Solar energy use in buildings - Solar Energy Sciences and Engineering Applications - page 614

Cooling loads should be reduced as much as possible by a good external shading
system, efficient electrical appliances and night ventilation if possible. The remaining
loads have to be removed by air-conditioning equipment. Solar photovoltaic energy
can power electrical compression chillers and solar thermal collectors can be combined
with sorption chillers to provide cooling of buildings.
18.11 INFLUENCE OF THE URBAN FORM ON SOLAR ENERGY
USE IN BUILDINGS
The effects caused by urban design on solar energy use vary according to climatic con-
ditions. The main factors that affect daylight use and solar gains in buildings are the
distance between buildings, the height of the facing building, the orientation of and the
reflectance from the facing buildings, the size of openings and the size of the shading
device. The daylighting performance is especially significant for office buildings which
are characterized by high lighting energy consumption and where the productivity of
the employees is highly affected by lighting conditions. In residential building, electric-
ity consumption for lighting is much less influenced by daylight performance due to a
higher evening use profile.
18.12 RESIDENTIAL BUILDINGS IN AN URBAN CONTEXT
The urban shading effect was simulated using the dynamic building simulation soft-
ware EnergyPlus (see Figure 18.12.1) along with all obstructing buildings around the
simulated one. The model includes the reflectance from the obstruction surfaces and
an albedo factor is defined for obstruction buildings and the ground. Site densities are
defined as the ratio of built-up area to total area and these varied between 30% and
60%, as below 30% obstructions are nearly negligible and above 60% the buildings
become unrealistically close.
18.13 SITE DENSITY EFFECT AND URBAN SHADING
IN MODERATE CLIMATES
First the heating and cooling demand of a building type in the centre of an urban
structures is analysed as a function of site density (building 9 in Figure 18.13.1). In
a second step the influence of the position of each building within the urban setting
Figure 18.12.1 EnergyPlus models of multi family buildings for shading simulations with site densities
varying between 60 and 30%.