Zurich’s RAFA Firm has created a proposal for a mammoth “Solar Tower” to be implemented for the 2016 Rio de Janeiro Olympic Games, and, if built, it is destined to be one of the most talked-about structures in recent memory. Despite the name, the tower has very little to do with the concentrated mirror/hot salt solar power towers to which most people familiar with alternative energy are accustomed. Instead, the structure will incorporate a 105 meter tall edifice with several panoramic viewing areas and a bungee jumping platform. In addition, there will be large photovoltaic array at the base of the tower and a system that uses excess energy to pump seawater to the top of the tower, to be released downward to turn turbines when the sun is not out. The plans further call for one side of the tower to turn into a waterfall on “special occasions.” An overview can be found at http://www.rafaa.ch/rafaa/rio_de_janeiro.html.
As somebody with a degree in Cultural Studies, it would be remiss of me not to do a bit of cursory symbiotic analysis :). As worldwide awareness about sustainability issues has increased, Olympic organizers have tried to minimize the impacts on what is inherently a very energy-intensive fortnight. The Beijing Olympics bought renewable energy, planted trees, and recycled water, while the Vancouver Olympics were the first to show online metering of the Olympic buildings’ energy usage, and London’s Olympic organizers have promised the “greenest Olympics in history.” The Rio organizers seem to be moving in this direction, and a structure like this would certainly become an important landmark, immediately becoming as recognizable as Rio’s famous Christ the Redeemer statue. If completed, this would be the most audacious Olympic structure ever created, leaving even the gorgeous (and now deserted) Birds Nest Stadium of the Beijing Olympics behind. As a sheer wall of water studded with swirling LED lights (check out some of the artist’s renderings on the website—they are stunning) in full view of the beaches of Rio de Janeiro, it would showcase the possibilities for humanity when it thinks big, providing a tangible form to the hope of a future without fossil fuels. Further, this would immediately become the world’s most recognizable symbol of renewable energy, with the waterfall and the solar panels combining in a monument to the untapped possibilities of renewable energy.
Though there are very few specifics available, we do know that the architects plan to put the structure on Ilha de Cotonduba, a small island that overlooks the city. The pictures make the Tower look like a rectangle, so I will (completely arbitrarily—if somebody can find detailed information then by all means bring that to the discussion) choose 75 meters as the width of the structure. Assuming that the PV array will have the same surface area as one of the tower’s faces, I did some quick calculations to see how much electricity the system will create. Using the worksheet on http://eosweb.larc.nasa.gov/, I found the average daily insolation on Cotonduba to be 4.5 kWh/square meter/day, assuming the panels to be flat and facing due south. Assuming a reasonable efficiency rate of 20% for the panels, that gives about .9 kWh/m^2 on Cotonduba. With 7,875 square meters of PV panels, this would work out to a little more than 7 MWh from the array. Though this would not be enough energy to power the whole Olympics, a glance at the numbers from the Vancouver Olympics (available at http://www.venueenergytracker.com/home) shows that this would certainly power a good chunk of the Games.
As with pretty much every renewable energy system, there are sure to be NIMBY-related eyesore complaints, but such aesthetic conservatism is easily overcome, and there will probably be more people who like the way the tower looks than not anyway. However, there is a more substantive critique to be made. From what I can tell, the plans call for the tower to be built on greenfield (previously undeveloped land) on the island. Though this does make the tower stand out as the lone pinnacle on the island, it of course invites the sustainability critique that, since the organizers are building something where there was once nothing, they are inherently degrading the environment. I personally believe that the tower could be more striking, possibly revitalize one of Rio’s notorious favelas, and eliminate the sustainability critique were it located on brownfield within the city, but it seems that placing almost 8,000 square meters of PV panel in the middle of a city is not realistic. Just as with large solar installations in the Mojave Desert, the issue thus becomes whether the gains made by building the tower on Ilha Cotonduba outweigh the negative impacts on the pre-existing environment. Though it is not without much trepidation, I believe that they do.
The greenest building is the one that is never built; it is simply impossible to build any structure that has zero environmental impact. The Solar Tower will be an incursion onto land that once had no buildings onsite, if not exactly pristine wilderness. Therefore, it is imperative that as much care be taken as possible both to mitigate the environmental harm done by the Tower and to make its benefits great enough to drown out any possible opposition on sustainability grounds. The problem of energy storage is one of the greatest ones facing the alternative energy market today—the sun doesn’t shine all the time and the wind doesn’t blow all the time. The tower’s innovation, the waterfall-powered turbines, is a beautiful idea that can help drive further investments in energy storage innovation with its visibility. The Tower would also symbolize a Latin American commitment to shifting towards renewable sources of energy. In a region where much of the money comes from fossil fuel reserves, this would echo oil billionaire T. Boone Pickens’s commitment to wind power and help signal a newer, more technologically enlightened Latin America. Brazil is one of the largest economies on the planet and the Olympics are alongside the Super Bowl and the World Cup in terms of worldwide exposure—having such a symbol of commitment to renewable energy built for the 2016 Olympics has powerful connotations. Further, there are the concrete energy savings that the tower will produce. Though its construction will probably take a fair amount of energy, the project seems to be of the size that it can repay its energy debt quickly (this is of course speculation on my part and I would gladly step aside for anybody who could show me some verifiable hard numbers), and over 7 Megawatts of power that was not created through burning fossil fuels would save a large amount of CO2, while avoiding the environmental degradation that comes from coal mining/oil pumping, etc. While it is certainly not a slam dunk (I would urge the organizers to try as much as possible to find a site for the tower within the city’s confines), the Solar Tower would become a permanent landmark for alternative energy in the Americas and around the world. It will certainly build awareness, and if the project is done with enough care, the energy savings will be a nice bonus as well.