Author: Eoin O'Driscoll, doctoral researcher, Department of Mechanical and Manufacturing Engineering, Trinity College Dublin
According to the recently published Fifth Assessment Report (AR5) from the Intergovernmental Panel on Climate Change (IPCC), it is extremely likely – 95% certain – that the majority of the observed increase in global surface temperature between 1951 and 2010 has been caused by anthropogenic influences.
The report projects that if global greenhouse gas emissions continue on their current trajectory, sea levels will rise at a faster rate than previously predicted, heat waves and droughts will last longer, and storms will become more intense and frequent. Furthermore, it confirms that, in order to overcome the climate and energy challenges that we are now facing, major changes are required.
At a national level, there is a need for decision makers to develop and implement proactive, integrated policies and strategies that will assist all economic sectors to manage resources in a more sustainable way. The long-term solution requires a combination of smart electricity grids, time of use consumption tariffs and expanded renewable energy generation capacity.
In the short term, however, the International Energy Agency (IEA) believes that more efficient energy consumption has the potential to make the most significant contribution. Focusing on the industrial sector, the IEA has reported that up to 26% of the industrial sector's energy consumption could be saved each year if all proven technologies and best practices were implemented.
Within the manufacturing sector, a combination of increasing energy costs, corporate image concerns, and environmental legislation are driving a transition towards energy and resource efficiency. Developing a more comprehensive understanding of how energy is consumed within manufacturing facilities is now a core component of research efforts aiming to advance industrial energy efficiency.
From an Irish perspective, these research efforts are being led by a number of university-industry collaborations including bilateral research projects and multi-stakeholder research initiatives including Innovation for Ireland's Energy Efficiency (I2E2) and the International Energy Research Centre (IERC).
Manufacturing enterprises typically reduce their environmental impact by reducing utility expenditure in a number of ways: implementing energy efficient technologies, removing outdated equipment, running energy awareness programmes for staff and implementing lean manufacturing strategies. The aforementioned energy-saving initiatives can all produce significant savings, however it is widely recognised that energy consumption in manufacturing facilities can only be fully optimised if it has been accurately quantified [1, 2, 3].
CONCEPT FOR HIGHLIGHTING ENERGY CONSUMPTION
A recent research collaboration between DePuy and the Department of Mechanical and Manufacturing Engineering, Trinity College Dublin, developed a concept for highlighting energy consumption at a machine tool and value stream production level in combination with traditional energy metrics typically available to facilities personnel. The project successfully designed a novel metering strategy, sourced and implemented a state-of-the-art energy metering system within the DePuy manufacturing facility and developed novel energy consumption characterisation approaches.
[caption id="attachment_9215" align="alignright" width="742"] Figure 1: Energy consumption transparency  (click to enlarge)[/caption]The newly installed energy metering system facilitates a disaggregation of energy consumption – an ISO 50001 energy management system standard requirement – and also supports the continuous improvement of energy performance throughout the manufacturing facility. The installed energy measurement infrastructure provides stakeholders at DePuy with a level of energy consumption transparency that is typically only available in research labs; an example of this is shown in Figure 1.
From figure 1 it can be seen that at facility level, basic metering equipment is typically installed between the utility provider and the main facility electrical incomer; this information is then used as a means to query monthly utility bills. Site-level energy consumption information can also be used to monitor overall consumption trends allowing more efficient energy procurement and better utility contract management, e.g. optimising maximum import capacity (MIC) commitments.
The next level of the hierarchy includes the facility's significant energy users (SEUs): the main contributors to the facility's overall energy consumption. Examples of typical SEUs in the manufacturing sector include compressed air, production equipment and heating, ventilation, and air conditioning (HVAC). The identification of SEUs and the quantification of their energy usage allow a number of improvements to be made including the establishment of an energy baseline as well as the development of SEU energy performance indicators (EnPIs) that can be continuously monitored.
Opportunities for energy savings exist within each SEU. Operational strategies including setback control – allowing air temperature to rise in unoccupied areas – and enhanced economiser control can be used to improve the energy performance of HVAC systems. Lighting installations can be improved by installing the most energy efficient light fittings with presence detecting sensors. The energetic performance of compressed air systems can be enhanced by installing variable-speed air compressors, minimising inlet air temperature, and regularly cleaning air filters. The key enabler of the above improvement projects is effective energy measurement, which can identify the most beneficial energy performance upgrades and also verify the savings made after implementation.
From the perspective of production equipment, the availability of continuous energy consumption data, coupled with the empowerment of individuals directly responsible for energy consumption, is another proven cost saving methodology. This type of ‘energy ownership’ approach – where production line managers are directly responsible for energy consumption – promotes competition between production lines and incentivises behavioural changes and operational energy savings.
ENERGY-CONSCIOUS PRODUCTION SCHEDULING
Energy-conscious production scheduling is one approach that value-stream managers may adapt in order to achieve energy savings. Production schedules are typically optimised with respect to cycle times and throughput without considering energy costs, however, current state-of-the-art research is focusing on intelligent production schedules that avoid the creation of energy consumption peaks and perform energy intensive tasks during low-tariff periods.
In order to fully exploit the energy savings that are available at each level of the manufacturing hierarchy, a robust framework facilitating the accurate measurement, recording, and analysis of energy consumption is required. The inclusion of an energy metering system within a structured ISO 50001 energy management framework equips management with the tools necessary to effectively monitor and control their facility's energy requirements.
The implementation of energy efficiency projects within the Irish manufacturing sector is just one aspect of the multi-faceted approach that is required to address the issues raised in the IPCC's Fifth Assessment Report. As engineers, it is our collective responsibility to continue developing an energy-conscious economy, based on clean technology and green innovation in order to secure a sustainable, long-term future for Ireland's manufacturing sector.
The research work described in this article is the result of an ongoing collaboration between the manufacturing engineering research group in Trinity College Dublin under the guidance of Dr Garret O'Donnell, and the energy research team in DePuy under the guidance of Dónal Óg Cusack. The funding was provided by the Irish Research Council and DePuy and is gratefully acknowledged.
Eoin O'Driscoll, BSc (Ing), PG Dip (Stat) is a PhD graduate student in the Department of Mechanical and Manufacturing Engineering, Trinity College Dublin. His PhD research focused on the characterisation of electrical energy consumption within manufacturing facilities. The project was an Irish Research Council funded Enterprise Partnership Scheme between DePuy and Trinity College Dublin. Eoin also has experience in the power generation sector, working as an operations engineer for Dalkia Alternative Energy.
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