Water utilities venture into energy generation to save money
PHILADELPHIA, Aug. 30, 2000 -- Attendees on the last day of the Energy Efficiency Forum tackled the issue of electricity generation, discussing techniques and warnings for onsite power generation, making power from digester gas, and fuel cell power. Other topics included aeration, energy management, pump system efficiency and energy optimization.
The topics were part of a three-day, narrowly targeted program hosted by WaterWorld Magazine and PennWell Corporation, with latest research on conserving energy from a water or wastewater utility's perspective. The conference, now in its third year, also includes exhibits on products for more energy-efficient water and wastewater systems.
Matt Clark, Facilities Design Section Manager of HDR Engineering
There was intense interest in the session about power generation to offset energy costs or to recycle excess biogas. Matt Clark, Facilities Design Section Manager for HDR Engineering, presented a paper on a new onsite generation facility for the City of Fresno, Calif.
Fresno owns and operates an 80-mgd wastewater treatment plant which uses two internal combustion engines firing digester gas to generate a small fraction of the facility's power needs. The plant also has a small package boiler that burns digester gas to produce steam, which is used for digester heating. But the city has also been looking at installing a new power generation plant at this location.
After exploring the idea of buying new equipment, the engineering firm doing the study settled on a used combined cycle cogeneration plant from a site which had closed in 1998. The power plant, with a nominal electric capacity rating of 9 MW and a maximum steaming rate of 38,000 pounds per hour (pph), had only been used for two years and appeared to be performing as required. The plant was designed to burn natural gas and diesel fuel oil.
The city hoped to change the fuel method to a blend of low-Btu digester gas (at 500 to 600 Btu/CF) and natural gas to obtain a medium Btu blended gas of 800 Btu/CF, but first another system must clean, compress and store the digester gas in preparation for blending with natural gas.
The system also has a small water treatment system with water softeners, reverse osmosis demineralizers, and filters. The water is treated so that it is clean enough to use within the power generator in the steam process.
The three generators can produce a total of approximately 9 MW of electrical energy at 12 kV, enough to power the entire treatment plant.
The whole generation project would probably cost around $7.49 million, which includes purchase and delivery of the used equipment, plus the cost of the new equipment required to complete the facility. The project was expected to save the city roughly $10 million after 20 years in operation.
It should go into bidding this month and work may also begin during the same month. Based on the analysis, the plant could be fully operational by summer 2001.
Another location, the city of Allentown, Penn., installed a microturbine energy generation system which used digester gas in its raw form to produce more than 2 million kwh per year.
John Steckel Jr., PPL Spectrum Inc.
The digester gas contained an average of 58-62 % methane gas, and the microturbines got close to 100 % combustion efficiency, said John Steckel Jr., an engineer with PPL Spectrum, Inc., and the author of the paper.
The microturbines are a new technology - each low-maintenance, modular unit produces about 30 kw and has very low NOX emissions in the range of 2-3 ppm, Steckel said.
"The microturbine technology makes this applicable for mid-sized plants," Steckel said.
The city has begun installing the microturbine generators and plans to install a total of 12 generators with three heat exchangers.
The project should give the WWTP a raw value of $165,000 per year in energy savings. Under a ten-year contract with Spectrum, the city's share would be $20,000 per year.
The contractor has just finished an investor grade audit, and approval is expected on Sept. 5. The plant should be ready to start up in early 2001.
In another presentation, a fuel cell power plant which began operation in July 1999 provided almost pollution-free generation of 175 kW from digester gas, with reuse of the waste heat as well.
Duane Sanger, Public Works Mgr., City of Portland
The project, presented by Duane Sanger, Public Works Manager for the City of Portland, was made possible by three grants totaling $486,000. The city borrowed an additional $790,000 in a new kind of partnership deal with a local bank in which the state awarded the bank a 35 percent income tax credit and the bank shared it with the WWTP.
As a result, the city borrowed $790,000 at a negative interest rate of 2.4 percent. In essence, it only had to pay back $740,000.
Fuel Cells are electrochemical devices that convert a fuel's energy directly to electrical energy, the National Fuel Cell Research Center said. Fuel cells operate much like continuous batteries when supplied with fuel to the anode (negative electrode) and oxidant (e.g. air) to the cathode (positive electrode). Fuel cells extract energy by chemically combining the molecules of a fuel and oxidizer without burning, dispensing with the inefficiencies and pollution of traditional combustion.
The fuel cell technology at the Portland WWTP is 38 percent efficient with generation only and 80 percent when waste heat is also recovered. In addition, it has few moving parts and is odorless and quiet. Each unit takes up about 100 square feet of space, plus there are two small separate units for gas pretreatment and backup cooling.
