Energy harvesting, electromagnetic microgenerator, renewable energy
The need for new clean energy sources driven by the growing worldwide energy demand has boosted the emergence of an intense research activity seeking new ways of efficiently managing energy resources. Among the so called energy harvesting techniques, allowing scavenging from clean and free residual environmental sources (light, vibrations, thermal gradient), the use of mechanical energy in form of vibrations is an interesting option since it does not depend on sunlight level. However, existing electromagnetic generators cannot be used to produce electricity from low frequency oscillations like the ones produced by swell or wind, since these devices need higher frequencies to operate. The main goal of this work is the development of a device that generates electricity from vibrational energy coming from either sea waves or human motion. It allows auxiliary power supply in fishing vessels (e.g. genset) through rechargeable battery storage, or direct power for low consumption electronic devices.
According to the FAO, in 2004 the world's fishing fleet consisted of 4 million vessels. The Council Regulation (EC) of 2006 on the European Fisheries Fund, aimed at ensuring the conservation and sustainable use of marine resources, provides measures to adapt the EU fishing fleet like energy yield promotion and engines replacement (forbidding an increase in the catch capacity or the power of the fishing vessel's engine). This Regulation means an opportunity for the technological renewal of small-medium fishing ships, which could benefit from the technology presented in this work. Moreover, the need for electricity in remote locations where no direct wiring to the mains is possible is usually met by the use of batteries. However, not only batteries are unable to provide power infinitely but also recycling of disposed ones is an arduous task, since most of them contain hazardous materials, which can pollute the environment. The presented technology provides a clean solution to this problem.
The energy transduction mechanism of this technology is by definition independent on sun light. The innovative design of this device maximizes the electric energy generated from vibrations, producing a power density up to 20 mW/cm3 (higher than photovoltaic solar panels performing at full throttle). Unlike conventional sources of power like batteries (which have to be either recharged or disposed and replaced), this system is maintenance-free, hermetic, wearless, and robust, since it should show shock and weather inclemency resistance. Also, it can be easily adapted to any size and geometry, allowing its multiple application fields. Low cost of the required materials and use of a well-established technology diminish manufacturing costs as compared with other clean technologies (like Silicon-based photovoltaics). Besides, microsystems technology allows batch fabrication of a large number of identical microgenerators. This permits assembly between several modules and the collection of large amounts of energy.
The performance of this technology is optimized for power supply of fishing boats of small-medium size, with higher rocking than bigger, more stable fishing vessels. It works either on the high seas, or in situations of anchoring or docking. It could also be used to power supply buoys, automatic control systems of autonomous equipment in marine infrastructures (harbors, fisheries), and could be adapted to generate energy from pieces swung by the wind. Individual or assembled microgenerators could either be part of a structural element of the ship (i.e. the deck), or form an auxiliary element. It is considered also the application of this technology for the power supply of low consumption portable electronic devices in situations in which no direct wiring to the mains is possible.
As a first stage of the project an optimization of the generator design was obtained through computer modelling. These simulations allowed the determination of optimal electrical and geometrical parameters that maximizes the electric energy generated by each microgenerator. From these simulations several pre-prototypes were manufactured and tested under lab conditions. The last milestone achieved has been the field testing of these prototypes on a small fishing boat to get information about oscillation frequencies and amplitudes in order to find out which is the most favourable section in the ship hull to place the devices, and also to perform other in-situ complementary measurements. Similarly, all mechanical studies and electrical measurements for the prototype characterization have already started.
At the moment, the task of mechanical and electromagnetic optimization of the microgenerator is under development. The basic design of the generators will be different for the portable and non-portable applications considered. The next stages envisioned after completion of this task include: (1) The development of an electronic system for the control and storage of energy, and its integration into the microgenerator system, and (2) The design and manufacturing of a preindustrial prototype fulfilling all normative regulatory requirements on electronic devices. Once this preindustrial prototype is achieved, this technology will be ready for scalability and commercialization.