Electrification of Transportation in the US: Accommodating Peaks and Valleys of Electricity Use A Major Challenge

Plug-in hybrid electric vehicles (PHEVs) are being developed around the world with much emphasis on optimizing engine and lithium ion batteries operations, but accommodating the peaks and valleys of electricity use will be among the major challenges for generators and transmission operators.
On the generation side, we don’t see that much of a problem if the demand is managed intelligently, said Raphael Hudson, manager of Hart Energy Consultings Global Technical Research, We see tremendous opportunity for valley-filling, because there is a fair amount of underutilization during the early morning hours when demand is lowest.

Speaking to a gathering on September 8, Hudson explained the added demands of evening charging, especially at high power levels, could also impact the overall demand peaks and reduce the reserve margins for a regions system. Night recharging has little potential to influence peak loads, but it will still influence the amount and type of generation.

Raphael Hudson, manager of Hart Energy Consultings Global Technical Research, was among presenters at Harts Executive Breakfast Series event on September 8. Hudson explained why transformation could represent the biggest challenge for local energy providers as PHEVs and electric vehicles roll out onto the market later this year.

This is where plug-in vehicle technology can actually help, by addressing the underutilization of generation and transmission capacity, Hudson told attendees.

The general expectation has been that local distribution grids will not be greatly affected by the use of PHEVs and electric vehicles (EVs), because the recharging will occur during off-peak hours, or the number of vehicles will grow slowly enough so that capacity planning will respond adequately, he said. This expectation does not consider that drivers will control the timing of recharging, and their inclination will be to plug in when convenient, rather than when utilities prefer.

A key factor to understand is that the power demand on the grid from charging PHEVs or electric cars is directly linked to the voltage and amperage of the connection to the grid. The capacity of a battery will determine the length of time it takes to recharge, given the connection strength.

On a local utility level, transformation could represent the biggest challenge as PHEVs and EVs roll out onto the market later this year, Hudson said.

Transformers could be an issue because a lot of the transformers on a local level are already working near capacity, he said, so adding in an EV or plug-in hybrid could cause transformer failure. If you are a utility, you should probably focus your efforts in transformer renewal and in those areas that are expected to have the highest penetration of PHEVs and EVs.

During the Hart event, a second perspective on issues surrounding the integration of EVs and the electricity grid was offered by Dr. Gurcan Gulen, senior energy economist at the Center for Energy Economics (CEE), University of Texas at Austin.

Usage patterns of local distribution grids will change, and some lines or substations may become overloaded sooner than expected. Furthermore, the type of generation used to meet the demand for recharging PHEVs will depend on the region of the country and the timing of recharging. The addition of new electric capacity or an increase in the utilization of existing capacity may become necessary, Gulen said.

If you are a generator, you dont want to cycle down more than you have to; it’s just not feasible, said Gulen, a member of the GridWise Alliance and the Greater Houston Partnership Smart Grid Task Force. Ramping up and down also leads to greater emissions.

Generators and transmission operators must also consider the practical limits of new technologies in setting new and advanced standards, Gulan said.

There are also some concerns that increased electricity demand will extend the time during which electricity generators work at full capacity. It will accelerate amortization, increase opportunity costs of power plant withdrawals for planned operation and maintenance checks and change the mix of marginal generators, Gulan said.

In short, there will need to be synergy between electric car manufacturers and utilities, and some Smart Grid investments will need to be made, he added.