Not a direct thermodynamic limit per se, but a limitation of materials. You can make the heat to work conversion efficiency as high as you like by increasing the temperature at the hot end of the cycle.

The basic problem is that we don't have a (cheap) material that can take high temperatures while maintaining good mechanical strength and manufacturability. Metals have an upper operating temperature of about 1000oC give or take a couple of hundred, and that is what results in the thermodynamic efficiency of about 30%.

Ceramics take higher temperatures but are much harder to manufacture machine parts from and have crap tensile strength.

Alan - thanks for the links. You have enough material there for a guest post on this important topic - shoot an email to the editors box or nate@theoildrum.com if interested.

Just like I said, no 18 wheelers for long haul.

And what is the source of electric power -- 50% from dirty coal, 20% from natural gas, some from nuclear and oil.

And a 50% plus loss of fossil energy in power generation.

Then some loss in power transmission.

Then a 25% loss in the batteries.

Sounds to me like a lot of waste of fossil energy to get electric energy.

And what about the infrastructure for all of the electric economy, there are not even any plans for how to do all of it, and it would be trillions of dollars of infrastructure for the thousands of miles of highway.

Big capital costs in change over that will not be made in today's global bankrupt economy.

Seems like you solar folks are talking about what you dream about, rather than what is real.

And in so doing the above you are not looking at reality, the end of oil and time for risk management. We are moving at 100 MPH and the end of the tracks is just ahead, and you can't see it as you dream of what can never be.

This site is full of MEN, mostly MEN from the richest and most affluent societies on earth, who are obsessed with trying to invent technofixes to keeping things economic growth going, rather than careful analysis, which indicates that we have lost the battle with nature and can't keep this economy on the same path of everyone thinking they can have all the material possessions they want.

We've mostly used up our one time endowment of oil, and now you are grasping at straws, like solar and wind, which give us electric power, which we will have a surplus of when the factories, plazas, and airports shut down, this is happening today.

What will you do with spare electric power?

We have met the enemy and it is us, and ideologies and cultures of affluence, arrogance, and greed.

When the highways and power grid go out, so too will your solar toys.