Higher voltage? Lower current?

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The first car I owned was a 1966 VW bug.  It cost me $750.  When I bought that car in 1977, I was the king of the world.  I was independent.   I could drive around wherever and whenever I wanted.  Now as I look back in 2022, this reminds me of the the current-versus-voltage tradeoff that has permeated everything in our lives ever since. 

This car which I bought from earnings washing dishes in a restaurant, had a stylish “1300” on the back cowling that communicated to anyone in Metric World that the internal combustion engine had a displacement of a whopping 79 cubic inches.  This was at a time when a long-forgotten family car, before my father died, had been a Dodge Polara with a V-8 engine with a displacement of 440 cubic inches.  (See photograph above right.)

For those who are keeping score at home, the number 79 in 1976 was smaller than the number 440 in 1964.  Please keep with me on this.

I have now learned that:

The name Polara is a reference to the Polaris star, in a marketing attempt to appeal to the excitement surrounding the Space Race during the early 1960s.

Back when I was an eight-year-old and my family purchased one of these Dodge Polara cars, I was clueless about this cultural reference.   I must, however, confess that to this day I recall every design element of the dashboard of the Dodge Polara that my family inhabited.   Every gauge or indicator was surrounded by stylish chrome.  Ask yourself if you were male, and if you were to look at this cowling with two rounded features projecting towards you, with these two rounded features staring at you with points in the middle of each feature, in the year 1964 … what would you subliminally think that you were facing?

Of course in 1964 what you would think of was the Space Race, the Sputnik Scare, the need for all Americans to remind ourselves of the need to be stronger, need I say more manly, than the Soviets?  It was two years earlier in  1962 that JFK said:

We choose to go to the Moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win, and the others, too.

This, and not anything else, is what we think of when we look at the futuristic Jetson-style dashboard of the Dodge Polera in 1964.  

Well I suppose the other possibility is you would think it is two enormous eyeballs, staring at you.

Right?

But I digress.  In 1964, the Dodge Polara had a 12-volt electrical system.  Later in 1976, when I scraped together my dishwasher earnings to buy a used 1966 VW bug, I was buying a car with a 6-volt electrical system.

And there came a time just a few years later when my very inspirational college physics professor “Pete” Granville Smith somehow made me catch on about I2R.  This is the notion that the power loss in an electrical conductor is, unfortunately, tied to the square of the current flowing through the conductor.  It is not linearly related to the current, but unfortunately tied to the square of the current.  What this means, of course, is if you somehow can plan ahead and choose to send twice as much voltage through the wire, this cuts the current in half and you can reduce the power loss by a factor of four.  There is a power-of-two thing going on here.  Whatever amount of money you had to spend to buy the wires, now it is less money.  

Which then brings me to a recent news story.  An electric utility company in Florida, and I know this will shock you, but keep with me on this, apparently tried to game the system recently.  They can charge their customers money based upon how much they spend on things like cross-country power lines.  Normally, to build a big expensive cross-country power line, they have to get permission from the relevant state regulator.  I know this will also shock you, but I guess the electric power companies try to game the system by figuring out if there is some power line that they can construct, and pass along the costs to the customers, without having to get the permission from the relevant state regulator.

Yeah.  So normally if you were going to run a lengthy electrical transmission line from point A to point B, the two points being, say, 176 miles apart you would want to be non-stupid about how you engineer the design of the transmission line.  You would want to design the line so that it runs at maybe 230 kilovolts or even 440 kilovolts, to minimize the resistive losses.  The drawback to this, if you are located in Florida, is that you would need the permission of the state regulator to spend the money to construct such a transmission line.

