SOLAR POWER IN BUILDING DESIGN, THE CASE OF NTC TOWER IN THE SUDAN

Zero energy buildings is one of the methodologies to achieve green Architecture goal which combine energy efficiency and renewable energy generation to consume as much energy as can be produced onsite. The aim of this study is to describe current approaches to integrate solar photovoltaic power systems in architecture to achieve energy efficiency in buildings taking the National Telecommunications Corporation tower, (NTC Tower), in Sudan as an example of such buildings, which integrates solar cells in its envelope. In this research, we calculate the energy consumption in this tower and analyze the input of the integrated solar cells by presenting a simulation detailed model of the building. This allows us to examine the details of its energy performance. Based on this analysis the paper sets recommendations for enhancing energy efficiency building by integrating solar cells in buildings. Keyword Energy Consumption1, Solar Power2, Renewable Energy3, photovoltaic systems4

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The appl thermal t exterior w 3.1 Solar ene of solar h but also meet the such as t protectio exposed tube cann the flat p has highe [4]. Solar located in ts should play right from the olar energy. [1] d buildings. er, discusses t xplores a new ituation of the and evaluate e ings, have ren l remain fit a n amounts to m n two-thirds o y, the use of nding of solar ergy and build f the local en nd make solar he aims of th n Sudan, and he research app ing the Autod a building fo as it is. Then ied several sc hich has a bet APPLICATIO lication of sol technology, so walls and som Solar Therma ergy is mainly hot water syst to improve th needs of the the difficult in n and draugh to the outdoo not meet the n plate solar col er adaptability r collector sy n the basemen large amount of water, water tank can be a single one, double or even a multi-tank. If the tank capacity is increased, the installation area will corresponds to meet the hot water needs. Hot water is not only used in bathrooms, but also used for heating and cleaning kitchen utensils. The water quality should be clean to meet the drinking water standards. Integrating solar collector with the roofs, balcony rails of the south façade, bay windows and walls, can make the appearance of buildings be overall unified, and have rich hierarchies [5]. When installed on the sloping roof, the solar collector can be embedded in the roof like a sunroof or flat out on the roof, integrating with the construction to increase the building beauty. When installed on the flat roof, the flat-plate solar collector can act as roof covering or insulation layer, not only conforms to the residential modeling requirements, but also avoids the repeated investment and reduce the cost.
In addition, the flat-plate solar collector can be combined with balconies, bay windows, outside walls of buildings, to maximize the use of solar energy and provide new ways and means to the residential façade design, and achieve the aim of multi-purpose as well.
3.2 Solar Photovoltaic Technology Solar photovoltaic technology applying in buildings is mainly used for photovoltaic conversion and lighting. Building Integrated Photovoltaic (BIPV) is a new concept for the application of solar power. In short, it is installing the solar photovoltaic phalanx on the surface of the maintenance structure of the building to provide electricity [6]. Photovoltaic arrays do not take up additional floor space when integrate with the construction. It is the best installation way of photovoltaic generation system, thus attracting much attention. BIPV can be divided into two categories according to the forms that photovoltaic array integrated with the buildings [7]. One is the combination of photovoltaic array with building, installing the PV array on the building, and the building plays a supportive role as a photovoltaic carrier. The other is the integration of photovoltaic array with building, PV modules appears as a building material, and the photovoltaic array becomes the integral part of the construction. Such as photoelectric tile roof, photoelectric curtain wall and photoelectric lighting roof, etc.

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Solar Optical Technology The main use of the solar optical technology in buildings is for lighting, natural light can enter into the function rooms through the light guide tube, thus improve the indoor daylighting situation, such as underground garage, equipment room and storage room. Because utilization of solar optical system is also subjected to the impact of the climate, this technology is suitable for the regions that have abundant natural light and less cloudy sky [8]. The light guide tube is mainly composed of three parts: a light collector for collecting the daylight; tubing portion for transmitting light, and the light exit portion for controlling the distribution of the light in the room. Using the light guide tube on the roof must ensure that there have no obstructions, and well water treatment to avoid leaking during the installation. Moreover, as the instability of the natural light, the light guild tubes must in combination with the adjustable artificial light, to be an effective supplement when the daylight is insufficient.

