Mechanical Engineering

This paper reports the design, fabrication, and testing of a permanent-magnet energy harvester generator for body motion. The described generator was capable to extract up to 117µW of power from walking, employing a non-resonant rotational mechanism. The planar generator proposed is composed of a rotor having multiple NdFeB permanent magnet pole-pairs with an eccentric proof mass. The stator has a multi-stacked gearshaped planar coil. A change on the magnetic flux induces a voltage in the coil when the rotor moves as a result of body movement. A 2cm 3 prototype was tested on several body locations while walking.

The effect of air bubbles in 70 % isopropyl alcohol with magnetic nanoparticles (Fe 3 O 4) in both the absence and presence of a magnetic field was studied. In this study, the magnetic nanofluids in isopropyl alcohol was found to counteract the buoyancy force of bubbles in the absence of the magnetic field. The air bubbles were generated by an air pump, that allow to study the behavior of the bubble rise with magnetic nanofluids in presence of a magnetic field. The air bubbles stay suspended much longer in presence of a magnetic field than in absence of a magnetic field. In presence of a magnetic field, the average size of the departing bubbles decreased and the bubble frequency increased by 19 percent compared with the bubble flow with nanofluids in the absence of a magnetic field. Additionally, it was observed that the magnetic field affected the air bubble velocity in the bulk fluid.

Vibration energy harvesting using piezoelectric generators have been preferred due to the higher power output. Such low power generated can be successfully used to power wireless sensors nodes while extracting energy from environmental sources. Machine vibrations have been typically chosen for this endeavor, but recently fluid flow energy harvesting induced are being investigated. This research focuses on study of the self-sustained oscillations (panel flutter) for energy generation with the use of flexible piezoelectric materials (MFC) with a thickness of 9 µm attached to a thin Mylar. Wind speeds a low as 7 mph can produce an open-circuit of 0.85 volt.

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 $0.20/kWh for the 2,300 kW turbine and as high as $0.36/kWh for the 3,600 kW turbine.

Energy harvesting is a new promising research area for portable electronics. Portable electronic devices have been typically limited by the finite lifetime and size of the internal batteries. This has been a constant conflict and tradeoff between battery size and device capabilities. For instance, cardiac pacemaker lifespan is mostly limited by battery size, which occupies at least half the available volume. Energy harvesting or energy scavenging is an alternative that extracts energy from the surroundings in order to operate. Energy harvesting is also an interesting approach when battery replacement is not possible or is too costly, such as deployment of sensors in remote areas for surveillance or environmental monitoring. One of the best known examples is the self-winding wristwatch that started from being completely mechanical and operated by the wearer’s daily motion, to be nowadays a miniaturized electrical generator. Energy harvesting extracts energy from the surrounding by ha...

This work explore the possibility to use the thermoelectric technology to create device to effectively cold or heat the skin of the people in contact with a car seat; in addition this device must to be adaptable to the factory made seat. Initially one thermoelectric device was used with two computers heat sinks and fans. The results shows comfortable temperature for the heating case, but still a high temperature for the cooling case. The use of optimal heat sinks and the improvement of the contact resistances are being explore.

The Puerto Rico CubeSat is a "3U" configuration, meaning that it is 10 × 10 × 30 cm (about 4 by 4 by 12 inches) in size. Active attitude control will be used to align the long (3U) axis along the orbital path, and the satellite will rotate along the 3U axis to assist in thermal management. The PR CubeSat will orbit at about 400 km (240 miles) altitude within the earth's ionosphere, which consists of a thin neutral atmosphere together with a large percentage of positive ions and negative electrons. The satellite will carry two scientific instruments, CARLO (Charge Analyzer Responsive to Local Oscillation) and GimmeRF (Gimme Radio Frequency). CARLO will measure charged ion turbulence from 0 to 10 kHz, which affects radio propagation in the 0 to 30 MHz radio band measured by GimmeRF.

This work analyzes the energy generation capability from human walking using pendulum-based generators. Energy harvesting is the process to extract energy from the surroundings to power small portable electronics. Literature for energy harvesters is mostly for linear devices whereas body motion has rotational components as well. The periodic swinging of the limbs is more suited for oscillating generators based on pendulum geometries, such as self-winding wristwatches. Wearable devices can benefit of harnessing energy from everyday activities, such as walking, to reduce battery size or the need for frequent battery recharges. This study discusses the energy availability of using inertial passive generators on body locations while walking. It is estimated that a miniature planar generator using an oscillating pendulum can scavenge from 0.1 mJ to over 20 mJ of energy from walking.

The almost total elimination of sediment supply from the Colorado River has produced a condition of sediment starvation in the entire northern Gulf of California (NGC). Textural and mineralogical analyses of 114 surface sediment samples collected in the area show that this situation has promoted alternate sediment sources to become more important in supplying and controlling the compositional characteristics of the sediments in the region. By applying multivariate data analyses using Q/F ratios as well as heavy mineral and clay mineral content of samples, four sedimentary provinces are identi®ed: Colorado River Delta Province (CRDP), Concepcio Ân River Province (CcRP), Transitional Province (TP) and Baja-Sonora Province (BSP). The CRDP dominates the regional distribution of sediments, being mainly con®ned to the western side of the NGC. The sediment source for this province is the deltaic structure of the Colorado River. Sediment recycling through resuspension and reworking of the Colorado delta and the shallow shelf of the Upper Gulf of California (UGC) is an important agent for supplying sediments to the NGC. The CcRP re¯ects the mineralogical association of Concepcio Ân River, while the TP contains a mineral association that is similar to CRDP and CcRP, but with intermediate values to these provinces. This situation suggests that TP is a mixing zone between these two neighboring provinces. The higher abundance of zircon and garnet in TP also suggests a clear contribution of sediment sources from the Sonora desert in NW Mexico. Clay mineral composition of these sediments indicates a greater abundance of smectite and chlorite relative to previous studies, being mainly derived from eolian dust carried from the desert region of NW-Mexico and SW-USA. Although eolian supply of ®ne-grained sediments is important in the NGC, Colorado River delta sediments are still the largest single source of sediments to the region. Eolian supply of ®negrained sediments is, however, more dominant in the southern half, and along the eastern margin of the NGC. The dispersion of sediments in the NGC is consistently cross-basinal with a series of transport cells that follow a cyclonic circulation. Four depocenters were identi®ed, located all on the western side of the NGC, and mainly associated to the deep basins. The major effect that damming of the Colorado River has had on the sedimentology of the area is that sediment dispersion is now cross-basinal instead of long-basinal. This situation indicates that sediment dispersion at present is mainly controlled by oceanic forcing instead of¯uvial processes, as it was in the past.