Quantification of global waste heat and its environmental effects

Abstract

Waste heat is a major source of recoverable loss in societal energy use, offering significant potential for reduction in greenhouse gas emissions. A number of studies have been carried out to determine the size of the available resource but have been limited in scope or confined to the status quo. This work reports a method to quantify future global waste heat emissions from the Power Generation, Industry, Transport, and Buildings sectors, and investigates their environmental effects. Four projected energy landscapes (World Energy Outlook 2016: 1. Current Policies; 2. New Policies; 3. 450-scenario. 4. 100% renewable energy penetration) were simulated to assess the amount of waste heat produced in different sub-sectors in the year 2030. The impact of CO2 radiative forcing and various technological shifts are reported. Total waste heat emissions are found to account for 23.0–53.0% of global input energy depending on year and scenario, with a range of theoretical and economic recovery potentials of 6–12% and 6–9% respectively. Further insight is gained into the waste heat landscape through analysis of temperature and sectoral distributions, and identification of hotspots for targeted waste heat recovery. When considering emissions from 2014 to 2030, the integrated radiative forcing of CO2 is found to be 13 times greater than that of waste heat, primarily attributable to the former’s cumulative nature. Full recovery of the theoretical potential is found to lead to a 10–12% reduction in the combined forcing of CO2 and waste heat over this period, mainly due to a reduction in CO2 emissions. Under a conservative carbon tax, this reduction is estimated to offer potential economic savings of $20-77bn/year. A 10% increase in the penetration of solar/wind/tidal hydroelectric power and electric vehicles are found to decrease global waste heat losses in liquid and gaseous streams by 5% and 0.7–2.0%, respectively; retrofitting of Carbon Capture and Storage to power plants decreases CO2 radiative forcing, outweighing the increase in thermal radiative forcing from additional waste heat streams.