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CNN has a good story updating the status of the Australian 50 MW solar tower (I prefer the name 'Solar Chimney') planned by EnviroMission (OTC: EVOMY.PK). Quite a few changes have been made since I originally wrote about this, the biggest being that the tower was downsized from 200 MW to 50 MW. In addition incorporation of two enhancing technologies has allowed smaller units to become economically viable and eligible for government funding.

The re-engineered tower will be a 260 foot-diameter, 1,600-foot tall structure, taller than the Sears Tower, surrounded by a two-mile-diameter glazed solar collector at ground level. About 8 feet tall at the perimeter, the solar collector will gradually slope up to a height of 50 to 60 feet at the tower's base.


First prototype

Acting as a giant greenhouse, the solar collector will heat the air to about 100 oF (38oC) hotter than the outside air entering at the periphery, using the radiation from the sun. Acting like a chimney, the air is sucked into the tower, where it passes through a multitude of wind turbine generators clustered around the structure. The tower will cost an estimated $250 million to build, with construction expected to start in 2007 pending receiving a $75 million grant from the Australian government.

The two enhancements are:

1. The efficiency of the collector zone, which is substantially increased by replacing a portion of the collector with a vastly improved system. The air heaters are different from other direct gain mechanisms as solar energy is captured by two mediums: a glass plate and a metal plate. This configuration greatly reduces heat loss through reflectance, radiation and convection resulting in greater efficiency and durability.

2. More energy will be collected and stored via a heat storage facility which will provide base load capability for energy generation, in-turn providing the Solar Tower the ability to meet both shoulder and peak demand. Power can be generated by the facility 24 hours, 365 days per year, if required. Saltwater ponds sit outside the solar collector and trap heat in layers of saltwater during the day. At night the heat is released to power the tower's turbines. Solar radiation is captured in the ponds and stored in the bottom level of the ponds where the heated liquid can be continuously extracted at 35oC to 50oC above ambient temperature. Heat can be delivered to the collector zone, the region beneath the collector, via a heat exchanger which in turn further heats the air within the collector zone providing a greater differential in temperature and enhancing the ability to maintain air velocity sufficient to generate high load factor power day and night, throughout the year .

The enhancements allow units to be constructed with a smaller footprint, regardless of their nameplate capacity, and operate with a much greater efficiency or capacity factor. In essence the new technology developments, created by EnviroMission and protected as intellectual property, allow the Company to get ‘more from less’ out of the Solar Tower.

An analysis by Waterville Investment Research in New York concluded that a 50-megawatt solar tower would be competitive with other renewable-energy sources, while a larger version could produce electricity for the same cost as conventional power plants, and possibly less.

The 50-megawatt Tapio Station plant is just the small model: A half-mile-tall version is in the works for China, and EnviroMission is scouting sites in the American Southwest for other possible sky-scraping power plants.

The enhancing technologies and the Australian government's creation of the Low Emission Technology Development Fund [LETDF] led EnviroMission last year to downsize the solar tower plant to 50 megawatts. EnviroMission bought 24,000 acres of Tapio Station, the wheat and sheep farm located near the southwest New South Wales town of Buronga. State Significant Development status has also been granted to the project by the NSW State Government recognizing the significance of the project to NSW and has passed the planning approval process to the NSW Minister for Planning ensuring a streamlined approach to the planning process.

After four years and 17 capital raising's, Enviromission is trying to grab an $75 million piece of $370 million allocated to low-emission energy projects to keep its dream alive, a decision is imminent. It successfully met the terms for applicants to the LETDF. Successful applicants of the LETDF will be eligible for 2:1 dollar funding of project capital cost to demonstrate low emission technology using new intellectual property with the potential to deliver commercial large-scale energy generation and emission abatement set out in the program's 2030 targets. EnviroMission lodged its application in line with the 31 March, 2006 LETDF application deadline and joins a list of 30 potential applicants awaiting the formal assessment process ahead of an announcement early in the new financial year.

The initial design was a massive structure and too big a risk for investors. The station was to be a 200-megawatt monster with a 3,300-foot-high tower surrounded by a 4.5-mile-wide solar collector. The tower would have been nearly twice as tall as the tallest structure on earth, the CNN Tower in Toronto. "People thought I was stark raving mad," said Roger Davey, chief executive officer of EnviroMission. "They said you couldn't do it, that it would never be commercial because it was so big and such a construction nightmare." Not to mention the estimated $800 million to $1 billion price tag.

This is one of the most interesting technologies I have seen, if only they could build one, they have been trying to get financing for years. Continuous power from a solar source without complex energy storage. Capital cost of $5000/kW is very expensive, about twice that of a nuclear plant, but with much lower O&M costs and no fuel costs. This comes out to $0.09-$010/Kw without any susidies, which is may be lower than any other renewable energy plant. Wind? They claim they want to compete with coal.

Resources:

Tower of Power, Todd Woody, CNNMoney.com, July 20, 2006
EnvroMission Limited, South Melbourne, Victoria Australia

Source: EnviroMission's Solar Tower Of Power