Climate change

October 14, 2009

TCASE 3: The energy demand equation to 2050


Updated 13/10/2009, based on post comments. Bottom line: 2050 power demand will be ~10 TWe of electrical generating power — a 5-fold increase on today’s levels, requiring the construction of ~680 MWe per day from 2010 to 2050.

Before we look in detail at the various low-carbon energy technologies that may provide the means to move away from fossil fuels, it is worthwhile considering what our future energy targets are likely to be. That is, what are plausible energy demand scenarios?

In the developed world (US, Europe, Japan, Australia and so on), we’ve enjoyed a high standard of living, linked to a readily available supply of cheap energy, based mostly on fossil fuels. Indeed, it can be argued that this has encouraged energy profligacy, and we really could be more efficient in the mileage we get out of our cars, the power usage of our fridges, lights and electrical appliances, and in the design of our buildings to reduce demands for heating and cooling. There is clearly room for improvement, and sensible energy efficiency measures should be actively pursued. More on that in later posts.

In the bigger, global picture, however, there is no realistic prospect that we can use less energy in the future. There are three obvious reasons for this.

1) Most of the world’s population – collectively, the developing world – is extremely energy poor. A quarter of all humanity, some 2.5 billion people, have no access to electricity whatsoever. For those that do, their long-term aspirations for energy growth, to achieve something equating that used today by the developed world, is a powerful motivation for development. For a nation like India, with over 1 billion people, that would mean a twenty-fold increase in per capita energy use.

2) As the oil runs out, we need to replace it if we are to keep our vehicles going. Oil is both a convenient energy carrier, and an energy source (we ‘mine’ it). In the future, we’ll have to create our new energy carriers, be they chemical batteries or oil-substitutes like methanol or hydrogen. On a grand scale, that’s going to take a lot of extra electrical energy! This counts for all countries.

3) With a growing human population (which we hope will stabilise by mid-century at less than 10 billion) and the burgeoning impacts of climate change and other forms of environmental damage, there will be escalating future demands for clean water (at least in part supplied artificially, through desalination and waste water treatment), more intensive agriculture which is not based on ongoing displacement of natural landscapes like rainforests, and perhaps, direct geo-engineering to cool the planet, which might be needed if global warming proceeds at the upper end of current forecasts.

In short, the energy problem is going to get larger, not smaller, at least for the foreseeable future. To project just how much energy will be needed is a widely debated topic. I cannot possibly provide you with “the answer”, so what I shall instead do is provide “my best guess”, for situation in the year 2050 — about four decades from now. Realistic or not (that’s a judgement call), I’ll use this as a reference scenario for later TCASE posts (although I may modify it, depending on what comments I get in this thread). For definitions of power and energy, please read my energy primer (TCASE 2).

At present, the primary world energy demand is very roughly 500 exajoules (EJ). Most of that is thermal energy, with electricity generation equivalent to a mere 60 EJ. To put that in terms of power, 1 gigawatt (GW) = 0.000000001 EJ/s, so a 1 GW nuclear power station, running at 90% capacity factor, yields 0.03 EJ/year. As such, to meet today’s world electricity demand  requires 60/0.03 = 2,000 GWe — the equivalent of 1,750 of the new AP1000 reactors. Note that there is currently about 4,000 GWe of installed electrical generation capacity, but the global average capacity factor is ~50%.

Next, consider this. The 2009 human population size is 6.8 billion, so per capita primary energy use = 0.0000000735 EJ (for Australia, it is 5.77 EJ/21 million = 0.000000274 EJ per person, or 3.7 times the global average). I assume that by 2050, the global population will have stabilised at 9 billion (i.e., 1/3 larger than today).

The Energy Information Agency’s International Energy Outlook 2009 projects total world consumption of marketed energy to increase by 44 percent from 2006 to 2030, or 1.5% per year, with the largest projected increase in energy demand coming from non-OECD economies, as expected. If this continues, by 2050 demand would have grown by 1.015^41 = 1.864 or 86.4%. (See figure on the left. Note that 1 EJ is fairly close to 1 quadrillion British thermal units [BTU], or ‘quads’ — this being the unit being expressed in the figure, which is another commonly used unit for large-scale energy. Another you may hear is a cubic mile of oil = 160 EJ.)

This gives a 2050 projected demand of 930 EJ, but given the gross uncertainties involved in any such prognostication, I’m going to happily round this to 1000 EJ, or a doubling of today’s demand. This gives 0.000000111 EJ/person. Very clearly, this assumes that the developed world still hasn’t caught up to today’s living (energy) standards of the developed world, but Australia is pretty energy profligate. By comparison the French have a per capita use in 2002 of 0.00000019 EJ per person, which is a bit closer to the global 2050 figure). Still, there’s no doubt that it’s going to be a long road to global energy equality.

In 2050, my decarbonised world must be close to 100% electrical, because human activity should be emitting very little carbon dioxide. (I count, in my ‘electrical-powered definition’, any synthetic process to manufacture fuels, and also processes like flash distillation for desalination which make use of waste heat resulting from electrical generation. There will also be some contribution of biofuels.) So, now, let’s say that by 2050 we have managed to achieve the following:

a) Transition to an all-electric society with nuclear power meeting the greater fraction of our demand;

b) Use nuclear power and renewables to create our energy carriers (e.g. batteries, hydrogen, ammonia, boron, whatever), and also use waste heat from thermal reactors for desalination; and

c) Increased technological development means that we get 30% more efficient at using energy to do work (e.g. cumulative improvements in electrical appliances, but excluding transport, see below) — that’s an 8% improvement per decade (one imagines that in reality, the biggest efficiency gains will come in the next two decades, with diminishing returns thereafter).

Now some additional calculations. Current thermal energy derived from coal = 140 EJ, oil = 190 EJ,  natural gas = 120 EJ, nuclear = 30 EJ, other (biomass, solar etc.) = 5 EJ, and then hydropower provides an additional 5 EJ of direct electrical production. To derive the expected electrical power requirement in 2050, I assume an 87% increase in energy demand, a 30% improvement due to general energy efficiency and a 75% improvement due to the switch from oil to electric vehicles. I also assume that 60% of the thermal energy from coal, nuclear and other thermal-to-electric is dispersed in producing electricity. For natural gas, I assume that 1/3 is currently used to produce electricity and 2/3 is used directly for heating, cooking etc.

On this basis, the world in 2050 would demand 700 EJ in thermal energy, which translates to 290 EJ of electrical energy (which I round up to 300 EJ). This would require 300/0.03 = 10,000 GWe of generating capacity. As you can see, under some pretty heroic assumptions, we are likely to need a 5-fold increase in electricity generating capacity by 2050. If we assume all existing power plants (fossil, nuclear and renewable) will be retired by 2050, then we have to build 10,000/(365*40) ~= 680 MWe every day for the next 40 years (2010 to 2050), to meet this challenge. (By the way, the scale of the problem doesn’t diminish if you favour renewables or ‘clean’ fossil fuels over nuclear — indeed, it gets substantially larger due to overbuilding required for technosolar and the efficiency losses involved in carbon-capture-and-storage [CCS]).

By the year 2100, we may want double this figure again — to 1,400 EJ of thermal power or 20 TWe of electricity generating capacity — which would give the global population of 7 billion (let’s assume we stablise our numbers due to improved standards of living and education levels, and then gradually decline), a per capita energy use of a little less than the French enjoy today. This would allow for global economic growth (in energy terms) over the next 91 years of a few percent per annum, and agrees fairly well with the World Energy Council’s scenario A for 2100.

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