An Analytical Energy Harvester Model for Interdigitated Ring Electrode on Circular Elastic Membrane

Energy harvesters are devices that accumulate ambient vibrational energy from the environment, and for the time being, variable capacitance is the most widely used mechanism. Various designs were proposed to increase the power of such devices, and in particular, the interdigitated electrode (IDE) pattern is the mainstream. Nevertheless, most IDE designs focus merely on the parallel-type vibrations of electrodes. In this study, the performance of a novel harvester, which combined circular membrane and interdigitated ring electrodes (IRE), was investigated. This design allows the device to collect energy from the rotational structure motions of electrodes through the vibrating membrane. Besides, the circular structure provides a dense capacitive arrangement that is higher than that of the arrangement obtained using regular rectangular chips. The IRE diagram is composed of many capacitive rings, each of which harvests vibrated energy simultaneously. Three gaps (1, 10, and 100 μm) of the ring are investigated for the first four vibrational modes of the membrane to understand the effect of energy output. It is found that the energy outputs are approximately the same for the three gaps; however, rings with a wider gap are easier to manufacture in MEMS.

СТАН ТА ТЕНДЕНЦІЇ РОЗВИТКУ СИСТЕМИ ЕНЕРГОЗАБЕЗПЕЧЕННЯ В УКРАЇНІ

The article discusses contemporary issues of ensuring energy security in Ukraine. A brief overview on the modern energy system which comprises power plants of different types, electrical and thermal networks operating in the manufacturing sector, in transmission and distribution of electrical and thermal energy. The study considers the following types of power plants in the energy system of Ukraine: nuclear, thermal, hydroelectric and hydropower stations as well as power plants working with alternative (renewable) energy sources. It is argued that the ratio of energy sources and the energy system balance is the core basis to provide the national energy security and maintain stable power supply subject to different external environment factors. The findings have revealed the dominance of coal and natural gas production in the overall energy balance of Ukraine. However, the study of import and export trends demonstrates the prevalence of energy imports, in particular coal, oil and gas. It is observed that currently, alternative energy sources are at the infant development stage. The study of alternative energy supply in Ukraine shows that over 2018–2020 the capacity of such power plants increased by 7%, in particular, the capacity of wind stations grew by 2.3 times and solar – by 4.3 times, thus exhibiting respective change in energy output. It is also observed that during the period under consideration, the renewable energy output dropped by 17.1% while wind power production increased by 2.8 times and solar – by 5.2 times, respectively. According to the results, over 2018–2020 the capacity of wind power plants increased from 0.9% to 2.0% of the total domestic output, and solar – from 2.3% to 9.4%; as to production, the share of energy generated by wind power increased from 0.8% to 2.4%, and solar – from 0.7% to 4.1%. Given the current trend of increasing energy output generated from alternative sources, there is reason to tap a growing interest in the activities of companies offering power generating equipment in the Ukrainian market. A study on the capacity needs has revealed that the most popular among consumers of autonomous power supply systems, about 70% of total sales refer to low and medium power generators in the range of 8–550 kW. The conclusions resume that the key driver in boosting the alternative energy supply system is the relevant legal framework that encourages further alternative energy supply market development and, accordingly, the market of power generating equipment in Ukraine characterized by a strong upward growth trend.

A Novel Approach on the Advancement in Polymer Phase Change Material in Solar Energy

A wide interest has been shown in the application of solar energy in recent times. This motivated the researchers to make a development in the approach of solar energy, but there are different technologies like MPPT, CPG, and grid mode that have been used to maintain a constant temperature. Among these, phase change material has been used to regulate the temperature in the system. Solar energy is becoming an essential approach for increasing the efficiency of thermal energy conversion and utilizing polymeric step change composites, which have attracted extremely large interest in recent years due to their advantages of high energy density and powerful energy output stability. A plethora of reviews and reports have been published to compile the diverse range of PCMs made available for various applications. PCMs are created by improving thermophysical thermodynamic stability, latent heat, and heat capacity. Furthermore, the possible applications of polymer phase PCMs in a variety of fields, such as energy storage devices, thermal corrective action, and temperature-controlled drug carriers, are detailed. In this paper, a novel approach on the advancement of nanoconfined phase change material is defined along with the application of the solar energy system.

Operation Mode of Integrated Energy System with Liquid Air Energy Storage

This paper takes the energy supply in the park as the research background, the integrated energy system as the research object and establishes the integrated energy system model including liquid air energy storage, distributed photovoltaic, gas turbines and other equipment. When the integrated energy system operates the mode of “ordering heat by power”, the heat wasted as high as 14.647MWh and the cold wasted as high as 24.13MWh. When the system is not equipped with LAES, the output power of the CCHP unit increases by 21MWh, the electricity purchase in power grid increases by 8.123MWh, the heat waste increases by 21.696MWh and the cold waste increases by 12.421MWh. When the integrated energy system operates the mode of [[CHECK_DOUBLEQUOT_ENT]] ordering power by heat ", heat energy of the system has been reasonably utilized. When the system is not equipped with LAES, the power output and heat of the CCHP unit in the system are the same, the thermal energy output results of the system are the same and the electricity purchased by the power grid increases by 32.14MWh.

Flexible Active Power Control Strategy for Photovoltaic System Based on Current Limiting Control Method

India is country with abundant solar energy availability. The annual solar energy output exceeds the total energy output of India's non renewable energy sources. As increasing installation of renewable energy sources into the grid. The fluctuations of power based on operating climate conditions like solar insulation and temperature is highly depends as it is not possible to limit such installations with time the penetration level of renewable sources will increase to meet demand with green energy. This paper proposed a flexibly power point tracking (FPPT) control of active power in photovoltaic system to achieve reserve capacity with Power Limiting Control (PLC) which will provide high stability to existing system without overloading it thus a proper integration to the grid and to mitigate adverse negative effects of high level integrations are possible with modified grid codes in stand of replacement of existing grid . Matlab/Simulink software package is used to make the model and effectiveness of the propose system is tested with Simulink environment..

