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.

Proposed Project will be Net Carbon Neutral

In February 2012, the Santa Cruz City Council and Soquel Creek Water District Board of Directors both unanimously approved staff’s recommendation that the project be designed and operated with no net increase with regards to indirect greenhouse gases. 

This voluntary commitment is an important step in the agencies’ pursuit for a needed, reliable water supply.    Projects that could be implemented with the water supply project may include  on-site design features such as solar panels, energy efficiency pumps and recovery devices, and green building features to reduce the energy requirements.      

The City of Santa Cruz and Soquel Creek Water District have embarked on an Energy Minimization and Greenhouse Gas Reduction Study (Energy Study) to thoroughly evaluate energy and indirect greenhouse gases associated with proposed desalination project.  A technical working group, including local professionals, experts and practitioners in the water and energy fields, helped develop a list of potential projects and programs to reduce the proposed project’s carbon footprint.

 

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 scwd2 is 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 includes:

  • Current GHG regulatory guidelines
  • Calculattion of  estimated indirect GHG emissions from the Project
  • Comparison of Project emissions with potential baseline GHG goals to determine the amount of GHGs that could be reduced
  • Identifying  renewable energy and GHG reduction options

This study is being overseen by a Technical Working Group.

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.

 

Community Meeting on Energy, GHGs and Desalination

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

 

 

 

 

 

 

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