energy conservation in water and wastewater facilities rev 1 · energy conservation measures in...

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Energy Conservation in Water and Wastewater Facilities

Energy Management and Financing for Municipal Water and Wastewater Utilities

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Energy Conservation in Water and Wastewater Facilities

• Energy and the Life Cycle of Water• Energy Use Intensity, Benchmarking,

Requirements, and Management

• Energy Conservation Measures• The Comprehensive Process Energy Audit• How do I pay for all this?

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Energy and the Life Cycle of Water

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Energy and the Life Cycle of Water

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Why do we focus on wastewater treatment?

• Single largest energy expenditure• Recent developments in technology• Largest opportunities for energy cost savings• Quickest simple paybacks for projects we can

do NOW.

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Energy Management in Water and Wastewater Utilities

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Energy Management Plan

• Plan -> Do -> Check -> Act1. Plan:

1. Choose a Champion2. Establish an Energy Baseline3. Identify Priorities4. Set Goals

2. Do:1. Perform a Comprehensive Process Energy Audit2. Review audit and choose Energy Conservation

Measures for Implementation3. Implement Energy Conservation Measures

Plan

Do

Check

Act

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Energy Management Plan

• Plan -> Do -> Check -> Act3. Check:

1. Monitor key Indicators – Energy and Process Performance

2. Measure and Verify projected Energy Savings3. Identify and address any issues4. Document the results

4. Act1. Evaluate2. Apply lessons learned3. Repeat

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Energy Benchmarking

• What is an Energy Benchmark?• A standard metric for Energy Intensity or EI• kWh or Btu/MG• Establishes a baseline• Comparison to future energy use and to your peers

“You can’t manage what you can’t measure.”

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Energy Intensity

• Energy Intensity is the amount of energy used per volume of treated effluent; kWh/MG

• Water treatment has the highest range of EIs

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Energy Benchmarking

• Wastewater Treatment Plants• Data becoming more widely available

• EPA, Energy Star, WEF, AWWARF, CEC

• Water Treatment Plants• Benchmarking Data Relatively Scarce

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Energy Benchmarking

• How do I establish a benchmark?• Energy Star Portfolio Manager

• The Good: Comprehensive, accounts for Source and Site Energy, takes several different treatment processes into account

• The Bad: • Complicated • Time consuming • Finicky

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Energy Benchmarking

• Eaton’s Simple Benchmarking Tool• Based on the Energy Star Technical Rating

Methodology• A range of all secondary WWTP plants with nutrient

removal

Where does your facility stand?

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Source Energy Use Per Flow

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Energy Benchmarking Case Studies

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Illinois WWTP Case Study

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Energy Management Plan

• Plan -> Do -> Check -> Act1. Plan:

1. Choose a Champion2. Establish an Energy Baseline3. Identify Priorities4. Set Goals

2. Do:1. Perform a Comprehensive Process Energy Audit2. Review audit and choose Energy Conservation

Measures for Implementation3. Implement Energy Conservation Measures

Plan

Do

Check

Act

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Comprehensive Process Energy Audit

• A comprehensive audit includes all buildings and processes:1. Establish a detailed Energy Baseline2. Include a detailed equipment inventory3. Create an Energy Use Disaggregation4. Correlate Energy and Process Data5. Determine O&M costs for existing equipment6. Make Recommendations for Energy Conservation

Measures (ECMs)

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Energy Use Disaggregation

• A disaggregation is an energy baseline broken down by equipment

• A way to benchmark each process to look for inefficiencies

• Compare to plants of similar size, or theoretical energy requirements

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WEF Energy Requirements

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Correlate Energy and Process Data

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Measurement and Verification

• Plan -> Do -> Check -> Act3. Check:

1. Monitor key Indicators – Energy and Process Performance

2. Measure and Verify projected Energy Savings3. Identify and address any issues4. Document the results

4. Act1. Evaluate2. Apply lessons learned3. Repeat

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Measurement and Verification

• Monthly comparative review of utility bills• High Level • Basis for energy savings guarantees (ESPC)

• Individual Process Metering• Detailed System Performance• Energy Use, Power Quality, THD• Logging, Trending, Benchmarking

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Energy Conservation Measures in Wastewater Treatment

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Energy Conservation Measures in Wastewater Treatment

• Low-Cost/No Cost Measures• Capital Measures

• Lighting • HVAC• Pumping Systems• Aeration Systems and Blowers• SCADA Systems and Controls

