In TCASE 3 – The energy demand equation to 2050, I concluded the following:

The world in 2050 will demand ~700 EJ of thermal energy, or roughly 300 EJ of electrical energy. This will require ~10,000 GWe (10 TWe) of generating capacity, which is a 5-fold increase in electricity generating capacity, or 680 MWe, every day, for the next 40 years (2010 to 2050).

Given the large uncertainties associated with this forecast, the actual value could easily be as high as 15 TWe, which would up the daily built-out rate to a little over 1 GWe per day. But let’s stick with 680 MWe rate for this post.

What would that mean in terms of today’s zero-carbon (when generating) energy sources? Consider three technologies that are potentially (i.e., theoretically) able to be scaled up sufficiently to do this job (wind, solar thermal and nuclear fission), and then look at the limit analysis (what would be needed for any one technology to do the whole job — accepting that in reality, there will always be some diversity of energy technologies that are deployed worldwide). I will, for simplicity, use US capacity factors for these energy sources (solar thermal from Spain), based on the latest (2008) data. We can assume the US situation would be reflective of global conditions if the technologies are properly deployed worldwide (with due expertise and siting considerations).

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1. Wind turbines. Wind power collects ~2 W/m2 (or 2 MWe per km2), and this figure is not really dependent on the turbine size. (If you have larger turbines, you need to space them further apart. If you build large turbines with tall towers, the increased hub height does access stronger winds, increasing the yield by ~30%). The 2008 US capacity factor for wind was 23.5%. For our unit, let’s choose a widely deployed turbine, the 2.5 MWe (peak), the GE 2.5xl (rotor diameter = 100 m, hub height = 75 – 100 m, cut-in windspeed of 3.5 m/s, peak at 12.5 m/s, cut-out at 25 m/s).

To get 680 MWe average power, 680/0.235 = 2900/2.5 = 1,160 GE 2.5xl turbines per day, worldwide, spread over 340 km2 of land area (a square 18.4 x 18.4 km). Based on the University of Sydney ISA report (p145), which also agrees with Prof Per Peterson’s figures, this will consume ~1,250,000 tonnes of concrete and 335,000 tonnes of steel per day. Every day, from 2010 to 2050. Adding 1 day’s energy storage using NaS batteries (to make it equivalent to the solar thermal example below), increases the mass of steel required to 455,000 tonnes per day (see chart at bottom of the post).

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2. Solar thermal. In good desert locations such as the Sahara or central Australia, concentrating solar power would access ~15 W/m2 (or 15 MWe per km2). In Spain, it is closer to 10 W/m2. These figures are derived after taking account of mirror/heliostat spacing required to avoid shading. It agrees with current experience with solar thermal. Case in point (from Mackay 2009):

“Andasol – a “100MW” [is a] solar power station under construction in Spain. Excess thermal energy produced during the day will be stored in liquid salt tanks for up to seven hours, allowing a continuous and stable supply of electric power to the grid. The power station is predicted to produce 350 GWh per year (40 MW [average]). The parabolic troughs occupy 400 hectares, so the power per unit land area will be 10 W/m2.”

The Andasol-1/2 plant will will have a capacity factor of (100 x 8760)/350000 = 40% thanks to its 7 hours of thermal storage (without thermal storage, the CF of solar thermal is 15-22%). Let’s take Andasol as our exemplar.

To get 680 MWe average power, 680/0.4 = 1700/100 = 17 Andasol plants per day, worldwide, requiring (in an ideal desert location) 45 km2 of land (a square 6.7 x 6.7 km). Or, to put it another way, this means rolling out 520 m2 area of mirrors field per second, every second, from 1 Jan 2010 to 31 Dec 2050.

The material figures for the parabolic trough Andasol plant come from the detailed NEEDS report (p88). Based on these carefully document figures of an operational solar thermal plant, a 680 MWe build would equate to 2,215,000 tonnes of concrete, 690,000 tonnes of steel per day — shipped out to a remote desert site, each and every day, from 2010 to 2050.

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3. Nuclear fission. The AP1000 reactor, a Generation III+ design by Westinghouse that is now being heavily deployed in China, has a small concrete/steel footprint compared to other designs (see figure) — about 100,000 m3 of reinforced concrete incorporating 12,000 tonnes of steel rebar. The AP1000 unit’s island buildings would cover about 4 ha (0.04 km2) and generate 1,154 MWe (peak) at a capacity factor of 91.5% (based on US 2008 operations).

To get 680 MWe average power, 680/0.915 = 743/1154 = 0.64 (close to 2/3) AP1000 plants per day, worldwide, or roughly 2 x AP1000 reactors every 3 days, from 2010 to 2050. (This would require ~160,000 tonnes of concrete [based on 2.4 tonnes per cubic metre] and 10,000 tonnes of steel per day). Compare this to the figures for wind and solar thermal given above!

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In the case of wind turbines, much of the land below could presumably be used for other purposes (e.g. livestock). This is not true of solar thermal — the desert ecosystems under these mirrors would be destroyed. Nuclear sites would be restricted industrial zones, as they are today.

What’s missing from the above? Plenty! For instance, the above calculations take NO account of relative cost of implementing any of the above built-outs, nor does it consider the issue of overbuilding and geographical distribution, unit/facility operational lifetimes, large-scale energy storage and backup requirements, relative contribution to grid reliability, etc., etc. In reality, as I shall explain in the future, the figures I cite above for wind and solar, huge though they are, will turn out to be severe underestimates. The devil in these details will be explored in later posts in the TCASE series. I will also compare historical build rates to see how they stack up against the above projections (for renewable energy and nuclear power).

The main point of this post, TCASE 4, is to take a one step in quashing the absurd ‘bait-and-switch’ meme that some disingenuous anti-nuclear folk repeat: That because the energy replacement challenge facing nuclear energy is huge (a 25-fold expansion on today’s levels), it couldn’t possibly do it, so renewables are our only sensible option. On the basis of this post alone, any objective reader can see that this is pure, quantitatively unsupportable, nonsense. It’s going to be really tough, no matter what — and believe me, I’ve not even warmed up on the problems with renewables taking the lion’s share of the work.