POWER SUPPLY FOR A CLOCK Using Supercapacitor And Small Solar Panels

Solar photovoltaic panels produce energy only while the Sun shines, but lighting is required mainly during night. So, the solar energy needs to be stored, which is now generally done through lithium-ion batteries.

The lithium-ion batteries have some limitations. For one, cost of lithium-ion batteries is increasing year after year, so these are suitable for high-priced mobile items like vehicles and smartphones only. For stationary applications we need to find alternatives.

Second, lithium-ion batteries can handle a few thousand charge/discharge cycles only. This means the batteries need to be replaced after about five years of use.

Third, re-cycling of lithium-ion batteries is challenging and expensive. Also, India does not have lithium mines, so we are completely dependent on imports.

Fourth, lithium-ion batteries also use metals like nickel and cobalt. Therefore, these batteries are not environment-friendly. Besides, lot of mining is required to get these metals.

Hence, it becomes important to explore other devices for energy storage. Here we will explore use of supercapacitors for energy storage for low power but widespread applications.

Supercapacitors (or ultracapacitors) are also called electric double-layer capacitors. They use porous carbon electrodes and store energy in the form of electric field. Unlike batteries, which store energy in electrochemical form, these offer high-value capacitance, which can be measured in Farads. Typical working voltage of these capacitors is low (2.7V).

As of today, the cost of supercapacitors is high. Just for storing a few watt-hours of energy we have to use several capacitors. Hence, the cost of even small low-power systems is fairly high.

However, there are some ways the cost of supercapacitors can be reduced, a couple of which are suggested below.