INTEROFFICE MEMORANDUM

Transcription

1 INTEROFFICE MEMORANDUM DATE: October 23, 29 TO: Boise Public Works Commission FROM: Matt Hightree, Civil Engineer SUBJECT: Energy Consumption at Major Facilities Managed by Public Works This memo is presented on a semi-annual basis to update the Commission on the status of energy consumed and energy conservation projects occurring at major City-owned facilities managed by Public Works. Changes from the previous report are shown with bold font. Energy Use Narrative for Wastewater Facilities In the past several years a number of projects have been initiated to reduce utility energy use. One project cleaned the biogas to reduce the maintenance impacts. Another project used the biogas in applications that previously used natural gas; from March through September 29 the lab natural gas use dropped to 25.7 percent of the amount used during the same period in previous years, and the biosolids dewatering building has used no natural gas since June of 28. The primary scum handling system at West Boise has been modified to improve performance and reduce energy use. The new system was put into operation in October 29 and will reduce electricity used previously for heat tracing and also reduce energy needed to heat hot water for the scum pit heat exchangers. The Combined Heat and Power (CHP, also known as co-generation) project at West Boise for using biogas-fueled internal combustion engine-generators to generate electricity and recover heat from the engines and exhaust continues to move forward. The Request for Proposals to lease equipment for CHP is in final review and is scheduled to be advertised on November 18. Financing of the CHP project will not be through a City CIP budget due to cash flow concerns. Approximately half of the funding for the installation of leased equipment will be from a US Dept. of Energy grant. Variable frequency drives for two 15 hp motors on the W3 were put into service on March 1, 29. It was estimated this project would save 313, kwh and $9, per year during project planning. The chart at the end of this report shows performance from March through September, with an apparent decrease in electrical use of 54 kw, or an equivalent savings of 47, kwh per year. Staff continues to monitor actual performance. Automated control of air supplied to Aeration Basin 2 at West Boise will be put into service in November and will provide control similar to the system Lander Street has used for several years. This basin will be used to evaluate the effectiveness of the controls before adding them to the other aeration basins. Reduced air demands will reduce the electrical energy used by the Aeration Blowers. The following table summarizes current projects. A more comprehensive project list is attached following the energy use charts. In addition to these one-time projects, plant electrical use monitoring has been initiated at West Boise and at Lander Street. The monitoring data will serve as a baseline and will enable better measurements of the actual 1

2 performance of energy savings projects. Tables showing the monitoring summary are included near the end of this report. Current and Planned Projects to Reduce Utility Energy Consumption Project Name Dates Purpose West Boise WWTF Combined Heat and Power (CHP, aka cogeneration) West Boise WWTF Primary Scum System Improvements West Boise WWTF Aeration Basin 2 automatic air control valves Energy Use Narrative for City Hall Pre-design review complete Sept 28; design-build effort started January 29; seek funding source starting Feb 29; cancel D-B and start CHP equipment lease RFP May 29; advertise lease RFP Nov 29 Bids opened Jan 29, construction substantially completed October 29 Actuators ordered fall 28, mounted by contract September 29; electrical and PLC work completed October 29 Increase digester gas use; generate "green" electrical power for sale to Idaho Power Co.; use recovered heat to replace heat needed from boilers Resolve operational difficulties with system and reduce energy consumption. Converting to unheated glass-lined piping system. Automate 5 existing manual isolation valves to control air delivery based on dissolved oxygen in 5 cells in the basin. Piecemeal approach done to save money. The City Hall Complex is comprised of three separate buildings connected by a central atrium. Electricity is used in the City Hall complex for space cooling, equipment motors and controls, lights, computer and security systems, domestic water heating, and other minor loads. Electricity is also used as a backup for space heating in the event geothermal heat is not available. Space heating for the complex is supplied primarily by geothermal water. During the summer s there is no geothermal water use, so the charts below only show the s of October through March. Energy Use Narrative for Twenty Mile South Farm Practices at the Farm have been developed to use irrigation water efficiently with the current infrastructure. Efficient water use can be related directly to electrical usage by the irrigation well pumps delivering water to the irrigation equipment (for example, kwh per million gallons pumped) and applying water commensurate with crop requirements. TMSF continues to monitor irrigation rates by field and crop for comparison to local evapotranspiration data. The attached TMSF electrical use chart has been updated using data from the Idaho Power website and reflects power consumption for the TMSF irrigation wells. Approximately 95% of the TMSF power consumption is used for pumping irrigation water. For FY9, electrical usage was 12.5% lower (5,424,385 kw-hours) than in FY8 (6,21,52 kw-hours). This was due to higher amounts of precipitation received than in 29 and 2

