Energy White Paper Perspectives on Water Supply Energy Use

Energy White PaperPerspectives on Water Supply Energy Use

City of Santa Cruz & Soquel Creek Water District scwd2 Desalination Program

Prepared by:

April 2011

ii Energy White Paper, Perspectives on Water Supply Energy Use

Table of Contents

Table of Contents ....................................................................................................................... ii

List of Tables ............................................................................................................................. iv

List of Figures ............................................................................................................................ iv

List of Appendices ..................................................................................................................... iv

Section 1: Executive Summary and Background ......................................... 1

1.1 Executive Summary .............................................................................. 1 1.2 Background .......................................................................................... 2 1.3 Current Water Supply Portfolios ............................................................ 2

1.3.1 SCWD Water Supply Portfolio ................................................... 2 1.3.2 SqCWD Water Supply Portfolio ................................................. 3

Section 2: Energy and Our Current Water Supply ........................................ 4

2.1 What is Energy? ................................................................................... 4 2.2 Our Society is Fundamentally Reliant on Energy .................................. 5 2.3 Our Current Water Supplies Require Energy ........................................ 6

2.3.1 SCWD Water Supply Energy Requirements .............................. 6 2.3.2 SqCWD Water Supply Energy Requirements ............................ 7

2.4 Typical Residential Energy Use Including Water Supply ....................... 8

Section 3: Desalination Energy Requirements ........................................... 12

3.1 The Seawater Desalination Process ................................................... 12 3.1.1 Seawater Desalination Has Become More Energy

Efficient ................................................................................... 13 3.2 Energy Use of Proposed Desalination Facility .................................... 14

Section 4: Putting Desalination Energy into Perspective .......................... 15

4.1 Desalination Energy Compared to Typical Santa Cruz Area Energy Uses ....................................................................................... 15

4.2 Water Supply Energy with Supplemental Desalination ........................ 16 4.2.1 SCWD Water Supply Energy with Supplemental

Desalination ............................................................................ 16 4.2.2 SqCWD Water Supply Energy with Supplemental

Desalination ............................................................................ 17 4.3 Desalination Energy Compared to Typical Household Energy

Uses ................................................................................................... 17

Table of Contents (cont'd)

Energy White Paper, Perspectives on Water Supply Energy Use iii

Section 5: Energy Minimization and Greenhouse Gas Reduction

Study .......................................................................................... 19

5.1 GHG Regulatory Guidelines ............................................................... 19 5.1.1 California Environmental Quality Act (CEQA) .......................... 19 5.1.2 California Global Warming Solutions Act (AB 32) .................... 20 5.1.3 California Coastal Commission and the California

Coastal Act ............................................................................. 21 5.1.4 Monterey Bay National Marine Sanctuary ............................... 21

5.2 Projected scwd2 Indirect GHG Emissions ........................................... 21 5.3 Putting Desalination GHG Emissions into Perspective ....................... 22 5.4 Investigating Renewable Energy and GHG Reduction Options .......... 23

References ............................................................................................................................... 24

iv Energy White Paper, Perspectives on Water Supply Energy Use

List of Tables

Table 2-1 Estimated SCWD Residential Annual Energy Consumption by End Use ............ 9 Table 2-2 Estimated SqCWD Residential Annual Energy Consumption by End Use ......... 10 Table 3-1 Conceptual Range of Energy Requirements of the Project ................................ 14

List of Figures

Figure 2-1 PG&E 2009 Power Mix ........................................................................................ 5 Figure 2-2 SCWD Graham Hill WTP ..................................................................................... 7 Figure 2-3 SqCWD Groundwater Pump ................................................................................ 8 Figure 2-4 Typical Santa Cruz Area Residential Energy Use Including Water Supply ........... 9 Figure 2-5 Estimated SCWD Residential Annual Energy Use ............................................. 10 Figure 2-6 Current SqCWD Residential Energy End Uses .................................................. 11 Figure 3-1 Desalination Plant in Pleasanton, CA ................................................................ 12 Figure 3-2 Typical Desalination Process ............................................................................. 13 Figure 3-3 Energy Consumption by the RO Desalination Process ...................................... 14 Figure 4-1 Desalination Energy Use Relative to Santa Cruz Area Demands ....................... 15 Figure 4-2 SCWD Residential Annual Energy Consumption with Supplemental Desalination

Water Supply ..................................................................................................... 16 Figure 4-3 SqCWD Residential Annual Energy Consumption with Supplemental

Desalination Water Supply ................................................................................. 17 Figure 4-4 scwd2 Household Desalination Water Supply Energy Equivalents ..................... 18 Figure 5-1 Categories of GHG Emissions ........................................................................... 20

List of Appendices

Appendix A: Units, Conversion Factors, and Calculations...................................................... 26

Energy White Paper, Perspectives on Water Supply Energy Use Page 1

Section 1: Executive Summary and Background

1.1 Executive Summary

The City of Santa Cruz Water Department (SCWD) and Soquel Creek Water District (SqCWD), partnering together as scwd2, are evaluating seawater desalination as a supplemental source to their current water supply portfolios. The energy requirement of seawater desalination is among the key issues in the evaluation of the proposed scwd2 Regional Seawater Desalination Project (Project). scwd2 is committed to thoroughly studying the potential energy use of the scwd2 Regional Seawater Desalination Project (Project).

A desalination facility uses electricity from the power grid, similar to a home or business. scwd2 is conducting the Energy Minimization and Greenhouse Gas Reduction Study to ensure that the most advanced and energy efficient technologies and approaches are identified and incorporated into the proposed Project and to inform the Project’s Environmental Impact Report (EIR). The study will also explore renewable energy options (such as photovoltaic solar systems, third party providers, etc.) to offset power requirements of the Project.

This paper serves as a preface to the scwd2 Energy Minimization and Greenhouse Gas Reduction Study. This paper will describe the energy requirements of traditional water supplies with those of the Project (which includes the water treatment facility as well as the related intake, pump stations, etc.), and compare the respective energy uses to typical energy requirements for a household. This comparison will put the energy requirements for desalination into broader perspective.

