Before I start in on more calculations, I realized there was one interesting feature to this system I proposed. Since the car is following the cable in the road
, it doesn’t really need you to steer! You put some radar in the front bumper to maintain a proper following distance and you can just have to car drive itself and notify you when you get close to your exit. I suspect this would result in significant decreases in highway fatalities, considering the distraction levels for the modern commuter, especially if auto drive was required for freeway vehicles.
I've put all my references at the end.
The next part is to calculate how many cars are on the freeway at rush hour. Surprisingly, I couldn’t find a ready number for that, so I went back to the envelope. I found a reference that the lane capacity of a freeway is around 2,300 cars per hour. At 60 MPH, that works out at about 138 cars per mile or 826 cars on 6 lane freeway (3 lanes each way). The 4 lane road
would be about 551 cars. Since I previously found out that there are 75,000 miles of freeway in the US, I assumed 10,000 miles of 6 lane freeway and another 10,000 miles of 4 lane freeway and then threw in another couple of million cars for the rest of the freeway system which comes out to around 15.8 million cars.
But what do I do about freeways that have more cars than their capacity? As near I can tell, the cars would actually use less electricity because they are moving slower and generating less wind resistance. Read “Sustainable Energy – Without The Hot Air” by David MacKay if you are interested in the math.
There are around 235 million cars and trucks in the United States, not including larger commercial vehicles and stuff. This means that 15.8 million is only 7% of the total. I figured not everyone commutes at the same time and a lot of them are on surface streets and some people actually car pool and besides if more cars are on the freeway, then they don’t use more electricity and if someone knows the actual number, then they will correct me.
Next I had to figure out how much electricity each car would use. After looking at the specs on a bunch of EV, I came up with 10KW per car by assuming significant weight savings from a smaller battery pack. I suspect the actual number is higher, since I want the cars to cruise at about 60 MPH. If people in Los Angeles could average 60 MPH during their freeway commute, they would start naming their kids after me. Come to think of it, with the auto drive function, their kids might be conceived during their commute. I’m sure it has been managed a few times, without the auto drive.
Anyway I multiplied the two numbers together and came up with a total of 158 Gigawatts. At this point, I had what might be referred to as a Doc Brown moment, and used some words not suitable for a family forum. Remember afternoon rush hour actually overlaps the peak electricity consumption point of the day. If I want 158GW, then I have to generate it. The whole nameplate capacity for the United States is around a Terawatt and actual average power generated is less than half that (464GW).
I’m pretty sure I can’t get peaking power for less than a $1 a watt. Actually after adding in the rest of the plant and the power distribution, I’m certain I can’t do it for a buck. And I need another 160 billion. Suddenly the power plants cost 6 times as much as the whole freeway system and probably over 10 times and I’ve got a system that costs over 200 billion and probably over 300 when the usual pork is added in. This might still be worth work doing, but isn’t exactly cheap.
This annoyed me, since in my previous post, I eliminated Global Warming and put a dent in International Terrorism for 25 billion. How could I be so far off.? I thought I remember reading that we could convert all our cars to EVs without adding any electric
I found the paper and skimmed it. What it actually said was that we could have one EV per household without adding additional generating capacity. They assume that the charging would use 1.625 KW for 8 hours to add 13KWh to the battery. They didn’t actually calculate it for the whole country, since they were using Cincinnati and San Diego for their examples. There are around 100 million households in this country, which works out to 163GW to recharge the batteries for 100 million vehicles, which would be 43% of the total cars and light trucks in the country. Technically this doesn’t require new generating capacity, but tends minimize that whole peak/off peak differential , so the electricity gets more expensive or we build a lot more off peak power. If we want to convert most of our cars and trucks to electric
power, then I’m not sure if peaking power is even an option.. I’d don’t think there is enough Natural Gas to do it.
I guess my next part will be to calculate if most of the electricity comes from Natural Gas, then does it make sense to use an electric
car versus running one on CNG?References:http://www.state.nj.us/transportation/eng/documents/RUCM/Section3.shtmhttp://www.inference.phy.cam.ac.uk/withouthotair/cA/page_254.shtmlhttp://en.wikipedia.org/wiki/Toyota_RAV4_EVhttp://en.wikipedia.org/wiki/General_Motors_EV1http://www.eia.doe.gov/cneaf/electricity/epa/epat2p2.htmlhttp://www.eia.doe.gov/cneaf/electricity/epm/table1_1.htmlhttp://www.euec.com/documents/pdf/Paper_5.pdf