Energy Harvesting: A Realistic Alternative in Times of Energy Crisis?

Table of contents

1. What does energy harvesting mean?
2. Forms of energy conversion in energy harvesting
3. Potentials and opportunities of energy harvesting
4. Challenges and risks of energy harvesting
5. The future of energy harvesting

Energy harvesting, i.e. harvesting environmental and ambient energy, is not a new invention – but is experiencing a new boom in times of energy scarcity and inflation. Fossil fuels have become scarce and expensive. The reason: this stored form of energy is only available in limited quantities. Residual energies of already existing energy sources from the environment seem to be the means of choice. In addition to less dependent and constant energy availability, they also promise positive effects on the planet.

In which areas is the method already being applied? Where does the potential lie? And: what challenges await the industry? This magazine article provides the answers.

What does energy harvesting mean?

The term energy harvesting refers to the extraction of electrical energy in small quantities as a byproduct of using existing energy sources from the environment. The classic examples of what this energy can be extracted from are light radiation, waste heat, and ambient temperature.

Motion energy from air currents and vibrations also belong to this spectrum. Energy harvesting (EH) appears particularly promising in terms of breaking away from external or wired power supplies (wireless technologies). Energy recovery from the use of existing sources also reduces dependence on fossil fuels or other limited resources.

Forms of energy conversion in energy harvesting

Conversion methodology, which converts energy from the environment into electricity and powers electronics, is used in many fields:

Photovoltaic conversion

Energy harvesting from solar panels is probably one of the most well-known and well-established application areas of energy harvesting. It relies on the photoelectric effect: Electrical energy is generated from ambient light. Photovoltaics is already used for countless everyday applications. Solar cells, lighting solutions or water pumps are just a few examples.

Piezoelectric conversion

In the piezoelectric effect, mechanical pressure or vibration, i.e. the application of force, causes electrical energy to be generated. The best-known application of this mechanism is in piezo igniters. Here, the mechanical energy is applied to a switch or trigger, which in turn causes a spark to produce a desired reaction. Applications range from ultrasonic medicine to stress measurements using piezoelectric sensors and automotive electronics.

Thermoelectric conversion

Temperature differences generate electrical voltage, which in turn generates current. This form of conversion uses the waste heat from motors or process equipment, for example, and leads to an improvement in energy efficiency. The method can also be used to monitor systems. Thermoelectric sensors send signals when a thermal over- and under-limit is reached. These alerts help protect various devices and machines.

Electromagnetic conversion

This phenomenon occurs when there is movement or difference in current in electromagnetic fields. Electromagnetic waves (radio frequency signals) from cell towers, WLAN routers and Bluetooth devices can also be used for energy harvesting. With the help of an antenna, the signals are received and then supply Internet of Things (IoT) devices with power – recharging dead batteries, for example.

Potentials and opportunities of energy harvesting

• Relief for the environment: If one looks at the concept of energy harvesting from an ecological point of view, there are definitely advantages to be seen. The use of energy that has already been generated by other processes, as well as the generation of energy from unlimited or renewable environmental resources, leads to lower emissions of greenhouse gases and thus to a reduced burden on the ecosystem. In the long run, any alternative energy source – if sufficiently efficient – also reduces dependence on expensive and scarce fossil fuels.
• Increased self-sufficiency for devices of the IoT: atterie and battery charging is still a costly affair. In the IoT in particular, maintaining power takes a particularly long time. Many battery or accumulator-powered machines need to function in places where there is no reliable power supply, for example. As soon as the charge of energy runs out, it has to be renewed manually – causing high, avoidable costs. Energy harvesting can extend the functional times of equipment because energy is constantly supplied from the immediate environment.

Challenges and risks of energy harvesting

• Complexity of the application: External factors such as intense, erratic weather and temperature fluctuations strongly influence the efficiency and performance of the systems. This requires particularly robust design of relevant systems and equipment. Unforeseen changes can also lead to deviating availability of ambient energy. Only with particularly economically designed systems is it possible to consistently generate sufficient energy despite these fluctuations.
• Special requirements: In addition to environmental factors, the respective application area also poses a wide variety of challenges. In M2M communication (M2M = machine to machine), for example, there is always a sudden increase in energy consumption during transmission and reception. The energy requirement is therefore not constant. If such a system is powered by energy harvesting, it must be ensured that sufficient energy is always available, even at peak consumption times.
• Compatibility and integration: In most cases, EH is not taken into account during the basic development of a system, but is integrated afterwards. The addition afterwards, however, often raises new problems, since different technologies and modes of operation collide. Keyword: compatibility!
• Cost efficiency and economy: Energy harvesting is not a universal solution and usually requires individual technologies to function successfully in the respective application areas. In addition, the converted energy often has only a very low efficiency. This usually leads to high costs. The complexity of the processes requires special expert knowledge, and once the systems are in operation, they must be able to meet high expectations.

The future of energy harvesting

Energy harvesting alone cannot solve the energy crisis at this time due to the low cost effectiveness of the methodology. We already know many of the counterpoints from the world of smart living including smart devices and smart buildings. One thing is certain, however: the development of energy-learning processes is an important adjusting screw for securing the energy supply in times of bottlenecks in individual use cases.

The cost-benefit ratio and the specific requirements in the desired area of application remain important factors to be weighed up with regard to energy harvesting.