Daniel P. Duffy 2015-06-09 11:31:28
People living in a golden age usually don’t realize they are living in great times. We are very adaptable, and usually take even major changes and improvements in stride. And we are definitely now in a golden age of high-tech communications. As someone old enough to remember dial telephones wired into the kitchen wall, I think to myself about how amazing is the smartphone that’s in my pocket. Renewable energy is also taking off, which allowed the world’s economy last year to grow, without increasing greenhouse gas emissions. It could also be argued that we are living in a golden age of distributed energy. There have been significant advances in technologies of battery storage, cogeneration, photovoltaic solar cells, wind turbines, alternate fuels, smart grids, gensets, and engines. Now, while improved generator efficiency may not sound very sexy or high tech, it can save an office building tens of thousands of dollars each year. And, it can save a nation’s economy billions of dollars annually. So, though updated gensets may not make headlines like the debut of a new electric self-driving automobile, an improved genset can make a significant difference to a business’s ability to operate, as well as to its bottom line. Gensets and Engines: What Do They Do; How Do They Operate? “Genset” is short for “engine generator set.” These portable power sources have three main parts: • The electrical generator is the source of the electrical power produced by the genset. • The reciprocating engine drives the generator: The engine is mounted together with the electrical generator as one complete power unit. The engine, itself, is typically an internal combustion engine, with some gensets utilizing turbines to drive the generators. • The fuel powers the engine and its storage tank: larger gensets typically use diesel fuel, while smaller gensets use gasoline, though other fuels such as natural gas, propane, biodiesel, hydrogen, and even sewer gas can be used. Actually, the entire unit is typically considered to be a specific type of portable single-phase generator. These can vary in size from handheld models for emergency home use or recreational activities, to larger trailer-mounted units hauled to sites by trucks. Larger, immobile, three-phase generators are not considered to be gensets. (Even though the general configuration—generator, power source, fuel—is identical.) Auxiliary Systems and Regulators In addition to its main components, there are multiple auxiliary systems required for the operation of a genset. These include (but are not limited to): automatic starting switches, a speed regulator (or governor), a voltage regulator, coolant system, exhaust vents, an engine lubrication system, a battery starter for smaller gensets, and compressed air starters for larger ones. Specially pre-positioned gensets come equipped with starting switches that automatically cut the power from the grid to the genset when a power failure occurs. Speed regulators keep the engine speed constant, typically by limiting the amount of fuel and air fed to the engine. This is of vital importance in an electrical power-generating operation. By keeping the speed of the engine constant, the regulator keeps the power output, voltage, and frequency of the electricity generated constant as well. There are three main types of regulators: electro server, pneumatic, and centrifugal. An electronic servomotor is equipped with an electronic module that measures engine speed by counting the frequency of spark plug discharges. Using the feedback from this measurement, it sends proportional voltage back to the servo to control engine speed. A pneumatic regulator measures an engine’s exhaust air stream. Again, using a feedback mechanism, it adjusts the engine carburetor’s intake throttle. It continues to increase and decrease air flow proportionally until equilibrium is reestablished. The simpler centrifugal regulator utilizes a flyweight linked by a spring mechanism to a rapidly rotating axle. The centrifugal force generated by the rotating axle causes the weights to move outward or back in towards the axle depending on engine speed. This movement adjusts engines speed via a leveraged linkage mechanism. Diesel Versus Gasoline Fuel Gensets tend to be powered by diesel engines instead of gasoline engines. There are several reasons for this. The fuel consumption of a diesel engine is approximately half that of a gasoline engine. As a result, the same amount of energy can be stored in a much smaller and compact diesel fuel tank. This is a significant advantage for potentially portable gensets. Diesel engines tend to be safer since they don’t use a spark plug to ignite the fuel mixture. In diesel engine, combustion occurs as part of the compression process itself. Without a spark there is less danger of an accidental explosion. Compression ratios for diesel engines are higher (up to 25:1 for diesel versus a maximum of 12:1 for gasoline). As a side benefit, diesel engines are built more ruggedly to withstand these high internal pressures. Diesel operations, therefore, are likely to be more efficient and typically deliver 25–30% better fuel economy than similarly performing gasoline engines. Since gasoline engines tend to be more complicated and run hotter than diesel, they often suffer greater wear and tear over time. Diesel engines will tend to have lower overall maintenance and replacement parts