The harsh reality of climate change is our Earth moving from being hot, hotter to hottest. Demand for cooling is rapidly increasing and as incomes and standards of living increase, people want to buy and use air conditioners to keep cool for health, well-being, and economic productivity.
So, why is this topic of global energy cooling demand of utmost importance? There are only two ways to achieve our temperature goals:
i) Reduce and ii) Remove Green House Gases (GHG) that deplete the protective ozone layer and allows for harmful solar radiations to impact our health. One of the biggest opportunities in reducing GHG emissions is by optimizing the energy demand for space cooling/air conditioners (ACs). Today, the electricity required to power ACs give rise to huge carbon emissions (mainly from fossil fuels like coal and gas) and leakage of refrigerants from ACs traps heat leading to extreme hot conditions.
Here are some facts to know:
- Of the 2.8 billion people living in the hottest parts of the world, only 8% currently possess ACs, compared to 90% ownership in the United States and Japan.
- Global sales of ACs have been growing steadily: since 1990, annual sales of ACs more than tripled to 135 million units. There are now about 2 billion ACs in use that consumes over 2000 terawatt hours (TWh) of electricity every year, which is two and a half times the total electricity usage of Africa.
- 10 ACs to be sold every second for the next 30 years.
- The highest demand in energy use for space cooling by 2050 comes from the emerging economies, with just three countries – India, China, and Indonesia contributing half of global cooling energy demand growth.
The most practical and effective methods of residential cooling are ‘Active’ cooling using household fans, packaged air-conditioners (ACs), split ACs, large chillers that need electricity from the power grid to function.
‘Passive’ cooling requires no electricity and use sustainable methods to cool. Learning from both ancient as well as modern ideas, passive cooling techniques are increasing being used to keep buildings cool. One such example is ‘cool roofs’ method that coats roofs with materials and products that strongly reflects sunlight and cools itself by efficiently emitting heat and resulting in the roof literally staying cooler thereby reducing amount of heat conducted to the building below.
In North India where temperatures become scorching in summer, in shaded courtyards, traditional Indian stepwells lead to pools of collected water that absorbs heat and circulates fresh cool air. Evaporative cooling that provides an air flow together with circulation of dripping water such as ‘bee-hive’ systems using terracotta pots have been cost effective as well as requiring low maintenance.
Wind-catcher designs: Another example is in Iran (also known as a ‘windcatcher’ city) that uses an ancient Persian method to keep houses cool. Towers on top of flat-roofed buildings catch the breeze and channels down air, with the cooler and more dense air flowing through the interiors of the building.
Active Cooling using District Cooling Systems (DCS):
The latest technologies that will become the backbone of cities transition to sustainable cooling and reduce reliance on power grids and usage of more renewable power (such as solar and wind) are DCS (District Cooling Systems). A DCS can serve a wide variety of loads for commercial offices, hotels, residential, industry units, data centers, cold chain, sports arenas, malls, schools, institutional buildings, and hospitals. DCS distributes (supplies and collects back) cooling energy in the form of chilled water from a central district cooling plant to multiple buildings through a distribution network of insulated, underground pipes for space cooling.
India is taking inspiration from leading district energy cities and countries such as Dubai where 40% of all buildings (residential and commercial) will be connected to DCS by 2030 and Denmark where almost all buildings in large cities are connected to district heating systems and customers enjoy some of the lowest heat prices in Europe showing it is possible and affordable but requires strong government support to reach such levels. Look at the chart below that shows how other countries are leveraging district cooling systems (DCS) to keep their cities cool.
With India’s water scarcity, where is the water for running the cooling systems?
India is the 13th most water-stressed country globally with several of its cities, including the industrial hub Chennai, are at “extreme risk” of experiencing water shortages. Water for cooling can be sourced in multiple ways:
a) Municipal or borewell water, which is a precious commodity that could rather be used for drinking purposes
b) Ground water or treated sewage water recycled from sewage treatment plants
c) Sea water or brackish water treated using reverse osmosis (RO), forward osmosis (FO) or other technologies
Over 90% of industrial wastewater generated every day across India is untreated when discharged and flows into rivers (As an example Ganga river alone receives around 1.3 billion liters of raw sewage and 250 million liters of industrial effluents daily). There are tremendous opportunities to re-use wastewater and is a win-win for tackling extreme heat conditions with cooling systems that can use treated wastewater.
India (and South Asia in general) is already seeing the dangers of extreme heat waves among other weather-related calamities and rapid migration to cities is expected in the coming decade. It is of utmost importance to improve energy efficiency in our country by providing sustainable energy/cooling and investing in the right infrastructure for smart cities to function. As we learn from developed countries : Public sector, private sector, city, and state administrations to collaborate with technology companies, financial institutions, and industries (such as real estate and utilities) to bring in change and make life in cities bearable for all.