Resolving ‘dumsor’ with the use of natural light
The intensity of the power outages in Ghana seems to have dwindled in recent times but it is without doubt that a lasting solution is not in the offing. The announcement of routine maintenance of any of the power plants in the country raises concern of imminent ‘dumsor’.
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It has, therefore, become apparent that energy conservation and a diversification of Ghana’s energy sources is non-negotiable.
It calls into question Ghana’s inability to take full advantage of the sun in the provision of illumination and electrical energy.There is a heavy dependence on electric energy from hydro and thermal sources, and electric light is used regardless of weather condition. Our desire for glass curtain walls and air conditioning makes it practically impossible for work to be carried out in most offices (without generators) during dumsor because of poor ventilation and lighting.
It is very common to see mid-rise buildings with glass facades in the capital where blinds have been drawn to exclude daylight because architectural lighting was not considered in the design phase.The time has come for buildings in our cities to consider the local climate in the design process.
Sources of illumination
Daylight, sunlight and reflected light which make up natural light presents reliable sources of illumination and electrical energy.Fortunately, guidelines and precepts have been established to aid in making the best use of natural light in buildings. The most important factor in utilising natural light is the orientation of a building. Natural light can be difficult to control and may cause excessive heat and uncomfortable glare whenever care is not taken in establishing the orientation of a building.
East and West facades experience the greatest exposure to the sun and makes it more difficult to shade direct sunlight, therefore, avoiding orienting the long axis of a building in the north-south is advisable. The long axis running east-west is preferable since the solar impact on the northern side of buildings is usually minimal and does not require shading. For instance, having a library in a residential facility oriented toward the north will ensure even light source and prevent any damage to books by sunrays.
Fenestration and shading devices are equally essential because sun rays arrive at a building envelope and is transmitted through a window.
The arrangement, proportioning and design of windows in the building contributes to the quality and quantity of illumination. Windows on the north and south facades are easier to shade with horizontal devices usually overhangs. Windows and openings facing east and west are best shaded with adjustable devices which can respond to the changes in the sun angle (sun changes bearing about 15 degrees per hour).
Natural light distribution
An important aspect which is often ignored is the building shape and massing (organisation of building over volume). The quality of natural light distribution within a building is dependent on the massing. Narrow building forms with exterior openings are easier to illuminate with natural light than wider forms. Narrow buildings in alphabetical shapes such as L,E ,U and T are able to maximise perimeter access to natural light. The use of electric light is necessary but must be used sparingly and only to aid in illuminating spaces where the effect of natural light is minimal. Photo sensors can be used to detect daylight levels that will inform the output level of electric lighting needed to create the desired illumination within a space. Light controlling system may also make use of multilevel switching such that lamps in a single light fixture can be switched on and off independently of each other. This allows for various steps between full output and zero illumination to avoid over illuminating a space.
The provision of illumination by the sun does not only result in reduction in use of electric lighting but reduces pollution associated with electric light. The interception of the intense rays of the sun into building interiors drastically reduces the air-conditioning cooling load.Generation of electricity from sunlight has a huge potential in addressing the energy needs of residential properties and offices in Ghana.Luckily, pricing for solar photovoltaics installations is becoming reasonable.Most built-environment professionals are knowledgeable about the measures of optimising the use of natural light in building designs and construction, yet their services are not patronised by developers because of the erroneous impression that they charge an arm and a leg for their services.
Life cycle costing should ,therefore, be the guide for citizens who are yet to develop residential, commercial and educational facilities.Cutting corners will only result in perpetual occurrences of building defects which come with huge repair costs.Citizens must patronise professionals who will make use of their vast experience and thorough deliberation in giving them energy efficient designs that take full advantage of the sun. Hopefully, dumsor can be laid to rest soon and there will be less reliance on the national grid.