Solar Tower Technology

Enviromission are an Australian company determined to make the biggest impact possible in renewable energy. The announcement that they want to build a solar tower twice the height of the Empire State Building shows just how far their ambition reaches.

A Solar Tower acts as a huge heat chimney enabling the flow of hot air to pass through turbines to generate electricity. Beneath the tower is a large solar canopy that traps solar heat, much like a green house. Then the lighter, expanded, heated air is drawn toward the central tower where it can rise to be exhausted into the atmosphere. The placement of the proposed 800 metre high tower in the Arizona desert would provide enough electricity for 150,000 homes.




How a Solar Tower Works (according to EnviroMission's description)

-The Tower

The Tower is the thermal engine of the Solar Tower technology. In it, heat is transformed into mechanical energy. The updraft inside the tower, produced by the rising lighter, hot air, is essential for this. The greater the velocity of the Tower, the higher the column of air is and the stronger the updraft. Therefore, a high-capacity power plant should have the highest Tower possible.

-The Canopy

The canopy converts a large percentage of the insulation into heat, which in turn, heats the air trapped under the canopy roof or is stored in the ground soil thermal storage system. One of the main objectives of the canopy is to lose as little heat as possible into the ambient.

-The Turbines

The Turbines transform the energy from the heat and pressure of the air into mechanical energy and the generator converts it into electricity. They work like the well known Kaplan Turbines used in hydro-electric power plants.

Cost Efficient

The estimated cost of this 200 megawatt structure is US$750 million, the company are in the early stages of site engineering. Financial modelling predicts that the tower will pay off in just 11 years - and the engineering team are for a structure that will stand for 80 years or more.

The Southern California Public Power Authority have already put their faith in Enviromission, signing a 30-year power purchase agreement with them to secure all the power generated by the proposed tower. With a predicted efficiency rating of 60% the tower is among the most efficient renewable power sources in the world and the SCPPA have identified this as a great opportunity to secure low/zero carbon energy for the 80 year lifespan of the project.

Our View

With such a short payback and long lifespan the future seems bright for solar towers. The question in our mind is space, the comparison with a fossil fuel generator per square metre of land used would be a very interesting comparison. Obviously space is not an issue in our deserts, but we also need to consider the initial carbon footprint of construction.

Do you have any ideas on the solar tower, Enviromission or renewable energy in general? Comment below and let's get the discussion going.

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