Harvesting Green Energy Research Articles

Study of phase Stability, Optical, and thermoelectric properties of antiperovskites X3GeO (X=Ca, Sr, Ba) for solar cells and energy harvesting

Perovskites and their inverse derivatives are emerging aspirants for solar cells and energy harvesting applications. Herein, we have comprehensively addressed the phase stability, optical, and transport characteristics of X3GeO (X=Ca, Sr, Ba) antiperovskites by first-principles analysis. The studied compounds have an orthorhombic crystal structure with a space group (1-P1). The phonon spectra have been computed to assess the dynamic stability. The electronic band structures demonstrate that perovskites have narrow band gaps, while the antiperovskites are narrow band gap semiconductors. The calculated values of band gaps for antiperovskites are 0.38, 0.63, and 0.70 eV, respectively, suggesting optimal absorption in infrared to visible regions. Light energy’s dispersion and absorption are calculated by a complex dielectric function, refractive index, and absorption coefficient in the energy range 0 to 5 eV. The Seebeck coefficient, electrical & thermal conductivities, and power factor assess thermoelectric performance at increasing temperatures and carrier concentration. The findings convey a theoretical foundation for future experimental investigations of these antiperovskites and suggest their effectiveness for optoelectronic, and thermoelectric applications to harvest green energy.

Eco-friendly, compact, and cost-efficient triboelectric nanogenerator for renewable energy harvesting and smart motion sensing

In recent years, the growth of Internet of Things devices has increased the use of sustainable energy sources. An alternative technology is offered by triboelectric nanogenerators (TENGs) that can harvest green energy and convert it into electrical energy. Herein, we assessed three different nopal powder types that were used as triboelectric layers of eco-friendly and sustainable TENGs for renewable energy harvesting from environmental vibrations and powering electronic devices. These nanogenerators were fabricated using waste and recycled materials with a compact design for easy transportation and collocation on non-homogeneous surfaces of different vibration or motion sources. In addition, these TENGs have advantages such as high output performance, stable output voltage, lightweight, low-cost materials, and a simple fabrication process. These nanogenerators use the contact-separation mode between two triboelectric layers to convert the vibration energy into electrical energy. TENG with the best output performance is based on dehydrated nopal powder, generating an output power density of 2.145 mWm−2 with a load resistance of 39.97 MΩ under 3g acceleration and 25 Hz operating frequency. The proposed TENGs have stable output voltages during 22500 operating cycles. These nanogenerators can light 116 ultra-bright blue commercial LEDs and power a digital calculator. Also, the TENGs can be used as a chess clock connected to a mobile phone app for smart motion sensing. These nanogenerators can harvest renewable vibration energy and power electronic devices, sensors, and smart motion sensing.

Direct electrospinning of reconstructable PVDF-TrFE nanofibrous mat onto conductive cement nanocomposite for triboelectricity-assisted net zero energy structure

As interest in harvesting green energy and utilizing renewable energy in the building sector has increased, the concept of Net Zero Energy Structure (NZES) has been highlighted. In this study, a strategy to develop the sustainable triboelectricity-assisted NZES is proposed. The multi-walled Carbon nanotube (MWCNT)-incorporated Cement Composite (CCC) is adopted as the structural/electrical member of the triboelectric nanogenerator (TENG) and the polyvinylidene difluoride-trifluoroethylene (PVDF-TrFE) nanofiber is directly electrospun onto the surface of CCC to act as the contact layer of the CCC-based TENG. The optimal concentration of incorporated MWCNT, CMC, is determined to be 1 vol%, considering the compressive strength and electrical property of CCC. The conditions of the electrospinning process for configuring the electrospun PVDF-TrFE nanofibrous mat on the surfaces of CCCs with various shapes are investigated. The electrical output performance of the CCC-TENG is characterized by varying the various environmental and operational parameters. The direct electrospun PVDF-TrFE nanofibrous mat on the CCC-TENG significantly increases the output voltage to approximately 6 times that of flat TENG. The maximum peak power generated from CCC-TENG reaches 60.9 μW when the connected load resistance is 50 MΩ. Furthermore, as a proof-of-concept, the reconstructability of the PVDF-TrFE nanofibrous mat using the direct electrospinning process, as well as the restorations in terms of surface micro/nanostructures and electrical output performance, are demonstrated. Given the wide range of applications of cement and various functionalities of direct electrospinning technology, the sustainable triboelectricity-assisted NZES with CCC and direct electrospun PVDF-TrFE nanofibrous mat is expected to have great potential to take a step toward the development of sustainable Net Zero Energy Community in the future.

