The Energy Water Nexus

August 27, 2015

Figure 1. Greenhouse Gas Intensity Change for Water Supply Infrastructure Components of Different Alternative Water Supply Methods at 50.3% Renewable Electricity

PR = Water Purification and Reuse
UC = Urban Water Conservation
MD = Membrane Desalination distributed by urban population
MDSC = Membrane Desalination emphasized in higher population areas
TD = Thermal Desalination using natural gas
TDw = Thermal Desalination using waste heat

The different colors represent the change in greenhouse gas emissions intensity for different components of the water supply infrastructure.

"Direct" - Greenhouse gas emissions sourced directly from the facility implementing this measure
"Plant" - Emissions due to the electric load produced by the facility
"Conv." - Emissions due to energy use for water conveyance
"Trea." - Emissions due to energy use treatment
"Dist." - Emissions due to energy use in water distribution
"WWT" - Emissions due to energy use in wastewater treatment plants

The California Energy Commission recently awarded a research grant to APEP in collaboration with Water UCI for their proposal entitled "Building a Climate-Change Resilient Electricity System for Meeting California's Energy and Environmental Goals." The focus is on determining the climate change related hydrological and atmospheric impacts on the resiliency and sustainability of the electrical system. Additional research involves investigating the impact of shifting precipitation patterns and drought on hydropower generation and grid reliability. Implementing alternative water supply measures has a diverse range of impacts on the energy infrastructure including but not limited to, direct energy usage, the introduction of large electric loads of varying profiles, and changes in the amount of energy utilized for conveyance, treatment, distribution, and wastewater post-treatment.

These impacts have implications for greenhouse gas emissions from the combined energy-water system, therefore the energy infrastructure to support these methods needs to be understood. Due to the intensity of energy usage and spatial location within the topology of the infrastructure, each measure impacts the water supply infrastructure differently, however, on a large scale there can be synergies between developing sustainable water and energy supplies.

In California with a 50.3% share of renewable resources on the electric grid, Figure 1 presents the change in greenhouse gas intensity per unit of water produced, when implementing different alternative water supply methods on different aspects of the water supply infrastructure [1]. Overall, implementing a measure may reduce emissions from one component, but increase it for another, highlighting the importance of capturing these impacts for an accurate greenhouse gas assessment for any given region. Site maintained by the Advanced Power and Energy Program, UC Irvine