The Technology Context – B101

The sun is one of the future most promising sources of energy because its energy is renewable, clean, and available all over. Presently, solar energy is not utilized extensively because of: the high cost of the procurable solar technologies; the quality of energy acquired from solar; and other factors related to sunshine duration. The future utilization of solar is dependent on current development work to solve problems, reduce costs. The distinctive constituent in what is now designated the "development process" is an all-round acceleration in the rate of change in the life fashion of present and future generations. The process is characterized by the establishment of more activities and novel environments which are leading to new relationships both within the society and with the outside world, many technologies use solar energy. Some classifications of solar technology are active, passive, direct and indirect.



One of Saudi Arabia projects in solar energy was put in action in the mountainous regions of southern and western Saudi Arabia, where there are many road tunnels, which need to be lit during daylight hours to avoid accidents when drivers are suddenly plunged from bright sunlight into darkness. Since 1985, photovoltaic power systems have provided daytime lighting for two of these tunnels: tunnel 1, which is 166 metres long, and tunnel 2, which is 546 metres long. The success of this initiative led the ministry of communication to recommend that daytime lighting be provided to all tunnels over 100 metres in length. However, the local electricity power company found that it was unable to connect 13 of these tunnels because they are located in difficult mountainous terrain beyond the reach of the local electricity grid.
The aim of the project was to use photovoltaic systems to light the 13 problem tunnels. First, the tunnels had to be assessed to make sure that they were appropriate sites for the installation and operation of photovoltaic lighting systems. Then a suitable photovoltaic system had to be designed, which included selecting the best position and equipment to use.
The costs of installing, operating and maintaining photovoltaic systems were estimated to be higher than for diesel systems, so it was decided that a hybrid photovoltaic system would be the best option. One reason for not choosing the diesel system alone is the worldwide need to find alternatives to fossil fuels.
For several decades, photovoltaic cells have provided reliable power to industries and other users in inaccessible locations with adequate sunshine and in areas where demand for electricity is so small that it is met more economically by stand-alone photovoltaic systems than by mains supplies. However, widespread acceptance of photovoltaic systems has been hampered by the high cost of their installation.
In Saudi Arabia, lighting for road tunnels in mountainous areas has become one of the most important applications of photovoltaic energy, but little has been published on this subject. Photovoltaic energy was first used to provide daytime lighting for the mountain road tunnels of Saudi Arabia in 1985, when the king Abdul-Aziz city for science and technology, in collaboration with the ministry of communication, designed and implemented two systems in the southwest of the country near the city of abha. These systems served only two of the region's many tunnels, and the ministry of communication then turned its attention to providing daytime lighting for all the tunnels needing it in both the abha and al-baha city areas. The first step taken by the ministry was to ask the regional utility company to assess the possibility of connecting these tunnels to its grid. While a number of tunnels could be supplied from the grid, a total of 13 in the two areas could not be reached because of the difficult, mountainous terrain. The ministry then went back to the king Abdul-Aziz city for science and technology to ask it to study the potential for using photovoltaic systems to light these tunnels. The king Abdul-Aziz city for science and technology assigned the project to its energy research institute, which had been responsible for the success of the two existing photovoltaic tunnel lighting systems.





The principal aims of the project were to:
• reduce the life-cycle costs of installing, operating and maintaining tunnel lighting systems;
• find suitable sites for tunnel lighting photovoltaic systems;
• reduce the risk of falling rocks or wild animals damaging photovoltaic systems;
• provide system autonomy that is less expensive than installing high-capacity batteries;
• vary the intensity of light provided to the tunnel so that it remains constant throughout the tunnel and between the tunnel and the daylight outside.

The hybrid photovoltaic-diesel system was found to be the most reliable and appropriate system for lighting the 13 tunnels. The photovoltaic systems do not have to be especially large because power is needed only during daylight hours.
The king Abdul-Aziz city for science and technology recommends that diesel generators be positioned between the tunnels so that power can be provided on cloudy days. It suggests that it may be advisable for the ministry of electricity to assume responsibility for the lighting of these 13 tunnels where system costs can be decreased and system reliability increased.