you need to add references

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eak's picture
Status: Member (Offline)
Joined: May 10 2009
Posts: 1
you need to add references

The first part of this is a general comment that applies to all chapters, but I am making in 17a because of a questionable statistic presented here. The second part transitions into a complaint specific to 17a.

You need to add references to the text (e.g. links, or [1] and then at the bottom of the page provide the link) for the claims you make. I understand why you cannot go into detail in a video, but the text version should be augmented so that people can see what you mean.

Let's take your claim that "Oil represents over 50% of US total yearly energy use, while oil and natural gas together represent over 75%." Where does this claim come from? On what basis is it measured? Are you using the Lower Heating Value (LHV) of petroleum and comparing it to the kWh of electricity? When I go to the DOE's EIA website, I find that petroleum is 39.2% and natural gas 23.2%, for a sum of 62.5% (this is from their Annual Energy Review 2007). These numbers differ from yours. I cannot judge on what basis you said 50% and 25% without a reference. Their basis is the converting various to BTUs (I think they HHV method).

You should also understand the limitations of comparing high-quality energy (e.g. electricity) with low-quality energy (e.g. petroleum) using either LHV or HHV methods. The Carnot theorem of thermodynamics puts an upper bound on converting heat into useful work, and even after a  a century, practical internal combustion engines are still a fraction of this upper bound. In contrast, the Carnot theorem does not apply to non-heat energy (e.g. electricity), and one finds that one can deliver, for example, electricity from a power plant to the wheels of a car at 4-5 times the efficiency of that burning gasoline in an internal combustion engine achieves. As a result, if one were to fuel our passenger vehicles with electricity rather than gasoline, it would only take about 900 TWh (tera watt hours, or billion kilo watt hours) per year [1], which is only 23% of the 4006 TWh generated in 2007. Of course it would take 30 years to transition the US fleet to electric fueled vehicles, so this may not arrive in time to save us, but my example is meant to illustrate a more fundamental point that the form of energy matters, and so saying 50% of our energy comes from petroleum is misleading, because petroleum is an inefficient form of energy storage.

If you understand the above, then you should now reallize that your claim "Those 10 million barrels represent the same power equivalent as 750 nuclear power plants." is grossly misleading. It suggests that the US would need to build 750 1 GW power plants to eliminate petroleum, which is simply false. The 900 TWh required to fuel the 2.8 trillion passenger vehicle miles driven in the US with electricity would require only 115 1 GW power plants (operating at 90% capacity), not 750. Efficiency matters; you're off by a factor of 6.5 because of this mistake.

If 115 1 GW power plants sounds daunting, then you should realize that calculation is simplistic. The Pacific Northwest National Laboratory looked at the impact of electric vehicles on the US grid in detail and found that 73% of cars, pickup trucks, SUVs, and vans could be supported by the existing power plant infrastructure. We have that much spare capacity at the moment.

Even if you insist that electric vehicles be fueled by renewable energy (I would), then the situation is not so bad. Another way of looking at the 900 TWh is how many wind turbines or solar farms would be required. It would, for example, take 3550 sq.mi. (a square 60 miles on a side) to generate this much power from Stirling Energy Systems' SunCatchers. The cost per mile would be a fraction of what we pay today per mile for petroleum transportation. Alternatively, it would take 173,000 2 MW wind turbines operating at 30% of capacity to generate this much power. If this number seems large, consider that the US produced 303,000 aircraft during World War II. Given that these wind or solar farms could be built to match the fleet they power over 30 years, this is really quite reasonable. While one does not elimanate petroleum completely, large annual reductions in petroleum may make it possible to survive peak oil if we reduce consumption at the same rate as production declines.

[1] 2.8 trillion vehicle miles @ 300 Wh/mi, factoring in 92% grid efficiency

Please note that I've provided references in this forum post. It's not that hard!

csstudent's picture
Status: Bronze Member (Offline)
Joined: Dec 22 2008
Posts: 48
Re: you need to add references

I'd also like to ask a question about the figure that is referenced in the question above.  There are five lines on this graph - liquid fuels, natural gas, electricity, renewables and coal.  The question I have is why is electricity there?  The other items can be used to generate electricity.  For example, natural gas is listed as contributing about 25% to our energy use.  But a lot of natural gas is used every year to generate electricty.  Wouldn't that be double counting?

The only way I can make sense of that chart is if the uses for coal, natural gas, etc are used in some way other than generating electricity and the line for electricity doesn't take into account what source is used to generate it.

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