Commercial Scale DE
Alternative fuel and technology options make onsite power an economical choice.
From reciprocating engines to fuel cells to photovoltaic cells, the choices for commercial scale distributed energy (DE) technology have never looked better. Nor has the economic argument for producing energy onsite at 1 MW and higher. In fact, though manufacturers are seeing solid sales growth, they haven’t slowed their drive for innovation and efficiency. And with the recent mergers and acquisitions by some of the world’s top manufacturers and energy companies, the investment in research and development promises even higher gains for the future.
When surveying the commercial power market, it’s hard to ignore the momentum built by GE, Fairfield, CT. And when the company makes a $3 billion bet on an industry, it’s fair to assume that the industry in question probably isn’t in question anymore. Such is the case with GE’s vote of confidence in distributed energy, as demonstrated by the recent acquisition of Dresser, Inc., a global energy infrastructure technology and service provider of compression, flow technology, measurement and distribution infrastructure, and services to customers in more than 150 countries. Dresser’s businesses will be integrated into GE’s Energy Services and Power & Water business units, and, importantly, that includes integrating the company formerly known as Waukesha Engine, a supplier of natural gas-fired reciprocating engines.
|Photo: Courtesy of Capstone
Capstone microturbines at the Center
That’s more than a strong vote of confidence, considering that Waukesha isn’t the only gas-fired engine in the line up. In 2003, GE acquired Jenbacher A.G., an Austrian manufacturer of gas-fueled reciprocating engines and generator sets. Both Jenbacher and Waukesha continue to advance their technologies. In October of 2010, Waukesha received a $6.6 million award from the US Department of Energy (DOE), to develop an ultra-clean, environmentally friendly combined heat and power (CHP) engine-generator system. Among the project’s many goals, Waukesha’s engineers aim to reduce carbon dioxide (CO2) emissions by one-third, compared to coal power plants and heat in separate, natural gas-fueled boilers.
Jenbacher continues to push the bounds of cogeneration efficiency, and one of their showcase examples is a project in France that exceeds 90% efficiency. The installation at a commercial grower’s greenhouse consists of two, two-stage turbocharged J624 engines. Each engine produces about 4.4 MW of electrical output and 4,014 kW of thermal output, for 44.4% efficiency and 47% thermal efficiency, respectively.
The design of the turbochargers is a key to the high efficiency, according to GE’s technology leader Volker Schulte. “It’s actually four turbochargers per engine with two turbochargers on the left hand bank and two on the right,” says Schulte. “You have a low-pressure and a high-pressure turbocharger, and in between you have the capability of an intercooler. You compress the air coming into the engine and cool it down, then compress it again to get higher pressure levels, and then pull it down again as it goes into the combustor.”
|Photos courtesy of Colorado State University
Colorado State University Engine and Energy Conversion Laboratory
|Dr. Bryan Wilson, professor and director at the Laboratory
With their need for heat, greenhouses offer great opportunities for natural gas-fueled Jenbacher engines, but Schulte says GE is looking to other markets with different sources of fuel, such as biogas, landfills, coal mine gas, and production gas from steel plants. Another prime market is cogeneration where the emphasis leans more to the need for heat, rather than electricity.
“The engines run on natural gas and are not just employed to make electricity, but to use heat for district heating or other purposes,” says Schulte. “For that type of application the two-stage turbocharger engine is very well suited. It has advantages, because you can choose basically between electrical efficiency or total efficiency. You can basically tune the engine to a variance where you sacrifice electrical efficiency a little bit to get a better total.” Markets include hospitals, hotels and resorts, shopping malls, or large areas where there’s a lot of heating demand.
For long-term genset supplier Caterpillar, Inc., natural gas is seen as a key to growth of the market for commercial-scale distributed energy. In March, the company announced a series of performance enhancements to gensets in the 1.2- to 2-MW range, the 50-Hz Cat G3512E and G3520E gas generator sets (1,200-kW), plus a new 60-Hz option for the G3520E (2009-kW). Designed specifically for extended-duty distributed generation and CHP Application, the enhancements feature higher power density, improved fuel efficiency, and lower operating costs.
Design improvements have reduced average oil consumption by 57%, while extending oil change intervals from 1,000 hours to 2,000. As for CHP performance, total system efficiencies have risen to 85% for the G3512E, and 87.9% for the G3520E.
The DOE would like to see GE, Caterpillar, and others succeed in developing a healthier market for cogeneration. In 1998 it launched the CHP Federal-State Partnership, and the overall CHP Program now includes accelerated research and development, technology demonstrations, and aggressive market transformation efforts. By 2009 there were 85 GW of installed CHP, representing just 9% of US capacity. The department’s goal is to boost capacity to 20% by 2030, resulting in: savings of 5.3 quadrillion BTU of fuel annually, reduced CO2 emissions of more that 800 MMT annually, and $234 billion in new investments, plus nearly 1 million highly skilled technical jobs.
