New engines address tightening emissions regulations, bridging the gap between prime and standby power demands.
Recently introduced new engines for prime or standby power reveal a further emphasis on sustainability and efficiency. Increasingly, these engines suit the use of alternative fuel sources and cogeneration applications, and are designed to bridge the gap between island and prime modes in many cases. More and more applications are representing logical uses of these sustainable technologies, from water treatment to greenhouses.
Below is a sample of what the marketplace currently is offering in engines.
Cogen Water Treatment Plant Supplements Grid
A Columbus (GA) Water Works (CWW) wastewater treatment plant is being retrofitted to use cogeneration powered by a new engine technology and was scheduled to go online in August 2009. The 3.5-MW South Columbus Water Resource Facility will use an Advanced Reciprocating Engine System (ARES) powered by two Cummins QSV 91 1,750-kW/12.47-kV natural gas genset reciprocating engines that reportedly will produce at least 20% more power than conventional lean-burn engines using the same amount of fuel.
Combined heat and power (CHP) such as this application is well-suited to the 1,514-rpm, four-cycle QSV91, which uses lean-burn technology that reportedly keeps exhaust emissions levels as low as 250 milligrams per normal cubic meter. The model is also equipped with a permanent magnet generator designed to provide better starting and fault-clearing short-circuit capability, mechanical strengthening for use in utility paralleling with unreliable grids, and auto-shutdown that activates at fault detection. It also has a PowerCommand 3.3 genset control designed to allow full paralleling in grid or load-share modes and a user interface panel that installs in the genset.
Monitoring parameters include engine, alternator, and utility/AC Bus data; and data logs and fault history. The piston cylinder liner has a carbon-cutting ring that prevents carbon buildup between the piston and cylinder wall. Ease-of-maintenance features include simplified cylinder head removal, a multi-duct manifold whose removal does not require removal of common duct or exhaust bellows, and a two-piece camshaft.
CWW is in the Middle Chattahoochee River watershed and provides water and wastewater treatment for 227,600 residents of the Columbus region. In 2004, CWW acquired the water treatment system serving Fort Benning, including a 12-mgd water treatment plant. Cliff Arnett, senior vice president, water resource operations and technical services for CWW, reports that the US Department of Defense’s Base Realignment and Closure (BRAC) program is bringing an additional 20,000 troops to the base along with a roughly 20% increase in wastewater treatment volume.
The $17-million Biosolids Flow-Through Thermophilic Treatment (BFT3) National Advanced Demonstration Project, which commenced in November 2007, is partially funded through EPA and is designed to treat wastewater sludge to Class A Exceptional Quality levels. As of mid-2009, CWW was seeking an additional $2 million in federal funding for the energy component of the operation, having already received a grant of $5 million for the biosolids-processing component. The ARES component of the project is part of the US Department of Energy’s (DOE) Distributive Energy Program for using renewable energy technology such as methane from landfills. The goal of the ARES program is to increase engine efficiencies to increase the energy efficiency of medium-size natural gas engines from 34–38% to 50%, reduce nitrogen oxides emissions from one gram per horsepower-hour to 0.1 gram per horsepower-hour, and reduce operating and maintenance costs by 10%. On this project, the engines will operate at about 40% efficiency.
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Photo: Cummins Power Generation
Cummins 1,750-kW/12.47 kV QSV 91 engine, two of which are being used at a new combined heat and power water-treatment plant in Columbus, GA. |
The cogen operation will alternate the use of two generators powered by the Cummins QSV91 engines that began to be installed in mid-2008. Arnett says that in off-peak hours, the operation will be powered by the local grid. The new cogen process is expected to receive a fuel boost from a new grease-waste transfer station that will increase the amount of methane gas production. This supplemental fuel source should help to provide the cogen operation with enough capacity to power the treatment plant for 14 hours consecutively in a day, Arnett predicts.
