Waste heat ballooning

Many industrial business, such as power stations, pump out significant quantities of waste heat. This idea is to divert this waste warm air to fill large tethered balloons. Warm air would enter the bottom of the balloon (through a very long flexible tube when the balloon is airborne). The air supply would take air straight to the top of the balloon. As the air cools it would spill out of the (open) bottom of the balloon.

This could work in a number of ways. For somewhere which pumps out waste heat 24 hours a day, the balloon would be weighted in such a way that it is buoyant enough during the cool night to rise, but gradually sinks during the day as the ambient air warms up. For businesses that only generate warm air during the day (e.g. a large office block's air-conditioning), it would rise during the day and sink during the night.

With balloons constantly shuttling up and down all the time, it might be possible for them to give some of their warm air to another balloon, permanently moored at, say, 5,000 feet. In this case, the permanently moored balloon could have a small amount of luxury office space slung beneath it, and the other balloons get used for commuting.