Energy harvesting, also known as power harvesting or energy scavenging, is the process by which energy is derived from external sources (such as solar power, thermal energy, wind energy, salinity gradients, and kinetic energy), captured and stored for small, wireless autonomous devices, like those used in wearable electronics and wireless sensor networks.
History and Development of Energy Harvesting
The earliest research on energy harvesting can be traced back to the 1990s when scientists first began investigating techniques to convert ambient energy like movement, light and heat into usable electricity for powering portable electronics. Since then, substantial advancements have been made in areas like piezoelectric, electrodynamic and thermoelectric energy harvesting technologies. Some key developments include Michael Allen's invention of the thermoelectric energy harvesting wristwatch in 1992 and product launches like the EPFL shoe inserts that harvest energy from walking in 2008. Commercial adoption really took off in the 2010s with the proliferation of smartphones, smartwatches and IoT devices driving demand for compact power sources. Today, energy harvesting is a multi-billion dollar industry with applications ranging from personal electronics to infrastructure monitoring systems.
Types of Energy Harvesting Technologies
There are several types of Energy Harvesting Systems technologies that convert different forms of ambient energy into electricity:
- Photvoltaic/Solar energy harvesting utilizes solar cells commonly made of silicon to convert light into electricity. It has widespread use in powering outdoor sensors, calculators and small devices.
- Thermoelectric energy harvesting exploits the Seebeck effect to generate electric current from temperature differences. It is often used to scavenge heat from body heat, engine compartments, industrial processes etc.
- Piezoelectric energy harvesting captures energy from vibrations, motions and pressure changes using piezoelectric materials like quartz and ceramics. It is suitable for harvesting from human motions, machinery vibrations and fluid flows.
- Electromagnetic/Inductive energy harvesting involves the relative motion between a magnet and coils of wire to induce current through electromagnetic induction. It is effective in harvesting from fluctuating magnetic fields.
- Radio frequency (RF) energy harvesting collects energy from ambient electromagnetic waves in the RF spectrum emitted from sources like Wi-Fi routers, TV and radio signals.
Advantages of Energy Harvesting Systems
Energy harvesting provides some key benefits over conventional battery-powered systems:
- Extended Operational Lifetimes - Harvesting technologies can theoretically power devices indefinitely by continuously capturing ambient energy as long as the energy source exists. This eliminates the need for frequent battery replacement or recharging.
- Reduced Maintenance - With no batteries to charge or replace, energy harvesting systems have very low upkeep requirements. This is well-suited for embedded systems installed in hard-to-reach or hazardous areas.
- Sustainability - By leveraging renewable and waste ambient energy sources, harvesting technologies help achieve net-zero or even net-positive energy systems. This makes them a green alternative to non-rechargeable batteries.
- Independence - Harvesting allows powering of autonomous devices without the need for wired infrastructure or manual intervention. It enhances flexibility and independence of operation.
- Cost Savings - While initial costs may be higher, energy harvesting solution eliminates battery expenses over the long run and lowers total cost of ownership. Simple payback periods are typically only a few years.
Applications of Energy Harvesting Systems
Energy harvesting finds applications across many industries due to its flexibility, extended lifetimes and inherent sustainability:
- Industrial Equipment Monitoring - Harvesting powers condition monitoring sensors installed on machinery, conveyors, pipelines and industrial vehicles to wirelessly transmit operational data.
- Building Automation - It feeds sensor nodes for lighting control, HVAC automation, security and access systems. Ambient energy from motion, temperature differences, solar can be captured.
- Wearables - Harvesting makes self-powered wearable electronics like fitness trackers, smartwatches, soldier gear energy independent through human power scavenging.
- Wireless Sensor Networks - Distributed harvesting-powered sensor networks are deployed for environmental monitoring, precision agriculture, infrastructure inspection and more.
- Transportation - Energy is extracted from vehicle vibrations, thermal gradients to power diagnostic sensors, trackers as well as charge electric vehicles using kinetic roadways.
- Consumer Electronics - Charging smartphones and accessories on-the-go utilizing footfalls, finger taps and ambient Wi-Fi is an emerging application area.
Challenges and Future Outlook
While energy harvesting promises perpetual operation, there are still certain technological hurdles that need to be crossed:
- Efficiency - Conversion efficiencies are relatively low at present, limiting harvested power levels. Efficiency improvement through materials innovation remains an active area of research.
- Intermittency - The intermittent nature of energy sources leads to power fluctuation or temporary absence depending on conditions. Effective energy storage and management is required.
- Cost - Mass production techniques are required to reduce costs of harvesting modules and compete with battery economics, especially for low-power sensors.
But with continued progress, energy harvesting is expected to play a lead role in next generation of sustainable, independent and pervasive solutions across industries. Emerging technologies enabling electrochromic glass, kinetic batteries, ambient RF power transfer are expanding its potential application scope further. Wider commercialization will depend on overcoming current technical and economic barriers, but the future certainly looks promising for this disruptive renewable power paradigm.
Get more insights on this topic: Energy Harvesting Systems
