An LCA methodology to assess location-specific environmental externalities of integrated energy systems

Quantification of location-specific environmental effects attributable to the operation and future growth planning of integrated energy systems (IES) is an important part of quantitative sustainability analysis. Toward this end, this paper presents a Life Cycle Assessment methodology which accounts for diurnal and seasonal changes in emission rates from different supply and demand-side energy systems due to variations in the regional power generation energy portfolio mix. The proposed methodology has been illustrated using end-use monitored data for a whole year operation of a university campus IES. The analysis revealed that the average external costs of purchased electricity, specific to the local power utility fuel mix, were about 1.93 ¢/kWh, with ±8% diurnal and ±5% seasonal variations, while externalities from solar photovoltaics were four times lower. Depending on the amount of recovered heat, the externalities associated with the cogeneration system ranged from 1.86 ¢/kWh (with cogeneration total efficiency of 71%) to 4.36 ¢/kWh if no heat is recovered. The novel contribution of the proposed methodology is the ability to evaluate in real-time the environmental externalities associated with demand-side IES which will facilitate real-time sustainable operation of such systems in terms of dynamic building load management and optimal control and operation.