So what if you intentionally do it a stupid way, so that it runs at a mere 161 kilovolts?  Well, the resistive losses would be much worse, maybe 2 or 4 or 8 times worse.   To get the system to work, you would have to spend the money to make the wires much, much thicker, which would be much more expensive.  The wire would cost more.  The insulators that support the wires would have to be be more expensive because the wire is heavier.  The support towers would have to be closer together because the wire is heavier, meaning you would have to pay for a lot more support towers.  Also, every time you are going to install a support tower, you have to pay money to whoever owns the land where the support tower is going to be placed, and you have to do a lot of expensive truck rolls to that location.

Oh and the wires of that 176-mile transmission line, they are giving off waste heat, so much heat per foot or per mile of transmission line, except the waste heat is maybe 2 or 4 or 8 times more compared with a non-stupid transmission line.

Normally, no sane system designer would use this lower voltage of a mere 161 kV for a long-distance run.  You would only use this kind of expensive power line for a short run.  A “last mile” for example.  If it is a short run, only a mile or less, then the higher cost-per-mile of construction cost, and the crummier amount of waste heat per mile, does not add up to so much.

But now think about it not from the point of view of the actual consumer ratepayer, and not from the point of view of what is good for the environment.  Just think about it from the point of view of Florida Power and Light.   If you choose to drop the voltage of the transmission line from 440 kV or 230 kV down to a mere 161 kV, this offers a big advantage, namely that you don’t need to get permission from the state regulator.  You can just construct the power line and charge the cost to the ratepayers, and that is the end of it.  Not only that, if the power line loses 4 times as much of the transmitted electrical power as waste heat along the length of the transmission line, or 8 times, that is not your loss as an electrical company.  That loss is passed along to global warming and to the end users.

So now we get to return to the start of the story.  In the 1960’s and 1970’s, the makers of motor vehicles got a clue.  Make the electrical system 12 volts instead of 6 volts and the wires don’t need to be as thick and the resistive losses will be smaller.   This also reduces the weight of the wiring harness, which saves gas.  Indeed during those years, some trucks migrated to 24 volts or even 48 volts so as to get even greater benefits from the reductions in the resistive power losses and lighter wiring harnesses.  That Dodge Polara was a 12-volt car, while my VW bug with its 79-cubic-inch engine was a mere 6-volt car.

So anyway you can read in the news (New York Times article, May 31, 2022) about a stupidly designed transmission line that FP&L constructed recently.   Of course this cross-country line, at 176 miles, ought to have been at whatever highest voltage it could have been.  Instead, the electric company gamed the system to get away with building a much less energy-efficient transmission line, while still being able to charge it off to the ratepayers.  

So that’s what made me think of the VW bug and the 6-volt electrical system, and the Dodge Polara and its dashboard that made you think you were, perhaps, on the winning side in the Space Race.

One Reply to “Higher voltage? Lower current?”

  1. A couple of decades ago IIRC there was a movement in the auto industry to move to a 48-volt standard, which would also allow a low of actuators to be little motors rather than mechanical things. Not much happened with it though.

    In regard to transmission lines, your analysis is correct, but it doesn’t mention NIMBY. The single largest barrier to installing transmission capacity is fierce political resistance by people along the way. This is compounded by the fact that anyone who already delivers power to the destination has an incentive to finance grass roots groups that oppose the new transmission line. So you get things like “According to the Iowa Office of Energy Independence, lack of transmission line capacity is beginning to restrict further growth of wind farms in the state. A report from the NREL acknowledges that this is a major hurdle to increased wind power development in the U.S.” https://en.wikipedia.org/wiki/Wind_power_in_Iowa

    More recently, the state of Mass. tried to lower the carbon-intensiveness of its power by installing a transmission line down from Hydro Quebec. That was blocked by a voter initiative in Maine, which coincidentally was heavily funded by a couple of power companies.

    So in the case of FPL, it could easily have been worth it to avoid having to fight in front of the regulator. It’s even conceivable that the lifetime cost of the lower-voltage line was lower than the higher-voltage line, if you count the cost of the political fight. I do notice that the line is relatively short, 176 miles. Indeed, if you know the total capacity, you could do a rough calculation of the increased I2R losses and what they cost.

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