###### Abstract  
This study conducts a comparative performance analysis of three different low-temperature solar collector systems: flat plate solar collectors (FPCs), heat pipe evacuated tube solar collectors (HPETCs), and heat pipe flat plate solar collectors (HPFPCs). Key performance parameters, such as heat transfer coefficients, useful heat, and thermal efficiency, are analyzed under varying mass flow rate, fluid temperature, and antifreeze concentration. The objective is to evaluate the thermal performance of these systems using different heat transfer fluids, specifically water, and mixtures of 30% and 50% ethylene glycol and propylene glycol. The performance data indicate that the heat transfer coefficient in the HPFPC diminishes by 28% and 41% when antifreeze is employed at concentrations of 30% and 50%, respectively. Furthermore, the integration of heat pipes with water in a flat plate solar collector results in efficiency enhancements, with respect to FPCs, of up to 13% at a fluid temperature of 30 \({}^{\circ}\)C, and up to 21% at 80 \({}^{\circ}\)C. At the elevated fluid temperature of 80 \({}^{\circ}\)C, an efficiency increase of 13% is observed with a 30% ethylene glycol concentration. The incorporation of heat pipes leads to an efficiency improvement of up to 6.5% in comparison to traditional flat plate solar collectors. This study highlights the significant impact of fluid properties, affecting the convective heat transfer coefficient, on the overall efficiency of solar collectors, emphasizing the importance of optimizing fluid composition and operating conditions for enhanced thermal performance. s 1 (2020) 2 driven by human activities [1]. In an effort to change this situation, the aim is to use energy sources that are not harmful to the environment. Many studies report the use of various types of renewable energy to meet different needs, whether in the residential, commercial, industrial, or transportation sectors [2,3]. Today, solar energy is extensively utilized across various sectors, both for generating power and for general heating and cooling systems, as reported in different reviews [4, 5, 6]. [PERSON] et al. [4] show that solar energy projects have proliferated across the UAE, demonstrating a diverse range of applications from residential systems to large-scale power plants, resulting in reduced fossil fuel use and greenhouse gas emissions. The study by [PERSON] et al. [5] examines the integration of agrivoltaic systems, which combine agricultural production and solar energy, highlighting their technical and economic viability, the importance of social acceptance, and the opportunities they present for developing policies that promote sustainable land use. In [6], solar energy technologies, emphasizing their potential in meeting future energy demands are examined by [PERSON] et al. They state that large-scale solar power systems significantly contribute to energy generation while mitigating carbon emissions, and that challenges such as land requirements, intermittency, and fluctuating policy support delay growth. Generally, low-temperature solar collectors are used for various applications [7, 8, 9] including the following:  
* Water heating: used in homes and buildings to heat water for domestic and commercial use, especially in areas with sufficient solar radiation. * Space heating: they can be integrated into heating systems in buildings, providing supplemental heat. * Product drying: employed in agricultural product drying processes and in industrial applications where low-temperature heat is required. * Desalination: used in desalination systems where heat is needed for the process. * Air conditioning: they are used in passive cooling systems where heat is combined with other cooling methods  
In regions where temperatures can drop below freezing, water used in solar thermal systems can freeze, potentially causing significant damage to pipes, collectors, and other components.