05 Mar 2012 09:03:05
The dilemma of fast-charging of electric vehicles
The dilemma of fast-charging of electric vehicles
By Dr Peter Harrop
People like to see a lifebelt by the local river even though they may never use it. They certainly do not want to pay for one though. It is like that with the fast charging of cars. We all want to charge our electric car in the blink of an eye. Indeed, we may be happy to pay through the nose for that electricity when we are far away if the only alternative is to walk home or at least be late for an appointment. Many companies now offer fast chargers for on-road vehicles though very few have been installed. For instance, Japan has only installed 80 across the whole country.
Challenges with fast chargers include the following.
Fastest "SAE Level 3" charging stations give only ten times the speed for one hundred times the installed cost. This is because they cannot use the inverter in the vehicle because it is not powerful enough and they need extra safety measures. Although Nissan has offered fast chargers down to $10,000 or so that is at a huge loss, the costs of most fast charger designs being near to $65,000 at present in our opinion. The price premium goes even higher when they need a community transformer as a grid upgrade. On the positive side, Mark Duvall, director, Electric Transportation and Energy Storage at the respected Electric Power Research Institute EPRI in the USA said at the recent Advanced Automotive battery Conference in Orlando Florida that grid upgrade is not commonly required and, when it is, it is something that was going to be needed anyway and is just brought forward a bit.
There are options instead of grid upgrade. One can slow charge a large battery in the charging station as with the vanadium flow batteries in the UniCube. Here charging can even include solar power and/or a wind turbine to give complete independence from the grid. However, this does not cope with intensive use and there is a cost. Alternatively, load management is offered by Siemens and others to prevent overload when too many cars are charging. This can even happen at Level 2. However, customers can be inconvenienced by this. Then there is EPRI developing HF solid state transformers in fast chargers that work directly from the main grid.
Standards not fully agreed/adopted
The Society of Automotive Engineers and others are completing standards for fast charging of on-road vehicles. Although these may look very grand with a lightning bolt of up to 240 kW permitted, in many countries the permitted grid upgrades simply do not cope with this, there is a big cost and there are other issues such as possibly needing an attendant. In reality, the sweet spot for fast charging is 50-65 kW. Contrast that with the fact that, to mimic a gasoline station filling many vehicles in one minute or so you need 40MW.
Uncertain whether hybrids need it or can do it
We are in the age of the hybrid on-road vehicle not the pure electric one. Most analysts agree that hybrid cars, buses and trucks will outsell pure electric ones by at least four to one over the decade. Plug-in hybrids are coming in with a rush (we all want "fuel" at one fifth of the cost and no range anxiety) and their electric range is rapidly advancing from 12 miles to 50 miles and later more. All the same, it is still not obvious that plug-in hybrids need Level 3 charging because their batteries are still small enough to charge in one hour or less with a Level 2 charger at least for the next few years. Meanwhile, it is not even possible to fast charge the archetypal plug-in Prius, that is expected to outsell the others in the short term, because it does not have an appropriate socket. Will plug-in hybrid sales drive Level 3 charging station sales by the end of the decade or not?
Uncertain whether pure electric on-road vehicles will be an immediate success
Pure electric on-road vehicles are not yet selling well. Over 100 Chinese manufacturers offer them but none have good sales because of the price even more that the range issue. The Mitsubishi MiEV is flat-lining at a modest sales level according to statistics presented by the Institute for Information Technology at EV Japan in Tokyo this year. The Nissan Leaf global rollout has been delayed but sales were quite good, if irregular, in 2011 and may exceed 65,000 in 2012 vs about 90,000 achieved by the leader in pure electric golf cars, Ingersoll Rand Club Car. Yet some of the largest manufacturers of fast charging stations feel that, sooner or later, fast charger sales must follow pure electric on-road car sales: what happens with pure electric cars really matters.
Not suitable for residential use
At $20,000–$70,000 even before that troublesome installation requirement, Level 3 charging stations will not appear in domestic premises beyond those of your local billionaire.
Big heavy cable and connector to car is tough to use.
A Level 3 charger looks like a gasoline pump with a "pipe" of similar dimensions but try to use it and you realise it is much stiffer and heavier. Will small or infirm people be able to cope with this? With inductive contactless charging they are relieved of the bother but fast charging inductively has many difficulties and it is not commonly available nor are there adopted standards for inductive charging.
Can destroy or shorten life of some batteries
Fast charging can shorten the life and even destroy some lithium-ion batteries used in on-road vehicles. To cope, some batteries must be charged more slowly. Toshiba and Altairnano have lithium titanate anodes in their vehicle traction batteries that are more tolerant of fast charging and some other battery makers are happy to see their batteries hit with the electric currents offered by typical fast chargers but care is needed. Just shortening the life of a $12,000 battery in a pure electric car by one year represents a huge cost.
Rather like that lifebelt, fast chargers currently have no payback. They are rarely being installed at roadsides, owners preferring semi-supervised sites such as workplaces, retail sites and other destinations. For these locations, they rely on the charity of local and national government and the owners of those sites. How secure is that funding in the years to come?
All this sounds very negative but the technology of fast charging is moving forward in leaps and bounds and we want them – yes, we want them. At Electric Vehicles Land, Sea, Air USA 2012 in San Jose California March 27–28, learn more from Schneider Electric, ECOtality,OLEV Technology, Qualcomm Halo, Electrovaya, Bosch, BMW, IBM and others encompassing the batteries and chargers for all forms of electric vehicle.