INTEROFFICE MEMORANDUM

Transcription

1 INTEROFFICE MEMORANDUM DATE: April 24, 29 TO: Boise Public Works Commission FROM: Matt Hightree, civil engineer SUBJECT: Energy Consumption at Major Facilities Managed by Public Works This report contains new information shown in bold. This memo is presented on a quarterly 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. Some projects involved cleaning the biogas to reduce the maintenance impacts. Other projects used the biogas in applications that previously used natural gas. In November and December the Dewatering Building and the Lab were switched to heating using digester gas. After a week of use, the lab boiler was switched back to natural gas until February 12, 29 when it was permanently switched to digester gas. During March the lab natural gas use dropped to 9 percent of the amount used in March 28. The primary scum handling system at West Boise is being modified to improve performance and reduce energy use. Combined Heat and Power (CHP, also known as cogeneration), a means of using biogas-fueled internal combustion engine-generators to generate electricity and recover heat from the engines and exhaust, is being considered for the West Boise facility. A draft Request for Proposals to complete a Design/Build CHP project is to be delivered by the end of April for City review. Financing of the CHP project will not be through a City CIP budget due to cash flow concerns, so staff is seeking alternative methods of project financing. Variable frequency drives for two 15 hp motors on the W3 were put into service on March 1, 29. This project is estimated to save 313, kwh and $9, per year. The chart at the end of this report shows performance in March and April, with an apparent decrease in electrical use of 2 kw, or an equivalent savings of 175, kwh per year. Staff will continue to monitor actual performance. 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, with plans to begin similar data collection at Lander Street. The monitoring data will serve as a baseline that helps identify the biggest energy uses and therefore biggest potential energy savings opportunities, and will also enable better measurements of the actual performance of energy savings projects like the W3 pumps. A table showing the West Boise monitoring summary is included near the end of this report. 1

2 Current and Planned Projects to Reduce Utility Energy Consumption Project Name Dates Purpose biogas distribution system design for space heating of some plant buildings Part 1: Lab started burning DG in boiler on Feb 12, 29. Hot water heating of dewatering building with DGfire boilers started Nov 28. Part 2: gallery heating 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. Lab and dewatering buildings converted co-generation Digester No. 3 W3 water system pumps Primary Scum System Improvements Energy Use Narrative for City Hall project abandoned Mar 28 Pre-design review complete Sept 28; design effort started January 29; seek funding source starting Feb 29 2-part project. 1 st portion completed Nov nd portion completion projected for April 29 Study completed in Jan 28. Started March 1, 29. Bids opened Jan 29, construction to be completed in FY 29 2 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 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. 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. We are continuing to improve lighting efficiency throughout City Hall. Space heating for the complex is supplied 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. For FY29, the year-to-date electrical usage is at low rates as is typical for farm operations. The irrigation systems were started up the first week in April and usage rates are expected to follow similar patterns as the past two years (refer to TMSF Electrical Use Chart). Peak usage occurs in June through August. MDH/mh

3 Attachments: Unit Energy Use Charts for Lander Street WWTF and 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 - W3 History H:\docs\SAR655- energy use & conservation\pwc energy report text 9424.doc 3

4 Natural Gas Use, therms/mg treated 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: $ 13,21 for 5.82 therms/mg FY 29 budget: $ 86,32 (spent 15.3% of budget) FY 26 FY 27 FY 28 FY 29 Natural Gas Use, therms/mg treated 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: $ 75,37 for therms/mg FY 29 budget: $271,387 (spent 27.8% of budget) FY 26 FY 27 FY 28 FY 29 Energy Use at Wastewater Treatment Facilities, City Hall and, TMS Farm through Mar 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 FY 26 FY 27 FY 28 FY Lander Street WWTF Unit Energy Use- Digester Gas Only Digester Gas Use, therms/mg treated FY 26 FY 27 FY 28 FY 29 Energy Use at Wastewater Treatment Facilities, City Hall and, TMS Farm through Mar 29

6 Compare Natural Gas and Digester Gas use at 16 Unit Energy Use- Natural Gas Only Natural Gas Use, therms/mg treated FY 27 FY 28 FY Unit Energy Use- Digester Gas Only Digester Gas Use, therms/mg treated Lab boiler used DG in Dec, FY 27 FY 28 FY 29 dewatering building switched to hot water from DG-fired boilers too. Energy Use at Wastewater Treatment Facilities, City Hall and, TMS Farm through Mar 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: $178,597 for 2,17 kwh/mg FY 29 budget: $43,749 (spent 44.2% of budget) FY 26 FY 27 FY 28 FY 29 Electricity Used, kwh/mg treated 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: $32,965 for 3,233 kwh/mg FY 29 budget: $531,31 (spent 57.% of budget) FY 26 FY 27 FY 28 FY 29 Energy Use at Wastewater Treatment Facilities, City Hall and, TMS Farm through Mar 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 Mar 29

9 City Hall Electrical Use by quarter FY Electrical Use, kwh FY24 FY25 FY26 FY27 FY28 FY29 2 Q1 Q2 Q3 Q4 Quarter Twenty Mile South Farm Electrical Use (Composite of All Meters) 1,6, 1,4, kwh per 1,2, 1,, 8, 6, FY7 FY8 FY9 4, 2, October November December January February March April Month May June July August September Mar 29 data only reflects billing through 3/18/9 Energy Use at Wastewater Treatment Facilities, City Hall and, TMS Farm through Mar 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 gas utilization study by B&C, with follow-up work by MWH and CH2M Hill Ferrous Chloride system biogas cleaning and storage system design 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 effort started January 29; seek funding source starting Feb 29 cogeneration Digester No. 3 ventilation reduction study W3 water system pumps Primary Scum System Improvements 2-part project. 1 st portion completed Nov nd portion completion projected for April 29 study completed in Jan 26. Design started in April, 27, construction completed Oct 28. Study completed in Jan 28. Started March 1, 29. Bids opened Jan 29, construction to be completed in FY 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. West Boise Electrical Monitoring Summary Location/ Plant Area Oct-8 Nov-8 Dec-8 Jan-9 Feb-9 Mar-9 Total billed kwh for : 1,239,375 1,23,794 1,3,832 1,38,168 1,22,94 1,31,8 Aeration blowers 27.8% 28.5% 25.2% 24.7% 27.4% 29.1% UV disinfection plus W3 pumping (UV MCC) 19.7% 18.8% 18.2% 17.3% 17.6% 17.5% Headworks with influent pumping & plant air compressors 17.5% 18.1% 17.8% 18.2% 17.% 17.9% North plant aeration with RAS & ML pumping All south plant aeration loads except RAS pumping not recorded not recorded not recorded 3.4% 3.4% 2.9% 2.2% not recorded 5.5% 4.4% 4.1% 4.4% Wastewater Treatment Facilities Utility Energy Reduction Projects 2

12 VFD started March W3 History Control tuning & equipment failure March 21 to April 2, W3 header pressure, psi UV MCC kw measured /1/9 Average 32 kw to March 1 3/8/9 3/15/9 3/22/9 3/29/9 4/5/9 4/12/9 4/19/9 4/26/9 date Average 3 kw since April 2 pressure, psig kw, measured Wastewater Treatment Facilities Utility Energy Reduction Projects 3