Go to Content | Go to Page Updated Information | Go to Footer
Welcome to the California Energy Commission

Public Interest Energy Research Program: Final Project Report

cover of report Refining Estimates of Water-Related Energy Use in California

Publication Number: CEC-500-2006-118
Publication Date: December 2006
PIER Program Area: Industrial, Agricultural and Water End-Use Energy Efficiency Research

The executive summary, abstract and table of contents for this report are available below. This publication is available as an Adobe Acrobat Portable Document Format File. In order to download, read and print PDF files, you will need a copy of the free Acrobat Reader software installed in and configured for your computer. The software can be downloaded from Adobe Systems Incorporated's website.

Download Report in Acrobat PDF ( 95 pages, 638 kilobytes )



Abstract

In 2005, the California Energy Commission published a report, California's Water-Energy Relationship (CEC-700-2005-011-SF), that estimates the magnitude and intensity of water-related energy consumption by segment of the water-use cycle. Because water-energy is a new area of study, and data were not readily available, this report relied on a number of different data sources and methods to develop the magnitude and intensity estimates.

The current study reviewed and updated these estimates for the magnitude and intensity of water-related energy consumption by segment of the water-use cycle. This review indicates that while the data and methods used to prepare the Energy Commission's 2005 report were not perfect, they offered a reasonable starting place for prioritizing water-energy research and development, as outlined in the Energy Commission's 2005 Integrated Energy Policy Report. Further, this study provided adjusted water-energy proxies that are sufficient for informing policy and prioritization of research and development investments. The study also describes important data gaps and includes the collection of primary data from water utilities and the disaggregation of data geographically and within water-use cycle segments. A greater understanding of the sub-segments of the water-use cycle offers an opportunity to more effectively target research and development decisions at the technology level, and a phased approach is recommended to continually refine water-related energy intensity estimates on an ongoing basis.

Keywords: water-use cycle, water-related energy, research and development, California's water-energy relationship, embedded energy, water, wastewater, water-energy, water supply, water conveyance, water treatment, water energy intensity, agricultural water use, urban water use, industrial water use, residential water use, commercial water



Executive Summary

Introduction

In 2005, the California Energy Commission published a report California's Water-Energy Relationship (WER) (publication # CEC-700-2005-011-SF - PDF file, 180 pages, 1.3 megabytes), that estimated the magnitude and intensity of water-related energy consumption by segment of the water-use cycle. These estimates were used to develop a proxy, or representative, valuation of the amount of energy deemed embedded in a unit of water, by virtue of the amount of energy consumed in collecting, extracting, conveying, treating, and distributing the water to end users (upstream embedded energy) and then by treating and disposing of the wastewater (downstream embedded energy). The Energy Commission's 2005 Integrated Energy Policy Report (IEPR - publication # CEC-100-2005-007-CMF) relied on these estimates and the proxy. However, Energy Commission recognized that the data used to prepare the estimates and the proxy were limited, given that investigation of the water-energy relationship is a relatively new field.


Purpose

Looking to ensure that the data used in the 2005 reports were a good basis for informing research and development (R&D) decisions, the California Energy Commission's Public Interest Energy Research (PIER) division retained Navigant Consulting, Inc. to assist in reviewing the data, estimates, and proxy in the initial reports.


Project Objectives

  • To review and document the bases for the Energy Commission's 2005 Integrated Energy Policy Report estimates of water-related energy magnitudes and intensities

  • To determine whether the data and methodologies employed to develop these estimates were reasonable and can be used by PIER to prioritize its investments in water-energy research and development

  • To identify beneficial adjustments to the data, methodologies, estimates and/or structure of the proxies

  • To evaluate the relative merits of applying these estimates to different purposes

  • To identify additional work needed to remedy critical gaps in data and methods that may otherwise impair PIER's ability to make informed R&D investment decisions


Project Approach

The distinct differences in the regional characteristics of the state's water supply and conveyance systems suggested that two separate proxies be established—one for Southern California and one for Northern California. To establish a consistent benchmark for evaluating the relative values of these proxies, the study team estimated the amount of energy needed for each segment of the water-use cycle in terms of the number of kilowatt-hours (kWh) needed to collect, extract, convey, treat, and distribute one million gallons (MG) of water, and the number of kWh needed to treat and dispose of the same quantity of wastewater.

