Short version:
Hybrid battery-electric/CNG vehicles as a distributed, grid-connected load-balancing and on-demand generation system, managed by the utility company, by a price-based realtime spot market, decentralised down to the local substation level.
Longer version:
One of the objections
to the widespread deployment of electric or plug-in hybrid vehicles is the load this will place on the electricity grid, specifically at its most tenuous extension, the consumer/ neighbourhood end.
One of the objections to the widespread exploitation of (some) renewable energy sources is their intermittency, and the consequent need for, and cost of, some form of load balancing, either as energy storage (batteries etc) or excess, on-demand generating capacity.
Hello two birds, have a stone.
You drive a battery-electric hybrid vehicle, containing batteries, an electric motor, a compressed natural gas (CNG) tank, and either a fuel cell (series hybrid), or a combustion engine (series - separate generator, or parallel - drives electric traction motor as a generator).
When you park your car at home or at work, it hooks up to:
• the town gas supply via a compressor
• the electricity grid
• the building's hot water system
• the LAN.
The first thing that happens is a data handshake/"hello world" between the vehicle, the building hot water system, the local electricity substation, and the local town gas substation. The second is that the onboard computer checks out the state of charge of the battery pack, and the fill level of the onboard CNG tank.
The third thing that happens depends on which management model you adapt. I'll describe here two models: a market based one, and a centrally-planned one. As electricity grids are increasingly moving towards realtime markets as a mechanism for demand management, I'll explain that one first, and in more detail.
In a market model, the local substations give a present-time and local-area spot price for both a kW of electricity and a litre of NG. This is already baked for electricity. When the electricity spot price is low (ie supply > demand) the vehicle buys electricity from the grid, and uses it to top up its own batteries. This provides a local demand management buffer to the grid. When the price is high (supply < demand) it sells electricity back to the grid, either by depleting its own batteries or by purchasing NG to run the generator, or both. The spot price for NG is a factor in calculating which is the optimum source to draw on at any one time.
Whatever heat is generated by energy conversion onboard the vehicle is converted into hot water by the link between the vehicle's cooling system, and the building hot water system.
A parking garage or workplace carpark may have its own substation, and the HVAC/hot water controller would be another independent bidder in the market. At home, the substation would cover a neighborhood. A meta-market operates between the substations to balance demand at the next level up, and so on up to the backbone grid.
The vehicle computer balances the spot price (of NG, hot water and electricity) against expected user demand (ie, needing a full battery pack and CNG tank by 8:00am/5:00pm), and against known patterns of rise and fall in supply and demand (ie, household power demand generally drops at night). It can play hedge games and futures trading against these expected patterns, and determine when during the diurnal cycle is the best time to purchase or sell its resources. It also learns the patterns of user demand for mobility, so it can hedge against them. This feature can be over-ridden by the user, who for example needs a full tank and batteries for a 4am airport run, and is willing to pay slightly more on that day to ensure availability.
In a "command economy" model, the vehicles are remotely managed by the utility to either dump and store excess electricity or supply electricity from batteries or town gas, as per local, realtime supply and demand.
I think a combination of the two models may work the best. The vehicles (and optionally associated infrastructure) may be leased to the user at a fixed cost, with a maintenance contract built in, and the utility buys and sells NG/electricity to/from the vehicles as required. The user pays only their lease costs and mobility costs (kW/litres actually used in transport). This would work best perhaps with large corporate or government fleets, where a "company car" is routinely provided as part of a salary package, at least as an initial roll-out and proof of concept. Bus and taxi fleet would also be worth investigating.
Standardization common amongst such fleets would simplify the provision of a standard vehicle designed to mate with utility infrastructure in the workplace garage. Because of the number of connections required (gas, LAN, electric, HW), an automated hookup system is likely to be necessary, even if these are integrated into a single umbilicus. Standardization will help enormously here, thus motivating towards larger fleets as a first point of deployment. Initial tests could be performed using a slightly modified production Toyota Prius.
At the other extreme, the user would pay (or finance) the upfront cost of the vehicle (and optionally infrastructure) themselves, and enter into a supply/demand contract with the utility. A middle ground would see the vehicles privately owned, and the infrastructure owned and operated by the utility.
At a rough guess, this works out financially advantageous to everyone. The user/fleet owner is assisted in amortizing the cost of the vehicle by taking a powerful, high-tech energy conversion plant which may other otherwise be only utilized for two hours per day, and giving it a productive income-earning capacity 24/7. The utility is assisted by spreading the capital cost of necessary load-management plant across a wide area, negating somewhat the need for upgraded trunk transmission infrastructure, and by sharing the financing burden of that infrastructure with the user.
It might - just, barely - work out possible for the utility to supply the vehicles for free or close to it, and charge only for miles.
As a further refinement: the data connection between the vehicle and utility can be wireless, 24/7, and wired into the GPS nav system. The utility and the vehicle can negotiate the most mutually advantageous routes and parking spots, taking into account departure point, destination, vehicle range, areal supply and demand, and the availability of charging stations.