Climate change

January 5, 2009

Renewable energy cannot sustain an energy intensive society

Filed under: Renewable Energy — Barry Brook @ 1:05 pm

At least that is the argument put forward by Dr Ted Trainer from the University of New South Wales. To quote:

It is commonly assumed that greenhouse gas and energy problems can be solved by switching from fossil fuel sources of energy to renewables.  However little attention has been given to exploring the limits to renewable energy.  The main problems are to do with the magnitude of the supply tasks that would be set and the difficulties that would be encountered integrating large amounts of intermittent renewable energy into supply systems. [I] argue that wind, photovoltaic, solar thermal and biomass sources, along with nuclear energy and geo-sequestration of carbon could not be combined to provide sufficient energy to sustain affluent societies while keeping greenhouse gas emissions below safe levels. The case is strongest with respect to liquid fuels and transport. [There are also strong] reasons why a “hydrogen economy” is not likely to be achieved.

So where is Ted coming from with such a dismal conclusion? Ted’s principal thesis is that itermittency of supply is the Achilles’ Heel of renewable energy when operating at the scale of complete, society-wide energy replacement. The problem is far worse if projected rates of economic and energy growth are factored in, and worse again if we try to imagine a scenario where the currently developing world nations attempt to achieve the same standard of living as those in the developed world.

Ted has put together a 37 page primer which summaries the content of his recent book published by Springer (Renewable Energy Cannot Sustain a Consumer Society; Trainer, T 2007, 200 p.). With his permission I have made a PDF copy of this primer available for download here.

Some selected quotes from his primer help illustrate the basis of his arguments and the underpinning of his calculations (EJ = exajoules of energy, GW = gigawatt):

[R]enewable sources tend to be alternative rather than additive.  Therefore it is not a matter of having each renewable source carrying a fraction of the load all the time.  If we build one unit of wind power and one unit of PV power we would not necessarily have two more units of renewable energy capacity; sometimes we would have no more, e.g., on calm nights.  This means we might have to build two or even four separate systems (wind, PV, solar thermal and coal/nuclear) each capable of meeting much or all of the demand on its own, with the equivalent of one to three sitting idle much or all of the time.

It is evident from the graphs from Oswald et al., Coelingh, and Davey and Coppin that no matter how much wind capacity we added there would still be several times a month even in the best wind time of the year when more or less the whole X GW needed would have to come from coal or nuclear plant, and that we could cut carbon emissions to the very low required level only if we had perhaps 5X GW of wind capacity and dumped most of the energy it generated (or stored it very inefficiently as hydrogen.)  Clearly the gains from “over-sizing” the wind system would be savagely offset by the rise in total system capital costs, and it would not pay to have much more than X GW (peak) of wind plant, meaning plant capable of delivering on average about .25 of demand (or whatever the average wind system capacity fell to in view of the need to use very large areas.)

[concerning solar thermal] Some of these numbers are uncertain but when combined they indicate that the total energy loss might be 35% of the meagre gross output, meaning that a net delivered amount well under 10 W/m might reach users.  If so plant capable of delivering 1000 MW in winter would need 100+ million square metres of collection area.  At the estimated SEGS cost of $800/m (Trainer 2008) the plant would cost $80 billion.

The climate data seems to show that despite their storage capacity solar thermal systems would suffer a significant intermittency problem and in winter would either need storage capacity for four or more cloudy day sequences once or twice each winter month, or would need back up from some other sources.  This means they could not be expected to buffer the intermittency of other components in a fully renewable system.

For 2100 it is not likely that we could assume any coal use, on the grounds that no CO2 emissions will be permissible.  If 9 billion people had the per capita average energy consumption Australians are likely to have by 2050, i.e., c. 500 GJ/person the gross target would be 4,500 EJ.  If energy saving and conservation advance reduced this to 3375 EJ, and if low temperature heat could easily be derived from solar sources (again not a valid assumption for Europe and US in winter), the energy “service” target for renewables would become 2,530 EJ.

If the 844 EJ of electricity was to come equally from wind, PV and solar thermal, wind capacity would have to be about 560 times as great as it was in the early 2000s.  We would need 72 PV panels per person, at Sydney insolation, and therefore many more in Europe.

