Building a Better Turbine
Waste gases are a problem. If vented or flared without being properly treated, they contribute to pollution and global warming. Conditioning them to be disposed of properly is expensive, however.
The problem would be solved if a way is found to use the dirty and diluted gases to produce the heat that is necessary to generate the electricity that drives turbines and other equipment. Indeed, such a solution would provide a double benefit: The dangerous gases would be eliminated — and in the process a worthless commodity would be transformed into one with value.
Ener-Core, which is based in Irvine, CA, thinks it is doing just that. In traditional gas-fed turbines, energy in the form of heat is released when the gas is ignited. The combustion really is the oxidation of the gas. The heat produced is used to generate. Ener-Core’s Power Oxidation, according to CEO Alain Castro, achieves the key step — generating heat — without the combustion. The bottom line is that the absence of combustion makes the contaminated and weak gas a viable energy source.
The Ener-Core approach uses lower levels of heat and pressure exerted in a precise, software-controlled manner to trigger the oxidation process. The software adjusts the heat/pressure mix to the composition of the waste gas being processed. The result, according to Castro, is that oxidation and the heat it generates occurs almost instantaneously. “We found that if you control the temperature and the pressure it turns out that what at normal atmospheric conditions takes 15 years can be done…in one second,” Castro said.
Castro claims that the process is cheaper than traditional approaches because 60 percent to 70 percent of the cost of generating electricity from gas is to pay for the used to trigger combustion. That cost is reduced in Ener-Core’s approach simply because there is no combustion. “You kill two birds with one stone,” he said. “You get cheap onsite energy and drastically reduce waste gas emissions.”
Power Oxidation systems can be positioned to be the power source for cogeneration systems that today are often fueled by natural gas. The system is installed — or soon will be — in several places. Castro said that Siemens’ subsidiary Dresser-Rand has sold two 1.8 MW systems to Pacific Ethanol, which is headquartered in Sacramento, California. The systems are expected to generate 3.5 MW of power for the landfill and save $3 million to $4 million annually, Castro said. The savings come from a couple of sources: The company will reduce or eliminate the power they buy from the utility by the cogeneration function and no longer will have to pay to have waste gas destroyed.
The units, which are not appropriate for retrofit, carry a cost premium of 30 percent 50 percent over traditional turbines. They come in 250 KW and 1.8 MW versions. Castro said that it is impossible to determine precise return on investment (ROI) figures for the systems because savings are dependent on the price of electricity that the facility is paying.
In general, however, Castro says 2.5 years is a reasonable estimate in places, such as New York and California, where power is relatively inexpensive. Hawaii – which has very high energy prices – could lead to an ROI as short as one year. The approach breaks or reduces – if the facility doesn’t use the system for all its energy needs – the uncertainty caused by energy price fluctuations, Castro said.
Building managers need about a day of training on managing the Power Oxidation process, Castro said. The footprint of the units are the same as traditional turbines, but they are significantly taller.
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