Energy consumption from commercial buildings is a major contributor of greenhouse gas emissions. In the UK, supermarkets consume 3% of the electricity and account for 1% of the country’s carbon emissions (Tassou et al. 2011). This paper explores the implementation of bio-methane fuelled combined heat and power (CHP) systems to satisfy heat and electricity demands of commercial buildings; with the overarching goal of making cost-effective investments and decarbonizing building operations. The research work consists in the development of a CHP technology selection and operation (TSO) optimization model. Results from this effort can be utilized to develop a strategy for investment in bio-methane CHP projects for a portfolio of supermarket buildings.
The TSO model enables a new approach for the selection and operation of CHP units that encompasses whole life costing, carbon emissions as well as half-hourly energy prices and demands throughout the day, seasonally and annually, providing a more comprehensive result than current methods. Utilising historic metered energy demands, projected energy prices and a portfolio of available CHP technologies, the mathematical model solves simultaneously for an optimal CHP unit selection and operational schedule for a determined building based on a preferred objective. The objective can either be: minimum cost, minimum GHG emissions, or a mix of both for an operational period that satisfies the store's energy demands. The model defines which unit to acquire and its power output for each half-hourly interval for different day types and a given time period.
The TSO model was implemented for a sample of 35 buildings from a group of over 1300 stores that belong to a supermarket chain in the UK. These varied in characteristics such as heat-to-power ratio, size, and electricity pricing region. It was identified that the majority of stores assessed could reduce their operational emissions more than 70% while providing returns on investment above 100% by installing low-carbon co-generation units. Results of this model prove that attractive cost and emissions savings are possible through the optimal selection and operation of CHP technologies fuelled by bio-methane.
