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Waste Heat Recovery Dynamics: An Analogy of Electricity Generation & Emission Reduction

Climate change is real. it is happening right now. it is the most urgent threat facing our entire species, and we need to work collectively together and procrastinating.

- Leonarda DiCaprio (2016 Oscar Speech)

In a rising global concern of shifting weather pattern, rising sea level to uncontrolled rainfall and risk of catastrophic flooding has instigated worldwide move toward climate change. The increasing global temperature poses significant risk flood, drought, malnutrition impacting living beings and economy as a whole. Last year, extreme weather killed more than 1500 people claimed by the India Meteorological Department is the testimony to the wrath of global warming.

To curb the rising alarm of climate change, one of the essential initiatives can be the circular economy. India being the major developing country, requires immense electricity requirements adding to the CO2 emissions. The one solution to the same can be the Waste Heat Recovery (WHR) system.

"Waste heat energy id the heat that is rejected into the atmosphere from a process at a temperature high enough to permit  the recovery of some fraction of the energy for useful purposes in an economical manner."

Regulation Governing WHR  

As per Section-86 (1)(e)  of Electricity Act 2003, the State Commission should "promote co-generation and generation of electricity from renewable sources of energy by providing suitable measures for connectivity with the grid and sale of electricity to any person and also specify, for purchase of electricity from such sources, a percentage of total consumption of electricity in the area of distribution licensee,"

The Electricity Act has directed states to promote co-generation and provide required ancillary services to these plants. And power generation from waste heat is one of the efficient, cost-effective and cleaner & greener method to generate electricity from heat generated from the manufacturing process. This is an alternative process in which manufacturing companies can full fill their captive electricity requirement. And help to build "Negawatt" (Negative Watt) capacity in the country, which will reduce the use of fossil fuel consumption for power generation and hence reduce the greenhouse gas emission.  

WHR Source and Its Opportunity

Industrial units like Steel, Aluminum and Cement produce a lot of heat energy in their mineral processing units. A substantial amount, i.e. 20% to 50% of this heat energy produced by the industry being wasted as heat into the environment in the form of exhaust gasses. The industrial sector nearly contributes 45-50% of the electricity demand in the country. And if WHR electricity generation has given impulse in the country then their dependency on grid-based power will reduce hence this will save future capacity addition for electricity generation.

As per January-2020 CEA data, India fossil fuel-based generation contributes around 62.43% of total installed capacity. Therefore, there lies an immense opportunity in the reduction of fossil fuel if WHR implemented, enabling the purpose of decrease in import dependency, energy security, and addressing environmental concerns.

WHR Potential and Impact

In this section we will explore the tune of the prospect of WHR potential & impact in electricity generation capacity, reduction in coal & water usage as well emissions reduction per year based on two scenarios and they are: -

  • Scenario-1 (SC-1): If 30% of Industrial waste heat used for WHR based Electricity Generation.
  • Scenario-2 (SC-2): If 50% of Industrial waste heat used for WHR based Electricity Generation.

WHR Electricity Generation Capacity Potential & Impact

WHR Potential in Reduction of Coal and Water Usage Per Year

WHR Potential in CO2, SO2 Plus NO2 Reduction Per Year

Disclaimer: All the above-depicted graph is based on the analysis or information from MNRE, Economic Survey Report and NPTI. The critical assumption taken in the study are: -

  1. Coal usage is considered as 12 Tonne/MW/Day.
  2. Water usage is considered as 98 m3/MW/Day in a coal-based power plant.
  3. CO2 emission is considered around 30 tonnes/MW/Day in a coal-based power plant.
  4. SO2+NO2 emission is considered around 0.68 tonnes/MW/Day in the coal-based power plant.

Summarization and Way Ahead

From the above analysis, we can assume that if we can utilize 30% to 50% of the industrial waste heat, then we can avoid many capacity additions, which will improve the thermal and energy efficiency of industries in the country. There is a massive potential for waste heat capacity utilization available in India. And with increasing industrial growth, this potential is going to increase in the coming years.

Therefore, it is quintessential that all the governing body should come together, ranging from central and state government to policy formulation & implementation bodies to work in a collaborative environment to develop the WHR system. Industries require to work in a close-knitted action plan with the help from the government to tap the future energy source efficiently from Waste Heat Recovery based power generation.