Smart coatings on glass and other substrates have the potential to create added value in a huge range of applications, but this can only be realized if they can provide sufficient performance enhancement at the right price. In the energy industry, the key driver is the desire to improve energy efficiency, and this is especially true in the renewable energy sector. We expect to see increased demand for coatings for solar panels and wind turbines as photovoltaics (PV) and wind energy become more prevalent and improved efficiency and low maintenance costs become increasingly important.
Smart coatings in the PV sector can provide antimicrobial and self-cleaning properties that can prevent the accumulation of microbes, debris, and dust particles on solar panels, thereby increasing the useful life of the panels and improving the energy conversion efficiency. NanoMarkets believes that the established market for solar panels and the growing demand for improved power generation capabilities will create additional opportunities for self-cleaning multifunctional smart coatings in the photovoltaic market.
Coating requirements in the wind energy sector also focus on reducing the amount of debris and contamination to improve energy efficiency, but in this case the goal is to avoid damage to wind turbine blades. Protective self-repairing wind turbine coatings prevent damage from airborne particles and keep turbine blades clean and free from contamination.
Going forward, the wind energy industry is expected to demand multifunctional self-healing and self-repairing coatings to reduce maintenance costs with minimal need for human intervention. NanoMarkets believes that the interest of the wind energy industry will boost research efforts in this domain, leading to the commercialization of these coatings.
An Emerging Market for Self-Cleaning Solar Panels
One problem with solar panels is that efficiency gradually decreases over the lifetime of the panel as accumulation of dust and debris limit the amount of light that can be absorbed by the solar cells. Manual cleaning is inconvenient and expensive, so self-cleaning films can provide a real value-added feature.
Hydrophobic coatings appear to be an excellent solution for solar panels. They work like a shield, repelling water and preventing dirt and grime from clinging to the glass. Hydrophobic coatings are especially useful in rainy climates.
nanoShell in the U.K makes a silane-based hydrophobic coating. It repels water molecules much better than an uncoated panel, preventing debris like bird droppings and tree sap from sticking to the panel surface. It also improves PV efficiency in inclement weather and saline environments.
One drawback with hydrophobic coatings is lifetime. Most of these coatings have a lifespan of only three to ten years in exterior applications, which is much shorter than the expected lifespan of a solar panel. The nanoShell material claims a lifetime of five years, after which the solar panel would presumably need a new coating application. This issue, along with high cost, limits market penetration of these materials.
The dominant coating material for PV applications, and in fact for all self-cleaning smart coating applications today, is titanium dioxide (TiO2). In the PV space, inorganic coatings based on TiO2 nanoparticles are designed to prevent dust accumulation. These have an advantage over hydrophobic coatings in that they can last 10 to 15 years.
Such coatings act as a photocatalyst, absorbing UV rays from sunlight, and can enhance the power generation capabilities of solar panels by as much as 25 percent. TiO2 coatings are hydrophilic and prevent water droplets from forming on the surface; instead, a thin film of water covers the entire surface to keep the surface clear and free from dust particles.
Hydrophilic coatings work in areas with an abundance of sunlight and frequent rainfall. The use of titanium dioxide also imparts stability to the coating. One limitation, however, is these coatings only break down organic dirt, not inorganic matter. These coatings are not effective in removing debris such as tree sap.
NanoMarkets believes that TiO2 coatings will continue to dominate the market for self-cleaning coatings in PV applications, despite limitations in the type of dirt they can remove. They cost much less than hydrophobic coatings and have a huge lifetime advantage, and this should be sufficient to ensure their continued dominance in this space.
As solar energy production grows through the rest of the decade, so will the need for smart coatings in this sector. NanoMarkets forecasts the market for smart coatings for solar panels to grow significantly, from $50 million in 2014 to $1.2 billion by 2020.
Markets for Wind Turbine Protection
Wind turbine blades need to withstand especially harsh environmental conditions, and smart coatings that reduce wear and tear can enable turbines to run longer without maintenance, reducing operating costs. Research shows that airborne sand and rain droplets can reduce the energy output of typical wind turbines by up to 20 percent.
Some of the most established brands of wind turbine coatings are based on polyurethanes, but there is a trend in the industry toward smart coatings that do more than protect the wind turbine blades from the elements. These new coatings claim to actually repair minor damage to the blades, help operators detect the extent of damage to the blades, or increase energy generation efficiency.
One example is a new type of smart coating system comprised of a composite material covered with a top layer of microencapsulated polymer spheres. These minute spheres undergo color changes in response to different levels of damage, and thus act as a visual indicator. In addition, the spheres contain resins that are released according to the level of damage, and thus the coating is also self-healing.
While these new materials are still in development, useful polyurethane-based coatings are commercially available today from large, established material manufacturers such as BASF, PPG, 3M, and Jotun. Some of these incorporate multiple components that extend service life and provide corrosion or abrasion resistance. For example, 3M makes a two-component polyurethane Wind Blade Protection Coating that is especially useful in offshore locations and deserts, where damage from airborne sand is a major concern.
NanoMarkets believes that the support of major material manufacturers, along with continuous worldwide, government-led push for alternative energy sources such as wind energy, will drive an increase in cost-effective solutions to improve efficiency and lifetime of wind turbine blades.
While wind power doesn’t have the cachet or market penetration of solar power, worldwide wind power capacity is growing at a rate of 8 to 10 percent per year. Only a very small fraction of wind turbines, however, include smart coatings, making this a very small market. Smart coatings for wind energy applications are relatively expensive – around $6 per Watt – and so these coatings need to provide sufficient operational cost savings in order to convince the industry that they are worthwhile.
We do expect that smart coatings for wind turbine blades will be able to demonstrate sufficient performance benefits to be cost-effective. We should see reasonable growth in smart coatings made from epoxies, polyurethanes, and ethyl silicates, and NanoMarkets forecasts the total market for these coatings to be about $58 million by the year 2020.
The key to growth in this market will be the development of more advanced coatings than what are currently commercially available. NanoMarkets believes that the commercial future of smart energy coatings will hinge upon the ability of coating manufacturers to offer self-healing and corrosion-sensing coatings for the proactive prevention of damage to energy-generating surfaces, thereby increasing the operating life and operational efficiency of these systems.
