Ceramics and glass in energy

 

In the energy sector, ceramics and glass are key materials for the fabrication of a variety of products that are used for energy conversion, storage, transfer and distribution of energy, and energy savings.  Wear, temperature and corrosion resistance, transparency, inertness, and insulating, conducting or superconducting characteristics are the most important properties that make ceramics and glass suitable for these applications.

In energy conversion, ceramics and glass are found in solar cells and solar collectors that transform solar energy to electricity; fuel cells and batteries that change chemical to electrical energy; thermoelectric generators that convert heat to power; and gas turbines that produce mechanical energy from chemical energy.

Ceramics are used in the fabrication of solar panels in the form of transparent conductive coatings (TCOs). TCOs are currently based primarily on indium-tin oxide (ITO), which is by far the most popular, followed by aluminum-doped zinc oxide (AZO) and fluorine-doped tin oxide (FTO). Perovskite-based solar cells are also being developed as the next generation of high-efficiency photovoltaic cells. With respect to glass, it is used extensively in solar cells as a substrate on which all different films forming the cell are deposited layer by layer.

Fuel cells and batteries comprise ceramic membranes and separators whose function is to properly direct the flow of ions within the electrolytic cell. Silica, alumina and zirconia are popular materials for producing  separators for liquid electrolyte lithium-ion batteries. In addition, ceramic-based electrolytes are being fabricated for solid-state batteries for electronic devices, consumer products, and electric vehicles. Solid electrolytes are based on lithium-ion-conducting oxides such as (La, Li)TiO₃, Li₉SiAlO₈, and Li₅La₃Ta₂O₁₂.

Thermoelectric generators are being fabricated from ceramic materials, such as n-type perovskite oxides, that have high electrical conductivity but low thermal conductivity so that they are capable of converting heat to electricity. Thermoelectric materials are becoming of interest for energy harvesting applications, where electricity is generated from recaptured heat. An example is heat produced from the human body that is converted  to power for wearable devices. In thermoelectric generators, ceramics are also used as substrates that enclose the device.

Ceramic matrix composites (CMCs) have been introduced in the fabrication of components for gas turbines and microturbines, such as vanes, airfoils, and shrouds, for power generation.  CMCs are also finding application in nuclear reactors to manufacture fuel pellets and protective casings for spent nuclear rods.

Ceramic capacitors, and even more importantly, supercapacitors are used for energy storage. Typically, high-temperature supercapacitors, which have a construction somewhat in between that of a capacitor and a battery, contain a ceramic separator that prevents charge recombination. Supercapacitors have very high capacitance measurable from microfarads to kilofarads. They find application as a source of energy in electronic devices (e.g., mobile phones), solar cells and wind turbines (to store energy produced by the cell or the turbine), electric and hybrid vehicles, as well as in power grids.

Ceramics are also used in thermal energy storage, where energy is stored in the form of latent heat for later use. Porous or honeycomb structures are manufactured for this purpose based  on ceramic formulations that allow for high heat-transfer surfaces and large thermal capacities. These structures can act as heat storage systems by warming up when a hot fluid passes through them and subsequently releasing the heat, or these structures can be used as containers for phase change materials that change status when heated or cooled, thus storing or releasing energy.

Glass and porcelain insulators are used in high-voltage power lines to separate and orient lines and for safety purposes, whereas high-temperature superconducting cuprates in the form of wires and magnets have been introduced to transfer and distribute electrical energy without losses.

As insulating materials, ceramics and glass are key components of energy saving solutions. Refractory and non-refractory bricks, porcelain components, porous structures, fibers, thermal barrier coatings, thermal protection systems, and smart glass are different forms in which these materials are manufactured to satisfy the specific requirements of different energy saving projects.

Within the energy sector, wear-resistant ceramics are also used in machinery for energy production, including bearings, valves, seals, spheres, pumps, sheaths, and tubes for wind turbines, gas turbines, oil and gas extraction equipment, and other systems.

The main applications of ceramics and glass in energy are illustrated in the table below.

Main applications of ceramics and glass in energy

Where?	What?	Examples
CERAMICS
Energy conversion	Transparent conductive coatings	1
	Separators and coatings for fuel cells and batteries	2
	Solid electrolytes for batteries (for example, flexible lithium ceramic batteries (left) and parallel lithium ceramic batteries (right))	3
	Materials for thermoelectric generators	4
	Coatings and parts for gas turbines	5
Energy storage	Capacitors and high-temperature supercapacitors	6
	Porous and honeycomb structures for thermal energy storage	7
Energy distribution	Insulators for power lines	8
	High-temperature superconducting wires and magnets
Energy savings	Insulating products	9
GLASS
Energy conversion	Solar panels	10
	Insulators for power lines	11
	Smart glass	12