costs. Despite these disadvantages, gasoline remains the preferred choice in America for personal transport, and is used by most automobiles and utility trucks. Gasoline is usually much cheaper per gallon than diesel fuel. Gasoline engines also tend to be less noisy. These same advantages have allowed gasoline-powered gensets to carve out a section of the portable power market for themselves. The oil and fuel industry itself benefits from the use of gensets. Dresser-Rand is one genset supplier whose products and services are used for a wide range of applications in the oil and gas industry, as well as power generation and its associated technologies (biomass, waste-to-energy, CHP/cogeneration, marine propulsion, marine auxiliary power generation, and compressed air energy storage). A perfect example of the crossover capabilities that allow them to utilize gensets to service the oil and gas industry would be Dresser-Rand’s recent project in the Anzoategui area of Venezuela. A region noted for its rich deposits of oil and natural gas, the associated petroleum gas produced during extraction operations was used as fuel for power generation. The company provided 150 containerized gensets with Guascor SFGLD 560 engines, basic engineering, voltage transformers, MT transfer switches, PLC controls, installation materials, and equipment for this project over a phased period of time. The units have been configured to use venting gas that is extracted from nearby oil wells, putting to work what was once a waste byproduct to generate 112.5 MWe of electrical power. Genset Technology Advances Genset technology continues to improve along the lines of ever-greater efficiency, safety, environmental protection, and ease of use. Let’s begin with the fuel itself. Traditionally, diesel fuel tended to have high sulfur content. This resulted in a less clean burn and the production of greater amounts of post combustion. As a result of EPA mandates published in 2006, a new kind diesel fuel has been reformulated with sulfur content as low as 15 parts per million (ppm). This “Ultra-Low-Sulfur-Diesel” fuel meets these more stringent emission standards. In addition to improved fuel, the diesel engines powering gensets also have achieved greater fuel efficiencies. Newer diesel engines have pre-chambers and combustion chambers that have been modified to maximize combustion and minimize noise. Combustion efficiency is a function of how small and widely distributed the droplets of fuel are that are injected into the pre-chamber. By properly sizing and reconfiguring the chamber, the desired physical distribution of fuel can be achieved. Not just improved fuels, but alternate fuels are finding a place in genset operations. A leader in these technological advances is MTU Onsite Energy who manufactures and services both diesel- and gasoline-powered gensets. MTU is one of the core brands of Rolls Royce Power Systems AG, a worldwide provider of high-speed and medium-speed diesel and gas engines, complete drive systems, distributed energy systems, and fuel injection systems. It provides a wide range of power systems; mission-critical; standby power; and continuous power, heating, and cooling. The product line includes diesel gensets up to 3,250 kW, gas-powered cogeneration systems up to 2,500 kW, and gas turbines up to 50,000 kW. The company continues to develop further advances in genset technology by developing sustainable alternatives, with systems that produce greener energy from climate-neutral, regenerative fuels, combined heat and power (CHP) plants, biogas, landfill gas, or sewage gas. As mentioned above, diesel engines tend to be noisy (especially at start up), so sound reduction is an issue. To minimize noise, redesigned pre-chambers come lined with sound attenuation pockets. Like the recessed pits in sound muffling materials, these pockets are sized and spaced to attenuate shock waves from the combustion detonation. Additionally, these pockets can be filed with porous, metallic, or ceramic pellets. Physically, these pellets act to further absorb sound waves, while their metallic coatings act as a catalyst to further improve combustion rates. Once combustion has been achieved, its byproducts have to be dealt with. While low-sulfur fuels burn cleaner, the engine’s exhaust system can be further modified to reduce air-borne pollutants. Exhaust gas recirculation (EGR) is one such technique to lower nitrogen oxide (NOx) emissions. EGR recirculates part of the exhaust back into the engines combustion chamber to mix with the incoming air. As a result, the adiabatic flame temperature is reduced while the heat capacity of the fuel/air mix increases. This allows combustion to occur at a lower temperature, which reduces NOx formation (without reducing the amount of available oxygen). Another method of reducing NOx emissions is the use of selective catalytic reduction (SCR). Exhaust gases pass through a reducing catalyst such as aqueous ammonia. The resulting interaction converts NOx into nitrogen and water. An industry leader in managing genset emissions is Cummins, whose engines are noted for their superior exhaust controls. Cummins Bridgeway is the Cummins distributor responsible for the sales and service of Cummins engines, power generation equipment, and related products in Michigan, Ohio, and Western Pennsylvania. It serves multiple markets, including industrial, automotive, agricultural, marine, RV, mining, construction, military, bus, rail, oil