William Atkinson 2015-11-11 14:12:27
In recent years, turbine manufacturers have been taking a number of steps to make their equipment more environmentally friendly in terms of improved efficiency and performance, reduced emissions, and such. However, what is even bigger news is how turbines are being used as parts of larger renewable and environment-conscious projects. Examples include their use in creating energy from solar arrays—from waste gas, from biomass, and from waste coal. Turbines and Energy From Solar Arrays These days, turbines are being used more and more as integral components of solar generation and storage projects. One example is the Ivanpah Solar Electric Generating System. Located in California’s Mojave Desert, and co-owned by NRG Energy, Google, and BrightSource Energy, this is currently the largest solar generating system in the US. The energy generated at the site—which is sufficient to support the energy needs of about 140,000 homes on average, and double that when operating at maximum capacity—is being sold through power purchase agreements to Southern California Edison and Pacific Gas & Electric. The clean generation makes it possible to avoid the emissions of 450,000 tons of carbon per year. A significant part of the energy generation process at Ivanpah is three Siemens SST-900 turbines, which have a total capacity of 392 MW. Each of the three specially designed solar towers at the site holds a 2,100-ton Riley Power boiler that directs steam to one of the Siemens turbine generators, which is located at ground level. A Siemens announcement noted, “The SST-900 turbine is ideally suited for deployment in solar thermal power plants. It is known for its fast startup and shutdown capability, and the fact that it can very flexibly track the respective operating conditions of solar thermal power plants. Steam reheat enhances the efficiency of the turbine, and thus of the entire power plant.” And there are other solar projects using turbines. One is the Crescent Dunes Solar Energy Project in Tonapah, NV, which is owned and operated by SolarReserve’s Tonapah Solar Energy LLC. When the project goes online, either later this year or in 2016, the power will be sold to NV Energy. The 540-foot tower, toward which the solar panels are directed is designed to superheat salt, from 550°F to 1,050°F, and then provide thermal storage with an efficiency rate of 99%. The “active” component of the system is a 110-MW steam turbine manufactured by Alstom. Turbines and Energy From Waste Gas Another way turbines are benefiting the environment is as part of a method of transforming waste gasses into clean power. One example of this is the process created by Ener-Core, which has a technology that can capture waste gas and, using turbines, convert it into clean energy. “The process is fairly simple,” says Alain Castro, CEO. “Oxidation is a chemical reaction that happens to many compounds.” For example, waste gasses oxidize, but very slowly in the standard conditions of the atmosphere. In fact, it takes some greenhouse gasses, such as carbon dioxide and methane, between 12 and 20 years to oxidize. “However, if you can increase the temperature and pressure of the environment, almost everything will oxidize faster,” he says. Ener-Core’s technology, which focuses on low-BTU, high-contaminant waste gasses that would normally go to some form of emission destruction equipment such as flaring, sends these gasses into a pressure vessel, where the pressure is generally four to six times higher than the atmosphere with slightly elevated temperatures. “We have found the ideal combination of pressure and temperature at which waste gasses will oxidize in two or three seconds and generate heat in the process,” says Castro. Below 30%, methane can no longer be used to run an engine. Below 5 to 15%, it doesn’t even combust. Ener-Core’s pressure vessels can generate electricity at as low as just below 2% methane. This eliminates the need for flaring at industrial facilities or landfills. “Our technology is actually a replacement for the combuster of a turbine, which is what actually generates the power,” says Castro. “As such, we work with turbine companies to interface systems, which convert the heat from our vessels into electricity. We work with these companies to come up with versions of their turbines that, instead of having combusters, have our pressure vessel generate the heat.” Then, the rest of the turbine does what it was originally designed to do, which is take the heat and convert it into power. Here is the process: Emissions (low-BTU methane and oxygen) enter a heated pressure vessel, where a chemical reaction begins. Initially, the pressure vessel is heated with a small propane tank and burner, but these are not necessary once the heat-generating process to be described begins. The pressurized air reacts with the low-energy gas to release heat. A ceramic material retains and conducts the heat and sends it as heated air to a turbine, and the heated air drives the turbine. A generator then converts the mechanical energy from the turbine rotation to clean electrical power. Carbon dioxide, much less problematic than methane in terms of trapping heat, and water are released into the air. Ener-Core also works with steam boiler companies to interface with their systems, which convert the heat from Ener-Core’s vessels into steam. “The result, in both cases, is the ability to produce baseload energy,” says Castro. “Unlike solar and wind—which are intermittent—our energy is being generated 24/7, year-round.” What do customers do with the energy? It depends on their specific situation. “We believe that most of our industrial clients, such as ethanol plants and petrochemical refineries, will have onsite use for the energy, since the cost to generate this power onsite from waste gasses is less expensive than purchasing it from the local utility,” says Castro. “Probably the only clients that will sell power back to the grid are those that don’t have a need for the power onsite, such