Rising energy costs and environmental concerns increasingly require companies to improve their energy efficiency in order to reduce operating costs, increase profits and reduce greenhouse gas emissions. This paper describes the development and implementation of an Energy Management System (EMS), a tool that helps promote energy efficient operation. The paper describes work done for two Shell sites, each having 2 ethylene plants. The average benefit of an effective EMS is estimated to be 3% to 5% reduction in the site's energy cost. Consequently, an EMS can be an effective tool to help sites minimize CO2 emissions.
An EMS is a combination of structured management processes and monitoring tools, linked to real-time plant data systems, that aims to continuously reduce energy costs, bottlenecks and emissions, by human intervention.
Monitoring tool elements include items like measurement requirements, identification of key performance indicators (KPI) and drivers, (i.e. any process variable that influences the changes and variability in the selected KPI), software and hardware specifications and graphical user interface requirements. As an example, a KPI for an olefin plant would be the plant's total energy consumption per unit high-valued chemical (HVC) production, while for the ethylene cracker furnace it could be the total energy loss through the furnace stack caused by deviation of drivers like excess O2 and/ or high stack temperatures away from their targets.
Management process elements, which include the definition of responsibilities and accountabilities for energy utilization and encouragement of participation and involvement of personnel across all levels of the site, ensure energy optimal operation of the plant.