Report on a Hybrid Radiation Filtering and Passive Cooling Strategy for Floating Photovoltaic Systems

Executive Summary

This report details the development and analysis of a novel floating photovoltaic (FPV) system designed to significantly advance Sustainable Development Goal 7 (Affordable and Clean Energy) and SDG 13 (Climate Action). A three-dimensional multi-physics thermal model was created to evaluate an innovative design that incorporates a passive, natural convection cooling loop (NCCL) which dually functions as a solar radiation filter. The primary objective was to optimize the cooling loop geometry to enhance the electrical performance and sustainability of FPV systems. The model investigates the combined effects of passive cooling and radiation filtering by varying key geometric parameters. Simulation results indicate a remarkable improvement in FPV electrical performance. The system effectively filters non-useful wavelengths for crystalline silicon cells while simultaneously reducing operational temperatures. Key outcomes include a reduction in the daily average temperature by up to 15 °C, a subsequent 3% increase in electrical efficiency, and a thermal convective cooling contribution of up to 64.48%. This passive system enhances energy output without parasitic energy consumption, directly supporting SDG 7. The system’s performance was assessed under diverse global solar irradiance levels, confirming its practical feasibility and effectiveness even under minimum irradiance conditions, thereby demonstrating its potential for widespread global deployment in line with SDG 9 (Industry, Innovation, and Infrastructure).

Introduction: Aligning Photovoltaic Technology with Sustainable Development Goals

The Challenge: Enhancing Renewable Energy for SDG 7 and SDG 12

Floating photovoltaic (FPV) systems represent an innovative solution to the land-use challenges associated with large-scale solar farms, contributing to SDG 11 (Sustainable Cities and Communities) and SDG 13 (Climate Action). However, the operational efficiency of photovoltaic (PV) cells is critically hindered by temperature; for every 1°C rise in a crystalline silicon (c-Si) cell, electrical efficiency decreases by approximately 0.5%. This inefficiency not only curtails energy output but also shortens the operational lifespan of the panels, running counter to the principles of SDG 12 (Responsible Consumption and Production). Effective thermal management is therefore vital to sustain and improve the energy yield of PV systems, making them a more reliable and affordable clean energy source as envisioned by SDG 7.

The Solution: Advanced Floating Photovoltaics for Sustainable Infrastructure

This study focuses on enhancing FPV systems through an integrated approach that addresses both thermal management and spectral efficiency. The proposed system utilizes a Natural Convection Cooling Loop (NCCL), a passive technology that requires no external energy supply, aligning perfectly with the goals of sustainable and resilient infrastructure (SDG 9). By positioning the cooling channel in front of the PV panel, the system achieves two critical functions simultaneously:

1. Passive Cooling: It reduces the PV cell’s operating temperature by using the underlying water body as a heat sink, thus increasing electrical output and longevity.
2. Radiation Filtering: The coolant (pure water) absorbs non-useful infrared wavelengths (beyond 1125 nm) that generate heat but not electricity in c-Si cells. This spectral filtering further reduces the thermal load on the panel.

This dual-function design represents a significant innovation aimed at maximizing the contribution of solar technology to global sustainability targets.

A Novel Approach: Integrating Cooling and Radiation Filtering

System Design and Modelling for SDG 9

A reliable three-dimensional simulation tool was developed to model the multi-physics interactions within the hybrid FPV-NCCL system. The model was designed to achieve the following objectives, contributing to innovation and sustainable infrastructure under SDG 9:

• Advance the understanding of coupled thermal-fluid dynamics and radiation filtering in a passive FPV cooling system.
• Optimize the cooling loop geometry, including the height of the cooling channel and the spacing between connecting tubes, to maximize performance.
• Evaluate the system’s performance and feasibility under various global solar irradiance patterns, representing diverse geographical locations and seasonal conditions, to ensure its global applicability for SDG 7 and SDG 13.

The model simulates a closed-loop system where heated coolant becomes buoyant, rises to a reservoir, and is replaced by cooler fluid from a heat sink immersed in the water body. Pure water is used as the coolant and radiation filter, with its effectiveness analyzed at various channel heights (1, 2, 5, 10, and 20 mm).

Performance Analysis and Contribution to Sustainable Development

Key Findings on System Efficiency and Temperature Regulation

The numerical simulations provide compelling evidence of the system’s effectiveness in promoting the objectives of SDG 7 and SDG 12. The integration of the NCCL and radiation filter yields significant performance improvements over standard FPV panels.

