⚡ Electricity: A Ubiquitous Fuel Source
Given how common it is for us to get into a car and drive somewhere, it is hard to not overlook the vast amount of infrastructure needed to provide the fuel that makes the vehicle go. For over a century we have perfected the task of prospecting for, extracting, transporting and refining fossil fuels for cars with internal combustion engines. As we look at all the alternatives to fossil fuels, electricity presents a strong case for deserving the type of investment fossil fuel has enjoyed.
One advantage that electricity has over other alternative fuel sources is that a vast distribution and generation network already exists, in the form of the electric power grid. Therefore, refueling an electric car should be easy and possible nearly everywhere?
In this article we talk about the challenges of “fueling” an electric vehicle and some technological concepts behind it.
🦺 Why Does an EV Need Special Charging Equipment?
Your toaster is an electric appliance and it does not require any special equipment besides a power cord to connect to a wall socket, so why is an electric vehicle any different?
It turns out there are a number of ways in which “plugging in” an EV is a lot more complicated than plugging in a toaster:
- Your toaster is incapable of drawing so much power that it will overload your wiring and cause the circuit breaker to trip.
- Nobody will accidentally try do drive off in a toaster that is still plugged in.
- You won’t ever plug in your toaster while it is outside, in the middle of a rain storm.
- Your toaster is perfectly fine running its heating coils using AC power.
In order to address these issues, dedicated Electric Vehicle Supply Equipment (EVSE) is needed, to enable the safe and reliable charging of electric vehicles from the power grid. At the very minimum, the EVSE is responsible for
- Safety of the charging process, by not energizing the connector unless it is plugged into a vehicle’s charging port and some basic electrical safety checks have been performed. It will also de-energize the connector if an electrical fault is detected and when the vehicle is done charging.
- Reliability of the charging process, by indicating to the vehicle how much power the grid is capable of delivering, so that the vehicle does not attempt to draw more power than can be delivered, thereby tripping a circuit breaker or overloading the electrical wiring.
While this addresses the first three of the challenges described, the fourth one warrants further elaboration:
🔋 AC vs. DC Power
The electrical grid runs on AC power, where the flow of electricity changes direction many times a second. This enables relatively simple equipment (like a transformer) to convert electricity from lower voltages to higher voltages and back, for efficient transmission over long distances.
The reversible electrochemical processes that enable the charging and discharging of a battery consume or produce DC power, where the direction of the flow of electricity does not change over time. Also, batteries can only deliver power at a certain voltage, which depends on many factors, some of which also change over time, such as the battery’s state of charge or the amount of current being drawn from the battery at any given time.
To complicate matters even more, most electric vehicle drive trains use motors that require some form of AC power, the exact specification of which also varies over time, depending on conditions such as motor rpm and power demand.
Therefore electric cars contain power electronics: When the vehicle is in motion the power electronics acts as an inverter taking DC power from the drive battery and converting it to the correct form of AC power for the electric motor, to meet current driving conditions. Also, an often overlooked fact is that the inverter will also output some DC power at lower voltage, to keep the vehicle’s 12V car battery topped up, that electric vehicles still rely on.
🔌 Level 1 and Level 2 Charging
The in-vehicle power electronics are also designed to accept AC power from the grid – either in the form of 120V household electricity (like your toaster) or in the form of 240V (like your central air conditioner) and convert it to DC power suitable for recharging the drive battery.
In this case only relatively simple equipment is needed to interface with the grid when charging. EVSEs that enable this are available in a price range from a couple hundred dollars (for a mobile unit that plugs into your 120V or 240V outlet) up to a few thousand dollars (for smart network-connected commercial-grade equipment).
This kind of EVSE is known as Level 1 Charging equipment (120V) or Level 2 Charging Equipment (240V).
🏎️ DC Fast Charging
Present-day electric passenger vehicles with a range of around 300 miles are able to replenish an empty drive battery on a Level 2 charger overnight, drawing power at a rate of around 10kW (probably about two to three times the consumption rate of your central air conditioner when it is running).
While this covers everyday use cases, where just a top-off is required after a day’s worth of driving, an eight hour charge after every 300 miles driven would be prohibitive when attempting to cover long distances in an electric vehicle. – In order to enable this use case, we need much faster charging rates.
