Study of an intermittent regenerative cycle for solar cooling
The study presented here is focused on the use of aqua-ammonia solution in a novel solar-powered refrigeration cycle intended to be suitable for use in the rural areas of developing countries. The cycle is referred to as a `intermittent regenerative' (IR) cycle, the term regenerative meaning in this context the use of heat recovery or recuperation. The first chapter describes the three better known cycles which may be considered for this application. The IR cycle is introduced as a hybrid development of these which offers the significant advantages of high efficiency while minimising complexity. Chapter 1 provides a methodology by which the novel aqua-ammonia system can be evaluated in comparison with existing systems. The second chapter surveys previous experimental work on solar driven aqua-ammonia cycles. Chapter 3 consists of a detailed design study of the new IR cycle based on computer modelling techniques. The study serves as an analysis of the cycle and allows the performance of the cycle, together with design features and component sizes, to be simulated in a variety of meteorological conditions. A number of original design proposals are evaluated through the modelling exercise. Chapter 4 summarises the results of a second separate modelling exercise which investigates the absorption phase of the cycle. Chapters 5 and 6 describe experimental work. The results of laboratory tests are compared with the predictions of the computer model and in the event serve to validate the theoretical characterisation made in chapter 3 of the performance of key components of the system. The energy efficiency of the system as measured by experiment is proved to correspond to theoretical prediction, so representing a significant advance on the performance of alternative systems. Chapter 7 addresses itself to the wider question of the social and economic validity of a device with the performance and cost of the IR device. A case study is undertaken which explores the potential role of the device in the fish trading economy of Zambia. The study provides data valuable in assessing the usefulness of the technology in helping to stimulate the under-capitalised rural economy of a developing country and in improving local food resource utilisation. Chapter 8 draws together the conclusions of the various chapters and provides an overall conclusion and comment on the value of the IR system. It is proved to have a high efficiency but not to have the robustness nor portability demanded for widespread application in remote locations. Nevertheless the likely life-time cost-effectiveness of the system is judged to be an improvement on existing alternatives and suggestions are made for further improvement.