New HVAC Sustainability Index—TWI (Total Water Impact)

Abstract

Sales of air conditioning are growing rapidly in buildings, more than tripling between 1990 and 2016. This energy use for air conditioning comes from a combination of rising temperatures, rising population and economic growth. Energy demand for climate control will triple by 2050, consuming more energy than that currently consumed altogether by the United States, the European Union and Japan. This increase in energy will directly impact water consumption, either to directly cool a condenser of an equipment or to serve indirectly as a basis for energy sources such as hydroelectric power that feed these heating, ventilation and air conditioning (HVAC) systems. Knowing the unique and growing importance of water, a new index, Total Water Impact (TWI) is presented, which allows a holistic comparison of the impact of water use on water, air and evaporative condensation climate systems. 200 and 500 TON (tons of refrigeration) air-cooled and water-cooled systems are theoretically compared to evaluate the general water consumption level. The TWI index is higher in the smallest water condensing system. That is, holistically, water consumption is higher in the water condensing system than in the air condensing system. Thus, this index provides a new insight about energy consumption and ultimately, about sustainability.