Abstract
In the present work, the sensitivity of near-surface air temperature and
building energy consumption to different rooftop mitigation strategies
in the urban environment is evaluated by means of numerical simulations
in idealized urban areas, covering a large spectra of possible urban
structures, for typical summer and winter conditions. Rooftop mitigation
stategies considered include cool roofs, green roofs and rooftop
photovoltaic panels. In particular, the latter two rooftop technologies
are simulated using two novel parameterization schemes, incorporated in
the mesoscale model Weather Research and Fore-5 casting (WRF), coupled
with a multilayer urban canopy parameterization and a building energy
model (BEP+BEM). Results indicate that near-surface air temperature
within the city is reduced by all the RMSs during the summer period:
cool roofs are the most efficient in decreasing air temperature (up to
1°C on average), followed by irrigated green roofs with grass vegetation
and photovoltaic panels. Green roofs reveal to be the most efficient
strategy in reducing the energy consumption by air conditioning systems,
up to 45%, because of their waterproof insulating layer, while
electricity produced by photovoltaic 10 panels overcomes energy demand
by air conditioning systems. During wintertime, green roofs maintain a
higher near-surface air temperature than standard roofs, because of
their higher thermal capacity and the consequent release of sensible
heat during nighttime. On the other hand, photovoltaic panels (during
nighttime) and cool roofs (during daytime) reduce near-surface air
temperature, resulting in a reduced thermal comfort. Green roofs are the
most efficient rooftop mitigation strategy in reducing energy
consumption by heating, and are able to reduce the energy demand up to
40% for low rise buildings, while cool roofs 15 always increase
consumption due to the decreased temperature. The results presented here
show that the novel parameterization schemes implemented in the WRF
model can be a valuable tool to evaluate the effects of mitigation
strategies in the urban environment. Moreover, this study demonstrates
that all rooftop technologies present multiple benefits for the urban
environment , showing that green roofs are the most efficient in
increasing thermal comfort and diminish energy consumption, while
photovoltaic panels can reduce the dependence on fossil fuel consumption
through electricity generation.