How many EVs can the power network cope with?

What distribution system operators need to do to ensure that their grids are prepared for the future.

There are more than one billion vehicles on the roads around the world. Globally, they’re responsible for about one-fifth of direct CO2 emissions from fuel combustion, and hopes for more sustainable mobility are being pinned on electric vehicles. Distribution system operators have a key role to play in helping them make the breakthrough – but putting charging points in place isn’t enough. 

There’s no arguing the fact that electromobility is riding high. Tesla started the ball rolling, and established automakers are now joining in. Now every prominent maker has at least one electrically powered model in its catalog. But the picture is different on the streets. Although demand for electric vehicles is rising sharply, global sales figures are still modest compared to new gas- and diesel-powered vehicles. More than 80 million new vehicles were sold in 2018: Of those, only about two million had an electric motor.

 

From a climate policy perspective that’s bad news, given that road traffic is responsible for almost one-fifth of direct CO2 emissions from fuel combustion worldwide. If all vehicles were to run on electricity from renewables, we could save about six gigatons of CO2, or more than the entire annual greenhouse gas output of the European Union. To achieve the objectives of the Paris climate accord, it would be a blessing if we could have nothing but electric vehicles on our streets as soon as possible. 

eMobility charging station

Electric Vehicle Adoption and Public Charging

eMobility is a challenging territory for the entire ecosystem. The magazine 'Transmission & Distribution World' and Siemens have joined forces and put together a paper from which you will learn where the EV market is headed, essential objectives, and how to get there.

EVs: A challenge for distribution system operators

But it isn’t so straightforward. For our transport systems to be completely electric, the existing infrastructure needs to be expanded to enable all the vehicles to be recharged. And new charging points are just the tip of the iceberg: Ultimately, charging requires a vast amount of power. At a present-day quick-charge station with a charging capacity of 150 kilowatts, a car draws the same amount of power in 15 minutes as you’d need to toast 5,000 slices of bread. If huge numbers of vehicles suddenly ran on electricity alone and made use of quick-charge facilities, that would put huge stress on our power networks.

 

“Some of our existing power networks would be simply overloaded if millions of vehicles were to switch to battery-only operation overnight and had to be recharged in a matter of minutes,” observes Ben Gemsjäger, deputy head of Department for Distribution and Decentralized System Studies at Siemens PTI. He should know: He and his colleagues have been engaged by energy utilities to investigate just how future-proof the distribution systems are – and suggest steps that can be taken to equip them for the challenges of the future and to adjust investment strategies as appropriate.

Some of our existing power networks would be simply overloaded if millions of vehicles were to switch to battery-only operation overnight and had to be recharged in a matter of minutes.
Ben Gemsjäger, deputy head of Department for Distribution and Decentralized System Studies at Siemens PTI

Electromobility poses a double challenge for distribution system operators: First, EVs add to the number of consumers. The more EVs that are charged at the same time, the more likely it is that the grid will be overloaded. Second, electromobility is only environmentally practical if the required electricity comes from renewable sources. But wind and solar power have the problem of being irregular, and most wind turbines and sizeable solar power plants are located in rural areas, while most of the power is consumed a long distance away in cities. “Urban distribution systems will have to be able to establish a balance between large volumes of power from decentralized and irregular generation sources in the future,” Gemsjäger observes. “They’ll need to become much more flexible for that to happen.”

Just how fast is the EV revolution? 

No-one can say for sure how fast electromobility will catch on. Cost is a key factor. A current study by McKinsey suggests that, no later than ten years from now, battery-powered electric vehicles will be cheaper to buy and run than their gas and diesel counterparts. In addition, more and more countries are putting policies in place that favor lower-emission drive systems, including banning the sale of vehicles with internal combustion engines: for example, Norway is a trailblazer with its plan to ban the sale of new ICE vehicles from as early as 2025. China and India, both enormous markets, are considering similar actions for 2030, and the same goes for many other countries.

Urban distribution systems will have to be able to establish a balance between large volumes of power from decentralized and irregular generation sources in the future.
Ben Gemsjäger, deputy head of Department for Distribution and Decentralized System Studies at Siemens PTI

Even so, that doesn’t mean the only winners can be EVs with battery storage systems. It’s conceivable, perhaps even probable, that other technologies like hydrogen power or synthetic fuels will enjoy substantial growth in market share in the medium term, which will also have an impact in terms of the infrastructure they’ll need.