as landfills.” The Process in Action Currently, Ener-Core is working with customers at two different power station levels, and thus the company uses turbines from two different manufacturers. “When we work with smaller power stations—which are 250 kilowatts and 333 kilowatts—we use FlexEnergy turbines,” he says. Here, Ener-Core utilizes either its 250-kW Ener-Core Powerstation, or its 333-kW Ener-Core Power Oxidizer. To date, it has done two projects at this level. One was a DOD one-year pilot project. “The Department of Defense has a goal of eventually getting all military bases to be 100% grid-independent,” says Castro. “They were interested in our technology, because it is baseload, rather than intermittent.” The one-year pilot project took place from mid-2012 to mid-2013 at Fort Benning, GA. This base was selected because of its proximity to an old landfill. The project was a success, being able to generate enough renewable energy to power 250–300 homes. The energy that was produced contained near-zero emissions of NOx. “Since we were able to prove the reliability of the technology with this project, we then began to commercialize it,” he says. This led to the second project, a landfill in Schinnen, Holland, owned by Attero, the largest waste management company in Netherlands, which had just recently closed. “When you close a landfill and stop replenishing it with new waste, the quality of the gas goes way down, so most landfill projects that are generating power are active landfills or ones that were just recently closed,” says Castro. “After five or 10 years, you usually can’t generate any more power.” However, inactive landfills continue to emit methane for 50 to 60 years. The Schinnen landfill was producing methane below 30%, on which conventional gas turbines could not efficiently operate. “Attero saw our technology as a way to monetize gasses from this inactive landfill,” he says. The operation got up-and-running in mid-2014 and has already been a success. Some benefits include complete flare shutdown, the ability to process methane levels as low as 1.5%, and less then 1-ppm NOx emissions. “Attero is selling the power to a local utility,” says Castro. For larger projects, Ener-Core entered into an agreement with Dresser-Rand in late 2014. “The agreement involves the right to commercialize our technology with Dresser-Rand gas turbines for projects ranging from one megawatt to four megawatts,” says Castro. Currently with these projects, Ener-Core is installing its 2-MW Ener-Core Powerstation, coupled with Dresser-Rand’s specially designed KG2-3GEF 2-MW turbine generators. In a Dresser-Rand press release, Dan Levin, vice president, environmental solutions, notes: “The combination of reducing harmful exhaust emissions and generating clean energy from waste gases is a truly significant opportunity for many industrial companies. While most companies are focused on waste gas capture and destruction, Ener-Core’s unique gradual oxidation technology, combined with our gas turbines, will enable industrial clients across a wide range of industries to utilize their industrial waste gases to generate clean energy.” One success story is the installation at Pacific Ethanol in Stockton, CA. “This was really the first opportunity to show that we could scale the technology up from relatively small power capacities to utility-scale power capacities,” says Levin. For this project, Ener-Core developed, built, and installed two 2-MW Ener-Core Powerstations, which connected with Dresser-Rand’s KG2-3GEF 2-MW turbine generators. The 3.5-MW combined cogeneration system is replacing Pacific Ethanol’s existing use of thermal oxidizers. Pacific Ethanol expects the system to be operational by early or mid 2016. Pacific Ethanol will use the energy that is being generated to reduce its own energy bill. “The Stockton cogeneration system will replace most of the electricity we currently purchase from the grid and will reduce our energy costs by an estimated three to four million dollars per year,” says Neil Koehler, president and CEO of Pacific Ethanol, in a January 2015 press release. “The system is one of the most advanced cogeneration systems on the market, and will more efficiently deliver steam and electricity to the plant while lowering emissions. Rather than destroying waste gases, we will reuse them as a source of process energy, reducing costs and improving profitability.” Ener-Core’s most recent project is at the Santiago Canyon Landfill in Orange County, CA, decommissioned in 2004. Currently, the landfill ends up flaring about 1,000 cubic feet of methane every minute, which is generated by 23.7 million cubic yards of trash. “We expect to be able to continue generating power from this landfill for another 20 to 30 years,” says Castro. The project is expected to begin generating electricity in 2017, and Orange County is expected to be able to generate about $250,000 worth of electricity the first year. Turbines and Energy From Biomass The Elliott Group manufactures steam turbines and steam turbine generator sets, as well as compressors, power recovery expanders, and control systems. In terms of turbines, one stronghold for the company is Indonesia and Malaysia. “Almost all of our applications there are for palm oil mills,” says Scott Wilshire, manager, power generation business. “They have no source of electricity other than the turbines that we provide.” According to Wilshire, there are a few companies in the US that claim to be “zero to landfill.” However, these palm oil companies truly are. “They literally use every ounce of the palm fruits,” he says. They burn the spent carcasses of palm oil bunches and fruits to fire the boilers that make the steam to generate the power. Then, when they are done with it, they burn it again and make fertilizer out of it. The company’s turbines are also helping the environment in the US. According to Wilshire, the US power grid is migrating from a centralized model in which power is generated at large plants and then moved via transmission