3 reduced irrigation water requirements for the majority of crops grown. Approximately the same number of acres was irrigated in 28 and 29. In FY21, the Nicholson addition acreage will be put into service (~235 acres) and new well 12 will be brought on-line. This will result in a 7% increase in irrigated acres and on average, power consumption would be expected to increase by a similar percentage. Actual power usage will be influenced by the crop mix and weather conditions. MDH/mh Attachments: Unit Energy Use Charts for Lander Street WWTF and West Boise WWTF Unit Geothermal Use and Total Electrical Use Charts for City Hall Total Electrical Use Chart for TMS Farm WWTF Projects to Reduce Utility Energy Consumption West Boise Electrical Monitoring Summary West Boise WWTF - W3 History H:\docs\SAR655- energy use & conservation\pwc energy report text 9128.doc 3

4 Natural Gas Use, therms/mg treated 16 4 Lander Street WWTF Unit Energy Use- Natural Gas FY 27 Annual Cost: $ 49,743 for 1.48 therms/mg FY 28 Annual Cost: $ 2,237 for 4.63 therms/mg FY 29 YTD Cost: $ 14,397 for 3.3 therms/mg FY 29 budget: $ 86,32 (spent 16.7% of budget) FY 26 FY 27 FY 28 FY 29 Natural Gas Use, therms/mg treated 16 4 West Boise WWTF Unit Energy Use- Natural Gas FY 27 Annual Cost: $269,95 for 46.6 therms/mg FY 28 Annual Cost: $127,361 for therms/mg FY 29 YTD Cost: $ 97,993 for 18.9 therms/mg FY 29 budget: $271,387 (spent 36.1% of budget) FY 26 FY 27 FY 28 FY 29 Energy Use at Wastewater Treatment Facilities, City Hall and, TMS Farm through Sept 29

5 Compare Natural Gas and Digester Gas use at Lander St WWTF 16 Lander Street WWTF Unit Energy Use- Natural Gas Only Natural Gas Use, therms/mg treated 4 FY 26 FY 27 FY 28 FY Lander Street WWTF Unit Energy Use- Digester Gas Only Digester Gas Use, therms/mg treated 4 FY 26 FY 27 FY 28 FY 29 Energy Use at Wastewater Treatment Facilities, City Hall and, TMS Farm through Sept 29

6 Compare Natural Gas and Digester Gas use at West Boise WWTF 16 West Boise WWTF Unit Energy Use- Natural Gas Only Natural Gas Use, therms/mg treated 4 FY 27 FY 28 FY West Boise WWTF Unit Energy Use- Digester Gas Only Digester Gas Use, therms/mg treated 4 FY 27 FY 28 FY 29 Energy Use at Wastewater Treatment Facilities, City Hall and, TMS Farm through Sept 29

7 Electricity Used, kwh/mg treated * Lander Street WWTF Unit Energy Use- Electricity FY 27 Annual Cost: $253,953 for 2,51 kwh/mg FY 28 Annual Cost: $328,843 for 1,997 kwh/mg FY 29 YTD Cost: $391,984 for 2,96 kwh/mg FY 29 budget: $43,749 (spent 97.1% of budget) FY 26 FY 27 FY 28 FY 29 Electricity Used, kwh/mg treated West Boise WWTF Unit Energy Use- Electricity FY 27 Annual Cost: $425,22 for 2,685 kwh/mg FY 28 Annual Cost: $538,463 for 2,997 kwh/mg FY 29 YTD Cost: $656,687 for 2,97 kwh/mg FY 29 budget: $531,31 (spent 123.6% of budget) FY 26 FY 27 FY 28 FY 29 Energy Use at Wastewater Treatment Facilities, City Hall and, TMS Farm through Sept 29