Feasibility Study of long term Dual Tank PV/T Indirect Parallel Solar Assisted Heat Pump systems

A novel dual tank PV/T indirect parallel solar assisted heat pump system (DTPV/T-ISAHP) was investigated in this paper, which filled a gap in the literature. Furthermore, a long-term performance study analysis was performed under Tunisian climate to offset domestic electric and hot water loads. Optimal operations of such a system are achieved based on a simplified mathematical model. Results showed that the average thermal and electric energy efficiency is about 39.65% and 11.38%, respectively. Results revealed that the increase in solar radiation results in an improvement of the system's thermal-based COP efficiency coefficient reaching 4.49 at 893 W/m2. PV/T average electrical energy output is found to 0.68 kWh/m2/day with an annual average of 177.42 kWh/m2, which leads to an annual electricity surplus of about 5.83%. A reversible heat pump operation seemed more advantageous especially in the summer months, reducing yearly electric demand by about 84.57%. An economic analysis is undertaken and a payback period of about 12.7 years is found. The current study provided a framework for assessing such a system's behavior and providing useful flexibility to achieve the best possible system performance.

Potential of Floating Photovoltaic Technology and Their Effects on Energy Output, Water Quality and Supply in Jordan

In this work, floating photovoltaic systems were experimentally studied under Jordan’s weather conditions to determine their effects on energy output, water quality and supply. A limited number of studies have addressed the effect of floating photovoltaic systems on water quality and evaporation reduction especially in a semi-arid region like Jordan. Energy measurements were taken from August 2020 to January 2021 using an Arduino board with data logging sensors. Water quality parameters were tested for collected samples on a monthly basis from August 2020 to February 2021 using a spectrophotometer. Results revealed that the floating panel temperature was lower than the ground-mounted counterpart. An average increase of 1.68% in voltage and 4.40% in current were observed for the floating panel compared to the ground-mounted panel which translates to an average increase of 5.33% in power generation over the ground-mounted panel. Furthermore, efficiency and fill factor increased by 4.89% and 5.51%, respectively. Evaporation results showed that covering water bodies with panels can save a considerable amount of water. Over a period of 30 days, the 30% coverage pan saved 31.2% (36 mm) of water while the 50% coverage pan saved 54.5% (63 mm) of water in the same period compared to the uncovered pan. Moreover, this study involved examining the effect of shading caused by the floating structure on water quality. Results showed a reduction in pH, improvement in transparency, and an increase in total organic carbon indicating water quality enhancement and algal biomass reduction. However, due to the respiration of algae, the dissolved oxygen declined significantly, accompanied by the release of phosphate due to algae decomposition. Overall, findings of this research provided better understanding of floating photovoltaic systems and their applicability in Jordan to provide a safe and reliable supply of water and energy. Additionally, such systems can help to diversify the energy mix and help Jordan to alleviate some of the problems associated with limited energy and water resources.

Electric energy planning in Namibe, Angola: Inserting renewable energies in search of a sustainable energy mix

The socioeconomic development of any region requires electricity for operating the various sectors of the economy. Sometimes energy is scarce, not only because of the lack of energy resources, but also because energy policy is inadequate or non-existent. This paper examines the situation in the province of Namibe, Angola, characterising the energy sector, and proposing an energy mix for the security of electricity supply, environmental protection and sustainable economic development. Using the Long-range Energy Alternative and Planning System, energy scenarios were simulated and the greenhouse gas emissions (GHGs) for the period 2014-2040 calculated and analysed. The most sustainable scenario, in terms of energy mix diversification and GHG reduction, as well as the least costly (considering electricity production and carbon costs), has an increase of hydro capacity and the insertion of wind, solar photovoltaic, thermoelectric sources and natural gas. Given the intermittency of photovoltaic and wind systems, natural gas appears in this scenario as a way to avoid interruptions in the electricity supply. This scenario is the one with the largest production reserve margin of 24.47 %, and emissions are avoided at 386 550 tCO2eq compared to the base scenario in 2040. Energy policymakers can take this scenario as a model to assist in making decisions on how power capacities can be installed over the planned time for the desired energy output.

Crop sequence effects on energy efficiency and land demand in a long-term fertilisation trial

The effect of crop sequences (CR – continuous winter rye; CropR – three-field crop rotation of winter rye-spring barley-bare fallow) and fertilisation systems (unfertilised control, mineral fertiliser (NPK), farmyard manure (FYM)) on crop yield, energy efficiency indicators and land demand were analysed in a long-term experiment under Pannonian climate conditions. Due to lower fuel consumption in the bare fallow, the total fuel consumption for CropR was 27% lower than in CR. It was for NPK and FYM fertilisation by 29% and 42% higher than in the control. Although the energy output was lower in CropR than CR, the energy use efficiency for grain production increased by 35% and for above-ground biomass production by 20%. Overall crop sequences, the NPK treatment had higher crop yields, energy outputs and net-energy output with a lower energy use efficiency than the unfertilised control. CropR increased the land demand just by 20% in comparison to CR, although one-third of the land was not used for crop production. The land demand could be decreased with fertilisation by 50% (NPK) or 48% (FYM). A bare fallow year in the crop rotation decreased the crop yield, energy input and increased the energy use efficiency and land demand.