The mere concept of an electric car may well be an affront to those of us who worship at the altar of internal combustion, but the concept of electric cars is nothing new. Tesla may be the company that brought electric cars into the limelight in the 21st century, but the history of electric cars goes back much further than most people realize. The first fully electric cars were built in the second half of the 19th century in England and Germany, enabled by the invention of the rechargeable lead acid battery by French physicist Gaston Planté. In fact, by the turn of the 20th century (1900) there were more electric vehicles on American roads than petrol vehicles. But as internal combustion engines (ICEs) improved they became the preferred choice of propulsion for all types of vehicles. Battery technology simply couldn’t compete with the range and quick refueling of fossil fuel powered vehicles which in turn drove (pardon the pun) large investments into fossil fuel infrastructure which widened the gap again. ICEs still maintain this advantage to an extent today. Electric cars, by definition can be any car that uses an electric motor as its primary propulsion method. This can include plug-in hybrids, regular hybrids, fuel cell vehicles and battery electric vehicles (BEV). The most common usage of the term “Electric Car” is for the latter category, cars that use one or more battery packs as the energy source and one or more electric motors for propulsion, no engines, no fuel cells.
Electric cars are definitely high on the buzzword pecking order and they have a lot of advantages over ICEs and will probably be the future in terms of transportation energy sources. But they also have quite a few challenges that need to be addressed if they are to usurp fossil fuels as the predominant transportation energy source of choice. For this article we’ll be discussing a few things that all electric cars have in common and what some of the challenges facing wider adoption of EVs.
The most important part of any EV. ICEs work by converting the chemical energy in petrol or diesel into heat (through combustion) and then that heat is used to create mechanical motion through the pistons, conrods and crankshafts which propel the car. Batteries on the other hand, store energy chemically as well but instead of releasing that energy through combustion, that energy can be released in a controlled manner through charged particle movement between segments of the battery creating electricity which is then used to drive a motor etc. It is important to note that batteries DO NOT store energy as electrical charge but rather as chemical energy that can directly be converted to electricity. The earliest electric cars in the late 19th century used lead acid batteries, much like the ones you have in your engine bays right now, as a power source. With advancements in the lead acid battery, such as rechargability, there were quite a few electric vehicles happily running about cities in Europe and the US. The downsides to that were that the packs were heavy and the lead used in their manufacture was toxic. Modern electric cars have shifted almost exclusively to Lithium-ion-polymer (LiPO) batteries, as the ones found in the Tesla Model S and Nissan Leaf. The Toyota Prius, the world’s best-selling Hybrid uses older Nickle-metal-hydride (NiMH) batteries, but will most likely switch over to LiPO batteries for the upcoming generation. LiPO is the same type of battery you’d find in a laptop or cellphone and currently represents the state-of-the-art in battery technology.
Comparison of different energy sources with respect to energy, volume and weight. Courtesy US Energy Information Administration
The problem with modern batteries is energy density. Even the most sophisticated batteries are not even close to matching the energy density of petrol or diesel. This is a problem since the battery packs must become larger and therefore more complex and expensive, to match a given range for a petrol vehicle. This in turn will make the vehicle heavier which will require a larger battery all over again.
Petrol contains approximately 44.4 MJ of energy per kilogram of fuel and the latest LiPO batteries can barely manage 0.875 MJ/kg. This means that even if you were to assume that an ICE vehicle would have a 20%-30% efficiency compared to 90%-95% efficiency for an electric vehicle, there would still be an order of magnitude (10X) difference in energy density. This is one of the most fundamental problems holding back larger EV adoption. Going on a trip in an ICE car is a non-issue, just fill up the tank when it runs low. With an EV things aren’t so easy. From a Sri Lankan context though, where distances are short and speeds slow, EVs really do make sense from a practicality standpoint. Moving slowly in stop and go traffic is where EVs can really shine, where maximum use is made of regen braking as well as the fact that no energy is expended while the car is stationary (other than perhaps the A/C compressor). If you already have Solar Panels at your house that could make the investment even more sound.
Other than energy density, the other issue that EVs need to overcome is charging times. Modern electric cars take between 8hrs-12hrs to completely charge up compared to 3min-4min to fill up a fuel tank with petrol or diesel. This largely limits electric cars to relatively short range trips. Tesla has proposed to try and get around this by setting up a network of “Superchargers”, industrial grade high-power charging stations, between key cities such as LA and San Francisco. They claim the super charger can charge the Tesla battery to 80% in just 30min. However this means that you get 80% of the stated range after waiting ~8 times longer than you would if you were driving an ICE car and then refueling.
The Supercharging stations are simply a workaround to the real issue, which is batteries take time to charge and the rate of charge is limited by physics. This can be mitigated somewhat by increasing the surface area of the electrodes using things like nano-engineered surface treatments. Newer phones have a “rapidcharge” feature similar to what Tesla uses that claims to bring your phone battery up to 80% in about 15min. But then charging it to full capacity from 80% will take longer than it did to get from 0%-80%. The standardized connector seen above (SAE J1772) was a significant milestone that was achieved to get electric cars on the road. Electric cars need a standardized charging cable and getting different manufacturers to agree upon a standard that they’d be happy with wasn’t easy. As we enter the 21st century electric cars look poised to go big over the next two decades. However, much research and development is needed to overcome the fundamental limitations of the current generation of LiPO batteries, and whether this will come as a disruptive innovation form within the battery space or from a competing technology such as Ultra-capacitors, is too early to tell. In any case EVs are here to stay and petrol heads everywhere will have to start getting used to the idea of petrol-less cars.
Words: Kanchana Gunasekera