Cost-Emissions-Efficiency Tradeoff Analysis for Urban District Energy Systems With Distributed Energy Resources

The high population density in cities makes urban energy systems critical to the sustainable energy transition. District energy systems (DESs) with combined heat and power (CHP) plants are particularly important, as these long-term infrastructure investments form a foundation for this energy transition. Integrating distributed energy resources (DERs) into DESs can supercharge local and efficient production of electricity, heating, and cooling – achieving further cost, emissions, and fuel efficiency targets. While the promising impact of adopting DERs has been studied, a method to identify how each DER improves the ability to meet multiple objectives simultaneously remains lacking. This paper formulates an energy dispatch model of a DES with a CHP plant that can integrate battery and thermal storage, solar photovoltaics, solar water heaters, and absorption chillers. We provide a meta-heuristic solution framework to identify the Pareto-candidate solution set for cost, emissions, and CHP plant efficiency that this DES can achieve. We then apply Pareto tradeoff theory to identify the optimal dispatch schedule that meets multiple objectives simultaneously and quantify how the schedule improves through the inclusion of DERs. We also quantify how a DER installation can reduce tradeoffs between objectives, so the optimal cost, emission, and fuel efficiency schedules are more alike. The proposed analysis framework is tested on two DESs in Washington, D.C., which differ in scale and building types. Additionally, we show how the presence of a carbon tax can alter the impact that DERs have on the tradeoff analysis. This work offers a methodology that helps energy managers select the best DER installations that would meet multi-dimensional targets. Moreover, policymakers can understand which existing systems must sacrifice emission and fuel efficiency for cost, then strategically incentivize a multi-faceted energy transition.