CASE STUDY
The case study shown below depicts the efforts done to create of energy-efficient buildings integrated solar cells with its construction. The short project summary describes key features and lessons learned from the project. The NTC Tower is a skyscraper in Khartoum, The Sudan. The 29-story building finished in 2009. Its construction began in 2005. [2] The contractor was the Turkish company AINA International. The total area of the site is 5000 square meters and the built up area of the ground floor is 3000 square meters. The typical floor area is 980 square meters and the total built up area is 32,000 square meters. The total number of floors is 29 floors with a total height of 110 meters plus a telecommunication antenna, which is 30 meters high.   Where: Ed: Average daily electricity production from the given system (kWh) Em: Average monthly electricity production from the given system (kWh) Hd: Average daily sum of global irradiation per square meter received by the modules of the given system (kWh/m 2 ) Hm: Average monthly sum of global irradiation per square meter received by the modules of the given system (kWh/m 2 ) The following table shows the economic analysis of the system:   Figure (6). The construction is done step by step, taking into account all the openings, internal divisions and materials. This affects the energy calculations at the start of the simulation. 2. The following are the basic steps that have been followed in the Autodesk program to prepare the model for the NTC tower: 3. Open a new file: An empty file has been created and named (Case Study) 4. Processing the project browser list: which enables the project to browse and find all the required drawings in the project and it was as follows: (25 Floor Plans, one section, four elevations, three-dimensional drawings) 5. Build the model according to the studied material specifications as it is on the site, by adding the floors, walls and openings, and start with the ground floor only as it appears in Figure (6). After the ground floor model is completed with all its details, the floor will be copied because it is typical floor with some slight changes.   7. Then the simulation process started and a detailed analysis report is given. See Figure 9 and Figure 10. for summary of the report. 8. The simulation report shows that the highest is the cooling cost second came the lighting cost and this is clear in the peak electric demand chart where the highest demand of electricity is within summer session (May to October). Then several scenarios has been tested and the paper will recommend the best solution as follows.

RECOMMENDATIONS
To achieve an optimal energy model for the selected case study The NTC Tower in The Sudan, the paper applied the Generated and Test Technique, where we make our ideas under test to perform them using the Autodesk Ecotect Analysis software. Several ideas were generated and tested using Ecotect to evaluate its effect on the model energy performance, as follows: 1. Solar Panel efficient: Fig. 11: Using multi-crystalline solar cells, which is 11% more efficient than the used ones will increase the electricity generated from the current PVC systems by 11%.
2. Building envelop must be carefully designed to avoid thermal gain or thermal bridges. Fig. 12: Rotating the solar cells used in the south western side of the tower 10°, will increase the electricity generated from the current PVC systems by 5%.
3. Using the same suggested envelop in the eastern side will increase the electricity generated from the PVC systems by 15%. a. Roof integration, using more solar cells from the type multicrystalline solar cells will increase 9% of the electricity generated by the solar system. In an area equal to 550 square, meter available in the Roof.

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Solar energy and building integration technology also requires the integration of construction process and technology, in addition to the conventional construction, there also need to conduct the complex construction of waterway and circuit and to complete the installation and debugging tasks of solar equipment's .

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Economic Analysisand cost benefit is required to compare the advantages and the cost of using PVC system integrated in the building construction. 6.
Off-grid or Grid connected. Even if an architect creates a zero energy building by producing the amount of electricity needed for the tower with on-site solar energy generation, it is still not recommended to design an off-grid building for; the output of the PV systems is unstable because it varies depending on the weather. Connecting with the grid makes it possible to constantly, supply power to consumers. Installed systems other than HVAC systems can influence a building's energy performance in two different ways: through their own energy demand and through their production of waste heat which can result in increased cooling loads. Lighting considered the highest in consuming electricity among all other installed systems or other equipment's, the second after HVAC. Using natural lighting is recommended and lighting sensors to maintain the lighting level in spaces within an acceptable level.
8. HVAC systems used in the building for cooling in hot climate or heating in cold weather is consuming the largest part of energy used in the buildings. See Figure 10. 9. HVAC should use energy efficient machines and it should be maintained periodically. In addition, the designer should use passive cooling strategies to minimize the need of mechanical cooling or heating. In addition to the use of smart sensor and thermostat to obtain the thermal comfort needed inside the spaces.
10. Comparative studies show that large differences can exist when using different simulations programs, even for a very simple passive solar building.
5. CONCLUSIONS Solar energy and office building integration technology has broad application prospects, using simulation program will play a significant role in applying the use of solar energy in an efficient way, in the case shown for NTC tower, the researchers were able to increase the percentage of energy consumption covered by the solar energy by 40%, as shown in Figure.14. Finding an accurate and efficient way to model and simulate the building to evaluate the energy consumption is of upmost importance.Many future areas can be taken with this model. Use of real data should be used to refine the assumptions made and parameter calculations performed.