Upload
phamtu
View
215
Download
0
Embed Size (px)
Citation preview
1
One Year of Energy Net-Zero Via Energy Efficiency and FOG Codigestion
at the Gresham, OR WWTP
Jeff Maag, Project Manager, Wastewater Services Division, City of GreshamJeff McCormick, Project Manager, Carollo Engineers
City of Gresham WWTP
Gresham’s Wastewater Treatment Plant
114,000 service population 13 mgd annual average flow
Secondary, Activated Sludge, Anaerobic Digestion Discharge to Columbia River Contract Operator: 17 FTE in Operations & Maintenance
(Veolia Water) 3 FTE in WWTP and PS Engineering (City of Gresham) One of a handful of Energy Net-Zero WWTP’s in the U.S. Energy Net Zero: producing more energy than consumed
City of Gresham WWTP 2
3
New era of energy production began in 2005 with modern 400 kw Cogen No. 1
City of Gresham WWTP
Two 1 million gallon Anaerobic Digesters at WWTP Digesters treat solids in absence of air – biogas is
produced (65% methane, 35% CO2) Cogen burns biogas to produce electricity and hot water
CAT Model G3508LE
4
Cogen 1 Has Been Very Successful
93% Runtime since 2005 (off about 48 hours per month) Produces power and heats buildings with jacket water heat 55% of WWTP Power needs $250,000 annual avoided electrical costs 2.1 cents per kwh operation/maintenance expenses 3.5 year payback
City of Gresham WWTP
5
Several major developments in 2008 and 2009 on our path to energy net-zero
ACWA / Energy Trust “Energy Independence Project” studied 2 plants in Oregon, including the Gresham WWTP
Gresham City Council passed a Sustainability Policy Kicked off feasibility study of FOG Receiving Station and Cogen
Expansion Solar Array became operational
City of Gresham WWTP
Energy Independence ProjectEnergy Independence ProjectA Project for
Oregon Association of Clean Water Agencies and
The Energy Trust of Oregon
Prepared by Kennedy/Jenks ConsultantsJune 2008
Energy Independence Project
General Recommendations
▼ Do Energy Efficiency First!l Most cost-effective optionl An energy audit can help identify cost-effective
Energy Efficiency Measuresl Install identified EEMs and seek funding $
▼ Resource Optionsl Cogen engines are the most cost-effective for
producing renewable energyl Investigate a FOG Receiving program to enhance
digester biogas production and energy possibilities
8
Gresham’s Sustainability PolicyKey Goals (2009)
1) 80% Reduction in City Greenhouse Gas Emissions by 2050
2) 100% Renewable Energy by 2030
3) Zero Waste in City Operations by 2020
4) Ongoing Protection of Natural Resources (including water quality and availability, and habitat)
5) Toxin Reduction and Eventual Elimination
WWTP had large potential to contribute towards goal 1 and 2.
City of Gresham WWTP
9
FOG Feasibility Study Highlights
$40,000 Grant from State Economic Development Dept. Adding FOG Receiving Facilities is Economically Viable There is a market for this service in our area An additional 400 kw Cogenerator is economically viable FOG Tipping Fee of at least 3 cents per gallon required Need 7,000 to 11,000 gpd of FOG Estimated cost of $3.7 million Leverage $1.5 million in potential grants Simple payback of 7 years
City of Gresham WWTP
10
420 kw Solar Array installed 2009 Installation Dec. 2009 420 kW peak capacity Provides 7% of WWTP power 1+ acre ground-mounted system Power Purchase Agreement with
SunEdison in July 2009 PGE net metering agreement No capital cost to City kwh charge 2/3 PGE rate Fixed annual escalation of 3%
City of Gresham WWTP
11
2010 Energy Management Team
City of Gresham WWTP
Set Goal for Energy Net-Zero WWTP by 2015 Selected Energy Team Members (Team Leader, Ops
Manager, engineering, Maintenance Manager) Meet Monthly for 1 hour and talk only energy Develop Energy Management Plan (keep it simple) Update and discuss Monthly energy production and
consumption numbers every month Select, prioritize and evaluate projects Stay on track! Keep running agenda in Energy Management Plan
2011 Master Plan included continued study of “Energy Independence”
12
FOG Receiving / Cogen Expansion and “Energy Independence” was included in our master planning process
City of Gresham WWTP
13
New high efficiency Neuros blowers and
aerationdiffusers replaced aging equipment
City of Gresham WWTP
Linear Motion Mixer
Aging digester gas mixing was replaced by Linear Motion Mixers
Energy Conservation Project, 2012 - 16%Energy study funded by Energy Trust
14
Replace aging, out of date blowers with
modern efficient blowers
Replace 2 Hoffman mutistage blowers (100 hpeach)
Install 2 Neuros Turbo blowers (100 hp each) Operating curves are much more efficient 50% variable speed turndown Air bearings
City of Gresham WWTP
Linear Motion Digester Mixers
City of Gresham WWTP16
Replace aging biogas mixing system (3 - 40 hpcompressors)
Install Linear Motion Mixers (LMM) for both digesters
Each LMM has 20 hp motor and VFD
Currently operating at 75% speed and 5 hp.