The proposed scwd2 Seawater Desalination Project, running at full capacity year-round would have a peak demand of 1.6 MW and require about 13,700 MWh of energy annually. In a typical, non-drought year, the facility is expected to run at half capacity and thereby require approximately 0.8 MW or about 6,800 MWh annually. This is a small to moderate amount of energy compared to other demands in our society. The desalination plant would use energy similar to a small manufacturing facility or mid-sized hospital.

The energy required to produce water from traditional supplies (such as surface water and groundwater) for customers served by the City of Santa Cruz or Soquel Creek Water District is approximately 0.5 to 0.7 percent of a household’s total energy usage. While the process of desalination requires more energy than a typical water supply, because desalinated water would be used only to supplement existing water supplies, the energy required to deliver water would become approximately 1 to 2.3 percent of the total energy used in a typical household. Although the water supply energy could increase by 2 to 3 times with desalination, the energy use is still only a small percentage of the energy we use in our households every day.

“…because desalinated water would be used

only to supplement existing water supplies

the energy required to deliver water would

become approximately 1 to 2.3 percent of the

total energy used in a typical household.”

Energy White Paper, Perspectives on Water Supply Energy Use

1.2 Background

The City of Santa Cruz Water Department (SCWD) Integrated Water Plan (IWP, 2005) and the Soquel Creek Water District (SqCWD) Integrated Resources Plan (IRP, 2006) provide a flexible, phased approach for providing a reliable high-quality supply of water while ensuring protection of public health and safety. The integrated water plans for both agencies include the following primary components:

Conservation – Permanently reduce customer demand for water and increase water use efficiency to obtain the greatest public benefit from available supplies.

Curtailment – Further reduce water use by up to 15 percent through temporary water restrictions during times of drought.

Supplemental Supply – Construct a small regional 2.5 million gallon per day (MGD) desalination plant to provide supplemental water during drought and to help protect our coastal aquifers.

SCWD and SqCWD are collaborating to conserve, protect, and create a reliable water supply portfolio. The two agencies have partnered, forming the scwd2 Task Force, to implement the scwd2 Desalination Program. Development and use of the desalination plant and related facilities is being pursued by both agencies through an operational agreement. The scwd2 Desalination Program proposes a seawater desalination project to provide up to 2.5 million gallons per day (mgd) of water as a supplemental water supply. This water would help SqCWD meet its annual water needs as it reduces groundwater withdrawals of the over-drafted Soquel-Aptos area to prevent seawater intrusion. The desalination facility would help SCWD meet the water needs of its service area during drought periods as well as provide much needed operational flexibility should surface water reductions be required to protect endangered species.

1.3 Current Water Supply Portfolios

1.3.1 SCWD Water Supply Portfolio

The City of Santa Cruz (SCWD) relies primarily on surface water runoff that is captured in reservoirs or withdrawn through stream diversions. The SCWD also has several groundwater wells that seasonally supply about 5 percent of its water supply. The SCWD water supply facilities include:

Surface water storage in Loch Lomond Reservoir

Surface diversions from two locations on the San Lorenzo River

Surface diversions from three coastal streams and a natural spring (i.e., North Coast sources)

Groundwater from the Live Oak Wells. The SCWD system relies on surface runoff from local rainfall and groundwater infiltration. No water is purchased from State or Federal sources or otherwise imported to the region from


outside the Santa Cruz area. The strong reliance on surface water to provide nearly all of its water supply is the primary threat to the SCWD water system. Stream flows vary for a number of reasons including seasonal variations, drought, and potential long term impacts from climate change. If SCWD were faced with drought conditions similar to the 1977 drought, the SCWD would not have enough water to meet current demands; drought-related curtailment has historically been estimated to be as high as 45 percent. Even with ongoing conservation efforts and 15-percent additional rationing/water-use restrictions during drought, additional water supplies are needed to meet potable water needs for public health and safety, economic stability, and provide water for protection of endangered species.

1.3.2 SqCWD Water Supply Portfolio

SqCWD obtains 100 percent of its water supply from groundwater aquifers within the Soquel-Aptos area via production wells. Similar to SCWD, no water is purchased from State or Federal sources or imported to the region from outside the Santa Cruz area. The groundwater aquifers are located within two geologic formations that underlie the SqCWD service area, the Purisima Formation and the Aromas Red Sands aquifer. The Purisima Formation provides the majority of the SqCWD’s annual needs. These aquifers provide groundwater to SqCWD as well as other municipal utilities (such as SCWD, Central Water District, and the City of Watsonville), small mutual water districts or companies, and private well owners. The primary threat to the SqCWD water supply is overdrafting of the aquifers and the subsequent potential for seawater intrusion. The basin currently is in a state of overdraft, and the cumulative impact of pumping in excess of sustainable yields will eventually lead to seawater intrusion and to potential contamination of the groundwater basin. SqCWD has practiced groundwater management for over 25 years and continually monitors for changes in water quality and groundwater levels. In addition, to conserve and protect its potable water supply, SqCWD has joined SCWD to address common water supply issues. SqCWD needs to find a supplemental water supply that will permit them to reduce pumping from the overdrafted groundwater aquifers and naturally allow the coastal groundwater levels to rise and thereby prevent seawater intrusion.


Section 2: Energy and Our Current Water Supply

2.1 What is Energy?

The terms “power” and “energy” are often used, and sometimes confused, in discussions about energy requirements of a desalination facility. Power is a measurement of instantaneous electricity or force: this is also called energy demand. Scientific units of energy demand include watts (W) and horsepower (HP). For example, we may describe a power plant as having a capacity of 100 megawatts (MW), which is equivalent to 100 million watts. A vehicle often is described as having a 250 HP engine.

Energy is a term that describes energy demand over time and is equal to the instantaneous demand multiplied by the time that the demand is used, typically in hours.

