Integration of Photovoltaic Cells with the Architectural Design of Sustainable Public Buildings

: The use of solar energy in the architectural formation has become a step that must be achieved, as the sustainable architectural formation of public buildings will be based on solar energy. Photovoltaic cells are integrated in the roof or walls of the building to provide energy for the building, and this integration is either through the installation of photovoltaic panels on one Building elements or to replace finishing materials for the facade or roof. The research problem is that the rate of building energy consumption has increased with technological progress, and public buildings represent an energy-consuming element.


Introduction
The world is now seriously seeking ways to rationalize energy and the optimal use of resources and reduce their consumption in order to remedy the increasingly dangerous environmental threats that are lurking around the world recently in several forms, such as resource depletion, high rates of pollution and climate change.Technological development represents a fundamental pillar of society's developments.The development of technology in recent decades has resulted in distinct projects aimed at preserving the environment, energy and reducing pollution.One of the most important results of technological development is the emergence of photovoltaic cells and their use in buildings.
It is a good technique to raise the degree of evaluation of green buildings because it reduces the consumption of nonrenewable energy.Photovoltaic systems are no longer placed randomly on the facades of buildings, but are now an integral part of the planning and design stages of most building and construction projects in terms of studying their location or area, the amount of energy produced during the year.Building a sustainable building depends on its energy consumption on renewable energy elements that affect the architectural design and provide comfort for the building users.The research methodology depends on the qualitative approach through the following approaches: A. The inductive approach: identifying the concept of photovoltaic cells, their types, and the factors affecting their work efficiency, identifying the concept of the BIPV system and the importance of its application in sustainable public buildings.B. The analytical approach: through conducting an analytical study of public buildings that used photovoltaic cells that were constructed globally and knowing the design considerations through which photovoltaic cells can be integrated with the design of public buildings in Egypt.C. The case study approach: By studying, the methods of designing public buildings in Egypt and their energy consumption and examining the extent to which these buildings achieve the design standards for sustainable public buildings using the integrated solar cell system with the building envelope.

The concept of photovoltaic cells
It is a technology for generating electrical energy by converting solar radiation into direct electricity.The word photovoltaic consists of two words (photo), which is a word from Greek roots meaning light, and (voltaic) meaning electricity.Thus, photovoltaic means electricity resulting from the exposure of photovoltaic cells to direct light, and an electrical voltage is generated within them that generates a continuous electric current used in many applications, which contributes to reducing fossil fuel consumption and reducing environmental pollution .[1]

Components of a photovoltaic system
When the light falls on the photovoltaic cells, the electron gains excess energy, which pushes the electron to move, leaving a positive void, which leads to an imbalance.The negative upper layer is connected to the positive lower layer of the cell through an external electrical circuit that allows the flow of negative electronics towards the positive layer, as shown in Figure 1.Silicon is considered one of the most semi-conductive materials used in the manufacture of these cells.[2] The photovoltaic cells consist of the following parts:

The photovoltaic panels
The photovoltaic panel is the visible part of the photovoltaic system, which is installed on the roof of the building and generates electrical energy.The most important part of the photovoltaic system is the cell, but the cell cannot be produced on its own.Solar cells are described together in the form of modules, which in turn are gathered in the form of arrays, and the total arrays include photovoltaic panels [3], as shown in Figure 2 below.
The dimensions of the photovoltaic cell vary according to its type and method of manufacture and the dimensions of one cell range from (1 :15) cm in both directions or have dimensions (10 cm * 10 cm) as standard cells.The lowest energy that the photovoltaic cell can produce ranges from (1-2) watts due to the small size of the cell.[4] Figure 2. Components of the photovoltaic panel.

