The Human Power Workshop was part of the 1st Energy harvesting Network funded by the EPSRC to establish a network to contribute to the debate that will define a new generation of research challenges for Human Power Generation of devices. The workshop was split into two sessions, one in the morning which focused on energy harvesting for devices outside of the body and the second for devices within the body. The workshop consisted of academics from leading research groups at the forefront of Energy Harvesting in the UK and Europe and also delegates from companies and organisations involved in bringing new and innovative energy harvesting products to market.
The proceedings were started with an opening presentation from Prof. Markys Cain of the National Physics Laboratory (NPL), his talk gave a broad view of Energy Harvesting with a Human Powered theme, broken down into three main types of harvesting technologies:
- i.thermoelectric harvesters i.e. the conversion of energy from thermal gradients to electrical power;
- ii.mechanical harvesters, which he further categorised into:
- -a.Dynamic Energy sources, having a continuous repetitive nature such as vibration and
- -b.Impact Energy, which covers harvesters that tap into energy from non repetitive or complex energy sources such as the human heel strike or the movement of the elbow, knee joint or equally the movement of the entire body itself;
- iii.Biochemical harvesters, which capture energy from multiple sources in our personal and daily environment. The devices could consist of a piezoelectric poly nano-fiber nanogenerator for harvesting mechanical energy, such as from breathing or from the beat of a heart, and a flexible enzymatic biofuel cell for harvesting the biochemical glucose/O2 energy in biofluid.
The debates were stimulated by several speakers in the two sessions; the morning session focusing on in-body harvesting was started by James Patterson from Imperial College London, who gave a presentation on Human Power for Pervasive Sensing in Sport and Healthcare to show the need for further development of implanted sensing technology with energy harvesting in sport and health care. The notion of applying sensors to patients in hospitals has been around for some time; however the difficulty of implanting sensors into the body is that it is very much an invasive process, often requiring surgery. Energy harvesters attached to the sensors could allow the devices to be implanted for longer, or even for the life of the patient. Sensors require batteries, potentially very harmful to the body. These batteries, depending on the sensor data rates could be depleted in days or even weeks and for long term monitoring the replacement of batteries by further surgery is extremely undesirable, firstly because of the discomfort to the patients and also ultimately the cost attached to such procedures. The benchmark for wireless communication is said to be 100µW and in-body devices capable of producing this type of power output are not available as yet but the talk outlined the challenges put forward by the Body Sensor Network group at Imperial College London.
Tracy Wotherspoon of Zarlink Semiconductors presented on their innovative pacemaker powered by an electrodynamic generator via a bladder system inserted into the heart and connected by a silicon tube containing movable rare earth magnets. As the heart beats it squeezes the bladder system pushing the liquid through the tube and taking the magnet back and forth creating a magnetic field through the coil and magnet configuration and thereby generating a small amount of electrical charge to power the pacemaker; the electronic engineer on the project and also the electromechanical lead engineer Giles Stanley mentioned that the current version is able to harvest around half the power it needs, although simulations show a more generous output than the current system is producing in practical tests to operate effectively.
Challenges for future development work are a 10-fold increase in the voltage and doubling of the power output before it can proceed to the next generation of device. This work is under development and the team have clear strategies to overcome these barriers to the adoption of these devices into the mainstream, enabling these devices to remain in-body for the life of the patient.
To conclude the morning session and to facilitate a forthcoming report to be delivered by the Network, the delegates were asked to participate in the debate to define a vision for in-body energy harvesting. Dr Simon Aliwell, and Dr Costis Kompis led the debate to define the challenges, in terms of the drivers which will formulate the directions the research will follow and in terms of technology and science that needs to come about before we can see the technology in common place.
Top image source: TopNews
For more read : Energy Harvesting and Storage for Electronic Devices 2010-2020
