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Mass adoption of electric cars poses cost, charging dilemma

Posted: 28 Dec 2015     Print Version  Bookmark and Share

Keywords:NTNU  smart grid  electric car  EV  electricity consumption 

Looking way into the future, more people charging their EVS when they return from work could pave the road for electricity consumption issues, and consequently, the financial side of things. If everyone drove electric cars, there wouldn't be enough power to charge them all when people got home in the afternoon. The solutions could hurt your personal finance.

Power consumption: When people with EVs come home from work in the afternoon, they plug in their cars to charge them. That results in an extra peak in electricity consumption in the afternoon.

"We're moving towards a different kind of power use," said Olav B. Fosso, professor and director of Norwegian University of Science and Technology's (NTNU) energy strategic research area.

This peak may eventually become a major challenge for the electrical grid.

"We could have big voltage problems, with limited transmission capacity within the distribution system," said Fosso.

EV charging

People can't all charge their electric cars simultaneously. Electricity is perishable. It's helpful if your power use is relatively even over a 24-hour period. Photo: Thinkstock

Capacity could also become a problem. Large variations in consumption throughout the day are challenging. Electrical power is perishable. That means it's an advantage to have relatively stable power use over a 24-hour period. Renewable energy from the wind and sun has to be used immediately.

Fosso said Norway is lucky to be able to regulate its hydropower.

Water reservoirs allow adjustments in the power supply, but very few countries have that ability, and even in Norway high consumption at certain times of the day poses a challenge.

EV numbers on the rise

Afternoon charging of electric cars isn't a problem, yet. But the orders for electric cars in Norway show that growth won't stop with the almost 75,000 EVs already on the road, including hybrids.

Fast chargers

Fast chargers around 20kW can be installed for home use in the U.S. If these rapid chargers become common in Norway, the problem will intensify. Photo: Thinkstock

"Nothing suggests that this development won't continue," noted Fosso.

Cars have different charging power and storage capacities. Storage capacity is related to the car's range. Mitsubishi's capacity is around 16kWh, while the Nissan Leaf has a capacity of about 20kWh and Tesla, 85kWh. Battery size determines the charging time for a given amperage, with typical charging efficiency ranging from 4kW to 8kW. Home chargers provide long charging times, but that may become problematic when a lot of people charge their cars at the same time in residential areas. Quick charger installations require a higher current feed and thus a stronger electrical grid.

Fast chargers of around 20kW are now available for home use in the U.S. If this type of rapid charger becomes more common in Norway, so will problems.

A smart grid can affect your wallet

Afternoon peaks in power use are common, because people come home and turn on heaters and appliances. But this peak will also be increased when people come home and plug in their EVs.

That's when people have to get smart in how they use the power. A smart grid, which uses new technology to better leverage the electrical grid, will likely be an essential part of the solution.

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