Energy = Demand x Time

Scientific units of energy include watt-hours (W.h). For example, if a 100 MW power plant operated 24 hours per day for a year at maximum capacity, it would produce during that year:

100 MW x 24 hours/day x 365 days/year = 870,600 MWh of energy.

If the same power plant operated at only half its capacity (50 MW) for 24 hours per day over the year, then it would produce during that year:

50 MW x 24 hours/day x 365 days/year = 430,800 MWh (only half the amount of energy)

The appendix to this white paper includes additional descriptions, definitions, and relationships for units of power and energy, as well as detailed calculations to support energy numbers provided in the text.

Electricity on our California power grid comes from many different sources, including both fossil-fuel based and renewable energy sources. Pacific Gas and Electric (PG&E) supplies electricity for the power grid in the Santa Cruz area. The energy that PG&E produces emits a varying amount of greenhouse gases for every kilowatt-hour produced, depending on the mix of renewable and non-renewable energy sources. As a society, there is an increased awareness about reducing the amount of fossil-fuel, greenhouse gas-emitting energy we produce, and increasing the amount of renewable energy we produce, regardless of the end use of our energy. Figure 3-1 illustrates PG&E’s energy portfolio for 2009. Over time, PG&E anticipates that their energy portfolio will shift toward more climate neutral and renewable sources.


Figure 2-1 PG&E 2009 Power Mix

Source: PG&E, 2009.

2.2 Our Society is Fundamentally Reliant on Energy

Human societies worldwide are dependent on the use of energy. We use energy to cook our food, to provide light in the darkness, to heat or cool our homes, to transport ourselves and materials of commerce, and to run much of our machinery. Perceptions and ideas about energy use in our society are changing, with a greater awareness of the impacts of energy consumption on the environment and an emphasis on reducing the production of greenhouse gases that contribute to global climate change.

Some examples of power and energy use in our society include:

The state of California uses an average 257 million MWh of electrical energy per year, or about 7 MWh per capita per year. (California Energy Commission (CEC), 2009)

The average power plant in California can produce approximately 385 MW of electrical capacity. (CEC, 2011). The Moss Landing power plant, south of Santa Cruz, has a capacity of 2,500 MW. The Metcalf Energy Center in San Jose, CA has a capacity of 600 MW.

“Perceptions and ideas about energy use in

our society are changing, with … an

emphasis on reducing the production of

greenhouse gases that contribute to global

climate change.”


Large data centers are being built around the United States and the world to increase Internet bandwidth and download speeds. A proposed large Microsoft Chicago data center would require an electrical power capacity of 198 MW and could use up to 1,700,000 MWh of energy per year. (WDR, 2008). A smaller Internet Data Center, in Santa Cruz, operating with 30 data server racks, requires about 0.2 MW of power demand or 1,580 MWh per year of energy.

A typical refrigerator uses about 1,100 kWh per year, or about 6% of a California household’s energy use. A community of about 50,000 households (approximate number of households in each of the service areas for the City of Santa Cruz Water Department and the Soquel Creek Water District) requires about 6 MW of power demand or 54,000 MWh of energy for operating refrigerators for a period of one year. (Energy Information Administration (EIA), 2005)

Annual energy use for televisions in California is approximately 8.8 million MWh or about 725 kWh per year per household. A community of about 50,000 households requires about 4 MW of power demand or 36,000 MWh of energy for operating televisions for a period of one year. (CEC, 2009)

A mid-sized inpatient hospital with 200 to 300 beds similar to Dominican Hospital in Santa Cruz, CA, requires about 0.75 MW of power demand and consumes about 6,600 MWh of electricity annually. (EIA, 2003).

2.3 Our Current Water Supplies Require Energy

2.3.1 SCWD Water Supply Energy Requirements

The SCWD drinking water system relies on surface runoff from local rainfall and groundwater infiltration. Some of the surface water is captured in Loch Lomond and pumped to the Graham Hill Water Treatment Plant (WTP). Surface water diversions on the San Lorenzo River and the North Coast supplies also are pumped up to the Graham Hill WTP. Treated water flows by gravity to some areas of Santa Cruz. In other areas at higher elevations, the water must be pumped to storage tanks to provide enough pressure for use in homes and businesses and for fire protection. The primary energy requirements for SCWD’s current water supplies include:

Pumping energy to lift water to the Graham Hill WTP from all surface sources

Pumping energy to lift groundwater to the surface

Energy for the filtration and disinfection processes at the WTP

Pumping energy to move water and provide potable water pressure for portions of the Santa Cruz service area not served by gravity.

The SCWD Graham Hill WTP, which treats surface water to drinking water quality, is shown in Figure 2-2.


Figure 2-2 SCWD Graham Hill WTP

The water supplies for SCWD require approximately 1.4 kilowatt-hours (kwh) per one thousand gallons (kgal) of water delivered (1.4 kwh/kgal) for collection, treatment and delivery to customers. Residential water use is approximately 75 gallons per person per day. Assuming an average of 2.2 people for a residential connection, the average energy for water supply collection, treatment and delivery per household for SCWD is 83 kWh per year.

2.3.2 SqCWD Water Supply Energy Requirements

The SqCWD obtains all of its water supply from two separate groundwater aquifers. Groundwater wells and pumps located throughout the SqCWD service area lift the water several hundred feet to the ground surface. The water is disinfected and pumped to homes and businesses and storage tanks to provide enough pressure for potable water and fire protection. The primary energy requirements for SqCWD’s current water supplies include:

Pumping energy to lift water from underground up to the surface

Energy for the treatment (if needed) and disinfection processes at the wells

Pumping energy to move water and provide potable water pressure for the SqCWD service area.


A SqCWD pump, which treats groundwater to provide drinking water supply, is shown in Figure 2-3.

Figure 2-3 SqCWD Groundwater Pump

The SqCWD water supply requires approximately 2.1 kWh/kgal of water delivered. The energy requirements for SqCWD are higher than for SCWD because more energy is required to pump water from beneath the ground than to capture surface water. Assuming an average of 2.2 people for a residential connection, and a water use rate of approximately 75 gallons per person per day, the average energy for water supply collection, treatment and delivery per household for SqCWD is 129 kWh per year.

2.4 Typical Residential Energy Use Including Water Supply

In surveys of household energy consumption, the major electrical and natural gas energy uses include:

Home heating and air conditioning

Heating of water (water heaters)

Lighting and household appliances

Refrigeration

Because the energy for drinking water collection, treatment and delivery is associated with a community’s water utility infrastructure, water supply energy has not typically been considered in household energy consumption surveys. However, the water used by a household or business does require energy, as described above, and is worth considering in relation to other household energy uses.

“The water used by a household or business

does require energy … and is worth

considering in relation to other household

energy uses.”


Figures 2-4 and 2-5, and Table 2-1 show the estimated annual household energy consumption for a typical household in the SCWD service area, including energy for water supply. The Santa Cruz area is assumed to have similar residential energy use patterns as the rest of California with the exception of air conditioning, since Santa Cruz has a cooler coastal climate. The energy associated with air conditioning was removed from the 2005 US Department of Energy survey data to develop the typical household energy values below. (Calculations are shown in Appendix A).

Figure 2-4 Typical Santa Cruz Area Residential Energy Use Including Water

Supply

Table 2-1 Estimated SCWD Residential Annual Energy Consumption

by End Use

Water Heating Other Appliances

& Lighting Heating Refrigeration Water Supply Total

kWh/ household

6,828 5,773 4,601 1,084 83 18,370

% 37% 31% 25% 6% 0.5% 100%


Figure 2-5 Estimated SCWD Residential Annual Energy Use

The energy used for water supply (collection, treatment and distribution) is a small percentage of overall household energy use, and for each SCWD household is only approximately 0.5 percent of total household energy.

For SqCWD, the average household energy consumption is summarized in Table 2-2 and shown in Figure 2-6.

Table 2-2 Estimated SqCWD Residential Annual Energy Consumption by

End Use

Water Heating Other Appliances

& Lighting Heating Refrigeration Water Supply Total

kWh/ household

6,828 5,773 4,601 1,084 129 18,416

% 37% 31% 25% 6% 0.7% 100%


Figure 2-6 Current SqCWD Residential Energy End Uses

The SqCWD residential energy used for water supply (collection, treatment and distribution) is a small percentage of household energy use at only 0.7 percent of a household’s total energy. It is slightly greater than that of Santa Cruz because more energy is needed to pump water from beneath the ground than to capture surface water. NOTE: Although these figures show water supply as a household energy end use for comparative purposes, water supply energy is associated with a community’s water facilities, and does not show up on a household electricity use meter.


Section 3: Desalination Energy Requirements

3.1 The Seawater Desalination Process

The seawater desalination process withdraws water from the ocean, either through a screened intake or through the sands of the ocean floor, and delivers it to the treatment facility. At the desalination plant, the water is first filtered to remove “dirt” particles and bacteria from the water (just like the filtration treatment at the SCWD Graham Hill WTP). The filtered seawater is pumped at high pressure through reverse osmosis (RO) membranes that produce fresh water and water with concentrated salts. The fresh water is disinfected and treated to minimize corrosion (also similar to the SCWD Graham Hill WTP). The treated water is then pumped into the existing potable water distribution system. The desalination treatment processes are typically housed in a building that could look like an office building or business facility.

The scwd2 Desalination plant could look similar to this brackish water facility in Northern California, shown in Figure 3-1.

Figure 3-1 Desalination Plant in Pleasanton, CA


Figure 3-2 shows the general process steps for a typical seawater desalination facility.

Figure 3-2 Typical Desalination Process

The primary energy requirements for the proposed scwd2 Regional Seawater Desalination Project include:

Pumping energy to lift seawater from the ocean to the desalination facility

Energy for filtration processes

Energy for the RO desalination process Energy for the disinfection and corrosion reduction processes

Pumping energy to provide potable water pressure.

Of these energy uses, the seawater RO desalination process makes up the greatest part (approximately 70 percent) of the overall energy requirements.

3.1.1 Seawater Desalination Has Become More Energy Efficient

Improvements in RO membrane and energy recovery technology have cut the energy requirements for RO desalination to approximately one-third of what they were twenty years ago. With high efficiency design, the typical modern, high-efficiency desalination project uses about 15 kWh per thousand gallons of water produced (kWh/kgal). As shown in Figure 3-3, the most energy-intensive step of the treatment is seawater RO process.


Figure 3-3 Energy Consumption by the RO Desalination Process

The Affordable Desalination Collaboration (ADC) recently operated seawater RO equipment at a test facility in southern California that used approximately 8 kWh/kgal. The scwd2 Desalination Facility would be designed with similar advanced, high-efficiency energy recovery components to minimize the energy requirements of the seawater RO equipment.

Looking forward, nano-particle technology and other chemistry improvements to the RO membranes hold the promise of additional energy savings. However, because the energy for desalination is related to the salt levels in the water being treated, the laws of physics will eventually limit how much energy can be saved.

3.2 Energy Use of Proposed Desalination Facility

The SCWD and SqCWD propose to operate the seawater desalination facility to provide water to each agency at different times to meet the different objectives and needs of the two agencies. The amount of energy used for scwd2 Desalination Facility would depend on how much water is produced. Table 3-1 below summarizes a range of energy requirements of the proposed Project from half capacity to full capacity.

Table 3-1 Conceptual Range of Energy Requirements of the Project

Operating Condition

Half Capacity Full Capacity

Average Flow (Mgal/day)

1.25 2.5

Flow (Mgal/yr)

465 930

Electrical Demand (MW)

0.8 1.6

Energy (MWh/yr)

6,800 13,700

Disinfection & Pumping 2 kWh/kgal

SWRO 10 kWh/kgal

Filtration 2 kWh/kgal

Intake 1 kWh/kgal


Section 4: Putting Desalination Energy into Perspective

4.1 Desalination Energy Compared to Typical Santa Cruz Area

Energy Uses

The energy demands required by the proposed high-efficiency scwd2 Desalination Facility would be similar to a small manufacturing facility or a mid-sized hospital. In a typical year, the scwd2 Desalination Facility is expected to operate at about half capacity over the year. Figure 4-1 shows the average annual energy use of the scwd2 Desalination Facility compared to other typical Santa Cruz area energy uses, describe in Section 2.2.

Figure 4-1 Desalination Energy Use Relative to Santa Cruz Area Demands

For typical non-drought year operations, the annual energy use of the proposed scwd2 Desalination Facility of 6,800 kWh per year is equivalent to any one of the following examples:

The annual energy used by a mid-sized hospital such as Dominican Hospital.

The annual energy use (electric and gas) for approximately 370 Santa Cruz area households.

Annual refrigeration energy use for about 13% of households served by the Santa Cruz Water Department and Soquel Creek Water District.

Annual television energy use for about 20% of Santa Cruz of households served by the Santa Cruz Water Department and Soquel Creek Water District.


Compared to other typical energy demands and uses in the Santa Cruz Area, the proposed high-efficiency scwd2 Desalination Facility is relatively small to moderate in demand and average annual energy use.

4.2 Water Supply Energy with Supplemental Desalination

4.2.1 SCWD Water Supply Energy with Supplemental Desalination

In a drought year, desalinated seawater could account for up to 15 percent of the water portfolio for SCWD. With the supplemental desalination water supply, the annual SCWD household energy use for water supply would increase from 83 kWh per year to 183 KWh per year.

As shown in Figure 4-2, the percentage of household energy for water supply with supplemental desalination is 1 percent of overall household energy usage for the drought year. (This additional energy would not show up on a household electric meter, but is the energy associated with supplying water to a typical household.)

Figure 4-2 SCWD Residential Annual Energy Consumption with Supplemental

Desalination Water Supply

Typical household energy use with current water supply

Typical household energy use with current and supplemental desal water


4.2.2 SqCWD Water Supply

Energy with Supplemental

Desalination

In periods of non-drought, desalination could account for 30-40% of the water portfolio for the SqCWD. With this level of supplemental desalination water supply, SqCWD household energy use for water supply would increase from 129 kWh per year to approximately 429 KWh per year. As shown in Figure 4-3, the percentage of household energy for water supply with supplemental desalination would be 2.3 percent of overall household energy usage. This additional energy would not show up on a household electric meter, but is the energy associated with supplying water to a typical household.

Figure 4-3 SqCWD Residential Annual Energy Consumption with Supplemental

Desalination Water Supply

4.3 Desalination Energy Compared to Typical Household

Energy Uses

On a household basis, the additional annual energy associated with the supplemental desalination water supply could be approximately 100 kWh during a drought year for SCWD, and could be about 300 kWh per year for SqCWD. This is a relatively small amount of energy and is equivalent to:

Typical household energy use with current water supply

Typical household energy use with current and supplemental desal water

“… the percentage of household energy for

water supply with supplemental desalination

would be 2.3 percent of overall household

energy usage.”


One 35-watt CFL light bulb on for about 8 hours per day for SCWD, and on for about 24 hours per day for SqCWD.

The energy for a washing machine load (warm wash/cold rinse) for 1 to 3 loads per week.

The energy for a typical computer for about 1 to 3 hours per day (US DOE, 2009).

The energy saved by turning down the thermostat by about 1 or 2 oF in winter heating months (EIA, 1997).

Figure 4-4 scwd2 Household Desalination Water Supply Energy Equivalents

The energy required to treat seawater to drinking water standards is higher than for surface and groundwater sources: desalinated water, at15 kWh/kgal, is approximately 7 to 10 times the energy of the traditional water supply (1.4 to 2.1 kWh/kgal). However, because desalinated water will be used only to supplement existing water supplies, the energy required to deliver water could increase by 2 to 3 times. However, the water supply energy would still only be 1 to 2.3 percent of the total energy used in a typical household, and relatively small compared to other daily household energy uses.

“…because desalinated water will be used

only to supplement existing water supplies

the energy required to deliver water would

become approximately 1 to 2.3 percent of the

total energy used in a typical household.”


Section 5: Energy Minimization and Greenhouse Gas

Reduction Study

scwd2 is conducting an Energy Minimization and Greenhouse Gas (GHG) Reduction Study (Energy Study) to ensure that the most advanced and energy efficient technologies and approaches are identified and incorporated into the proposed Project, and to explore renewable energy projects to offset power requirements of the Project

The Energy Study will:

Describe current GHG regulatory guidelines.

Calculate estimated indirect GHG emissions from the project.

Compare the project emissions with potential baseline GHG goals to determine the amount of GHGs that could be reduced or mitigated.

Identify renewable energy and GHG mitigation options.

Prepare an Energy Minimization and Greenhouse Gas (GHG) Reduction Plan to meet the goals of the scwd2 Desalination Program.

The first several elements of the Energy Study are summarized below followed by next steps in development of this Study.

5.1 GHG Regulatory Guidelines

The following sections describe regulatory guidelines regarding seawater desalination energy use and GHG emissions that could inform or set energy minimization and GHG reduction requirements for the scwd2 Desalination Project. These sections also provide examples of energy or GHG minimization goals or requirements for other California desalination projects.

5.1.1 California Environmental Quality Act (CEQA)

The California Environmental Quality Act (CEQA) requires projects to investigate and report on potential environmental impacts of projects. For the scwd2 Desalination Project, SCWD and SqCWD will be required to complete an Environmental Impact Report (EIR), which must include an estimation of GHGs emissions associated with the project.

CEQA does not identify a threshold of significance for project-related GHGs, but allows the California Air Resources Board (CARB) and regional air quality management district’s to establish thresholds. Currently, thresholds vary based on agency and region. CARB has a preliminary draft significance threshold of 7,000 MT CO2e per year. Monterey Bay Unified Air Pollution Control District (MBUAPCD) currently does not have a threshold, but the nearby Bay

“scwd2 is conducting an Energy Minimization and Greenhouse Gas Reduction Study to… explore renewable energy projects to offset power requirements of the Project.”


Area AQMD has a threshold of 10,000 MT CO2e per year, and the San Joaquin Valley AQMD guidance states that a project is “less than significant” if GHGs are mitigated to AB 32 levels.

The local 10-mgd Monterey Regional Desalination Project is proposing to use the CARB significance threshold of 7,000 MT/yr as its GHG reduction goal.

5.1.2 California Global Warming Solutions Act (AB 32)

The California Assembly Bill 32: Global Warming Solutions Act (AB 32) sets reduction goals for emitters of GHGs. The AB 32 goal is to reduce statewide GHG emissions to 1990 levels by the year 2020. A facility, such as a power generation site, that directly emits GHGs is considered to produce “Scope 1” direct emissions. A facility or site, such as a home or a water treatment plant, that consumes power and purchases electricity is considered to have “Scope 2” indirect emissions. “Scope 3” indirect emissions refer to GHGs emitted indirectly through the purchase of products that emit GHGs, such as air travel or manufacturing of materials. Compliance with AB 32 is mandatory for Scope 1 emissions, but is voluntary for Scope 2 and Scope 3 emissions. CARB is the agency responsible for achieving AB 32 goals.

Figure 5-1 Categories of GHG Emissions

The scwd2 Desalination Project primarily would be a Scope 2 emitter since the facility would consume energy, although construction of the facility and some purchased materials would have associated Scope 3 emissions. The GHGs associated with the project would be indirect emissions from Pacific Gas and Electric (PG&E). The energy that PG&E produces emits a varying amount of greenhouse gases for every kilowatt-hour produced, depending on the mix of renewable and non-renewable energy sources that supply PG&E. Over time, PG&E anticipates


that their energy portfolio will shift toward more climate neutral and renewable sources. Each year PG&E publishes a certified conversion factor to determine the amount of indirect GHG emissions that are associated with the electrical energy a Scope 2 consumer uses.

5.1.3 California Coastal Commission and the California Coastal Act

Coastal development in California is regulated by the California Coastal Commission (CCC). The construction of the scwd2 Desalination Facililty would require a permit from the CCC, which would include a review of the facility’s proposed energy consumption.

The California Coastal Act regulates coastal development that is within the coastal zone near the ocean or that draws water from the ocean. The Coastal Act encourages coastal facilities “to locate or expand within existing sites” where possible. The Coastal Act describes that “uses of the marine environment shall be carried out in a manner that will sustain the biological productivity of the coastal waters.” Guidance from the CCC in a March 2004 document titled, “Seawater Desalination and the California Coastal Act”, describes that, “energy consumption of new development be minimized.”

While the CCC does not have specific regulatory authority for GHG mitigation, the CCC has put GHG mitigation requirements in permits on a case-by-case basis. For example, the CCC has required the 50-mgd Carlsbad Project to mitigate GHG impacts to a goal of being “net carbon neutral.” Alternatively, the CCC did not require the 0.6 mgd Sand City desalination plant to provide specific GHG reduction or mitigation.

5.1.4 Monterey Bay National Marine Sanctuary

The Monterey Bay National Marine Sanctuary (MBNMS) was established by the National Marine Sanctuaries Protection, Research, and Sanctuaries Act to protect valuable marine resources. MBNMS is part of the National Oceanic and Atmospheric Administration (NOAA). The intake portion of the proposed desalination facility would be located within the MBNMS boundaries. The MBNMS would therefore authorize and/or provide a permit for construction activities associated with the intake that have the potential to disturb the seafloor in the sanctuary. MBNMS guidelines for energy use and greenhouse gas emissions issued in May 2010 state that:

“The project proponent should provide estimates of a facility’s projected annual electricity use and the greenhouse gas emissions resulting from that use. Applicants should also identify measures available to reduce electricity use and related emissions (e.g., energy efficient pumps, low resistance pipes, use of sustainable electricity sources, etc.) and to mitigate for all remaining emissions (e.g., purchase of offsets and/or credits that are consistent with the policies and guidelines of the California Global Warming Solutions Act of 2006 (AB 32), etc.).”

5.2 Projected scwd2 Indirect GHG Emissions

This section summarizes the projections for the SCWD IWP and SqCWD IRP water supply energy use and associated indirect GHG emissions. The projections estimate the energy use for the SCWD and SqCWD to supply water to meet their goals through the implementation of


the IWP and IRP, which includes conservation, curtailment and the operation of the scwd2 Desalination Facility as a supplemental supply.

The projected annual water supply emissions were calculated by multiplying the estimated annual water supply from surface water, groundwater and desalinated water, by the respective energy requirements for each supply. The IWP or IRP overall water supply energy use is then multiplied by an equivalent CO2 (CO2e) emissions factor. The calculations use the 2008 PG&E emission factor of 641.35 lbs CO2e/ MWh.

Based on state regulations and PG&E company goals, it is anticipated that the emission factor will decrease over time as PG&E’s energy portfolio shifts toward increased alternative and renewable energy sources that produce less carbon emissions. However, to be conservative, the calculations have assumed that the emission factor will not change.

The estimated annual indirect GHG emissions for the projected operation of the scwd2 Desalination Facility by the SCWD, during drought year operations, are equivalent to approximately 2,000 metric tons (MT) CO2e.

The estimated annual indirect GHG emissions for the projected operation of the scwd2 Desalination Facility by the SqCWD, during non-drought year operations, are also equivalent to approximately 2,000 metric tons (MT) CO2e.

5.3 Putting Desalination GHG Emissions into Perspective

Similar to the energy of the proposed scwd2 Desalination Facility, the indirect (Scope 2) GHG emissions from the project are relatively small to moderate when compared to other GHG emissions in the Santa Cruz area (City Draft CAP, 2010) and current regulatory guidelines. Those GHG emissions levels include:

CARB preliminary draft significance threshold of 7,000 MT CO2e per year.

City of Santa Cruz, 2008 Commercial/Industrial emissions of 93,000 MT CO2e per year.

City of Santa Cruz, 2008 Transportation emissions of 96,000 MT CO2e per year.

City of Santa Cruz, 2008 Residential emissions of 76,000 MT CO2e per year.

The operation of the scwd2 Desalination Facility by either or both SCWD and SqCWD could produce indirect GHG emissions that range from approximately 2,000 MT/yr CO2e in a normal year, to approximately 3,500 MT CO2e in a drought year. These indirect GHG emissions are equivalent to the emissions from approximately 400 to 700 typical automobiles.

The estimated annual indirect GHG emissions

are equivalent to the emissions from

approximately 400 to 700 typical automobiles.


5.4 Investigating Renewable Energy and GHG Reduction

Options

Even though the indirect GHG emissions from the proposed scwd2 Desalination Facility are relatively small to moderate, the Energy Study will investigate options for renewable energy and GHG mitigation projects to meet the goals of the scwd2 Desalination Program.

The potential renewable energy and GHG mitigation projects will be evaluated for local benefit, technical maturity and reliability, operational impacts, amount of energy produced/saved or GHG emission reductions, and environmental and community impacts. A technical working group (TWG) has been formed to help evaluate mitigation projects.

The top ranking alternatives could then form the elements of the scwd2 Energy Minimization and Greenhouse Gas (GHG) Reduction Plan for the project.

scwd2 will be evaluating additional local solar power opportunities similar to this 127kW system on the Graham Hill WTP.


References

American Council for an Energy-Efficient Economy (ACEEE). “Consumer Guide to Home Energy Savings: Condensed Online Version.” http://www.aceee.org/consumerguide/waterheating.htm. 2007.

California Energy Commission (CEC). “Frequently Asked Questions – FAQs, Energy Efficiency Standards for Televisions.” http://www.energy.ca.gov/appliances/tv_faqs.html updated 3 December 2010.

California Energy Commission (CEC). “Power Plant Fact Sheet.” http://www.energy.ca.gov/sitingcases/FACTSHEET_SUMMARY.PDF updated 7 January 2011.

California Energy Commission. U.S. Per Capita Electricy Use By State in 2009. http://www.energyalmanac.ca.gov/electricity/us_per_capita_electricity.html

California Coastal Commission. Seawater Desalination and the California Coastal Act. March 2004.

City of Santa Cruz. Draft Climate Action Plan. September 2010.

Crisp, Gary. “Perth provides world desalination sustainability model.” Desalination and Water Reuse, Volume 19/No. 3. November/December 2009.

Energy Information Administration (EIA). 2003 Commercial Buildings Energy Consumption Survey: Consumption and Expenditure Tables. Table C14A. http://www.eia.doe.gov/emeu/cbecs/cbecs2003/detailed_tables_2003/detailed_tables_2003.html#consumexpen03

Energy Information Administration. 2005 Residential Energy Consumption Survey: Household Consumption and Expenditure Tables. Table US14. http://www.eia.doe.gov/emeu/recs/recs2005/c&e/detailed_tables2005c&e.html

Energy Information Administration. Dollars Saved per Household for a 1° F Lower Thermostat Setting by Division in the West Census Region, 1997. http://www.eia.doe.gov/emeu/consumptionbriefs/recs/thermostat_settings/table4.pdf

Monterey Bay National Marine Sanctuary and National Marine Fisheries Service (National Oceanic and Atmospheric Administration). Guidelines for Seawater Desalination in the Monterey Bay National Marine Sanctuary. May 2010.

Pacific Gas and Electric Company. “PG&E 2009 Projected Power Mix.” November 2009 Bill Insert.http://www.pge.com/myhome/myaccount/explanationofbill/billinserts/previous/2009/november.shtml

http://www.aceee.org/consumerguide/waterheating.htm

http://www.energy.ca.gov/appliances/tv_faqs.html

http://www.energy.ca.gov/sitingcases/FACTSHEET_SUMMARY.PDF

http://www.energyalmanac.ca.gov/electricity/us_per_capita_electricity.html

http://www.eia.doe.gov/emeu/cbecs/cbecs2003/detailed_tables_2003/detailed_tables_2003.html#consumexpen03

http://www.eia.doe.gov/emeu/cbecs/cbecs2003/detailed_tables_2003/detailed_tables_2003.html#consumexpen03

http://www.eia.doe.gov/emeu/recs/recs2005/c&e/detailed_tables2005c&e.html

http://www.eia.doe.gov/emeu/consumptionbriefs/recs/thermostat_settings/table4.pdf

http://www.pge.com/myhome/myaccount/explanationofbill/billinserts/previous/2009/november.shtml

http://www.pge.com/myhome/myaccount/explanationofbill/billinserts/previous/2009/november.shtml


U.S. Department of Energy (US DOE). “Estimating Appliance and Home Electronic Energy Use.” http://www.energysavers.gov/your_home/appliances/index.cfm/mytopic=10040. 24 March 2009.

Siemens, Vossloh Euro Series Locomotive Engines, http://www.railcolor.net/index.php?nav=1405862&lang=1

Water Desalination Report (WDR), “Energy Priorities.” Volume 44, Issue no. 20. 2 June 2008.

http://www.energysavers.gov/your_home/appliances/index.cfm/mytopic=10040


Appendix A: Units, Conversion Factors, and Calculations

A.1 Units

Power: watts (W), kilowatts (kW)

Energy: watt-hours (W.h), British thermal units (Btu)

Water volume: gallons (gal), kilogallons (kgal), million gallons (MG)

Water flowrate: gallons per day (gpd), million gallons per day (MGD)

A.2 Conversion Factors

Energy (W.h) = Power (W) x Time (h)

1 kW = 1,000 W 1 MW = 1,000 kW = 1 million W 1 GW = 1,000 MW = 1 million kW = 1 billion W

1 kWh = 1,000 W.h 1 MWh = 1,000 kWh = 1 million W

.h 1 GWh = 1,000 MWh = 1 million kWh

1 kWh = 3412.3 Btu

A.3 Calculations

Section 2.2

DATA CENTER

Proposed Microsoft data center power capacity = 198 MW (WDR, 2008)

Annual energy = 198 MW x 24 hours/day x 365 days/year = 1,734,480 MWh per year

Santa Cruz, Cruzio Data Center data center power requirements = 52.5 MWh per year per rack (Cruzio Center Staff, 2011)

Annual energy use = 52.5 MWh/yr per rack x 30 racks = 1,576.8 MWh per year Energy Demand = 1,576.8 MWh per year / 365 days / 24 hrs = 0.18 MW