8 CH1 - Gallons per HDD per Square Foot Gallons Geothermal Water Used per Heating Degree Day per square foot Oct Nov Dec Jan Feb Mar Month FY24 FY25 FY26 FY27 FY28 FY29 CH2 - Gallons per HDD per Square Foot Gallons Geothermal Water Used per Heating Degree Day per square foot Oct Nov Dec Jan Feb Mar Month FY24 FY25 FY26 FY27 FY28 FY29 Energy Use at Wastewater Treatment Facilities, City Hall and, TMS Farm through Sept 29

9 City Hall Electrical Use by quarter FY ,2, 1,, Electrical Use, kwh, 6, 4, FY24 FY25 FY26 FY27 FY28 FY29 2, Q1 Q2 Q3 Q4 Quarter TMSF Electrical Usage for Irrigation Wells 1,6, 1,4, 1,2, kw-hours Used 1,,, 6, 4, 2, Jan Feb March April May June July Aug Sep Oct Nov Dec Month Energy Use at Wastewater Treatment Facilities, City Hall and, TMS Farm through Sept 29

10 WWTF Projects to Reduce Utility Energy Consumption Project Name Dates Purpose constructed and commissioned in 24 Lander Street WWTF Digester Gas Cleaning Facility Lander Street WWTF Ferrous Chloride system Lander Street WWTF Burner Replacement for Boiler No. 2 West Boise WWTF gas utilization study by B&C, with follow-up work by MWH and CH2M Hill West Boise WWTF Ferrous Chloride system West Boise WWTF biogas cleaning and storage system design West Boise WWTF biogas distribution system design for space heating of some plant buildings commissioned in August of 27 placed in service on May 11, to 27; master plan final report issued in July 27. put in service late in August 25, stopped using July 26, started again July 27 Construction NTP Oct 3, 26, work commissioned in Aug nd boiler started on DG Nov 26, 27. Part 1: Lab started burning DG in boiler on Feb 12, 29. Hot water heating of dewatering building with DG-fire boilers started Nov 28. Part 2: started design Jan 28, project abandoned Mar 28 Removes siloxanes from the gas, dries and removes particles from the gas. See comments for West Boise system below Allow biogas to be burned in Boiler No. 2, the larger of two boilers at this facility. The smaller boiler has always burned biogas. Evaluate methods for biogas cleaning, storage, and utilization. Provide recommendations to City managers for optimum gas uses. Gas treatment and gas distribution projects have been completed, co-generation using biogas-fueled enginegenerators is recommended. Master plan consolidates previous work & develops implementation schedule. When injected in the sludge before it enters the digesters, ferrous chloride chemically binds sulfides and greatly reduces the concentration of hydrogen sulfide in biogas. Concentrations drop from 17 ppm to under 1 ppm. Remove siloxanes, moisture and particles from gas. Make gas suitable for use in boilers, furnaces, and engines. Gas blower distributes gas to boilers and future equipment. Experiencing some control difficulties and a heat exchanger failure in the spring 29. Deliver cleaned gas to selected buildings, where it can be burned boilers, or deliver hot water from digester complex to heating coils in air handlers. Part 1: Lab and dewatering buildings Part 2: Galleries and Headworks Building abandoned because pre-design cost estimate was 3 times the master plan estimate & resulted in a negative net present value for the work Wastewater Treatment Facilities Utility Energy Reduction Projects 1

