The Air Emissions And Water Consumption Of Combined Cooling, Heat, And Power Systems And Renewable Energy Systems For Commercial Buildings In The United States

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Broesicke, Osvaldo Alejandro
Crittenden, John C.
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Within the next 30 years, the world’s energy demand will double as space-cooling demands increase and building services and transportation systems are electrified. Infrastructure investments are long-term decisions, and to mitigate and adapt to climate change impacts, cities are looking to invest in more sustainable and resilient infrastructures. Among these options, combined cooling, heating, and power (CCHP) systems are often portrayed as a more sustainable alternative to conventional fossil-fuel systems because 1) they have a higher conversion efficiency relative to other thermoelectric plants; 2) they are dispatchable and can produce energy in the absence of sunlight and wind; 3) they increase resilience to external stressors that could cause blackouts or brownouts. However, adopting a distributed CCHP-based system would require a massive reorganization of our existing energy infrastructure, and potentially lock cities into fossil-fuel dependency. Accordingly, stakeholders need to understand the long-term environmental impacts of a CCHP-based energy network to justify these investments. This research bridges the gap between energy planning and climate change mitigation/adaptation by investigating two understudied areas regarding CCHP systems, i.e., the air emissions and water consumption of distributed CCHP systems within various climates and power regimes. To do this, we developed energy-balance models of hybrid energy systems composed of the centralized power grid, conventional heating-and-cooling equipment, CCHP systems, and on-site renewable power generation. Each energy system supplies the hourly electric, heating, and cooling demands of 16 commercial building types in 16 climate zones of the United States. We quantified the greenhouse gas (GHG) emissions, conventional air pollutants (CAPs), fuel consumption, and water consumption associated with each hybrid energy system for each climate zone in the United States and 25 different power grids within the continental United States. Our results suggest that – despite their energy efficiency benefits – standard distributed CCHP systems may hinder the decarbonization goals of countries with ongoing renewable energy transitions and simultaneously increase regional water consumption – especially in water-stressed regions. Nonetheless, CCHPs may still prove invaluable towards reducing peak-energy demands considering the massive energy investments that will be required over the coming decades. The results presented in this dissertation highlight the potential benefits of CCHP systems and provide caution on the potential long-term consequences of these investments.
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