The worldwide energy demand is expected to double by 2040, according to the Global Energy Institute. As an ongoing effort, researchers are looking to replace fossil fuels with renewable energy sources like solar and wind power to sustainably meet this demand.
In 2017, the United States reported 50 gigawatts (GW) of solar power capacity and 80 GW of wind power capacity. Despite these impressive figures, one of the prevailing issues around renewable energy is how to meet continuous energy demands when the energy sources themselves are not constant, considering the variabilities in sunny or windy days.
To effectively replace fossil fuels, we need energy storage systems that can store vast amounts of energy and output it instantaneously to keep pace with demand. For these reasons, researchers are turning to supercapacitors.
Supercapacitors as a Green Energy Solution
A supercapacitor, also commonly referred to as an ultracapacitor, is a capacitor with a very high capacitance value.
Diagram of a supercapacitor system. Image used courtesy of Applied Energy
These devices are a compelling component choice for designers of energy storage solutions for a multitude of reasons. They offer:
- Infinite lifespans
- Simple architectures and manufacturability
- High storage ability and energy delivery
- Fast discharge
- Short charging times
- High performance in low temperatures
Energy attributes of supercapacitors vs. other power sources. Image used courtesy of MDPI and Sustainability
These attributes, especially the ability to discharge very quickly, are essential to supply high power if demand were to instantaneously change, making supercapacitors a useful choice for these energy storage applications.
An Example from EATON
EATON’s XLM supercapacitor module is a helpful example to showcase these advantages. EATON claims this device can offer millions of charge/discharge cycles regardless of the depth of discharge (DoD), which is the amount of energy relative to the system’s total energy discharged from a battery before charging once again. This results in a module lifespan upwards of 20 years.
The XLM supercapacitor comes in a 62 V, 130 F module. Image used courtesy of EATON
The module can also absorb or supply high energy variations, making it a viable candidate for renewable energy systems. Another bonus is that the device is constructed with green materials and is RoHS compliant.
Research Extends the Promise of Supercapacitors
While supercapacitors feature many advantages at face value, developers may still face cost and performance bottlenecks with these components. As such, researchers are doubling down on capacitor development to make this storage solution both accessible on a wide scale and high performing.
Carbide-Derived Carbon for Supercapacitors
One researcher looking to find new materials that can optimize supercapacitor performance is John Chmolia, a doctoral student working at Drexel University’s Nanotechnology Institute. Chmolia is researching the use of carbide-derived carbon (CDC) as a material to build supercapacitors and maximize the capability of the component by changing the pore size of the carbon.
Titanium carbide-derived carbon was used to create electrochemical capacitor electrodes. Image used courtesy of John Chmiola, Drexel University
Originally, people building supercapacitors out of carbon assumed that the maximum pore size correlated with maximized performance, but Chmolia discovered that pores that were much smaller—under a nanometer in size—featured better performance than their larger counterparts. The pores needed to match the ions would pair with them in exact order to obtain a 50% improvement in performance.
Researchers at Texas A&M have also created novel supercapacitors that are completely plant-based biomaterials. The researchers say that in the future, their flexible, lightweight, and cost-effective solution could charge electric vehicles in a matter of minutes.
While implementing biomaterials in these devices makes it difficult to control the resulting electrical characteristics, the team was able to make devices with superior electrical performance. The process of making biomaterials today usually requires hazardous chemical treatments, but the team was able to manufacture these devices using environmentally-friendly processes that are also simpler and lower cost.
Prototype of the Texas A&M supercapacitor. Image used courtesy of Texas A&M
Hong Liang, a contributor to the project from the mechanical engineering department of the school, looked into using manganese oxide nanoparticles for one of the two electrodes for their supercapacitor design since this material is cheaper, more abundant, and safer compared to other transition metal oxides that are popular for making the electrodes.
The team also utilized lignin on the electrode to enhance the poor conductivity of the manganese oxide. This resulted in very stable electrochemical properties along with a specific capacitance that was up to 900 times greater than that of current supercapacitors, all done with 100% environmentally-friendly materials and processes.
Are Supercapacitors the Key to Renewable Energy?
Supercapacitors, especially ones created using eco-friendly materials and processes, are becoming a crucial part of the green movement. Their ability to quickly react to the changes of power demand can be paired with erratic renewable power generation systems like photovoltaics and wind turbines.
Despite performance pitfalls (compared to batteries), supercapacitors have a great deal of promise, especially as new research quickens their adoption.