Energy Efficiency Strategies for Municipal Wastewater Treatment ...
RCAC Energy Efficiency for Water and Wastewater Systems.
Transcript of RCAC Energy Efficiency for Water and Wastewater Systems.
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Energy Efficiency for Water and Wastewater Systems
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WelcomeWelcome
Trainer:Jake Salcone
RCAC – Portland, ORRural Development Specialist – Environmental
Event:Washington D.C. RCAP conference
December 2010
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Why Energy Efficiency?
Some 4% of the nation’s electricity use goes towards moving (80%) and treating water/wastewater*
Electricity costs are increasing rapidly; efficiency is cheaper in the long-run
Funding programs have increasing preference for “green” projects
Efficiency can extend life of assets Less energy means lesser demand for power – ALL
power generation has an environmental impact
*Water and Sustainability: U.S. Electricity Consumption for Water Supply & Treatment—TheNext Half Century, EPRI, Palo Alto, CA: 2000. 1006787.
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The Problem:
Water weighs 8.34 lbs/gallon. We use ~60 gallons/day, which means we move 500 lbs of water miles and miles, for every individual, everyday.
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The Problem:
1 MGD plant moves about 4,120 tons of water each day
Plants commonly designed to handle max capacity not operate at lowest cost
Many new technologies in motors, HVAC, and lighting have not been adopted in water and wastewater systems
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Power Costs and Power Prices
Utility power cost includes:Maintenance and operation of power delivery
infrastructure – transmission and distributionCost of powerCapacity for peak demand
Billing rates or tariff structures often aimed at discouraging peak demand
“Small Industrial” customers should evaluate electricity requirements versus billing structure
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Energy Audit
Range from simple walk-through to detailed engineering and return-on-investment analysis
Level of detail depends on goals TAP vs. Utility Representative Steps:
Identify Quantify Verify
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Where is the energy going?
Pumping Aeration
According to the Consortium for Energy Efficiency (CEE), aeration typically accounts for the largest share of energy consumption, 60% at an activated sludge WWTP.
Dewatering U.V. Lighting HVAC Odor Control
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Categorical Efficiencies
Any water conservation measure is an energy conservation measure
I&I reduction is an efficiency measure Basic systems use less energy
Energy Consumption of secondary
treatment
*Energy Audit Manual for Water/Wastewater Facilities; EPRI 1994
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Energy Audit: Data Collection
Plant Flows Electric Bills and Billing Schedule Design Summary Equipment Inventory Pumping records and performance curves Operating times for pumps and other processes Plant management and operations strategies Previous energy audits
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General Guidelines for Finding Efficiency Opportunities
Does the process/equipment need to run at all? Find loads that run continuously or nearly
continuous - Is it possible to run the process/equipment for fewer hours?
Look at your electrical diagram and pick out big motors
Look at equipment more than 10 years old
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Tune-Ups vs. Capital Projects
Is the process efficient at most common load conditions, or does equipment need modified or replaced? e.g. Run more efficient pumps for normal base loads
and use lower-efficiency, larger units for only peak flows
Systems that are run on simple or no control – Can controls be added/improved?
Evaluate tune-up savings vs. new equipment savings
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Example Energy Conservation Measures (ECMs)
Motor/pump output optimization System-wide optimized pumping strategies System-wide pressure management
strategies Metering/Billing/Rate Leak/I&I detection and repair technologies
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Pumping
Pumps should be selected for maximum efficiency at average flow, not maximum capacity. Multiple pumps can meet peak demand Use your most efficient equipment first and most often Swap out old motors rather than rewinding Check that your pump impellers are correct for actual conditions
Compare Variable Frequency Drives to cycling pumps on and off
*High Efficiency motors will eventually become standard, so get your incentives now!
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Pumping Cont.
System Pressure: Upsize sewer force main or water main size. Allow pump station basins to fill higher before
pumping to reduce head Replace lift-station with gravity sewer
*Most process pumps are fairly low head, so 2 or 3 feet of pressure difference can be a good percentage of total head.
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Aeration
Aeration systems are huge consumers – up to 60% of total plant demand!
Switch to fine bubble diffusers – 30% + reduction over coarse air
Install active DO control, or utilize what you already have Upgrade to modern blowers with efficient turn down
capability Use cascaded control strategies Are you nitrifying? Do you need to?
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Fine-Bubble Aeration
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Other Energy Loss
Dewatering Centrifuge uses ~ 6 x more horsepower than belt filter or
screw-press
U.V. Low-pressure, high efficiency lamps more efficient than
medium pressure lamps Match number of lamps to flow
Lighting T5 lamps, motion sensors
HVAC Seal-tight, ventilate right Use waste-heat from motors, generators, etc. Heat pumps
on effluent
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Energy Efficiency Incentive Programs
Why do electric utilities want you to SAVE energy?