Thermoplastic polymer track with gearing mechanism to harvest green energy for sustainable development

Consumption of energy and its demand is increasing constantly. There are various ways to generate energy. Non-renewable energy sources are in high demand, which causes harmful effects on the atmosphere. So environmentally friendly energy sources are very much required. Recently various researchers have been working towards green and environment friendly renewable energy causes. Energy generation from renewable sources, India is within top five position throughout the world. Support towards enhancement of energy generation by renewable sources has been declared by our Honourable Prime minister. The present work deals with a designed model to generate electricity by utilizing energy from footstep movement and vehicle motion. The designed model consists of a gearing mechanism, lever, and thermoplastic polymer track attachment. Thermoplastic tracks are easy to use because of their easier attachment and smooth surface. It is required to attach our designed system in places where maximum mobility of people and vehicle motions is possible. Generally, the places are national highways, temple roads, mall areas, etc. Due to movements on the track, the pressure energy of the foot and vehicle wheels transfers to rotational energy through the gearing attachments of our designed system. This rotational energy is utilized to rotate the armature of the generator to generate electricity and that electricity is stored in the battery for utilization on demand. The lever arm and thermoplastic track are placed with a 10 mm gap so that when load is applied on the track, the thermoplastic will deflect and the load will be transferred to the lever. Due to the provision of a gearing mechanism in our designed system, less input on the track will produce the required rotation of the generator shaft. Natural walking on the track to harvest energy without disturbing the body is very suitable for the stability of this designed system due to the provision of thermoplastic tracks.

Green energy harvesting to power electronic devices using portable triboelectric nanogenerator based on waste corn husk and recycled polystyrene

Green energy harvesting devices are potential sustainable power sources for self-powered sensors, electronics, and the Internet of Things. Triboelectric nanogenerators (TENGs) based on natural polymers and waste materials can harvest green energy from vibration sources to convert it into electrical energy. These nanogenerators could substitute conventional electrochemical batteries to power future smart sensors and electronic devices without contaminating our ambient. Herein, we present a novel portable triboelectric nanogenerator formed by a waste corn husk and a recycled polystyrene (PS) plate as triboelectric layers. This nanogenerator has a compact and lightweight structure developed by a low-cost and eco-friendly fabrication process. This nanogenerator can convert vibrational kinetic energy into electrical energy, achieving a power density of 670.5 mW∙m−2 with a 51.9 MΩ load resistance and operating at 14 Hz. This portable nanogenerator includes simple signal processing and it can power an array of 472 commercial blue LEDs, a digital calculator, and a stopwatch. The output voltage of this nanogenerator is stable even after 25,211 operating cycles at 14 Hz with 25 mm of separation distance between triboelectric layers. The proposed nanogenerator has potential applications to power small electronic devices and sensors using vibrational kinetic energy from the environment.

Design, energy, exergy, economy, and environment (4E) analysis, and multi-objective optimization of a novel integrated energy system based on solar and geothermal resources

Increasing energy consumption rates and concerns over environmental problems like global warming have led researchers to provide new energy supply solutions, one of which is the use of combined energy systems. Combining conventional fossil energy cycles with renewable cycles is one of the most effective ways to improve their performance and also help harvest green energy. To address this solution, in this paper, a hybrid novel energy system including a gas cycle, a steam cycle, two organic Rankine cycles (ORC), and a renewable cycle based on geothermal and solar energy sources using concentrating photovoltaic thermal panels (CPVT) is proposed. A comprehensive study has been conducted on this system from the perspective of energy, efficiency, economy, and the environment. Different fluids have been investigated for use in ORC subsystems in this study. Additionally, a parametric study has been conducted to determine how the cycle's overall performance is affected. Multi-objective optimization using the Non-dominated Sorting Genetic Algorithm second version (NSGA-II) has been performed based on the objective variables of exergy efficiency and capital costs. In this paper, Engineering Equation Solver (EES) and MATLAB are used for modeling and optimization. The results show that the best fluids to use in ORC are R123 in the first cycle and Ammonia in the second cycle, which energy efficiency, exergy efficiency, exergy destruction rate, and generated power in the base state for the whole cycle are 50.59%, 25.44%, 1537.35 kW and 524.66 kW, respectively. Also, the amount of annual capital cost and the amount of carbon dioxide emission from energy and exergy are 107,034 dollars, 11,672, and 35,401 kg per month, respectively. The optimization results indicate a 0.25% improvement in exergy efficiency and a 500$ annual capital cost reduction at the optimal point.