Reciprocating engines will play a major role in the growth of CHP, according to Dr. Bryan Wilson, professor and director, Engines and Energy Conversion Laboratory at Colorado State University. The Engines and Energy Conversion Laboratory is a comprehensive research/teaching facility, with emphasis on engines, fuels, and energy conversion technology. “Right by my office is a 1.8-megawatt Caterpillar 3516 engine, and we’re working with them on next-generation technology for their gas engines for distributed generation. We’ve done similar work with Cummins, Waukesha, and every engine on the US pipeline system,” says Wilson. The laboratory opened in 1992, and over the years it’s built an impressive record of research that has earned continuous support from the natural gas pipeline industry.
“Natural gas is literally methane,” explains Wilson, “but what people don’t recognize is that methane or natural gas is probably our most renewable fuel. Almost any organic compound can be treated with an anaerobic process, and you get anaerobic digestion and you have methane. Of course that’s what happens in landfills and waste treatment plants, and industrial processes. ”
To get a maximum return on the natural gas—or methane, as the case may be—Wilson’s team is exploring some cutting-edge technology. For example, variable valve timing. He says, “The technologies are available now to allow us to either use mechanical controls to vary intake and exhaust valve timing, or go all the way to direct hydraulic actuation, which gives us tremendous control and ability to optimize the cycle.” Also, there’s research for an entirely new approach to fuel ignition. “We’ve been working on laser ignition using focused lasers instead of spark plugs to ignite the mixture. It sounds like Star Wars, but it actually has a significant combustion advantage, and it looks to be commercially realizable.”
The University of North Dakota is another stage for ongoing research in engine and energy technology development. Much of the research is taking place under the auspices of the Energy & Environmental Research Center, a nonprofit organization chartered to develop and commercialize innovative technologies. According to Paul Stohr, director of Energy Solutions Business at Cummins Power Generation, Fridley, MN, the center is helping Cummins develop new solutions to handle challenging fuel stocks, such as railroad ties.
“Railroad ties are a very nasty feedstock, but the center has some gas-fired technology that can consistently control gas quality, and then deal with the contaminants,” says Stohr.
Much of the growth in CHP will come from its adaptability to use a variety of fuel sources, notes Stohr. “Look at biomass, gasification, and other ways of producing gas from organic materials, and we’re seeing lots of applications for industrial byproducts from areas such as pharmaceutical manufacturing processes.”
One of the challenges with biomass and other forms of gasification is the labor-intensive process of gathering enough feedstock to produce a minimum of 1 MW. The problem has prompted Cummins to look at technologies such as pyrolysis and other feedstocks, such as municipal solid waste, industrial wastes, and plastics. Stohr notes, though, that new fuel stocks come with some new challenges.
“The plastics are effectively long chain hydrocarbons and pyrolysis can break them down into something that reasonably resembles some of the more traditional nonstandard gases that you see,” he explains. “When you get into pyrolysis and biomass gasification, a lot of these industrial byproducts get their heat content from hydrogen. From a technology development standpoint, there’s some challenges as to the combustion characteristics of hydrogen. We have developed some test facilities that can blend of hydrogen and carbon dioxide and propane so we can mix fuels to simulate what we’re seeing in industrial applications.”
Mixing fuels and biofuel generation is becoming a standard operation for wastewater treatment plants, such as Columbus Water Works in Georgia. At Columbus, Cummins Commercial Projects recently provided a dual-fuel solution using digester gas and natural gas. Two Cummins 1750-kW QSV 91 generators were installed, facilitating heat recovery through high-grade and low-grade hot water, as well as continuous baseload generation.
Wastewater treatment plants are also seen as a prime market for fuel cells, and FuelCell Energy, Danbury, CT, recently won a contract to supply a 1.5-MW, DFC1500 power plant at a CHP facility at the San Jose/Santa Clara Water Pollution Control Plant in San Jose, CA. Before the addition of the fuel cell, about two-thirds of the energy used by the 11-MW facility came from methane derived from digester and landfill processes.
Another market for fuel cells are university campuses. FuelCell Energy has a unit at California State University Northridge and recently sold a DFC1500 to California State University, San Bernardino. In 2010, the California Public Utilities Commission authorized two California utilities to pursue utility-owned fuel cell installations at state universities as part of a drive to adopt clean fossil fuels for distributed generation. But the trend isn’t limited to utilities and universities.
In September 2010, Adobe Systems Inc., San Jose, and Bloom Energy Corp, Sunnyvale, CA, announced completion of Bloom’s largest installation to date—a total of 12 Bloom Energy Servers that will supply 1.2 MW, or about 30%, of Adobe’s power requirements. Adobe, eBay, and Google have purchased Bloom hardware at prices reported to be about $800,000, but in January of 2011, Bloom shifted its business model from selling energy servers to selling energy, via the new Bloom Electrons service. Electrons customers include Walmart, Coca-Cola, Staples, Kaiser Permanente, and the California Institute of Technology. Bloom’s Electrons program is based on a 10-year contract, and customers buy electricity at a 20% discount from utility prices, without upfront capital expenses. Bloom has partnered with Southern California Gas Co. for natural gas, and Adobe plans to purchase methane through a five-year contract with a Pennsylvania landfill.
