Looking at the most likely ways of reducing greenhouse gas emissions, I am struck that low-tech innovations, such as wind turbines and (the yet unproven) sequestration of CO2 from coal-burning plants, seem to be offering faster and better solutions than high-tech ones, like solar cells and improved nuclear reactors. Now in New Scientist, I found an intriguing, if a bit quirky article describing how a combination of heat from greenhouses and hot-air balloons can be used to generate substantial amounts of electricity.
In a recent blog entry about OTEC (Ocean Thermal Energy Conversion), I described a resurgent technology from the 1960s that used ocean thermal gradients to power simple heat engines.
The New Scientist article, “Balloon power isn’t just a load of hot air,” describes a paper by Australian innovator Ian Edmonds that proposes a simple two-cycle engine using hot-air balloons as pistons. Edmonds notes that atmospheric gradients, augmented by a greenhouse at the surface, make it possible for balloons to succeed where other proposed air-temperature gradient devices, such as thermal updraft towers, run into technological difficulties.
The abstract and outline of Edmonds’ article, with a subscriber’s link to the full text, appear at this link at Science Direct. Here’s part of the abstract.
This paper describes a solar powered reciprocating engine based on the use of a tethered hot air balloon fuelled by hot air from a glazed collector…. The engine thermal efficiency compares favorably with the efficiency of other engines, such as solar updraft towers, that also utilize the atmospheric temperature gradient but are limited by technical constraints to operate over a much lower altitude range…. Preliminary cost estimates suggest a lower $/W installation cost than equivalent power output tower engines.