Supercharging Infrastructure Interaction with Power Grid

Supercharging Infrastructure Interaction with Power Grid

Supercharging stations essentially behave as a huge electric load in the power delivery system. In peak time (all charging ports are occupied) it can reach ~1 MW (135kW * 8) power demand in the system. From the electric utilities' operation and planning point of view, I'm wondering if Tesla supercharging stations are installed along the power transmission system or within distribution system? This configuration selection depends on both load nature and power system design. Furthermore, will supercharging station require dedicated lines/substations or just reside in the existing distribution systems?

SamO | 12. Juni 2017

Batteries and the present and future of Supercharging. Then solar energy production. The grid will be BETTER for having a Supercharger nearby.

Mike83 | 12. Juni 2017

With PowerPacks who needs the grid. Why should we have to pay distribution when solar production is local?

SamO | 12. Juni 2017


It's still better for Tesla to provide grid services and to enroll in time-of-use, where offered. Tesla can buy at night and sell during the day. Just those transactions could be enough to offset the cost of the network. Or even a net positive in locations where Supercharger use isn't voluminous.

NKYTA | 12. Juni 2017

An 8 stall setup would most often be using 135kW * 4.

Mike83 | 12. Juni 2017

SamO your right. It is good leverage for the future.

Rocky_H | 12. Juni 2017

It's a more detailed question than any of us here can answer. This is part of why Supercharger sites are kind of expensive to build. They have to do this kind of planning and communicating with the regional electric utility to specify this huge 500kW+ load, and the utility has to plan how they are going to handle it.

As @NKYTA pointed out though, Supercharger stalls share hardware, so for an 8 stall location, it has 4 of the stacks of 135kW charging equipment.

Earl and Nagin ... | 12. Juni 2017

Superchargers are installed in places that have commercial/industrial connections. The amount of power is not very high compared to a few strip malls, restaurants, and hotels.

rxlawdude | 12. Juni 2017

The solar power arrays on Supercharger canopies can't possibly cover the power requirements.

Mike83 | 12. Juni 2017

Currently not, expansion is the plan I believe.

Bighorn | 12. Juni 2017

Since there are 16 stall stations, I didn't assume the OP was necessarily confused in his math.

milesbb | 18. Juni 2017

I am a retired power EE. I believe society is better served by putting energy storage, size and location in the hands of grid operators. Battery storage systems can be placed to support system voltage in areas of the grid that need it. Use of battery energy can be timed to fill in for forecast wind shortages. Large scale battery storage systems can be more easily maintained and purchased at a significant discount. Time of use billing plans have a key role in moving loads to more favorable time period. Time of use billing plans are not effective in dealing with load swings like toilet flushing during the Super Bowl commercials, or loss of power from clouds passing over solar farms. Having instant access to battery storage allows the utility to reduce or even eliminate spinning reserve. Spinning reserve has always been a great efficiency loss in the utility system.

rxlawdude | 18. Juni 2017

Hehe, load swings for dumps. This argument is swirling the drain. :-)

SUN 2 DRV | 18. Juni 2017

Miles: Yes, those are all great benefits of utility scale energy storage. But why not also support and encourage energy storage at the local and individual building levels? Seems like many of the value props you list would apply to individual building owners too. Doesn't it make sense to "firm up the grid" at all tiers?

Frankly one of the tenets of the Internet is to have a fully distributed system with as little central control as possible. Seems like a good long term goal for the EnerNet too... Transactional energy flows by many distributed players could be a very interesting model.

carlgo2 | 18. Juni 2017

It just seems cheaper to build up huge solar utilities on on one site, mass produce it, than to install hundreds or thousands of unique systems, each with their own difficulties. Decentralization is good on paper and philosophically, but might not be practical.

Earl and Nagin ... | 18. Juni 2017

I agree that technically you are right but unfortunately, power utilities are often subject to political and bureaucratic pressures that preclude them from doing the right thing. If I take care of surges on my home with a Powerwall then the grid won't have to deal with those kinds of issues.

Earl and Nagin ... | 18. Juni 2017

I should add that I can't change my power company but, with my own storage, I can unilaterally do the right thing.

eric.zucker | 19. Juni 2017

It may not be possible to have enough solar at the supercharger location to cover its usage - what prevents Tesla from deploying a solar farm injecting at a more appropriate location, essentially using the grid to "transport" from A to B.

As long as the production exceeds usage, it's fine.

I don't think one can legally create a private power transmission line between two properties.

carlgo2 | 19. Juni 2017

@ez: Surely this is what Tesla will do. Tesla could get clever and release power from their solar arrays into the grid to match real-time usage reports uploaded from the chargers to the array's storage batteries.

