Degree of Achievement of the Thesis Aim
Through accomplishment of the seven thesis objectives, the aim of the design, development and testing of an efficient and effective SOFC liquid desiccant trigeneration system has been successfully achieved. The novel system is truly multi-functional, designed to provide the energy needs of a building throughout all seasons. The system increases the utilisation of thermal energy from the SOFC during periods of low/no thermal demand, to provide a comfortable indoor building environment through dehumidification/cooling. Theoretical and experimental methods have been adopted in order to carry out a rigorous and analytical piece of work. The thesis has proved, both theoretically and experimentally, the novel tri-generation system concept. The relationship between SOFC and liquid desiccant component operation and tri-generation system performance has been documented. The climatic, economic and environmental conditions in which the system performs best are provided, and recommendations for future work in order to improve system performance have been discussed.
The thesis has been approached in a systematic and logical manner, with research integrity demonstrated throughout. As highlighted in the approach taken to the review of the literature presented in Chap. 2, the novel nature of the developed tri-generation system means there is no previous work directly related to it. It is therefore proposed that the thesis provides a clear contribution to new knowledge, and provides a step forward in the area of low carbon sustainable energy conversion techniques for building applications. Although there is no work directly relating to the thesis topic, it is suggested that the presented work builds upon the following fields of research; small (micro) scale tri-generation systems, particularly those adopting fuel cell (SOFC) technology and the application of liquid desiccant air conditioning in small (micro) scale tri-generation systems (Huangfu et al. 2007; Pilatowsky et al. 2011; Jradi and Riffat 2014c; Wu et al. 2014; Buker et al. 2015).
To summarise Sect. 9.2, the thesis presents the following general conclusions
with respect to the novel SOFC liquid desiccant tri-generation system:
- • SOFC and liquid desiccant air conditioning are an effective technological pairing. High tri-generation efficiencies, particularly in hot and humid climates, are demonstrated.
- • Appropriate matching of component capacity is necessary. Overall tri-generation system performance is more influenced by the SOFC component than the liquid desiccant.
- • It is primarily the optimisation of the liquid desiccant component that facilitates effective tri-generation system integration and operation. The inclusion of liquid desiccant can bring significant improvement to system performance.
- • The developed SDCS shows significant potential for integration with other CHP prime mover technologies (ICE, SE), with likely improvements to the reliability and economic performance.
- • The novel tri-generation system can effectively provide electricity, heating or dehumidification/cooling from a single fuel source. Distribution losses are eliminated.
- • Nonsynchronous operation is a particular advantage specific to a SOFC liquid desiccant tri-generation system. Thermal energy storage in the form of concentrated desiccant solution has the potential to bring about improvements to system performance.
- • The concept has been proven at a small capacity but it is easily scalable.
- • SOFC can internally reform natural gas, therefore reducing system complexity and demonstrating the simplicity of tri-generation system integration into current markets where natural gas distribution is widespread. Furthermore, the developed tri-generation system demonstrates great potential for decentralised locations where electrical grid connection is unavailable.
- • Economic performance is questionable. This is anticipated to improve with SOFC capital cost reductions.
- • Favourable environmental performance is demonstrated, with the potential for zero carbon operation with the transition to a pure hydrogen fuel.
Section 9.2 has re-visited the thesis aim and objectives and critically examines the
degree to which they have been fulfilled. Next, Sect. 9.3 presents the thesis recommendations for future work.