Windmills for Steam (Sep, 1938)

Windmills for Steam

The fan-like internal structure of a huge steam turbine designed for driving an electric generator. High pressure steam enters through a close fitting cover at the center, and spreads through the “windmill” in both directions, transmitting its energy to the driveshaft. There are 1,500 blades. The longest measure thirty-eight inches and move with a tip speed of thirteen miles a minute—nearly as fast as a rifle bullet. Giant turbines such as these have made modern large scale power generation possible.

The world’s largest single-shaft turbo-generator has been installed in the Richmond Station of the Philadelphia Electric Company. Made by the Westinghouse Electric and Manufacturing Company, it produces 165.000 kilowatts, about enough to light continuously 7,000,000 twenty-five-watt lamps, or one in every fourth home in the United States. The turbine runs at such high temperatures that its color is cherry red when it is operating. The generator is at the right-end portion of the unit.

  1. TomLR says: November 28, 20112:05 pm

    Someone see if I understand this article correctly. It says that the single turbine “produces 165,000 kilowatts, about enough to light continuously 7,000,000 twenty-five-watt lamps, or one in every fourth home in the United States.” That’s assuming that the period in “165.000” should be a comma. In 1938, eh? That’s a number that we won’t see anything close to again.

    I just looked on this site:…
    and the estimate for 2001 total US household electrical energy usage was 1,139.9 billion kWH.

    Could the 1938 US home electric energy consumption actually have been low enough that four of those turbine generators could have produced enough power to light up every household? I know that a lot of the nation wasn’t even electrified at that time, and there were many fewer electric devices, but that’s more of a change than I imagined! I feel as if I’m not correctly interpreting something here.

  2. Jari says: November 28, 20112:36 pm

    TomLR: It is comma in the big picture, so it’s 165 MegaWatts. In my grandparent’s house, which was extended from 2 rooms to a whopping 4 rooms (including the kitchen) right after the WW2, there were total 6 lightbulbs, radio, fridge and a small, range with 2 heaters + oven for the summer use. This was in Finland, so I don’t know, if it’s comparable to the US in that period.

    Here’s some more about that particular power station: http://www.workshopofth…

  3. JMyint says: November 28, 20113:59 pm

    TomLR- I don’t think you are quite getting the analogy. In 1938 there were about 30 million homes in the US. If each home had a single 25 watt bulb in it, then this would provide power for a fourth of those bulbs.

    Much like Jari’s description a US house with electricity at the time would have a light bulb per room (likely 60 or 75 watt), a refrigerator, and a radio. They would likely have some electrical appliances like a iron, toaster, electric fan and a vacuum cleaner. The lady of the house would be glad to have a washing machine, sewing machine, and a mixer. So a six room house you are talking about using Anywhere from 400 to 1500 watts at any one time. A house I had bought in the 80s had 40 amp service so that would have set the maximum consumption around 4500 watts. By comparison the minimum allowed by law today is 100 amp service.

    The general rule of thumb for power generation is 10,000 watts per household capacity.

  4. Sean says: November 28, 20118:00 pm

    I work for a company that builds these guys up to about 70 megawatts. A couple changes that I can see, though are a few stages of Curtis blading at the steam end and general decline of the use of opposed rotors for load balancing. I’d guess that advances in thrust bearings permits the simpler construction of single-directional flow.

  5. TomLR says: November 28, 20118:32 pm

    @ JMyint. Thanks. Indeed, I totally missed the analogy based on 7,000,000 *light bulbs*, as you kindly noted. That’s one of the reasons i asked for help from y’all. I couldn’t figure out how four of these doozers could have possibly filled the electrical needs of 1938 homes. Whew.

    The other reason was to get a conversation going.

  6. Toronto says: November 28, 201110:03 pm

    Sean: Yeah, I was wondering about those opposed rotors. Ships turbines were single-spool per shaft since the early 50s, I’d say. There are a lot of big bearings on a ship, so no big deal.

  7. Jari says: November 29, 201111:17 am

    Toronto, Sean: Seems that double-flow turbines are still used as a low pressure stage in a big power plant turbines. Does it make possible to extract even more energy from the low-pressure steam or is it for reducing the rotor diameter when compared to single-flow? Where’s Professor Steamhead, when you’ll need him…

  8. Sean says: November 29, 201111:39 am

    A big part of the reason is thrust balancing. The differential in steam pressure creates a thrust which pushes the rotor from the steam end to the exhaust end of the casing. This is especially apparent on big Parson’s type turbines like that which rely on the pressure differential across the stage rather than the velocity of the steam hitting them nearly tangentially. Thrust bearings take this pressure, up to several tons, and keep the rotor in place. This requires more structure, hurts efficiency somewhat, and needs a big honkin’ bearing which can run into the hundreds of thousands of dollars once you account for oil pumps, coolant, sensors, etc.

    The other options are to either drive a machine, such as a pump or compressor which creates a nearly equal thrust in the opposite direction, which decreases the force on the bearing, or divide the turbine in half and have one set of set of blades be thrust in one direction, while the rest go the other, thus balancing the load.

    The company that I work for (…) only makes uni-directional flow machines, though I think that we have built opposed ones in the past.

  9. Jari says: November 29, 20112:08 pm

    Sean: Thanks for the explanation.

  10. Charlene says: November 29, 201110:59 pm

    And I’ve just spent the past five minutes figuring out how many lightbulbs there are in my 600 sq ft condo. (38, if anyone’s wondering.)

  11. hwertz says: November 30, 20112:17 pm

    Yeah, when I lived in a condo the first thing my roomate and I did was start “de-lighting” it. This was before the compact fluorescents… living room? 6 100 watt bulbs. Bedroom? 4 100 watt bulbs. Another 4 100s in the other bedroom. 2 100 watt bulbs in the bathroom, the sink had a thing with like 4 75 watt bulbs in it. There were probably a half dozen more in the hallway and kitchen. I’ve never seen such a lit place. We generally cut the number of bulbs about in half, and switched the 100s for 60s for the ones we kept. I think my roomate decided to keep all 4 bulbs in his room but cut them to 40 watt bulbs.

    I cut out a few bulbs in my current trailer (lots of natural light comes in through the windows), but it was much more reasonably lit to begin with. I have of course switched to CFL bulbs as the conventional ones burned out.

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