REFRIGERATION

Annual energy per household for refrigeration in California = 3,700,000 Btu = 1,084 kWh (EIA, 2005)

Total annual household energy use in California = 67,100,000 Btu = 19,664 kWh

1,084 kWh / 19,664 kWh = 5.5% household energy spent on refrigeration

1,084 kWh/household x 50,000 households = 54,200,000 kWh/yr = 54,200 MWh/yr

54,200 MWh/yr / 365d/yr / 24h/d = 6.2 MW

TELEVISION

TV annual energy use in California = 8,772 GWh = 8,772,000,000 kWh (CEC, 2009)

Approximate households in California = 12,100,000

8,772,000,000 kWh / 12,100,000 households = 725 kWh/household annually

725 kWh/household x 50,000 households = 36,250,000 kWh/yr = 36,250 MWh/yr

36,250 MWh/yr / 365d/yr / 24h/d = 4.1 MW

Section 2.3

SCWD

Average energy use per year = 5,504,600 kWh/yr = 5,504 MWh/yr

Average water production per year = 3,992 MG/yr = 3,992,000 kgal/yr

5,504,600 kWh/yr / 3,992,000 kgal/yr = 1.4 kWh/kgal

Average residential water use = 75 gallons/person/day 2.2 people/household (SCWD General Plan) 1.4 kWh/kgal / 1000 gal/1 kgal x 75 gal/person/day = 0.10 kWh/person/day 0.10 kWh/person/day x 365 days/year x 2.2 people/household = 83 kWh/household/year


SqCWD

Estimated annual energy use (2001 – 2005) = 3,765,534 kWh/yr = 3,766 MWh/yr

Average annual water production (2001 – 2005) = 1,760 MG/yr = 1,760,000 kgal/yr

3,765,534 kWh/yr / 1,760,000 kgal/yr = 2.1 kWh/kgal

Average residential water use = 75 gallons/person/day 2.2 people/household (AMBAG) 2.1 kWh/kgal / 1000 gal/1 kgal x 75 gal/person/day = 0.16 kWh/person/day 0.16 kWh/person/day x 365 days/year x 2.2 people/household = 129 kWh/household/year

Section 2.4

Typical California Residential Annual Energy Consumption by End Use

Water Heating Other Appliances & Lighting Heating AC Refrigeration Total

million Btu 23.3 19.7 15.7 4.7 3.7 67.1

kWh 6,828 5,773 4,601 1,377 1,084 19,664

% 35% 29% 23% 7% 6% 100%

Source: EIA, 2005

Section 3.2 Mid Capacity operation = 1.25 MG/day x 365 days/yr x 15 kWh/kgal = 6,844 MWh/yr Capacity = 6,844 MWh/yr x 1 year/8760 hours = 0.8 MW Full operation = 2.5 MG/day x 365 days/yr x 15 kWh/kgal = 13,688 MWh/yr Capacity = 13,688 MWh/yr x 1 year/8760 hours = 1.6 MW

Section 4.1 Mid Capacity operation = 6,844 MWh/yr

HOSPITAL (EIA, 2003)

6,844 MWh/yr / 6,628 MWh/yr = 103%

HOUSEHOLD

6,844,000 kWh/yr / 18,469 kWh/household in SCWD = 371 households

REFRIGERATION


6,844,000 kWh/yr / 1,084 kWh/household = 6,314 households / 50,000 households in Santa Cruz = 13%

TELEVISION

6,844,000 kWh/yr / 725 kWh/household = 9,440 households / 50,000 households in Santa Cruz = 19%

Section 4.2 SCWD

75 gal/person/day x (88% x 1.4 kWh/kgal + 12% x 15 kWh/kgal) x 1kgal/1000 gal = 0.23 kWh/person/day

0.23 kWh/person/day x 365 d/yr x 2.2 people/household = 183 kWh/yr per household

Water

Heating Other Appliances &

Lighting Space Heating Refrigeration

Water Supply

with Desal Total

kWh 6,828 5,773 4,601 1,084 183 18,469

% 37% 31% 25% 6% 1% 100%

SqCWD 75 gal/person/day x (61% x 2.1 kWh/kgal + 39% x 15 kWh/kgal) x 1kgal/1000 gal =

0.53 kWh/person/day

0.53 kWh/person/day x 365 d/yr x 2.2 people/household = 429 kWh/yr per household

Water

Heating Other Appliances

& Lighting Space Heating Refrigeration

Water Supply with Desal

Total

kWh 6,828 5,773 4,601 1,084 429 18,715

% 36% 31% 25% 6% 2.3% 100%

Section 4.3 SCWD LIGHTBULB 35 W x 8 hours/day x 365 days/yr = 110 kWh/yr THERMOSTAT Lowering thermostat by 1

oF during winter months saves 227 kWh/yr (EIA, 1997)

100 kWh/yr x 1

oF / 227 kWh/yr = 0.4

oF

COMPUTER USE Average computer + monitor wattage = 270 W (US DOE, 2009) 270 W x 1 hours/day turned off x 365 days/year = 99 kWh/year saved


WASHING MACHINE USE Average washing machine load (warm wash/cold rinse) = 2 kWh/load (US DOE, 2009)

2 kWh/load x 50 loads/yr = 100 kWh/year

SqCWD LIGHTBULB 35W x 24 hours/day x 365 days/yr = 307 kWh/yr THERMOSTAT Lowering thermostat by 1

oF during winter months saves 227 kWh/yr (EIA, 1997)

300 kWh/yr x 1.1

oF / 227 kWh/yr = 1.3

oF

COMPUTER USE Average computer + monitor wattage = 270 W (US DOE, 2009)

270 x 3 hours/day turned off x 365 days/year = 296 kWh/year saved WASHING MACHINE USE Average washing machine load (warm wash/cold rinse) = 2 kWh/load (US DOE, 2009)

2 kWh/load x 150 loads/yr = 300 kWh/year

Section 5.3

AUTOMOBILE

Typical automobile produces 5 MT of CO2e per year (US DOE, 2009)

2,000 MT/yr / 5 MT/yr per car = 400 cars 3,500 MT/yr / 5 MT/yr per car = 700 cars

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