V2G: Benefitting the Owner and the Grid
Did you know that the energy in electric vehicle (EV) batteries can be a resource with value over and above making the EV move? From the simplest case of powering equipment at a worksite to the most sophisticated utility managed operations, being able to utilize the power in EVs has huge potential.
But unfortunately, there is a lot of confusion about EVs and charging created by industry terminology. Here’s some of what the public needs to know.
Much has been written about the value of V2G or Vehicle to Grid. Numerous studies have shown that if EVs were bidirectional and could give up the electricity stored in their batteries when it was needed, it would have multiple benefits both for the owner and for the electrical grid as a whole.
At the local level the owner of a bidirectional EV could use electricity from the EV battery as an alternative to buying expensive electricity from the utility at times when the utility rates were very high. Electricity stored in the EV battery could also serve as an emergency reserve, particularly in areas subject to power outages.
On a wider scale, if a utility were able to call on the stored electricity in many plugged in EVs by interacting with the chargers over the internet they could serve as a giant battery that could stabilize the grid at times of need.
V2G, V2H, VIG, G2L – Acronym Confusion!
The discussion of these possibilities is made more difficult by the proliferation of acronyms that are not necessarily used consistently. The literature variously refers to V2G, VGI, V2X, and many other acronyms that we will attempt to clarify here.
VGI & V2G
The generic term for any interaction of EVs with the grid is VGI or Vehicle Grid Interaction. The term V2G for Vehicle to Grid should be reserved for applications where power is actually flowing from the EV onto the grid through the charger (referred to as EV Service Equipment or EVSE.). This distinction is important because to feed power onto the grid it is not enough to produce the correct frequency and voltage. Regulations require that any device that is going to add power to the grid must be capable of communicating with the utility to make adjustments as required for grid stability.
The two meanings of V2H
This requirement is the source of the confusion around the use of the term V2H for Vehicle to House (or Home) and its companion term V2B for Vehicle to Building. These are both used to describe two very different use cases.
1. “Blue Sky” operation
In one case V2H means the building is still connected to the grid but for economic reasons the owner would prefer to use electricity from the vehicle battery rather than buy it from the utility. This might be because the time of use rate is higher than the cost of charging the vehicle at some other time or place. If the building is subject to demand charges any plugged in vehicles can be called upon to meet peak loads to mitigate demand peaks.
The point is that the building is still connected to the grid, but the EVSE is drawing just enough electricity from the EV’s battery to meet building demands without running the electric meter backwards. Although there is no flow of electricity to the grid , the utilities and regulatory agencies take the view that because there is electrical continuity between the EVSE and the grid this must be licensed in just the same way as a V2G application.
Because such an installation must meet all the requirements of a V2G system they are sometimes referred to as V2G even though no electricity reaches the grid. In an environment where the reimbursement for running the meter backwards is negligible this feature might be preferable to V2G. EVSE devices with this feature are currently available for heavy duty vehicles and are just coming on the market for passenger vehicles.
This mode of operation is called parallel operation because the EVSE is operating in parallel with the grid. The EVSE is said to be in grid following mode because it is matching the phase and frequency of the grid. Colloquially this is called “Blue Sky” operation because the equipment is not being used during a disaster (“Black Sky”) in contrast to the other mode which is also called V2H.
2. “Black Sky” Operation
The other mode of operation also often referred to as V2H is islanded operation which is intended for emergency only use. In this case the EVSE comes with a disconnect switch which can isolate or “island” the building from the grid. Once this is done the issues of grid following and responding to utility messages become moot. EVSE devices which can operate in this mode are said to be grid forming because they must generate their own frequencies.
If an EVSE device only operates in this emergency mode disconnected from the grid then it is exempt from the regulations governing grid connected devices. On the other hand, some bidirectional EVSE devices are dual mode, meaning they can operate in grid following mode if the grid is up and they are connected, or disconnect and switch to grid forming mode if the grid goes down.
V1G & V2L
People have extended the nomenclature in other ways. As a back formation the term V1G is used to mean EVs and EVSE that are NOT capable of V2G. It refers to controlling when EVs charge to manage the load on the grid.
The term V2L means Vehicle to Load, indicating the vehicle has AC outlets which can be used to power any device that can be plugged in subject to the limit of the vehicle’s output power. This is a source of confusion because even some salespeople do not realize that this power does not meet the requirements to connect to house wiring or the grid. Attempting to use the V2L outlets on an EV to energize the wiring of a house, whether or not the grid is operating, is both dangerous and illegal.
Conclusion, V to Everything
Finally, to reduce (or perhaps increase) the confusion the term V2X was coined as a generic term for Vehicle to Everything to cover all the usages described above when the author does not want or need to be specific.
The bottom line is that the energy in an EVs battery is a resource that has value over and above making the EV move. From the simplest case of V2L powering a picnic to the most sophisticated utility managed V2G operation that generates revenue to the owner, having a bidirectional EV adds value to the vehicle.
CLICK HERE TO DONATE IN SUPPORT OF FREEDOM OF THE PRESS AND OUR NONPROFIT NEWSROOM