Solar panels with bio-glycol, symbolizing renewable energy and sustainability.

Beyond Ethylene Glycol: Is Bio-Glycol the Future of Solar Collectors?

Soraya Malik in Climate & Environment October 2026 • 5 min read.

"Explore how renewable bio-glycol enhances solar collector efficiency and sustainability, offering a safer, eco-friendly alternative to traditional coolants."

Ethylene glycol and propylene glycol have long been the standard thermal liquids in solar flat-plate collectors (FPCs), serving both as base liquids and stabilizers for nanofluids. However, the quest for more sustainable and efficient solutions has led researchers to explore renewable alternatives. This article introduces bio-glycol, a renewable-derived option, and examines its potential as a superior base liquid in FPCs.

A recent study investigated the performance of conventional and nanofluid-laden FPCs using different glycol products. The goal was to determine the suitability of bio-glycol by evaluating the impact of various base ratios (BR) on FPC efficiency. The modeling was conducted using MATLAB, simulating the performance of FPCs with copper and cerium oxide nanomaterials.

The results indicated that a 20:80 bio-glycol/water mixture significantly enhances the energetic efficiency of FPCs, achieving up to 72.1%. This surpasses the efficiency of FPCs using ethylene glycol and propylene glycol. Furthermore, the study highlighted that while the energy efficiency of glycol-based nanofluid-filled FPCs generally decreases with higher base ratios of all three glycol products, bio-glycol stands out due to its non-toxic and environmentally friendly nature, making it a safe and sustainable choice for nanofluid-filled FPCs.

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Stats & Impact

Bio-Glycol Efficiency in Flat-Plate Collectors

A study on a nanofluid-laden solar flat-plate collector reported that a 20:80 bio-glycol/water mixture could raise the collector’s energetic efficiency to 72.1%. The reported value was higher than the efficiency achieved with either ethylene glycol or propylene glycol in the study’s comparison.

History

How Solar Thermal Collectors Work

Solar thermal collectors transfer captured solar energy to a working fluid, which can deliver heat directly to a load or store it in thermal reservoirs. Flat-plate collectors capture direct, diffuse, and reflected solar energy over a large surface area, unlike concentrating collectors. They are suitable for low-temperature applications and are commonly used in residential and commercial settings to heat water and air. Collector performance depends on factors including thermal efficiency, optical absorption, fluid flow characteristics, and environmental adaptability.

Why Bio-Glycol Could Revolutionize Solar Collector Technology

Solar panels with bio-glycol, symbolizing renewable energy and sustainability.

Nanomaterials, when mixed with appropriate base liquids like water, ethylene glycol (EG), or propylene glycol (PG), can significantly enhance solar energy extraction in solar water heaters. Researchers have been exploring nanofluids to improve FPC performance. For example, one numerical study showed that an alumina-water nanofluid could increase a collector's outlet temperature by 7.20% compared to using just water. Similarly, introducing a water/cerium oxide nanofluid increased the zero-loss efficiency of an FPC by 10.74%.

While EG and PG are commonly used, they have drawbacks. EG is toxic and poses environmental risks, while PG can increase the risk of plumbing issues in collector systems. This has spurred the search for safer, more sustainable alternatives, leading to the investigation of bio-glycol (BG).

Enhanced Efficiency: Bio-glycol mixtures can boost FPC's energetic efficiency up to 72.1%, outperforming traditional glycols.
Environmental Safety: As a non-toxic, plant-based product, bio-glycol offers a safer alternative, reducing environmental concerns.
Sustainability: Bio-glycol supports sustainability goals by replacing fossil-fuel-based glycols with a renewable resource.

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Latest Research

Bio-Glycol as a Renewable Collector Fluid

A review of nanofluid-laden flat-plate solar collectors reports that bio-glycol (BG), described as a renewable, corn-based glycol product, has recently been suggested for use in flat-plate collectors. The source presents this as a proposed application rather than a settled finding about its performance or adoption.

The study used mathematical modeling in MATLAB to simulate FPC behavior. The model accounted for solar insolation passing through the glazing cover to the absorber plate, with thermal energy then transferred to the working fluid inside the riser tubes. The collector's specifications were adapted from Thermo Dynamics Ltd. G-series product data. The investigation focused on first-law and second-law efficiencies, testing various working fluids, including pure water, BG, PG, and EG, and their mixtures with nanoparticles, assuming steady-state and laminar flow conditions. Instantaneous performance was evaluated for each fluid.

The Future is Green: Embracing Bio-Glycol in Solar Technology

The research indicates that glycol products with higher base ratios decrease energetic efficiency when used as antifreeze. In contrast, BG and EG increase exergy efficiency, while PG decreases it. When used as a base liquid, the energy efficiency of the FPC decreases with higher glycol product base ratios. However, BG and EG enhance exergy efficiency, while PG has little impact.

The highest energetic efficiency was achieved with a BG20-based CeO2 nanofluid (72.1%), suggesting it as the optimal nanofluid for maximizing energetic efficiency. Furthermore, the highest exergetic efficiency was obtained with an EG60-based CeO2 nanofluid (1.66%), making it ideal for minimizing energy destruction.