Surface Carbonized Natural Wood via Hydrogen–Oxygen Flame for Electricity Generation from Water Evaporation

Water evaporation-induced power generation technologies based on the interaction between water and nanomaterials have received wide attention over the years. Herein, a natural wood-based water evaporation-induced power generator (EIPG) via the surface carbonization technique under high-temperature hydrogen–oxygen flame was developed. The unique surface carbonization strategy made the internal layer (uncarbonized layer) maintain high hydrophilicity to satisfy the stable and continuous capillary flow for the transport of ions. The internal layer possessed a higher surface charge density, promoting the establishment of the electric double layer (EDL), which ensured high selectivity of the wood channels for positive ions. Meanwhile, the external carbonized layer could effectively adsorb positively charged ions through strong cation−π interactions to strengthen the EDL effect. The carbonized layer also provided an electrical charge transportation channel, lowering the resistance of the device. The device could continuously generate power with an open-circuit voltage (Voc) of ∼170 mV and a short-circuit current (Isc) of ∼730 nA over 24 h, exhibiting excellent stability. Moreover, a higher electric output was generated by the water EIPG through assembling several devices in series or parallel and applied successfully in charging capacitors and powering a commercial digital calculator. This work provides a different strategy for developing an environment-friendly and low-cost water EIPG utilized in harvesting green energy, with no chemical treatment.

Engineering of Sodium-Ion Batteries: Opportunities and Challenges

The recent proliferation of sustainable and eco-friendly renewable energy engineering is a hot topic of worldwide significance with regard to combatting the global environmental crisis. To curb renewable energy intermittency and integrate renewables into the grid with stable electricity generation, secondary battery-based electrical energy storage (EES) technologies are regarded as the most promising solution, due to their prominent capability to store and harvest green energy in a safe and cost-effective way. Due to the wide availability and low cost of sodium resources, sodium-ion batteries (SIBs) are regarded as a promising alternative for next-generation large-scale EES systems. This review discusses in detail the key differences between lithium-ion batteries (LIBs) and SIBs for different application requirements and describes the current understanding of SIBs. By comparing technological evolutions among LIBs, lead-acid batteries (LABs), and SIBs, the advantages of SIBs are unraveled. This review also offers highlights on commercial achievements that have been realized based on current SIB technology, focusing on an introduction of five major SIB companies, each with SIB chemistry and technology, as well as commercialized SIB products. Last but not least, it discusses outlooks and key challenges for the commercialization of next-generation SIBs.

A Portable Triboelectric Nanogenerator Based on Dehydrated Nopal Powder for Powering Electronic Devices.

Triboelectric nanogenerators (TENGs) based on organic materials can harvest green energy to convert it into electrical energy. These nanogenerators could be used for Internet-of-Things (IoT) devices, substituting solid-state chemical batteries that have toxic materials and limited-service time. Herein, we develop a portable triboelectric nanogenerator based on dehydrated nopal powder (NOP-TENG) as novel triboelectric material. In addition, this nanogenerator uses a polyimide film tape adhered to two copper-coated Bakelite plates. The NOP-TENG generates a power density of 2309.98 μW·m-2 with a load resistance of 76.89 MΩ by applying a hand force on its outer surface. Furthermore, the nanogenerator shows a power density of 556.72 μW·m-2 with a load resistance of 76.89 MΩ and under 4g acceleration at 15 Hz. The output voltage of the NOP-TENG depicts a stable output performance even after 27,000 operation cycles. This nanogenerator can light eighteen green commercial LEDs and power a digital calculator. The proposed NOP-TENG has a simple structure, easy manufacturing process, stable electric behavior, and cost-effective output performance. This portable nanogenerator may power electronic devices using different vibration energy sources.

