District energy systems have been shown to improve energy efficiency, GHG emission reduction, and air quality, yet they are not as widely adopted as these benefits would imply. Extensive studies have been conducted to optimize district energy system design but typically focus on optimization for low carbon emissions and low life cycle cost, ignoring optimization of capital expense (CAPEX) during critical ramp-up. This paper proposes an analytical framework using Integer Programming for district energy system design and installation to simultaneously optimize CAPEX phasing and OPEX (operating expense) including ramp-up and operations. A case study was conducted with preliminary results showing that CAPEX and OPEX could be reduced by 3% and 5% respectively. This approach brings significant advantages to the project predictability and profitability thus strongly promotes the use of district energy technologies.
Keywords optimization, district energy, energy efficiency, ramp-up, installation phasing, operation