Systems for the building envelope concept made real in an office vision
The task are completed with the following results. 1) New glazing systems with a balance between heat loss and solar gains: A new system for montage of glass with overlap connections has been designed, developed and tested.
The vision is to regulate the climate within a highly insulated glazed building envelope in order to create summer all year,- 'a pacific Island within evacuated glazing'. Within this building envelope is created a 'botanical garden-like' interior. As the indoor climate is protected from the weather, any kind of buildings and partition walls can be built. A large photovoltaic disk follows the sun, produces optimal electricity and shades the glass building from the direct sunlight to protect it against overheating. In an office building there is a good correlation between working hours, daylight, passive solar gains, and the stack effect to drive natural ventilation with heat recovery. On winter nights, the temperature in the thermally light building drops rapidly reducing the heat loss significantly. On winter mornings some heat is necessary before sunrise to reheat. However this heating is much more effective if it is applied right next to the person sitting in the building,- in the hot chair. The indoor environment is regulated individually and integrated in a automatic demand control system in order to achieve optimal 'user habits'. DTI plants to build office VISION in order to join the subtasks to complete the experimental project and to demonstrate that 0-energy goal of the Danish energy research programme (EFP) is achievable. Office VISION will be DTI's forum for R og D activies, collaboration and dissemination of sustainable technology. Subtask 1: New glazing system with balance between heat loss and passive solar gains. Subtask 2: New system for photovoltaics following the sun and shading the building. Subtask 3: Demand controlled 'hot chair'. Subtask 4: Demand controlled natural ventilation with heat recovering solar chimney. Subtask 5: Demand controlled individual indoor climate control and user interface
Calculations of indoor climate and energy consumption shows that the U-value must be below 0,5 W/m2K to achieve a balance between heating demand and energy production from PV on a yearly basis. The overlap is only an advantage if the glass is thin. To achieve an overall U-value of 0,5 W/m2K it is necessary with a centre U-value of 0,42 W/m2K for the overlap solution (1 m2 glass, 2x4 mm thickness) and 0,25 for the ordinary solution, such performance is not yet commercially available. Comfort calcuations show that a comfortable winter solution is possible with a U-value of 0,7 W/m2K. In the summertime overheating is a problem due to the absorption in the inner glass and consequently high radiation temperatures. The solar energy transmission should be below 20% to achieve a comfortable summer indoor climate. 2) New system for montage of PV tracking the sun: Initially a large 'disk' tracking the sun like the large satellite dishes was designed. The PVs were mounted on conducting wires and was transparent for the wind. This concept was abandoned as TI invented a more promising system described in the accepted proposal for EFP 98 with focusing PV systems integrated in the facade. 3) Demand controlled decentralised heating system: In the mean time investigations has shown that heating of the chairs and desk are insufficient as the hands and feet are still too cold. Working on laptops yours hands are already heated. Heated carpets can heat the feet. The Danish Thermo-floor company produces an electrically heated carpet. 4) Demand controlled solar chimney ventilation with heat recovery: Calculations shows that the all glass building can be ventilated by natural ventilation. It also shows a dramatic increase in energy consumption if the building is not very airtight. The main overheating problem is the high internal surface temperatures of the glass. This problem can be controlled by establishing a virtual solar chimney between the glass and a curtain on the inside. The heat can be recovered using a kind of passive heat pump transmitting the heat from the exhaust to the air intake by brine. 5) Development and test of demand controlled and individually controlled user interface: A complete new concept for decentralised control system was developed. This way the user interface is built into the system by the place and direction the controlling component is situated and by the way the receiving component is set to respond. This concept received funding from EFP 98
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