Joan Carles Bruno

Review of optimization models for the design of polygeneration systems in district heating and cooling networks

Abstract The current increasing energy prices and the limitation of the existing energy resources promotes the use of new energy production systems, like hybrid integrated systems (using fossil fuels and renewable energy sources) with high-energy efficiency. These integrated systems, known as polygeneration systems, produce electrical, heating and cooling at different conditions at a higher efficiency than a conventional system, and involve a wide range of technologies with several possible configurations. Sometimes the design of these systems is carried out with the aid of mathematical models that are solved and optimized minimizing the investment and operational costs, but these optimization techniques are applied frequently for industrial applications and rarely for building or district heating and cooling (DHC) applications. The objective of this paper is to present a literature review of the optimization techniques that have been used so far for building or DHC applications. The main purpose of this review is to establish the basis for the development of an optimization tool for the synthesis and design of polygeneration systems for their use in district heating and cooling networks, that are optimized reducing their investment and operational cost. An example is presented to illustrate the application of this tool.

Combined absorption power and refrigeration cycles using low- and mid-grade heat sources

This article presents several combined absorption cycles proposed for the simultaneous and/or alternative production of power (mechanical or electrical) and refrigeration. The cycles are classified into two groups according to their driving heat source temperature range as low-grade (<200°C (392°F)) and mid-grade (<300°C (572°F)) combined absorption cycles. The thermodynamic performance of these cycle configurations were evaluated based on energetic and exergetic performance criteria that consider the thermodynamic quality of their useful outputs in both performance criteria. One particularly interesting application of such types of cycles could be the efficient utilization of solar thermal collector installations throughout the year to produce variable amounts of electricity and cooling according to a given building demand to minimize the consumption of primary energy.

Performance Analysis of Absorption Chillers Using Data Reconciliation

Performance data obtained from measurements of process variables usually do not obey material and energy conservation laws. This is why a data reconciliation process, that is, the adjustment of measured data to obey the conservation laws and other constraints is necessary in order to characterize the real performance of equipment, processes, or the whole plant. The information on the partial load and off-design operation performance of absorption chillers is scarce. Real operation of these units do not always coincides with the expected performance according to the data provided by the manufacturer due to site specific conditions. On the other hand the data reconciliation procedure has been extensively applied mainly only for open cycles with a moderate number of recycle streams. The objective of this work is the development and application of the data reconciliation technique to analyse the performance of absorption chillers using rigorous thermodynamic properties for the calculation of the P-V-T equilibrium properties and enthalpies. We present in this paper the preliminary test results for one of the absorption chiller components, the evaporator.Copyright