Piping system designed for low pressure drop saves pump energy.
This is a "best practices" approach to piping system design that saves energy and can often be a no-cost or low-cost strategy. This strategy has been developed and promoted by Factor Ten Engineering, a Rocky Mountain Institute initiative (http://www.rmi.org/rmi/10xE). Instead of using industry-standard rules of thumb to size the circulating loop piping, the designer optimizes pumping systems by increasing the pipe diameter. This reduces flow resistance, which saves pumping energy. However, this approach is not often implemented because the larger-diameter piping is more expensive. If, however, smaller pumps can be installed because of reduced flow resistance resulting from the use of larger-diameter pipes, valves, and fittings, the first cost for the entire system is reduced, and in some cases, first cost can actually be lower than with conventional pipe-sizing, resulting in an immediate payback for the strategy. The optimum sizing should be determined by minimizing life cycle costs of the entire system.
Energy savings can also be obtained through selection of pipe with a low friction factor i.e. pipe made of plastic or with a plastic coating and through selection of low pressure-drop valves and fittings. Another source of savings is through selection of a pump with a high efficiency at its operating point and which has a broad efficiency contour---meaning little reduction in efficiency when flows change. Lastly, for systems with variable flow requirements, provision of adjustable speed drives allow for efficient pumping over a broad range of operating conditions. This ET is certainly not "emerging" and can be simply be summarized as "do a good job with respect to design of hydraulic or fluid pumping systems". To implement this system widely in the Northwest, training should be provided to piping system designers that would have to be developed using standard civil engineering principles.
Status:
Baseline Description: 100 GPM with piping system at 7' head per 100 equalivant feet Baseline Energy Use: 22.6 kWh per year per ton
Typical sizing for hydronic is 3 GPM/ton. To circulate enough through a typical medium office building, 100 GPM through a 2.5" pipe would require a 1/2 hp pump. (75% min efficiency, 100 GPM, 7 feet of head loss per 100 ft piping length). Operating 2,000 hour per year. Annual energy use is thus 0.5 hp x 0.746 kW/hp x 2000 hours x 0.75 load /0.75 = 746 kWh/year per 33 tons = 22.6 kWh/year-ton.
"Typical" Savings: 33% Low and High Energy Savings: 20% to 35% Energy Savings Reliability: 2 - Concept validated
Typical sizing for a hydronic system is 2.5 to 3 GPM/ton. To circulate enough through a typical medium office building, 100 GPM through a larger pipe would require a pump with a 1/3 hp drive motor (75% min efficiency, 100 GPM, 3 feet of head loss per 100 feet of pipe length). Operating 100 gpm/3 gpm/ton = 33 tons, 2,000 hour per year. This would require 0.33 hp x 0.746 kW/hp x 2000 x 0.75 load /0.75 = 496 kWh/year for 33 tons or 15 kWh/year-ton. As the baseline design required 22.6 kWh/ton-year, the savings is equal to 33%.
Since pipe comes in finite sizes and there are minimum and maximum flow rate criteria, this should not be implemented without an engineer's approval.
Energy Use of an Emerging Technology is based upon the following algorithm. Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.
Kristine Chan-Lizardo, 01/01/2011. Big Pipes, Small Pumps: Interface, Inc. Rocky Mountain Institute
Natural Edge Project , 01/01/2007. Principles and Practices in Sustainable Development for the Engineering and Built Environment Professions The Natural Edge Project
CAC, 01/01/2014. Distribution Piping: Understanding Pressure Drop Compressed Air Challenge
John Weale, 02/01/2005. Low-Pressure Drop HVAC Design for Laboratories National Renewable Energy Laboratory
RMI, 01/01/2014. Factor Ten Engineering (10xE) Rocky Mountain Institute
Technical Advisory Group: 2010 HVAC TAG (#3) TAG Ranking: 30 out of 36 Average TAG Rating: 2.1 out of 5 TAG Ranking Date: 06/29/2010 TAG Rating Commentary: Cost/performance tradeoffs should be analyzed. VFD controllers on pumps could be more effective. Not emerging technology. "Good thing to do. Challenging to design a program around this. Most suitable as a technology for New Construction program. It is in category of "best practice" design."