When client Hans-Erich Schilling decided to build a biomass power plant on the outskirts of the village of Schwendi, in southern Germany, he knew good design was imperative. New interventions here, on the fringes of the Alps, must complement the idyllic landscape and not offend the locals, who tend to be skeptical of new ideas. Schilling, whose family has operated a sawmill for 200 years in this region, required cost-effective heat for his business. Federal incentives made the construction of a green power plant viable, but district council approval was required.
Location Schwendi, Germany (Rhine River watershed)
Gross area 10,794 ft² (1,000 m²)
Cost $10.75 million (8.2 million euros)
Program Biomass power plant, office space
TEAM & SOURCES
Windows Glasbau Wiedermann
Skylights Hans Börner
Doors Glasbau Wiedermann
Seeking a high-profile architect, Schilling turned to Milan-based Matteo Thun, whose recent, large-scale buildings dot the Alpine region. By commissioning a prominent architect to create a stand-out biomass power plant, Schilling hoped to encourage local interest in sustainability. Indeed, Thun's building celebrates green energy production while respectfully integrating itself into the rural landscape. This commitment to design quickly paid off when the scheme easily passed the review process.
The power plant sits on a steep slope and can be glimpsed from the surrounding valley. To visually break down its scale, Thun designed the complex as two structures. A long shed situated parallel to the slope houses a loading dock where organic materials are sorted and mixed. From the shed, materials are transported on a slow-moving underground track to the glass cube where combustion takes place. Heat and electricity are produced using an Organic Rankine Cycle (ORC) machine. This system heats silicon oil to 365 degrees Fahrenheit (185 degrees Celsius) to produce silicon steam, which moves a turbine to generate electricity. Water, which is used to condense the steam back to oil, becomes heated and delivers thermal energy.
The client's sawmill uses most of the heat and sends the remainder to a nearby hospital via a district heating network. Electricity (sufficient for the needs of 1,450 single-family houses) is fed into the grid managed by the regional energy provider.
To allay local fears about the potential dangers of a biomass power plant and to demonstrate the efficiency of green energy, the architect put the workings of the machine room on display by wrapping the cube in transparent glass. "It's like looking under the hood of a Ferrari," notes Florian Koehler, a collaborating architect with Thun's office.
A circular exterior screen made of intersecting larch posts veils the top half of the cube. Recalling an oversize country fence, the post structure softens the glass's reflection and glare, provides shading, and adds a natural contrast to the cube's industrial surfaces. The larch is nano-impregnated to prevent moisture absorption and preserve the wood's reddish-brown color. The posts extend past the eaves to make the domed, zinc-clad roof appear less imposing. The east elevation's terrace, accessed by an exterior stair, serves as an exit for the offices and the machine room's topmost level.
At the client's request, the architect created bionic forms, such as the underlying roof structure, which resembles a spiderweb and the roof beams, which suggest palm fronds. The architect also directed an underground stream to flow around the building and through long rectangular concrete pools located at the base of the cube. The pools are decorative, and the staff keep fish in them, another gesture to assure locals that green energy is clean and safe.
Upon completion in 2008, the plant produced heat and electricity, but the client was eager to lower operating expenses to ensure the plant's long-term viability when the start-up subsidies expire. Dieter Baumann, a location-based engineer specializing in biomass power plant optimization, was called in. During weekly visits over a 12-month period between 2009 and 2010, Baumann focused on reducing the cost of the combustibles. Different mixtures were tried and now half of the fuel is waste material from the client's sawmill, in the form of tree bark and wood chips, which are pressed into pellets, sold to stables to absorb liquid manure, and then returned to the plant free of charge.
The client's enthusiasm notwithstanding, the Schwendi biomass power plant was only possible due to recent federal legislation. Germany's Renewable Energy Sources Act, passed into law in 2000, dictates that energy concerns purchase electricity from renewable sources and guarantees a set price for compensation for a period of 15 to 20 years. The use of innovative technologies (such as the ORC machine) and renewable natural materials to produce electricity earn additional incentives. The savings and loan association in the nearby city of Biberach, which is mandated to invest locally, provided financing for the Schwendi plant.
A range of green infrastructure has appeared in Germany in the past decade, but clients tend to embrace cost-effectiveness over investing additional resources to create good design. The Schwendi biomass power plant counters this thinking and proves that a green power plant can gracefully fit into a natural context, an approach that Thun calls "an aesthetic form of ecology."
The Schwendi plant is now a regional attraction and offers weekly tours. Although the specialized design added roughly 20 percent to the final cost of the project, the members of this family-run business remain convinced that good architecture and green technology are sound investments. They also pride themselves on their role in changing local attitudes about sustainability. One of the clan's younger members, Johannes Schilling Jr., observes: "People driving by stop and say 'What's that?' and then we know we have reached our goal."