Battery-powered cars get their energy from the grid
RANGE: A maximum of 500 km. RECHARGING: 1-12 hours. CHALLENGE: Short range and very long charging time. ADVANTAGE: Communicate with the future grid, so the power can be as cheap as possible.
YOU WALK OUT THE DOOR – ready for a day at work. You get into your battery-powered car, which monitored power prices during the night, only charging at low prices. Almost 100 % of the energy comes from renewable sources such as wind turbines and solar cells, which only generate electricity, when the sun is shining or it is windy, so prices fluctuate. Moment by moment, the car computer is updated on the electricity grid load.
If battery-powered cars become common in the future, they will probably be able to communicate with the electricity grid. The cars wil l form part of the power supply: “batteries on wheels”. When the grid is in surplus, car batteries are charged. When it is in deficit, cars go on driving, but the sparse electricity supply is used for more crucial purposes such as electricity in hospitals.
Batteries are win- win for society Leading car engineers would soon like to see the roads fill up with battery-powered cars. Financial analyses of the future indicate that up to one third of all the world’s cars might be battery-powered in 2040. For years, hybrid
cars – i.e. vehicles that are powered by a combination of batteries and fuel – have been emphasized as a temporary solution, until batteries will be good enough to be the only power source of electric cars. But in April 2017, a report showed that the sales of purely batterypowered cars in Europe are now rising as quickly as the sales of hybrid cars.
The advantages are obvious. First of all, the cars pollute extremely little, even considering the entire battery production. Secondly, battery-powered cars fit easily into the changeover to green energy types – unlike hydrogen cars, etc., they do not use a separate fuel, they must only be hooked up with the existing electricity grid.
Short range is a major problem
Paradoxically, the weak point of batterypowered cars is the battery itself. For decades, batteries have been too heavy, have taken too long to charge, and have had much too low energy density. In other words, batteries are too heavy as compared to how much energy they can include.
One of the world’s best battery packets is to be found in the Tesla Model S, which is also one of the most expensive battery-powered cars on the market. The battery takes up the entire bottom of the car and weighs about 550 kg (the total weight of the car is some 2,000 kg). Its maximum range is 482 km – much less than the approximately 1,000 km that modern petrolpowered cars can cover. And when it comes to cheaper battery-powered cars, the situation is even worse. A Nissan Leaf can cover a maximum of 170 km, before it must be recharged. Moreover, fuel cars even have the advantage that they can be filled up very quickly and anywhere, whereas a Tesla requires one of the company’s superchargers for a quick recharge. But even at a fast charge point, a full charge takes 1+ hour.
More energy in less space
Lithium batteries are one of the most common types of car batteries today, and in the past 10 years, scientists have steadily improved them. Basically, the batteries function by positively charged lithium ions passing between a negative and a positive pole, which are made up of two plates. Between the plates, you will find a separator enveloped in a liquid electrolyte solution – an ion-conducting liquid that allows the lithium ions to pass back and forth between the poles. The motion of the ions also makes the electrons in the battery’s poles stir, but as the separator prevents them from moving about the electrolyte liquid, they are diverted out of the battery to power the car’s electric engine.
The number of lithium ions that can move between the poles determines the battery’s capacity, and so, modern lithium batteries have not only one set of poles, but rather many layers of plate. Over the years, engineers have managed to pack ever more plates into less space, so lithium batteries have become flatter and come to include more energy. This has been particularly clear in smartphones, that are also powered by this battery type. However, scientists are reaching the upper limit of how closely plate, separators, and electrolyte liquid can be packed, so several battery experts are looking into a new type of battery, in which all layers are united in one material.
Today, the best lithium batteries’ energy density in the lab is a maximum of three megajoules per kg, but scientists hope to be able
to more than triple the number, when solidstate batteries enter the market. In this battery type, the electrolyte liquid has been replaced by a solid, ion-conducting material, which functions as both separator and conductor. Today, separators are about 20-30 micrometres thick, but with solid-state technology, it is possible to go as low as 3-4 micrometres. The solid electrolyte material also makes the battery more durable. A liquid electrolyte could overheat and make the entire battery burst into flames or even explode.
In 2017, Toyota declared that the company aims to install solid-state batteries in its battery-powered cars from 2020, and Fisker promises to follow suit in 2023. According to Fisker, its solid-state batteries can be charged in only one minute, i.e. just as quickly as filling up a car with petrol or diesel. Consequently, there is one less argument against replacing fuel by batteries.
If scientists and car engineers solve the battery challenges of space, range, and charging time, battery-powered cars could soon be charged on any street corner.