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Study: Investigation and proposal of a novel solar-powered trigeneration system for more environmentally friendly heating, cooling, and power generation. Image Credit: Ayham Thalji/Shutterstock.com

Solar-Trigeneration System Overview

Solar energy remains one of the most promising renewable sources due to its abundance and potential to satisfy diverse energy demands, particularly in building applications. Concentrating solar power (CSP) technologies, such as solar towers equipped with heliostat fields, are widely used for efficient solar-to-thermal energy conversion.

However, conventional central receiver designs with straight tubes suffer from limited heat transfer capabilities, reducing system efficiency. Moreover, traditional organic Rankine cycles (ORC), commonly used for low-temperature power generation, encounter thermodynamic irreversibility due to mismatches between working fluid temperature profiles and heat sources.

The Kalina cycle, utilizing a low-boiling ammonia-water mixture, addresses this by offering a better temperature match, thereby elevating power cycle efficiency. Meanwhile, absorption refrigeration cycles (ARC), especially those based on lithium bromide-water or ammonia-water pairs, enable the use of waste or low-grade heat for cooling production. Combining these cycles enables the utilization of solar heat for producing electricity, cooling, and heat simultaneously, thus maximizing resource use and reducing environmental impact.

System Modeling and Simulation Approach

The proposed system integrates a solar power tower with a central receiver designed with helically coiled tubes embedded with internal ribs, through which Syltherm 800 oil flows as the heat transfer fluid (HTF). The oil absorbs concentrated solar radiation reflected by heliostats, raising its temperature effectively due to the combined enhancement of coil curvature and rib-induced turbulence.

This heated oil then transfers thermal energy to a Kalina cycle working fluid in a superheater section, generating electricity through a turbine. The waste heat remaining in the cycle is harnessed by an ammonia-water-based absorption refrigeration cycle to provide cooling, while excess heat is supplied for space or process heating through a heat exchanger.

The modeling and analysis of the system were carried out using the Engineering Equation Solver (EES) software, incorporating mass, energy, and exergy balance equations with working fluid thermodynamic properties obtained from the REFPROP database. Computational Fluid Dynamics (CFD) simulations were conducted via ANSYS FLUENT to optimize the receiver’s heat transfer characteristics by variation of parameters such as rib height, coil pitch, and solar irradiance (Direct Normal Irradiance, DNI).

The parametric study focused on how these geometric and environmental factors influence the HTF outlet temperature and pressure drops. Additionally, thermodynamic performance was quantified through energy and exergy efficiency calculations to identify major sources of irreversibility across system components.

Performance Analysis and Parameter Effects

CFD simulations revealed that using helically coiled tubes with internal ribs significantly improves heat transfer performance in the solar receiver. The highest increase in oil outlet temperature was approximately 39.4% observed at a rib height of 2 mm, coil pitch of 42 mm, and solar radiation of 1000 W/m2. This enhanced thermal conversion efficiency would potentially allow the Kalina cycle to operate more effectively with higher inlet heat source temperatures.

Thermodynamic analysis showed that integrating the absorption refrigeration cycle with the Kalina cycle yielded considerable gains in system efficiencies. Specifically, energy efficiency improved by about 23.78 %, and exergy efficiency rose by 14.55 % compared to the Kalina cycle operating alone. These improvements result from the productive utilization of waste heat for cooling, which typically would be discarded in conventional power generation schemes. The system’s overall energetic output ranged from 144.8 kW to 202.5 kW as the solar irradiance increased from 450 to 1000 W/m2, demonstrating the scalable potential of the design.

The exergy analysis identified the central receiver, heliostat field, superheater, and vapor separator as the principal locations of exergy destruction, with the receiver alone accounting for over 22 % of the irreversibility. These findings highlight opportunities for further optimization by improving solar absorption and reducing thermal losses. Furthermore, sensitivity studies on system operating parameters such as separator pressure and evaporator temperature showed varying effects on power output and cooling capacity, suggesting that a careful control strategy could also enhance system performance.

System Efficiency and Sustainability Insights

This research presents a comprehensive investigation of a new solar-powered trigeneration system that exploits heliostat-concentrated solar energy with helically coiled tube receivers to generate electricity, heating, and cooling in an integrated manner. The system’s modular design enables flexibility for application in different scales and building types, providing an environmentally sustainable solution to meet combined energy demands.

Although the analysis is theoretical and requires experimental validation, findings suggest the system offers meaningful reductions in energy waste and harmful emissions by shifting to renewable solar heat inputs. Future work may extend to exergo-economic assessments and optimizing components to minimize exergy destruction. Overall, the study underscores the potential of integrated renewable energy systems in addressing building energy requirements while supporting global sustainability goals.

Journal Reference

Alsharif A.M., Khaliq A., et al. (2026). Investigation and proposal of a novel solar-powered trigeneration system for more environmentally friendly heating, cooling, and power generation. Scientific Reports 16, 12871. DOI: 10.1038/s41598-026-41098-x, https://www.nature.com/articles/s41598-026-41098-x

Written by Dr. Noopur Jain

Reviewed by Laura Thomson

Dr. Noopur Jain is an accomplished Scientific Writer based in the city of New Delhi, India. With a Ph.D. in Materials Science, she brings a depth of knowledge and experience in electron microscopy, catalysis, and soft materials. Her scientific publishing record is a testament to her dedication and expertise in the field. Additionally, she has hands-on experience in the field of chemical formulations, microscopy technique development and statistical analysis.