Renewable energy comes in inconsistent amounts. It’s available when the sun is high and clear (or sometimes even cloudy), and it’s available when the wind blows (which it often does during certain periods of the day). In order to use this variable power reliably, we need reliable storage solutions overnight or during periods of low generation (like early morning or late evening). Yet most renewable energy projects require a stable electrical grid that works all the time, especially during peak demand periods.
A crucial component of renewable energy storage is the battery. Years ago, researchers thought the bioelectrical potential of a human (say, from touching a badger) could be harnessed using an electric eel as part of an electrochemical cell. This was not meant to be taken literally – it was meant to illustrate just how essential batteries are in powering various applications toward the delivery of clean power and how scalable they are.
The Battery Industry Research Council forecasts that by 2030 lithium-ion batteries will account for nearly 70 percent of smart grid battery systems, supplies that will handle up to 12 hours of off-peak electricity demand.
The renewable energy landscape benefits greatly from a variety of energy storage solutions that complement traditional batteries. Pumped hydroelectric storage represents one tried-and-true method in this space, using water held in two different elevation locations as part of its operating cycle. When there is excess electricity on the grid, such as when wind turbines are spinning or solar panels are producing power during peak sunlight hours, water is pumped to an upper reservoir—essentially uphill. This “storing” of electricity allows for several advantages over other types of electrical generation and/or consumption scenarios.
1. The amount of water stored does not have to be handled like a gas; so it doesn’t have to be compressed like natural gas (which requires 536 times more gas to produce the same amount of energy as hydropower), transported through pipes like synthetic liquefied natural gas (a big reason why “natural” gas isn’t nearly as “green” as we’ve been led to believe), or stockpiled in landfills (as happened with the electric power world’s first choices: wood and coal). Water does a great job representing stored physical force without going anaerobic or emitting CO2.
The renewable energy storage market is largely a lithium-ion battery market. That’s because lithium-ion batteries offer much more energy density than any other kind of rechargeable battery and, therefore, are vastly versatile and easily applicable to many different situations in which you might want to use a stored-energy solution – from the electric vehicles of yesterday (and tomorrow) to grid-scale applications where they’re used in conjunction with wind turbines or solar panels to create a kind of recurrent charger for the electrical grid.
So, if you were wondering what kinds of advancements have been made at the level of chemical mechanics, that really should be the stuff physics labs should ideally be working on as part of some secret project. Instead, it seems like something that happened in public over 1-2 years and is now sort of a fait accompli: researchers replaced graphite with silicon; they increased battery capacity; they reduced charging times; and most significantly, though lesser-known – refundable health insurance policy for factory workers who use dangerous materials, including embryotoxic lithothiazide yellow dyes (that aren’t toxic when you’re using them in safe conditions), high-pressure air-dried nitriles (like cyclonite), etc., following a discovery by scientists mostly working for A123 Systems (a spinoff from MIT).
Looking beyond lithium-ion, several up-and-coming battery technologies hold potential. One is the solid-state battery. In this type of battery, rather than using a liquid electrolyte, a fragile, moisture-sensitive component that can lead to unpredictable and sometimes catastrophic failures—an electric vehicle could use a “solid” (i.e., gel or ceramic) electrolyte—meaning advancements in those materials should also improve the overall safety of an EV.
Another exciting technology is flow batteries. These don’t use messy batteries submerged in salty pools of water but instead employ liquid electrolytes stored in external tanks; if more capacity is needed, you simply provide more tanks. They’re scalable and work well with renewable energies capable of delivering variable amounts of power into the grid.—Zara Prendergast-Mason
Current research in high-energy-density materials is very promising for future batteries, particularly lithium-sulfur batteries. These offer the potential for a massive increase in energy density and are generally considered a more environmentally friendly technology than current battery technologies relying on cobalt, nickel, or other metals that have unfortunate byproducts, like child labor and forced labor conditions that mar the production of these latter minerals.
Graphene can be used to enhance battery performance through its conductivity and large surface area. At present, most of graphene’s applications exist mostly in concept-stage ideas where companies hope to use this ultra-high-performance material to change the world a common refrain from many materials science stories over the past few years ideas that often result in upsetting expectations when they fail.
Innovative storage systems existent today provide cutting-edge mechanical solutions for storing renewable energy. One such system is pumped hydro storage. It uses two water reservoirs and converts electricity into mechanical energy, which can then be converted back when needed (Dolgopolov et al., 2015). When there’s a surplus of electrical power, water from one reservoir is pumped to the other: to an upper reservoir when the electricity comes from renewables like wind or solar power, and back down to the lower storage reservoir during periods of high demand (erosb.com).
Another invention that accomplishes similar tasks with innovative design and materials is compressed air energy storage (CAES). In its most basic form, CAES accomplishes what we’ve so far seen as the only way around: using stored electricity released by turbines in a very efficient generator.
Innovations in chemical storage have the potential to enable large-scale energy storage. Hydrogen can be generated using electrolysis, and then either used directly (in fuel cells, for example) or converted back into electricity. Similarly, when it comes to ammonia as a means of storing electrical energy, one can envision a future in which gas turbines use the plentiful supplies of ammonia available from agricultural overruns to generate electricity when needed most—an ideal way of handling the variability in wind and solar power production rates. Ammonia can either be used directly as fuel or reconverted into hydrogen and then used in an electric power plant.
As far as metal-air batteries go, they are quick to “discharge” (a nice change from lithium-ion technology that tends to produce questionable disposal scenarios for the metals they use), to storable form.
The cost of battery systems, such as lithium-ion and lithium-iron phosphate, can be high. Installation often requires some digging and excavation to lay down the required amount of cables and inverters—a job that demands significant quantities of dirt and dust. And construction itself appears not to have a first-cost incentive: federal policies are critical to this market, enabling broad adoption through policies like the Production Tax Credit (PTC), which provides an average incentive of about 2.4 cents per watt for wind energy generation, or incentives provided under the Energy Act, which give manufacturers roughly $51 billion worth of incentives over 10 years—though those amounts do ascertain that we’re coming closer to cost-effectiveness than previous markets for other clean technologies. But don’t be discouraged! Similarly priced costs in previous clean tech markets didn’t prohibit broader adoption either—look at solar panel prices compared to five years ago!
