China's EV charging challenges
By: SGN Staff
By James Post
James Post is a product manager at a Dutch high-tech company. He recently presented at the China EV Charging Infrastructure & Grid Integration Forum 2012. He sends us this summary of the biggest electric vehicle (EV) issues.
The EV industry is far from settled. Everybody agrees that uncertainty and the lack of infrastructure and associated standards are issues. This article is a compilation of the opinions of international leaders in the EV field.
Everybody agrees that this is the preferential way to go. The time is available at home, at work and at hotels. Acceptance of EVs for home-work use will depend on this basic, but essential infrastructure. 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).
Optimally the chargers at residential parking lots should have built-in timers so they can by default be charged during the nighttime, when the grid has ample capacity and charging cost will be lower. (Of course this default mode can be easily overruled by the user.) The next priority is to install power outlets at offices.
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 not fully charge the customerâ€™s EV battery. But that is not 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 slow charging. When commuting between cities, 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 unless they have an extended range option (such as the GM Chevy Volt).
Grid stability challenges and solutions
Today, Beijing has 40,000 electric vehicles. When a Chinese official was asked the consequence if all Beijing EVs were charged at high speed at the same time, the answer wasâ€¦ a blackout!
There is little doubt that EVs 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). But if the number of EVs increases by a factor of six, the grid could not even handle simultaneous slow charging.
One solution, as proposed by the Zigbee group is the smart grid, where the utility can influence the charging times depending on grid conditions. The smart grid can also regulate a balanced use of other power users, such as HVAC and washing machines, without sacrificing user comfort.
Additionally, energy storage â€“ that could well be performed with depreciated EV batteries â€“ can also help balance the power usage. The most structural solution is renewable energy close to the electricity users. Residence roofs and parking lot 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 have a limited (typical maximum 20%) contribution to the total base load because of intermittency. Without limits on the percentage of wind, the grid would become unstable. However, used EV batteries could be used to buffer the wind turbine output thus allowing a far higher wind penetration. As with solar PV panels, it is advantageous to place the batteries close to the users. And not just for EV purposes, but to achieve a higher renewable energy contribution to the total base load power, which is a wider governmental goal.
If I were in charge of EVs in China I would firstâ€¦
- Make it the highest priority to get all stakeholders together so the decision process can start
- Require power outlets at every new parking spot at residences and offices, followed by retrofitting that infrastructure in existing construction
This way the first and foremost EV applications (home/work and shopping/dining) are ensured. Without this infrastructure, consumer acceptance in China will lag behind.
James Post is the Executive Product Manager of Battery Condition Test Equipment designed by a Dutch high tech company (http://engineering-spirit.nl), active in the crossroads of power electronics, embedded and technical software. He can be reached via email: email@example.com, China phone: 138.1663.0584
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