Fossil fuels like coal, petroleum, natural gas and oil were created from organisms such as plants and animals that died millions of years ago. Over time, after the process of fossilisation (of organic matter becoming preserved in a hard-petrified form) we got deposits of carbon-rich resources such as coal and oil. According to Octopus Energy, the world is expected to run out of known oil deposits by 2052, while coal and natural gas are expected to last until 2060. Because these fossil fuels take millions of years to create, depleted sources cannot be replenished. Renewable energy like solar, hydro, and wind energy are the most suitable and environmentally sound solutions in this scenario.
Energy harvesting uses energy found in the ambient environment and converts it into usable electrical energy. This energy is conditioned for either direct use or can be accumulated and stored as a source of power for applications at a later time. Here, we examine how energy harvesting can provide the energy required to power devices and circuits, and offer solutions for battery-operated devices.
What’s driving the global energy harvesting market
Many factors drive the global energy harvesting market. The demand for safe, power-efficient and durable systems that require little or no maintenance is increasing on a daily basis. Since technology is evolving faster than ever, the extensive application of IoT devices in building and home automation is increasing. Another major driving factor is the cost of renewable energy. The less expensive fuel for automobiles is electric energy versus fossil fuels. Electric cars are becoming more dominant over time. Studies indicate that the number of internal combustion engine (ICE) vehicles will reduce by about 50 per cent by 2030.
Sources of energy
To generate power, there needs to be an energy source from which to harvest. Some main sources of energy are photovoltaics, kinetic energy, as well as pyroelectric, piezoelectric and radio frequency (RF) energy (Figure 1).
Let’s discuss each of these energy sources.
Photovoltaic energy: Photovoltaic (PV) devices generate electricity directly from sunlight. The solar cell is an example of a photovoltaic device. Solar cells are made of a material called semiconductors. Because of the structure of the semiconductor material, when sunlight strikes it, electrons are released and forced in one direction, creating a flow of electrical current.
Kinetic energy: The kinetic energy of an object is the energy it can produce because of its motion. Wind turbines, ocean buoys and hydroelectric plants are all examples of kinetic energy sources, from the motion of wind or water. Wind turbines create electricity by turning the propeller of the turbine around a rotor, which spins a generator, creating electricity. Just like the wind turbines, hydroelectricity is produced by spinning a generator using the flow of water.
Pyroelectric and piezoelectric energy: Pyroelectricity and piezoelectricity both have high thermodynamic efficiency and can only be used on a micro level. Pyroelectricity is the ability of certain materials to create electric current based on temperature change. Piezoelectricity is the ability of certain materials to convert mechanical energy such as sound or pressure into electrical energy.
Radio frequency energy: A radio frequency (RF) energy harvesting system can convert electromagnetic energy into usable direct current voltage. The system usually contains an antenna and a rectifier circuit that captures the RF power, which is alternating current, and converts it into DC power.
Capacitors used in energy harvesting storage
Almost all energy harvesting scenarios require some sort of energy storage. A specialised DC-DC converter takes in power from the transducer and outputs electricity used to power devices. The system converter requires careful electronics design to minimise power losses. The energy storage balances the energy supply and demand. For applications where energy is used as soon as it is collected, storage is not necessary and, usually, an aluminium electrolytic capacitor is used. Determining the energy storage needed in an energy harvesting system depends greatly on the application.
The world is expected to run out of oil deposits by 2052, while coal and natural gas are expected to last until 2060. As the demand for energy continues to increase, there is no choice but to turn to alternative and sustainable options. Energy harvesting uses energy from the ambient environment such as photovoltaics and kinetic energy, as well as pyroelectric, piezoelectric and RF energy and converts it into usable electrical energy. As hours of life are one of the key parameters, designers must choose robust, long-life capacitors and work with the manufacturer to ensure their application will continue to operate for years to come.
This article is contributed by Mouser Electronics.