Inasmuch as water-energy is a new area of study, data were not readily available that directly related energy use to portions of the water-use cycle. Consequently, the team adjusted the existing data sets to prepare refined estimates.


Project Outcomes

Through detailed reviews of work papers and interviews with stakeholders, the study team identified a number of recommended adjustments to the water-energy relationship proxies for energy embedded in water for Northern and Southern California. Some of the recommended adjustments addressed a number of minor errors and inconsistencies in allocations made during the preparation of the WER. Others addressed adjustments needed to ensure consistency. In addition, the team recommends adjusting the estimates by segment of the water-use cycle for losses.

The type of water use determines whether wastewater treatment and disposal will be required. In general, outdoor water use, such as landscape irrigation, typically either flows into storm drains or recharges groundwater or natural waterways, bypassing need for wastewater treatment and disposal. Indoor water use typically discharges to sanitary sewers, consuming energy for wastewater treatment and disposal. To simplify application of the proxies, we recommend further breaking down the northern and southern proxies into indoor and outdoor use.

Table ES-1. Recommended revised water-energy proxies

Indoor Uses Outdoor Uses
  Northern California
kWh/MG
Southern California
kWh/MG
Northern California
kWh/MG
Southern California
kWh/MG
Water Supply and Conveyance 2,117 9,727 2,117 9,727
Water Treatment 111 111 111 111
Water Distribution 1,272 1,272 1,272 1,272
Wastewater Treatment 1,911 1,911 0 0
Regional Total 5,411 13,022 3,500 11,111

The bases for the recommended adjustments are provided in Section 2 and the appendices to this report.


Conclusions

This review indicates that while the WER data and methods were not perfect, the results were not unreasonable.

While some of the adjustments recommended in this report are arithmetically significant, these are not deemed to impair the viability of the WER's general approach and proposed structure for valuing embedded energy upstream and downstream of water end use. The primary purpose of the proxy from PIER's perspective is to help make informed investment decisions. In this context, the following is clear:

  • In general, indoor water uses have a higher energy intensity than outdoor water uses, and Southern California water has a higher energy intensity than Northern California water.

  • Energy applied in the consumption of water by agricultural and urban end uses—typically, pumping, and heating—accounts for more than 50 percent of the water-related energy consumption identified in the WER.

  • Other water-related energy is consumed by water industry operations. The magnitude and intensity of energy consumption by water operations determines the amount of energy that can be saved by saving water.

  • The segments of the water-use cycle outside of the retail water meter with highest variability in energy intensity and magnitude of energy use are supply and conveyance. Therefore, these segments offer the highest potential for significant energy savings.

  • Energy magnitude and intensity are not the sole determinants of energy savings potential. The ability to influence that magnitude or intensity, whether through changed systems and operations or new technologies, must also be considered in targeting R&D investments.

  • Further disaggregation of energy magnitudes and intensities by sub-segments of the water-use cycle can facilitate better targeting of R&D investments. It can also help to inform the design of incentives for reducing water-related energy consumption.


Recommendations

  • The adjusted WER proxies in Table ES-1 (repeated as Table 7) are sufficient for informing policy and prioritization of research and development investments.

  • Drilling down into sub-segments of the water-use cycle offers an opportunity to more effectively target R&D decisions at the technology level.

  • Supply and conveyance have both the highest energy magnitude and the greatest variability in energy intensity of options. These segments of the water-use cycle need further study to better understand the key drivers of energy intensity and the magnitude of potential benefits for various supply options.

  • Data gaps that should be addressed are described in Table 14 and include the collection of primary data from water utilities and the disaggregation of data geographically and within water-use cycle segments.

