HomeRenewablesCharging ahead: EVs and the grid

Charging ahead: EVs and the grid

Hybrid and plug-in electric vehicles
Hybrid and plug-in electric vehicles could together make up nearly 7 per cent of global light duty vehicles by 2020 according to new research
Credit: Nissan

Hybrid and plug-in electric vehicles are becoming a significant part of the auto market as fuel prices rise, with both expected to see significant sales growth. Penny Hitchin discusses the real impact of growing EV use on our electric power systems.

The battery powered electric car has been around for more than 100 years. In 1900, out of a total of less than 4500 cars produced in the US, nearly 30 per cent were battery powered.

Yet within a few decades the electric vehicle was overshadowed by the petrol engine. The development of the electric starter and the ready availability of gasoline led to the eclipse of the electric car, with its lack of horsepower and limited range (distance travelled without refuelling). For years the popular image of the electric vehicle was typified by the slow moving milk float.

A century later, the EV is back in the frame. In the US there are now 130 000 EVs on the road. Ever-rising petrol costs, developments in battery technology and the need to address carbon emissions have all played their part in this renaissance. Automobile manufacturers are developing and vigorously marketing new models and EVs are on course to play a role in global vehicle fleets of the future. Recent analysis by Navigant Research says that hybrid and plug-in electric vehicles could, between them, make up nearly 7 per cent of global light duty vehicles by 2020.

A range of political, environmental and technological developments are driving the increase in the number of EVs on the world’s roads. Incentives for buying and running low carbon emission vehicles, improvements in battery performance, a decrease in the cost of batteries and the lower cost of electricity compared to petrol have all contributed to demand for the vehicles.

The disadvantages of EVs have been their high cost, low top speed and short range. Hybrid plug-in electric vehicles (HPEVs) using an electric battery in conjunction with a conventional internal combustion engine have been on the market for over 25 years. Developed in response to escalating fuel costs, they can be run on a charge-depleting mode (using the battery) or a charge-sustaining mode (using the fuel). Developments in battery technology have enabled auto manufacturers to develop pure plug-in electric vehicles (PEVs), of which an increasing number are on the market. EVs are more energy-efficient than conventional vehicles and dramatically cut CO2 emissions.

John Gartner, research director at Navigant, says that in most countries there is sufficient generation capacity to deal with the incremental additions of EVs. However, it could add to the peak if charging is not done intelligently.

Beefed-up batteries

Developments in battery technology have played a key role in the resurgence of EVs. Increases in batteries’ energy density (energy per unit volume) is reflected in improved range and speed. Acceleration and top speed are now comparable with petrol cars, but the distance that an EV can cover without needing to charge remains substantially less than that offered by a full tank of fuel. A high performing EV with a 60 kWh battery pack has a range of up to 300 km while a lower specification vehicle range might be half this. Realistically this limits the market to people with daily usage of 50″60 km. ‘Range anxiety’ impacts consumers’ decisions about car purchases. Increased battery capacity and the development of charging infrastructure are needed to allay some of this concern.

Increasingly, modern EVs use lithium-ion batteries which have good energy density and can be recharged before complete discharge, with no loss of recharge capacity, and can be topped up to 80 per cent relatively quickly. The loss of charge when not in use is fairly slow and they can be recharged thousands of times in their working life.

EVs in regular use need frequent charging. Vehicle supply equipment (EVSE) can be used at home or work to charge the battery, but key to increasing public acceptance and takeup of EVs is the establishment of networks of easily-accessible public charging stations.

Charging time depends on the type of charge and battery. Empty batteries using a standard 120 v (US) connection may need to charge overnight. A 240 v (UK) or 220 v (Europe) outlet can fully charge a battery in 4″6 hours. A ‘Quick Charge’ station can charge a depleted battery up to 80 per cent in less than 30 minutes.