 

It’s difficult to forecast the influence that future mobility concepts will have on motorized personal transport, or how battery-driven vehicles will develop. Various mobility scenarios suggest that battery-driven electric vehicles will make up between 10 and 95 percent of the fleet by 2050. “The range of these forecasts alone shows the level of uncertainty that grid operators have to allow for in their planning,” Gemsjäger notes. 

Charging infrastructure: Planning for the “unplannable”

But even so, distribution system operators can’t simply sit and wait: Large parts of their infrastructure are designed with a 40- to 50-year timeframe in mind. In other words, what’s planned today will be in service to 2060. So where and how will electric vehicles be recharged? And how many should be accommodated? These are tricky questions, because we’re talking about more than just the sheer numbers of battery-operated vehicles.

 

For example, if car-sharing strategies really take off, that will alter the demands being made on the charging infrastructure. If cars are shared, they’ll need to be quickly charged again after they’re used, which means that powerful public charging stations will be needed. But as long as all drivers still own their own cars, there will still be a need for overnight charging solutions. In this scenario, charging speed is less important.

 

 

A step-by-step approach is recommended when it comes to integrating the future charging infrastructure into the grid.
Dr. Adam Slupinski, head of Distribution and Decentral Systems at Siemens PTI

So what options are available to grid operators to ensure that their networks are prepared? “A step-by-step approach is recommended when it comes to integrating the future charging infrastructure into the grid,” says Dr. Adam Slupinski, head of Distribution and Decentral Systems at Siemens PTI. “The first step is to determine the additional charging load that EVs will impose in the future and where they’ll come into contact with the grid. Using this knowledge, we can simulate the grids and apply long-term planning to optimize them both technically and economically.” In the process, grid operators will also learn what resources are potentially critical. Then, through a process of predictive and intelligent re-investment planning, they can keep the expansion costs brought about by electromobility to a minimum.

 

Slupinski considers this approach to be especially practical for medium-voltage grids. “In the low-voltage grids, volume issues and the high level of uncertainty about charging points in the future mean we’ll have to make use of a higher-level charging management system to control the charging stations.” An intelligent system of this nature will enable communication between the distribution system and the charging points, and will ensure that the number of EVs being charged simultaneously is limited to what the grid can accommodate. 

Battery storage and decentralized energy systems

In addition, it’s possible that we’ll see more use of battery storage and decentralized energy systems (DES) in the future. Battery storage systems are well-suited to providing capacity at the local level to charge EVs. Storage solutions are also of interest to grid operators because they can supply balancing energy when required: They can accommodate temporary excess production from solar power plants or wind turbines, and conversely, they can help bridge shortfalls when generation volumes are insufficient, which keeps the grid stable.

 

In parallel, DES – mainly consisting of solar or combined heat and power generation (CHP) systems – will generate power close to where it will be consumed. The benefit of decentralized power stations like these is that there’s no need for supraregional supply structures, because the electricity is generated and consumed locally.

Making use of digitalization for more extensive grid models

The complexity of the current situation pushes the tried-and-true methods of grid analysis to their limits. “The utility of the future will need a detailed digital model of the energy system that’s as transparent as possible,” says Gemsjäger. Otherwise, it will hardly be possible to plan for an efficient and reliable supply that will meet requirements. A digital model of the grid will do more than simply identify vulnerabilities in the existing infrastructure. It will also incorporate additional data, for example on population, structure and mobility infrastructure – and will consider operational factors like voltage regulation, repositioning open points, and reactive power management. It will therefore lay the groundwork for scenario-based stress tests, which will show when and where the grid is reaching its limits as well as how it will deal with future changes in user behavior.

 

“Grid transparency and flexible models are the key to being optimally prepared for the electromobility of the future and identifying ‘no-regret’ measures,” says Gemsjäger. “In other words, measures we can take today without regretting them tomorrow, regardless of the scenario that plays out.” And the reverse is also true: The more prepared grid operators are for the drive technologies of the future, the faster these technologies will catch on.

Photos: Siemens AG, GettyImages

2020-01-30

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