and distribution lines to where it is being used, to a model in which power is generated closer to the need, including a lot of actual onsite generation. While there are a lot of options for onsite generation around the country, one inexpensive and convenient option for certain companies is biomass. “In terms of onsite generation, we have done a lot of biomass projects for customers that manufacture products from wood and end up with a lot of wood scraps, shavings, and chips,” says Wilshire. “These companies burn the scraps, shavings, and chips to make steam in a boiler that generates some of their own electricity.” For some of these companies, the decision to integrate biomass may be an environmental initiative, but for most it is likely an economic issue. The reasons: Not only is it less expensive to generate their own power than to purchase it from the grid, but expenses decrease even more when these companies no longer have to pay someone to haul away the wood scraps, shavings, and chips when the piles become too high, something they had to do in the past. Turbines and Energy From Waste Coal The Elliott Group is also involved in another “green” initiative. “Western Pennsylvania, eastern Ohio, and West Virginia are populated with thousands of old coal mines, which have piles of residual coal that accumulated over the years,” says Wilshire. “It is a source of pollution, contaminating the groundwater, and, until recently, hasn’t been economically worth anyone doing anything with it.” However, the company now has a customer in western Pennsylvania, called Energy Management Concepts Inc., that offers to haul the old coal away and use it in boilers that cleanly generate steam and electricity. Energy Management Concepts provides a unique combination of heating, cooling, and electricity generation using hybrid boiler systems that burn a variety of alternate fuels including waste coal, which have a track record of providing the lowest overall long-term costs for customers. The hybrid state-of-the-art renewable energy systems ensure operational reliability, which provides insulation from power outages, while also allowing environmentally friendly, locally based alternative fuel resources to be consumed, benefiting both the customer and the environment. One of the company’s projects is the State Correction Institute-Greensburg, in western Pennsylvania, which had been built in the late 1960s. Following an earlier successful project for another state correction institution, Energy Management Concepts was approached by the director of the Pennsylvania Department of Corrections in 2004 to provide a similar waste coal-fired cogeneration response for Greensburg, for steam and electricity. “The facility’s steam host, which was the local county, told them that they were no longer going to provide them with steam, so they asked us to build a plant for them similar to the one we had done previously,” says David Goldsmith, president of Energy Management Concepts. Based on the savings the project could generate with waste coal as the main fuel, and with cogeneration to offset electricity purchases, Energy Management Concepts designed a system that was approved by the state. The new system significantly exceeds state and federal environmental regulations. The system utilizes a fully-automated mini-ICFB (internally-circulating fluidized-bed) boiler design, incorporating new technology that provides a remote operational capability in conjunction with the need for only one-person operation on a daily shift basis. The system contains one 15,000-pounds-per-hour mini-CFB coal boiler, with two 10,000 pounds-per-hour oil-fired emergency backup boilers. Two steam-driven Elliott turbines generate electricity to be fed into the prison’s electrical distribution systems. “When I needed the steam turbines, I went to Elliott, because I had been using their turbines for other projects for several years, and believe that they produced the best steam turbine in the small range,” says Goldsmith. “We have had a great relationship over the years.” The system is able to burn low-grade, low-cost waste coal and blended biomass simultaneously, with a delivered price of under $2 per MMBTU. In sum, the system can heat and cool for far less expense than high-grade coal, gas or oil, and just as cleanly as natural gas. “The cost for premium-grade coal is about $7 MMBTU, and delivered gas is $6 MMBTU today,” says Goldsmith. The system began operating in 2005. “Our technology burns waste coal cleanly, with very low emissions,” he says. As a way to meet some stringent and specific state environmental testing cycle criteria, the system also burns a minimum 15% of waste wood. “Our technology allows them to be burned simultaneously,” says Goldsmith. The system also provides continuous onsite and remote monitoring of the facility’s operation, and recording of necessary historical data. The Web-based server allows authorized engineers to carefully monitor the ongoing technical operations of the main coal boilers and the backup oil-fired boilers from a remote location. The system provides detailed reports, along with analysis and recommendations to facilitate optimized reliability and operating efficiency. As Goldsmith sees it, this new boiler system may become the standard that other nationwide coal-producing communities and state agencies emulate. With energy costs of waste coal/biomass being less than 30% of the cost of gas and/or oil (with the forecasted future prices even higher), the economics are appealing. In sum, the overall concept of a privatized thermal energy system that is owned, financed, and operated by a single entity outside the responsibility of the host facility offers multiple benefits for the customer. “Our next goal is to improve the technology to produce zero emissions, and will be first plant in the world that burn products to produce zero emissions,” he says. William Atkinson specializes in topics related to utilities and infrastructure.
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