In order to achieve higher charging rates, why can’t we just scale up Level 2 charging and allow the vehicle to draw more power from an AC source, that supplies it maybe at a higher voltage?
In order to get charging times down to minutes rather than hours, we would need equipment that is able to handle the conversion from AC to DC at a power level that is ten to twenty times higher than on a Level 2 charger. This would require electronics that are more expensive, bulkier and require a substantial amount of cooling, just for the purpose of recharging the battery fast.
Therefore, the solution that engineers have to come up with is to place the power electronics that enable such fast charging rates outside the vehicle and leave it stationary. This is referred to as Level 3 or DC Fast Charging Equipment. It supplies DC power to the drive battery directly, mostly bypassing the vehicle’s own electronics, which will still monitor power flow and request the appropriate amount of current from the DC Fast Charger to be delivered at any given time, in order to recharge the battery as quickly as possible, safely.
⚖️ A Case for Ubiquitous Level 2 Charging Infrastructure
If DC Fast Charging enables rapid replenishment of a vehicle’s battery, why would we not just put DC Fast Chargers everywhere?
As outlined above, DC Fast charging equipment is bulky and expensive. While a commercial-grade Level 2 charger can be installed for a few thousand dollars or less, DC Fast Charging equipment will likely be a six figure investment for every charging spot, not including the cost and time required for a service upgrade.
When the much higher initial cost and higher electricity cost (because of the demand spikes that DC Fast Charging can generate) is passed on to the driver, the “fuel” dispensed from a DC Fast Charger will likely be substantially more expensive than the retail cost of electricity from the grid, making DC Fast Charging only a good proposition in cases where Level 2 charging is too slow:
This would be the case when we try to cover a distance that is larger than the vehicle’s range on a single charge. Drivers are likely fine with paying a premium for only taking a short twenty or thirty minute break to top off their battery, rather than waiting for hours at a Level 2 charger. Another good example would be vehicles that are used for commercial purposes, such as taxicabs or cars used to provide ride share services: While each trip taken is well within what can be covered on a single charge, the total number of miles traveled per day can exceed this limit and hence a quick recharge is required that can put the vehicle back in service within minutes rather than hours.
In many use cases – where cars are parked for several hours, such as at home overnight, or at the workplace – Level 2 chargers appear to be a better solution not just form a cost but from a user experience point of view: If a car is parked for several hours, “plug in when you arrive and drive off with a topped off battery” is a much better proposition than “remember to come back in half an hour to move the car out of the DC Fast Charging spot, or pay idle fees”.
Also a study found that the number of electric vehicles on the road is growing much faster than the number of (public) places to plug them in. If this problem is not addressed, the transition to electric transportation is at risk of slowing down.
Making Level 2 charging ubiquitous and available at a low cost in places where people work and live/rent will also ensure that lower income communities are not left behind as the transportation sector electrifies and gas prices soar.
In order to support socially-just transportation electrification, Station A has begun to evaluate commercial as well as multi-family residential buildings for their ability to support Level 2 charging infrastructure within the limits of their current grid connection. For a commercial building owner this means you can now turn to Station A to get some guidance as to how to improve your building’s appeal to your tenants as well as contribute to our transition to zero-emissions transportation by installing Level 2 charging infrastructure.
🤔 Why Consider EV Charging for Your Commercial Building?
As mentioned above, there are a number of market and policy factors that will continue to drive demand for EV charging stations. Commercial building owners and business operators are going to find that providing EV charging stations for their employees and tenants will soon become an amenity as essential as restrooms.
EV charging also pairs nicely with an on-site solar installation: Excess generation does not have to be exported to the grid, but can be used to charge vehicles. Not only does this ensure that the EVs are being refueld using electricity generated from a renewable energy source; it is also desirable from a grid management point of view, particularly in regions where there is a large amount of solar power online already.
🔍 See if EV Charging is a viable option for your building.
Enter an address on stationa.com to view a building’s Clean Energy Grade. Your building’s grade will include an estimate the number of EV (Level 2) charging spots your building could support without an electrical upgrade. Tap the “Go Green” button to receive your clean energy buyer’s guide with information about how to take the next step in your clean energy journey.
