الفهرس 
Energy CrisisOnly 14 pages are availabe for public view
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Abstract
from the theoretical part and practical part, many important results
could be concluded:
Energy crisis that Egypt facing nowadays is mainly due to
overconsumption of its traditional energy resources to compensate
negative consequences of highly glazed facades trend in terms of indoor
thermal comfort.
It is necessary to increase awareness of improving indoor thermal
performance, thus building energy efficiency. Especially that the
extensive utilization of air conditioning equipment has dangerous effects
on the surrounding environment. It leads to increase the pollution level
due to the resulted Co2 emissions.
As façade is the mediator between indoor and outdoor environment,
it could control heat gain rate thus having the capability to improve
indoor thermal performance. In this respect, integrating glazing
technologies in building facades is considered the best solution to
accomplish indoor thermal comfort.
Semi-transparent photovoltaic (STPV) glazing technology is
considered the most promising glazing technology that has a direct
impact on improving indoor thermal performance. Also its role of
generating electricity could contribute to the utilization of renewable
resources in Egypt which would be one of the efficient solutions that can
help in solving problem of energy crisis.
STPV is one of new emerging photovoltaic (PV) types that is low
cost with high efficiency and more flexibility that can be integrated in
many parts of building envelope especially the transparent part.
Exposing STPV for conditions such as high level of temperature and
shading caused by the surroundings could affect efficiency of STPV to generate electricity that mainly leads to overheating of cells thus
affecting thermal performance.
Although PV system doesn’t have any mechanical parts, it still needs
a preventive maintenance once every six months to guarantee high
efficiency of PV cells. Also it definitely needs a formative maintenance
that should be done in case of damaging any part of PV system parts.
Integration of PV in building envelope is considered a preferable
solution from economic point of view. This solution is called BIPV. It
can save cost of the traditional construction materials of building
compared with solution of being added to the building envelope which is
called BAPV.
Semi-transparent photovoltaic could be obtained in three
transparency styles such as matrix-based, process-induced and intrinsicbased.
Transparency style of matrix-based couldn’t provide a full view to
the outdoor due to existence of obstructive parts that could make this
style isn’t preferable for occupants. However, process-induced and
intrinsic-based styles have a transparent appearance without any blocking
parts thus having the capability to provide full view to the outdoor.
STPV is one of PV types that could play a multifunctional role when
integrated in building façade. It can improve visual and thermal
performance in addition to its main role of electricity generation. But
some of these functions compete with each other. Thus, balance should to
be attained between them to get the efficient performance of STPV. This
balance could be obtained through investigating all functions of STPV
individually and in combination to get the efficient design of STPV
windows.
Achieving the maximum thermal savings by integrating STPV in
building facade depends on obtaining the efficient design for STPV
window which is correlated with many parameters such as electrical
efficiency, thickness, number of layers, window to wall ratio (WWR),
optical and thermal properties. Some of these parameters affect thermal
performance of STPV directly while others affect the efficiency of power generation of STPV. The inappropriate design for parameters that affect
the efficiency of power generation of STPV may result in overheating
occurrence thus affecting indoor thermal performance negatively.
Climate of Egypt is divided into eight climatic regions.
Consequently, three governorates in three different climatic regions are
chosen as cases to get impacts of different climatic conditions of Egypt
on thermal performance of STPV.
Integrating Design Builder software with Energy Plus could be used
easily in energy simulations to calculate the thermal (cooling/heating)
loads in addition to artificial lighting loads.
In case of not using lighting control system, increasing visible light
transmittance (VLT) or window to wall ratio (WWR) of glazing elements
increases the cooling demand because the solar heat gains became higher.
In case of using the artificial lighting control system:
Increasing VLT or the WWR of glazing elements decreases
the lighting demand due to higher daylight penetration.
Single clear glass (Sgl Clr) has the lowest artificial lighting
loads due to having the highest transmittance degree.
