Effective utilization of liquefied natural gas for distributed generation
Alexandrou, Andreas N.
PublisherNova Science Publishers, Inc.
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Liquefied natural gas (LNG) is considered a safe and transportable fuel and could become a fueling option for distributed generation applications, particularly in locations which are situated far from centralized power plants. Depending on the location and the related needs in energy type, these systems could vary in size, technology (e.g., gas turbine, steam turbine, gas engine), and useful energy generation (i.e., heat-and-power, cooling-and-power, cooling-heating-and-power). In the case of a trigeneration, i.e., cooling-heating-and-power, system, the more appropriate technologies are gas turbine and the gas engine, with the former being more favored for larger-scale power production (5+ MWe), and the latter being favored for smaller-scale systems (0.5-2.5 MWe). For such systems, a thermally-activated cooling plant must be coupled to the exhaust streams of the gas turbine (or gas engine). The absorption chiller can be set to produce only useful cooling (in the form of chilled water), or modified to also generate useful heating. Alternatively useful heating can generated from heat recovery in a heat exchanger. Heating and cooling (hot water and chilled water, respectively) can be then distributed through a district energy network to nearby buildings to fulfill local demand. In terms of electricity production, the system can generate electricity very efficiently due to the technology utilized, but also transmission and distribution losses (in comparison to a centralized power plant) to the network grid are eliminated. Additionally during the regasification stage of LNG, the cooling energy can be recovered to cool the air stream before compression in the air compressor (in the case of a gas turbine cycle). In this manner, the thermodynamic efficiency of the cycle, and thereby the net electrical efficiency, is improved, since less power input is needed in the compression stage. Alternatively, when LNG is available in larger quantities, the cooling energy in LNG can be utilized in the district cooling network. This also improves system efficiency, since less fuel is needed to produce cooling. In this study various analyses are included, namely energy analysis, exergy analysis, cost analysis, and thermoeconomic analysis. The results show the potential of the system in terms of efficiency maximization (system efficiency, utilization of fuel), reduction of greenhouse gases, and minimization of running (fuel) costs and energy losses. © 2015 Nova Science Publishers, Inc.