and gas, and power generation. The company’s gensets are designed to start up and assume load in less than 10 seconds, and rated load in a single step. The diesel gensets have been utilized at utility peaking plants, distributed generation (DG) facilities, peak shaving, and power management at large commercial or industrial sites. Each unit can be equipped with optional factory-integrated exhaust after treatments to reduce emissions during high-hour use. Gensets range from 7.5- to 25-kW air- and liquid-cooled diesel generator sets, 35- to 500-kW diesel-fueled generator sets with Power Command control systems, and 600-kW to 2.7-MW units. Improved emissions are often the byproduct of improved operating efficiency, as evidenced by the performance of Caterpillar gensets. As part of the Caterpillar dealer network, Northeast CAT Dealers has access to a large rental fleet of power generation and temperature control equipment. This equipment is specifically designed to meet the requirements of commercial, industrial, institutional, and manufacturing applications. The company’s gensets range in size 6–14,040 ekW (7.5–17,550 kVA) of power potential. These units are built for high efficiency, low fuel consumption, and global emissions compliance (equivalent to US EPA Tier 2 or Tier 3 non-road emissions standards). There is also a range of options of these generator sets. Harco Manufacturing is a leading fabricator of premium engine exhaust silencers for diesel engines along with a complete line of supporting products. The company produces the HAPCO line of exhaust silencers, third-party diesel oxidation catalysts, and diesel particulate filter systems, diesel engine exhaust spark arrestors, and other related emission control products. Improvements in how the fuel is introduced into the combustion chamber are also areas of technical advancement. Common rail fuel injection (CRF) injects fuel stored in tanks under high pressure into individual solenoid valves. Since this process is electronically monitored it allows for greater control over the timing of combustion (with as much as five separate injections per combustion cycle) and the quantity of fuel injected with each cycle. The high-pressure further improves efficacies by homogenizing the air fuel mixture to a much greater extent. Electronic digital controls have also begun to supplant traditional analog controls. Analog controls cannot handle the requirements of critical facilities and their complex power backup and distribution systems. Analog controls are applicable for simple or small facilities, but digital is preferred for systems having both non-linear and linear load requirements. Advanced digital controls also provide feedback, reporting the status of their system components in real time while displaying this information on computer monitoring screens. Yet, gensets with traditional analog controls retain a significant portion of the genset market. Taylor Power Systems Inc. manufactures industrial-sized diesel and natural gas generators, for a wide range of applications. The generators range in size from 9 to 2,000 kW. Taylor generators are used by industrial, commercial, agricultural, and residential customers. In addition to standard models, the company can design, engineer, and manufacture custom-built generators tailored to meet specific power needs. The mobile generators range in size from 20 to 500 kW, and are powered by mobile EPA-certified engines. These gensets also come with DOT-rated integral tank trailers, heavy-duty weather enclosures, critical grade exhaust silencers, and full output circuit breakers. Instrumentation and control is provided by an analog control panel. Electronic controls can be used for controlling performance, as well as tracking performance. As one of the largest rental companies in the US, Sunbelt Rentals provides gensets to a wide variety of customers (commercial, residential, industrial, municipal, and specialized service industries) from over 450 locations nationwide. In addition to gensets, Sunbelt’s product line includes general construction equipment, industrial tools, pumps and large power generation equipment, trench shoring, scaffolding, remediation, and restoration equipment. Ranging in size from 2.5 to 10 kW, these gas portable generators are suitable for powering 120/240-V power tools, lighting equipment, fans and blowers, and such. All models come with automatic idle control resulting in greater fuel economy and reduced noise levels. Roll cage steel frames and shock mounting are standard to provide durability during operations and help ensure on-the-job performance. A further advantage is that digital controls allow for remote monitoring via SCADA systems. SCADA is an acronym that stands for “Supervisory Control and Data Acquisition.” SCADA gathers real-time data on the operations of mechanical and hydraulic systems and allows for remote control of these systems from a central remote operator (though some SCADA systems merely monitor without allowing for control). The result is an information feedback loop where data from current operations guides the control changes needed to optimize or modify these operations, which in turn generates a new data set describing these operations, that can lead to further control changes. For over 15 years, OmniMetrix Inc. (an Acom Energy Inc. company) has been a leader and pioneer in wireless remote monitoring, control, and