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An investigation of the operational energy and carbon savings of changing air-conditioning set points in Indian offices to provide adaptive thermal comfort temperatures locally (2023)
Authors: Rajan Rawal, Tarjani Mehta, Yash Shukla, Susan Roaf
Abstract:

Thermally comfortable and energy-efficient buildings will play a pivotal role in radically reducing operational energy use and carbon emissions from the built environment. The emphasis in emission reduction strategies is now moving away from reliance on the marginal energy benefits of slightly more energy efficient machines for meeting emission reduction targets towards the provision of energy-sufficient buildings that not only protect occupants from the predicted more extreme climates of the future while also resulting in radical emission reductions. Buildings are responsible to nearly 40% of global Greenhouse Gas (GHG) emissions and despite huge investment in the sector over recent decades GHG emissions continue to rise alarmingly. In the tropical countries of the global south, the recent trend has been towards designing primarily cooling-dominated workspaces in offices. This paper presents an investigation into the importance of, and potential extent of emissions savings that can result from utilizing favourable outdoor conditions in building operations in India. It then analyses the operational energy and carbon saving potentials resulting from moving HVAC operation away from using narrow set-point temperatures to those derived from the adaptive thermal comfort theory. The study used integrated modelling approaches involving building performance analysis tools to characterize the performance of an office building located in an urban hot and dry climate. The study provides a comparative analysis of several scenarios interrogated to optimise the provision of low carbon, indoor thermal comfort for occupants. An initial deep dive into the climate analysis was followed by calculating the uncomfortable hours, operational energy consumption and resulting carbon emissions based on the ASHRAE 55 PMV model, ASHRAE 55 adaptive model, India Model for Adaptive Comfort (IMAC) AC model, IMAC Mixed mode operation model, IMAC Natural Ventilation Operational Mode. The study also investigated the impact of elevated air speeds on achieving thermal comfort and demonstrated the savings. The building's Annual Energy Consumption was reduced by between 11% to 66% compared to the reference model specified as per India’s Energy Conservation Building Code 2017 for fully air-conditioned buildings. The results indicate an 18% to 29% reduction in Operational Carbon Emissions can be achieved in this way substantially helping the move towards meeting the Net Zero Emissions ambitions.

Supported by:

Ministry of New and Renewable Energy Govt. of India, Gujarat Energy Development Agency, U.S. Agency for International Development iNDEXTb (Industrial Extension Bureau) Govt. of Gujarat, Shakti Sustainable Energy Foundation, New Delhi