Modeling and Design of Net ZEBs as Integrated Energy Systems - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 80

Lehmann, Dorer, and Koschenz, 2007; Xu et al. , 2010). Examples for
ventilated systems include ventilated concrete slabs (VCS) (Chen, Galal,
and Athienitis, 2010b) and ventilated masonry block walls (Howard, 1986).
Research on the efficient utilization of VCS in cooling applications for
commercial buildings has been conducted by several groups (Ren and
Wright, 1998; Winwood, Benstead, and Edwards, 1997). The air channels in
these systems are often used as ventilation ducts. In this case, they integrate
TES, space conditioning, ventilation, and structural systems into one. The
air flow can be open-loop (inlet and/or outlet air mix with room air) or
closed-loop (no mixing), and it is possible to switch based on applications
(e.g., open-loop in slab cooling and closed-loop in slab heating). Open-loop
ventilated systems have been shown to provide stronger thermal coupling
between high-mass slabs and room air (e.g., higher total convective heat
transfer rate, and direct mix of room and channel flowing air) and hence to
significantly reduce space conditioning load (Braham, 2000). Oswald and
Sedlbauer (1995) suggested hygienic maintenance on open-loop systems.
Active charge and discharge BITES systems (e.g., hydronic or ventilated
systems) with proper design and control have the following additional
advantages compared to isolated thermal storage systems:
- They exploit the large space conditioning potential of the building
fabric in a space-efficient and cost-effective way. Active charge/
discharge enhances the TES function and adds TES to the original
functions of the building component (e.g. structural and architectural)
with reduced material cost.
- Active charge and discharge design can be used to reduce peak
demand.
- Active BITES can be utilized to improve thermal comfort by reducing
room temperature fluctuations and drafts. Ceiling/floor located active
BITES systems may evenly discharge thermal energy directly into
occupied space by radiation and convection. This reduces surface
temperature differences and radiant temperature asymmetry. Thermal
comfort is also improved with enhanced direct radiative heat exchange
between occupants and active BITES systems (ASHRAE, 2009c; Feustel
and Stetiu, 1995; Inard, Meslem, and Depecker, 1998).