Maximum Harvest Research Articles

Sustainable Microalgal Harvesting Process Applying Opuntia cochenillifera: Process Parameters Optimization

Microalgae harvesting by coagulation can use coagulant agents such as alum, synthetic polymers or biocoagulants. Biocoagulants have attracted the attention of researchers because they are natural, biodegradable, and promote high microalgal harvesting efficiencies. This study aims to optimize the harvesting of Chlorella vulgaris based on the dosage of the Opuntia cochenillifera extract and the choice of eluent for biopolymer extraction. The outdoor cultivation of C. vulgaris achieved a specific growth rate of 0.455 d−1 and a maximum biomass concentration of 1.28 gDW L−1. In order to harvest the microalgal biomass, the polymer present in the mucilage of O. cochenillifera was extracted using NaOH and HCl. Coagulation and sedimentation assays were performed with different coagulant dosages: 3.5, 5.9, and 8.2 g L−1. The maximum harvesting efficiencies using the acid and alkaline extract coagulant solutions were 80.8% and 99.5%, respectively, with a dosage of 3.5 g L−1. According to the results, the C. vulgaris biomass can be harvested with the mucilage from O. cochenillifera in acid and alkaline eluents. The application of this biocoagulant constitutes a sustainable solution for microalgal harvesting.

A high-performance mini-generator with average power of 2 W for human motion energy harvesting and wearable electronics applications

The sustainability of power supply for mobile electronic devices is a problem that needs to be solved urgently. The energy from human motion is an optimal solution for this problem. As for the traditional energy harvesters based on electromagnetic, triboelectric, and piezoelectric induction, energy management is the largest challenge because of the low conversion efficiency and output power. In this paper, a high-efficiency and high-power energy harvester (EPEH) is presented based on the intersecting beam array structure. It can effectively harvest the pressure energy of humans under the soles at the states of walking, running, and weight-bearing walking. The EPEH does not impair the flexibility of humans compared with joint energy harvesters. The intersecting beam array structure is key component, which can magnify the compression distance in the vertical direction of 3.4 times in the horizontal direction, facilitating maximum energy harvesting within a limited height. On the other hand, the design of rolling friction structure can effectively reduce energy loss and improve energy conversion efficiency. The result shows that the maximum average output power can reach 2 W at 7 km/h. Because of the high output power, the energy management circuits and voltage regulator circuits can be derived and stable work, the energy harvested by the EPEH can be stored in the lithium battery (3.7 V, 50 mAh). Furthermore, the generated energy could supply mobile phones, smart watches, light bulbs, flashlights, children's anti-lost devices, and so on. Through the energy management circuit and voltage regulator circuit (1.5 V and 5 V), the energy conversion efficiency of the device can reach 65.2 % at a compression velocity of 2500 mm/min and a frequency of 1.25 Hz. It is of great significance for the practical application of wearable energy harvesting technology and has multiple application prospects.

Influence of Phosphorus and potassium on Growth and Yield of Chick Pea (Cicer arietinum L.) under Prayagraj Condition

The field experiment entitled was “Influence of Phosphorus and Potassium levels on growth and yield of chickpea” conducted during Rabi 2022 at Crop Research Farm, Department of Agronomy, SHUATS, Prayagraj (U.P). The soil of experimental plot was sandy loam in texture, nearly neutral in soil reaction (pH 7.1), low in organic carbon (0.36%), available N (171.48 kg/ha), available P (15.2 kg/ha) and available K (232.5 kg/ha). The experiment was laid out on Randomized Block Design with nine treatments each replicated thrice on the basis of one year experimentation. The treatments which are T1 : 20 kg/ha Phosphorus +10 kg/ha Potassium, T2 : 20kg/ha Phosphorus+20kg/ha Potassium, T3 :20kg/ha Phosphorus +30 kg/ha Potassium, T4 : 30 kg/ha Phosphorus +10 kg /ha Potassium, T5 : 30 kg/ha Phosphorus +20 kg /ha Potassium, T6 : 30 kg/ha Phosphorus +30 kg /ha Potassium, T7 : 40 kg/ha Phosphorus +10 kg /ha Potassium, T8 : 40 kg/ ha Phosphorus +20 kg /ha Potassium, T9 : 40 kg/ha Phosphorus +30 kg /ha Potassium are used. The results shown that the steady increase in growth attributes of Chickpea at 100 DAS viz., plant height (42.66 cm), Number of nodules per plant (6.33), Dry weight (29.17 g) were significantly higher in treatment 9 (40kg/ haphosphorus+30 kg/ha potassium). Also, treatment 9 with 40kg/ha phosphorus +30 kg/ha potassium recorded maximum number of Pods per plant (43.60), seeds per pod (1.93), Test weight (210.50 g), maximum Seed yield (2.49 t/ha), Stover yield (4.60 t/ha) and Harvest Index (34.99 %) compared to other treatments.

