[RightWhale]

Not exactly. My interest is more economic. Rockets and astronauts flying between planets and cities floating in space with no apparent purpose are interesting enough but don't make for a successful business. Resource extraction is the key, just like with the oil resource.

[SunkenCiv]

Reason i was curious, O'Neill visualized huge photovoltaic arrays in geostationary orbit, beaming electricity to large reception dishes (in unpopulated areas) using microwaves. That concept made it into the computer game "Sim City", but obviously one wonders what kind of long term heating of the atmosphere would result. Also obviously, there would be a blocking of part of the Sun's radiance here on the surface, which would have a long term cooling result. I'd wonder also about possible increases in microwave-induced cancers and whatnot, and also whether the Luddite Coalition would actually favor this system in order to get rid of coal burning power plants.

System converts smokestack heat to electricity
by Bob Holmes
May 04 2004

The key to the efficiency of the heat-scavenging system is that it uses propane vapour rather than steam to turn a turbine and drive an electricity generator. This allows it to be driven by low-temperature waste heat. When steam is used to turn a generator, it must be pressurised and raised to around 650 °C. Below 450 °C, the process no longer operates efficiently because the steam pressure drops too low. This means that the heat in flue gases below 450 °C cannot be used to generate electricity, and so is lost to the atmosphere... This is one of the reasons why fossil-fuel-powered generating stations have an overall efficiency of only around 35 per cent... Daniel Stinger, a turbine engineer, and Farouk Mian, a petroleum engineer, have developed a surprisingly simple way to harness almost all this waste heat. They calculate that a second turbine, driven by the waste heat from the first, would capture almost all the remaining energy. The first turbine's waste heat would vaporise and pressurise still more propane to drive the second... The pair calculate that flue gases will then emerge at a relatively cool 55 °C... Promising as it sounds, Wow Energy's scheme, called a cascading closed loop cycle (CCLC), remains untested... CCLC also has another potential advantage. Because it cools smokestack emissions to about 55 °C, many pollutants that enter the atmosphere today, such as mercury oxide and cadmium oxide, would instead condense inside the stack, from where they could be disposed of safely through chemical treatment.