That said, everybody agreed during the event that uncertainty and the lack of infrastructure and associated standards are the main issues faced by the industry. “As I participate in more forums (lately the China EV Forum in Shanghai) and also communicate with industry specialists in Europe and North America I have a distinct opinion on how Charging Infrastructure & Grid Integration issues can be addressed. This article is therefore a compilation of the opinions of international leaders in the EV field,” explains Post.
Slow charging
Everybody agrees that this is the preferential way to go and the time hereto is available at home, at work and at hotels. The infrastructure hereto must be built; every residential parking lot must have a power outlet for the chargers integrated in the car (typically 3.3 kW for battery capacities in the range of 16 – 24 kWh). The next priority is to install power outlets at offices. Acceptance of EV’s for home-work use will depend on this basic, but essential infrastructure. Optimally the chargers at residential parking lots should have built in timers so they can default be charged during the night time, when the grid has ample capacity and charging cost will be lower. Of course this default mode can be easily overruled by the user.
Medium to semi-high speed charging
This mode can be in the range of 6-12 kW and will thus charge a 24 kWh battery in 2-4 hours. When used at shopping malls this will therefore not full charge the customer’s EV battery but this is also no a requirement; even when charging with 6 kW during a one-hour mall visit, adding 25% to the capacity will be enough to get the customer back home. Reducing the charging current is a priority for grid stability.
High-speed charging
Industry specialists agree that high-speed charging is a last resort and will be more expensive than lower speed charging. When commuting between cities (that have EV charging support) it is a requirement that charging stations are available on regular intervals, a bit more frequently than gas stations. If this infrastructure is not available, consumers will not buy EVs without extended range option (such as the GM Chevy Volt).
When North American consumers were asked which charging speed they would expect at shopping malls more than 90% answered: high-speed charging. When confronted with the option of free slow charging (using the internal charger) or paid higher speed charging more than 90% selected slow charging. Consequently, mall management can safely chose a low high speed (paid) option and a high slow charging capacity; the latter will cost the mall owner typically 2 RMB, well spent marketing money.
Battery swapping
There is probably no EV subject as controversial as battery swapping. When analysing this issue, it becomes clear that battery swapping is a perfect (and internationally widely proven) application here. Taxis – preferably managed by one organization – are also potential users as they also need to operate on a continuous basis.
But for private car owners battery swapping is not the preferred choice, mainly because of the associated higher cost but also because private individuals wish to fully own a car, reportedly especially in China. Besides, in a country like China, building a widely spread infrastructure for battery swapping would be an enormous investment, which can be compared with the high speed Maglev train from Pudong Airport to Longyang Road: an interesting technological achievement, but not deemed very useful by consumers. For public transport, investments are much lower as this is a controlled environment within a limited area.
Grid stability challenges and solutions
Now, Beijing has 40,000 electric cars. When a Chinese official was asked what would be the consequence of all Beijing electric cars be high-speed charged at the same time, the answer was…. a blackout! There is little doubt that in the future electric cars will become far more popular, driven by reduced prices and improved range (CALB and Foton both stated that 300Wh/kg will be a feasible reality in the near future; more than 3 times the current performance/weight ratio).
When there would be more than six times the number of electric cars in the future, the grid could not even handle consecutive slow charging. One solution, as proposed by the Zigbee group is the Smart Grid, where the utility can influence the charging times in function of the grid usage. The Smart Grid can also regulate a balanced use of other power users such as HVAC, washing machines, without sacrificing user comfort.
Additionally, energy storage – that could well be performed with written-off EV batteries – can help to balance the power usage. The most structural solution is the additional use of renewable energy close to the electricity users. Residence roofs, parking lots canopies can be covered with solar PV panels. For new construction of high buildings the use of solar windows is a consideration for the (very) near future.
Used EV batteries and wind turbines
Wind turbines can normally have a limited (typical maximum 20%) contribution to the total base load (which is much lower than the maximum load), because wind surges cause a very fast increase in output. Without this limitation the grid would become instable (fluctuating output). Used EV batteries however can be used to smother the wind turbine output and will thus allow a far higher wind penetration. Needless to say that it is advantageous –like with solar PV panels- to place them close to the users; not just for EV application but to achieve a higher Renewable Energy contribution: a wider governmental goal.
If I were in charge I would first….
This way the first and foremost EV applications Home-Work and Shopping/Dining are secured. Without this infrastructure consumer acceptance will lag behind.
[Editor’s note: James Post is the Executive Product Manager of Battery Condition Test Equipment designed by the Dutch high-tech company Engineering Spirit, active in the crossroads of power electronics, embedded & technical software. He can be reached via email]
For additional information:
China EV Charging Infrastructure & Grid Integration Forum 2012
