P h o t o v o l t a i c s a n d ( N e a r l y ) N e t Z e r o E n e r g y B u i l d i n g s
303
Table 1: energy production for 1 m
2
PV module, optimal tilt and azimuth angles for the selected
latitude, power density 120 W/m
2
. The estimation is based on JRC PVGIS calculations for 1 kW
p
,
crystalline silicon technology (8,3 m
2
PV modules surface) [JRC PVGIS].
Rome
(tilt 36°, azimuth -1°)
Berlin
(tilt 33°, azimuth -3°)
Oslo
(tilt 32°, azimuth -1°)
Average sum of global irradiation
received by the modules, total for
year (kWh/m
2
)
1680
1150
1000
Average monthly electricity
production by 1 kW
p
system, total for
year (kWh/year)
1260
877
778
Average monthly electricity
production for 1m
2
crystalline silicon
PV module, total for year
(kWh/m
2
/year)
152
105
120
What are the possible architectural implications of this shift?
In the following will analyze the concept of Net ZEB, and its relationship with the
architectural design, so to emphasize potentialities and challenges in using PV in Net
ZEBs.
1. The Net ZEB concept(s)
Since the early 1990s various buildings and estate projects have been built all over the
world which claim to achieve a (completely) balanced annual budget for the operating
energy or carbon emissions.
As investigated in the IEA research group, in the past twenty years a variety of actors
created projects according to different balance approaches. Until now more than 300
known projects were developed all over the world, but for defining such buildings as Net
ZEB a wide variety of definitions was used, with the consequence of having many
balance approaches and many solution sets [Musall 2010; Musall 2012a]. In particular,
depending on the point of view, there are several ways to define Net ZEBs: they are
called “(net) zero energy building”, “carbon-neutral home”, “equilibrium building” or even
“energy plus building” [Voss Musall 2011]. In the following, will describe the main issues
to consider in defining a Net ZEB.
Initially Net ZEBs have a simple, common goal, which is a neutral result for an energy or
emission balance, which should be achieved in the very most cases in a period of one
year.
It is normally reached at the individual building level by a two-step concept: (1) reducing
the energy demand (by energy efficiency and passive measures) and (2) generating
energy (e.g. by PV, combined heat and power plants (CHP), wind turbines or ST
collectors).
The modifier “Net” indicates that the goal of the ZEB refers to a calculated balance
between energy demand/supply and energy generation/export to grid(s). The identified
balance concepts behind these buildings are hardly comparable, do normally not
represented national standards and differ in the following categories [Sartori 2012]:
1.
Choice of an “indicator” (final energy, primary energy, equivalent carbon emissions,
energy costs, etc.);
