Bartlett, who wrote “Modern agriculture is the use of land to convert petroleum into food.” When ethanol is used as a fuel, we are using fossil fuels to create food to create fuels, which is a gross abuse of thermodynamics.
The same argument can be applied to using fossil fuels to produce heat to produce electricity to produce heat. If one is going to engage with fossil fuels to produce heat one can just do it directly.
The same argument can be applied to using fossil fuels to produce heat to produce electricity to produce heat. If one is going to engage with fossil fuels to produce heat one can just do it directly.
chemgeek
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This depends on the non-fossil-fuel fraction of electrical generation, and the temperature differential the heat pump is operating in. In cold climates, ambient air heat pumps may not be efficient enough to produce sufficient heating.
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Domenick
How is that possible when modern home gas furnaces burn at 97% efficiency? Energy can not magically be created.
Even if the electricity running the heat pump is produced by the best combined-cycle gas turbine power plants, such turbines only achieve about 65% efficiency. Solar and wind, which despite a common misconception are not 100% efficient in terms of fossil fuel use to design, manufacture, transport, construct, and maintain, can't make up the difference.
I've always wondered if direct heat to electricity, thermoelectrics, are more efficient.
flyingbrit
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It is because a heat pump does not "generate" heat, it just moves it from the outside of the building to the inside. They are rated by Coefficient of Performance or COP. This is defined as (effective energy out)/(energy in). A typical COP (older unit) is 3. This means that for every kWh electricity it consumes, it outputs 3kWh to the building. If we call this "300% efficiency", then when combined with your 65% efficiency the overall result is 195%, higher than a resistance heater which is 100%.
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See this answer below. I had to do such a calculation for P-chem a long time ago when we were learning about Carnot cycles. "Efficiency" may not be the best word for cold weather. A given heat pump can only move a certain quantity of heat, just as a furnace needs to be properly sized for a building and climate.