Saturday, July 1, 2017

US '100% renewable by 2050' scenario 'unreliable'

In 2015, Stanford University Prof. Mark Jacobson and his colleagues, in a paper in the Proceedings of the National Academy of Sciences, argued that between 2050 and 2055, the United States could be entirely powered by ‘clean’ energy sources (wind, solar and water power) and ‘no natural gas, biofuels, nuclear power, or stationary batteries are needed.’
However, a group of 21 researchers have now published a study in the same journal arguing that the work ‘used invalid modeling tools, contained modeling errors, and made implausible and inadequately supported assumptions’.
They say that ‘The study’s numerous shortcomings and errors render it unreliable as a guide about the likely cost, technical reliability, or feasibility of a 100% wind, solar, and hydroelectric power system. It is one thing to explore the potential use of technologies in a clearly caveated hypothetical analysis; it is quite another to claim that a model using these technologies at an unprecedented scale conclusively shows the feasibility and reliability of the modeled energy system implemented by midcentury.’
Crucially they say it ‘does not provide credible evidence for rejecting the conclusions of previous analyses that point to the benefits of considering a broad portfolio of energy system options. A policy prescription that overpromises on the benefits of relying on a narrower portfolio of technologies options could be counterproductive, seriously impeding the move to a cost-effective decarbonized energy system’.
The authors of the critique include Dr Ken Caldeira, who, in 2103, along with others, famously wrote an open letter to environmentalist asking them to back nuclear power- an option Jacobson et al treat with distain. The authors of the critique say that the inclusion of nuclear and CCS, as well as biomass/BECCS (which Jacobson et al also avoid), alongside renewables, would allow US power to be 80% carbon free. Jacobson has replied to the critique which he says is ‘demonstrably false’ and ‘riddled with errors’ e.g. nuclear & CCS wouldn’t help balance variable renewables and would push up costs. He also sees it as too focused on carbon saving. His approach was broader, e.g. also looking at air pollution health impacts, energy security and nuclear risks:  and
The debate continues: and  It is not just an academic debate; it touches key strategic issues for the US and the rest of us. Jacobson’s team had also earlier developed a global version, published in Energy Policy, and more recently, with a team of 27 or so, has been working on an upgraded version covering 139 countries in detail, with variable supply and demand balancing carefully addressed : These 100% scenarios suggest that there is no need for nuclear or carbon storage fixes- there are sufficient renewables of various types to supply all global energy needs - and soon. Given that Jacobson excludes (most) biomass, that is certainly provocative. Most other ‘high renewables’ global and national scenarios include biomass and many of them only look to 80-90% renewable electricity contributions by 2050.  However, Jacobson’s work and some of the other earlier studies like that by WWF, in effect set the benchmark high and the studies that have followed do seem to be gradually filling out the expectations. For example, in a joint report with the IEA, which says ‘near 70%’ may be possible, IRENA looks to renewables supplying 82% of global electricity by 2050:
Indeed, some have now gone even further.  Lappeenranta University of Technology (LUT) in Finland, has produced very ambitious EU and NE Asian studies of renewable potentials, with hourly balancing and supergrid links:  and
And it says 100% of power by 2030 globally is technically viable and affordable.
100% by 2030 would certainly be pushing it!  And their analysis has attracted some criticism- see the initial links to the critiques by Energy Matters in this riposte from LUT:          
The detailed technical debate over whether the numbers add up or not will no doubt continue, and is valuable, but to some extent it misses the strategic point.  What has been achieved is that the debate is no longer couched in terms of whether renewable can make contribution or not, but on the scale of that contribution. Now we are debating whether it will or should be near 70% of global power (IEA) or above 80% (IRENA) by 2050. Or even more.
Time was when it was common for renewables to be almost totally dismissed and trivial, irrelevant and foolish. Even now we are treated to the selected use of data to minimise their significance. Thus the new BP World Energy Outlook says renewables, excluding hydro, only supplied under 4% of energy globally in 2016. That figure is for primary energy, which BP calculates in terms of the tonnes of oil that would have be burnt in a power plant to give the same energy output, even if it’s actually wind or solar generated energy being used. So, for comparisons sake, they say the raw plant output data is ‘converted on the basis of thermal equivalence assuming 38% conversion efficiency in a modern thermal power station’.
However, that’s an unfair comparison: unlike fossil or nuclear-fired steam-raising plants, wind and solar plants don’t suffer from 62% thermodynamic energy conversion losses. It’s also not a very useful comparison- what matters for these systems is the energy delivered to users. On that basis, REN 21 calculates that renewables, excluding hydro, accounted for around 6.6% of final energy uses in 2015, or 19.3% including hydro. While nuclear comes out at 2.3%:
You can play with the figures in other ways too.  REN21 says that renewables, including hydro, supplied 24.5% of global electricity in 2016, with wind supplying 4%. But reverting to the use of primary energy, Matt Ridley manages to render the wind statistic as in effect zero, ‘to the nearest whole number’, since the IEA say it was 0.46% of total energy in 2014!  
Leaving these tiresome number games aside, there are some more important issues. Renewables like wind and solar deliver variable outputs, so that has to be taken into account. Sadly, that too can lead to some confusion, willful or otherwise. Those hostile to renewables sometimes say the backup needed will be prohibitively expensive. But the most recent analysis has put the extra cost at around 10% for moderate renewable contributions. And that ignores the possible cash and health cost savings from not using fossil fuel. As IRENA has commented reducing the impact on human health and mitigating climate change would save between two- and six- times more than the costs of decarbonisation’.

Scenarios are helpful to harden up estimates like that, but the overall direction of travel should be clear- with renewables playing a central role.  Within that there are choices to be made- do we include biomass. Large hydro? Do we focus on small scale systems or accept some large systems?  Scenarios can help assess the likely energy system impacts of these and other options, and may also be used to identify the scale of any wider impacts, but in the end it’s a matter of strategic choice based on assessments of likely costs and benefits, risks and obstacles. A system based on a wide range of renewables of various scales and types seems likely to be more robust and sustainable than one based mainly on large probably costly and possibly inflexible nuclear plants coupled perhaps with CCS as a fix for continued interim fossil fuel use, and it may be possible to model that to see if it is true. But in reality, while scenarios and debates over them can help, if done without too much rancor, we still have to make decisions based on future outcomes which can’t be fully modeled.  

1 comment: