Re: OT: cost of renewables

I agonised a bit over whether to say 100,000 years for just that reason. Presumably they also hunted megafauna directly. But >10k is certainly uncontentious.

Going quite that far seems to me to be less likely. There's a small part of me that wonders whether the very long-term future may look more than a little like Diskworld.

Will that produce enough wind to turn the turbine blades?

No, but it might start the diesel engine that is needed when there is no wind.

I'm quite willing to believe that some future advance in solar panels will make them far more efficient.

The problem with solar panels is that the peak load on the electricity system is when everyone gets home from work about 18:00, puts the cooker one, and especially in winter when they turn on the heating too. Soon they'll be plugging their cars in to charge which will make things worse.

The problem being that in the winter at 18:00 it's dark, and it doesn't matter how many solar panels there are their output will be zero.

They're really great for running your air conditioning, but that's not a major load in the UK.

We need grid scale energy storage. Or a power source that doesn't stop every night, or when the wind doesn't blow.

I don't know of any grid scale energy storage.

Andy

I'm not on the far more efficient given how long we have been doing them now.

And we know that isn't feasible if you can't do pumped hydro.

We know that is nukes.

Pumped hydro is that, but few can do that. Australia and Norway have been doing that for more than half a century now.

These are just applications of the basic principles, which have *not* changed.

They are around 30% efficient now. over 100% is impossible.

Remember they don't create energy, they collect from the sun. If the energy isn't there, they cant collect any, can they?

Exactly.

BST is the one with no clue.

At a given point a new technology turns up. Might be a steam engine. Might be a laser. Might be a metal oxide rectifier or a cats whisker diode or a photoelectric cell. Science then goes to work to establish how they work, and how much they might be made to work better.

The first is quite rapid. The second - getting incrementally closer to 'as good as it gets' - takes a bit longer.

Early steam engine were less than 1% efficient. By the time we get to WWII piston steam engines are up around 20% and steam turbines have reached nearly 40%, and there they have stuck. Because the way to make them better than that is to have enormously hot superheated steam and infeasibly large condensers, and still that only gets you a few percent more.

Gas turbines which start with extremely hot gases can, when added to a steam turbine get up to around 65% efficient.

Windmills are already pushing the Betz limit. There is little left to come other than building them higher.

Solar panels are already pushing their limits.

We are not limited by technology, we are limited by the actual energy in the coal, gas or wind or sun itself.

The only place there are massive amounts of untapped energy left, is nuclear materials.

This is not theory, this is not opinion, it is the nearest thing to facts - objective facts - there is.

If we had the sort of education that was standard in the 1950s, which was based on sound teaching of basic English and mathematics, we might have a population with a hope of understanding this.

Instead Blair's Britain got in first and destroyed any educational discipline there was, and people's knowledge of science is now based on consumer marketing telling them how wonderful it all will be, after they have bought the shiny new thing.

Where renewable energy is concerned, it wont be wonderful. It will be a hell of poverty that is beyond the conception of anyone brought up today.

Efficency is defined (as any 1st year physics undergrad will tell you) as:

useful energy out

----------------- energy in

and since "useful energy out" can be redefined as "energy in" minus "energy wasted", you get

energy in - energy wasted

------------------------- energy in

or, putting it slightly more mathematically:

Ei - Ew

------- Ei

For a heat engine, each of these energies is directly proportional to the absolute temperature of the working fluid, so the above can be changed to:

Ti - To

------- Ti

where Ti is input temperature, and To is output temperature and both are in Kelvin (K). Steam starts to attack even stainless steel above 600C or so, so if your input temp is 600C and your output temp is 101C (so the steam doesn't condense), your efficiency is:

(600+273) - (100+273) / (600+273)

or 57%

You'll find that the same considerations apply to any energy conversion system, so the notion that it will be possible to make solar panels "far more efficient" would seem fanciful at best.

Hilarious -- an understanding of the basic principles, while usually necessary, is not in any way sufficient when you want to get any real work done. And the insights by those working

#Paul

That is certainly a useful definition of efficency, and indeed a very common one, but there are others that are also useful, and indeed are more useful in some contexts. Please stop this lazy expectation that your undergraduate degree is somehow the be-all and end-all of understanding.

#Paul

I think you'll find the output of a steam turbine is usually well below atmospheric pressure, and this permits a lower temperature.

Andy

Idiot alert:-)

I have a vague recollection from an engineering course some 60 years ago that overall steam turbine efficiency is limited by the latent heat of water (creating/condensing steam). The figure we were given was 44%. Research was underway at that time with MagnetoHydroDynamics? to get a bit more for your kilo of coal.

That's not what we are talking about - which is whether the basic principles have changed or not, and they haven't.

I get that. And *I'm* cautioning that a simplistic and dated view of "basic principles" might result in conclusions of dubious value.

As to whether basic principle might be seen as having changed or not (particularly e.g. in EM or QM) is an interesting question. In one sense Maxwell's equations are the same as the original by-component ones, even if now expressed in the language of differential forms. However, there is a very reasonable argument to be made that the basic principles underlying the formulation of EM - as now understood - is utterly different. In fact, in different sub-fields, things that might be thought of as basic principles are not always seen the same way. In optics (even quantum optics), E and H are typically regarded as the fundamental EM fields; whereas for those more interested in relativity (or differential forms) it is instead E & B.

And QM does not escape this sort of thing either, with quite interesting attempts to rederive QM by making only the most minimal set of assumptions (or "basic principles"), but in a fundamentally

#Paul

yes, but the advantages gained from going from 100°C to say 50°C are not great

typically at 600°C which is *well* above any practical boiler the efficiences are

versus

A gain, and worth the super large condensers, but not an order of magnitude gain

In practice sort of yes, but that boils down to how hot you can practically superheat your steam.

certainly getting the water to condense gets the last drop out.

In practice big coal power statins and nucleart plants are around 37%.

I seem to remember that as well. Another 'save the planet' idea that never came to anything for reasons we have all forgotten

Fuel cells also.