Its easy to say that we need flying cars or a cure for cancer now. But in this blog entry I’ll go over and show you why EREVs (extended-range electric vehicles) could have such a huge impact, both on a per car basis and from the nation’s perspective.
So we’ll start with a few bits of information that form as the basis for our assertion that EREVs are needed badly.
First, we assume that the average person drives about 12,000 miles per year. Even is a somewhat irregular driving pattern that’s about 40 miles per day six days per week.
Second is the amount of driving that will be done on gas after the battery runs out. I’ll assume that to be an amount to be 1/6th of the total miles driven at 12,000 MPA (miles per annum, or miles per year). In the case of the average driver, we’ll assume thats 2,000 miles per year. At 15,000 miles per year, thats 2,500 miles per year. From there, we run into the limit of driving time and charging time. There will be limited recharging at work, for those with jobs that don’t involve driving all day. So we’ll fix the maximum miles/day on electric only is 50 (or about 18,000 miles per year).
Ok, from there we’ll start with 12,000 miles per year averaging 40 miles six days per week, and 1/6th of the miles being on gas. For a standard vehicle driving 12,000 miles per year at 25mpg, it results in the consumption of 480 gallons of gas. There is some ethanol using in the consumption of that gasoline but its usually limited to metro areas in winter. Switching to an EREV would result in the consumption of gasoline for only 2000 miles per year.
Here is where the math gets interesting. If the internal power source (engine) in a perspective EREV is 30% efficient (since it runs at a constant speed and there is no transmission or other system loses – just charging the battery), a gasoline engine would produce about 11kWh of energy. If it were E85, it would produce about 7.2kWh based on the BTU to kWh conversion minus losses. This results in about 27.5mpg and 18mpg respectively. For reference, the current MPG for the US passenger vehicle fleet is about 17 MPG.
The 2,000 miles traveled on gas or E85 would result in 72 gallons of gas or 111 gallons of E85 (which is actually 17 gallons of gas and 94 gallons of E85). So in the gasoline case, we’d reduce our consumption on a per car basis by 85%, and in the E85 case we’d reduce our consumption by 96.4%. This is by far the most important fact to take away from this article.
Of course, those numbers are on a per-car basis, and it would be 20 years or more before we could cycle out every existing light duty passenger vehicle to an EREV, and of course, over those 20 years we’d see various improvements such as further distances on electricity and other vehicle types (large SUVs and trucks).
The other factor in all this is the electric grid and where are we going to find that much power. A study I referenced in an earlier entry shows that with just the current power plants and limited recharging times between 6pm and 6am we could provide enough power for 42% of the US light duty passenger vehicle fleet. This would take at least 10 years to produce as many cars starting in late 2010 or 2011, and its quite possible that in that time we could see large advancements in solar and wind deployments that would dramatically effect how the grid works (peak demand, etc).
But the overwhelming numbers above show that we must start now. We need to start planning for cars, for batteries and for the infrastructure.
For every one million EREVs we put on the road, we will reduce our oil consumption by 44,500 barrels per day assuming they’re filled with E85. It may sound like a lot, but the US uses about 23M bpd, with about 13M of that amount being used in passenger cars and light trucks and SUVs, which is about 0.37% of consumption.
So that means we’re going to need to build a ton of vehicles to make a dramatic impact. There are about 250M cars on the road, so to replace a quarter of those we’d need 62.5M cars, which would save about 2.78M bpd or 23% of consumption. How long would it take? Even if you were to figure a 50% year over year growth rate, starting with 25,000 cars in 2011, we wouldn’t approach that figure until 2028, and at a 100% growth rate (doubling every year) it would take until 2022.
Every car will need about 15-16kWh of Li-Ion cells. For context, the average battery in a laptop has anywhere from 40-80Wh of energy storage (0.25-0.5% of the batteries in a car, or 200-400 batteries). Now the interesting thing to note is that GM’s spec for their EREV, the Volt, actually runs the battery between 85% and 35% (most likely due to battery lifetime considerations), so each recharge is about 8-9kWh for 40 miles, or aobut 200Wh/mi (fairly good and wlll definately require regenerative brakeing).
Finally, one of the benefits to EREVs and PHEVs over pure EVs is that you can recharge the battery overnight or while you’re at work – in just about 4 hours – from a standard 120V/20A outlet (8kW of energy, .85 recharge efficency factor). By using a 240V/40A outlet like you might have for a large appliance like an electric dryer, you can cut the recharge time down to about an hour.
Possibly Related Posts:
- Powertrain 2030: Vehicle Propulsion in 20 years…
- Brightsource to build nearly 1GW of Solar Thermal in Nevada
- California utilities invest in efficiency instead of new power plants
- Nissan to Lease LEAF Battery
- Western Governors’ Association Identifies Renewable Energy Zones
- Solar PV: Can it Scale Up? A View From the Grid…
- Jet Fuel From Camelina Plants
- Hitachi’s future EV battery due sometime around 2015
0 Responses
Stay in touch with the conversation, subscribe to the RSS feed for comments on this post.