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Low-Cost/No Cost ECMs

• Effective use of existing controls• Timers• Differential Water Devices• Thermostats• Pump staging and sequencing• ORP Control• Dissolved Oxygen Control

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Energy Conservation Measures in Wastewater Treatment

• Lighting and HVAC typically make up about 7% of a wastewater facilities energy usage

• Lighting Measures• High Efficiency Lighting Upgrades• T8, T5, Compact fluorescent, LED• Lighting Controls

• Photocells• Timers• Occupancy Sensors• Integration to BAS

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Energy Conservation Measures in Wastewater Treatment

• HVAC Measures • Anything from programmable thermostats to

building automation systems• Temperature and night setbacks• High Efficiency equipment• Premium Efficiency motors• Exhaust Air Heat Recovery• Heating and cooling system upgrades• Digester Gas Utilization

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Energy Conservation Measures in Wastewater Treatment

• Headworks• Bar Screen Units

• Optimize schedule for mechanically cleaned units

• Influent Pumping• Can represent 15% to 70% of electrical energy use

depending on

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Energy Conservation Measures in Wastewater Treatment

• Pumping Systems make up about 12% of facility energy use• Premium Efficiency Motors• Reducing Flow Rates• Variable Speed Pumping

• Deposition of sediment can take place where flow rates are too low

• Minimizing head loss due to restrictions• Buildup in chemical feed systems• Clogging in wastewater lift stations

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Energy Conservation Measures in Wastewater Treatment

• Aeration Systems make up about 60% of facility energy use• Most commonly 60%, as high as 76%• Greatest opportunity for energy savings at a typical

WWTP• Most critical component to meeting permit

requirements

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Aeration Systems

• History:• Energy Crisis of the 1970’s caused the industry to

reevaluate the technologies and equipment used in wastewater treatment

• New technologies were introduced to improve aeration systems

• Recent developments in technology have allowed great leaps in overall efficiency

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Aeration Systems

• Diffusers• Coarse bubble diffusers have almost all been

replaced with fine pore diffusers, and work well in systems that require mixing and have low DO requirements.

• Rubber membrane diffusers are common due to cost

• High diffuser flux rate (variance in amount of air transferred per area of diffuser) – not the highest OTE

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Aeration Systems

• Diffusers• Fine-pore Ceramic Disc

• Lower diffuser flux rate, better OTE than porous membrane

• Higher Cost• Higher maintenance, often need to be removed to be

cleaned• Reduced energy consumption• Ultra fine pore diffusers are emerging on the market with

high SOTE and low flux

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Aeration Systems

• Blowers• Most significant improvements in technology• Two common types of blowers, Positive

Displacement (PD), and Multi Stage CentrifugalPD Blowers• Fixed volume of air per

revolution regardless of pressure

MSC Blowers• Variable volume of air over a

small operational pressure range

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Aeration Systems

• How much does aeration cost?

= $273,528

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Aeration Systems

• High Speed Turbo Blowers• Recently became

available in the US as of 2005

• Off the shelf wire-to-water water efficiency improvement of 25%

• Up to 60% quieter than PD or MSC

Courtesy of HSI

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Aeration Systems

• High Speed Turbo Blowers• Air or magnetic bearings require no lubrication• Low maintenance, regular air filter changes• Operates of a large range of pressures and volumes at high efficiency

Courtesy of HSI

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SCADA Systems and Controls

• Automated Dissolved Oxygen Control• Combined with HST equipment upgrades, aeration

savings of 50% are achievable• Poorly controlled equipment can be as inefficient as

poor equipment• Improvements in DO sensing technology have

reduced maintenance events for sensors to once per year per sensor

• Self cleaning, self calibrating

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Aeration Systems

• Case Studies• Green Bay Metropolitan Sewerage District, De Pere

facility, De Pere WI. 14.2MGD• 6x330hp HST blowers replaced 5x450hp MSC• 50% Electrical Energy Savings, 38% Cost Reduction

• Lake County Department of Utilities, Vernon Hills WWTP, Libertyville, IL 6.0MGD

• Aeration System Control Upgrades• 44%* Electrical Energy Savings, 39%* Cost Reduction

*Projected

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Financing Energy Projects

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Financing Energy Projects

• Utility Rebates• LED Lighting, HVAC, VFDs, custom measures

• Traditional financing• Revenue bonds, lease purchase agreements

• Energy Savings Performance Contracts (ESPC)• No up front capital costs• Utilize guaranteed energy savings as leverage for

financing, given cash flow can support• ESCO assumes the risk

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