Energy budget control in manufacturing systems with on-site energy generation: an advanced methodology for analyzing specific cost variations

In light of the growing competitiveness in global economy and the raising energy prices, energy budget management is an increasingly critical aspect for manufacturing companies. However, the analysis of the energy budget variation over time can be challenging due to numerous parameters affecting specific energy cost and energy consumption. The present study falls within the context of various works in literature concerning energy budget control and has the purpose of focusing the analysis on complex manufacturing systems including an on-site energy generation plant. In this case, the contributions of energy produced on-site, purchased and sold will contribute to the definition of the specific energy cost, which will be in turn influenced by several factors such as market prices of the resources (electricity, fossil fuel), specific characteristics of consumption (quantity and load synchronization), efficiency of the production system. In order to implement a comprehensive control of the energy budget, the difference between the predicted values and the real ones (budget variations) should be broken down into various components. This work proposes a methodology to decompose budget variations, defining a series of indicators at different levels associated to the single components influencing the variation itself, thus enabling the identification of the specific causes. This methodology has been developed in response to the demand of a specific company but can also be applied to others with similar configurations, given the interest recently aroused in this topic. Its application in an industrial context is then presented. The result of this work is the definition of a system of indicators allowing the identification of the different causes of the budget variance. The clear attribution of such deviations to different responsibility centers is enabled by the identification of a set of parameters to keep under control, hence supporting the company in the definition of timely countermeasures.