Exergy recovery from LNG-regasification for polygeneration of energy

Identifier:  TDX:3243

Handle: https://hdl.handle.net/20.500.11797/TDX3243

Authors:  Atienza Márquez, Antonio

Abstract:
Liquefied Natural Gas (LNG) is a premium-quality physical exergy source because of its cryogenic temperature and usually high regasification pressure. But although this exergetic potential can be utilized as a regasification by-product for multiple applications, it is rarely used because of several barriers such as low efficiencies and limited economic competitiveness of the proposed systems. Additionally, the solutions proposed to boost efficiency generally require very complex structures and huge capital investments. The objective of this doctoral thesis is to develop innovative and sustainable polygeneration systems to harness the physical exergy of LNG (and other cryogenics fluids such as bio-LNG) with a competitive efficiency-complexity ratio both in large-scale and satellite regasification facilities. The different configurations proposed consist of non-combustion systems that regasify LNG and produce electricity and/or refrigeration at different temperatures.The results obtained showcase that polygeneration is an economically feasible technical solution to squeeze the LNG physical exergy efficiently in cascade. Besides, a remarkable finding of the thesis is the suitability of natural fluids as working fluids and heat transfer fluids for such kind of systems. The configurations proposed for large-scale receiving terminals can achieve double the efficiency of current cryogenic power plants, and an equivalent electricity production up to 150 kWh per metric tonne of LNG regasified. As for the economic performance, a base-case payback period of five years is estimated for the polygeneration configuration with the most efficient performance among the investigated in this thesis. Finally, in certain scenarios satellite plants are an attractive gateway to the integration of cryogenic biofuels in the energy mix for the recovery of the low-temperature heat from the regasification.