This paper presents a new methodology for the energy integration of systems that require refrigeration. It considers the integration between process streams as well as that between the heat from process stream excess, solar energy, fossil fuels, and biofuels to run the stripper required by the absorption refrigeration (AR) needed. The proposed methodology consists of two stages: the first one identifies the energy targets, while the second one uses a new mathematical programming model to solve a multiobjective optimization mixed-integer linear programming (MILP) problem, allowing one to determine the minimum cost as well as the minimum greenhouse gas emissions (GHGE) to satisfy the utility requirements identified in the first stage. The proposed model considers the optimal selection of different types of solar collectors, and since the solar radiation depends on the season of the year, the model also accounts for the best combination of fossil and biofuels to complement the energy required for the AR. The proposed methodology is very useful to identify the scenario required to implement the use of clean energies in the refrigeration process. Three problems are presented to show the applicability of the proposed methodology, which does not exhibit numerical complications; these results show that process integration helps to get a given reduction in the GHGE economically attractive involving the use of clean energies, besides identifying the required tax credit to get economic and environmentally efficient cooling systems. In addition, because of the availability of the solar radiation, the solar collectors must be integrated with different types of energy, depending on the season of the year.
Absorption refrigeration is gaining increasing attention in industrial facilities to use process heat for partially or completely driving a cooling cycle. This paper introduces a systematic approach to the design of absorption refrigeration systems for industrial processes. Three sources of energy are considered to drive absorption refrigerators: excess process heat, solar energy, and fossil fuels. To handle the dynamic nature of solar energy, hot water tanks are used for energy storage and dispatch. Thermal pinch analysis is performed to determine the amount of available excess heat and the required refrigeration duty. Next, a multiperiod optimization formulation is developed for the entire system. The procedure determines the optimal mix of energy forms (solar versus fossil) and the dynamic operation of the system. Three case studies are solved to demonstrate the effectiveness and applicability of the devised procedure.
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