Initially, the new cogen operation was conceived as emergency power, says Arnett. But “with our new thermophilic process, we were going to generate so much additional methane gas that it became obvious that we might be able to justify going to full-time operation with generators rather than using them in a standby process,” he says. “You can’t justify the kind of money you spend on these types of projects if you’re just using it in a standby mode. From a revenue-producing standpoint, we’ll be able to supply about 40% of our total plant needs, saving this plant about $600,000 a year at present rates to offset the cost. It creates a payback, you might say, for the installation itself, which is very unusual in the wastewater industry—you hardly ever get a payback. We’re going to get about an eight-year payback.”
Cummins Power Generation installed a main breaker that will synchronize the new ARES with the cogen system and provide a seamless transition to the renewable power source from the grid on short notice. This configuration will give CWW the ability to take the plant off the grid when a storm is approaching and then put it back on the grid after the storm passes, for example.
The ARES will utilize cogeneration of electricity and heat whereby digester gas—biologically produced gas (mostly methane) from controlled decomposition of sludge—will be used to produce electricity and digester heat will be recovered. This plant reportedly will be the first thermophilic plant in the US to be primarily heated by cogeneration waste heat. Also, according to DOE, more than 3,500 of the nation’s wastewater facilities use anaerobic digestion, but only 2% use biogas to produce electricity as the Columbus plant will.
According to CWW, the ARES reportedly is two to 12 times less costly to operate than microturbines and fuel cells. In addition, the ARES is more efficient than fuel cells and almost twice as efficient as microturbines. According to the CWW, a plant this size reportedly could save at least $5 million in capital costs and $70,000 per year in operating costs at 1,000 kW of power compared with similar-capacity fuel cells.
The ARES’ waste heat will provide the 60–108˚C (140–226˚F) temperatures needed for thermophilic treatment of EPA Class A biosolids. The BFT3 process will capture heat from the ARES and it will be sent to the thermophilic anaerobic digestion process to produce Class-A Biosolids. The plant will have a thermophilic digestion volume of 3.0 million gallons, a mesophilic digestion volume of 1.5 million gallons, and a peak raw sludge feed flow of 175 gallons per minute.
The process is expected to reduce carbon dioxide emissions by 9,601 metric tons per year. Additionally, engineering and environmental communities are taking notice of the project. In 2005, the Georgia Chapter of the American Council of Engineering Companies (ACEC) gave project its Grand Conceptor Award and national ACEC gave it a National Honor Award. The International Water Association also presented its 2008 Global Project Innovation Superior Achievement Award to CWW and Brown and Caldwell, the Walnut Creek, CA-based environmental engineering consulting firm on the project. Results of the project will be reported to other water authorities around the nation through groups such as the Water Environment Research Foundation.
“The biosolids treatment part of this project did receive significant federal funding and we believe that it has serious implications for other utilities across the country that have the need to be able to transfer from a low-temperature mesophilic process to a high-temperature process and gain this Class A designation, which allows you to take these biosolids and utilize them virtually anyplace you want to,” says Arnett. “I like to refer to his project as kind of like slaughtering hogs down South: You use everything but the squeal.” Representatives from several municipalities around the country have already visited the operation, he adds.
Five New Engines Introduced
At the Power-Gen International 2008 show, John Deere Power Systems displayed five of its diesel engines: the Tier 3/Stage III A PowerTech Plus 6.8L and 13.5L, the PowerTech E 4.5L and 9.0L, and the PowerTech 3.0L. The PowerTech E 4.5L and 9.0L engines were additions to the company’s lineup of 60-Hz genset engines, which are Tier 3 emissions-compliant and provide an alternative for customers in regions where low-sulfur fuels are not mandated.
The Tier 3 PowerTech Plus 6.8L is a six-cylinder, turbocharged and air-to-air aftercooled engine with full-authority electronic controls, cooled exhaust gas recirculation (EGR), variable geometry turbocharger (VGT) and a high-pressure common-rail (HPCR) fuel system. The engine has genset ratings up to 254 kilovolt-amperes (kVA) (203 kW-electric—kWe) at 60 Hz (1,800 rpm). The Tier 3 PowerTech Plus 13.5L is a six-cylinder, turbocharged and air-to-air aftercooled engine with full-authority electronic controls, cooled EGR, VGT and an electronic unit injector fuel system. It has genset ratings up to 511 kVA (409 kWe) at 60 Hz (1,800 rpm).
