On today's episode. new bi-directional tech lets evs power homes.
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Electric vehicles have been around a long time. The first practical examples were produced in
the late 1880s, and in the early decades of the automobile it was unclear whether battery,
electric or internal combustion engines would dominate the industry.
Heavy lead acid batteries and inefficient, poorly controlled motors allowed gasoline powered
vehicles to rapidly overtake EVs in performance, and by 1910, EVs rapidly fell from favor.
Interest in electric vehicle development, however, has been continuous. Now, propelled by Tesla,
all major automakers are launching large numbers of new electric vehicles.
Fueling those vehicles, of course, means public and home charging,
which requires connection to an electric utility’s power grid.
Like gasoline, the energy flow is one way: into the vehicle. But does it have to be this way?
General Motors and a California electric utility, Pacific Gas & Electric,
don’t think so. They have announced a collaboration to use GM electric
vehicles as backup battery systems for home use during grid power interruptions.
PG&E is a California utility, and California has experienced multiple grid outages due to
wildfire damage to distribution infrastructure and the need to black-out service in high-risk
areas preventatively, as high winds and powerlines are themselves a fire risk.
So-called bi-directional charging, however, adds system complexity.
Household service in America is 60 Hz AC at a nominal 240 V single phase,
and the current must be rectified for electric vehicle battery charging. Running the process in
reverse requires that DC current be fed through an inverter to generate alternating current,
and the AC must have sufficient voltage and waveform regulation to closely match
the power quality of grid electricity. A further complication is the need to automatically handle
the switchover from grid to EV-sourced household power, then back again as grid power is restored.
Bi-directional charging is not a new idea, but American utilities face a particular challenge:
in the absence of a national standard, will backup power be controlled in isolation from the grid,
or centrally controlled to allow the potential for battery feed into the grid with the possibility
of net metering and load leveling for neighborhood or even citywide systems.
Software will be the key, and the GM/PG&E pilot will test
software-defined communications protocols. The joint team plans to work very quickly,
with pilot testing with consumer trials by the end of the year.
Why so fast?
The electric car industry is experiencing a sort of “gold rush” culture, with automakers jockeying
for volumes to establish de facto standards in areas like control software and battery chemistry.
Electric utilities that can develop workable control methodologies can
establish standards that will allow all automakers to build compatible EVs.
As electric vehicles increase in popularity, the benefit for power companies is considerable.
Net metering already exists in some jurisdictions for customers equipped with solar panels, but some
experts warn that increased use of electric cars will create difficulties for utilities,
requiring either increased baseload capacity or more robust load leveling technology, or both.
Grid-scale battery storage is already in use for this purpose, but hundreds of
thousands of EV batteries, all grid connected and operating through software-controllable inverters
could provide a sort of remote, pay-as-you-go load management solution for electric utilities.
Ford has developed an independent bi-directional system for the upcoming F-150 Lightning electric
pickup, and PG&E is also working with that company on bi-directional charging.
The amount of charge stored in California’s garages and driveways
must be a tempting resource. How tempting? One in five electric vehicles sold in the
United States are based in PG&E’s service area, representing 6,600 MW of available capacity.
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