Effect of Biofertilizer and Drought Stress on Quantitative and Qualitative Traits in Some Winter Rapeseed (Brassica napus L.) Cultivars

To evaluation the effect of plant growth-promoting rhizobacteria under water deficit condition on quantitative and qualitative traits of winter rapeseed cultivars, an experiment was conducted at Agricultural and Natural Resources Research Center located in North Khorasan Province (2015-2017). Plant growthpromoting rhizobacteria (Nitroxin consumption and control) under water deficit condition (after 80, 130, 180 mm evaporation) on quantitative and qualitative traits of winter rapeseed cultivars (Natalie, Okapi, and Neptune) were investigated. Findings indicated that Nitroxin increased soil K, P, Fe, and Cu concentrations and decreased the soil pH and EC. Indeed, the soil N reduction and P increasing trend were related to the maximum biological yield and harvest index (HI) in the second and first years, respectively. Also, an inverse relationship was observed between No. of pods plant-1 (NPP) and No. of seeds pod-1 (NSP) among cultivars. Nitroxin was more affected on NSP and seeds weight than NPP under low and mild drought stress. The highest harvest index was observed in the mild stress in three cultivars, but, the Nitroxin consumption was ineffective. Seed yield and its components except for NPP and HI were increased by the Nitroxin consumption. The HI exhibited the inverse and direct relationship between protein and oil content, respectively. High drought stress compared to low drought stress reduced NPP (54.9%), NSP (1.3%), seed yield (52.2%), biological yield (47.5%), seed oil content (5.5%), seed oil yield (54.9%), and seed protein yield (52.7%). The highest NPP (45.5), seed yield (2740 kg ha-1 ), biological yield (7572 kg ha-1 ), and oil yield (933 kg ha-1 ) were obtained from cv. Natalie. In conclusion, Nitroxin biological fertilizer ameliorates the negative effects of drought stress under mild stressful conditions but it had not any considerable effects on reducing the effects of drought stress under severe stress conditions.

Influence Of Varietal Duration And Nitrogen Fertilization In Augmenting Micronutrient Uptake And Yield Of Rice

Lack of micronutrients in diet lead to health anomalies in human, to solve which diet-based availability can be looked upon. The goal of the current research is to ascertain how micronutrient uptake and yield of boro rice are influenced by the duration of the variety and graded doses of nitrogen fertilization. The field trial was conducted in the boro season of 2022 at Bidhan Chandra Krishi Viswavidyalaya, Gayeshpur, Nadia in a thrice replicated split plots with nitrogen fertilizer levels (0, 50, 100, 150 kg ha-1) in main plot and varieties (short duration-Satabdi, medium duration-Pratikshya and long duration-Swarna masuri) in sub-plots. At both maximum tillering and harvest stage, increase in nitrogen fertilization levels significantly increased the uptake of Zn, Cu, Fe and Mn and biomass yield significantly. However, while Fe and Mn concentrations were highest for N application at 150 kg ha-1, N application at 100 and 150 kg ha-1 statistically registered at par Zn and Cu values. Varietal influence on grain and straw yield as well as micronutrient uptake in harvest may be linked to their life cycle pattern where Partikshya considerably outperformed short duration Satabdi variety. Worst performance of Swarna Masuri variety may possibly be attributed to the inherent varietal characteristics and exposure to terminal moisture and heat stress at the months of May and June. Judicious management of nitrogen fertilizer may be a viable non- traditional approach for micronutrient nutrition in rice.