The Tier 3 PowerTech E 4.5L is a four-cylinder, turbocharged or turbocharged and air-to-air aftercooled engine with full-authority electronic controls and an HPCR fuel system. This engine features genset ratings up to 161 kVA (129 kWe) at 60 Hz (1,800 rpm). The Tier 3 PowerTech E 9.0L is a six-cylinder, turbocharged and air-to-air aftercooled engine with full-authority electronic controls and an HPCR fuel system and has genset ratings up to 348 kVA (278 kWe) at 60 Hz (1,800 rpm).
The PowerTech 3.0L is a five-cylinder, turbocharged or turbocharged and air-to-air aftercooled engine with mechanical controls. The unit has genset ratings up to 79 kVA (63 kWe) at 60 Hz (1,800 rpm).
In April 2009, Deere announced technology solutions that the company will use to meet Interim Tier 4 emissions regulations in all of its diesel engines used in prime genset applications. US EPA regulations require genset engines for prime power generation to meet Interim Tier 4 standards and genset engines for standby power generation must meet Tier 3 standards. European Union (EU) regulatory standards dictate that genset engines for prime power meet Stage III A regulations and that standby genset engines meet Stage II regulations. At this time, the EU has not indicated that it will require genset engines to meet Stage III B regulations, although the regulations are subject to change. The Interim Tier 4 regulations require at least a 90% reduction in particulate matter and up to a 50% reduction in nitrogen oxides (NOx) from previous Tier 3/Stage III A requirements.
For all of its engines rated at 56 kW (75 hp) and above, the company will start with its Industrial Tier 3 PowerTech Plus engine platform, which includes cooled EGR for NOx control, and add an exhaust filter for reducing particulates. Displacements in this power range include the 4.5L, 6.8L, 9.0L and 13.5L in-line, four- and six-cylinder engines.
The exhaust filter, which consists of a diesel oxidation catalyst (DOC) and a diesel particulate filter (DPF), has been developed for off-highway applications. The DOC reduces carbon monoxide, hydrocarbons, and some particulate matter. DOC and DPF, along with cooled EGR and VGT, are key technologies that Deere is employing for adherence to Interim Tier 4 standards. The downstream DPF traps and holds particulates remaining in the exhaust stream, where they are eventually oxidized through a process known as regeneration. The company points out that a benefit of the exhaust filter is that it replaces the need for a muffler in most applications.
To meet Interim Tier 4 regulations pertaining to 130 kW (174 hp) and above engines that start taking effect January 1, 2011, the cylinder head, fuel system, cooled EGR, VGT and air-to-air aftercooling systems in Deere engines will be updated but will be similar to Tier 3 configurations. The company’s engine models in this power class include the 6.8L, 9.0L, and 13.5L in-line, six-cylinder engines. The engine control unit (ECU) was developed and manufactured by Phoenix International, a business unit of John Deere’s Intelligent Mobile Equipment Technologies. The manufacturer reports that, compared with its Tier 3 counterpart, the new ECU will provide twice the RAM, double the processing speed, and four times the program memory of the previous version.
To meet Interim Tier 4 regulations for engines in the 56-kW (75-hp) to 130-kW (174-hp) range—which take effect on January 1, 2012—the manufacturer will also use a cooled EGR system in combination with an exhaust filter. These engines will be available in 4.5L and 6.8L displacements with full-authority electronic controls, a four-valve cylinder head, air-to-air aftercooling, a high-pressure common-rail fuel system, and a wastegate or variable geometry turbocharger.
