Does this sound right to you? (steam turbing output question

Junghalli · Post by **Junghalli** » 2006-03-21 12:24am

I was doing some research on fusion power on Wikipedia and I came upon this.

Wikipedia wrote:Steam turbines are made in a variety of sizes ranging from small 1 hp (0.75 kW) units used as mechanical drives for pumps, compressors and other shaft driven equipment, to 2,000,000 hp (1,500,000 kW) turbines used to generate electricity.

1,500,000 KW is 1.5 GW, right? That seems a little off to me, as AFAIK a modern nuclear power plant only generates MW level energy.
What am I missing?

Stark · Post by **Stark** » 2006-03-21 12:26am

Some powerplants (which use steam turbines, which is what they're talking about) produce GW level output. I would have assumed this used many small turbines instead of individual single ones, but I guess not.

Junghalli · Post by **Junghalli** » 2006-03-21 01:13am

Doesn't the whole US have a total power output of around 500 GW?

Interesting, I found this while trying to find a balance of plant for a starship fusion reactor in my SF setting. Maybe I could just use a regular steam turbine?
A steam turbing in an FTL ship has a weird feeling to it but I guess it's probably the most plausible system out there.

phongn · Post by **phongn** » 2006-03-21 09:35am

Total net power generation capacity for Summer 2004 was 968GW. (Source)

Junghalli wrote:A steam turbing in an FTL ship has a weird feeling to it but I guess it's probably the most plausible system out there.

That sounds like a pain to implement, especially with the radiators to cool off the ship. IIRC, most spaceborne nuclear reactors to date have been liquid-sodium reactors (like on the RORSATs)

Post by **Darth Wong** » 2006-03-21 10:42am

Considering the truly gargantuan size of some of the turbine systems I've seen, it wouldn't be that surprising to find one that can handle the full output of a GW-class nuclear reactor. The really big turbines will have a cone-like shape where there are many sets of turbine blades on a single huge shaft, of increasing diameter. I don't know of any 1.5GW reactors off-hand, but it seems possible. After you've seen a single generator which spans several floors of a powerplant, you can't be too surprised.

nickolay1 · Post by **nickolay1** » 2006-03-21 11:13am

An RBMK design of 1.5GW of electric power was produced. The total thermal power output apparently was nearly 5 GW.

http://www.iae.lt/inpp_en.asp?lang=1&subsub=29

nickolay1 · Post by **nickolay1** » 2006-03-21 11:14am

Edit: Sorry, I posted a bit too early. It appears that two 750MW turbines are used.

SyntaxVorlon · Post by **SyntaxVorlon** » 2006-03-21 12:07pm

The output of a nuclear plant can be on the order of 1GW as I recall.

SyntaxVorlon · Post by **SyntaxVorlon** » 2006-03-21 12:07pm

Edit: Or rather 3 GWs of heat and 1/3rd of that as usable electricity.

Post by **Darth Wong** » 2006-03-21 12:44pm

The scaling limit of a turbine would obviously be the durability of the assembly, and in particular the main shaft, and the practicality issues associated with making it bigger. Eventually everything reaches such a size that it's just not practical and you're better off splitting the steam pressure as is apparently done in the reactor referenced in Nickolay's quote.

Junghalli · Post by **Junghalli** » 2006-03-21 03:38pm

phongn wrote:That sounds like a pain to implement, especially with the radiators to cool off the ship. IIRC, most spaceborne nuclear reactors to date have been liquid-sodium reactors (like on the RORSATs)

I guess I'll use that then.
So that works about the same way, only it uses liquid sodium instead of water to drive the turbines?

Metrion Cascade · Post by **Metrion Cascade** » 2006-03-30 04:29am

Junghalli wrote:
phongn wrote:That sounds like a pain to implement, especially with the radiators to cool off the ship. IIRC, most spaceborne nuclear reactors to date have been liquid-sodium reactors (like on the RORSATs)
I guess I'll use that then.
So that works about the same way, only it uses liquid sodium instead of water to drive the turbines?

It's used as the reactor coolant. If you're using turbines, the sodium coolant's heat would have to be transferred to the water for the turbines by a boiler. Basically the coolant pipes connect to a boiler, where they're divided into a large number of smaller pipes. The water contacts those pipes, boils from the heat, and goes to the turbines.

I can't find out anything about how RORSATs converted the liquid sodium's enthalpy to electricity, but they were pretty small reactors and not designed to last very long.

Since you're dealing with a reactor that can't be supplied from outside while operating, I think submarine reactors would be a good template (and the Seawolf does use liquid sodium). The main issue you'd face that submarines don't is that subs can replace the feed water for their turbines by desalinating seawater.

IIRC liquid water is rare in interstellar space. *thinks* Yeah. Rare.