Impact of water consumption on the economic viability of energy efficiency improvements for industrial steam systems

Industrial energy conservation measures (ECMs) are important components of efforts to reduce global energy consumption and carbon emissions. To aid in assessing water conservation co-benefits of ECMs applied to industrial steam systems, this study proposes a combined energy-water conservation metric that captures the cost of conserved energy and water (CCEW) for common steam system-related ECMs. The proposed metric utilizes a fundamentals-based steam system model coupled with US industrial energy audit data to estimate potential water savings for 21 common ECMs in US industrial plants. At an average water cost of $0.71/kL ($2.66/1000 gal.), improvements to steam distribution, steam vents, de-aerator operation, steam traps, and steam leaks, which correlate to a reduction in steam generation requirements, are shown to have a CCEW that is 0.22 $/GJ lower than the conventional cost of conserved (CCE) for these ECMs. Furthermore, improvements to boiler system blowdown, which correlate to a reduction in liquid water purged from the system, are shown to have a CCEW that is 0.83 $/GJ lower than the CCE for this ECM. The study results demonstrate how broader consideration of water savings can improve the economic case for industrial ECMs.