Size optimization was a design goal in the company’s Interim Tier 4 engines which, equipped with cooled EGR and an exhaust filter, will have a similar package size to their muffler-equipped Tier 3 counterparts. The 4.5L and 6.8L models below 130 kW (174 hp) will have available engine-mounted or remote-mounted exhaust filters for increased application flexibility. Also, 4.5L and 6.8L engines below 130 kW (174 hp) reportedly will have similar levels of fuel economy that cooled EGR provided in the 130-kW- (174-hp) and-above range for Tier 3 engines, an improvement of as much as 5% compared with the Tier 3 PowerTech M and E models they replace.
Lean-Burn Unit Uses Either Gas or Biogas
At Power-Gen Europe 2009, Dresser Waukesha shared application details of its new turbocharged, lean-burn 16V150LTD Gas Engine for its APG1000 Generator Set. The new engine is designed for the 1-MW class and, according to the company, addresses demand for high-efficiency gas engines for power generation and cogeneration. The new engine was developed through the DOE’s ARES program and production models have a reported efficiency rating of 43.6%.
Of more than 100 units sold to date, most of the units are running on natural gas and a few are fueled by biogases, according to the manufacturer. In addition, most engines are on the grid, but some are operating in island mode or in parallel with another engine. Notable applications include food packaging and horticulture.
In late autumn 2008, the new engine was installed at an Italian food-packaging factory that previously used boilers to produce hot water and steam and was buying electricity from the grid. The hot water system uses heat from the lube oil cooler, intercooler, and jacket water and steam is produced from the exhaust gas. The plant uses the electricity and the excess is delivered to the grid.
Another typical application for the new engine is greenhouses, particularly in the Netherlands. The electricity is used either in the greenhouse or supplied to the grid, the latter when the price of electricity is high. Most of these facilities also use the CO2 from the exhaust, which is treated to remove NOx, carbon monoxide (CO), and ethylene with uses a selective catalytic reduction (SCR) system, for fertilizer. The Hedera greenhouse in the Netherlands, which has operated two of the new engines since the autumn of 2007, has experienced 43.8% compared with 42.8% promised ISO efficiency. Additionally, actual NOx emissions were 13% below the TA-Luft standard that is widely used in Europe and CO and CxHy emissions also were found to be well below specified levels.
The company also released a biogas version of the new engine, which recently was commissioned in Belgium. This application uses part of the heat for the digester while the remaining heat is delivered to a nearby resort.
Designed for Efficiency, Low Emissions
Horticultural applications recently demonstrated further suitability to CHP. Two horticultural facilities in the Netherlands recently installed CHP-specialized gas engines that provide the greenhouses with CO2 for fertilizing as well as for electricity and heating.
Rose grower Baarenburg and tomato grower Prominent Kabel are utilizing J612 ‘6F’ natural gas-fueled Jenbacher engines from GE Energy for their facilities. The units reportedly feature electrical efficiency ratings of 44.1% and 44.8%, respectively. The engines are part of the manufacturer’s new ‘Type 6’ gas engines that were developed to help EU member states comply with a directive to install new industrial, commercial, and residential cogeneration systems that boost energy efficiency while reducing local fossil fuel consumption and greenhouse gas emissions.
According to the manufacturer, the 3.3-MW 6F units have demonstrated an increased output of up to 10% and a 1% increase in electrical efficiency over existing systems. The 20-cylinder J6F series provides speeds of up to 1,500 rpm and reportedly increases electrical efficiency by up to a percentage point to about 45%, depending on the application.
An optimized combustion design is intended to produce fewer uncombusted hydrocarbons. The engines operate at an effective pressure of 22 bar, which boots the efficiency. The steel pistons are designed for higher peak pressure capability than aluminum pistons. The manufacturer notes that the series has a new generation of turbochargers with a higher pressure ratio that are designed to optimize the Miller valve timing and shift the knock limit for improved combustion.
The series is based upon the manufacturer’s compact 1,500-rpm J624, a 4-MW unit that was introduced in 2008 as the first 24-cylinder gas engine for commercial power generation, particularly cogeneration. According to the company, one J624 can power about 9,000 European homes at up to 46% electrical efficiency and the unit has an overall efficiency of up to 95%. The J624 is also designed for fuel flexibility, operating on natural gas or renewable or alternative gas sources.