Electrochemical harvesting of Chlorella sp.: Electrolyte concentration and interelectrode distance

Two modes of electrochemical harvesting for microalgae were investigated in the current work. A sacrificial anode (aluminum) was used to study the electrocoagulation-flotation process, and a nonsacrificial anode (graphite) was used to investigate the electroflotation process. The study inspected the effect of chloride ions concentration and the interelectrode distance on the performance of the electrochemical harvesting processes. The results demonstrated that both electrodes achieved maximum harvesting efficiency with a 2 g/L NaCl concentration. Interestingly, by increasing the NaCl concentration to 5 g/L, the harvesting efficiency reduced dramatically to its lowest value. Generally, the energy consumption decreased with increasing of NaCl concentration. Moreover, the energy consumption achieved with aluminum anodes is lower than that achieved with graphite. However, by increasing the gap between the electrodes from 15 mm to 30 mm, the time required to achieve the maximum efficiency doubled, and energy consumption increased consequently.

EFFECT OF IRRIGATION FREQUENCY ON GROWTH AND YIELD OF SOYBEAN

A field experiment was conducted at the research field of HSTU, Dinajpur during November 2019 to March 2020 to find out the effect of irrigation frequency on the growth and yield of Soybean (Glycine max L.) cv. BARI Soybean-6. The experiment was carried out with a RCBD with four replications of irrigation treatments viz, I0= no irrigation (control), I1= one time at 20 days after sowing (DAS), I2= two times (20 and 40 DAS), I3= three times (20, 40, and 60 DAS). At 105 DAS the highest plant height (52.53 cm) was found from I2 treatment and the shortest plant (45.82 cm) from I0 treatment. The highest (5.91) leaf area index was obtained from the treatment of three irrigation (I3) at 90 DAS and the lowest (5.1) leaf area index from the control (I0). At the 90 DAS highest nodule number (9.208) and the lowest nodule number was (6.459) recorded from I3 and I0, respectively. The highest (90.09 g) fresh weight was obtained from the treatment I2 at 90 DAS and the lowest (65.64 g) was recorded in I0. I3 produced the highest amount of dry matter of (29.50 g) and the lowest amount of dry matter production at harvest (20.67 g) in I0 treatment. The highest seed yield was observed from I2 (1.638 t ha-1 ) which was statistically similar with I3 whereas, the lowest obtained from I0 (1.075 t ha-1 ). The highest small stover yield was obtained from I3 (1.759 t ha-1 ) which is statistically similar to I2 (1.754 t ha-1 ) whereas the lowest was observed from I0 (1.540 t ha-1 ) which was statistically similar to I1 (1.566 t ha-1 ). The highest biological yield was found from I2 (3.425 t ha-1 ) which is statistically similar to I3 and the lowest was obtained from I0 (2.56 t ha-1 ). The maximum harvest index was found from I2 (47.71 %) and the minimum was obtained from I0 (40.81 %). I2 treatment showed more significant results than the other treatment I0, I1 and I3. So, two times irrigation showed significant effect showed the highest yield of 1.638 t ha-1.

Design of Piezoelectric Energy Harvesting Structures Based on Proof Mass Analysis-Simulation and Experimental Study

In this work, two types of piezoelectric structures A and B are designed for harvesting maximum amount of energy from motor vibrations. The analysis is conducted under various load conditions with the placement of two different shapes of proof mass (square and rectangular) on the piezoelectric energy harvester. An experimental study is conducted for harvesting energy from motor vibrations using two piezoelectric structures A and B, in which, structure B with the placement of square-proof mass generates maximum power, which is efficient for powering low-power electronic applications.