11 WWTF Projects to Reduce Utility Energy Consumption Project Name Dates Purpose Pre-design review complete Sept 28; design-build effort started January 29; seek funding source starting Feb 29; cancel D-B and start CHP equipment lease RFP May 29; advertise lease RFP Nov 29 West Boise WWTF Combined Heat and Power (CHP, aka cogeneration) West Boise WWTF Digester No. 3 West Boise WWTF ventilation reduction study West Boise WWTF W3 water system pumps West Boise WWTF Primary Scum System Improvements West Boise WWTF Aeration Basin 2 automatic air control valves 2-part project. 1 st portion completed Nov nd portion completed April 29 study completed in Jan 26. Design started in April, 27, construction completed Oct 28. Study completed in Jan 28. System started up March 1, 29. Bids opened Jan 29, construction substantially completed October 29 Actuators ordered fall 28, mounted by contract September 29; electrical and PLC work completed October 29 Increase digester gas use; generate "green" electrical power for sale to Idaho Power Co.; use recovered heat to replace heat needed from boilers Increase solids handling capacity at West Boise, revise biogas piping system for code compliance Report and staff recommend code-allowed ways to reduce ventilation rates under certain occupancy conditions and thereby reduce natural gas consumption. Install two variable speed drives on the pumping system to reduce electrical costs. Savings up to $9, per year are estimated, about 2 percent of the plant electrical use. Resolve operational difficulties with system and reduce energy consumption. Converting to unheated glass-lined piping system. Automate 5 existing manual isolation valves to control air delivery based on dissolved oxygen in 5 cells in the basin. Piecemeal approach done to save money. Wastewater Treatment Facilities Utility Energy Reduction Projects 2

12 Meter (billed) kwh for Lander Street Electrical Monitoring Summary Area of Plant Total submetered Aeration blowers UV disinfection plus W3 pumping Rawe Sewage pumps Intermediate pumps Month Aug-9 737, % 26.2% 23.1% 2.6% 2.% 3.2% Sep-9 75, % 27.2% 24.3% 2.7% 2.2% 3.2% RAS pumps Month Meter (billed) kwh for West Boise Electrical Monitoring Summary Area of Plant Total submetered Aeration blowers UV disinfection plus W3 pumping Headworks with influent pumping North plant aeration with RAS & ML pumping All south plant aeration loads except RAS pumping Oct-8 1,239, % 27.8% 19.7% 17.5% not recorded not recorded Nov-8 1,23, % 28.5% 18.8% 18.1% not recorded not recorded Dec-8 1,3, % 25.2% 18.2% 17.8% 3.4% 5.5% Jan-9 1,38, % 24.7% 17.3% 18.2% 3.4% 4.4% Feb-9 1,22,94 69.% 27.4% 17.6% 17.% 2.9% 4.1% Mar-9 1,31, 71.1% 29.1% 17.5% 17.9% 2.2% 4.4% Apr-9 1,26,25 68.% 3.2% 17.4% 15.6% 3.4% 1.4% May-9 1,213, % 22.6% 16.% 14.5% 4.2% 2.% Jun-9 1,189, % 3.7% 15.5% 14.% 5.8% 1.9% Jul-9 1,245, % 3.2% 15.4% 13.5% 6.3% 1.9% Aug-9 1,22, % 28.9% 16.3% 14.2% 6.% 2.% Sep-9 1,126, % 27.8% 17.% 13.6% 5.8% 2.1% Wastewater Treatment Facilities Utility Energy Reduction Projects 3

13 Control tuning and equipment failure March 21 to April 2, 29 Started March 1, 29 West Boise WWTF- W3 History 14 Average 266 kw since April 2 W3 header pressure, psi /1/9 3/15/9 3/29/9 4/12/9 4/26/9 5/1/9 5/24/9 6/7/9 6/21/9 7/5/9 7/19/9 8/2/9 8/16/9 8/3/9 9/13/9 9/27/9 UV MCC kw measured 2 Average 32 kw to March 1 date pressure, psig kw, measured Wastewater Treatment Facilities Utility Energy Reduction Projects 4