How The Use Of Steam Can Hinder Efficiency.

There exists a concept in Thermodynamics, which describes theoretical limits in the efficiency of all possible heat-engines. This principle states, that if we have a heat-source and a heat-sink, each has an absolute temperature. The ratio between these temperatures defines the highest-possible output of free energy from a heat-engine, as well as the lowest-possible consumption of free energy by a refrigeration-device.

The principle is based on the axiomatic assumption, that there exist no perpetual-motion machines, which simply convert ambient heat into free energy. If we could connect a heat-engine to an air-conditioner, and if these limits could be exceeded, we would have such a perpetual-motion machine.

This also explains why in practice, air-conditioners, refrigerators and heat-pumps can transfer heat from a colder source to a warmer sink, with the energy in heat far-exceeding the electricity consumed. They are all examples in which the ratio of absolute temperatures is close to 1.0 . Actually, what matters is the ratio of the temperatures of the working-fluid in each case, which is actually more oblique than the ratio for air temperatures, because heat-exchangers are never perfectly efficient. And the working-fluids used tend to be similar, because the temperatures at which those systems are designed to work, are also similar.

This also implies that if we wanted to build a heat-engine that uses small temperature-differences to generate electricity, large reserves of heat would be needed as a source, and sent to the sink, before even small amounts of electricity result – which might sometimes be available – but which constrains the system, regardless of what type of heat-engine is used.


Well, in Industrial Power Generation, the temperatures which the heat-source can be run at, depend firstly on what type of fuel is burning, but also depend on the range of temperatures at which water will boil. At 1 atmosphere of pressure, water only boils at 100⁰C, which is also 373K, while the external temperature tends to be around 273-300K .

Actually, by keeping the water boiling at much higher pressures, its boiling-point can also be increased. But it is generally not boosted beyond 200⁰C , which corresponds to about 473K . And so, according to basic principles, no power station based on water and steam, can be more than 50% efficient.

(Edit 05/12/2017 : Additionally, my late father, who was a professional Engineer, used to tell me, that something prevents a steam turbine from being more than 50% efficient. But, this is not a subject I know about, even though it would additionally limit the maximum efficiency of steam-turbine-based power-stations, to approximately 25%. )

In theory, if we could operate our heat-engine at 1000K, and its heat-sink still at 300K, we could achieve efficiencies closer to 70%. Mind you, that that point our heat-source might resemble a lightbulb, more than what we are used to, but this would still obey the rules of Thermodynamics.

My only point being, that the use of water, and its associated boiling-points, is an arbitrary decision. There is no magical reason why we must use it. We could use vaporous sodium if we knew how to work with it safely.

If one breaks out, a sodium-fire is a nasty hazard, much more dangerous in its nature than wood or oil-fires already are.

Dirk

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My Server was just down for an Upgrade.

From 14h30 until 15h30, I needed to do some upgrading to the hardware of the computer which I name ‘Phoenix’.

Link To Previous Posting

This old computer from 2008 may be running the most powerful Linux version at my disposal, in 64-bit mode, and its dual-core CPU may clock up to 2.6GHz, but until now, it had still only possessed 2GB of RAM! This box still uses DDR2 RAM modules, and I had upgraded it from 2x 512MB to 2x 1GB in the year 2008. But what I needed to do today, was to upgrade it to 2x 2GB, finally giving it its maximum of 4GB of RAM.

This time around, I no longer felt I’d have the dexterity to prevent static damage to the RAM modules, just by controlling the sequence with which I touched parts. And so this time, I also felt I needed to use an actual anti-static bracelet.

Further, the CPU heat sink was plugged full of dust, so that the CPU fan was no longer able to push any cooling air through it. I knew for a long time that this also needed to be remedied, but had procrastinated in doing so. While I had the tower open today, I also took care of the dust in the CPU heat sink, with a bottle of compressed gas.

One reason I was not so eager to do this much-needed work, was the knowledge that if I had botched this, I’d have lost my one and only server. But I was also reminded, that if the server was to fail, because the CPU was consistently running too hot, the outage would take longer than 1 hour to fix. And so I finally chose the 1 hour preventative action.

I am glad that now the CPU is being cooled properly again, and that I finally have 4GB of RAM on this 64-bit machine.

Also, this was one situation in which I could not post a Maintenance Mode Notice on my blog, because for 1 hour, there was no server to render the Maintenance message screen.

Dirk