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Modelling and Optimization of Long-Term Heat Storage Systems in Greenhouses

Mohebi, Parastoo | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 53733 (46)
  4. University: Sharif University of Technology
  5. Department: Energy Engineering
  6. Advisor(s): Roshandel, Ramin
  7. Abstract:
  8. Heating demand required for greenhouses is mainly met by fossil fuels. On the other hand, anxieties over usage of fossil fuels have led the societies to move toward renewable energies. With this in mind, the purpose of this research is to analyze using both solar energy for satisfying the heating demand of greenhouses and heat storage for compensating the intermittence of renewable energy.Considering the mentioned points, in the current research, a linear optimization framework has been developed for design and operation of energy systems including long-term heat storage to meet heating demand of greenhouses. The objective of this framework is to minimize annual cost. The developed method has been used for heating demand of a 1-hectare greenhouse located in Tehran by utilizing a solar collector and a back-up boiler. The results of this optimization framework include the optimal capacity of each technology and hourly optimal energy flows during a year. Furthermore, by applying multi-objective optimization (epsilon constraint method), the opposing economic and environmental impacts are presented by a Pareto curve. Different scenarios are assessed for application of the developed optimization framework, including usage of fossil fuel, solar energy (without back-up boiler) and hybrid scenario (using both solar energy and fossil fuel). Furthermore, impact of cultivation patterns, subsides of renewable energy, carbon tax, different policies for gas price and solar collector price have been analyzed.In an optimal point selected by Linmap decision-making method, among the optimal points of pareto resulted from multi-objective optimization, CO2 emissions decline by 75.22% in comparison with fossil fuel scenario. Analysis of the impact of crop type on the results of the assessed project depicts that the annual cost of cultivating lettuce and cucumber will be 39.89% and 15.78% less than that of cultivating tomato, respectively. Besides, by considering the cultivation pattern and not cultivating during November, December and some days of October, the annual cost will be decreased by 31%. The analysis of gas price shows that by rising till average world price, considering economical optimization, the solar fraction will be increased by 21.66%.
  9. Keywords:
  10. Solar Collectors ; Linear Optimization ; Design Optimization ; Energy Demand ; Design and Operation Optimization ; Greenhouse Heating Demand ; Heat Storage

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