• PEVs
  • Energy Storage Systems
  • Battery Energy Storage
  • EV Charging

Thinking Creatively About Energy Storage

Scott Shepard
Jun 06, 2019

EVs 4

The energy storage potential of plug-in EVs (PEVs) has long been a tempting prospect for the electric power sector. PEV batteries sit idle for most of the day; these could be tapped to balance grid supply with demand. As intermittent renewables like solar and wind satisfy larger portions of grid supply, demand for balancing assets like batteries will grow more desirable. Vehicle batteries are particularly attractive because they come with far fewer capital costs than dedicated balancing assets like natural gas combined cycle generators or stationary batteries. Batteries are also quick and accurate in responding to balancing commands relative to other balancing assets. This means more battery balancing will make the grid operate more efficiently.

Why Isn’t This Already Common?

While exciting, tapping vehicle batteries for such purposes has proven difficult. Bidirectional chargers that enable vehicles to discharge back to the grid have been costly custom requests for pilot projects until recently, when the charging industry began commercializing offerings. Automakers have been hesitant to enable bidirectionality. They’re understandably concerned that increased use of the battery for grid services could diminish its capability to provide its primary purpose: motive power. Additionally, there is little demand from consumers for bidirectionality, making the investment for OEMs difficult to justify. Despite this, automakers are progressing with bidirectionality. Some vendors see potential for this capability to eventually be a competitive advantage.   

Other Obstacles

There are also challenges concerning critical user data points like battery state-of-charge and time of departure, and complications for PEV owner compensation procedures that will vary from market to market. There are movements to overcome each of these issues, but there may also be a simpler way to go about this.

Many charging station deployments require a capacity upgrade to the feed-in electrical circuitry or local distribution grid assets. Depending on the size of the charger (measured in kilowatts) such upgrades can be costly, and installations will take time. There is also concern regarding property owner electricity costs. The use of chargers may coincide with peak monthly property usage and exacerbate already costly demand charges. There are a few different solutions to bypass these issues. An increasingly interesting one is the use of energy storage devices.

Energy Storage Potential

Colocated at charging stations, energy storage can be used to avoid feed-in infrastructure upgrades and to buffer and shift PEV charging to reduce or avoid additional demand charges. While the addition of energy storage increases overall equipment costs, in some cases it may reduce overall installation costs and speed the installation process. FreeWire Technologies has pointed out these potential advantages with its latest offering, designed to deliver 120 kW from level 2 charging infrastructure.

A positive market response to such a solution could place significant distributed energy storage capacity in grid markets that would theoretically be much easier to tap than the vehicle battery. The storage could be ideal for second life EV batteries, but technically it doesn’t have to be batteries at all. Chakratec has demonstrated as much with its flywheel solution. An added benefit here is that remaining uncertainties concerning battery durability would be avoided via a mechanical solution.