At a commercial scale, fuel accessibility and economics drive power technology decisions, and it was a key factor at a remote ski resort in Russia where 38 microturbines generate 2.32 MW of CHP, enough to provide all of the resort’s power needs. The setup consists of thirty C60 and eight C65 microturbines from Capstone Turbine Corp., Chatsworth, CA. The resort’s location made it economically unfeasible to run a grid transmission line or a natural gas pipeline, but liquefied methane—with liquefied propane-butane as a backup fuel—offered an economical alternative. Officially in operation since 2008, the resort reports 100% reliability since commissioning.
According to Valeriy Ignatenko, chief power engineer at Sport Center Igora, low emissions and noise levels, plus low-maintenance costs and reliability, made the microturbines an ideal fit for the resort.
Low emission specifications are having an impact on much of the market for distributed energy, and the air quality issue is especially important to the California Energy Commission (CEC), as demonstrated in a project with Tecogen Inc., Waltham, MA. In August 2011, Tecogen launched the InVerde Ultra 100 (100 kW), with the CEC’s backing as a solution for distributed energy users intending to meet—and exceed—the strictest California emission standards. The company’s InVerde Ultra is a natural gas engine-driven CHP unit, designed with a modular approach that’s intended for scalable distributed power generation.
Modular scalable units are finding favor in many distributed energy settings. Tecogen’s InVerde 100 (predecessor to the Ultra) was chosen by a Brooklyn, NY, pharmaceutical packaging company as a solution to their high energy costs. The company needed security against blackouts and liked the InVerde’s utility-friendly interface, because the local utility, ConEd, is particularly sensitive towards new generation on the grid. Power demands at the location require 1.2 MW, and a system of twelve 100-kW units offered a high level of built-in, inherent redundancy.
Moving up the ladder of lower emissions, it’s hard to beat photovoltaic (PV) solar panels. Schneider Electric, Palatine, IL, sees a strong future in the technology, as evidenced by its acquisition of Canadian inverter manufacturer, Xantrex Technology, Inc. Xantrex earned top status as global supplier to the solar and wind inverter market. As a showcase for both inverters and PV, Schneider recently launched a 1-MW dual-voltage solar farm at its manufacturing plant in Smyrna, TN. It’s the first dual-voltage solar farm in the US and spans 6 acres, with Schneider’s solar inverters, transformers, and panel boards, and it is expected to generate about 1.3 million kWh of electricity per annum. The investment is totaled at US $6.25 million, with this figure being supplemented by a 30% federal tax credit.
According to Ed Willhite, facility manager at the Smyrna plant, Schneider expects the project to supply about 25% of the plant’s energy. The project is part of the Tennessee Valley Authority’s (TVA) Partners Program, and 100% of the power is sold back to the TVA, along with renewable energy credits. “We want to make this a learning lab to test our converters, DC [direct current] switchboards, and equipment that we bring to the market so we could test them in a real-life working environment,” says Willhite. “As a result of that, we can understand the different between 600 volts and 1,000 volts, and we have different kinds of grounding in the field to test inverters and positive, negative, or no-ground situations.”
One benefit of operating at 1,000 V is efficiency. The higher voltage allows for up to 40% fewer parallel connections than using 600 V, leading to a reduction of the energy lost to resistance.
Ultimately, higher efficiency at all levels of technology looks to be an all-consuming trend with commercial scale power providers. And the results are impressive, but there’s even more to come in the future. For example, microgrid technology received a major boost in August, when two major companies, Boeing and Siemens, announced an alliance for the joint development of smart grid technologies to improve energy access and security for the US Department of Defense. The goal is to provide US military applications with secure microgrid management solutions that lower cost and increase efficiency.
The use of hi-tech batteries in microgrids also saw a boost from the military. This time, it was the US Navy that ordered a 1,000-kWh/500-kW-rated energy storage system for use in a microgrid application at the San Nicolas Island Naval Facility. The system will utilize a product from ZBB, Milwaukee, WI. It’s the company’s newly branded EnerSystem technology, and it uses next-generation Zinc Bromide flow battery modules. The system will be tested and certified to maintain power quality and perform load management for off-peak produced power of the wind turbines and diesel electric power plant power delivery system for the microgrid.
Taking a step further out into the future, researchers at Sandia National Laboratories are ready to demonstrate a liquid CO2-fueled Brayton Cycle turbine that’s expected to achieve a 50% improvement in thermal-to-electric conversion efficiency over the current generation of steam turbines at nuclear power plants, which the Braytons are targeted to replace. Of course, nuclear power plants are a leap up from distributed energy, but adapting the technology to smaller applications makes sense. The Brayton design offers an increase in power per unit of fuel that can exceed 40%, and Sandia researchers describe the design as similar to the turbines in today’s jet aircraft.
All told, commercial power for distributed generation has a foundation of solid support from current technology, and continued research and development promise even higher efficiency and productivity for the future.
Author's Bio: Writer Ed Ritchie specializes in energy, transportation, and communication technologies.