Graphene as the Driver of the Energy Revolution:
Advances in Efficiency and Renewable Energy Storage
In today’s context, environmental concerns and climate change have shifted from being a trend to a top priority. This has led to the formation of multidisciplinary teams globally, focused on finding more sustainable technological solutions for energy challenges, such as energy generation and storage, with the additional aim of minimizing emissions.
In this context, thermal energy management through passive technologies, like solar energy, has gained significant importance. Its utilization as an eco-friendly and energetically efficient alternative has seen substantial growth, from its application in domestic settings to electricity generation systems.
However, the natural intermittence of solar energy due to diurnal and nocturnal cycles poses long-term challenges. Hence, it’s imperative to consider complementary technologies like Phase Change Materials (PCMs). These materials can absorb thermal energy from the surroundings to change their state, releasing stored energy for heating or cooling applications in various sectors, including construction, electronics, and aerospace.
Among the well-known PCMs is paraffin, which undergoes a solid-liquid phase change to store latent heat by absorbing thermal energy until reaching its melting point. While paraffins offer advantages such as being safe, reliable, economical, and having acceptable stability for long crystallization-fusion cycles, they also face challenges such as low thermal conductivity and leakage in the liquid state.
Fortunately, PCMs, including paraffin, benefit from advances in nanotechnology, especially when modified with nanoparticles like Graphene. Incorporating Graphene into PCMs like paraffin significantly enhances thermal conductivity and energy efficiency, facilitating solar-to-thermal energy conversion and storage.
What makes Graphene so special?
Graphene, with its exceptional physicochemical properties, is one of the most promising nanomaterials as a co-adjuvant in addressing energy-related challenges. Unlike other carbon nanostructures like diamond, graphite, activated carbon, fullerenes, or nanotubes, Graphene exhibits superior electrical and mechanical properties, with the added advantage of easy combination with other compounds like PCMs to share characteristics and enhance performance. For example, compared to nanotubes, one of the most well-known and studied carbon nanostructures, Graphene boasts higher charge mobility (200,000 cm2 V 1 s 1 Vs. 150,000 cm2 V 1 s 1), greater electrical conductivity (6.6 MS m -1 Vs. 0.35 MS m -1), and higher transmittance (97.0% Vs. 95.7%), making it highly attractive for energy-related applications.
How does Graphene relate to PCMs for solar energy utilization?
Historically, from a sustainable perspective and as a real-world application, architecture is a clear example of solar energy utilization. Starting from ancient times with the construction of adobe walls to trap daytime heat and release it at night, to modern infrastructure using heaters or solar panels, to Trombe walls as a passive heating tool. For instance, Trombe walls comprise materials like glass, wood, steel, aluminum, concrete, and PCMs like paraffin, arranged in special configurations that collectively absorb heat to slowly conduct it into the dwelling.
Through the identification of Graphene’s multifunctional properties and the exploration of its benefits in various sectors, it was found that its integration into paraffin used for passive heating systems can significantly improve thermal conductivity or driving force by up to 164%, showcasing clear superiority over highly efficient hybrid nanoparticles like Cu-TiO2 or Al2O3-MWCNT, whose normal benefits range between 50 and 70%. This means that integrating these technologies into passive heating systems, besides improving thermal comfort throughout the year, would also yield significant energy savings and reduce CO2 emissions.
Solar cells
Another well-known potential application of nanotechnology in the energy sector is the design of the fourth generation of solar panels, which includes the use of two-dimensional nanomaterials like molybdenum disulfide (MoS2), tungsten diselenide (WSe2), and again, Graphene.
Among the most representative advantages that Graphene has demonstrated over other materials are, in addition to its mechanical strength, its high charge mobility, great transmittance, lightness, flexibility, and stability, which have led to significant advances in its performance for solar panel design, increasing its efficiency from 1.5% to 15% in less than 10 years, almost comparable to the efficiency of current cells ranging from 20 to 22%. However, in pursuit of further improving these percentages, experts in the field continue to explore methodologies based on Graphene doping with other structures like silicon, molybdenum hexafluoride, molybdenum oxide, thionyl chloride, trioxionitric acid, gold chloride, boron, oxygen, nitrogen, phosphorus, or sulfur, to reduce its resistance and better harness solar energy.
At Energeia-Graphenemex, the leading company in Latin America in the design and development of graphene-based applications, we are aware of the challenges that Graphene, like any emerging technology, faces, and we are pleased to be part of the select group of researchers and industrialists globally seeking to benefit society, the economy, and the environment with the advantages these wonderful materials can offer.
Thanks to our multidisciplinary team, we have quickly overcome the obstacles that have hindered the arrival of this material to the market in real applications, starting with its large-scale production, with controlled quality and at an affordable cost, as well as with the development of new products with graphene nanoengineering, where controlling its stability and compatibility with compounds and processes used in each application or industry has been fundamental.
Graphene as an ally of renewable energies is still in its early stages, not necessarily due to its manipulation but because of the complexity this sector represents. However, the significant advances made over the past decade should not be underestimated, as they lay the groundwork for the next generations of equipment and technologies.
Redaction: EF/DHS
References
- Jafaryar M, Sheikholeslami M. Simulation of melting paraffin with graphene nanoparticles within a solar thermal energy storage system. Sci Rep. 2023, 26;13(1):8604;
- R. Bharathiraja, T. Ramkumar, M. Selvakumar. Studies on the thermal characteristics of nano-enhanced paraffin wax phase change material (PCM) for thermal storage applications. J. Energy Storage, 73, Part C, 2023, 109216;
- Li-Wu Fan, Xin Fang, Xiao Wang, Yi Zeng, Yu-Qi Xiao, Zi-Tao Yu, Xu Xu, Ya-Cai Hu, Ke-Fa Cen, Effects of various carbon nanofillers on the thermal conductivity and energy storage properties of paraffin-based nanocomposite phase change materials, Applied Energy, 110, 2013, 163;
- Top Khac Le., et al., Advances in solar energy harvesting integrated by van der Waals graphene heterojunctions. RSC Adv., 2023, 13, 31273
