The International Energy Agency (IEA) publishes a biennial report on the prospective energy technologies and its 2014 edition is devoted to the potential of electricity by 2050 (IEA, Energy Technology Perspectives 2014, Harnessing electricity potential, www.iea.org ). Electricity production sectors are indeed important to the extent that, according to the IEA, electricity represents, presently, 40% of the world primary energy and 40% of CO2 emissions and it is assumed that electricity demand will grow in the coming decades. The objective of national energy policies is to move gradually to a « low carbon » power generation, this objective being the center of the energy bill which is being discussed, presently, by the parliament in France. In its report, the IEA assesses recent developments in power generation and its consumption in major sectors of the global economy. This assessment does not encourage optimism : – the carbon intensity of energy fell by only by 1% in 40 years – the technologies for « clean » coal are not really used (CO2 capture and underground storage) – onshore wind energy is mature (but not off-shore) but renewables are emerging slowly (but strongly in Asia) – the Fukushima disaster has disrupted the « renaissance » of nuclear power – the rise of electric vehicles global sales is rather slow (though with a strong increase in 2013). Most energy scenarios for 2050, especially those of the IEA, are considering a sharp rise in electricity demand : demand growth will be in the range of 80 to 130% and according to its most proactive scenario, limiting climate warming to 2 ° C, the share of renewables in electricity generation will increase from 20% in 2012 to 60% in 2050. Let us recall that in the energy bill which is being discussed in France that share would reach 40% in 2030.
In its report the IEA addresses specifically six technical-economic issues. Some important facts emerge from these views. The main one being, probably, that the IEA proactive climate scenario – where renewables would take the top spot in power generation – « expects » that solar energy could be the dominant electricity production sector globally (photovoltaic electricity and concentrated solar power). IEA also assumes that natural gas used in turbines whose performance are now very high (50-55 %) should facilitate the energy transition accompanying the rise of intermittent renewables. The electrification of ground transportation is a third important perspective to the IEA, meanwhile it can only be realized if power is available at a reasonable cost and if battery storage with their charging infrastructures are available in good conditions. The IEA report highlights several technical and economic obstacles which might block the energy transition. It noted in particular that the storage of electricity is a key point for the power system of the future (99% of electricity storage being provided in the world today by hydraulic pumping facilities). For nearly ten years, the IEA made a plea for the separation and storage of CO2 from power plants – they would continue to use fossil fuels (natural gas and coal) for power generation – these techniques are still being tested and will really take off if CO2 is taxed. The IEA also draws attention to the need for a carbon tax at a significant level to encourage the take-off of renewable energy sectors and the nuclear revival that would fund the non-carbon energy as well as raising substantial funding for energy R & D.
This new IEA report has the merit to highlight the complexity of the technical system that will have to be implemented to exploit the potential of electricity. IEA’s has great hopes regarding solar energy – it would be the main electricity production sector industry in 2050 – although it is not considering alternative to silicon for photovoltaic electricity. In general, IEA does not really make any assumption about any technical breakthroughs that could change production techniques to a more or less near horizon. However, it makes some assumptions about the production costs of electricity which are an important parameter for its future. It should also be observed that the IEA does not mention the sociological aspects of the rise of electricity: consumer behavior, hostility to nuclear or underground storage of CO2, etc. According to the IEA, accelerated electrification is somehow the « driving force » of the overall global energy system. Without going into detail on our previous analyzes, particularly those on the energy law draft in France, it should be remembered that strong obstacles still block the access to a « carbon-free » electricity highway.
Let us just make a few observations. If onshore wind can be considered, presently, as mature, it is far from being the case for solar technologies (photovoltaic and concentrated). Hence the urgent need for R&D investments on new materials for photovoltaic cells. Chemists have thus proposed, recently, a new solution with an organometallic semiconductor pertaining to the perovskite family materials (in general these are metal oxides), this hybrid materials consisting of an halogen (chlorine, bromine or iodine) methylammonium and a metal such as lead or tin prepared by vapor deposition on a solid substrate (a glass for example). The conversion efficiency of these cells is, at present, 18% with a voltage higher than that of silicon. This new material is currently being tested, in order to ensure the solar cell stability, it has the advantage of being easy to use, possibly in tandem with silicon because it does not absorb the same photons (cf. M. Grätzel « The light and shade of perovskite solar cells, » Nature Materials, 13, p. 838, 2014, www.nature.com/natmat) and it is produced at rather low temperature (~ 100° C far lower than silicon production which is more energy consuming). Electricity storage is another obstacle to be blown out if we want to develop renewable energy and electric cars, and it is clear that in the field of batteries progress is very slow. The energy density of lithium-ion batteries, the mostefficient, is still insufficient (~ 150 Wh/ kg) and other options are being considered, for example with lithium-air batteries, or with electrodes in lithium oxides or magnesium.
Will electricity be the driving force of the future energy system, as the IEA believes? This scenario is credible only if national energy policies (and that of the European Union) admit one hand the need for a tax on CO2 emissions and on the other hand taking seriously into account the need of significant R & D long term programs on most non-carbon energy systems.