Balance of System (B.O.S);
The supporting system connects the energy from the photovoltaic panels to the loads through its components, as shown in Figure (3), and it consists of the following parts: A. Charger: It is a device that transfers energy from the photovoltaic panels to the battery, measures the percentage of energy in the battery, and stops the charging process when the batteries are full of energy.B. Energy storage: Usually in systems connected to the national grid, the building does not depend entirely on photovoltaic systems, but rather takes its needs from the main network, and in some cases, the systems give their surplus energy to the main network, so it is not necessary to install batteries for this type.In the case of using batteries, they will be used to store energy to save on days when the radiation level is low.C. The electrical transformer: It is known as the power regulator, and its function is at sunrise to connect the panels to the rest of the system and at sunset to separate them from the rest of the parts.D. The supporting structure of the photovoltaic system (stabilization frames): It carries all the photovoltaic panels in the array and is used to determine the angle of inclination of the photovoltaic panels in the photovoltaic row.Some of the supporting structures are movable, which is known as tracking systems for solar radiation, and they move on one or two axis.[5] Figure 3. Components of the solar system.

The relationship of photovoltaic cells to environmental development
The relationship of photovoltaic cells to sustainable development can be known through photovoltaic cells achieving and supporting the sustainable development strategy.Figure 4 shows the exploitation of photovoltaic cells in the Solar Park farm, not only in generating electric power, but also in providing shaded areas for sheep to eat and drink.[6]

The role of photovoltaic cells in preserving natural resources
The cells are based on raw silicon extracted from sand, as shown in Figure 5. Photovoltaic cells are distinguished from other solar energy technologies by being easily dismantled and installed, thus facilitating the process of reformulating the building's outer shell.As well as the possibility of recycling, as the materials that are used in the process of manufacturing cells are (silicon -glass), which are materials that can be reused again, and this is not only beneficial for the environment, but also to reduce the amount of energy required to produce these materials.[7] Figure 5.The production of photovoltaic cells from silicon and the preservation of natural resources.

The role of photovoltaic cells in economic development
Photovoltaic cell fuel is free, as the sun is the only source needed by photovoltaic cells.The relative cost of photovoltaic cells is one of the biggest obstacles to nonproliferation.The high initial cost of producing cells is due to the high price of pure silicon itself, but now, with the progress of scientific research, scientists have been able to exploit crystalline silicon as much as possible while reducing the initial cost of producing photovoltaic cells .
There is a significant increase in the production of photovoltaic systems globally.We find that production doubled from 2007 to 2008 [8], and the percentage is still on the upward trend until now, as shown in Figure 6.

The effect of photovoltaic cells on social development
The use of renewable energies generally and positively affects health rates, as the use of renewable energies helps to reduce carbon emissions.Photovoltaic cells depend mainly on solar energy in their energy production without emissions or pollution.The use of photovoltaic cells helps in the movement of air between the solar panels and the elements of the building, which helps in the process of cooling the building as shown in Figure 7, and thus achieving thermal and psychological comfort for the users of the building.[9] and support for the sustainability system.

The use of photovoltaic cells in urban planning
With urban overcrowding on existing cities and the problems resulting from overcrowding and pollution, the selection of photovoltaic stations sites and their relationship with neighboring areas should be taken into account.New cities and villages in Egypt are among the most appropriate environments for activating photovoltaic cells, as these areas suffer from lack of access to local electricity networks .The use of photovoltaic cells in urban planning as a kind of application of social justice can be summarized in the following points: [10] A. The use of photovoltaic cells to provide projects with the energy, as shown in Figure 8.   C. Exploiting the vacant areas (residents, schools, any buildings that represent shadows on the cells) on the periphery of cities by making solar energy farms, as shown in Figure 10.

