Reporting on promising developments in storage, delivery capability and cyclability
At a meeting in Paris on 12 December 2015, 195 countries adopted a climate agreement with the long-term goal of keeping global warming to a level “well below 2°C”. To achieve this, the countries undertook to “rapidly reduce their greenhouse gas emissions”. This agreement implies a complete rethinking of global energy production, bearing in mind that it is still largely dependent on fossil fuels, including coal and oil.
However, the latest Statistical Review of World Energy published by oil company BP shows that since 2015, total consumption (in tonnes oil equivalent) of coal, oil and natural gas rose by 0.97% in 2016 and by 1.02% in 2017 (-0.98%, 1.82% and 2.88% in 2016 and 0.69%, 1.42% and 2.69% in 2017 respectively). This runs contrary to what could have been legitimately expected. This regrettable observation raises the thorny question of how the Paris Agreement objectives are to be met.
The issue is all the more pressing in that recent studies have shown that climate destabilisation could be subject to an irreversible chain reaction process; in this scenario, a rise in temperatures above a certain threshold, as yet not precisely defined (perhaps in the region of 2°C), would lead to the accelerated melting of the permafrost in glacial regions (including Siberia); the greenhouse gases it contains (CO2 and methane) would be released into the atmosphere, further intensifying global warming through a process as yet not properly understood; this process would result in non-linear change, in fits and starts. It is therefore becoming vital to avoid such tipping points, triggering such fits and starts shocks.
In this worrying context, the development of renewable energy (solar and wind) is essential. However, these forms of energy are irregular and unstable. One of the challenges that scientific research must quickly resolve is how to store the electricity they produce when conditions are favourable more efficiently and more economically for use when conditions are less favourable.
Hoped-for innovations in this field could be accompanied by the accelerated deployment of installations to produce such forms of renewable energy. The scale of the undertaking is huge! As a study by the Carnegie Institute has shown, for example, the installation of an offshore wind farm in the North Atlantic over an area the size of India could provide humanity with all the energy it consumes.
Various ways of storing energy already exist. Surplus electricity can, for example, be used to move water from a low reservoir to a high reservoir or to electrolyse water with hydrogen and oxygen, which can then be burned or used in a fuel cell, or to compress gases (such as nitrogen) to their liquefaction point. One major area of development will, however, be that of rechargeable batteries.
A few points to bear in mind: a battery is composed of a cathode to reduce the metals and an anode to oxidise the metals. These electrodes are impregnated with a conducting electrolyte to enable the flow of ions. Batteries are rated in terms of their electric tension, expressed in volts (this is the difference in electric potential between the two electrodes) and by their capacity, expressed in coulombs or ampere hours (Ah). The specific energy, expressed in mAh/g, is the product of the voltage and the capacity and represents the amount of energy the battery can deliver per unit of mass (or volume), from a completely charged state to a completed discharged state. A battery’s lifespan is estimated by its ‘cyclability’, i.e. the number of charge/discharge cycles it can withstand. The nature of the chemical components and materials used determine the level of these variables.
Currently, lithium-Ion (Li-Ion) batteries are the most cutting-edge type; compared to other types of batteries currently available, they have one of the best specific energies and one of the lowest rates of discharge when not in use; research is ongoing to enhance their performance in terms of both specific energy and cyclability. The most sophisticated types, used in electric cars, could recharge in six minutes, providing 320 km of autonomy.
However, elements such as cobalt (one of the components used as a support matrix in the batteries) and lithium are costly and recycling Li-Ion batteries poses a number of problems, not only technical, but also ecological, due to the toxicity of the metals they contain. This is why other avenues are being explored and should offer more economic, denser, lighter and more powerful electrochemical systems in the years to come.
Three new battery technologies are particularly worth mentioning at this time.
A. sodium-Ion batteries
B. lithium-sulphur batteries
C. ‘all-solid-state’ batteries
Environmental fund specialists at BNP Paribas Asset Management are closely monitoring the various developments in this niche sector to be in a position to invest in those companies with the best future prospects.