Response of rainfed Indian mustard to different tillage practices and mulching

A field experiment was conducted during the rabi season of 2019 at College of Agriculture, Central Agricultural University, Imphal, Manipur. The experiment included the combination of two soil tillage systems viz., Conventional Tillage (L1) and Minimum Tillage (L2) and four different mulching materials viz., No mulch (M1); Rice straw mulch (M2); Polythene mulch (M3) and Tree leave mulch (M4). The Experiment was laid out in a split-plot design with different levels of tillage (main plot), and mulching materials (subplot) and each treatment were replicated thrice. The growth and yield of Indian mustard were influenced by different tillage practices and mulching. Maximum plant height (165.33 cm.), number of siliquae per plant (197) and seed yield (1790 kg/ha ) and oil yield (692 kg/ha) were recorded in a combination of (L1M3) which received in Conventional tillage + Polythene mulch and minimum seed yield was recorded in a combination of (L2M1) 1441 kg/ha which received in Minimum tillage + No mulch. Maximum harvest index was recorded in a combination of (L1M2) 27.50% which was received in Conventional tillage +Rice straw mulch and minimum harvest index was recorded in a combination of (L1M4) 24.13% which was received in Conventional tillage + Tree leaves to mulch. The highest benefit-cost ratio (0.72) was recorded in Minimum tillage + Rice straw mulch because there was less input cost for tillage or ploughing activities and mulching material cost. The highest energy use efficiency, and energy productivity but lowest specific energy was observed in Minimum tillage with No mulch and energy use efficiency, and energy productivity but highest specific energy was observed in Minimum tillage with Rice straw mulch.

Enhancing energy harvesting efficiency of form stable phase change materials by decreasing surface roughness

A high thermoelectric energy harvesting efficiency is vital to increase the collected output electrical energy. In this work, we fabricated cross-linked graphene/cysteamine aerogel (GCA) to reduce the volume shrinkage, and a phase change material (PCM) composite with relatively low surface roughness was obtained. The flat surface of PCM composite is suitable for connecting with the PN cell efficiently and promoting the thermal transportation during heating and cooling processes. Polyethylene glycol (PEG) and 1-tetradecanol (1-TD) two different PCM were utilized as working materials for PCM composites. The surface roughness of GCA supported PEG and 1-TD composite were 0.0286 and 0.0224, respectively. The heat transfer coefficient (HTC) can be affected by the surface roughness. It was found that the PEG/GCA and 1-TD/GCA composites had a great thermal-to-electrical conversion during the phase transition process. The maximum energy harvesting efficiency was 59.13 % and the numerical simulation was conducted to process the surface images and temperature profiles of PCM composites.

Wind Energy Harvesting and Conversion Systems: A Technical Review

Wind energy harvesting for electricity generation has a significant role in overcoming the challenges involved with climate change and the energy resource implications involved with population growth and political unrest. Indeed, there has been significant growth in wind energy capacity worldwide with turbine capacity growing significantly over the last two decades. This confidence is echoed in the wind power market and global wind energy statistics. However, wind energy capture and utilisation has always been challenging. Appreciation of the wind as a resource makes for difficulties in modelling and the sensitivities of how the wind resource maps to energy production results in an energy harvesting opportunity. An opportunity that is dependent on different system parameters, namely the wind as a resource, technology and system synergies in realizing an optimal wind energy harvest. This paper presents a thorough review of the state of the art concerning the realization of optimal wind energy harvesting and utilisation. The wind energy resource and, more specifically, the influence of wind speed and wind energy resource forecasting are considered in conjunction with technological considerations and how system optimization can realise more effective operational efficiencies. Moreover, non-technological issues affecting wind energy harvesting are also considered. These include standards and regulatory implications with higher levels of grid integration and higher system non-synchronous penetration (SNSP). The review concludes that hybrid forecasting techniques enable a more accurate and predictable resource appreciation and that a hybrid power system that employs a multi-objective optimization approach is most suitable in achieving an optimal configuration for maximum energy harvesting.

Generalized Analysis Method for Magnetic Energy Harvesters

Large-scale deployment of low-power sensing and computing units calls for unique power management solutions to overcome the inconvenience, costs, and waste problems associated with batteries. Energy harvesting offers an exciting solution to the battery problem, enabling circuits that can power themselves on-site from available ambient energy. Magnetic energy harvesters (MEHs), configured as current transformers, extract energy from the magnetic fields surrounding current-carrying power lines. As maximum power harvest occurs when a magnetic core is on the verge of saturation or saturated to some degree, modeling of magnetic energy harvesters is inherently difficult and nonlinear. This article proposes generalized analytical methods for modeling magnetic energy harvester behavior and validates these methods along with existing circuit model techniques. Intuition for core saturation behavior is presented and agreement with existing models is discussed. The analysis is motivated by addressing the feasibility of a split core magnetic energy harvester to power a microcontroller unit, and the models are experimentally validated for multiple harvester cores.

