By BENJAMIN LAWLER //
The internal combustion engine is old, inefficient and dirty. Its days are numbered. The future is electric vehicles, which are new, efficient and clean.
At least, that what you’ve been told, by people who have a financial interest in propagating EVs.
The truth is somewhat different.
EVs and ICE-powered vehicles first competed in the late 1800s. But in the early 1900s, the ICE was found to be more desirable due to its lower cost, greater range, lower weight and better reliability, so the engine was used in almost every transportation application for the past 120 years – until now, when EVs are being advertised as the more efficient technology.
But are they really more efficient? To answer this question, we need to define efficiency as the usable energy that you get (energy out) as a fraction of the energy that you had to pay for it (energy in). If we multiply an average electric-motor efficiency (85 percent) by the national average electricity generation efficiency (33.6 percent), we get an average EV efficiency of 28.6 percent.
The average efficiency of an ICE depends on the engine itself. Some can achieve efficiencies over 50 percent. But for a fair comparison, let’s consider the type and size of engines used in passenger cars, which can have efficiencies of 0 percent (at idle) to 40 percent (at their peak).
How the engine is used in the vehicle dictates its average efficiency. In all honesty, the numbers you’ve heard for ICE efficiency (mid-teens) are true, due to how the engine is used in the vehicle. It’s not hard to imagine that if the engine can be 40 percent efficient, but instead is averaging 15 percent, then it’s not being used correctly.
In other words, in a conventional vehicle, the engine is not being used intelligently – and that keeps average ICE efficiency low.
Benjamin Lawler: Giving internal combustion a little gas.
Instead, consider the example of the Toyota Prius or a similar “power-split” hybrid. The power-split hybrid has an ICE, one small electric motor, one medium electric motor, a planetary gear set and a medium battery. The purpose of the electric components is to enable the ICE to operate more efficiently – and as a result, the average ICE efficiency in a power-split hybrid is greater than 32 percent.
Last, proponents of EVs often state that they are “clean” and have no emissions. It’s true that there are no emissions from the EV itself after it’s been constructed. But what about the emissions from electricity production? And what about the emissions associated with manufacturing the battery? The amount of emissions produced by manufacturing a single EV battery is on the order of years’ worth of driving an ICE-powered vehicle – not days or months, but years!
None of this is meant to discredit EVs, which do have their place in today’s society and in the future. The problem comes from thinking that EVs are the “silver bullet.” Instead, we need to consider each specific application and determine the most efficient powertrain for that application.
If EVs are not the silver bullet they’re being marketed as, is there any hope for the future of energy and transportation? Yes – there is a lot to be excited about!
Over the years, we’ve made considerable progress increasing ICE efficiency, reducing their emissions and using ICEs in a more intelligent manner. The power-split hybrid is evidence of that. We’ve reduced the cost of batteries significantly and improved their energy density. In the future, a larger fraction of the electrical grid will be generated by renewable sources, reducing the environmental impact of electricity production for EVs.
The most exciting future technology is alternative fuels. All of the issues with ICEs – all of their harmful environmental impacts, all of their political issues – aren’t related to the engines themselves, but instead are caused by burning fossil fuels.
But engines are not married to fossil fuels. Engines can operate on a wide variety of fuels without negatively impacting their efficiency or emissions. Some alternative fuels actually improve the efficiency and emissions characteristics.
In the future, we’ll have sustainable biofuels that absorb carbon dioxide during fuel production. There will also be fuels produced exclusively from renewable energy sources. These fuels can use the same distribution and refueling infrastructure we already have.
Most significantly, an ICE-powered vehicle using a renewable fuel can provide a net-carbon neutral – and completely sustainable – energy and transportation solution for the future.
This article originally appeared in the Advanced Energy Research and Technology Center’s Fall 2018 newsletter. Dr. Lawler is an assistant professor in Stony Brook University’s Department of Mechanical Engineering.