Mark Duvall, EPRI’s electric transport director, says, “Every vehicle comes equipped with a portable cord set that charges at 1.2 kW, and that’s how a lot of people in America charge, but auto makers want to offer an option to charge in four hours.

“You don’t need very high charge rates at home or at work, you need them when you are out and about, or out shopping or going to the cinema. That is where the higher charge rates come in handy.”

Barney McGahan, Pat Rabbitte, Jerry O'Sullivan
Northern Ireland’s Deputy Secretary for Regional Development Barney McGahan, Energy Minister Pat Rabbitte and ESB Networks managing director Jerry O’Sullivan at the launch of the TEN-T fast charge point roll out by ESB ecars

There are standardized charging modes for EVs. Mode 2 uses a domestic socket to charge the battery, but a control box with a RCD protection is incorporated into the cable, giving protection during charging. Mode 3 uses dedicated charging equipment connected to a fixed installation to charge the battery. This charging point can work with either single phase or three phase installation. The charging equipment has built-in communication protocols which detect when the charging is finished and can manage energy consumption. Mode 4 uses a dedicated charging point and converts the AC current from the grid to DC current, allowing a charging voltage around 500 v and a charging current around 125 amps. This regime allows fast charging in 20 minutes.

What impact could mass charging of EVs have on networks in future? Gartner says that in most countries there is sufficient generation capacity to deal with the incremental additions of EVs.

“Where it will have an impact is at the local level, notably where there are older transformers,” he says. “There can be a clustering effect with EVs: they tend to be acquired where there is a particular demographic, and this concentrates their impact in a particular locale. We may need to see transformers swapped out in a particular neighbourhood or in a block where there is a shared transformer.”Duvall is confident that power systems can cope with charging electric vehicles. “Given that load is generally flat or declining in most of the first world, it’s not a big challenge to meet that, especially as it will take time,” he says. “EVs are like any new technology, they start really slowly and then they ramp up. A car is not like a smart phone that you buy every couple of years. Cars are a big purchase that last a long time and we replace them slowly.”

He adds: “One of the things that American utilities are proactively doing is asking customers to voluntarily notify them when they buy an EV. They go in and do a pre-inspection to check if the system has enough capacity at the transformer level. The kind of approximations we are hearing from US utilities in California where there are a lot of EVs is that overload happens maybe 1 per cent of the time. Then they upgrade the transformer. It’s not really an issue, but as the grid expands we might need to upgrade. We can mitigate that by getting more people to charge off peak or to charge at different times.”

Views from Europe

In the UK, Simon Harrison, development director for power at Mott MacDonald, is cautious. He is concerned about the scenario where someone gets an EV and everyone in that road follows suit. If they all want to charge their cars simultaneously, this could lead to a charging demand greater than the capacity of the feeder.

“If everyone wants to switch the charge on at the same time it completely changes the pattern of loading on that distribution feeder, especially if the cars are all on fast charge. At the moment the average load on the distribution feeder per house is a little over 1 kW and an average car plugged into the mains will be around 3 to 8 kW. A fast charge could be more than that. The residential system is not designed to take a large number of EVs unless they move to having smart infrastructure to manage the charging pattern of those vehicles so that they are spread out across the night.”

Congestion charge: “If everybody comes home and plugs in their car at the same time, this is not good,” says Gunnar Lorenz of Eurelectric
Credit: Elektobay

Gunnar Lorenz, head of the networks unit at Eurelectric, is confident that networks will be able to meet the demand; there will be time to adapt systems as EV market penetration increases. “Generally, the total demand of EVs will not be too dramatic. This means we will be able to provide the energy. We are talking about maybe 15 per cent of the total demand today could be EVs, but it will take some time to build up. On the generation side we can cope with this. However on the network side it could be more problematic because the electricity has to be there at a certain time. If everybody comes home at six o’clock and plugs in their car at the same time, this is not good.”

Hubert Lemmens, chief innovation officer for the European transmission system operator (TSO) Elia, says that while distribution system operators (DSOs) operate close to the vehicle connection points and their interest is to manage the loading of the cables, TSOs are concerned with balancing the system.