A 5.8 GHz high-gain flexible receiving antenna for wireless power transmission

In this paper, a 5.8 GHz, high-gain flexible receiving antenna (FRA) is proposed, which can be used for wireless power transmission (WPT) systems. The FRA is designed by an iterative process and is etched on Kapton, with a coplanar waveguide (CPW) feed. In order to improve the gain of the FRA, an air-gap and a flexible reflector are loaded, and the gain is improved from 2.79 to 9.51 dBi at 5.8 GHz. To validate the stability of FRA, the fabricated prototype uses three configurations of 80, 70, and 50 mm. The impedance matching keeps well, and the gain of the FRA can sustain above 8.96 dBi. In addition, a miniaturized WPT system was built. The measured results show that the proposed FRA has a maximum harvesting efficiency (HE) of 71.3%, and it can maintain the maximum HE above 63% in bending conditions. The lightweight, high-gain, and high HE in various cases prove the huge potential of the FRA in WPT applications.

Effect of farmyard manure, elemental sulphur and EDTA on growth and phytoextraction of cadmium by spider plants (Chlorophytum comosum L.) under Cd stress

Cadmium (Cd) contamination is considered as a widespread concern at global scale which is serious threats to human health. Phytoremediation is an eco-friendly approach which can remove or immobilize Cd from the soil. Different organic and inorganic amendments can potentially enhance Cd phytoremediation efficiency but the comparison of farmyard manure (FM), elemental sulphur (S) and ethylenediaminetetraacetic acid (EDTA) for Cd phytoremediation through spider plants (Chlorophytum comosum L.) remained unanswered. The present study evaluated the efficiency of S (0.1 and 0.2%), EDTA (0.1 and 0.2%, represented as EDTA-0.1 and EDTA-0.2) and FM (0.5 and 1%, represented as FM-0.5 and FM-1) for remediation of Cd contaminated soils (50 and 100 mg kg-1, represented as Cd-50 and Cd-100) through spider plants. Results depicted that the highest shoots and roots dry biomass was found in FM treated plants followed by S, EDTA and control except in EDTA-0.2 treatment in which the lowest values of these parameters were observed. Application of FM-1 significantly increased the shoot dry weight (120%), root dry weight (99%), as well as photosynthetic attributes in Cd-50 as compared to control. Application of EDTA-0.2 increased the bioavailable fraction of Cd than control and the maximum increase was observed in Cd-100. The highest Cd concentrations in shoot and roots were found in EDTA treated plants followed by S, control and FM irrespective of Cd and amendment levels. Maximum Cd in roots (109%) and shoots (156%) was recorded in plants grown in Cd-100 with EDTA-0.2 than control. The maximum bioaccumulation factor, translocation index, harvest index and root to shoot translocation were observed with EDTA than control and other treatments. EDTA along with spider plants may enhance the uptake of Cd but lower biomass production in the highest dose of EDTA may questioned the efficiency of EDTA.

A review of energy harvesting from regenerative shock absorber from 2000 to 2021: advancements, emerging applications, and technical challenges.

In the automotive and transportation sectors, technological advancements and innovations aim to reduce fuel consumption and CO2 emissions of vehicles. In vehicles, a significant portion of fuel energy is wasted in heat, vibrations, and frictional losses. The vibration energy from vehicle suspension systems is always wasted in heat and can be utilized for useful purposes. Many researchers have designed various regenerative shock absorbers (RSA) to transform vibration energy into electrical energy that can charge electric vehicles' batteries and power low-wattage devices. The present work focuses on an in-depth summary of rotary, hydraulic, and linear electromagnetic RSA. Also, the applications of regenerated energy and technical challenges are discussed. In RSA, the maximum energy harvesting, and ride comfort of the vehicle cannot be achieved simultaneously. The weight of RSA may increase due to the integration of some additional components compared with conventional shock absorbers. It is necessary to examine the impact of weight on the vehicle's road handling and ride comfort. The hydraulic RSAs have low energy harvesting efficiency, so they are not suitable for lightweight vehicles despite their higher energy harvestability than rotary and linear RSAs. The bibliometric analysis is conducted using the visualization of similarities (VOS) viewer to visualize the contributing authors and countries and specify the research themes. The articles are collected from the Web of Science using keywords related to energy harvesting from 2000 to 2021. Authors from China are more productive than others, with the highest number of publications related to the energy-harvesting from RSAs in 2019.

