| dc.description.abstract | Current technologies of using conventional energy produce a large amount of waste heat which can potentially be recovered in the form of useful work to use in our day to day life. This initiative not only optimizes the energy usage but also contributes to mitigating
environmental impact of fossil fuel. There are also two main sources of renewable energy, solar and geothermal that can be used as an alternative to fossil fuel based options. Harnessing of this energy with appropriate low cost technology could be a promising method of alternate energy utilization. However, there are some developed
technologies which are already in use to generate medium to large scale of power or power and heat (co-generation). But small scale trigeneration with a single source of energy has not yet been developed. In this research work a small scale trigeneration
system is designed, built and experimentally investigated for simultaneous generation of power, heating and cooling.
This integrated system combines a power and cooling cycles where the source heat is used to generate power through a scroll expander and a portion of the heat is used in an ejector cooling system. The residual heat which is normally released to the environment in this type of power cycle is captured as much for hot water heating or space heating. Ammonia-water is used for both the power cycle and the cooling cycle.
The experimental investigation of this thesis work analyzed the performance of a scroll based heat engine working with low temperature heat source within the trigeneration facility. Coupling trigeneration and renewable makes a very strong scheme to supply not only low-carbon electricity and low-carbon heat, but also cooling, in an integrated system with high utilization factor. The first part of the work is to study the performance of the heat engine that consists of custom built expander, boiler and condenser in an ammonia water Rankine cycle system. The second part is to determine the utilization of the heat engine driven by low grade heat source in a small scale trigeneration unit. Ammonia water is suitable for low temperature Rankine power cycle, because of its non-azeotropic properties. The source of heat can be at relatively low and intermediate temperatures in the range of 80°C- 200°C. This heat can be derived from a multitude of sources including solar panel collectors, biomass combustion, biofuel, recovered waste heat etc. Due to the trigeneration feature, the utilization factor of the heat source or fuel energy with this system exceeds 90%. The experimental result shows a maximum isentropic efficiency of 67% and an overall energy efficiency of maximum 7% at 120°C source temperature, while the exergy efficiency is about 30%. The experimental result also shows that the concentration of ammonia is a dominant factor in determining the optimum efficiency with a range of ammonia-water mixture. 40% ammonia concentration found optimum, however higher concentration drastically reduces the work output. In the trigeneration facility, the cooling and heating can be adjusted without affecting power generation. Finally, it can be concluded that from the optimization results, if mass production is put in place, the system shows a high economic competitiveness with respect to conventional power generation methods which require multiple individual systems to provide the same results. This system is very new and novel with unique features, which would resolve various energetic and environmental issues and provide potential solutions to residential applications. It is also aimed to make such systems suitable for restaurants, hospitals, commercial buildings, social centres, farming facilities and to use in remote locations. The ultimate goal is to produce a viable commercial product. | en |