“In order to manage the whole system we need to have intelligent systems exchanging information between the car and the DSO, the TSO, the supplier of energy and the leasing company (if it is a leased car), so standardization is important,” he says.

Lemmens says that protocols about the information exchanged between the parties (DSOs, TSOs, auto manufacturers and charging stations) and also the technical and material levels for data exchange between the different equipment on the system must be defined. “You have to have information exchanged between the car, which has the information about the battery situation, how many kW hours to charge, when the charge is due, when the car is needed, and you need to know the quantity of energy that is supplied to the car and you need to know who to bill and so on. It is a complex system of information exchange. It can only work if enough standardization and common standards exist among the different parties.

“It is technically feasible but it needs to have the co-operation of all the different parties. Car manufacturers, distribution system operators, suppliers can all be competitors but if they want to promote EVs they must co-operate.”

An end to dumb charging?

Everyone agrees that smart grids and smart charging are the way forward. Lorenz says: “What we are proposing is smart charging, so for example, the car charging is done at midnight when the other loads are off. This would decrease the impact on the distribution network and thus the investment costs will not be so high.”

A smart grid can digitally process information about energy supply, demand and patterns of consumption in order to route power efficiently from the point of production to its end user on the network. A modernized grid will enable two-way flows of energy and uses two-way communication and control capabilities that will lead to an array of new functionalities and applications.

Smart grid technology will enable utilities to offer flexible pricing and other tariff incentives which would help meet the demand from large EV fleets by encouraging consumers to reduce peak”time consumption. It would also open up the possibility of using EVs to balance the grid.

Lemmens says: “One of the issues in today’s electricity systems, and will be even more tomorrow, is that renewable energy like wind and solar depends on availability of the natural resources. In order to balance such a system we need to have flexible generation, but flexible load can also play a part. I think, used intelligently, EVs can play a role as flexible load and can help to balance the system.”

Other possibilities are being explored. Duvall points out that utilities are increasingly focusing on how to integrate more distributed renewable energy and local generation. EVs are selling well in Japan, and after the 2011 earthquake there has been a lot of interest in using vehicle-to-home (V2H) back up power. For example, a product on the market enables the Nissan Leaf to put 6 kW of power back into the house.

There are currently no projects where EVs are aggregated to provide large scale storage to the grid, although the US military has pilot vehicle to grid (V2G) projects. Duvall says: “We are in a time frame where there is lots of interesting technology. We will see an increasing number of small scale projects over the next three to five years. Things are happening more and more quickly, so we should be ready for anything!”

New business models needed

The rate of growth of EVs nationally and globally is uncertain, but the direction is clear. Work to understand the likely impacts on the electric grid is underway. Pilot studies are exploring models for developing the necessary infrastructure for charging EVs, but finding a business model for public charging points remains a challenge. At present public sector funding is providing the investment, but evolution of a commercial model is needed for takeoff.

Utilities are monitoring the situation closely, in the knowledge they will be required to gear up to the interlinked challenges of increased renewable and distributed energy, storage, EVs and smart grids.

The synergy between renewable energy and EV charging lies in the use of smart grids. Networks built in the last 30 years have some communications built in, and deploying the latest upgrades and new equipment enables smart functioning. Adding EVs to the grid may be a challenge but it is also an opportunity. Smart charging could allow EVs to be integrated into the grid, make better use of renewable energy, and help balance the grid by making a slight change in the frequency of the voltage.

There is a lot of work to do and investment is required, but spikes in the price of petrol, government commitments to reducing emissions and technological advances in design and manufacture of batteries and vehicles will all contribute to increased takeup of EVs. Interesting developments lie ahead as auto makers, leasing firms, charging stations, EV owners and utilities forge smart collaborations.

Penny Hitchin is a freelance journalist specialising in the energy industry.

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