Transmission constraints Conservation cheaper than generation Regulatory pressure
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Energy Efficiency Incentive Programs
How do these programs work? 1. Water or wastewater utility contacts their electrical utility to ask
for specific program details, and which program components apply to them.
2. A program representative conducts an energy audit or facilities plan analysis and determines which program components the facility can take advantage of.
3. As projects are completed, a program representative will perform measurements and verify savings.
4. The utility pays the industrial facility an incentive check based on the savings.
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Energy Efficiency Incentive Programs
Example Incentives: Oregon Bonneville Power Administration
Via rural electric co-ops $.25/kWh of annual savings Up to 70% of total project costs Energy management services
Energy Trust of Oregon $.32/kWh of annual savings Up to 50% of project costs
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Energy Efficiency: Incentive Example
Example Savings: BPA Incentive $.25 per kWh saved, based on first
year’s energy consumption.This is about $1600 per horsepower
on a 24/7 basis.Reducing pull on an aeration system
from 45 hp to 35 hp has a potential incentive of roughly $16,000 annually.
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Energy Efficiency Incentive Programs
How do I find incentives in my region?Contact your electric service providerEfficiency programs often handled by consultant
group, not utility directlyDatabase for State Incentives for Renewables
and Efficiency (DSIRE) http://www.dsireusa.org/
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More Efficiency Incentives
What about Tax Credits? Municipalities and Non-profit Districts don’t pay
taxesPrivate ‘pass-through partner’ may be recipient,
particularly with big renewable energy projects
University Extensions: Audits and Grants
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But wait, there’s more!
Ongoing energy savings for life of the measure. Often reduced maintenance cost from turning
off or turning down equipment. Aesthetic and comfort improvements – e.g.
better lighting, better HVAC.
Conservation: The gift that keeps on giving!
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Long-Term Savings
*Water & Wastewater Systems Optimization & Energy Management Technologies: BacGen Overview Brief . Northwest Energy Efficiency Alliance, 2007.
Energy Efficiency Technical Assistance
New Project No New Project
Design Complete Still Thinking Requests energy
efficiency TADoes not request
energy efficiency TA
Does design reflect most
energy efficient solution?
Yes. Train on appropriate renewable
technologies and incentives
Encourage board to include
‘energy demand’ in
project selection criteria
Help board determine most
appropriate efficiency
measures and payback period
Contact local utility for
energy audit, or perform your own
Incorporate training on energy demands, costs, and potential
benefits to efficiency measures
No. Contact electric utility to evaluate design,
potential for energy savings and incentives
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Renewable Energy Opportunities
Solar Wind Hydro Biogas Heat pump
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Solar
Photovoltaic cells about 10% efficient, but “fuel” is free
“Tracking” systems much more efficient than fixed systems, but roof space is wasted space, so it might not matter
4 acres of tracking panels = 1MW Payback best where electricity is at least
$.10/kWh
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Wind
Small systems exist Payback best where electricity is at least
$.10/kWh 20 year payback common
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Micro-Hydro
Low-head and High-head systems available Relatively small footprint Micro-hydro opportunities on source water
intakes and effluent outfalls
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Digester Biogas
Can add algae or FOG to generate more methane
May qualify for Carbon Credits Cogenerators simple and common Fuel Cells
Most efficient; generate DC power 24/7; Minimal O&M Robust incentives Must condition fuel to remove Hydrogen Sulfide –
expensive on small scale Only viable above ~10 MGD
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Fuel Cell
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Heat Pumps
Capture heat from air, digesters or effluent Cheap energy
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Greywater and Effluent Reuse
Greywater Benefits Lower fresh water use Decreased water burden
to WWTP Dry season landscape
watering Potential groundwater
recharge Effluent is potential
revenue
Greywater Obstacles Permitting - Regulations
vary by state Diaper washing causes
contamination concerns Potential decreased
contribution to river flow High capital costs for
greywater systems
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Compost
Biosolids as Soil AmendmentClass ‘B’ worth up to $35/tonClass ‘A’ up to $30/yard
Can be expensive to make. Often must add bark, sawdust, sand, etc.
But may save considerably on landfill disposal fees
Must do more than meet standards – must make a marketable project
TAGRO:
http://www.cityoftacoma.org/page.aspx?nid=306
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Resources
http://www.energy.ca.gov/process/water/eff_water.html
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Resources
Database for State Incentives for Renewables and Efficiency (DSIRE) http://www.dsireusa.org/
RCAC Green Infrastructure Guide:http://www.rcac.org/assets/green_infra/gig.pdf
Thanks for listening about energy efficiency and renewables!