To use digester gas in the fuel cell, first it has to be put through a scrubber to remove sulfur and other impurities.
The WWTP produced 170,000 cubic feet of methane gas which was flared off, but is now used in the fuel cell to produce 1,400,000 kwh per year, reducing the plant's annual electricity bill by $92,000. In addition, the fuel cell produces 800,000 Btu/hr of recoverable heat, Sanger said.
Exhibitors
Products and services on display at the Energy Efficiency Forum ranged from valves to educational materials.
EPRI
The Electric Power Research Institute offered technical information on energy efficiency.
The Electric Power Research Institute (EPRI), one of the forum's co-sponsors, had technical information on several energy efficient methods for water and wastewater. Under their Municipal Water and Wastewater program, they support research and development of new treatment processes which help utilities save on energy costs.
EPRI is joined with the American Water Works Assn. Research Foundation (AWWARF) and the Water Environment Research Foundation (WERF).
One of the main objectives of the cooperative effort is to leverage research and development dollars so that the program participants gain a multiple return on one investment. Supported research includes retrofit of existing facilities and design of new facilities for electric, water and wastewater utilities.
Several documents are available through EPRI, including its Techcommentary publications, documents about six pages in length which cover one specific topic of interest. They include "Energy-Efficient Aeration Systems for Wastewater Treatment" and "Improving Operation of Aeration Systems Using DO Probes". For more information, visit EPRI's web site or call EPRI's AMP Program office at (800) 4320-AMP.
Pennsylvania DEP
Water Supply Specialist Karen Brown and Environmental Engineer Keith Dudley, both from the Department of Environmental Protection
The Pennsylvania DEP offered technical information on pollution prevention and energy efficiency, beneficial use of biosolids and the Pennsylvania nonpoint source management program. Under a program called "P2/E2," the DEP offers help to Pennsylvania industrial and commercial businesses, municipalities and farming operations with good compliance records by visiting the site and suggesting ways to reduce pollution and increase energy efficiency.
Pollution Prevention (P2) is source reduction and other practices that reduce or eliminate the creation of pollutants through increased efficiency in the use of raw materials, energy, water or other natural resources by conservation.
Energy Efficiency (E2) reduces the use of generally-non-renewable energy forms such as electricity and natural gas. E2 practices lower operating costs and contribute to a company's bottom line without affecting productivity or safety and may also improve environmental quality as well.
In addition to free site visits and recommendations for better practices, a related program offered through the DEP obtains funding for small businesses to pay for site assessments not conducted by the DEP. Under the P2/E2 Site Assessment Grant Program, DEP will fund 80 percent of the cost of a pollution prevention and energy efficiency site assessment up to a maximum of $5,000. The assessment can be conducted by environmental consultants, service providers or others experienced in providing such assessments.
For more information, visit DEP's web site or call +1-717-783-9981.
Passaic Valley Sewerage Commissioners
The Passaic Valley Sewerage Commissioners offered liquid waste disposal for businesses or municipalities in the Northeastern US.
Passaic Valley Sewerage Commissioners, a wastewater treatment plant in Newark, NJ, offered liquid waste disposal services. The company accepts liquid waste from liquid waste haulers, wastewater treatment facilities, water treatment plants, pharmaceutical companies, food processors, chemical manufacturers and textile companies.
The plant itself uses secondary wastewater treatment to treat 330 million gallons of wastewater per day. The 172 acre plant is one of the largest modern wastewater facility in the Eastern United States and one of the half-dozen largest in the entire Country. The secondary treatment approach utilizes a pure oxygen-activated sludge process with wet air oxidation for sludge treatment.
For more information, visit PVSC's web site.
ITT Industries
ITT Industries had case studies available on its DOE Showcase Demonstration projects on the City of Milford, Conn., and the Town of Trumbull, Conn. Both involved the replacement of large pumps with smaller pumps that were better suited to the average pumping volume required. Gunnar Hovstadius, Director of Engineering for ITT Industries, explained the concept Aug. 29 in his paper, "Life Cycle Cost in Optimizing Pump Systems." A smaller pump which is sized to the regular flows will last longer and be more energy-efficient than a larger pump which is only pumping at a fraction of its capacity and turning on and off frequently as a result, Hovstadius said.
In addition to the case studies, the booth had information on its N-Pump series of submersible wastewater pumps, designed for efficiency even with viscous fluids. The series includes pump capacities up to 8,700 gpm. For more information on ITT Flygt's pumps or the case studies, visit ITT Industries' web site.