diagnostics for emergency power generator systems. The systems have been proven to make emergency power systems more reliable. Omnimetrix’s innovative technology includes the introduction in 1998 of the first wireless remote monitor for onsite power generation. In 2012, the company joined with Nixon Power Services (the world’s largest Kohler generator distributor headquartered in Nashville, TN) to supply one of the largest regional supermarkets in the US with backup power supply monitoring capabilities for their generators. “Recent utility grid failures on the East Coast of the US emphasize the need for reliable backup power for a myriad of facilities. Sustained loss of power accompanied by failed backup power would pose a risk to shoppers and significant financial loss for the stores that OmniMetrix will be monitoring,” says Deena Redding, former president. “This order, and the connections it constitutes, validate the recent change in our business model that emphasizes growth by connection volume and recurring revenue versus sales of individual units.” In addition to the engine powering the genset, there have been recent advances in the generators themselves, involving inverter technology. A standard inverter converts direct current (DC) power from a battery, solar cell, or fuel cell into alternating current (AC) power by means of properly configured electronic circuitry. The resultant AC power can be of the necessary voltage and frequency required by the equipment, homes, and businesses utilizing the energy. An inverter generator, on the other hand, uses advanced electronic circuitry that initially produces electrical power output that starts as basic three-phase AC, gets converted to DC, and then gets inverted back into single-phase sine wave AC. Despite, or perhaps because of, these advances, there remains a strong showing in the market for traditional firms that have been supplying gensets for decades. They have done so by remaining agile, staying ahead of the technological curve, and supplying ever-improving gensets to their customers. Take for example Girtz Industries. Since 1963, Girtz Industries has been a designer and manufacturer of power modules and enclosures for gensets, chillers, boilers, and switchgear for turnkey power packaging solutions. Their Z-CUBE ISO containerized packages house gensets from 400 to 2,250 kW. All packages utilize a similar mechanical and electrical design resulting in a consistent look and feel for the operators and service technicians. Nearly as old, Kraft Power Corporation is celebrating 50 years in the power generation industry. Since 1965, Kraft Power is one of the major providers of CHP systems, emergency/standby generators and power systems, power transmission products, and diesel and gas engines, including parts and accessories. The company’s CHP modules are suitable to operate on natural gas, digester gas, as well as landfill gas. These CHP modules are designed and built with long-term success and durability in mind. They use only the highest-quality industrial grade components, carefully selected to result in a highly efficient system that provides clients with maximum uptime and reliability, along with industry-leading performance. Kraft Power also specializes in servicing CHP systems in the Northeast and Midwest, and offers long-term service agreements for CHP modules, using their own service teams (not sub-contracting), located in New York, New Jersey, Massachusetts, Ohio, Michigan, North Carolina, Georgia, and Texas. Their unique commitment to CHP service is backed by extensive inventories of service parts, technical staff, and component repair capabilities. Kraft Power builds long-term serviceability into all of their products. The products can be custom designed and manufactured for customers’ specific needs. One company in particular has tracked the changes in the industry, keeping pace with customer needs. In the past 30 years, gensets were often shipped as skid-mounted units with the radiators and the switchgear included but not connected together. Upon arrival, the genset and switchgear would typically be installed inside a building. Then, the radiators would be mounted outside of the building to maximize heat dissipation rates. Meanwhile, the paralleling switchgear (the gear that electrically “locks” the generator unit to the electrical utility) would be installed in a separate climate controlled room. Complete installation would require the services of an electrical and plumbing contractor. Only then would the vendor come to the site to do a commissioning startup. Martin Energy Group of Martin Machinery followed this basic approach, manufacturing electrical power systems powered by innovative internal combustion engines fueled by waste gas. These systems vary in size from 40 to 1,300 kW and are designed to parallel to the electrical utility, a setup that stabilizes electrical production and allows the user to sell electricity back to the utility. Martin Energy and the market has moved more to “walk-in” type enclosures. These have the advantage of being more like a “plug-in-and-play” system, which reduces labor costs at the job site. These modular units also allow for faster depreciation than a “site built” building and are easier to resell since they are self-contained systems. Daniel P. Duffy, P.E., is a frequent contributor to Forester Media publications.
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