The 464 EJ for transport (i.e., the amount driving wheels) would require generation of 928 EJ of electricity ( or twice as much again if via  hydrogen) making the total electricity task 1,172 EJ, and therefore requiring a wind capacity  some 1,180 times as great as in the early 2000s (assuming the task is divided equally between wind, PV and solar thermal), again ignoring intermittency and integration problems.

There should be no need to continue.  Clearly if the 2050 budget is impossible then one that is 4 times as big and unable to use geosequestration will be far more so.  Note that the never-questioned business as usual expectation of 3% p.a. economic growth from here to 2100 would see a global economy churning out more than 16 times as many goods and services in that year as is produced and consumed each year now.

And so on (these are just a few snippets). He covers all the major renewable energy types (wind, solar photovoltaic, solar thermal, geothermal, wave), as well as energy storage issues (hydrogen, vanadium batteries, compressed air, pumped water, ammonia), conversion and transmission losses, system integration problems, liquid fuels and total energy budgets. You really do need to read the whole primer in order to properly appreciate the detailed and well-worked basis of his numbers and the system-wide scope of his analysis.

Ted’s ’solution’ is, strictly speaking, that there is no direct  solution. He says that a consumer society of the type we know today simply cannot be sustained in the post fossil fuel era. He sees the only alternative as being is that a rapid transition must be made to a ’simpler way’, focused on well-organised regional communities which have low energy demands and a local production base — admitting that the chance of achieving this is slim at best. Trainer is thinking much deeper here than just addressing the energy crisis — the simpler way is his solution to the sustainability emergency in general (climate, energy, water, food, biodiversity). More details can be found on Ted’s website.

Trainer has also written a telling critique of the energy assumptions embedded within the Garnaut Review, pointing out that the review’s discussion of the scale-up issues for renewables amounts to nothing more than a few throw-away lines and a lot of optimistic ‘technology development will solve these problems’ type statements otherwise lacking substantiation.

What do others think of the work of Trainer? The Energy Bulletin has done a review of his book, and concludes:

Trainer’s figures on renewables have been and will continue to be disputed. However, one thing is not in dispute. The move away from fossil fuels will be much much easier with some of the cultural changes that he describes as “The Simpler Way”.

I must admit I struggled to find many direct criticisms of Trainer’s calculations, either in the peer-reviewed literature or on the internet (though there is this from Barney Foran from Monash University), but if you can track them down I’d like to be alerted to them.

There are certainly a lot of technical papers which show how a distributed and diversified renewable energy grid can enhance the supply potential of renewables to near-baseload, but none that deal directly with the long-term storage problem that can lead to supply failure for short periods (e.g., large-scale renewables may be baseload for 25 days of every month and yet still fail to provide a reliable supply for the other 5-6 days, which would obviously create serious problems for today’s ‘always on the go’ society). Perhaps the critiques are there, and are able to show where Trainer has gone wrong — if so, please do alert me to them in the comments section below.

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Where do I stand on this? As BNC readers would know, I am strongly in favour of a massive rollout of renewable energy and energy efficiency. I think Trainer’s primer is superficial in its discussion of bioenergy because it focuses on the inadequacy of first-generation (crop-based) biofuels and doesn’t consider the potential of microalgal biodiesel or hydrogen-producing microbes (although his general point about a reliance on ‘future tech’ to make this stuff work is valid). His dismissal of nuclear is based on the limitations and wastefulness of Gen II LWR nuclear — he has not even considered Integral Fast Reactor (IFR) nuclear power (though I have since alerted Ted to this and he is looking into it, like we all are now!).

I would like to say Ted is being overly pessimistic about total delivery potential and the huge redundancy demands of large-scale renewables, but his stark calculations appear to be quite robust (alas). That says to me that whilst achieving a diversified renewable energy supply will remain a high priority, it will simply not be enough. If we are to close all coal-fired power stations within the next two decades, as is required, an IFR-type technology will have to be a large (perhaps primary) contributor to achieving this.

Otherwise, it’s back to a simpler way, either by design or inevitability.

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