The City of San DiegoThe City of San Diego

Metropolitan Wastewater Metropolitan Wastewater Department’sDepartment’s

Sustainable Energy Sustainable Energy Management Using In-House Management Using In-House

ResourcesResources

The City of San Diego MWWDThe City of San Diego MWWD

• Serves 2.2 million Serves 2.2 million peoplepeople

• Treats an average Treats an average of 180 MGDof 180 MGD

• Has a peak flow of Has a peak flow of 477 MGD477 MGD

• Operates four Operates four Treatment Plants Treatment Plants and 90 Pump and 90 Pump StationsStations

Treats Wastewater for 15 CitiesTreats Wastewater for 15 Cities

Metropolitan Metropolitan Wastewater Wastewater SystemSystemExisting & Planned Existing & Planned FacilitiesFacilities

The Facilities Consist of:The Facilities Consist of:• One 240 MGD Advanced One 240 MGD Advanced

Primary WWTPPrimary WWTP

• Two Water Reclamation Two Water Reclamation Plants (30 & 15 MGD)Plants (30 & 15 MGD)

• One 150 DTD Biosolids One 150 DTD Biosolids Processing FacilityProcessing Facility

• And, Pump Stations with And, Pump Stations with Pumps fromPumps from3 HP to 2250 HP3 HP to 2250 HP

Renewable EnergyRenewable Energy• In 2006 the City of San In 2006 the City of San

Diego consumed more Diego consumed more renewable energy than renewable energy than any other agency in the any other agency in the U.S. (Average: 7.2 MW)U.S. (Average: 7.2 MW)

• MWWD consumes 96% MWWD consumes 96% of that green energyof that green energy

• MWWD currently MWWD currently produces or causes to produces or causes to produce more than produce more than twice than is consumes twice than is consumes (16.6 MW + 3.9 MW)(16.6 MW + 3.9 MW)

Point Loma Wastewater Treatment Point Loma Wastewater Treatment PlantPlant

4.53 MW DIGESTER GAS BASE 4.53 MW DIGESTER GAS BASE + 1.2 MW PEAKING+ 1.2 MW PEAKING

1.35 MW HYDRO 1.35 MW HYDRO

DIGESTERSDIGESTERS FLARESFLARES

PRIVATIZED BUDG 300 KW PRIVATIZED BUDG 300 KW FUEL CELL + 3.6 MW FUEL FUEL CELL + 3.6 MW FUEL

CELLS OFFSITE (BOC)CELLS OFFSITE (BOC)

PLWTP Hydroelectric PLWTP Hydroelectric GeneratorGenerator

Duel FuelDuel FuelA

ENGINE

AIRCLEANER

DIGESTERGAS

POWER

FUEL/AIRMIXER

TURBOCHARGER

DIESELFUEL

FUELINJECTION

GENERATOR

LFG & Digester GasLFG & Digester Gas

Landfill Gas WellLandfill Gas Well

MBC COGENMBC COGEN6.4 MW PRIVATIZED6.4 MW PRIVATIZED

COGENERATION FACILITYCOGENERATION FACILITY(MINNESOTA METHANE)(MINNESOTA METHANE)

Cogen System SchematicCogen System Schematic

NCWRP NCCFNCWRP NCCF3.8 MW PRIVATIZED3.8 MW PRIVATIZED

(MINNESOTA METHANE)(MINNESOTA METHANE)

MWWD 30kW Photovoltaic System at MWWD 30kW Photovoltaic System at MOC IIIMOC III

• 30 kW rooftop system at MOC III

• Under directive from Metro Commission, innovative rooftop mounting system and semiconductor technology were chosen

Solar Cadmium TellurideSolar Cadmium Telluride• Use of the First Solar’s cadmium telluride thin film Use of the First Solar’s cadmium telluride thin film

collectors helps to push the Photovoltaic Industry’s collectors helps to push the Photovoltaic Industry’s development by using new Mass Produced development by using new Mass Produced Technologies for PV cells that have a strong Technologies for PV cells that have a strong potential of obtaining SIGIFICANTLY LOWER COSTS potential of obtaining SIGIFICANTLY LOWER COSTS PER WATT INSTALLED in the near future.PER WATT INSTALLED in the near future.

• This installation also utilized new mass producedThis installation also utilized new mass producedPVC flat ballast mounted roof racks.PVC flat ballast mounted roof racks.

