REALLY! We still use steam to generate electricity?

[I2CU]

Watching the TV the other day with my partner when I heard her say "Really, we still use steam to generate electricity?"

 

When I confirmed to her that yes we still do, she looked at me dumbfounded, which made me think, "why have we not been able to generate large quantities of electricity without steam?"

 

So I jumped onto the internet and there it was, that word that drives our society these days "Economical". It seems that tech created over 100 years ago is still the only economical way to generate electricity.

 

WHY?

 

How the hell could we possibly create a colony on the moon or anywhere else where water is rare if we still need steam to generate electricity in large quantities?

Edited July 26, 2013 by I2CU

[EdEarl]

It's not that we must use steam, it is that water is plentiful, inexpensive, eco-friendly, and has the right physical properties for the job. Although, gas turbines, windmills, solar PV, and some other power generating methods do not use steam.

[Danijel Gorupec]

There are other ways to generate electricity from heat source. Diesel generators are used to about 1MW. Gas turbines can be used to tens of MW. However, the steam cycle is still the best choice to generate electricity from large (>1GW) concentrated heat source. It is a cheap, clean, silent and efficient method.

 

Cheap... low temperatures - low material stress (compared to gas turbines). Less complex than diesel motors.

 

Clean... What would happen if you use nuclear powered gas turbines – you would have to discharge the gas directly into environment. In steam cycle, if needed, you can use double-circuits so that water (steam) released is newer in touch with the fuel.

 

Silent... you know how a diesel generator or a gas turbine sounds.

 

Efficient... There is a nice trick with steam. You can condense it into water (low volume) and then pump it back into the high-pressure boiler. This makes closed steam-water circuits efficient.

 

But look... diesel generators, gas turbines, steam cycle... all these are using the same physics (see Carnot cycle). No fundamental differences here. It is actually water that makes steam cycle so appealing. Water is cheap and clean and has high thermal capacity.

 

We know no fundamentally different method to generate large quantities of electricity from heat sources (you can try with thermo-couples for minute quantities).

 

As you can see, the world doesn't change that much fundamentally. We are just reusing many old fundamental technologies. Science is only rarely able to give us new insights. Most of the time the world is pushed forward by plain old engineering (reusing known fundamental stuff in a smarter way).

[Delbert]

I think it's the case that water is perhaps the easiest and safest way to transfer the energy from a heat source (I nearly said 'boiler', but would probably be shot down for such!), to cause mechanical movement of an electrical generator. And presumably until we cover large enough areas with enough wind farms, or enough wave power generators etc, we'll continue to do so until we find a way to generate electricity directly from a heat source.

[Phi for All]

How the hell could we possibly create a colony on the moon or anywhere else where water is rare if we still need steam to generate electricity in large quantities?

 

We use what's most efficient for the locale (or at least that's the hope). Steam wouldn't be efficient for a moon colony, where we'd find that solar was much better than using what little water we had for steam. In Colorado, we get a LOT of sunny days so solar companies love it here. Also, we have abundant natural gas and use that for heating and hot water, as opposed to the US east coast that uses coal and oil a lot.

 

When we figure out how to "send" electricity from a space-based solar array, I'd love to see a worldwide project set up to supply some renewable energy (private enterprise might beat us to it though, since there are now conglomerates whose pockets rival those of some countries). It would be immensely ironic if the most efficient way to utilize a space-based solar array was to send a focused beam to the Earth's surface where it could heat up a steam turbine to create electricity.

[Danijel Gorupec]

 

Steam wouldn't be efficient for a moon colony, where we'd find that solar was much better than using what little water we had for steam.

 

 

When you say 'solar' you mean PV?

 

Solar energy can also be used to generate steam. Still, I think PV would be much better choice for a Moon colony, except maybe if >1GW is needed.

[Bill Angel]

Interesting remark about the properties of steam in the book "A Different Universe: Reinventing Physics from the Bottom Down" by Robert Laughlin (Chapter 4, Water Ice and Vapor):

As one raises the steam pressure above a pot of boiling water the roiling surface becomes harder and harder to see and, at a critical pressure, disappears. Above this pressure the liquid and vapor have lost their separate identities and have merged into a single phase, the fluid, so that there is no surface. The pressure at which the liquid and vapor merge is useful to engineers because of the special expansion properties of steam they exploit to make engines are maximized there, but is otherwise unimportant.

 

 

This is an excellent thought provoking book on a wide range of topics in physics. Dr Laughlin received the Nobel Pize in Physics in 1998.

[Janus Sunaj]

Phi for All is right about using the type of electrical generator that is optimum for the locale. Steam (more properly, a Rankine heat engine with water as the working fluid, with either nuclear or thermosolar heat) may not be optimum for a Moon base, because of the temperature ranges there – even though it's a pretty good choice here on Earth, being non-toxic, non-flammable, and low-corrosivity compared to other working fluids – mercury, pentane, CFC, etcetera – and having a fairly low molar heat of vaporisation, for good efficiency.

For a Moon base, a Stirling (or Ericsson) heat engine with hydrogen working fluid may be a better choice for nuclear or thermosolar heat, and maybe better than photovoltaic for large-scale needs.

[decraig]

OK, I give up. What's special about water: Temperature of vaporization, thermal conductivity, heat of vaporization?

 

Ammonia and chlorofluorocarbons are used in refrigeration units. How do these compare to water in physical properties for use as a working fluid for power generation?

Edited December 7, 2013 by decraig

[John Cuthber]

OK, I give up. What's special about water: Temperature of vaporization, thermal conductivity, heat of vaporization?

 

Price.

[Dekan]

I share the surprise expressed in I2CU's OP, about the continued use of steam in modern times

 

It's true that in past times, in the 18th and 19th centuries, steam was a radical new energy source. It led to the Industrial Revolution, the abolition of slavery, Marxist theory, practical physics, engineering, and so on.

 

All well and good, but in these modern times, it seems steam ought to have become outdated. Yet it persists.

 

Consider for example, a nuclear submarine. Such a submarine has an onboard nuclear reactor. But the reactor doesn't provide a direct motive force. The reactor just heats water until it boils into steam. The steam then goes through pipes, to spin a turbine round - which spins a propellor - which pushes the sub forwards

 

All the reactor does is generate heat. In the past, this heat came from the combustion of coal or oil Now it comes from the fission of uranium or plutonium.

 

Is that the best use of atomic energy - to boil water in a steam engine?

[EdEarl]

Is that the best use of atomic energy - to boil water in a steam engine?

If there were a better substance than water, it would be used, especially in electrical generation where efficiency gains of a fraction of a percent are significant.