V2G: Vehicle to Grid Power

Seth Insley CH 407H

Concept

Cars use large amounts of power – Far more than other power uses 750 GW electric vs 12 TW from cars – Must generate or store it themselves – Unused most of the time Average use only 1 hour per day Fuel cell, hybrid and battery cars generate power as electricity – Why not hook them up to the power grid?

Conventional View

V2G View

Examples

Use the battery in plug-in hybrid/battery cars to buy cheap power at night and sell during the day Use hybrid/fuel cell car to generate peak power Use either to provide ‘spinning’ reserve or regulation services

Benefits

Better utilize existing generation capacity – Will need to build fewer new electric plants – Allow better load balancing by diversifying the electric grid – Reduce transport load on grid by distributing generation – Increase grid reliability Provide income to car owners – Offset or reduce the cost of the car

Considerations

How will vehicles be connected to the grid?

How will this effect drivers?

Is this a cost effective way to generate power?

Infrastructure

Requires physical connection between car and grid – Only useful when parked – Could hook up at home – Could be incorporated into public charging stations or parking lots – Should be simple to set up, automatically handling payment, etc Just plug it in May also desire fuel connection: – Natural gas or hydrogen

Driver Experience

Primary Consideration: Will this affect range?

– Allow owner to easily limit extent of discharge/fuel use Will it be easy to set up?

Will it be sufficiently profitable to make it worth the effort?

– The car owner should not have to worry about this – Only sell power when profitable

Economics

Not worthwhile unless it returns sufficient amounts of money after expenses incurred – Cost of fuel/ electricity – Maintenance costs for Battery Fuel cell Engine – Effort required by owner

Economic Advantages

Very low capital costs – Car already bought Adding grid capabilities relatively cheap – Even so, costs roughly $60/kw Compared to $1000/kw for traditional generators Due to lower efficiencies, reliability Has freedom to buy/sell only when profitable – Much more responsive than traditional generators

Economic Disadvantages

Poor Efficiency – Smaller/cheaper generators are less efficient – Need more fuel to generate same power Requires relatively expensive fuels – Gasoline or hydrogen or natural gas vs coal – Cannot buy fuel in bulk

Economic Conclusions

Not suitable for baseline power generation – Cost of power to high vs. conventional generators ~5 ¢/kwH vs >10¢/kwH – Unique Advantages not used Suitable for – Peak power generation – Spinning Reserves – Power Regulation Economic analysis depend heavily on exact assumptions

Cost of generation

Cost per kwh Batteries (charged at base rate) – Lead acid $.23

– NiCad $.32

– NiMH $.45

Hybrid generating w/ gasoline $.20 Fuel Cell w/ H2 $.09-$.38

Peak Generation

Used when electricity needs are much higher than baseline – During daytime, hot/cold weather, etc.

Considerably more expensive than baseline – Often Generated by natural gas Low capital, high incremental expense – ~200 hours a year where > 50¢ kwh

Economics of Peak Gen

Not to slightly profitable for batteries – Depends on current power markets Can be fairly profitable for fuel cells – ~1k / year Less so for hybrids – ~.5k / year

Spinning Reserve

Generators ready to provide power in ~10 min Used to preserve grid stability if generators go down, load is too high Sold on contract basis – Ex. 1 Kw for a day – Payment even if not used – Extra payment if used

Spinning Economics

Profitable for all vehicle types – Batteries $10-$700 – Fuel cell, hybrid generating: ~$2000

Power Regulation

Used to keep frequency stable at 60 Hz Must be able to respond instantly 2 kinds – Regulation up – generating power – Regulation down – absorbing power

Regulation Economics

Batteries are ideal for this purpose – Up/down corresponds to discharge/charge – Has minimal effect on total charge – ~3k for lead acid – ~2k for NiMH – Actual degradation hard to determine Not profitable for other types

Market Size

All numbers for CA electric market ~300k battery vehicles for regulation 76k – 273k vehicles for spinning reserve ~ 734k vehicles at max for peak .5% – 5% of total light vehicle count Additional uses are likely in a saturated market – More reliability, renewable

Conclusion

V2G is a promising concept – Provides a cheaper way to provide many grid services Needs more detailed study Not hard to implement simply May play an important role in the future power grid

Sources

V2G research group at U of DE. “V2G: Vehicle To Grid Power” http://www.udel.edu/V2G/ Kempton, et. al. “Vehicle-to-Grid Power” http://www.udel.edu/V2G/V2G-Cal-2001.pdf

Kempton, Letendre. “Electric Vehicles as a new Source of Power for Electric Utilities” http://www.udel.edu/V2G/Kempton-Letendre 97.pdf