An s-curve model for deployment of new energy technologies based on analysis of past rates of technology deployment was published over five years ago [i]. It showed that new technologies typically start with a period of exponential growth, increasing by about an order of magnitude per decade. When technologies reach around 1% of world energy supply their growth becomes more slower in percentage terms (though not necessarily linear). The post exponential rate of growth and the saturation point for each technology on its s-curve are less clearly defined.
A wide variety of energy technologies conform well to this model (see chart), because it takes a few decades to build the scale of industry necessary to provide 1% of the world’s energy, then long replacement cycles in the energy sector (typically 20-40 years) and competition with incumbent infrastructure limit the rate of further growth.
The projections have held up well for solar and wind, with the triangles on the chart showing the actual likely to be produced in 2015. CCS has been much slower to develop, and is likely to fall further behind projections for 2025 given the current rate of project development.
Source: Kramer,GJ and Haigh,M. No quick switch to low-carbon energy, Nature Vol462, 2009
The model implies that groups of technologies still in the early phases of deployment, including CCS, concentrated solar thermal power, geothermal, and large scale electricity storage technologies will take several decades to reach very large scale. They will thus probably only be in a position to make a really large contribution to emissions abatement towards the middle of this century (if at all). For example the rate of CCS growth shown the deployment chart above already seems highly optimistic. (For some reason CCS seems to have been plotted as energy in rather than electricity out, so if the line for CCS reached the same annual energy as solar or wind it would still be generating only about a third as much electricity.)
This emphasises the importance of deployment of those technologies that are already at scale (wind, solar and nuclear). Continuing improvements in energy efficiency (despite rebound effects) and the use of natural gas in power generation also have an important role to play in emissions reductions pathways. And of course the sooner the scale-up of early-stage technologies such CCS begins the earlier they will be able to make a very large contribution, so starting now remains very valuable.
There are couple of important caveats to this analysis. While the authors refer to the patterns as “laws” they are observed regularities rather than absolute constraints. Some technologies have particular factors associated with their deployment not captured by the model. For example, the reduced rate of growth of nuclear from the mid-1980s was driven by a particular confluence of political and economic factors, and its future growth is similarly subject to political and economic constraints in many places, although it is favoured in others. It also does not go back far enough to show all of the very rapid increase in oil use in the two decades after the end of the second world war.
More recently, Solar PV has been growing much more rapidly than the model suggests, with quite different supply side characteristics to other energy technologies, being much more scalable. Energy efficiency technologies also have different characteristics, as the authors of the modelling work acknowledge. Other demand side technologies such as electric vehicles seem also seem likely to be able to scale up somewhat more rapidly than these projections suggest. And while some storage technologies might take time to reach scale lithium ion batteries seem likely to be able to grow very rapidly as there production is also scalable, although there may be some supply chain constraints that may partially limit this. These imply potentially different prospects for deployment in these cases.
In view of the time required to build scale in new technologies, few energy policies seem more important than those that encourage continuing reductions in costs and increases in the rate of deployment of technologies already at scale, including wind and solar PV, along with continuing improvements in energy efficiency.
Updated 8th December 2015
[i] Kramer,GJ and Haigh,M. No quick switch to low-carbon energy, Nature Vol462, December 2009