2625 Feet Tall!Solar towers, which are kind of big funnels that generate electricity by using the fact that hot air rises, are too often forgotten when we discuss solar energy. Solar PV and CSP get all the press, but solar towers have attractive power-generating characteristics and I wish more companies were working on perfecting them. EnviroMission is an Australian company working on that very thing, and they've announced that they want to build a gigantic 2625 feet/800 meters solar tower in the Arizona desert that would produce about 200 MW, enough to power 150,000 US homes. Read on for a video, more photos, and more details.
How a Solar Tower WorksThere are 3 main components. Here's EnviroMission's description:
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 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 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.
The beauty is that there are very few moving parts, so it doesn't cost much to operate, and because the area under the canopy heats up so much and there's still going to be a significant temperature differential between the bottom and the top of the tower, it can continue to produce power at night. Not as much as during the day, but some, which is better than nothing (as with solar PV).
Currently undergoing site-specific engineering and land acquisition, EnviroMission estimates the tower will cost around US$750 million to build. It will generate a peak of 200 megawatts, and run at an efficiency of around 60% - vastly more efficient and reliable than other renewable energy sources.
The output has already been pre-sold - the Southern California Public Power Authority recently signed a 30-year power purchase agreement with EnviroMission that will effectively allow the tower to provide enough energy for an estimated 150,000 US homes. Financial modelling projects that the tower will pay off its purchase price in just 11 years - and the engineering team are shooting for a structure that will stand for 80 years or more. (source)
A 11-year payback on a structure that should be productive for around 80 years isn't bad at all! And I'm sure that moving forward, material science breakthroughs will provide us with better materials to build such towers more inexpensively and have them last even longer. It's a big capital investment at first, but after that, the sun is free...
Via EnviroMission, Gizmag
See also: DOE Awards $2 Billion Loans to Double Concentrating Solar Capacity in the US
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