Electricity generation from renewable sources like wind turbines and solar farms is only half of the fossil-free energy future. The other half consists of the necessary storage for “fidget current” and inevitable “dark doldrums.”
The discussion about replacing fossil and nuclear fuels in energy production revolve primarily around producing electricity from renewable sources: hydroelectric power, wind turbines, and photovoltaic systems. Fossil fuels had the advantage that electricity was generated when needed. Storing electricity was only necessary to a limited extent: to provide our electronic devices with rechargeable batteries or to enable electric mobility by bike or car.
However, renewable electricity production to supply the electricity grid is not possible in the long term without large storage systems. “Dunkelflaute” (dark doldrums) and “Zappelstrom” (fidgety power) are German keywords that, like “kindergarten” and “waldsterben,” have already found their way into the English language. Dark doldrums refer to times without wind and when wind turbines and their generators stand still, and night and cloudy weather turn off the sun for solar systems. Because dark doldrums make electricity from renewable sources unpredictable, these sources are now somewhat condescendingly referred to in the discussion as fidget power.
Energy storage – mainly in the form of rechargeable batteries – must therefore bridge periods of dark doldrums. What can already lead to minor personal crises at the end of the day with our smartphones and deters many potential buyers of e-cars is unthinkable for power grids: At present, thermal power plants, in particular, whether operated with fossil or nuclear fuels, have to bridge the fluctuations in the fidget current.
Therefore, efficient and cost-effective electricity storage is indispensable for a future based on renewable energy. In addition to technical challenges to improve energy density, they bring new environmental pollution. The currently standard lithium-ion batteries need vast amounts of lithium and cobalt, the mining of which is highly problematic in terms of ecological destruction and human rights violations in the countries of origin.
No (problematic) metal needed
A new type of battery, developed by two professors from the renowned MIT (Massachusetts Institute of Technology) and the Boston startup PolyJoule, uses no metals to store electricity. Instead of lithium or other metals, PolyJoule uses electrically conductive polymers for its batteries – plastic at the core. The conductive polymers replace lithium or lead used in other batteries. Since this plastic is readily available, it would no longer depend on previous sources of raw materials.
PolyJoule’s plastic batteries exhibit several properties essential for power storage, writes MIT Technology Review. The batteries charge very quickly and can keep the stored electricity for a long time. Due to their high efficiency, little current is lost during charging. The processed plastic is inexpensive to produce. Because the plastic is robust, it doesn’t expand to shrink when loading and unloading. With conventional batteries, this can cause several problems.
The most significant disadvantage is the low energy density of plastic batteries. The cell of a plastic battery is up to five times larger than that of a lithium-ion battery of comparable capacity. That is why PolyJoule sees the application primarily in the stationary sector, not the mobility sector. On the other hand, they are particularly well suited for power grids since the plastic batteries cannot overheat. Therefore, separate cooling and control systems to prevent overheating and possible fire are unnecessary.