Advantages of using a photovoltaic system with sustainable public buildings
The use of photovoltaic cells to produce sustainable public buildings leads to the construction of modern buildings and at the same time environmentally friendly.There are several main advantages achieved namely: [12] A. Increasing energy efficiency, which reduces the amount of energy a building needs in the end.B. Using environmentally friendly building materials that can be redeveloped, renewable and non-toxic.C. The ability of photovoltaic cells to be transparent and the possibility of their diversity as desired.D. Producing electricity to be used in matters of heating and cooling and operating any other loads.E. Use materials that are economically feasible for installation, maintenance, replacement and repair.F. Photovoltaic systems integrated with the building envelope.G.It protects the building from weather fluctuations, provides shade and protects the building from wind and rain.H. Availability of natural lighting due to its different types, including transparent and non-transparent ones that allow sunlight to pass through.I.The photovoltaic cells used in the walls of the building act as sound insulation.
4. Disadvantages of using a photovoltaic system with sustainable public buildings The disadvantages of using photovoltaic cells in public buildings can be summarized in the following points: [13] A. The initial cost is the main drawback due to the high cost of its design, manufacture and materials.B. B-High labor cost due to installation techniques.C. The installation of photovoltaic cells on the building envelope without taking into account the presence of a ventilation space leads to an increase in the temperature D. The production of solar energy is affected by the presence of clouds or air pollution.E. Photovoltaic cells produce continuous energy that needs to be converted into alternating current by means of transformers, which causes energy losses of (4-12) %.

Integration of photovoltaic cells with the outer envelope of sustainable public buildings
Integrated solar energy cells used in construction (BIPV) are photovoltaic materials that are used to replace traditional building materials in some external parts of the building such as roofs, skylights and facades.

Photovoltaic glass
The architects paid great attention to the openings from the aesthetic, plastic and functional point of view.Its physical properties have been developed to suit the climatic conditions surrounding the building.Now there is a more accurate and technical solution, which is the use of photoelectric glass instead of ordinary glass, as in Figure 11, the advantages of photoelectric glass: [14] A. A building material that reduces construction costs, its manufacturing materials are safe and can be reused.Showing an analytical example of using photovoltaic glass to integrate with the outer envelope to form sustainable public buildings, as shown in Table 1.

Table 1. Photovoltaic glass integration with the building envelope.
University of Wisconsin Building:

Cells used:
Vertical photovoltaic curtain walls Analysis of the use of photovoltaic cells in sustainable architectural formation: The outer shell of the building consisting of traditional insulated glass has been replaced by photovoltaic glass made of semi-transparent thin film cells.Photovoltaic glass is a sustainable formation element that achieves natural light during the day, produces the energy needed for industrial lighting at night, and covers the building.

Curtain walls
In general, curtain walls are defined as an integral part of the external formation of the building that is not opaque and allows the internal spaces of the building to connect with the surrounding environment [15].The advantages of curtain walls can be summarized in the following points : A. Beauty of a special kind that expresses the technical development in architecture with ease of installation and implementation .

Photovoltaic breakers
Photovoltaic breakers are considered one of the most sustainable shading elements that can be used in shading facades, as shown in Figure 13, as they can block the sun from the openings and the façade and at the same time produce electricity.[16] Showing an analytical example of using photovoltaic breakers to integrate with the outer envelope to form sustainable public buildings, as shown in Table 2.  Horizontal photovoltaic breakers with a production capacity of 54 kilowatts Analysis of the use of photovoltaic cells in sustainable architectural formation: The photovoltaic solar breakers have been installed in an integrated manner with the elements forming the facade of the building, where the photovoltaic sun breakers work to capture the sun's rays to block them from the building and generate electricity without shadows falling on each other.There is a group of photovoltaic units in the garden area of the southern building

Flat photovoltaic roofs
The roofs are characterized by their permanent exposure to sunlight and the lack of shadows falling on them from the neighboring buildings.They are also of high quality due to the ease of controlling their inclination angle suitable for the location of the sun, as in Figure 14.The inclination angles for flat roofs range from (0:15) degrees, and for inclined roofs between (15:75) degrees.Taking into account the direction and strength of the winds and taking into account the addition of the weight of these units to the structural system of the roofs .[17] Showing an analytical example of using photovoltaic cells on the roof of the building to integrate with the outer envelope to form sustainable public buildings, as shown in Table 3.

