Page 53 - Designing for Zero Carbon - Case Studies of All-Electric Buildings

Daylighting and Electric Lighting
The natural daylight level is harvested on the south end of building by using the exterior blind system, which adjusts the angle and spacing of the louvers in response to the angle of the solar incidence as measured by a photocell detector. Thus the collection of glare-free daylight can be maximized while providing full shading of the curtain wall glazing.
Daylight controls on the LED electric lighting system provide the required reduction in electric light levels in response to measured daylight available. Occupancy sensors add to the energy- efficient operation of the electric lighting system.
Heating, Ventilating and Cooling Systems
For the relatively brief time of the year when mechanical cooling and heating may be required, a small heat pump is used. The heat pump is connected to multiple-zone fan coil units with vari- able refrigerant flow (VRF) lines in a small but very efficient system. By modulating refrigerant flow depending on the particular loads of a zone, just the right amount of heating or cooling is delivered to the zone.
The entire building is served by the VRF system, including the first floor restaurant and retail spaces. Each of the office floors has a dedicated outdoor air supply unit (DOAS) to provide fresh air; each DOAS unit has an energy recovery feature that exchanges thermal energy between the incoming outdoor air and the outgoing exhaust air. The small size of the VRF system also has the advantage of simply occupying less space on this limited site. In fact, the bulk of the equipment is located on the roof underneath an elevated solar photovoltaic panel array.
There is some added energy savings due do the demand control ventilation (DCV) system, which minimizes the amount of fresh outside air introduced into a space depending on the measured CO2 concentration there. CO2 sensors located in the space determine whether fresh outside air needs to be delivered there. There is a slight savings of fan energy and, on occasion, energy required to condition the outside air with the use of a DCV feature.
Building Management System and Control Systems Integration
MAKERS QUARTER BLOCK D OFFICE BUILDING CASE STUDY NO. 2
The operation of the natural ventilation system, including the control of operable windows and panels in the façade, the VRF system, the automatic exterior blinds, data collection and perfor- mance monitoring—all have control systems that are integrated by one master building man- agement system (BMS) to provide coordinated operation per the design intent. The different communication protocols of the various control systems (BACnet, Modbus, etc.) require this co- ordination, especially in modern “smart buildings”. The client opted for a BMS platform4 that au- tomatically controlled all the subsystem operations and recorded the overall performance data.
An example of this control system coordination is the operation of the automatic exterior blinds and the natural ventilation system components. As the sun tracks toward the southwest, the blinds would close to minimize heat gain as the day warms up and solar heat gains intensify. In concert with this, the thermostat would signal when the rear doors and front openings would need to open to manage the internal space temperature. The comfort range defined in the BMS is expanded beyond the typical range to allow for greater temperature swings to be associated with natural ventilation. The BMS switches the system back to the tighter comfort range as
the internal space temperatures rise too high; the openings are simultaneously closed and the mechanical VRF systems are activated.
4 LOCBIT: https://www.locbit.com/
Designing for Zero Carbon: Volume 1 39
(Opposite) An excerpt from the BMS diagram for the Block D office building.
(Courtesy Syska & Hennessy)