Molecular architecting of photothermal hydrogels reinforced by polar-porous C2NxO1-x for efficient solar water purification

Solar-powered interfacial evaporation provides a sustainable and effective means of harvesting green energy to relieve the global water scarcity issues. While hydrogel evaporators are effective for purifying the contaminated or saline water, the use of hydrophobic carbon-based light-absorbers that compromises the hydratability and local heat exchange poses an impediment to the evaporation rates. Herein, we propose a concept of using heteroatoms-rich and porous C2NxO1-x as the light absorber for molecular design of hydrogel-based evaporators for solar-powered water purification. The synergy of abundant polar groups within C2NxO1-x and hydratable skeleton (chitosan and polyvinyl alcohol) enables the decline of water evaporation enthalpy and thus facilitates vapor generation. The hydrophilic C2NxO1-x that penetrates hydrogel network enlarges the pore aperture with improved pore interconnectivity, which allows for rapid water transport and sufficient water supply. Importantly, the converted energy was localized to sufficiently power the evaporation of water molecules present in polar pores of C2NxO1-x due to adequate heat exchange. The resultant photothermal hydrogel attains a high evaporation rate of ca. 2.9 kg m−2 h−1 with an ultrahigh ion removal efficiency (99.9 %) in both simulated seawater and complex ionic contaminants under one sun irradiation. This study offers a useful guideline of utilizing hydrophilic porous light-absorber to develop high-performance hydrogel for efficient solar-powered water purification.

Techno Economic Analysis of Cotton Stalk Biomass Based Bio-Oil Production Using Slow Pyrolysis Process

In Indian context, green energy mission can be fulfilled through harvesting green energy from agriculture residue which is available abundantly. Slow pyrolysis may be a prominent technology to convert these low value agricultural biomasses into high value products such as Bio-oils, Pyro- gas and Bio-char, which finds vast applications as energy sources. Authors in this paper have presented a Techno-economic analysis of cotton stalk through slow pyrolysis process .Lab scale slow pyrolysis process was performed in batch scale Pyrolyzer at 500 °C temperature, 10 C°/min heating rate and 1-hour residence time as input parameters and Bio-Oil, Bio-Char and Pyro-Gas were obtained as output of slow pyrolysis process having process yields of 36.60 %, 37.78% and 25.25% respectively. Bio-oil and bio-char can be used to generate direct revenue, while pyro-gas may be used as energy source for process heating. Entire plant was assessed economically by considering nth process plant assumption and 20 Tone/day capacities. Techno economic viability of plant was assessed by evaluating plant capital investment and operating cost. Plant capital investment was calculated based on total purchased equipment cost where as Total purchased equipment cost was calculated using equipment scale factor. Operating cost of entire plant was analyzed based on fixed capital investment. Plant economic evaluation was carried out by evaluating Minimum fuel selling price; Payback period and net present value. Estimated Minimum fuel selling price of the plant was ₹66.30/Liter ($ 0.068/liter), payback period of the plant was 3 years and Positive cash flow in Net Present Value.

Phase-separated porous PVDF-CO-HFP thin film for High-power triboelectric nanogenerator

Triboelectric nanogenerator (TENG), one of the latest and most effective technologies to harvest green energy in the industrialization and modernization era, converts mechanical energy to electricity through triboelectrification and electrostatic induction. Herein, highly porous poly(vinylidene fluoride-co-hexafluoropropylene) (PDVF-co-HFP) as a negatively charged tribomaterial was assembled with microdome-patterned chitosan as a positively charged surface to fabricate TENG and examine its mechanical and electrical properties. The results revealed that the porous PVDF-co-HFP-based TENG could generate a maximum instantaneous power of 3 mW and an open-circuit voltage of 200 V, which is 4 times higher than that made from flat PVDF-co-HFP and could light up 102 LEDs. The newly developed PVDF-co-HFP-based TENG achieves a great convergence between excellent flexibility, scalability, and superior electrical output, which has great application potential in wearable electronic devices.

