Building Performance Optimization of Net Zero-Energy Buildings - Modeling, Design, and Optimization of Net-Zero Energy Buildings - page 272

DHW), two efficiencies ( η SHS and η DHWS ) are considered as being
consistent with the Finnish regulation. Based on the installed space heating
system (electrical radiator, water radiator, or floor heating), the distribution
efficiency ( η dist ) is assumed to be 94, 84, or 87%, respectively ( Table 5.2 ) .
The implementation of a flat-plate solar thermal collector reduces the
domestic hot water demand Q DHW by d Q DHW . When mechanical cooling
( Q c ) is needed, it will take place for a short period. Therefore, the coefficient
of performance for the cooling system for nominal operating conditions
(25 °C outdoor air temperature) is used. Only 13 simulations are carried
out to calculate the cooling energy required for the Group 2 solutions.
Implementing the mechanical cooling options, with a 25 °C indoor
temperature setpoint, reduced the DH 27 ( Eq. (5.2) ) of the Group 2 solutions
to zero.
Figure5.11 presentsimprovements totheenvironmental viability of Stage -2
building envelope and HVAC-system optimal solutions ( Figure 5.10 , front
1 and 2) by implementing optimal sizes of RES systems (solar-thermal and
photovoltaic collector areas). A simulation-based optimization model is
developed, using MATLAB 2008b and IDA ESBO (a building performance
simulation program that includes the possibility of implementing RES
systems),tofindtheoptimalcombinations ofthefront1and2solutionsand
the RES options (from 0 to 31 m 2 solar thermal collector areas and from 0
to 71 m 2 photovoltaic array area). The optimization is performed by PR_GA
approach (Hamdy, Hasan, and Siren, 2009).