sbp sonne gmbh
First demonstration loop integrated in a solar power plant in California
The Ultimate Trough is the 3rd parabolic trough collector generation developed by schlaich bergermann und partner, sbp sonne gmbh and several partners. The company holds the worldwide distribution right on this collector.
A first Ultimate Trough (UT) collector test loop was successfully integrated in an existing solar power plant in California. Compared to the Eurotrough, the very successful first collector generation, the size of the new collector has more than doubled. The Eurotrough has already been integrated in many multi Megawatt parabolic trough power plants all over the world. With the new UT collector design parabolic trough plant competitiveness is expected to rise by 25 % and will thus contribute significantly to further cost reduction of future parabolic trough power plants.
Fig. 1: Ultimate Trough® test loop installation, California
In 2010 schlaich bergermann und partner (sbp) and Fraunhofer Institute for Material Flow and Logistics (IML) started under the leadership of Flabeg Holding GmbH (Flabeg) the development of the next generation collector for parabolic trough power plants. The project is based on the decision of Flabeg, being the market leader for parabolic shaped mirrors, to serve the market need for a collector design with lower field cost and a special suitability for large solar fields.
The new collector design, the so-called Ultimate Trough® design, was developed with an aperture area of 1,689 m² and an aperture width of 7.5 m. A first prototype collector had been built in a German production hall in 2011. Detailed photogrammetry and deflectometry measurements confirmed the excellent optical performance of the collector.
Fig. 2: Ultimate Trough® prototype (2 SCEs), Cologne, Germany
With the Ultimate Trough®, the industrial partners are focusing on large scale solar thermal power plants in the range of 50 250 MWe. Profiting from the economy of scale effect, such plants will further decrease costs and make solar power plants competitive even to fossil fuel power plants. The Ultimate Trough® is intended to serve the demand for such larger PTC power plants. These new very large dimensions are realized without compromising stiffness of the support structure, or increasing deformations under operation loads, while simultaneously improving optical performance.
The Ultimate Trough® demonstration loop will be continuously operated for one year; specification for the full size commercial collector field will be finalized early in 2013.
Special Features of the Ultimate Trough®:
Mirror gaps for wind load reduction:
Several measures for wind load reduction for the new collector were investigated in wind tunnel tests. Mirror gaps were enlarged to serve as venting gaps to equalize wind induced pressure in front and behind the mirrors. Conventional minimum gaps between the mirrors behave like completely closed parabolas, as small gaps do not allow for sufficient pressure equalization. On the other hand, very big gaps enlarge the gross aperture significantly, thereby reducing optical efficiency. An intermediate optimum was found when designing the Ultimate Trough®. The 200 mm wide gaps between the inner and outer mirror help to decrease wind load factors by up to 30 %.
Cost reduction by "going large":
sbps evolution of parabolic trough collector dimensions over three development cycles is shown in Fig. 2. It is expected that specific costs of a large solar field employing UT-technology will be lower by around 20 % as compared to Eurotrough technology. This is mainly achieved by doubling the aperture area per collector.
Fig. 3: Evolution of parabolic trough collector sizes over 3 development cycles at sbp (Eurotrough, HelioTrough, Ultimate Trough®)
By doubling collector aperture area, the number of drive units, sensors, control elements, pylon foundations, loop specific piping, and erection procedures is halved. A huge cost reduction can be achieved by reducing solar field assembly costs: By reducing the number of solar collector elements by 60 %, related labor costs are reduced by around 30 %.
The development is co-funded by the German Federal Ministry for the Environment, Nature conservation and Nuclear Safety, reference no. 0325232.
About schlaich bergermann und partner, sbp sonne gmbh:
schlaich bergermann und partner, sbp sonne gmbh are consulting engineers and technology developers for solar power plants with 30 years of experience in feasibility studies, design, planning, optimization, erection and commissioning of CSP systems.
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