The DOE Showcase is a technology-related case study which is supported by the U.S. Department of Energy. For more information on the program, visit the Best Practices page on the DOE site.
Powerware Solutions
Powerware Solutions, Energy Efficiency Forum's Platinum Sponsor, showed a software package called WaterSuite.
Powerware, the forum's Platinum Sponsor, had a software package called WaterSuite. The modular application is designed to help utilities improve efficiency by structuring its recordkeeping functions.
The application joins the separate operations of engineering design, operations, maintenance and business management to optimize electrical distribution and thus reduce costs. The schedule optimizations include operating parameters such as quality, costs, and variances in demand. The interface also displays all aspects of the distribution system, forecasting for operators how a schedule will affect each part of the water/wastewater system. The program is currently installed at the city of Irving, Texas and East Bay Municipal Utilities District (northern Calif.) Irving, located close to Dallas, has a population of about 180,000 and has saved roughly 14 percent on its energy costs over a 5-year period. EBMUD's water system serves about 1.2 million, while its wastewater treatment system serves about 600,000.
Two technical papers were offered, "Optimization Savings Opportunities: Deregulated vs. Regulated Electricity Markets" and "Set My Data Free!: UCA - Standard SCADA Interface." In the paper about deregulation, CEO Richard Jamieson said that whether the market is competitive or not, load shifting is a technique which increases market efficiency by reducing demand when price of power is high. Load shifting is the use of equipment during off-peak pricing times instead of during peak pricing times of the day, whenever possible.
In the paper about SCADA, Program Manager Raymond Joseph said that use of the Utility Communications Architecture (UCA) from the Institute of Electrical and Electronic Engineers (IEEE) can streamline a water or wastewater utility's business processes so that operations, design and management departments run smoothly. Systems which are specified by the standards include data acquisition systems, databases and other systems.
For more information, visit Powerware's web site.
Turblex, Inc.
Turblex offered a compressor for aeration systems that is designed to be energy efficient. The Turblex/HM-Turbo single-stage integral gearbox turbo compressor has a variable flow with turndown to 45% or less at constant speed. The compressor is smaller than most compressors it can replace. It is designed to meet demands for high efficiency over a wide regulating range. Torsional analysis in the coupling dictates the type of coupling to minimize vibration and prolong life of the equipment. The compressor units can be driven by electric motors, internal combustion engines or steam turbines. The compressor is useful for wastewater aeration, steam compression, two-stage air pressurization or non-air process applications. Also on display were instrumentation systems to go with the compressors.
Mace gave a presentation on how rebates help with aeration systems Aug. 28. He said that the average medium-sized wastewater treatment plant could save $219,000 per year with an aeration equipment upgrade. Rebates for capital equipment purchases by power generating utilities have been a catalyst to move sometimes stalled upgrades forward, Mace said. Many power utilities offer rebates if water utilities upgrade diffusers, blowers or instrumentation for energy efficiency, and water utilities can take advantage of that.
For more information, call +1-417-864-5599.
Power Correction Systems, Inc.
Power Correction Systems offered active harmonic filters to save energy and lengthen equipment life. In any large business, electronic systems cause harmonic noise and a poor power factor, causing heat, trips, lockups and other problems with equipment. Since electric companies often assess penalties for poor power factor, water/wastewater utilities that correct the problems can save money on energy. Filters, installed at the power source before the equipment, senses the critical portions of "dirty" power and injects a correcting element to "clean" the power (normalize its rhythm). By canceling the harmonic component, the true fundamental becomes the only component that is reflected back to the line, said President Brahm Segal, who presented a paper on harmonic filtering and cost reduction.
For more information, visit the Power Correction Systems' web site.
Milliken Valve Co., Inc.
Milliken Valve displayed several energy-efficient valves, including the Eccentric Plug Valve and the Flex Check™ Valve. Both valves are made of high-strength ductile iron. The Flex Check valve has a pressure rating of 285 psi. By virtue of its design, the check valve is energy efficient because it does not require any power to stop the flow of liquids. The Eccentric Plug valve's plug rotates away from the seat when opening. Once it is open, it is out of the flow path, allowing for smooth flow of liquids. This puts less burden on the pumps.
The company also had information on its AWWA Butterfly Valve, a range of plug valves, full port valves and multiport valves and swing check valves.
More information: Complete details about the conference are at http://ww.pennnet.com/home/events.cfm. For more information, call conference coordinator Marvetta McNeel at +1-918-831-9500 or e-mail: [email protected].