In case of not using lighting control system for all three investigated
cases study, there isn’t any combination of STPV that isn’t efficient to be
used. All simulated STPV combinations are improving the thermal
performance compared with Sgl Clr. However, in case of using lighting
control system in all three investigated cases, some inappropriate STPV
elements are emerged. This is due to that using the lighting control
system revealed the bad lighting performance for them.
Using lighting control system raised the percentage of cooling saving
accomplished by STPV glazing element in all three cases; Cairo,
Alexandria and Aswan.
In all three investigated cases study either in case of using lighting
control system or not, STPV10% with WWR=100% achieved the highest cooling savings despite of the difference in climatic conditions for the
chosen three cases. But it was more efficient in Alexandria than Cairo
and Aswan. It saved more cooling loads in Alexandria. Generally, in all
three cases, it can save almost half of cooling loads.
Despite of the low VLT of STPV 10% with WWR=100%, its
cooling saving percentage in case of using lighting control system in all
three cases is higher than its cooling saving percentage in case of not
using lighting control system in all three cases study. This is due to the
highest WWR for this combination that could provide more daylight.
There are many combinations of VLT and WWR for STPV that can
accomplish the same cooling performance. The decision of using any of
those combinations either by preferring the elements of less transmittance
or preferring façade with bigger openings is very critical. This is because
in such cases not only the efficiency of the building cooling performance
should be taken into account to define the appropriate facade solution,
but also other elements such as the building façade aesthetic and
providing view to the outdoor.
5.2 Limitations of this research
1- All the obtained results about the thermal performance of semitransparent
photovoltaic (STPV) in this research are compared
with only the thermal performance of single clear glass.
2- In this research, daylight performance for the investigated STPV
element is considered as the reduction of artificial lighting load.
Actually, daylight performance couldn’t be investigated only
from the reduction of artificial lighting load aspect but also it is
necessary to investigate the other problems regarding the daylight
performance such as the problem of glare. The daylight
performance for STPV glazing technology could be investigated
in further research.
3- This research doesn’t discuss electricity generation aspect for the
investigated STPV glazing elements. 4- This research has investigated STPV elements with only visible
light transmittance range from 10% to 40%. Further research can
investigate other STPV with higher visible light transmittance
degrees.5.3 Recommendation for future researches
Future researches may be conducted to investigate other aspects,
some of them are mentioned below.
5.3.1 Insulating spacers and frames
As high insulation of spacers and frames of STPV window plays a
major role in minimizing thermal bridging and equalization of pressure,
an extensive investigation is needed for selection of appropriate
components which are contributing in obtaining high performance of
STPV windows. Also the proper selection for these components
contributes in getting long lifetime STPV window ranging almost
between 25-30 years.
5.3.2 Investigating energy performance of semi-transparent
photovoltaic (STPV) windows in double-skin façade
applications
An investigation is required to assess energy performance (in terms
of thermal, visual and electrical performance) of STPV when integrated
in double skin facade application to be able to provide designers with
requirements of obtaining successful efficient STPV integration.
5.3.3 Using bifacial STPV technology
Typical STPV cell is called mono facial cell. It is able to generate
energy due to absorbing light incident on the outer surface of STPV.
However, bifacial STPV cells are able to generate energy not only by
absorbing the light incident on the outer surface but also by absorbing
light incident on the inner surface of STPV. Shading devices and spacing
between cells have a major impact on efficiency of STPV for generating
electricity. In this respect, this case needs to be investigated.
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5.3.4 Using STPV technology in other types of buildings
Mainly, performance assessments of STPV technology are
conducted in case of its integration in office buildings envelope.
However, STPV could be investigated when integrated in other types of
buildings such as residential, industrial or even hotels.
5.3.5 Investigating the Economic aspect of STPV
Economic aspect of STPV technology is required to be investigated
to assess the financial refund of integrating STPV in building envelope in
terms of thermal and visual savings. Also STPV role in generating clean
energy should be taken into account when economic assessment is
conducted.