Science Feature

Using Dhaka's Bright Roof-tops For
Solar Electricity Generation

Md. Humayun Kabir

BANGLADESH, having one of the least per capita in power generation (176 kWh in 2008) in the world has already appeared as a country of power crisis. The maximum power generation of the country reached at 4130 MW in 2008 against the forecast national demand of 5569 MW as per updated power system master plan (PSMP 2006). Although the country's power installation capacity is 5202 MW, on an average 3300-3500 MW can be generated mainly due to aging of the infrastructures, gas shortage and other reasons. Dhaka, the capital of the country with its nearly 14 million populations has recently encountered tremendous power deficiency although electricity is best provided here (sometimes at the cost of the other areas). Power supply in the megacity of Dhaka is quite inadequate (1,200-1,500 MW) compared to its peak demand (~2,000 MW), and therefore, frequent load shedding takes place especially in summer. From the viewpoint of social, economic, political, education, health and other services, the city has received immense importance and the central location has further enhanced its significance to the people. Frequent load shedding of electricity seriously hampers the city life, which has recently created immense dissatisfaction among the city dwellers and this has practically resulted in the collapse of various service and production sectors. The contribution of electricity generation by indigenous gas in Bangladesh is still more than 80%. Due to shortage of gas supply, power generation will be seriously hampered in the near future. The city dwellers have already experienced the problem for the domestic uses.

Realizing the fact that the conventional fuel will be exhausted in the near future, many of the countries round the globe have been making huge investment in the renewable energy sector. It can be worthwhile to take an example of Germany where 25,000 MW of electricity is being generated through wind based power plants. In Germany around 6,500 MW of electricity is being produced from solar photovoltaic systems, which is enough to run a country like Bangladesh. Even the Asian countries like China, India, Taiwan etc. are much ahead in the development of renewable energy technologies.

Bangladesh having a very ideal location on the globe receives global solar radiation (4.2 kWh per square meter per day) at least four times higher than that of Germany. Understanding the effectiveness of solar PV systems, some of NGOs (Grameen Shakti, Rural Services Foundation, Srizony Bangladesh etc,) under the government owned company (Infrastructures Development Company Limited- IDCOL) started solar programs in the rural areas of the country. Till 2009, nearly 450,000 solar home systems have been installed in the rural areas which cover around 20 MW of electricity. But unfortunately no attention has been paid so far to solve Dhaka city's power supply, while the city has extensive bright roof-tops. The immediate measure to supplement power to the existing demand of Dhaka can be power generation through the application of solar PV systems on the bright rooftops. Geophysical factors (absolute location, global horizontal irradiance, temperature, cloud cover, sunshine duration, space availability, bright roof-tops and so on) economic and socio-political (capital investment, technology supports, social acceptability, political commitment, institutional support etc.) and environmental factors (GHG emission reduction, climate protection) are fully supportive to the effective solar PV applications in Dhaka city.

In my study (which has recently been published in the International Journal of Renewable Energy), the bright roof-tops of Dhaka Megacity have been calculated from the high resolution Quickbird satellite image of Dhaka 2006 (with 0.6 meter resolution). In the very conservative calculation it is found that the city offers 10.554 km2 of bright roof-areas. The application of solar PV systems on these bright roof-tops with 75 Wp solar modules

can generate nearly 1,000 MW of electricity preferably through gird connected PV systems. The potential electricity generation can be substantially high (>1,500 MW) with the installation of solar modules with high capacity (i.e., 210 Wp) and efficiency, which would sufficiently meet-up Dhaka city's existing power demand. In the analysis, an extensive area has also been identified as informal settlements (mainly slums). Nearly 96% of these slum communities are provided with grid electricity with obviously poor connection facilities. Practically the slums are reported to have least attention from electricity supply point of view. The roof-tops of these informal settlements can be effectively used for stand-alone PV applications, which are popularly known as solar home systems in the rural areas of the country. Electricity demand for the informal housing is comparatively very low. Therefore, solar home systems can generate nearly 3-5 MW electricity (600-1,000 Watt in each slum cluster). The power demand of the slum-dwellers being remarkably less compared to the high and middle class residential buildings, the electricity demand of the slums can sufficiently be met-up through stand-alone PV installations.

In view of the phenomenal growth of population and gradual increase of electricity demand in Dhaka Megacity, application of solar photovoltaic systems (grid connected or stand-alone on the roof-tops) on the bright roof-tops is essential to supplement to the demand. The renewable energy policy of country has recently been approved and some recent activities by the government can be seen as the political will to promote solar PV applications. The government has declared that any multistoried building (to be built in Dhaka and other big cities in future) will have to have plan for solar based power supplement before the building design gets approved by the city authority. Along with it, 20 kWp solar PV system has been installed in the Prime Minister's office. Despite all these, the government has a lead role to play in the case of initial investment and there is a scope to manage big funds internationally (e.g., through carbon trading). From the perspectives of environmental protection and climate change, application of solar PV systems is pragmatic as the country is a signatory of both the Kyoto Protocol and United Nations Framework Convention on Climate Change (UNFCCC).

(Assistant Professor, Department of Geography and Environment, University of Dhaka & doctoral candidate, Humboldt-University of Berlin, Germany)
Email: mh_kabir@yahoo.com