• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2014.10a
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• pp.561-564
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• 2014

In this paper a photovoltaic energy harvesting charger with battery management circuit is proposed. The proposed circuit harvests maximum power from a solar cell by employing MPPT(Maximum Power Point Tracking) control and charges an external capacitor battery with the harvested energy. The charging state of the battery is controlled according to the signals from the battery management circuit. The proposed circuit is designed in a 0.35um CMOS process technology and its functionality has been verified through extensive simulations. The maximum efficiency of the designed entire system is 84.8%, and the chip area including pads is $1350um{\times}1200um$.

• Environmental Engineering Research
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• v.18 no.2
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• pp.95-101
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• 2013

Alternative sources of water are sought in some water stressed communities in the study area. The study focuses on the Aguata-Awka area of southeastern Nigeria. Aquifers occur at great depths, and surface waters may be far from homesteads. The scarcity of water has necessitated the people to adopt various local technologies for harvesting rainfall. The local technology includes collecting rainwater from roofs and channeling the water into large underground tanks, shallow wells and surface reservoirs. Large concrete tanks of $6m{\times}6m{\times}4m$ dimensions are often built underground and can store $144m^3$ of water. Surface reservoirs built on 4 m concrete pillar supports having dimensions of $10m{\times}10m{\times}4m$ and have a storage capacity of $400m^3$. Water samples were collected at 3 different locations of Agulu, Ekwulobia, and Awka and were analyzed for their physical, chemical, and bacteriological parameters. Results indicate a range of values for pH, 5.9 to 7.1; turbidity, 0.9 to 2.7; total dissolved solids, 80 to 170 mg/L; total hardness, 4.5 to 6.4 mg/L; magnesium, 1.2 to 1.4 mg/L; bicarbonate, 19.4 to 83.6 mg/L; and sulfate, 3.6 to 6.4 mg/L. Bacteriological analysis results were negative for fecal and total coliform counts. All parameters, with the exception of pH where aluminum and galvanized iron roofs are used for collection, fall within the recommended guidelines for drinking water quality of the World Health Organization, and the Standard Organization of Nigeria, new Nigerian standards for drinking water quality. Magnesium is above the maximum permitted level for consumer acceptability of the Nigerian standards for drinking water quality. The water can be classified as fresh moderately hard and soft. The water can be described as a calcium and bicarbonate type.

• Journal of Sensor Science and Technology
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• v.17 no.4
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• pp.267-272
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• 2008

Energy harvesting from the vibration through the piezoelectric effect has been studied for powering the small wireless sensor nodes. As piezoelectric uni-morph cantilever structure can transfer low vibration to large displacement, this structure was commonly deployed to harvest electric energy from vibrations. Through our previous results, when stress was applied on the cantilever, stress was concentrated on the certain point of the ceramic of the cantilever. In this study, for miniaturing the energy harvester, we investigated how the size of ceramics and the stress distribution in ceramic affects energy harvester characteristics. Even though the area of ceramic was 28.6 % decreased from $10{\times}35{\times}0.5mm^3$ to $10{\times}25{\times}0.5mm^3$, both samples showed almost same maximum power of 0.45 mW and the electro-mechanical coupling factor ($K_{31}$) of 14 % as well. This result indicated that should be preferentially considered to generate high power with small size energy harvester.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.64-71
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• 2006

A target of this paper is to study on the usefulness of the adaptive piezoelectric energy harvesting device as a wireless electrical power supply when it is driven by mechanical vibrations of low frequency. For this purpose, an adaptive control technique and a step-down converter are used. A THUNDER series a piezoelectric material (TH7-R), which has been developed by a NASA engineer is selected for this study. In order to provide a mechanical energy to the piezoelectric material, a mechanical motion vibrator is designed. The adaptive controller is implemented using a dSPACE DS1104 controller board. The do-dc converter with an adaptive control technique harvests energy at over five times the rate of direct charging without a converter.

• Journal of Biosystems Engineering
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• v.14 no.1
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• pp.16-23
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• 1989

An oscillating potato digger for power tillers was designed and constructed to evaluate the effects of vibration on potato digging. Changing the levels of amplitude, frequency, and travel speed, 16 combinations of such parameters were tested in the potato field. The measured variables were harvesting loss and damage, and storing loss of the mechanically harvested potatoes. It was observed that the operation of the digger blade was good with amplitude of 12 mm, frequency of 9.67 Hz, and travel speed of 0.87 km/hr. Under these conditions the harvesting loss and damage were 3.18 % and 0.67 % that are very lower than those of 6.83 % and 9.83 % of traditional harvesting method. The operating efficiency of the experimental digger under optimum operating conditions was about 552 $m^2$ per hour which was about 20 times higher than 27.2 $m^2$ per man per hour of traditional harvest.

