Lilies Zero-Energy Modular Buildings
Client: International Solar Energy Society / China National Engineering Research Center for Human Settlements / Chinese Renewable Energy Society
Typology: residential
Year: 2007/2008
Place: Beijing, China
International architectural design competition. Prize for Technical Excellence.
Modular, Energy‑Self‑Sufficient Buildings in Beijing
The residential units of the “Lilies” project are composed of three independent housing blocks. Like the flower that gives the project its name, the cluster of buildings rises above a body of water and, thanks to solar radiation, is able to meet its own energy needs. The required electrical power is generated by nine Stirling engines, a type of generator that produces electricity by exploiting temperature differentials. The heating and cooling system is based on a heat pump that draws energy from the water basin.
The individual housing blocks are attached to a modular steel load‑bearing structure and are arranged along the perimeter of the plan, leaving the central space free for the stairs and walkways that provide access to the apartments. Each apartment is based on square modules measuring 60 centimeters per side; each module contains low‑voltage wiring with power and data outlets, as well as four LEDs. As a result, any point in the space can be transformed into a light source or a connection point for electrical equipment.
Technology
Each apartment block is equipped with eight Stirling‑Solar units produced by SOLO Stirling GmbH, capable of generating up to 8×8 kWp under Beijing’s average climatic conditions. The Stirling engines exploit the temperature difference between a “hot chamber”—heated by solar radiation through a parabolic concentrator—and a “cold chamber” cooled by the water of the underlying basin.
Passive Solar Solutions
Winter: Through the building envelope, solar heat is transmitted into the dwellings, with an additional contribution provided by the reflection of sunlight on the water basin. The cladding of the inner courtyard also retains heat, which is redirected upward through the open shaft of the stairwell and circulation system. The main heat source is supplied by heat pumps fully powered by a series of Stirling units, bringing net CO₂ emissions to zero.
Summer: The external envelope—formed by terraces and aluminum supports that, together with vegetation, create a brise‑soleil system—prevents solar radiation from overheating the residential units during the summer season. Natural ventilation is enhanced by exploiting the low‑pressure effect generated by the wing‑shaped form of the solar concentrators positioned above the courtyards. The thermal mass of the water basin also contributes to the overall cooling effect. The courtyard at the center of each building functions as a ventilation chimney, creating an upward airflow that naturally extracts overheated air.
Data
Area of the residential units: 38 to 76 sqm | Site area: 1,680 sqm Total residential floor area: 7,200 sqm Height of the blocks: 15.9 meters | Floors: 6, of which 5 are residential.