This would be free, but excess power would be sold for a profit.

mark.willing | 19. Juni 2017

"...Decentralization is good on paper and philosophically, but might not be practical."

So-called micro grids are likely the way of the future. In an analog society, the idea of a centralized power plant is good on paper, both economical and practical. That is what we are moving away from. If anyone remembers the huge black throughout the northeast area in 2003, that is something no one wants to deal with again. Now, with newer digitally,...computerized,...control systems making things much more efficient, it also opens up the threat of malicious computer hacking. Decentralization, micro grids, residential and commercial "point-of-use" power, battery storage, etc. greatly reduces the risk of massive black outs. When power goes out, not only is there economic losses for businesses, but it may also present a national security risk.

eric.zucker | 19. Juni 2017

There needs to be a structural redesign of how electric energy is distributed.

Today grid delivers power, local renewable production essentially reduces the consumption of the endpoints.

There are complex grid issues when the renewables output exceed the local consumption such as islanding. - a condition where a disconnected part of the grid continues to be powered from its own inverters. Theoretically if the grid goes down, grid-tied inverters detect it and should stop. However if enough inverters are running on that branch, they can fool each other into thinking the grid is still there.

This is very dangerous to maintenance personnel, as when they need to cut power to a line to work on it, it can surprisingly still be live from local sources.

Reconnecting is even trickier as it requires synchronising the power sources. Both are supposed to run at 50Hz or 60Hz but there are natural variations as power production vs consumption varies. You have to close that switch at the exact instant both grids are in sync, but you can't easily control the frequency/phase shift of either.

There are solutions, like creating HVDC or 400Hz backbones to interconnect grids, which is an interesting but expensive proposition. Finding a cheaper way of achieving that flexibility, and financing it, is key.

tes-s | 20. Juni 2017

All the supercharger sites I have seen are distribution-connected, not transmission-connected. They get their own transformer with a 12.5kV or 25kV distribution feed.

Right now superchargers are simply a customer like any other. As they become more prevalent and larger, I expect they will be more closely included in substation and distribution planning. Substations vary in size, but I guess around 50mW serving a few square miles is common. Rarely is there more than one supercharger connected to the same substation, so unless a substation is already maxed out a supercharger is not an issue.

I think home charging will be a larger challenge for power distribution. TOU metering can balance supply and demand, but overnight charging in residential areas may exceed the capacity of local distribution (not the substation). I have heard of people having the power company put in another transformer to meet the demands of a 20kW Tesla charger.

VFEA | 17. August 2017

Excellent and intriguing questions. Supercharger sites reflect generally the profile of a large commercial or small industrial customer, in other words, a customer connected with distribution networks subject to state jurisdiction. Simple enough.

Interconnection with the high-voltage transmission network would appear to involve expensive transformers and shift jurisdiction to the federal agency, the Federal Energy Regulatory Commission (FERC), the former Federal Power Commission. While FERC has well-established policies and procedures for generation interconnection, that is, for resources injecting energy to the transmission networks, a supercharger (generally) would act only as a customer load, taking energy from the network, and reselling that energy to users of the supercharger stations. FERC small generator Interconnection policies and procedures would seem to apply if the supercharger site acted as a resource, that is, injecting energy to the networks. Again, simple enough.

However, this setup would seem to make the supercharger site look and act more like a regulated utility or competitive retail energy supplier, buying in wholesale markets and selling retail. Not impossible by any stretch, but it seems unlikely that Tesla supercharger sites would have interest in bearing the enormous expenses and bureaucratic drag caused by regulatory culture. All states have laws that define 'public utility' and all related responsibilities. Lots of downside, very little upside. California has had its experience with competitive retail and VFEA leave that topic alone.

This response covers possibly your second question regarding dedicated lines to supercharger sites. Think $$$$, siting and permitting, NIMBY, and more layers of regulatory goo than you can might want to imagine, impractical and unrealistic for a 1 MW load (and it very low load factor).

Unspoken but lingering in the background of your questions, the hypothetical of widespread power outages that could disrupt service, for example, the 2011 San Diego blackout. Serious inconvenience to say the least, mighty risky for the EV fleet of emergency vehicles such as ambulances and fire trucks. Far more serious system risks in regions with weather (ice, wind, lightning) than in California, but something in need of attention sooner and not later. If EV saturations in 2025 in 'weather regions' begin to involve a few million vehicles, local distribution networks will need some very careful attention, involving distribution network reenforcements such as undergrounding large distribution feeder lines to manage outage risks. Given the pace of utility regulatory culture, 2025 is not far away. How much protection is enough, tolerance of retail customers for ever-upward rates, and how state regulatory policy and practice may address the issues ... all mysteries that will reveal themselves in coming years.