• Journal of Communications and Networks
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• v.14 no.2
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• pp.140-150
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• 2012

In this paper, we investigate the optimal packet scheduling problem in a two-user multiple access communication system, where the transmitters are able to harvest energy from the nature. Under a deterministic system setting, we assume that the energy harvesting times and harvested energy amounts are known before the transmission starts. For the packet arrivals, we assume that packets have already arrived and are ready to be transmitted at the transmitter before the transmission starts. Our goal is to minimize the time by which all packets from both users are delivered to the destination through controlling the transmission powers and transmission rates of both users. We first develop a generalized iterative backward waterfilling algorithm to characterize the maximum departure region of the transmitters for any given deadline T. Then, based on the sequence of maximum departure regions at energy arrival instants, we decompose the transmission completion time minimization problem into convex optimization problems and solve the overall problem efficiently.

• Journal of The Korean Society of Grassland and Forage Science
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• v.36 no.4
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• pp.376-380
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• 2016

This experiment was carried out to investigate the effect of harvesting time of Italian ryegrass (Lolium multiflorum Lam; IRG) in spring on dry matter (DM) yield. IRG cultivars 'Kowinearly' and 'Greenfarm' were seeded at 50 kg/ha and grown on rice paddy fields. There was no difference in growth characteristics between both varieties before winter. However, cold tolerance of Kowinearly was higher than that of Greenfarm, as demonstrated by post-wintering growth characteristics. The heading date of both varieties was affected by the spring weather. The IRG was harvested three times at 5-day intervals beginning from 9 May. The DM yield of Greenfarm was 6,306; 7,335; and 8,109 kg/ha, and that of Kowinearly was 7,498; 9,196; and 10,449 kg/ha at the three consecutive harvests. The delay of the harvesting time for 5 and 10 days increased the DM yield of Greenfarm by 16% and 29% and that of Kowinearly by 23% and 39%, respectively, compared to the yield at first harvest (p < 0.05). Therefore, IRG harvest later than early to mid-May is expected to increase productivity. The feed values of Greenfarm were: 12.2% of crude protein (CP), 34.5% of acid detergent fiber (ADF), 57.7% of neutral detergent fiber (NDF), 61.6% of total digestible nutrients (TDN), and 72.3% of in vitro DM digestibility (IVDMD). For Kowinearly, these values were 16.4% of CP, 30.4% of ADF, 52.7% of NDF, 64.9% of TDN and 79.0% of IVDMD.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.11
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• pp.2627-2635
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• 2013

In this paper micro-scale solar energy harvesting system with a new MPPT control are proposed. In conventional solar energy harvesting systems, continuous perturbation techniques of the clock frequency or duty cycle of a power converter have been used to implement MPPT(Maximum Power Point Tracking) control. In this paper, we propose a new MPPT technique to control the duty cycle of a power switch powering a power converter. The proposed circuit is designed in $0.35{\mu}m$ CMOS process, and the designed chip area including pads is $770{\mu}m{\times}800{\mu}m$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.255-258
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• 2012

In this paper, with a thermoelectric device using the seebeck effect which generates electromotive force by temperature difference generates electric energy an energy harvesting circuit using MPPT(Maximun Power Point Traking) control is designed. After periodically sampling the open voltage of the thermoelectric device, the 1/2 voltage of open voltage which in a maximum power point is maintained through MPPT control circuit and harvested energy from thermoelectric device is delivered to load through a switch. The proposed thermal energy harvesting circuit is designed with $0.35{\mu}m$ CMOS process and the chip area excluding pads is $1168.7{\mu}m{\times}541.3{\mu}m$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.533-536
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• 2016

This paper describes a vibrational energy harvesting circuit with MPPT control. A high-performance AC-DC converter of which the efficiency is improved by using body-bias technique and bulk-driven technique is proposed and applied for the vibrational energy harvesting circuit design. MPPT (Maximum Power Point Tracking) control function is implemented using the linear relationship between the open-circuit voltage of a vibrational device and its MPP voltage. The designed MPPT control circuit traces the maximum power point by periodically sampling the open circuit voltage of a vibrational device, makes the reference voltages using sampled voltage and delivers the maximum available power to load. The proposed circuit is designed with a $0.35{\mu}m$ CMOS process, and the chip area is $1.21mm{\times}0.98mm$.