| Author | Boonrit Prasartkaew |
| Call Number | AIT Diss. no.ET-11-05 |
| Subject(s) | Solar air conditioning
|
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Engineering in Energy Technology, School of Environment, Resources and Development |
| Publisher | Asian Institute of Technology |
| Series Statement | Dissertation ; no. ET-11-05 |
| Abstract | Nowadays, we are confronted with challenges of energy crisis and global warming. Global warming is caused by the burning of fossil fuels for electricity generation, industrial processes and transport. Of the total electricity generation, the energy used in buildings consumes about 30% of the total, of which about 70% is used for air conditioning purposes. During hot weather and especially in tropical regions, the demand for electricity greatly increases because of the extensive use of air-conditioning systems. Such ever-increasing demand could place significant strain on the current energy infrastructure and potentially contribute to green house gas emissions. To address these serious problems, renewable energy is one of the major options. Solar energy along with biomass (mainly from wood and their by products) utilization is a win-win solution to address this issue. Compared with conventional vapour compression cycle, a solar absorption cycle is more reliable, quiet, and feasible. From an energy saving point of view, a solar cooling system can save in the range of 25–40% of electrical energy when compared to an equivalent cooling capacity of a conventional system. The combination of renewable energy-based systems and heat-driven absorption chiller (ABC) can help address reducing green house gas emissions. Solar cooling system without an auxiliary heater (AUH) can be operated only during sunshine period with very low reliability. Almost all earlier researches on solar absorption cooling (SAC) systems used fossil energy AUHs. To address this challenge of developing a completely renewable energy based system, this dissertation presents a novel solar-biomass hybrid air conditioning (SBAC) system. This study presents the simulation and experimental studies aimed at assessing the feasibility of solar-biomass hybrid energy for absorption cooling technology under tropical (Thailand) conditions. There are three specific objectives: to design and provide the optimum parameters and configuration of the SBAC system, to evaluate the performance of the SBAC system theoretically by developing a simulation model using actual weather data (and the model will be validated against the experimental result), and to investigate the performance of the SBAC system operating in the actual tropical climate conditions. The methodology consists of mathematical model development, experimental setup and experimentation, and the model validation to evaluate the applicability of the developed model. Before all components were linked to form the complete system, theoretical and experimental studies of individual components were carried out. The simulation was done to design the system and evaluate the system performances. Five minute time period based simulations were performed using weather data obtained from the meteorological station at the Asian Institute of Technology, Bangkok, Thailand. The optimum system configuration (based on performance) was selected using simulation results. The model was used to study the influences of the important operating parameters on the chiller coefficient of performance (COP) and overall system coefficient of performance (COPsys). In these design steps, the optimum values of operating parameters and components sizes as well as their output of temperatures, power and efficiency were estimated. The simulation results show that the cooling load and solar fraction (SOF) are greater than 4.5 kW and 0.7, respectively, for a hot water set point temperature (SPT) of 84 ◦C. ivThe components sizes and operating parameters obtained from the design were used to design the experimental setup. The construction and installation of the SBAC system with the data acquisition (DAQ) system were carried out. The experimental studies consisted of three modes of operation: a) solar cooling system with electrical auxiliary boiler, b) solar-biomass hybrid cooling system and c) solely solar based cooling system. Modes a) and c) of experimental study were done at estimating performance of the system as base cases operated as the conventional SAC systems. The experiments were carried out for many days to observe the influences of the actual tropical climate on the performance of the SBAC system. Steady state periods of all experimental data were selected and used for the performance analysis. The steady state condition for each experimental result was defined with the criteria that all variation between time steps of each measured parameters must be less than 10% for all measured parameters over a period of 30 minutes or longer. The experimental results show that the developed SBAC system is promising. The experimental data demonstrates that the chiller was operated at about 75% of nominal capacity with the average COP of about 0.6. The comparative study results show that the proposed system can be operated with higher reliability than the conventional SAC system which operated without the AUH. Finally, the results show that the average COP and COPsys of the proposed system is higher than the conventional one which was operated with electrical AUH, as the generator supplied heat at the starting period and the energy losses of the proposed system are lower but their absorbed heat at evaporator are almost the same. Moreover, comparative study with similar studies in the literature shows that the proposed system’s performance (COP and COPsys) is superior to the experimental results reported in literature. The experimental results were also compared with those from the simulation model. The steady state periods of all experimental data were used for this model validation. Two statistical indicators, i.e., root mean square error (RMSE) and mean bias difference (MBD) (together with the uncertainties) were used to present and compare the results from the experiments and the models. The simulation model was validated against the experimental data, and the results showed that the simulation gives good comparison with experimental observations. The proposed system can be a sustainable energy air conditioning system for the future, and can be used with municipal solid waste (MSW) and waste heat recovery. Moreover, it can also be developed to be an isolated tri-generation system. This would thus help in our efforts to address global warming and greenhouse gas emissions. |
| Year | 2011 |
| Corresponding Series Added Entry | Asian Institute of Technology. Dissertation ; no. ET-11-05 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Energy and Climate Change (Former title: Department of Energy, Environment, and Climate Change (DEECC)) |
| Academic Program/FoS | Energy Technology (ET) |
| Chairperson(s) | Kumar, S.; |
| Examination Committee(s) | Perera, L. A. S. Ranjith ;Salam, P. Abdul; |
| Scholarship Donor(s) | Rajamangala University of Technology Thunyaburi, Thailand; |
| Degree | Thesis (Ph.D.) - Asian Institute of Technology, 2011 |