Building Performance Optimization of Net Zero-Energy Buildings - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 274

5.4 Application of Optimization: A Comfortable
Net-Zero Energy House
Optimization is a versatile technique that in this case study is used to
identify the most suitable technical solutions to guarantee a comfortable
environment inside a building and, hence, to minimize its energy needs
for space conditioning. This design strategy is a rational and promising
path toward Net ZEBs (Carlucci, Zangheri, and Pagliano, 2013; Pagliano,
Zangheri, and Carlucci, 2010). The European standard EN 15251 (CEN,
2007) also suggests a path, which starts with optimizing the building
envelope and its passive strategies by analyzing the building in free-floating
mode; the indoor thermal comfort is assessed with respect to an adaptive
comfort model (de Dear and Brager, 1998; Nicol and Humphreys, 2002).
However, in case thermal comfort requirements cannot be met only with
the building envelope and its passive strategies, efficient HVAC systems
are then introduced, and thermal comfort requirements have to be verified
against the Fanger comfort model (Fanger, 1970). In other words, this
means designing the building envelope for achieving thermal comfort by
using primarily passive strategies, so that, at the next step (if required),
efficient HVAC systems need only a limited amount of energy to provide
the required thermal comfort conditions. At the same time, efficient lighting
andelectricalapplianceshavetobeselectedtoreducetheelectricitydemand
of the building. Then, the overall energy required by the building has to be
covered by renewable energy preferably produced on-site (Marszal et al. ,
2011).
An automated computer-based workflow is applied to optimize a single
family net zero-energy house in the Mediterranean climate. It uses
EnergyPlus (Crawley et al. , 2001) as the building performance simulation
engine, guided by GenOpt (Wetter, 2001) as the optimization engine. The
identified optimal building variant reduces both the seasonal long-term
discomfort indices to values lower than 10% in free-floating mode. A
monocrystalline PV field with an area of 21.0 m 2 can provide all the needed
energy required by the house (on a yearly basis and via exchange with the
electric grid). In case the identified optimal building variant is equipped
with a reversible electric heat pump, the thermal comfort requirements
expressedwithrespecttotheFangercomfortmodelaremetwithadelivered
energy for heating of 7.3 kWh el /(m 2 a) and for cooling (sensible plus latent)