An energy audit alone doesn’t reduce energy use or energy costs. Energy efficiency can only be achieved once opportunities identified by the audit are implemented. However, continuous monitoring and repeat auditing ensure benefits last and help pinpoint areas for further improvements. Follow these five steps to maintain energy savings.
Step 1. Continuously monitor the energy use of energy-intensive process units and equipment as well as the overall plant. Energy Index reporting practiced by petroleum refineries provides a good example of energy use monitoring. Several software tools are available for energy performance evaluation and monitoring. The tools, downloadable for free from the U.S. Department of Energy (DOE) website (www.energy.gov/eere/amo/software-tools), are very useful to analyze the energy efficiency of equipment and systems. The DOE software available includes Steam System Tool Suite (SSTS), Process Heating Analysis & Survey Tool (PHAST), Compressed Air System Tool (AirMaster+), Fan System Assessment Tool (FSAT) and Pumping System Assessment Tool (PSAT). Some software tools also are capable of evaluating common improvement projects.
Plant engineers also could develop modules and macros to summarize actual field data continuously acquired from the plant in spreadsheets and data tables. The summarized data should be validated and analyzed at periodic intervals to evaluate the Key Performance Indicators (KPI) for the plant’s energy use and efficiency.
Step 2. Involve employees who help implement the energy-saving project. Energy cost control efforts start with the blessing of the top management and are coordinated by the plant’s energy manager or engineer. However, implementing the recommendations involves personnel in the operations, maintenance, materials and instrumentation groups. Their contributions are an “add-on” responsibility to them, and if they’re not convinced or not motivated enough, any effort to save energy could diminish and eventually fail. Involving all contributing members at all the phases of the energy cost control effort might take some additional time, but would ensure commitment from the whole team. A committed team could speed up implementation and sometimes even lower the initial budget. For example, in an edible-oil-based oleo chemical plant, the previously flared bio-gas was effectively utilized to generate hot water and steam, saving natural gas. The in-house project engineers recommended getting about 70% of the project material from old equipment on site. Only a new burner, its fuel control train and the required instruments were procured new. This was only possible because of motivated team members.
Step 3. Verify results. Because the implementation phase could extend several months, all personnel involved in the project should meet on a regular basis to review the completed tasks and their impact on the overall plant energy use. If savings are less than expected, determine the reason for the discrepancy and record any “Lessons Learned.” Occasionally, energy savings at one location may affect the energy use at another location. For example, waste heat recovery by preheating the makeup boiler feed water may lead to excess low-pressure (LP) steam venting. When this occurs, the team needs to identify a suitable steam-turbine drive and switch over to its motor drive. The ultimate objective is to control and reduce the plant’s overall energy cost.
Step 4. Conduct follow-up energy audits periodically. An energy-optimized system could easily deviate to higher energy usage due to changing operating conditions and gradual aging of equipment. Base the frequency of follow-up energy audits on the energy use monitoring, periodic inspections and preventive maintenance actions. Well-maintained and monitored equipment and systems provide high quality output at the maximum efficiency, preserve the safe conditions and experience longer service life with fewer failures, leading to less energy use.
Step 5. Publicize successful implementation results and recognize employee contributions. Share results and accomplishments with top management, organize recognition programs for group and individual achievements, and nominate employees to training programs on energy efficiency improvements.
Following the above five steps could sustain energy cost control efforts and repeat cycles with continuous improvement at any plant. Development of a motivated energy cost optimization team could be an added benefit.
VEN V. VENKATESAN is Chemical Processing's Energy Columnist. You can e-mail him at firstname.lastname@example.org