• Other Benefits Include:Other Benefits Include:Better performance on cloudy daysBetter performance on cloudy daysAnd may include: Lower performanceAnd may include: Lower performancelost over the life of the collectorlost over the life of the collector

Energy Produced per Rated kW Energy Produced per Rated kW per Day – August 2003per Day – August 2003

MOC IIIMiramarRidgehaven

0

2

4

6

8

8/1/

03

8/6/

03

8/11

/03

8/16

/03

8/21

/03

8/26

/03

8/31

/03

Date

kWh p

er

rate

d k

W p

er

Day

20% Higher Average Production/Rated kW

CdTe vs. Si

BUDGBUDGBOC/Linde BOC/Linde System System DiagramDiagram

Point Loma BUDG Purification SystemPoint Loma BUDG Purification System

Point LomaPoint Loma

3 Off-site Fuel Cells, 1.2 MW’s each

Blower Sulfur Removal

Drying, Chilling,Purification beds

2-StageCompressor

MembraneCO2 Removal

3-StageCompressor

Fuel CellFuel Cell

CNGCNG

EnclosedCO2 Flare

Point Loma BUDG SchematicPoint Loma BUDG Schematic

CompressedCompressedDigester GasDigester Gas

to Truckto Truck 3-Stage HP3-Stage HPCompressorCompressor

Feed fromFeed fromPLWTP GasPLWTP Gas

SystemSystem

FlareFlare

0 psig0 psig5 psig5 psig 0 psig0 psig

165 psig165 psig

BlowerBlower

Pre-PSADryer

Refrigeration

Pressure SwingAbsorption(PSA) Dryer

2-Stage2-StageCompressorCompressor

Pre-GranularActivatedCarbon

Refrigeration

GranularActivated

Carbon Filter

Pre-Membrane

Heater

150 psig150 psig

140 psig140 psig2600 psig2600 psig

C02 RemovalMembrane

Unit

Condensate Return to Wastewater Plant

C0C022

C0C022

SulfurRemoval

Fuel CellFuel Cell

Energy EngineeringEnergy Engineering

• Develop and manages power production projectsDevelop and manages power production projects

• Reviews new designs and obtains grants for energy Reviews new designs and obtains grants for energy efficiencyefficiency

• Fostered the writing of theFostered the writing of theDepartment’s energy planDepartment’s energy plan

• Leads the energy audit teamLeads the energy audit team

• Takes the lead on theTakes the lead on theimplementation on non-implementation on non-operational energy projectsoperational energy projects

• Track Department’s energyTrack Department’s energydatadata

MWWD Energy SectionMWWD Energy Section

Point Loma Hydro

Energy AuditsEnergy Audits

• Engineering, O&M Engineering, O&M and interested othersand interested others

• Trained with CEC Trained with CEC GrantGrant

• Three to four audit Three to four audit reports per yearreports per year

• 19 reports completed19 reports completed

NRG AUDITSNRG AUDITS• 169 potential improvements169 potential improvements

• 44 improvements implemented44 improvements implemented

• 20 in progress20 in progress

• 93 pending proposals/93 pending proposals/additional analysisadditional analysis

Examples:Examples: Turn off 800hp back up blowerTurn off 800hp back up blower Program to eliminate air gap system - 1 Program to eliminate air gap system - 1

pump station completedpump station completed Automate and raise large pump station Automate and raise large pump station

wet well set pointwet well set point VFD on 60hp ventilation fanVFD on 60hp ventilation fan LightingLighting VFD on cooling water pumpsVFD on cooling water pumps

Coming AttractionsComing Attractions• 900 KW expansion of the NCCF900 KW expansion of the NCCF

• 6.3 MW of peaking emergency generation for free6.3 MW of peaking emergency generation for freegenerator maintenancegenerator maintenance

• 1 MW Photovoltaic System1 MW Photovoltaic System

• NEW Department AnnualNEW Department AnnualEnergy Conservation BudgetEnergy Conservation Budgetwith performance guidelineswith performance guidelines

• Energy audit suggestionsEnergy audit suggestionsimplemented through Non-implemented through Non-Profit contractor with EnergyProfit contractor with EnergyIncentives from utilityIncentives from utility

• Automated flow pace control of PLWTP HydroAutomated flow pace control of PLWTP Hydro