Co-cultivation of microalgae-cyanobacterium under various nitrogen and phosphorus regimes to concurrently improve biomass, lipid accumulation and easy harvesting

Due to due to high-cost harvesting method, low biomass productivity (BP), and lipid yield (LY), commercialization of microalgae biomass is still impeded. Some researchers discovered that the combined effects of low nitrogen (N) and high phosphorus (P) resulted to an increase in biomass and lipid production. However, the choice of a balanced N:P ratio is still ambiguous between microalgal species and is up for debate. Here, we set various ranges of N:P ratios from 2:1–44.11:1 with the addition of glucose in the BG 11 medium to examine its influence on the growth of microalgae. The investigation was performed by subjecting a novel strain, Scenedesmus sp. DDVG I to these various mediums under heterotrophic and mixotrophic modes. The N:P of 100:50 or N-deficient P-over excessive (Ndef Poexcs) condition under mixotrophic mode had the highest growth rate of 0.15 d−1 ± 0.01, with a maximum BP and LY of 41.1 ± 0.5 mg/L. d and 39.1 ± 1.2 % dry cell weight (DCW), respectively. Further, in attempting to facilitate the harvesting step, we co-cultured Scenedesmus sp. with Limnothrix sp. DDVG II mixotrophically under inoculum ratio of 1:1, 1:2, 2:1 in the Ndef Poexcs condition. The co-culture 1:1 system achieved the maximum biomass harvesting efficiency of 99.9± 0.5 % with an increase in BP and LY up to 42.0 ± 0.9 mg/L. d and 40.2 ± 1.0 % DCW, respectively. The fatty acid methyl ester compositions of co-culture 1:1 was rich in C18:2 (36.05 %), C16:0 (32.25 %), C18:1 (16.86 %), and C18:0 (7.68 %). The biodiesel derived from the co-culture 1:1 also complied with standard specifications, making it appropriate for the production of biodiesel. The overall findings demonstrated a unique co-culture approach toward easy harvesting while concurrently maximizing biomass and lipid yield when grown in a balanced N:P ratio of 100:50. The techno-economic analysis of the system, biodiesel cost, and its implementation toward biorefinery approach can be envisaged in the future study.

Asymmetric tristable energy harvester with a compressible and rotatable magnet-spring oscillating system for energy harvesting enhancement

This paper proposes an asymmetric tristable energy harvester with a compressible and rotatable magnet-spring oscillating system to enhance the energy harvesting performance. The linear compressible and rotatable magnet-spring oscillating system is composed of two external magnets, a metal block and two parallel springs. The two external magnets are symmetrically located on the metal block and fixed to the base through the two parallel springs. Due to different compression of the two springs under variable magnetic force, the two external magnets can move along the spring's compression direction and rotate around the center of the metal block, thus to generate tunable and asymmetric potential function. The general governing equations and asymmetric potential function of the proposed harvester are established with Hamilton principle and point dipole method, respectively. The effects of system parameters on the nonlinear dynamic performances of the proposed harvester are numerically investigated. Experiments are carried out to validate the simulations. The results demonstrate that moderate spring stiffness can not only reduce the potential energy barrier and the threshold of snap-through, but also broaden the bandwidth of interwell motion, as well as enhance the energy harvesting efficiency. When the spring stiffness k = 900 N/m, the threshold value of snap-through of the TEH-A is 8 m/s2, the bandwidth of inter-well motion is 2.0∼4.5 Hz, and the maximum harvesting voltage and power reach 6.8 V and 4.6 × 10−5 W, respectively. These values are far better than the tristable energy harvester with symmetric potential wells, whose corresponding values are 3.8∼4.2 Hz, 9.8 m/s2, 0.81 V and 6.6 × 10−7 W, respectively.