• Temperature Reduction: The system reduces the daily average PV cell temperature by up to 15 K compared to a standard FPV panel without cooling. This directly mitigates thermal degradation, enhancing panel lifespan and aligning with SDG 12.
• Efficiency Gains: The lower operating temperatures lead to an electrical efficiency increase of approximately 3%. This gain, achieved passively without additional energy input, makes clean energy more affordable and accessible (SDG 7).
• Thermal Performance: The NCCL system contributes up to 64.48% of the thermal convective cooling through natural convection alone, demonstrating a highly effective and sustainable thermal management strategy.
• Radiation Filtering: The water-based filter effectively absorbs infrared radiation outside the useful spectral range of c-Si cells, preventing this energy from becoming waste heat and further improving the system’s overall efficiency.

Optimising Design for Global Applicability (SDG 7 & SDG 13)

The study analyzed the system’s performance by varying key design parameters to identify an optimal configuration for widespread adoption.

• Cooling Channel Height: A channel height of 10 mm was identified as the optimal balance point, achieving near-maximum thermal performance without significant over-filtration that could reduce useful photon flux. This optimization ensures the technology is both effective and resource-efficient.
• Tube Spacing: A tube spacing of 100 mm was found to be sufficient, as reducing the spacing further to 50 mm did not yield significant additional temperature reduction. This finding helps optimize material use and cost, contributing to the economic viability required for SDG 9.
• Global Irradiance Conditions: The system was tested under maximum, minimum, and reference solar irradiance scenarios corresponding to different global locations and seasons. The 24-hour simulations confirmed that the cooling loop effectively regulates temperature and resets overnight across all conditions, demonstrating its robustness and reliability for global deployment in the fight against climate change (SDG 13).

Economic and Environmental Viability (SDG 12, SDG 6, SDG 14)

The proposed FPV-NCCL system demonstrates strong potential for economic and environmental sustainability. While the initial capital expenditure is slightly higher, previous analysis indicates that the improved electrical efficiency reduces the Levelized Cost of Electricity (LCOE) by up to 10.19% and shortens the payback period by up to 11.90%. This economic advantage is crucial for accelerating the adoption of clean energy technologies. From an environmental perspective, the closed-loop system uses pure water, minimizing the risk of contamination to water bodies (SDG 6 and SDG 14). The simulated thermal discharge remains well within acceptable ecological limits, ensuring that the technology supports decarbonization efforts without harming aquatic ecosystems.

Conclusion: A Scalable Solution for Global Clean Energy Infrastructure

This study successfully demonstrates, through multi-physics modelling, that a hybrid radiation filtering and passive cooling strategy offers a significant advancement for floating photovoltaic systems. The findings present a clear pathway toward more efficient, reliable, and sustainable solar energy generation.

• Contribution to SDG 7: The system increases electrical efficiency by 3% and reduces operating temperatures by up to 15 °C without consuming additional energy, making clean energy more affordable and effective.
• Contribution to SDG 9: The novel, optimized design and the development of a 3D simulation tool represent key innovations in sustainable energy infrastructure.
• Contribution to SDG 12: By mitigating thermal degradation, the system enhances the lifespan of PV panels, promoting responsible production and consumption patterns.
• Contribution to SDG 13: The technology’s proven effectiveness under diverse global conditions confirms its potential as a scalable solution to accelerate the transition to renewable energy and support global climate action.

The practical feasibility and demonstrated performance improvements establish this FPV-NCCL system as a promising technology to help achieve global sustainable development targets.

Analysis of Sustainable Development Goals (SDGs) in the Article

SDGs Addressed or Connected to the Issues

The article on the novel floating photovoltaic (FPV) system addresses several Sustainable Development Goals through its focus on enhancing renewable energy technology, resource efficiency, and environmental considerations.

1. SDG 7: Affordable and Clean Energy

   The core of the article is dedicated to improving the efficiency and performance of solar photovoltaic systems, a key source of clean energy. By developing a technology that increases electrical output, the research directly contributes to making clean energy more effective and potentially more affordable.

   • Evidence from the article: The study aims to improve the “electrical performance of the floating photovoltaic system,” achieving a “3% increase in electrical efficiency” and reducing operational temperatures to sustain and improve “energy output of PV system.”

2. SDG 9: Industry, Innovation, and Infrastructure

   The research presents a “novel design” and an “innovative solution” for FPV systems. It involves developing advanced simulation models (“three-dimensional multi-physics thermal model”) to optimize a new technology (the Natural Convection Cooling Loop). This aligns with SDG 9’s emphasis on fostering innovation and upgrading technological capabilities for sustainable industrialization.

   • Evidence from the article: The study’s objective is to “develop a reliable three-dimensional simulation tool to model the buoyancy-driven motion of NCCL for FPV panels” and “optimise the cooling loop geometry,” which represents an advancement in clean energy infrastructure technology.

3. SDG 13: Climate Action

   By enhancing the efficiency of solar panels, the research contributes to making renewable energy a more viable and competitive alternative to fossil fuels. The widespread adoption of more efficient solar technology is a critical strategy for reducing greenhouse gas emissions and combating climate change.

