Renewable energy can’t work without batteries and other tales of energy storage.

Batteries. You know what they look like. You know what they do. But their biggest challenge yet is making renewable energy cover days at a time rather than just sunny and/or windy hours. And without the capacity to store the energy from solar during the day and wind when it’s not blowing, those power sources are only useful for specific times of the day. And with the way the power grid works, you might have to turn off the solar panels or wind farms to avoid overloading it if supply is higher than demand for power. Pushing peak supply to even out in times of low supply is called load-shifting.

Photo by mohamed Abdelgaffar from Pexels

And yet, battery storage, from Tesla/SolarCity’s industrial storage units in Australia to the ones in your newest electric car, is both the hot item of the decade and a pain to properly implement. It’s at that awkward point technologies get to, where the vision is there but the research and commercially viable option just haven’t come of age yet. But with renewables catching up fossil fuel energy production fast, the power grid needs storage to make use of solar when it’s cloudy and wind when it’s dead still. Even more important given the sheer amount of power they produce are hydroelectric dams. Their supply changes based on whether it’s a dry or wet season and evening out is crucial. This is called load-shifting.

Pushing water up a hill then letting it go back down.

Say you’re producing a lot of energy and it’s not being used — this can actually mess up the balance on the grid if supply is too high and crash it. What do you do with that surplus?

Sure, you could turn off the solar panels and just sink that cost…. Or you try and store that excess power to make up the cost.

For the purposes of this post, storage isn’t just chemical (your AAA batteries) but also mechanical. What is mechanical storage? Think of a water reservoir at the bottom of a mountain. The simplest way to do this is pump water up a hill or mountain and when the surplus supply stops, you release the water and power a turbine, giving you back that power when you need it. This is called pumped storage and for such a simple solution (dating back to Roman times), it gets remarkably little attention, despite making up 95% of the world’s storage capacity in 2016.

Unlike chemical batteries, there’s little technology that needs to be developed and can be built right away, assuming you have a hill, a reservoir and a turbine. (connection to power grid not included).

Photo by Ali Madad Sakhirani from Pexels

What if there’s no hills around? Think the vast North American plains, the flatlands of north-eastern Europe or the seas themselves where off-shore wind farms are built.

There’s rarely, if ever, any steep hills and reservoirs by the coast, where they feed their produced power into the grid.

So you want some device to store that power, that can be deployed anywhere — on coasts, flatlands, hills and remote islands. Batteries are where it’s at.

The history bit.

Looking at the history of batteries you might be thinking it started with the first chemical battery created by that Italian jack-of-all-trades, Alessandro Volta, back in 1799. The unit for electric potential, the volt, is named in his honour. (Fun fact — he’s also credited as the discoverer of the gas methane) But if you look at the underlying principle of battery storage, the first battery is far older. Just before WW2, a clay container was discovered near Baghdad, containing what’s described as one of the earliest electro-chemical batteries. It’d been dated to around 200 BC.

But batteries have been more of an experimental plaything rather than an invention with clear applications for most of their history. It was only with the advent of the first cars requiring an electric start that the modern battery (in its lead-acid form) became commonplace. By that definition, the modern battery started in 1859.

But the next step in the technology, that is to increase capacity and reduce cost, requires both a re-think of the chemistry of batteries and the economics to make them effective at reducing the final user cost of electricity.

How do they work?

Battery is a catch-all term for a device that converts chemical energy into electricity. This is done by having two metals or compounds separated by a porous insulator and making the energy potential difference release electrons from one of the compounds — this electrical current is then harnessed. The compound that loses energy is the anode and the compound that gains energy is the cathode. The mix of metals or compounds is what gives each type of battery its name: lead-acid in car batteries, mercury in watches, alkaline dry-cell (this is the AA, AAA and so on batteries), lithium-ion in modern laptops/phones/gadgets, nickel-metal-hydride for first-generation electric and hybrid cars and nickel-cadmium for pre-2000 laptops. There’s more types but these are broadly the most used ones.

What’s wrong with current batteries?

However, while lithium-ion and its more advanced but also more expensive sibling, lithium-ion polymer, are the most common batteries at the moment, they are reaching a plateau in terms of improvements and cost savings meaning they’re alright for battery storage but unlikely to become better according to the S-curve. The Technology S-curve suggests these battery chemistries have reached a plateau at the top of the S and newer technologies might be required. However, Tesla and Panasonic have built the Gigafactory in Nevada and a lot of Tesla’s business model relies on lowering costs for lithium-ion further still. This assumes lithium-ion is at the ‘Change of Paradigm’ stage of the Technology S-curve (see references below).

Li-Ion batteries found in most phones today. — Photo by Tyler Lastovich from Pexels

The three key properties of batteries for use in renewable energy storage are rechargeability, loss of charge over time and speed of discharge.

Rechargeability is essential. Without it, you’ve just built a one-time-use store and very expensive paperweight afterwards. Alkaline dry-cells can’t be recharged due to the way the dry paste inside changes as it’s discharged, but alkaline rechargeable batteries have become much more common in the last couple of years.

All batteries lose some charge over time due to the many cycles of chemical changes inside (this is why your iPhone loses charge over the two-ish years it’s designed to last). However, depending on the use and planned longevity, different batteries might be best. This is why we hear about new batteries that are paper thin and can store a thousand times what you have in your mobile phone now every other news cycle but if you dig deeper, they’ll have a fatal flaw disqualifying them from phones or cars: either they discharge too slow (you need a pretty big continuous flow for big stuff like cars) or they lose charge too quickly if unused (even if left charged).

Speed of discharge is also crucial for load-shifting.

While there are other factors, like Depth of Discharge (how much of the battery you should leave still charged when emptying it to avoid shortening its lifecycle, typically the last 10% should be untouched), Round-Trip efficiency (how much more energy does it take to store than what you take out) and battery lifespan or warranty, there are already commercially viable batteries at the edge of current technology that allow daily cycling of power from solar plants and wind farms.

The next generation

Proposed chemistries include zinc-air (technical challenges of air cathodes not yet overcome), solid-state lithium-ion (the concept is far from new and seemingly two or three years from widespread deployment in laptops, cars etc.), lithium-sulphur (also technically mature, expected just after solid state Li-ion), and lithium-oxygen (the most distant of them all, technologically).

The economics of batteries are ever-improving with more money flowing into bigger manufacturing plants and more demand year by year from both electric vehicles and storage facilities. Just in 2017, the 100 MW battery installed in Australia by Tesla was poised to smooth supply in the Australian state plagued by power cuts and black-outs and in Hawaii, the same company (whether for PR or for good business as well) is bidding to build a humongous 810 MWh-capable facility.

Notice the Wh is watt-hours (meaning 1 Wh is one watt released over an hour) whereas 1 W is a power measurement.

Where does that leave batteries?

The International Renewable Energy Agency estimates the world will need about 270 GW of battery storage capacity by 2030 to meet its renewable energy goals (45% of energy consumption). It already has 127 GW of pumped storage and another 55 GW of battery and other means (latest data I found was from 2017). The good news is predictions estimate we’ll match the required amounts and then some at the rate new installations are going. What’s more, the cost of battery storage is going down at about 7% per annum due to technological advances and economies of scale.

In all likelihood, we seem to be on a promising track. And both the renewable energy and the battery storage industries are looking very profitable in the years to come. Now all we have to think about is what do we do with the consequences of mining all that lithium in Chile and then disposing of it in 10–20 years’ time when they come offline. I’m pretty optimistic about batteries but I’ll leave you with my latest discovery : Solarpunk.

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