Sunday, March 25, 2007

Cost of Coast to Coast

With ghost energy it costs less to carry the corpses to where you'll use them. Shipping coal by rail or barge to power plants close to or within cities saves on the losses from resistance in power lines. Keeping troubled nuclear plants like Indian Point running in densely populated areas continues for the same reason. Oil pipelines are strung out through ecologically sensitive and politically precarious regions because you can't uses the ghoulish stuff where it's at.

Some years ago I read Bucky Fuller's "Critical Path." If you haven't read Fuller you can get a taste here. After you get used to his style what he has to say flows pretty well. I'm a fan of e.e. cummings and I saw a bit of his style in Fuller's writings. Fuller had a plan to connect all the continents into one large energy grid. Now when you're working with ghost energy this just sounds silly. It costs less to just lug the corpses around. But what if you are using real energy? Does it make any sense to share real energy over large distances? What is different about real energy that might lead us to consider such a thing?

When we build an energy grid we do it on a fundamentally temporary basis. Our nuclear power plants will have to be decommissioned, our coal plants will run out of coal, even our large hydro power dams have reservoirs that silt up. There is no point in building power lines to last longer than the power plants. So the basic calculation is how little material can we get away with using and still get power delivered fairly reliably over say 50 years. Roman roads were built with the idea of permanence but ghost energy has impermanence built in because it can't possibly be sustainable. So, when Enron was ripping off California a few years back, it was not as if they were holding up power from Chicago that San Fransisco could have used. They were manipulating things so that power from Chicago was not supplying people a bit further west and step-by-step a little further on so that power generated in Nevada couldn't be freed up for California. It was a matter of clever nudging through manipulating the deregulated market to run up prices rather than actually having (or not) power from the Great Lakes region flow all the way to California. Power losses keep energy from going all the way across the country.

Let's look at that: the power dissipated in transmission is the current squared times the resistance in the line. The current is power divided by voltage so to reduce the current for a given amount of transmitted power the voltage is increased. But, you can't increase the voltage too much because with the lowest possible cost power lines we use we end up with high potential gradients leading to corona discharge. What if, like the Romans, we were thinking build it right once and it will be more profitable in the long run? With real energy we might want to think this way since it does not run out the way ghost energy does. There is actually an organization called GENI that has been looking at aspects of this and they find that it can make sense to run power transmission over distances up to 7000 km. Here they are interested in remote renewable energy sources.

The Sun shines everywhere but not everywhen. (I'm beginning to sound like cummings or Fuller) So let's think about what it would take for California to get its predawn power from the East Coast. In 2005 California used about 270 billion kWh so let's neglect peak or non-peak and just say we want two hours of that per day from the East Coast so we need a transmission line that can carry 30 GW somewhere along the Union-Pacific right of way. Now to carry that much power we need to increase the cross-sectional area of the conductor of the 3 GW Pacific Intertie by a factor of 10. But if we do this, we will also increase the radius of curvature by a factor of 3 so that we can increase the voltage by that much without hitting the corona discharge limit and so reduce power loss by a factor of 10. That means we can go 8000 miles instead of 800. Actually we get more than this. We had to make the conductor thicker to carry more power but resistance goes like length (the trouble with long transmision lines) divided by the cross-sectional area which we just increased by a factor 10 to accomodate the extra power. So really we should be able to go 80,000 miles with the same loss. Thus, if we don't want to get too fancy about pushing up the voltage, we're still where we need to be just by increasing the cross-section. Can you think of a piece of metal about 6 cm wide running from the East Coast to the West Coast? We've had a pair since 1869. We just don't want to corrupt Congress with the next set.

Why in the world would the East Coast want to supply California with power? Actually it is a better deal for the East Coast. They get power from California in the evening when the Sun is still shining on the West Coast. Both the East and West Coasts would need to be generating more real energy that they use for this to be beneficial. But, they may be doing this anyway if power storage has replaced the base load concept. Once they are doing this, they may want to expand what they're doing, running a cable to Europe or Asia and before long, the Sun never sets on solar power. Building over specified links makes much more sense when we expect them to last for centuries. They can also replace transitional power storage technology with limited design lifetimes, perhaps reducing costs associated with distributed power storage. Think of them as the pavimentum of a sustainable world.

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