More Efficient Power Consumption for Hybrids

True, but how many people currently have hybrids?

The article in the link admits that total pollution would go up because of the power plants primarily burning coal; only urban pollution would decrease because the plants are located outside urban areas for the most part. Meanwhile, I live in New York and the air in the prevailing winds from the midwest is already highly polluted before we even get it ... so that will only get worse.

Meanwhile, the government is worried because the power grid is barely functional now that power is no longer necessarily generated locally but moves over the grid based on the cheapest way to satisfy demand. Although if it truly is off peak to charge the cars then it might help.

Anyway without a comprehensive energy policy, its all just talk.

In a thread some time back I started a discussion on the cost of electrical energy compared to the cost of energy from petrol. Interestingly for Sydney Australia the break even point was $1.16/liter. In other words while petrol was less than this price it would be more economic to use petrol to generate the electricity than to get the electricity from the grid.

Now in the calculation I didn't take into account discounts for off peak electricity and the intrinsic losses in the transfer and storage of electric energy in batteries nor the inefficiencies in internal combustion engines So I thought it might be worth doing the calculation again taking all these into account.

A liter of petrol contains about 34 Mj of energy so lets say we can run the engine in our hybrid at maximum efficiency and we get a 55% conversion of thermal energy to mechanical energy and the generator gives us about 80% efficiency then of the 34 Mj in a liter of petrol we get at the battery terminals

34 Mj x 55% x 80% = 15 Mj

The next question is how much dose it cost to get the same amount of energy to the battery terminals from the grid. The battery charger would be normally be about 80% efficient and the cost of off peak electricity in Sydney is around 5¢ per kilowatt hour then

1 Kwh = 1,000 w x 3,600 sec = 3.6 Mj = 5¢

Therefore

5¢ x 15 Mj / 80% / 3.6 Mj = 26¢

If we used normal electricity which costs around 12¢ a Kwh the cost works out as

12¢ x 15 Mj / 80% / 3.6 Mj = 62.5¢

So there you have it for Sydney Australia it would be cheaper to use off peak electricity while petrol costs more than 26¢ a liter and ordinary peak demand power if the price is above 62.5¢ a liter and since petrol currently costs around $1.16 a liter then it is absolutely worth charging the batteries in your hybrid car from the mains whenever possible.

Perhaps others could do the calculation for their locations, compare it to the price of petrol and post the results here? The equation is

Electrical Equivalent of 1 Liter of Petrol = Cost_{1 Kwh} x 15 Mj ÷ 80% ÷ 3.6 Mj

You say: "Adding plug-in capabilities is around $100 for hybrid vehicles."

In fact, kits for Priuses that convert to plug-in capability are around $8,000 - $12,000. (The Hymotion system, for instance, is projected to be $9500, installed.)To make a plug-in hybrid, you need to add not only a high-voltage battery charger, but also the batteries to charge. The standard on-board batteries in a Prius are insufficient to run the car for long on batteries alone. The kits add batteries enough for a round trip of about 30-40 miles.

In the US, using power from the grid to charge a hybrid or full electric car is, right now, at the break-even point vs gasoline: One kilowatt hour is about $0.10. If charging efficiency is 80% and motor/control efficiency is similar, then the effective cost per kilowatt hour at the wheels is $.15. A gas engine uses about .068 gal/kw/hr. To get the same cost per kilowatt hour, then gas has to be about $2.20 -- its current price. Therefore, if gas remains at its current price, you'd never payback any of the investment to convert a Prius to plug-in. The price of these kits would have to drop dramatically to make their use cost-effective even with $5.00/gal gasoline costs. (An interesting difficulty in their cost justification is that you would have to drive many many miles per year to save enough. However, even with 40 mile range, used every day to commute, you could only accumulate 10,000 miles per year.)

Ecologically, electricity from the grid has a very slight advantage, using a little less fuel to produce one hp at the wheels. Of course, the more benign the generation means, the more significant this benefit will become. If all our energy were generated via hydro, wind, and solar, then electric vehicles would be clearly superior, ecologically.

Actually, it had been a while since I looked at the Hymotion site. They are now claiming 50 km (30 miles) under optimum conditions.

"Driving range will depend greatly on driving style and road conditions. Under optimal conditions the L5 kit will provide a ZEV range of approximately 50km on the Toyota Prius. Heavy use of air conditioning can shorten this range by about 25%-30%."

So 30 miles is the best you could hope for, meaning my gloomy cost justification above is unrealistically optimistic. Perhaps, if one were serious about using a Prius in plug-in mode, a do-it-yourself approach with cheap lead-acid batteries might be more feasible. (Of course you'd be left with virtually no trunk, and possibly dangerous handling, in addition to the voided warranty that comes with the Hymotion kit.) (The Ford Escape version of the Hymotion kit seems completely ludicrous: the Escape Hybrid gets worse mileage than my ordinary Honda Accord, which is on a longer wheelbase. You can't make a silk purse out of a sow's ear.)

Just a sad (for me) note: Here on Long Island, New York, residential electricity is just under $.20/kwh !!!!

Well we built a big nuclear power plant some years back .... Shoreham.... then dismantled it without ever putting it on the grid. I will probably be dead before we pay it off!

Don't ever think that New Yorkers are sophisticated ... they only think they are. Just look at our state government in Albany!