Edwar Romero

Energy scavenging sources for biomedical sensors

Energy scavenging has increasingly become an interesting option for powering electronic devices because of the almost infinite lifetime and the non-dependence on fuels for energy generation. Moreover, the rise of wireless technologies promises new applications in medical monitoring systems, but these still face limitations due to battery lifetime and size. A trade-off of these two factors has typically governed the size, useful life and capabilities of an autonomous system. Energy generation from sources such as motion, light and temperature gradients has been established as commercially viable alternatives to batteries for human-powered flashlights, solar calculators, radio receivers and thermal-powered wristwatches, among others. Research on energy harvesting from human activities has also addressed the feasibility of powering wearable or implantable systems. Biomedical sensors can take advantage of human-based activities as the energy source for energy scavengers. This review describes the state of the art of energy scavenging technologies for powering sensors and instrumentation of physiological variables. After a short description of the human power and the energy generation limits, the different transduction mechanisms, recent developments and challenges faced are reviewed and discussed.

Rotational energy harvester for body motion

This paper presents a micro-rotational energy harvester topology for extracting electric energy from human body motion at joint locations. This was accomplished using an inertial-based axial flux machine constructed with multiple permanent magnet poles and stacked microfabricated planar coils. Several body locations were tested while walking and running on a motor-driven treadmill. An average power of 472µW was obtained when the 2cm3 device was placed on the ankle while walking at 4mph.

Powering biomedical devices with body motion

Energy harvesting from body motion is an alternative power source that can be used to energize miniature electronic biomedical devices. This technology can make it possible to recharge batteries to reduce the frequency of or eliminate surgeries to replace depleted cells. Power availability evaluation from walking and running at several body locations and different speeds is presented. Treadmill tests were performed on 11 healthy subjects to measure the accelerations at the ankle, knee, hip, chest, wrist, elbow, upper arm, and side of the head. Power was estimated from the treadmill results since it is proportional to the acceleration magnitudes and the frequency of occurrence. Available power output from walking was found to be more than 0.5 mW/cm3 for all body locations while being more than 10 mW/cm3 for the ankle and knee. Running results were at least 10 times higher than those from walking. An axial flux miniature electric dynamo using electromagnetic induction was evaluated for power generation. The device was composed of a rotor with multiple-pole permanent magnets positioned on an annular ring having an eccentric mass, and stacked planar coils as a stator. A 2 cm3 prototype was found to generate 117 µW of power from the generator placed laterally on the ankle while walking.

Micro-rotational electromagnetic generator for high speed applications

This paper presents the development of a micro-rotational electromagnetic generator for high speed applications. The generator followed an axial flux permanent magnet design. It was constructed with a rotor composed of multiple permanent magnet poles and a stator made of stacking micro-fabricated planar coils (25 mm in diameter and 2 mm thick, not considering the casing). The rotor is composed of commercially available NdFeB permanent magnets (6 × 2 × 1 mm) while the rotor is made of 10 individual copper-clad polyimide layers (18 μm thick copper, 25 μm thick polyimide). The planar micro-coils were manufactured by photolithography with 100 μm line width copper tracks. The rotor was assembled by placing the permanent magnets in a CNC-machined slotted disk. The generator was capable of producing 3.2V and 5.8 mW of power at a rotational speed of 4,000 rpm.

Micro-Rotational Generator

Energy harvesting is a relatively new research area that extracts energy from the surroundings to power autonomous systems. This project presents a generator that harnesses the motion of high speed rotational motors for machine health monitoring. Wireless accelerometer-based sensors for detecting crack initiation on rotating shafts are typically limited by the battery finite lifetime. Miniature generators attached to rotating shafts can scavenge small amounts of energy for powering such monitoring systems. Electromagnetic induction approaches (using coils and magnets) have been widely described in literature for larger machines but few at the micro-scale. This paper investigates a multiple-pole permanent magnet design with multiple-stacks of planar coils for energy generation without using Silicon-based processing at the micro-scale. Planar coils are manufactured from 18μm thick Copper-clad on 25μm thick polyimide. The 25mm diameter coils were stacked and bonded with cyanoacrylate for a stacked thickness of 360μm. The rotor was made of a 25mm in diameter (2mm thick) CNC machined PMMA disk with 20 slots (1mm×2mm×6mm) for placing commercial NdFeB permanent magnets. The entire generator had a volume smaller than 1.5cm3 . Experimental results show that the generator is capable of producing an average voltage output of 15.5V and 727mW of power (with a matching load) at a constant rotational speed of 29,500rpm.Copyright

Energy harvesting from human walking to power biomedical devices using oscillating generation

This work summarizes the energy generation limits from walking employing a pendulum-based generation system. Self-winding wristwatches have exploited successfully this energy input technique for decades. Pendulum-based planar devices use the rotation to produce energy for inertial generators. Then the oscillations of body motion during locomotion present an opportunity to extract kinetic energy from planar generators. The sinusoidal motion of the center of gravity of the body, on the sagittal and frontal planes, and the limbs swinging are compliant with oscillating devices. Portable biomedical devices can extract energy from everyday walking to extend battery life or decrease battery size. Computer simulations suggest energy availability of 0.05-1.2 mJ on the chest, 0.5-2.5 mJ on the hip and 0.5-41 mJ on the elbow from walking.

Preliminary Cost Assessment for Offshore Wind Energy in Puerto Rico

The high cost of energy in Puerto Rico (e.g.,

Scavenging Wind Energy From Fluttering Membranes With Piezoelectric Materials

0.27/kWh in September 2014) due to its dependence on fossil fuels (i.e., 61% of electricity production) has become a direct burden on individuals and a critical barrier on economic development in the Island. To alleviate the cost of energy and reduce environmental pollution and greenhouse effects, the Puerto Rico Electric Power Authority (PREPA) is seeking to establish over 380 MW of electrical power from wind sources as part of its renewable energy portfolio. However, contrary to a wind energy study that indicates that the greatest potential for wind power extraction in Puerto Rico resides offshore, all PREPA’s wind energy projects are onshore. This investigation considers a preliminary assessment for the use of offshore wind energy in the eastern region of Puerto Rico. A theoretical model was used to calculate the wind power and levelized cost of energy (LCOE) for three typical offshore wind turbines with nominal output power of 2,300 kW, 3,000 kW, and a 3,600 kW. The results suggest that a smaller wind turbine will be more cost effective in the offshore region of Puerto Rico. As shown in the results, the LCOE could be as low as

Pendulum Generators to Power Wearable Devices from Human Motion

0.20/kWh for the 2,300 kW turbine and as high as

Piezoelectric load measurement model in knee implants

0.36/kWh for the 3,600 kW turbine. Keywords— Image Compression, ANN, HIS energy, wind, offshore, cost, Puerto Rico. Digital Object Identifier (DOI): http://dx.doi.org/10.18687/LACCEI2015.1.1.186 ISBN: 13 978-0-9822896-8-6 ISSN: 2414-6668