Target driven design of electromagnetic metamaterial for dual-band Wi-Fi energy harvester

With the development of Internet of things (IoT), there have a large amount of interconnected devices communicates with each other through electromagnetic (EM) waves sent by Wi-Fi router. It is promising to harvest Wi-Fi energy realizing wireless power transmission for sensors or microelectronic devices. However, the energy is hardly to be harvested effectively due to the complexity and disorder of EM waves. To address such issue, we propose an EM metamaterial based on parametric equation as dual-band Wi-Fi energy harvester operating at 2.45 GHz and 5.8 GHz. By adjusting these equation parameters, the prototype can achieve almost an arbitrary shape, avoiding the problem of local optimal solutions. Through the co-simulation of MATLAB and CST Studio Suite software, we design a genetic algorithm (GA) to optimize the proposed structure so that it can harvest energy at Wi-Fi frequency bands. The optimized metamaterial exhibits electric dipole resonance and magnetic dipole resonance simultaneously at 2.45 GHz and 5.8 GHz, and the maximum harvesting efficiency is 96.9% and 95% at normal incidence, respectively. In particular, the metamaterial has the characteristics of polarization insensitive, ultra-wide band and wide-angle harvesting. It is expected to integrate with small electronic devices to realize the function of remote energy conversion, self-powered, and maintenance-free in the era of advanced wireless networks.

The Phytoremediation using Water Hyacinth and Water Lettuce: Correlation between Sugar Content, Biomass Growth Rate, and Nutrients

Degradation of water quality due to the presence of pollutants in water is an emerging issue in many countries, including Malaysia. Phytoremediation is one of the environmentally friendly, cost-effective conventional technologies that are still used in modern times. However, the selection of plant species is the most important aspect for the application of phytoremediation in wastewater treatment. Nevertheless, there are species of floating aquatic macrophytes that are capable of coping with various pollutants present in wastewater. Among the various floating aquatic macrophyte species, water hyacinth (WH) and water lettuce (WL) have been described as effective phytoremediators in reducing water pollution through bioaccumulation in their body tissues. Hence, WH and WL were chosen in this study as it is easily found, propagated, and cultivated. This paper aims to determine the biosorption capacity of these species in eliminating various pollutants present in wastewater as well as to define the optimum harvesting time for each species. Although these floating aquatic macrophytes are considered the most problematic plants due to their uncontrollable growth in water bodies worldwide, their ability to remove pollutants from wastewater has created a sustainable approach for their use in phytoremediation. In this sense, the use of phytoremediation by implementing the invasive floating aquatic macrophytes can certainly support the sustainable management of wastewater treatment in the future. Based on the results, it was found that WH efficiently removed higher PO43-, NO3- and NO2- concentrations compared to WL from the wastewater. Both WH and WL showed the same trend of correlation between the growth rate and sugar content, where the sugar content increased when the plants reached the highest growth rate. The maximum nutrient uptake occurred in 14-17 days, proving that nutrient availability is critical for plant growth. This study concludes that the sugar content of WH and WL are increased with the biomass growth rate, and both plants species are competent in eradicating the nutrient pollution in wastewater. On top of that, this study infers that the maximum harvesting period for WH biomass is on day 18, while WL biomass is on day 21; based on the highest sugar content and biomass weight of each species.

Nano magnetite assisted flocculation for efficient harvesting of lutein and lipid producing microalgae biomass

For commercial scale algal biorefining, harvesting cost is a major bottleneck. Thus, a cost-effective, less-energy intensive, and efficient harvesting method is being investigated. Among several harvesting methods, magnetic flocculation offers the benefits of modest operation, energy savings and quick separation. This study aims to develop novel magnetite-(Fe3O4) nanoparticles (MNPs) of 20 nm average size and their high reusability potential to reduce the harvesting cost of microalgae biomass. The MNPs were synthesized and characterized using FTIR, Zeta analyzer, and SEM before performing on Chlorella sorokiniana Kh12 and Tu5. For maximum harvesting efficiency >99%, the optimal culture pH, MNPs concentration, and agitation speed were 3, 200 mg/L, and 450 rpm, respectively. Subsequently, MNPs were recovered via alkaline treatment and reused up to 5 cycles as they retained their reactivity and harvesting efficiency. The studied MNPs-based harvesting method could be adopted at a commercial scale for cost-effective algae biorefinery in the future.