Exponential energy

Here’s a remarkable fact.

In the years since 1990, our global civilisation used more energy than had been used in the previous several hundred thousand years, possibly since modern humans first evolved.

No, really. All the energy extracted by burning wood, coal, gas, oil and obtained from wind, solar, hydro and nuclear fission up to 1990. That same amount of energy used again plus a bit more in a little over 20 years.

How on Earth is that possible? To begin to answer that, we need to acknowledge that we are living in a period of quite incredible change. Yet this rate of change is something that we have gotten used to. Indeed, it was something that we were born into: a period of exponential growth. What does this exponential growth in energy look like? Something like this:

This is a nice figure from the excellent Do The Math blog. The grey peak in the middle is global energy use. The red star is where we are now. It clearly demonstrates that our energy use is exceptional both in terms of the past and the future. The vast majority of this energy came from fossil fuels. Solar energy captured millions of years ago by plants and then stored under the ground. This energy is fast being depleted and its use is producing profound impacts on the Earth’s climate. There are reasons to think that fossil fuels will decrease as quickly as they increased. What will fill this energy gap? I think it’s fair to say we don’t know. More on this later. For now, let’s just examine how we got to where we are a little bit.

2009 was a special year with respect to global energy use, because it was the first time in 30 years that it went down – around 1%. That was largely due to the fallout from financial crisis of 2008 that quickly developed into an economic slump. The violent slowdown in USA, Europe and elsewhere resulted in a decrease in economic activity (fewer things were made and sold) and so a reduction in the amount of energy consumed. However, it’s worth noting that while this has been called a global economic crisis, energy use in some parts of the world continued to motor ahead. In 2009 China saw an 11% increase in energy consumption from the previous year. 11% seems quite a lot doesn’t it. 5%, the annual increase in global energy use for 2010 is quite modest by comparison.

But did you realise that if energy use increased by 5% every year, then by 2024 we would be using twice as much energy?

Global energy use is currently around 16 terrawatts. Thats 16,000,000,000,000 watts. Or sixteen trillion watts. Or sixteen million, million watts. What is a Watt? A watt is a measure of power – how much energy is used per second. A modern energy saving bulb that would light your living room uses about 20 watts. Fancy spotlights would use 100 watts. The maximum power output of a modern European family-sized car like a Ford Focus is around 100,000 watts (that’s about 130 horsepower). So our global energy use can be visualised as 10,000,000 Ford Focuss (or is that Ford Foci?) being driven foot to the floor at maximum power output continually. Non stop. Every second of every day, for every day of the year.

But with a 5% increase next year there will an additional 500,000 Ford Focuss/Focuses (really, what is the plural for this car?). By 2024 there will be 20,000,000. An annual 5% increase of anything will give a doubling period of about 14 years. There is a handy trick called the Rule of 72 to help you calculate doubling times. Simply divide 72 by the annual rate of increase. The doubling time for a 5% annual increase is found with 72/5 = 14.4. A more accurate number can be found by dividing 69 rather than 72, but 72 is often an easier number to work with as you can divide it with no remainder with 1, 2, 3, 4, 6, 8, 9, and 12. So a 6% annual increase leads to a doubling in 12 years.

This is one of the reasons why hearing people express known reserves of fossil fuels in terms of ‘current production’ can put me into a fit of jaw tensing irritation. For example a 2007 BP report estimated that global coal reserves will last 147 years. At 2007 rates of production. But the production rate of coal isn’t constant. It’s increasing. In fact it has been the fastest increasing energy source for the last couple of decades in large part becuse it produces most of China’s electricity. From 2000 to 2010 coal use in China increased 300%. There are plans to cap coal use because despite the many millions of tons of reserves within China it cannot be dug up fast enough to throw into the maw of the ever increasing number of coal fired power stations. That’s why China, altough sitting on very large coal reserves has to import millions of tons every year.

The techinque used to esimtate how long coal production can be sustained for applies to any fossil fuel and is known as the reserves / production ratio. For example, if you have one hundred million tons of coal and you mine one million tons a year 100,000,000 / 1,000,000 gives you 100 years of reserves. And given the history of human enegy use, it should be regarded with a very large pinch of salt. This figure from Wikipedia shows the clear trend in increasing global energy use.

I think it’s fair to say that suggesting energy use will suddently stabilise and remain constant is pretty unrealistic. But that doesn’t mean it has to continue either. There is another possibility. Collapse. Or at least an exponential decline that mirrors the exponential increase. We need to tread carefully here because there is much wild speculation, and outright propaganda and misinformation when it comes to this issue of fossil fuel reserves and in particular Peak Oil. However it’s perfectly possible to have a perfectly sensible conversation about this. Given that we’ve established that there has been a tremendous increase in energy use over the past couple of centuries, we can consider how this trend can continue and what are the alternatives if it cannot.

And just as important, we can ask what are the climatic impacts if we continue to burn coal, oil and gas at an ever increasing rate? Can we bear the costs of releasing all the carbon dioxide stored in the fuels that we need to keep the lights of our civilisation on? A real sense of urgency is added to these questions because putting in place alternatives to fossil fuels will take considerable time and energy. The time to do this is when there is sufficient spare capacity, or at least when building all the required infrastructure wouldn’t be ruinously expensive. We can be certain that fossil fuels will run out. The only question is when.

In the last twenty or so years we used about as much energy as humans had used in the proceeding hundreds of thousands of years. This rate of increase cannot continue indefinitely. How we transition to other energy sources will have profound impacts for future generations and the rest of the biosphere. These are the choices we are faced with right now. That may sound like a rather onerous responsibility. But we are on the right side of the curve – a world of plentiful energy and relatively benign climate. Taking a look past the peak just means broadening our horizons and getting a deeper appreciation of what it means to be alive now and what sort of a life we would want our decendents to have.

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