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the building is limited to a few special cases because the potential is low. [Voss Musall
2011]
By contrast, building-integrated CHP offers the option to export electricity beside heat is
generated and thus to gain credits offset against the energy supply. This is especially
true for systems running on biomass (lower primary energy conversion factors). CHP is
often used in larger residential projects and is also an option for non-residential or
renovated buildings. From the building integration point of view solar thermal collectors
are comparable with PV systems. But only a very few buildings examples are known
where big ST collector arrays generate a large amount of heat which is feed into local
heating grids to compensate the buildings own electricity supply in an annual primary
energy balance [Voss Musall 2011].
Whatever the case no real Net Zero Energy building exist without PV.
Figure 5: Matrix of used supply and generation systems. The study of approximately 200 out of the
300 known Net Zero Energy Building projects from European and North American countries (IEA
Task 40-Annex 52) dealing with the utilization of renewable energy generation/supply technologies
divided in different building typologies shows that all those buildings use PV. It should be
recognized that not only electricity generation technologies are mentioned while renewable
generated heat normally is not used to compensate electricity supply but the other way round. In all-
electric building concepts (no second energy carrier) it is often used in combination with solar
thermal collectors and heat pumps. Source University of Wuppertal, compare to [Musall 2011]
3.
Building Integrated energy supply options: Photovoltaics vs. Solar Thermal
Table 2 summarizes the energy demand for a single town inhabitant, and energy yield
for selected renewable technologies (JRC calculations, and the surface area
requirement for each energy supply option, which is the ration of above quantities. The
surface area requirement has been defined as the “building’s energy footprint”.
[Scognamiglio, Ossenbrink, Annunziato 2011]
As results from table 2, for an “average” standard building (energy consumption 100
kWh/m
2
/year) in a moderate region of Europe, the surface required for placing the
necessary energy supply (i. e. buildings energy footprint) to turn a standard building into
a Net ZEBs are quite big, and their size depends on the energy system efficiencies.
Despite wind is the most efficient technology, the only two technologies that is possible
to integrate easily into the building envelope are PV and ST, and their efficiencies are
comparable.