Cells used:
Photovoltaic cells at an inclined angle on the roof with a production capacity of 123 kilowatts.Analysis of the use of photovoltaic cells in sustainable architectural formation: Photovoltaic units have been added to the flat roofs of the existing building for shading and protection from sunlight while generating electricity.When renovating the cell locations, the shadows of neighboring buildings were taken into account so as not to affect the cell production.

Inclined photovoltaic roofs
Slanted roofs are a place for installing photovoltaic cells, as it is easy to insert them into the formation of the building block by tilting the roof as in Figure ( 15) or part of it by calculating the appropriate inclination angle that the cells need, as well as the appropriate direction. .[18] Table 4 shows an analytical example of using photovoltaic cells on slanted roofs to integrate with the outer envelope to form sustainable public buildings Eimendingen Building

Cells used:
Photovoltaic cells on the slanted roof with a capacity of 17 kilowatts.

Analysis of the use of photovoltaic cells in sustainable architectural formation:
The building is considered one of the negative projects in the exploitation of energy, as the slanted roof was formed to accommodate an integrated group of photovoltaic cells that are sufficient to produce the building equivalent to its energy consumption that its residents need, so that its consumption of conventional energy equals zero.

PV ceilings
Cell modules can be installed and installed on them easily and at the lowest cost.The ceiling can also be used as ventilation openings that shade the interior spaces from direct sunlight as in Figure 17, in addition to generating electric energy.

Table 5 shows an analytical example of the use of photovoltaic cells on coffered ceilings to integrate with the outer envelope to form sustainable public buildings.
Nieuwland Sports Complex: Figure 17 The use of photovoltaic cells on the coffered ceilings of the Nieuwland Sports Complex.The project Location Holland.Description of the building : German parliament building.

Cells used:
Photovoltaic cells on the pitched roof with a capacity of 46 kW Analysis of the use of photovoltaic cells in sustainable architectural formation: Photovoltaic units have been added to the pitched roofs of the building with an area of 95 square meters, from semitransparent photovoltaic panels that are accumulated above the entrance to the building.It is expected annually to produce 35,000 kilowatt-hours of electricity by solar energy .

Celestial photovoltaic roofs
One of the biggest challenges facing the use of photovoltaic cells in buildings, after the technical and formative development, can be used to cover the atrium and spaces open to the sky, which opened the door wide for architects, as this type combines the advantage of the possibility of introducing natural light into the building as well as a covering system as in Figure 18.
Table 7 shows an analytical example of using photovoltaic cells as a sky roof to integrate with the outer envelope to form sustainable public buildings .
Nieuwland Sports Complex: Photovoltaic cells on the sky roof with a capacity of 9 kilowatts.Analysis of the use of photovoltaic cells in sustainable architectural formation: The building was built in 1929 in the form of a round hall, and in 1997 it was necessary to expand and improve the restaurant, and this is an opportunity to prove and encourage the use of renewable energies on an existing building.Photovoltaic cells were used to cover the expanded hall with a transparency of 45% to introduce natural lighting .

Integration with the building
We explained how photovoltaic cells can be used in many sustainable formations in the external walls or in the ceilings and reach the aesthetic plastic goal as well as the functional goal, which fulfills the achievement of the sustainable architectural formation of public buildings.And creating an integrated plastic system using photovoltaic cells to produce the energy needed by the building so that it becomes able to achieve self-sufficiency in energy production, while not harming the environment and the users of the building  Architect Ron Tommaso formed the building and achieved the integration between the building and photovoltaic cells (BIPV).The formation and integration was carried out with four types of cells installed on the roof, photoelectric glass in the windows, photovoltaic walls, as well as the use of photoelectric breakers.

1.
Studying the concept of photovoltaic cells, their types and systems, knowing the factors that affect the efficiency of their work, and studying the relationship of photovoltaic cells to sustainable development and its impact on the design of sustainable public buildings by supporting photovoltaic cells for the axes of sustainable development, and finding that photovoltaic cells are the best types of renewable energy methods used in Egypt 2. Proposing design criteria that are taken into account when designing sustainable public buildings that use photovoltaic cells to obtain the energy consumed by the building by relying on solar energy instead of non-renewable energies, thus preserving the environment and its resources.

