Energy and Greenhouse Gas Emissions

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 project and scwd² is committed to thoroughly studying the potential energy use and greenhouse gas impacts related to desalination.

Key Issues:

scwd² is conducting an Energy Minimization and Greenhouse Gas Study that is expected to be complete in Fall 2011. This study will engage a Technical Working Group for oversight, input, and guidance. For Status Updates, click here.
The City and District are evaluating a range of GHG reduction goals including, but not limited to, how to make the project no net increase (net-carbon neutral).
GHGs are not emitted from the desal process; they are from purchased power (such as PG&E.)
The household energy equivalents to operating the proposed desal project is 1-3 loads of washing clothes a week or leaving a desktop computer on 1-3 hours per day.
The energy to operate the proposed desal project is comparable to a mid-size hospital (such as Dominican)
The indirect GHGs for the proposed project is equivalent to 400-700 automobiles.
A White Paper on Energy is now available. Click here to access.

Electricity Needs for Proposed Project

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. During proposed typical uses:

For a 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.
For a drought year, the facility is expected to operate at full capacity for half the year (May-October) and thereby require approximately 0.8 MW or about 6,800 MWh annually.

To put this energy requirement into perspective, the desalination project requires about the same amount of energy as 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.

City of Santa Cruz	Soquel Creek Water District

The percentage of household energy for water supply from SCWD with supplemental desalination would be 1 percent of overall household energy usage.	The percentage of household energy for water supply from SqCWD with supplemental desalination would be 2.3 percent of overall household energy usage.

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.

Equivalent Comparisons for Energy associated with the Proposed Project

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 equivalent to:

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.
The energy saved by turning down the thermostat by about 1 or 2 oF in winter heating months.

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.

scwd2 Energy Minimization and Greenhouse Gas (GHG) Reduction Study

The energy requirement of seawater desalination is among the key issues in the evaluation of the proposed Project, and scwd²is committed to thoroughly studying the potential energy use of the Project. 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
Identify renewable energy and GHG reductionoptions
Prepare an Energy Minimization and Greenhouse Gas (GHG) Reduction Plan to meet the goals of the scwd² program

This study is being overseen by a Technical Working Group and the Report is expected to be complete in Fall 2011.

Status Reports on the Energy Study

Desalination and Greenhouse Gas Emissions

The desalination process does not directly emit greenhouse gases like a power plant. The emissions are attributed to the powered purchase required, just as a home or business. The City and District are actively evaluating a range of GHG reduction goals including, but not limited to, how to make the project no net increase (net-carbon neutral). TWG will be assisting with identifying opportunities and projects to reduce the carbon footprint associated with desalination.

The Technical Working Group reviewed over 45 potential projects to further evaluate in the scwd2 Energy Plan that could reduce energy and greenhouse (GHG) emissions for the proposed desalination project. The 16 projects recommended by the Technical Working Group and approved by the scwd² Task Force include the following:

The criteria that these projects will be evaluated for include local benefit, amount of energy produced or mitigated, technical maturity and reliability, operational complexity, environmental/community/sustainability impacts, and cost/cost effectiveness.

Review of these 16 projects is anticipated to occur in September/October 2011.

Upcoming Community Meeting on Energy, GHGs and Desalination

scwd² will be hosting a community wide meeting to share information about the Energy Study. The meeting will be held December 8, 2011 at Live Oak School. For more information, click here.