   • Evidence from the article: The technology is designed for “global FPV power plants” and its performance is assessed under various solar irradiance levels worldwide, indicating its potential for global decarbonization efforts.

4. SDG 6: Clean Water and Sanitation

   The article explicitly mentions that a key advantage of FPV systems is their positive impact on water resources. By covering water bodies, these systems can help conserve freshwater, a critical issue in many parts of the world.

   • Evidence from the article: The introduction states that one of the “additional advantages of FPV systems are the reduction of the rate of evaporation from the water body.”

5. SDG 11: Sustainable Cities and Communities

   The article highlights that FPV systems address a major challenge for large-scale solar energy deployment: land use. By utilizing water bodies, FPVs free up land for other essential uses like agriculture or housing, contributing to more sustainable land management in and around human settlements.

   • Evidence from the article: FPV is described as an “innovative solution to tackle the central problem of extensive and expensive land requirements for solar farms.”

6. SDG 14: Life Below Water

   The discussion section acknowledges and addresses the potential environmental impacts of FPV systems on aquatic ecosystems. The study shows that the proposed design minimizes thermal pollution, thereby considering the health of life below water.

   • Evidence from the article: The discussion notes that the proposed closed-loop system uses pure water and that the “simulated temperature increase remains well below 10 °C, which is within acceptable ecological thresholds,” mitigating potential harm to aquatic habitats.

Specific Targets Identified

Based on the article’s content, the following specific SDG targets can be identified:

1. Target 7.2: Increase substantially the share of renewable energy in the global energy mix.

   The research directly supports this target by making a renewable energy technology (solar PV) more efficient and reliable. An increase in efficiency (“3% increase in electrical efficiency”) makes solar power more economically attractive and productive, encouraging its wider adoption and thus increasing its share in the energy mix.

2. Target 7.a: Enhance international cooperation to facilitate access to clean energy research and technology… and promote investment in energy infrastructure and clean energy technology.

   This scientific paper is a form of international knowledge sharing. The research, funded by Indonesian and UK institutions and involving researchers from multiple countries, assesses the technology’s viability in “five selected global sites from the northern to the southern hemispheres,” facilitating the global transfer of clean energy knowledge.

3. Target 9.4: Upgrade infrastructure and retrofit industries to make them sustainable, with increased resource-use efficiency and greater adoption of clean and environmentally sound technologies.

   The proposed Natural Convection Cooling Loop (NCCL) is a technological upgrade for FPV infrastructure. It is a “passively cooled” system that improves energy output without consuming additional power (“does not require energy supply to operate”), representing an increase in resource-use efficiency and a “clean and environmentally sound” technological advancement.

4. Target 9.5: Enhance scientific research, upgrade the technological capabilities of industrial sectors… and encouraging innovation.

   The entire study is an exercise in enhancing scientific research. It aims to “Advance our understanding of the multi-physics interactions in NCCL and radiation filter modelling” and develop a “novel approach that incorporates radiation filtering within the NCCL system.” This directly contributes to upgrading technological capabilities in the renewable energy sector.

5. Target 6.4: By 2030, substantially increase water-use efficiency across all sectors and ensure sustainable withdrawals and supply of freshwater to address water scarcity.

   The article mentions that FPV systems lead to a “reduction of the rate of evaporation from the water body.” This directly contributes to increasing water-use efficiency by reducing water loss from reservoirs, which is a form of conserving freshwater resources.

Indicators Mentioned or Implied

The article provides several quantitative and qualitative indicators that can be used to measure progress towards the identified targets.

1. Indicator for Target 7.2 (Renewable energy share):

   • Electrical Efficiency Increase (%): The article quantifies the improvement, stating a “3% increase in electrical efficiency.”
   • Power Output Increase (%): Previous studies cited in the article show an “increase in electrical power output of 7.4‒13.2%.”
   • Reduction in Operating Temperature (°C): The system can reduce the “daily average temperature of the floating photovoltaic system by up to 15 °C,” which is directly linked to improved and sustained power generation.

2. Indicator for Target 9.4 (Adoption of clean technologies):

   • Thermal Convective Cooling Contribution (%): The system provides a “contribution in thermal convective cooling by up to 64.48%,” quantifying the effectiveness of the passive cooling technology.
   • Levelised Cost of Electricity (LCOE) Reduction (%): The discussion mentions a previous study where the LCOE “was reduced by up to 10.19%,” indicating improved economic sustainability.
   • Payback Period (PP) Reduction (%): The same study showed the PP was “shortened by up to 11.90%,” a clear indicator of enhanced financial viability for clean infrastructure.

3. Indicator for Target 6.4 (Water-use efficiency):

   • Reduction in Water Evaporation: While not quantified with a percentage in this specific study, the “reduction of the rate of evaporation” is stated as a key benefit and serves as a qualitative indicator of improved water conservation.

Summary Table of SDGs, Targets, and Indicators

Source: nature.com