EnviroMission in Texas deal

Australia's EnviroMission has signed a deal with US outfit Apollo Development to develop a number of power plant projects in Texas based around the former's skyscraping solar updraft tower concept.

Under the terms of the companies' heads of agreement, Apollo will have exclusive rights to EnviroMission's design – which uses solar radiation to heat a large mass of air in a tower structure to drive turbines for electricity generation – in exchange for a $2m development payment and a yearly royalty and technology fee.

“Apollo is planning to develop multiple Solar Tower power stations to benefit from the economy of scale of an integrated construction timetable, and has planned initial siting studies for the high solar radiation regions of El Paso, Laredo and the Permian Basin,” says EnviroMission chief executive Roger Davey.

Apollo spokesperson Mike Rowley adds: “Apollo is confident the capital cost and conforming power profile of solar tower technology will deliver a highly competitive first-to-market renewable energy opportunity to the energy mix required to replace the current raft of carbon-based power plants being retired for economic and environmental reasons in Texas."

EnviroMission is also working on front-end engineering and design for a 400MW solar updraft tower project in Arizona with international engineering outfit Arup. 

Solar updraft towers – a concept pioneered by German consultancy Schlaich Bergermann and Partner more than 30 years ago – are made up of three basic components: a vast, open-sided, transparent, circular membrane roof, known as an air collector; a chimney-like tower; and a set of pressure-staged turbines.

As the sun beats down on the air collector, the air and earth beneath the membrane are heated. The air becomes lighter as the temperature rises, and flows towards the central tower, while cooler air is drawn in at the collector's edges.

The collector membrane allows solar radiation through, but absorbs the long-wave "re-radiation" coming off the heated ground, so that heat is transferred to the air flowing inward. When the heated air reaches the tower base, the updraft's air stream is converted into mechanical energy using turbines, and then into electricity via conventional generators.

Each 200MW tower would be made up of a “spoked wheel” air collector measuring 3.2km across, topped by a 750-metre-high, 100-metre-wide tower – only slightly shorter than the world's tallest man-made structure, Dubai's 828-metre Burj Khalifa skyscraper.