  • A phased approach should be undertaken to continually refine water-related energy intensity estimates on a going forward basis.


Benefits to California

This study has helped confirm the validity of using existing estimates and proxies (as adjusted in this report) for making decisions about water and energy R&D in California--despite any imperfections in the data or methods used to create these estimates and proxies. In fact, as this study has underscored, the decision making process is inherently iterative: decisions often lead to the development and improvement of data, which in turn inform the refinement of decisions.

Further, the recommendations in this report can improve existing data—and related decisions—in a very short timeframe. The report also suggests a consistent and cost-effective method for improving and augmenting data over time, recommending logical steps to take in the near-, mid-, and long-term. Following the recommendations and findings in this report can help California continue to make sound, effective, and beneficial decisions concerning water and energy R&D, both now and in the future.



Table of Contents

Preface i
Abstract vi
Executive Summary 1
1.0 Introduction 5
1.1. Overview 6
1.2. Average and Marginal Water Supplies 9
2.0 Baseline Estimates of the Magnitude and Intensity of Water-Related Energy Use in California 13
2.1. Baseline Estimates of Magnitude 13
2.2. Baseline Estimates of Intensity 18
3.0 Critical Variables 23
3.1. High Magnitude Variables 23
3.2. Ability to Increase Energy Efficiency 26
3.3. Potential to Increase Energy Efficiency via Technological Developments 26
3.4. Research and Development Implications 27
4.0 Incremental Refinement of Energy Intensity Estimates 32
4.1. Validity and Usefulness of Current Energy Intensity Estimates 33
4.2. Long-Term Goals in Refining Energy Intensity Estimates 33
4.3. Resolution of Data Deficiencies 43
4.4. Proposed Incremental Actions for Refining Energy Intensity Estimates 44
5.0 Conclusions and Recommendations 47
5.1. Conclusions 47
5.2. Recommendations 48
5.3. Benefits to California 48
6.0 References 50
7.0 Glossary 52

Appendix A. Contacts and Communication
Appendix B. Energy Intensity Data Points From Studies Reviewed or Discussed
Appendix C. Recommended Adjustments to Baseline Estimates of the Magnitude and Intensity of Water-Related Energy Use in California

List of Figures
Figure 1. The water-use cycle 8
Figure 2. Average and marginal water sources 10

List of Tables
Table ES-1. Recommended revised water-energy proxies 2
Table 1. Range of energy intensities for water-use cycle segments 8
Table 2. WER Appendix B approach to computing water-related energy use 14
Table 3. Recommended adjustments to WER Table 1-1 16
Table 4. Electricity use in typical urban water systems (as shown in WER Table 1-3) 18
Table 5. Recommended loss adjustment factors 20
Table 6. Recommended adjustments to WER Table 1-3 21
Table 7. Recommended revised water-energy proxies 22
Table 8. Updated range of energy intensities for water-use cycle segments 24
Table 9. Urban water intensity matrix (kWh/MG) 25
Table 10. Illustrative and partial list of opportunities for improving the energy efficiency of the water-use cycle 29
Table 11. Potential geographic and/or jurisdictional disaggregation levels 37
Table 12. Urban water intensity matrix (kWh/MG) 39
Table 13 . Agricultural water intensity matrix (kWh/MG) 39
Table 14: Existing data gaps in refining water-related energy intensity estimates 44
Table 15. Potential approach to refining water-related energy intensity estimates 45
Table 10. Illustrative and partial list of opportunities for improving the energy efficiency of the water-use cycle 29
Table 11. Potential geographic and/or jurisdictional disaggregation levels 37
Table 12. Urban water intensity matrix (kWh/MG) 39
Table 13 . Agricultural water intensity matrix (kWh/MG) 39
Table 14: Existing data gaps in refining water-related energy intensity estimates 44
Table 15. Potential approach to refining water-related energy intensity estimates 45
Page Updated:
Go to Content | Go to Page Updated Information | Go to Footer