Modeling and optimal control of an energy-efficient hybrid solar air conditioning system

Abstract

The paper addresses the modeling and optimal control problem of a new hybrid solar-assisted air conditioning system developed for performance enhancement and energy efficiency improvement. To regulate the mass flow rate of the refrigerant vapor passing through a water storage tank for increasing the refrigerant's subcooling process at partial loads, we propose a new discharge bypass line together with an inline solenoid valve, installed after the compressor. In addition, to control the air flow rate, a variable speed drive is coupled with the condenser fan. For the control purpose, a lumped parameter model is first developed to describe the system dynamics in an explicit input-output relationship; then, a linear optimal control scheme is applied for the system's multivariable control. The system has been fully-instrumented to examine its performance under different operation conditions. The system model is then validated by extensive experimental tests. Based on the obtained dynamic model, an optimal controller is designed to minimize a quadratic cost function. Numerical algorithms, implemented in a simulation tool, are then employed to predict the energy performance of the system under transient loads. The experimental results obtained from implementation with PLC demonstrate that the newly-developed system can deliver higher system efficiency owing to amelioration of the refrigeration effect in the direct expansion evaporator and adjustment of its air flow rate. The development is thus promising for improvement of energy efficiency, enhancement of the system performance while fulfilling the cooling demand.

Optimal Power Flow Techniques under Characterization of Conventional and Renewable Energy Sources: A Comprehensive Analysis

“…In 2016, Guo et al [88] presented the optimal ratio of turbine pressure drop to the available total pressure difference and examined it broadly using theoretical analysis and 3D numerical simulations, for solar chimney power plant (SCPP). In 2015, Ha and Vakiloroaya [129] addressed the modelling and control problem of a fully developed hybrid solar-assisted, splitsystem air-conditioner to improve the performance of an existing solar air-conditioning system. In 2013, LizarragaGarcia et al [130] presented an optimization case study for the time-variable operation of the concentrated solar power on demand (CSPonD) solar energy receiver and thermal energy storage.…”

Development and calibration of a model for the dynamic simulation of fans with induction motors

“…More specifically, ESP-r and Fluent tools were used for simulating heat transfer and fluid dynamics, respectively. Again, an ad-hoc numerical algorithm was implemented in TRYNSIS in order to predict the energy performance of a hybrid solar air conditioning system under transient loads (Ha and Vakiloroaya (2015)). In the same TRYNSIS software platform two hybrid micro-generation systems in a load sharing application among residential and office buildings were successfully modeled by Canelli et al (2015).…”

Solar Air-Conditioning Systems

“…At steady-state conditions, the compressor power consumption was decreased from 1.45 to 1.24 kW, which is traduced by a global energy saving of about 14 and 7.1% for only the compressor. Likewise, an energy saving achieved by the condenser fan is about 2.6% [25], which allows increasing the COP. Hence, the authors reported that the system is able to satisfy efficiently the cooling requirements.…”

“…On the other hand, the investigation [25] couples the solar energy to a traditional vapor compression air conditioner to perform a new hybrid solar-driven AC system. The proposed system was modeled and controlled using TRNSYS software in order to improve its energy efficiency.…”