Overall, bio-glycol emerges as a promising substitute for traditional antifreezes like PG and EG, offering higher energetic efficiency and being non-toxic and environmentally friendly. Its potential to promote sustainable development makes it a compelling choice for the future of solar thermal technology.

How bio-glycol compares in collector studies

The 2018 paper compares bio-glycol with ethylene glycol and propylene glycol as liquids for flat-plate collectors; its result concerns the collector’s energetic efficiency.^[1]

A separate collector experiment found that adding alumina nanofluid did not always improve efficiency: deposition increased resistance to heat transfer, and efficiency fell in that test.^[2]

Modeling bio-glycol mixtures in flat-plate collectors

Setting	Solar flat-plate collectors^[1]
Comparison	Bio glycol compared with ethylene glycol and propylene glycol^[1]
Main outcome	FPC energetic efficiency^[1]
Effect size	20:80 bio glycol/water mixture enhanced energetic efficiency up to 72.1%^[1]
Times cited	1^[1]

What the modeled comparison establishes-and leaves open

The paper frames bio-glycol as a renewable-derived base-liquid candidate, while the later review likewise presents its collector use as a suggestion. Together, these support interest in the option, not proof of broad adoption.^{[1] [3]}

Questions beyond the reported comparison

How would collector performance vary with flow conditions and nanoparticle loading, given that another experiment reported results across differing flow rates and deposition-related losses?^{[2] [4]}
How widely is renewable-derived bio-glycol actually used in collectors, beyond being proposed in a later review?^{[1] [3]}

Sources

About this Article -

Written with AI assistance from published research, and reviewed by the Mystum team. See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1051/matecconf/201822504014, Alternate LINK

Title: Suitability Of Base Liquid In A Nanofluid-Laden Solar Flat-Plate Collector With Emphasize On Bioglycol

Subject: General Medicine

Journal: MATEC Web of Conferences

Publisher: EDP Sciences

Authors: Seyed Reza Shamshirgaran, Hussain H. Al-Kayiem, Morteza K. Assadi, K.V. Sharma

Published: 2018-01-01

Everything You Need To Know

What is bio-glycol, and why is it important?

Bio-glycol is a renewable, plant-derived alternative to traditional coolants like ethylene glycol and propylene glycol used in solar flat-plate collectors (FPCs). It is a sustainable option that enhances solar collector efficiency and is non-toxic. The importance lies in its ability to improve the energy efficiency of FPCs, potentially achieving up to 72.1% in certain mixtures. This is significant because it offers a safer and more environmentally friendly approach to solar energy collection compared to the established use of ethylene glycol, which is toxic. Using bio-glycol helps reduce environmental impact while boosting performance.

What are solar flat-plate collectors (FPCs), and why are they relevant to this discussion?

Solar flat-plate collectors (FPCs) are devices that absorb solar energy and convert it into heat. Traditionally, they use thermal liquids, such as ethylene glycol (EG) or propylene glycol (PG), to transfer heat. In the context of this discussion, FPCs are the focus, with the study specifically examining how bio-glycol (BG) can be used as a more efficient and sustainable coolant within these collectors. The implications of using bio-glycol within FPCs are substantial, including enhanced energy efficiency, reduced environmental impact due to the non-toxic nature of bio-glycol, and the promotion of sustainability by using a renewable resource.

What are ethylene glycol and propylene glycol, and what role do they play?

Ethylene glycol (EG) and propylene glycol (PG) are standard thermal liquids used in solar flat-plate collectors (FPCs) due to their ability to transfer heat efficiently. However, they have limitations. Ethylene glycol is toxic and poses environmental risks, while propylene glycol can contribute to plumbing issues within collector systems. The significance lies in their historical and current usage, despite the drawbacks. The implications of using EG and PG highlight the need for safer and more sustainable alternatives, such as bio-glycol, that do not carry the same risks. Their presence underscores the advancements that bio-glycol represents.

What are nanofluids, and how do they relate to this topic?

Nanofluids are engineered fluids that contain nanoparticles dispersed within a base fluid like water, ethylene glycol, or bio-glycol. In this context, they are used in solar flat-plate collectors (FPCs) to improve energy absorption and transfer. Nanofluids' importance is that they can significantly enhance the efficiency of FPCs. The use of nanofluids in conjunction with bio-glycol offers the potential for increased energy efficiency compared to using traditional coolants alone. The implications include the potential for higher temperatures and greater energy extraction from the collectors, resulting in better performance. Specifically, research showed that mixing water and cerium oxide nanofluid could increase the zero-loss efficiency of an FPC by 10.74%.

What is MATLAB, and what role does it play in this context?

MATLAB is a software used to create mathematical models and simulations. In the context of this discussion, it was used to simulate the performance of solar flat-plate collectors (FPCs) under various conditions. The significance of MATLAB lies in its ability to provide insights into the behavior of FPCs with different working fluids, such as bio-glycol, propylene glycol, and ethylene glycol. The implications of using MATLAB in this study are crucial. The software enables researchers to evaluate and compare the efficiency of different glycol products and mixtures, which is crucial for assessing and understanding how bio-glycol and other fluids work in solar collectors. The simulations allowed researchers to understand how factors like the base ratio of the glycol products affected performance.