3.
Concluding that the use of photovoltaic cells in sustainable public buildings and integrating them with the outer envelope of the building through simulation work to design models for sustainable public buildings.Using computerized representation programs Ecotect and calculating the amount of energy needed by the building throughout the year and the ability of photovoltaic cells to provide this energy and achieve the economic feasibility of the use of photovoltaic cells and the application of the BIPV system in the building affects the architectural formation of the building.

Discussion
Computer simulation programs, or what is called computerized representation, are used during the design phase, as they work simultaneously with the design process, which provides an opportunity to find solutions and alternatives to expected problems before they occur.
Computer Simulation is defined as a computer program or a network of computers that tries to simulate a computer model of one of the buildings to be designed and know the capabilities and operating systems of the building and the amount of energy consumed after building the building.Computerized representation is a system that leads technology to create a virtual model, implement it, test its performance, and analyze its results.It is not possible to neglect or ignore the fact that architecture is one of the most important engineering fields affected by the computer.He touched on one of the most important programs for representation, which is Ecotect and learned about the most important simulation processes that it offers.Especially the process of analyzing solar radiation to generate electric energy in public buildings through the use of photovoltaic systems and quantitative analysis of various design alternatives for photovoltaic cells integrated with the public building.By studying the steps followed in the study to reach the final results by means of the Ecotect program and in the end, the performance of the photovoltaic systems integrated with the public building is evaluated.

Conclusion
After studying the concepts and axes of sustainable development from environmental economic and social development, the study dealt with the support of photovoltaic cells for the sustainability strategy and the possibility of integrating photovoltaic cells with the architectural formation of sustainable public buildings and finally studying the impact of using photovoltaic cells on sustainable public buildings in Egypt.The following results address the most important findings of the research study in the following points.

1-
The use of photovoltaic cells in the architectural formation of sustainable public buildings has formative foundations and is not just an addition to technology or a device for the production of renewable energy only.

2-
The use of photovoltaic cells in sustainable architectural formation 3-Computerized representation, which is used in studying the dynamic behavior of objects or systems, which enables measurement or prediction of the operational function of an entire system.

4-Ecotect program is defined as an integrated
environmental analytical tool that allows simulating the performance of buildings from the initial stages of the design idea.The program provides analyzes and tests in terms of energy analysis, thermal analysis, lighting and shade analysis, and acoustics analysis.

Recommendations
First: Recommendations for government decision makers 1-Enact laws and regulations for the use of photovoltaic cells integrated with sustainable public buildings by emphasizing the need to benefit from solar energy.2-Urging and encouraging citizens and institutions to utilize solar energy in buildings and adopt the concept of integrated cells with the buildings to be constructed.3-Developing a database with the concerned authorities to provide updated data on weather, climate and other data needed by researchers for the cities of Egypt.Second: Recommendations for architects 1-Exploiting the southern facades with their elements of walls, openings and breakers to be energy production elements through photovoltaic cells integrated with them.2-Adopting computerized representation programs as a basis for designing an energetically integrated building of photovoltaic cells to obtain the highest results from solar radiation through the building's shape, orientation, and study of its surrounding environment.3-Develop a detailed and comprehensive reference for design standards and requirements for photovoltaic cells integrated with public buildings.Third: Special recommendations for citizens 1-Holding meetings and workshops for citizens on the importance of renewable and non-renewable energy sources and the rationalization of their use.2-Educating citizens about the importance of using solar energy through visual, audio and written media, in addition to electronic social media.3-Holding courses to educate citizens on how to calculate electrical loads to calculate the area of photovoltaic systems to be installed and to identify the necessary equipment and devices.Fourth: Special recommendations for researchers and those interested in the field of solar energy 1-Providing scientific solutions and recommendations to decision makers according to scientific, experimental research foundations, which will contribute to the development of appropriate regulations and legislation to regulate the applications and investments of renewable energies.2-Enhancing joint cooperation between researchers and research institutions locally and globally, and increasing the interdependence between scientific and applied research and development with industrial sectors related to solar energy exploitation issues through photovoltaic systems integrated with the building envelope.3-Implementing a set of awareness programs for all concerned parties about the most important programs for the exploitation of solar energy through photovoltaic units integrated with the building by presenting the results and recommendations of their studies.Position figures and tables at the tops and bottoms of columns.Avoid placing them in the middle of columns.Large figures and tables may span across both columns.Figure captions should be centered below the figures; table captions should be centered above.Avoid placing figures and tables before their first mention in the text.Use the abbreviation "Fig.1," even at the beginning of a sentence.
Figure axis labels are often a source of confusion.Use words rather than symbols.
For example, write "Magnetization," or "Magnetization (M)" not just "M."Put units in parentheses.Do not label axes only with units.In the example, write "Magnetization (A/m)" or "Magnetization (A ⋅ m 1 )."Do not label axes with a ratio of quantities and units.

