RAFAA just submitted a design proposal (invited competition by www.brightsourceenergy.com) for the world largest solar plant in California.
Certain worldwide phenomena, such as global warming, shortage of resources and environmental pollution, have changed the relationship between man, nature and technology. These changes have caused a state of imbalance in the last decades. With the recent Deepwater Horizon catastrophe, the established energy industry and its infrastructure have suffered a major blow to their public image. The proposed projects will not only show solutions both for the functional assignment and for strengthening BrightSource Energy’s innovative image, but will also depict the appropriate attitude towards these challenges.
We want to give BrightSource Energy a strong image as a reliable leader in the field of sustainable technologies. The Solar Plant Towers will serve as a powerful statement to ensure the company’s share in the fast growing solar technology market. The slogan “Clean, Reliable and Low Cost Solar Energy” has been the starting point for our deliberation and has led to two different approaches.
The first proposal strictly adheres to the given budget and time frame and tries to have the greatest impact possible without having to fall back on major adjustments to the existing concept. The second proposal demonstrates a long-term strategy for BrightSource Energy.
BrightSource Energy and light are intrinsically entwined. Light moves at different frequencies as wavelengths through space. The physical characteristics of light waves have been translated into a vertical and three-dimensional form. It consists of helices rising at different speeds and frequencies, creating a structure that is able to react to the static parameters with different densities and openings and allowing for a peek into the inner workings of the “machine”. Thus, the technical module becomes perceptible and the visual impact on the landscape is reduced. The dissolution of the structure leads to a blending of the tower with the sky and thus, symbolically, to a bond between technology and nature. The organic and open structure can be understood as a counter proposal to the monolithic and concealed architectural language of conventional infrastructure projects. The project reveals an understanding of how the system works to the public and allows for a multitude of visual associations. The size and position of the openings have to be analyzed so that they can have a positive effect on the tower’s aerodynamics.
In collaboration with the engineering company Schlaich, Bergermann and Partners, we have evaluated different construction methods and developed two approaches; both are based on a model with a diameter of 64 feet.
A construction in precast concrete is possible. The individual precast elements would be transported and assembled on site, and connected in a force-fitting manner (steel structure for tension). The maximum size of the elements is limited by the transportation and the steel joint requirements are high due to the possibility of earthquakes. This solution will deliver the strongest architectural quality, however, the costeffectiveness of this method is arguable – even with a large number of towers. This is the reason why we have also considered the possibility to implement the concept in the slip-form or climbing formwork procedure.
The tower’s surface would be smooth and the openings would have to be constructed with sacrifice shuttering. In order to reduce the costs of the formwork, it would be assembled with small modules, which can be combined to create larger openings. The position and the size of the openings would have to be arranged in a manner that allows for the vertical distribution of forces and the diagonal bracing (see façade diagram). Due to the industrial character of the entire plant and the distance between the viewer and the tower, we think that a punched-holes solution would also be possible. It seems that this solution would require the least amount of adjustments to the original concept in terms of cost effectiveness, scheduling and construction processes.
We agree that the decision in favor of a concrete construction in the slip-form procedure is without doubt the most effective solution with regard to cost effectiveness. However, we would also like to think that this project can be used to establish BrightSource Energy as a leading company for renewable energy and as a true leader when it comes to sustainability. BrightSource Energy has already made the reduction of their environmental
impact as one of their most significant basic principles. The company went to great lengths to leave the local flora and fauna as intact as possible. This was taken into consideration by developing a specific solution for the foundations of the heliostats. For the credibility and integrity of the company, it makes sense to also apply this criterion for the construction of the tower. We do know about the cost pressure and the strong competition in the field of solar energy, but we are convinced that these investments will increase support by the general public, environmental organizations
and public authorities. This will consequently contribute to the success of the project; one that tries to be responsible, strike a new path and do the right thing.
Thus, it is important to take into account not only economic criteria, but also factors such as sustainability and ecological impact in order to assess the project. The essential question is not “How much does the tower cost today?” but “How much does the construction, maintenance, dismantlement and recycling of the tower cost in terms of its entire lifetime, CO2 footprint and environmental impact?”
This is why we have analyzed the use of a steel construction and have come to the following conclusions:
- In principle, the production of steel uses much more energy and produces 6 to 10 times more greenhouse gas emissions per ton than concrete. This can be counterbalanced by building a much more delicate construction with accordingly less weight.
- Almost 100% of steel can be recycled. Concrete, on the other hand, can hardly or never achieve this level due to its many additives.
- With a modular steel construction, the negative impact on local nature during the erection and dismantlement of the tower is much less than when using an in-situ concrete construction or at a later demolition.
- A steel construction can easily be dismantled and erected at another location or be expanded or replaced by a more modern plant.
- If the price of steel continues to rise at such a fast pace, you can theoretically count on additional profits in the case of a sale of the tower in 40 years: an investment for the future.
- The development of an integrative system from a single source should be the long-term technological goal for the 250 MW Solar Tower. In this development, there should no longer be any differentiation between the technical modules and the supporting tower for the SRSG. Both of these components have to be combined into one system. In the long run, this is the only way for synergies and, thus, savings to be achieved. This is why we have also developed a steel-frame structure alternative.
You can find in BrightSource Energy’s logo a Hebrew word referring to the biblical story of Jacob’s ladder and the city of “Luz”. We have tried to find an abstract form that is instinctively associated with the idea of a ladder to heaven. This form can be characterized as a movement consistently rising towards the sky. The result is a rectangular footprint, which rotates by 45 degrees, rising towards the sun, so to speak. The form is meant to stay open for interpretation and does not try to follow any short-lived trends. It can alter its identity over many decades, as the company’s image might change. The openness is the real quality of this concept. Other associations such as references to aquatic plants are equally intended and welcomed.
The tower consists of prefabricated 40-foot elements with a footprint of 58×58 feet. The elements are assembled by a power crane – similar to the erection method of the technical modules. Afterwards, the technical modules will be joined with the outer tower, thus forming a space truss. Between the twin steel columns, louvers run in the upper and lower area. The louvers allow for a visual opening in the center of the tower. The form and dimension of the tower correspond with the construction axis of the SRSG. Due to the rotation in the middle, the tower tends to deform under heavy loads. This is why the use of additional fortification at this position has to be checked.
The long-term strategy is a reduction of costs for the technical module. In this case, the tower would consist only of an outer construction tower of 49×49 feet; the technical installations could “hang” inside the tower. In past experience, Schlaich, Bergermann and Partners have already looked into similar approaches. However, this proposition is to be understood as a future vision and needs to be further researched.
Solar Plant Towers, Ivanpah
location: Mojave Desert, California
client: BrightSource Energy Inc.
status: competition stage
D U N E D I N A R T S
Architekten ETH I MSc Digital Design
8045 Zurich, Switzerland
Schlaich, Bergermann und Partner
70178 Stuttgart, Germany