It is envisioned that by 2050, the current world population of 7.6 billion is about to reach 9.8 billion (United Nations, 2017). At the same time, 66 per cent of the world’s population is projected to be urban by 2050 as opposed to the current 54 per cent residing in urban areas (United Nations, 2014).With rapid urbanisation, the macro-economic forces of development would impact businesses, economies, societies, cultures and personal lives of people worldwide. This would translate into an explosion of consumption, accelerate usage of energy and would result in severe consequences on the environment, health and natural resources, especially in urban zones.
For the first time since Independence, India recorded a higher decadal increase in population in urban areas (91 million) as compared to that in rural areas (90 million) in 2011. Between 1951 and 2011, urban population increased from 17.3 per cent to 31.2 per cent (Census of India, 2011).It is further expected to increase to about 50 per cent of the total Indian population by 2025 (United Nations, 2014). It is reported that in general approximately 2 million people are shifting from rural to urban areas on an annual basis while about 22 million people have moved from rural to urban areas since 2001 (Gautam, 2012). This is putting tremendous stress on infrastructure and resources available in the existing cities. Rapid and unplanned urban growth can be a threat to sustainable development if the necessary infrastructure is not developed on time.
Urbanisation is essentially fuelled by the buildings and construction industry. The building sector world over is regarded as a major contributor to global greenhouse gas emissions with a share up to 30 per cent while consuming 40 per cent of all energy (United Nations Environment Programme, 2009). Given the massive growth of new construction in developing economies, coupled with the inefficiencies of existing buildings, the consumption of energy and emission of greenhouse gas from buildings are expected to double in the not so distant future.
A possible policy solution to the problem could be the promotion of smart cities that focus on sustainability aspects in terms of energy requirements and environment protection. The Smart Cities Mission in India, for example, envisages promotion of eco-balance as one of the features of comprehensive development (Smart Cities Mission, 2017). Since buildings have a relatively long lifespan, actions taken now will continue to affect their energy requirements and environment over a considerable period of time. Creation of environmentally benign buildings would thus impact many aspects of sustainability for the next 50-100 years. Therefore, a long term perspective should be adhered to while planning smart cities. The requirements for long term sustainability would include enhanced energy efficiency, captive energy generation and increased use of renewable sources and bio waste.
Smart Cities Mission launched by the Government of India is widely considered to be a bold initiative having an objective to promote cities that provide core infrastructure and give a decent quality of life to its citizens, a clean and sustainable environment with application of smart solutions. The innovative solutions proposed under the Smart Cities Mission include—■ e-governance and citizen services, ■ energy management, ■ water management, ■ urban mobility, ■ waste management, and ■ incubation/trade facilities and skill development centre. The sustainability criteria have been included in the Smart Cities Mission through solutions under energy management and waste management.
Energy efficiency is an important feature of any sustainable building. The other aspects associated with sustainable buildings involve economising materials and resources used while ensuring energy efficiency during building construction. Buildings account for one-sixth of the world’s fresh water withdrawals, one-quarter of its wood harvest, and two-fifths of its material and energy flows. Building construction may therefore be considered as one amongst the industries having highest environment impact. At the same time it has significant scope for environmental impact reduction through selection of building materials.
When planning for sustainable buildings, prevailing weather conditions are crucial to the whole design. As an indicator to the climate change, extreme weather events are on the rise (Huber and Gulledge, 2011).A significantly high frequency has been recorded in the persistence and spatial coverage of both types of extreme temperature events (heat and cold waves) during the period between 1991 and 2000 (Pai, et al., 2004). Research indicates that there is a rising trend in the discomfort indices during the last 10 days of April to June over most of the Indian cities (Srivastava, et al., 2007). Increasing levels of urban densification in major cities are also leading to increase in average temperatures (Dhorde, et al., 2009). It would not be difficult to forecast enhanced uses of energy with increasing temperature and discomfort levels. Given such a scenario, in the Indian context, the major strategy will have to reduce energy requirement of the buildings on one hand, and enhance the generation and use of renewable energy on the other.
The reduction in energy requirement of a building can be achieved by adopting certain principles of building design (Chang, 1967). Accordingly, the design aspects include—■ orienting a building to minimise the wall area facing east or west; ■clustering buildings to provide some degree of self-shading (as is the case in many traditional communities in hot climates); ■ using high-reflectivity building materials; ■ increasing insulation; ■ providing fixed or adjustable shading; ■ using selective glazing on windows with a low solar heat gain and a high daylight transmission factor and avoiding excessive window area (particularly on east- and west-facing walls); and ■ utilising thermal mass to minimise daytime interior temperature peaks (Intergovernmental Panel on Climate Change, 2007). Power utilisation in buildings can also be reduced by deploying energy efficient appliances and gadgets that operate on renewable energy. According to UNEP, with proven and commercially available technologies, the energy consumption in both new and existing buildings can be reduced by an estimated 30 to 80 per cent (United Nations Environment Programme, 2009).
The other approach to reduce consumption of grid power is to promote community specific generation and use of renewable energy. Solar cities have been conceived in India with the aim to reduce projected demand for conventional energy by 10 per cent through energy supply from renewable sources and use of energy efficient measures (Tripathi, 2014). To this end, provisions could be made for converting solar energy to electrical energy by using SPV, solar thermal, thermoelectric materials and flexible photovoltaics including dye sensitised solar cells.
A crucial feature of renewable energy is that it is generated from intermittent sources such as sunlight and wind. Therefore, the energy generated from renewable sources needs to be stored for use at opportune time and place. Lead acid batteries, Li-ion batteries and redox flow batteries are suitable options for storing renewable energy. The increased use of renewable energy would therefore enhance the requirement for energy storage systems.
Another essential requirement for sustainable buildings is clean and healthy surroundings. This requirement can be changed into an opportunity by converting bio waste and municipal solid waste (MSW) generated in the building into energy for captive use. Anaerobic digestion of municipal solid waste (MSW) and source separated organics (bio waste) are amongst the most innovative technological developments in waste management. The technology is not only useful for production of renewable energy, but also for reduction of odour while requiring minimal surface area (De Baere and Mattheeuws, 2012).
One of the eight key messages communicated in the UNEP report suggests that governments should take lead by prioritising the building sector in the national climate change strategies. A mission mode programme is needed to reduce energy requirement of buildings while enhancing captive generation and use of renewable energy for making buildings energy neutral and sustainable.