Essentially trading 80 hp 24 hrs/day for 10 hp 24 hrs/day
17
Linear Motion Mixer (Inside Digester)
HydroDisk Diameter 8 feetTravel (up and down) 20 inches30 cycles/minute
City of Gresham WWTP
18
FOG Receiving Station, Phase 1, 2012
10,000 gallon FOG Receiving Tank FOG Grinder, FOG Unload/Tank Mixing Pump and FOG
Feed Pump FOG Heat Exchanger using Cogen Hot Water Loop
City of Gresham WWTP
FOG Receiving Station, Phase 1, 2012
19
Advertised RFP for FOG Haulers 3 FOG Haulers Contracted – must be Preferred Pumpers 8 cent per gallon tipping fee 7,500 gpd received during phase 1 – small tank difficult to
operate effectively
City of Gresham WWTP
20
Energy Net-Zero Project, Phase 2AFOG Receiving Station Expansion, 2014
Added 20,000 gallon receiving tank 30,000 gallon total capacity as of April, 2014 Major Increase in Biogas Production, now receiving
12,000 gpd, $300,000 in tip fees in 2015City of Gresham WWTP
Energy Net-Zero Project, Phase 2B:400 kw Cogeneration Expansion
21
The flared biogas to be utilized in additional 400 kw Cogenerator 2
$2.8 million design and construction $1.4 million in grants Completed January, 2015
City of Gresham WWTP
Energy Net-Zero Project, Phase 2B400 kW Cogeneration Expansion
City of Gresham WWTP 22
COGEN 1 COGEN 2
Energy Building ?
23
Biogas Production Trends
2014 Gas production up 60%+ from baseline Produced more energy than we consumed in 2015 Flared 20% of biogas production in 2015 (Future project?)
City of Gresham WWTP
0
2,000
4,000
6,000
8,000
10,000
12,000
0
50,000
100,000
150,000
200,000
250,000
300,000
350,000
2010 2011 2012 2013 2014 2015
Biogas (SCF/day) and FOG Injection (Gal/day)
Biogas FOG
FOG Phase 1
FOG Phase 2A
Cogen 2 Phase 2B
25
Biogas Scrubber Media Largest Cost of the treatment system H2S Iron Sponge Media replaced every 60-120 days H2S media changed when treated biogas > 100 ppm Siloxane media Changed every year (switch tanks 6
months) 1 per year siloxanes testing, unreliable and expensive Storage required for media so it is ready to go Change cogen oil (if needed) when media is replaced for
½ day outage. $10,000 per H2S Media Changeout (3 per year) $6,600 per Siloxane Media Changeout (1 per year) About $0.01 per kWh O&M cost
City of Gresham WWTP
March 2015 – first net zero month
City of Gresham WWTP 26
NET-IMPORT
NET-EXPORT
March 2015Net-Export 68,000 kwh
NET-ZERO
This is possible with a net metering agreement with PGE
Need special Net Metering Meter (installed by PGE)
27City of Gresham WWTP
No electricity purchased from PGE sinceFebruary, 2015 - Energy Net-Zero Goal Met!
28
Annual Energy Trends Since 2005
City of Gresham WWTP
Net-Exporter
2005-2015 Consumption and Production
17% reduction in Power Consumption One Year of Energy Net-Export in March, 2016 0 kWh PGE Utility Bill each month for a Year 595,000 kWh of Net-Exported power donated to PGE
(worth $22,000 wholesale rate)
0
1,000,000
2,000,000
3,000,000
4,000,000
5,000,000
6,000,000
7,000,000
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
Gresham WWTP Power Production and Consumption (kWh)
Solar
Cogen 2
Cogen 1
Consumption
29
Annual Savings
City of Gresham WWTP
Net-Exporter
2005-2015 Consumption and Production
Approximately $750,000 per year ongoing savings $3,500,000 in savings since 2005
$0
$100,000
$200,000
$300,000
$400,000
$500,000
$600,000
$700,000
$800,000
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015
Annu
al S
avin
gs/R
even
ue10-Year Avoided Utility Costs and
FOG Tipping Fee Income
Cogen 1 Cogen 2 FOG Solar
Energy Projects Cost Summary
City of Gresham WWTP
Energy Trust Technical Assistance and Incentives State of Oregon BETC Program State of Oregon CHP Business Energy Incentive
$1,364,147
$2,254,938
$5,971,934
$0
$2,000,000
$4,000,000
$6,000,000
$8,000,000
$10,000,000
$12,000,000
10 Years of Energy Related WWTP Projects
Gresham
ODOE
Energy Trust
38%
30
31
Cogeneration O&M Costs
City of Gresham WWTP
Net-Exporter
About $0.03 per kWh O&M Costs Includes Labor & Materials for O&M.
¢ 2.1
¢ 1.2
¢ 8.0
¢ 0.0
¢ 1.0
¢ 2.0
¢ 3.0
¢ 4.0
¢ 5.0
¢ 6.0
¢ 7.0
¢ 8.0
¢ 9.0
2005 thru 2014
O&
M C
ost p
er k
Wh
400 kw Cogeneration O&M Cost Summary
BiogasTreatment
Cogeneration
Avoided Utility Rate
Awards and Recognition 2015 OR APWA Environmental
Project of the Year 2015 American Biogas Council
Project of the Year Award 2014 Clean Energy States
Alliance, State Leadership in Clean Energy Award
2015 ACWA Outstanding Member Agency
2015 Recognized in EPA report on Sustainable Water Future
City of Gresham WWTP 32