Back in the 1960s, the space race was in full swing and huge American gas-guzzling cars, more akin to sofas-on-wheels than vehicular transport, were kings of the roads. It's no wonder the future visions of the 21st century drawn at that time included flying cars and autonomous-vehicle-filled highways.
The reality for the 2020 motorist is markedly different. For those on their daily commute, speed limits seem more like speed aspirations, fully autonomous vehicles are still limited to prototypes, and a widely available flying car remains a decade away.
In the meantime, the carefree approach to fossil-fuel usage has finally caught up with us. Road transport in Europe represents almost a quarter of its greenhouse emissions1. It is the only sector that demonstrated emission growth between 1990 and 2007, and only a gradual decline since. Studies show particulate matter from motor vehicles also has a direct health impact for a subset of respiratory diseases.
In the late 1990s, a commercial alternative to the purely internal combustion engine (ICE) powered vehicle emerged with the introduction of the Toyota Prius. This model is now considered one of the cleanest3 and most fuel-efficient cars available4. Since then, Tesla has become prominent, pushing plug-in battery electric vehicles (BEV) into the limelight. As the first automotive company to sell more than one million BEVs5, its strategy has been to refine the technology in high cost, luxury vehicles, allowing it to trickle down into affordable electric cars for the masses.
Enabling Technologies
This series of blogs discusses the all-electric revolution in powering vehicles, starting with the battery technology that made it all possible: Li-ion. One of the biggest hurdles in developing BEVs has been finding a storage technology that could compete with the energy density offered by petrol and diesel. While Li-ion batteries are yet to meet their full theoretical potential, in combination with advanced battery-management systems (BMS) and efficient power conversion, they can be used to build vehicles with ranges of 600 km. Unfortunately, such vehicles fall into the luxury car price segment. Those of us with more moderate means will currently have to settle for vehicles with a range of 100 to 200 km.
Of course, the other aspect to high range is the powertrain, the next topic in the series. Brushless electric motors are much more efficient than the brushed DC motors of the past. However, designing high-efficiency drive electronics is key to making the best use of the battery's charge. To date, due to the powers and voltages involved, IGBTs have been the primary semiconductor technology used. Wide bandgap (WBG) technology, such as silicon carbide (SiC), is now reaching a maturity level that allows it to fulfil the high standards of the automotive industry. In our view, this will lead to further efficiencies in power conversion, along with a reduction in size and weight that will moderately benefit BEVs.
Barriers to development and adoption
With a reduced range versus conventional ICE vehicles, society has to change views on vehicle 'refuelling', which leads to the next topic in the series: charging. BEVs cannot be refuelled in minutes like ICE vehicles. Instead, charging requires some planning and integration into vehicle usage. For example: where we park for long periods, such as the office car park, while shopping, or where we park and switch to public transport. Fast DC charging is defined as delivering powers of up to 350 kW. While such technology comes close to the refuelling time of an ICE, it depends on the battery technology of the BEV supporting it. There are also some significant heat dissipation challenges, even at efficiencies of 97% or more.
Of course, BEVs are not the only possible replacement for ICE vehicles. Fuel cell electric vehicles (FCEV) have been quietly progressing in the background with a handful of models now available. Using hydrogen fuel, they refuel like an ICE as well as offering a comparable range. Here the challenge remains price for entry-level models, something not helped by low volumes and the limited number of filling stations offering hydrogen.
Future electric vehicles
Our final blog looks at the motoring landscape out to 2030, taking a realistic look at what current technology research can be commercialised in that timeframe. Range improvement through technical advancement alone will be limited, and significant breakthrough in battery technology is also unlikely. Hydrogen does seem to offer a lot of potential, thanks to the similar ownership experience to ICE. And perhaps car ownership expectations and business models will change to accommodate the desperately needed carbon emission reduction from the transport sector.
- In this series of six blogs, we examine the topic of electric vehicles, the technologies that enable them, the limiting factors affecting development and adoption, and what we can expect in the future.
The next blog in the series will look at: Battery Power Packs
