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A Short Lesson In Scale (and Global Power Demand)

By Robert Bryce - May 24, 2010 1:26 PM

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When considering the global energy sector, one of the most difficult tasks is understanding the gargantuan scale of our energy consumption.

Talking about scale should be an integral part of our energy discussion now, particularly given the large number of politicians and activists who are contending that we must completely overhaul our energy and power delivery systems and in doing so, give up all carbon-based fuels.

That notion appeals to many people. And it's been given a big nudge by the oil blowout in the Gulf of Mexico. But that notion must be confronted with reality. And that's where the issue of scale comes roaring onto the scene.

Global commercial energy use now stands at about 226 million barrels of oil equivalent. Of that quantity, about 79 million barrels comes from oil, 66 million from coal, 55 million from gas, about 12 million from nuclear and about 14 million from hydropower. Obviously, hydrocarbons are the biggest portion of the global energy mix, accounting for about 200 million barrels of oil equivalent per day.

But those quantities of energy are nearly impossible to comprehend.

What is 226 million barrels of oil equivalent? Well, try thinking of it this way: it's approximately equal to the total daily oil output of 27 Saudi Arabias. Since the 1973 Arab Oil Embargo, Saudi Arabia's oil production has averaged about 8.5 million barrels per day. [1]

So let's suppose we want to quit using hydrocarbons. Fine. Global daily hydrocarbon use is about 200 million barrels of oil equivalent, or about 23.5 Saudi Arabias per day. Thus, if the world's policymakers really want to quit using carbon-based fuels, then we will need to find the energy equivalent of 23.5 Saudi Arabias every day, and all of that energy must be carbon-free.

While Saudi Arabia provides an easily understandable metric for global energy use, what we humans really care about is power. (Remember that energy is the ability to do work. Power is the rate at which work gets done.)

Let's convert those global energy consumption numbers into power terms. That will be easy as they are provided in barrels of oil equivalent per day, and that means they are readily converted into familiar power metrics: watts and horsepower.

A barrel of oil contains 5.8 million Btu. That's equal to about 5.8 billion joules (5.8 GJ). To obtain watts, we must divide those joules by seconds. (Remember that power = energy/time). We must therefore divide our 5.8 gigajoules by 86,400 seconds, which is the number of seconds in 24 hours. [2] We must also account for the heat lost during the conversion of that oil into useful power. The result: each barrel of oil equivalent produces about 22,152 watts, or about 29.7 horsepower. For simplicity, let's call it 30 horsepower per barrel of oil equivalent per day.

Multiplying global energy use of 226 million barrels of oil equivalent in primary energy each day, by 30 horsepower per barrel means the world consumes about 6.8 billion horsepower, all day, every day. Therefore, roughly speaking, the world consumes about 1 horsepower per person. Of course, this power availability is not spread evenly. Americans use about 4.5 hp per capita, while their counterparts in Pakistan and India use less than 0.25 hp.

World Power Consumption, By Primary Energy Source, in Horsepower (Watts)

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By Seth Meyers
Source: Power Hungry: The Myths of "Green" Energy and the Real Fuels of the Future


While those numbers are telling, they are somewhat unwieldy. Thus, it makes sense to look at global power consumption in watts. Using the numbers cited above, we find that global power consumption is about 5.1 trillion watts, or 5.1 terawatts. Using watts allows us to see the disparity in power consumption much more clearly. For instance, the average resident of India consumes about 167 watts while the average Brazilian uses 516 watts. Meanwhile, the average resident of the US consumes 3,366 watts.

Per-Capita Power Consumption in the Six Most Populous Countries, in Watts

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By Seth Meyers
Source: Power Hungry: The Myths of "Green" Energy and the Real Fuels of the Future


Amidst all of our discussions about energy and power we must keep the issue of scale foremost in mind. We cannot, we will not, make a major change in our energy and power delivery systems at any time in the near future because the vast scale of those systems will make any transition away from our existing systems slow and expensive.


This article first appeared in the Energy Tribune.

[1] BP Statistical Review of World Energy 2009. See also: Jad Mouawad, "OPEC Plans Further Output Cut," New York Times, December 17, 2008. Available: http://www.nytimes.com/2008/12/17/business/worldbusiness/17opec.html?fta=y. Mouawad reports that the Saudis settled on a production rate of 8.5 million barrels per day in November 2008.

[2] Here's the math: 5,800,000,000 J / 86,400 s = 67,129 W. To account for heat lost during the conversion of energy into electric power, we must multiply the 67,129 W by 0.33, which leaves us with 22,152 W.

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1 Comment

This is certainly true. Also, most of the alternative power systems are more investment intensive. Also, especially for transportation, they require major changes in the support infrastructure.

Perhaps more significant, going forward,
China, India and other developing countries are making major investments in new coal-based power generating facilities with 40-60 year lives. That implies that the time frame for change in those economies is even longer, since a higher percentage of their infrastructure is new.

The potential for massive economic dead loss in any rapid conversion to new energy systems is awe inspiring. The potential for market failure by technologies "not ready for prime time" is also daunting.

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