Figure 1 .
Figure 1.How photovoltaic cells produce electric current.

Figure 6 .
Figure 6.The continuous increase in the use of photovoltaic cells.2.3.3.The effect of photovoltaic cells on social development

Figure 7 .
Figure 7. Permeation of air through photovoltaic cells and support for the sustainability system.

Figure 8 .
Figure 8. Photovoltaic power plants in Austin, Texas B. Contribute to the sustainability of global civilization by providing clean energy, as shown in Figure 9.

Figure 9 .
Figure 9.A central photovoltaic station connected to the network.
B. Provides protection from direct sunlight.C. It generates clean electric energy with an average of 45 to 60 watts/m2.D. Achieving transparency in different degrees and achieving plastic aesthetics.E. It provides many architectural formations, as it is available in different dimensions and sizes.

Figure 11 .
Figure 11.The effect of the efficiency of photovoltaic cells on the degree of transparency.

Figure 12 .
Figure 12.The use of photovoltaic glass in the classrooms of the University of Wisconsin.The project Location University of Wisconsin -USA Description of the building : Study rooms and research laboratories .
B. It is more resistant to weathering, rust and water permeability .C. It can be closed or open in order to facilitate control of the internal air and the amount of light .D. No large loads are added to the structural structure

Figure 13 .
Figure 13.The use of photoelectric breakers with an angle of inclination at the Research Center at New York University The project Location New York University -USA Description of the building : Scientific and educational research center.Cells used:Horizontal photovoltaic breakers with a production capacity of 54 kilowatts Analysis of the use of photovoltaic cells in sustainable architectural formation:

Figure 14 .
Figure 14.The use of photovoltaic cells at an angle of inclination on the roof of the German parliament The project Location Germany.Description of the building : German parliament building.

Figure 16 .
Figure 16.The use of photovoltaic cells on the sloping roof of a residential building The project Location Germany Description of the building : Residential Building.

Figure 18 .
Figure 18.The use of photovoltaic cells to cover a skylight at Ambiente Restaurant The project Location Germany Description of the building : restaurant Cells used: Photovoltaic cells on the sky roof with a capacity of 9 kilowatts.Analysis of the use of photovoltaic cells in sustainable architectural formation:

Figure 19 .
Figure 19.The use of photovoltaic cells in the external walls and ceilings of the US mission headquarters..The project Location Geneva-Switzerland.Description of the building : Headquarters of the US diplomatic mission.Cells used: Photovoltaic cells for walls and ceilings.Analysis of the use of photovoltaic cells in sustainable architectural formation:

Table 2 .
The use of photovoltaic glass as solar refractors.
New York University Research Center Building:

Table 3 .
The use of photovoltaic glass on flat roofs.

Table 8
shows an analytical example of using photovoltaic cells to integrate with the outer envelope to form sustainable public buildings.