Batteries or Supercapacitors? Why Not Both?

When it comes to choosing between batteries and supercapacitors, it can be a tough decision. Batteries provide a steady source of power but can suffer from capacity fading over time. Supercapacitors, on the other hand, offer fast charging and discharging capabilities but have limited long duration storage capacity. That's why many are turning to hybrid systems that combine the strengths of batteries and supercapacitors to create an efficient and reliable power solution. Let's take a look at the differences between batteries, supercapacitors, hybrid energy storage systems that combine them together, and how Capacitech’s products overcome challenges to offer its customers the storage system of the future.

Before we go into details, here is a quick summary.

What are batteries?

Batteries are energy storage devices that use electrochemical reactions to store electrical energy as chemical energy, which can then be converted back into electricity when needed. Batteries have a relatively high energy density compared to other forms of energy storage, making them the ideal choice for many applications that require long-duration storage. They also have a low self-discharge rate, meaning they only lose a small percentage of charge when not in use.

Although batteries offer several advantages over other forms of energy storage, they also have some shortcomings. As a result of energy in batteries being stored as chemical energy, the power density is typically lower than some other energy storage devices, meaning it cannot deliver a lot of energy very quickly in a short period of time. Batteries that are subjected to loads that require bursts of power can degrade quickly, wasting their capacity and even shortening their operating life. Batteries also already have a limited cycle life, which can be as short as 500 cycles depending on the battery chemistry.

What are supercapacitors?

Supercapacitors are another type of energy storage device. Unlike batteries, which store energy through chemical reactions, supercapacitors store the majority of their energy electrostatically. As a result, they can charge and discharge energy much faster than batteries, with power densities typically 10 times greater.

The biggest advantage of supercapacitors is their high power density, allowing them to supply large amounts of power in short bursts. This makes them ideal for applications that require quick bursts of energy such as starting a motor or pump. Supercapacitors also have a much longer lifespan than batteries since there are no chemical reactions taking place, reaching cycle lives of up to one million.

Supercapacitors are more stable across a wider range of temperatures compared to batteries, allowing them to be used in locations with extreme temperatures. They can be operated in temperatures that range from -40C to 65C (-40F to 149F), whereas batteries like the Panasonic NCR18650GA Li-ion battery can only be operated in temperatures from 0C to 45C (32F to 113F).

However, supercapacitors have a much lower energy density than batteries and are not suitable for applications that require long-term storage of energy. Supercapacitors also have a high self-discharge rate, meaning they will lose a good chunk of their charge when not in use, and are typically more expensive than batteries.

What are the benefits of using a hybrid system?

By combining the complementary advantages of supercapacitors and batteries, these systems can fit in very well in applications with dynamic, fluctuating loads that also require longer duration storage requirements too. Cleantech applications like electric tug boats or solar farms operating in areas with moving cloud coverage are prime candidates.

As previously mentioned, supercapacitors are well suited for applications that require quick bursts of power, such as starting a motor or providing peak power demands for brief periods. These devices can quickly charge and discharge very large amounts of power, making them ideal for short-term or "turn-on" needs, like accelerating an electric scooter. On the other hand, batteries are great for providing steady, longer-term power, which can provide the steady-state power needed to keep the electric scooter moving, for example.

When used together in a hybrid energy storage system, the two technologies can complement each other and provide more stability to the overall system.

What are the tradeoffs of using a hybrid system?

However, a hybrid system does not come without complications; one of the biggest being the lack of physical space for it. Size and space restrictions force designers to choose one energy storage technology over the other, rather than choosing both. Essentially, batteries and supercapacitors compete for space in an energy storage system. On a solar farm, for example, a specific amount of space may be allocated for long-duration storage (batteries). To add supercapacitors to the farm, which would provide the extra power needed to keep loads on during periods of moving cloud cover, designers would have to either remove batteries to make room for the supercapacitors (less long-duration storage), increase the size of the energy storage container (less space for solar panels), and buy more land (added cost).

Capacitech’s Power Storage Cable revolutionizes hybrid systems

Capacitech's Power Storage Cable is designed to alleviate the engineering tradeoffs that make it difficult to combine batteries and supercapacitors. The Power Storage Cable hides supercapacitors and power electronics inside a power cord, thus avoiding the design tradeoffs associated with using a hybrid system, allowing customers to utilize space that is not traditionally used for energy storage. This allows for the creation of a discrete and distributed network of supercapacitors running between solar panels, batteries, inverters, and the loads they are powering. Our cables provide the advantages of supercapacitors to create the ideal energy storage system, allowing for a greater level of efficiency and flexibility in energy storage systems without the tradeoffs typical of hybrid systems.