Innovative Hybrid Solar-Thermoelectric System Utilizing Molten Salt for Sustainable Energy Storage

A Hybrid Solar–Thermoelectric System Incorporating Molten Salt for Sustainable Energy Storage Solutions

Abstract: Sustainable energy, particularly renewable sources, is increasingly recognized as essential for energy conservation and combating global climate change. Among the renewable energy sources in the UAE, solar energy stands out due to the country’s abundant solar radiation. This paper introduces an innovative system that combines parabolic trough mirrors, molten salt storage, and thermoelectric generators (TEGs) to create a reliable solar energy solution tailored for the UAE’s unique needs. The proposed system can be scaled for various applications, from residential homes to commercial establishments. The design aims to generate 2.067 kWh/day, achieving thermal and optical efficiencies of 90% and 90.2%, respectively. The TEG efficiency can potentially reach 149% when using a liquid-saturated porous medium, ensuring continuous operation throughout the day. This makes the system suitable for off-grid areas, providing a cost-effective, carbon-free energy source that can integrate with the electric grid, similar to fossil fuel plants, with lower maintenance requirements, thus supporting the UAE’s renewable energy strategy.

1. Introduction
Renewable energy, particularly green sustainable energy, plays a critical role in addressing energy conservation and mitigating climate change. Technologies harnessing renewable sources, such as wind and solar energy, are vital for reducing greenhouse gas emissions and enhancing energy accessibility while promoting economic growth. Despite numerous studies on sustainable energy, innovative solutions are still necessary to overcome existing challenges.

Historically, the UAE has relied heavily on oil exports, but the government recognizes the importance of diversifying its energy portfolio. Significant investments in renewable energy, especially solar energy, are part of the UAE’s Vision for a sustainable future. The UAE Energy Strategy 2050 aims for a 50% contribution from clean energy to the overall energy mix by 2050, reflecting the country’s commitment to becoming a global leader in renewable energy.

Given the UAE’s high solar radiation levels, solar energy not only aids in reducing greenhouse gas emissions but also supports energy conservation and economic development. However, the intermittent nature of solar energy necessitates efficient storage solutions for a stable power supply. This paper emphasizes the integration of trough solar mirrors with Molten Salt Energy Storage (MSES) and TEGs, optimizing the charging and discharging processes of thermal energy storage systems to maximize power generation from solar systems.

The novel design proposed here incorporates two extendable parabolic mirrors that collect solar energy and store it in a salt tank positioned between the mirrors. The molten salt functions as both a heat transfer fluid and a storage medium, eliminating the need for traditional receivers and fluid systems. TEGs convert heat directly into electricity using the Seebeck effect.

2. Literature Review
Green sustainable energy is crucial in mitigating climate change and conserving energy resources. Renewable energy sources like solar, wind, hydro, and biomass are essential in reducing greenhouse gas emissions. Research has highlighted the economic viability of renewable technologies, emphasizing their potential to create jobs and stimulate economic growth. Policies fostering investment in renewable energy have been implemented in various countries to ensure energy security and reduce fossil fuel dependency.

The UAE has made significant strides in solar energy utilization, establishing ambitious targets through initiatives like the Dubai Clean Energy Strategy 2050, which aims to source 75% of Dubai’s power from clean energy by 2050. The country has launched major solar projects, such as the Mohammed bin Rashid Al Maktoum Solar Park, contributing to its renewable energy goals while attracting investment and creating job opportunities.

3. Design Methodology
The main objective of the proposed hybrid system is to provide an efficient and effective solar energy solution capable of generating and storing electricity. The system can be customized for various applications, from residential to commercial use, and is particularly suitable for off-grid areas. The use of molten salts as an energy storage solution ensures continuous electricity generation, even without direct solar radiation, through the integration of TEGs.

The design involves several components:
– Aluminum Frame: Chosen for its strength-to-weight ratio and corrosion resistance, enhancing durability and efficiency.
– Parabolic Trough System: Consists of two mirrors that concentrate solar radiation onto the salt tank, maximizing energy collection.
– Copper Tank: Designed for thermal storage, featuring excellent heat conductivity and insulation properties.
– Molten Salts: Selected for their thermal stability, conductivity, and environmental safety, ensuring efficient heat transfer and storage.
– Thermoelectric Generators (TEGs): Employed to convert thermal energy into electricity, integrated with heat sinks and fans for optimized performance.
– Tracking System: A single-axis tracker is proposed to follow the sun, enhancing energy capture throughout the day.

4. Data Analysis and Results
The proposed hybrid system aims to achieve a daily energy output of 2.067 kWh, equivalent to the production of a 400 W photovoltaic panel under UAE conditions. Calculations based on solar irradiance and system efficiencies indicate the necessary mirror area and thermal energy requirements. The system is designed to collect sufficient solar energy to meet daily power needs, ensuring reliability in energy generation.

5. Economic Assessment and Comparative Analysis
The economic evaluation of the proposed hybrid system includes initial investment costs, lifetime costs, and the levelized cost of electricity (LCOE). The initial costs for components like parabolic trough mirrors, copper tanks, and TEGs are estimated based on current market prices in the UAE. Lifetime costs consider maintenance and replacement needs, demonstrating the system’s long-term viability.

Comparative analysis with alternative systems, such as PV with battery storage and standard parabolic trough systems, indicates that the proposed hybrid system offers competitive pricing and reliability, with unique advantages like continuous power availability and lower maintenance needs.

6. Design Evaluation and Alignment with the UAE’s Policy
The proposed solar energy system aligns with the UAE’s renewable energy objectives, supporting economic viability, scalability, and off-grid capability. The system contributes to environmental sustainability and innovation through its design, ensuring a consistent energy supply and promoting the UAE’s commitment to clean energy solutions.

7. Conclusions
This study presents a pre-feasibility analysis of a hybrid solar–thermoelectric system integrating parabolic trough mirrors, molten salts, and TEGs. The system demonstrates potential for reliable energy generation while remaining economically competitive with existing technologies. Future work should validate performance assumptions through prototype testing and characterization.

Author Contributions
The contributions include conceptualization, methodology, validation, data curation, and writing of the manuscript.

Funding
This research was supported by the Research Unit at Liwa College under Internal Research Grant IRG-ENG-002-2023.

Conflicts of Interest
The authors declare no competing interests.

The full article is accessible under the open access license, and readers are encouraged to explore the detailed findings and methodologies presented.