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Saturday, May 6, 2017

Are Dutch electric trains powered by wind?

A friend recently shared this story from several months ago to his Facebook page. I want to elaborate.

The operator of passenger trains in the Netherlands announced — or was interpreted as announcing — that all its electric trains would be powered by electricity generated from wind turbines. That's good. Wind turbines are not without their own issues, but they're clearly preferable to fossil fuels as a source of electricity.

To understand what actually happened, let's review a few things about electricity. I'll overlook some of the fine points in the physics.

  • There are many ways to generate electricity; the primary ones are organic fuels (natural gas, coal, oil, biomass), nuclear, geothermal, wind, tidal, and solar. Once the electricity has been generated, however, it's all the same. The essence of electricity is intentional, non-random movement of electrons. After the electrons are forced to move, an observer cannot tell what caused it. The word fungible is helpful here, although we usually here it in an economics class. Moving electrons are fungible.
  • With the technologies available today, there is virtually no storage in the transmission and distribution networks for electricity. The instantaneous supply of electricity from generating plants must match the instantaneous demand for electricity across the customer base. Otherwise something bad happens, like a brown-out or electric clocks that no longer keep accurate time. Of course, the demand for electricity fluctuates second-by-second, hour-by-hour, month-by-month. It's quite a challenge for the suppliers of electricity to dynamically adjust their generators to match the consumption in real-time and to keep all those generators synchronized. (This is one of the particular challenges for large-scale solar generation — something I'll blog about another day.
  • Electricity is bought and sold in units of kilowatt-hours. To illustrate, if you have 10 incandescent 100-watt bulbs in your house and you turn all of them on for an hour, you will have consumed 1 kilowatt-hour of electrical energy. In North Carolina, 1 kilowatt-hour costs a residential consumer 11 cents. At my house I pay the 11 cents to Duke Energy, which either generates the energy itself or buys it from another company at a wholesale price substantially lower than 11 cents. With the difference between what Duke charges me (pardon the pun) and what it costs them to acquire or to generate electricity, Duke pays for the transmission and distribution infrastructure such as transformers and lines, its billing systems, etc.
  • In many countries a consumer of electricity can contract directly with a specific generator of electricity to purchase so many kilowatt-hours at a negotiated price. This is a financial transaction, not an engineering transaction. Why would a consumer of electricity do this? When the price of electricity is deregulated, as it is for the largest industrial and commercial customers almost everywhere, the buyer can often find electricity at a price lower than the published standard price. On the other side of the transaction, the producer of the electricity may be operating on speculation in a market that is highly competitive and dynamic, so they may want to pre-sell their product in order to lock in their future revenues. The important thing to remember is that regardless of how the electricity is bought and sold, the actual electrons used by the purchaser are still fungible.
With that background, let's see exactly what the railroad did.

Over the course of 12 months, the railroad calculated its total energy consumption: 1,400,000,000 kilowatt-hours, or 1.4 terawatt-hours. Instead of paying the published rate for the 1.4 terawatt-hours, the railroad contracted with a specific supplier for the energy over a 12 month period. The supplier chosen by the railroad is wind-based, but the transaction in the financial markets would have worked exactly the same way if the supplier had been nuclear-based or coal-based.

The provider of wind-generated electricity would have sold its electricity one way or the other, either through similar deals or at the published rate. In other words, the railroad's purchase did not increase the total amount of electricity being generated from wind. Rather, that happened when the wind turbines came online in the first place…the occasion that should have generated a lot of excitement among the public.

Are the trains actually being powered by wind? Remember, all the electrons are fungible. Furthermore, the flow of power into the railroad's catenary varies second-by-second as trains accelerate and decelerate. So does the flow of power out of the wind turbines, for the simple reason that the prevailing winds change speed and direction constantly if slightly. Because the instantaneous supply of wind-generated electricity cannot be correlated exactly and continuously with the instantaneous usage by the railroad, it's inevitable that some of the electricity used by the railroad will come from non-wind sources at least some of the time. (Only 13% of electricity in the Netherlands comes from wind.) Likewise, at night when there aren't many trains running, the wind turbines are still producing power. Those electrons are going someplace, but not to the railroad.

It's imprecise to say, therefore, that the railroad is being run by wind-generated electricity. But it's good PR for the railroad.