Dye extracted from Bael leaves as a photosensitizer in dye sensitized solar cell

This study has explored a new plant source, Bael tree leaves, as an efficient dye extraction towards green energy harvesting through dye-sensitized solar cells (DSSCs). The photosensitizers, photo-absorption, bandgap, and ionic conductivity characteristics of the extracted dye were determined using thin-layer chromatography (TLC), ultraviolet-visible spectroscopy, Tauc plot, and conductivity meter, respectively. Chlorophyll is the main constituent in the extracted dye confirmed by TLC analysis. An optimum concentration (0.2 g ml−1) with ionic conductivity of 455 μS cm−1 of the dye was used as a photoactive layer in DSSC, demonstrating power densities of 1.345 μW m−2 and 8.078 μW m−2 under the illumination of the LED lamp (1555 lx) and tungsten bulb (1926 lx), respectively. Additional parameters, including fill factor (0.26), ideality factor (1.25), characteristic resistance (309 Ω), series resistance (313 Ω), and shunt resistance (662 Ω) of the fabricated DSSC under tungsten illumination reveal that the novel Bael tree leaves-based dye can harvest green energy efficiently through DSSCs.

Mutually exclusive ytterbium and nitrogen co-doping of mesoporous titania-carbon for self-cleanable and sustainable triboelectric nanogenerators

Herein, we report a mutually exclusive ytterbium and nitrogen co-doping strategy for mesoporous titania-carbon (YbNTiO2@C) specially designed for the positive electrode materials towards self-cleaning functionality and high-power triboelectric nanogenerators. Nano-porous structures of YbNTiO2@C having higher surface energy not only provide the enlarge platform for atom-to-atom contacts, but also increase the charge density of the tribo-layer by accelerating the effective electronic quantum transition effects in-between the opposite electrodes in comparison with pristine TiO2. The formation of crystal defects due to doping of ytterbium on the regular lattice structure of TiO2 along with unique substitutional and interstitial nitrogen-doping boosts the overall surface polarity and increases the charge storage and discharge capability when exposed as an interactive electrode surface in dry-type capacitive triboelectric nanogenerators (TENGs). Therefore, YbNTiO2@C coated tribo-positive electrode not only shows considerable enhancement of TENG performances, but also provides significant improvement in self-cleaning function under sunlight. The YbNTiO2@C layer shows remarkable output triboelectricity up to 3 folds and self-cleaning decomposition of methylene blue up to 96.40% within a minute. Notable improvements in both self-cleaning ability and high-performance power generation enable the realization of an ideal smart roof for harvesting green energy from rain and wind in cloud weather.

Bioinspired Hierarchical Nanofabric Electrode for Silicon Hydrovoltaic Device with Record Power Output.

Direct electricity generation from water flow/evaporation, coined hydrovoltaic effect, has recently attracted intense interest as a facile approach to harvest green energy from ubiquitous capillary water flow or evaporation. However, the current hydrovoltaic device is inferior in output power efficiency compared to other renewable energy devices. Slow water evaporation rate and inefficient charge collection at device electrodes are two fundamental drawbacks limiting energy output efficiency. Here, we report a bioinspired hierarchical porous fabric electrode that enables high water evaporation rate, efficient charge collection, and rapid charge transport in nanostructured silicon-based hydrovoltaic devices. Such an electrode can efficiently collect charges generated in nanostructured silicon as well as induce a prompt water evaporation rate. At room temperature, the device can generate an open-circuit voltage (Voc) of 550 mV and a short-current density (Jsc) of 22 μA·cm-2. It can output a power density over 10 μW·cm-2, which is 3 orders of magnitude larger than all those reported for analogous hydrovoltaic devices. Our results could supply an effective strategy for the development of high-performance hydrovoltaic devices through optimizing electrode structures.

Ultraviolet-protecting, flexible and stable photovoltaic-assisted piezoelectric hybrid unit nanogenerator for simultaneously harvesting ultraviolet light and mechanical energies

Owing to the ecological destruction and the energy crisis, harvesting green energy from the environment has become a hot issue in modern times. Here, a facile, flexible and stable hybrid unit nanogenerator (NG) with ultraviolet (UV) protection based on poly(vinylidene fluoride) (PVDF) piezoelectric nanogenerator (PENG) unit and ultraviolet photovoltaic (SC) unit is fabricated. Specially, self-made thiophenyl soluble conjugated polymer (scp)/zinc oxide (ZnO) quantum dots nanocomposite film was prepared by spin-coating in ambient air condition as UV photoelectric and UV-protective thin film. The flexible photovoltaic films were found to exhibit good photovoltaic performance with a dominating fraction of UV absorption. Under external mechanical forces and UV LED illumination, and the open-circuit output voltage and short-circuit current of the device were significantly enhanced by UV LED constant light exposure. To specify this device performance, the effects of different external mechanical forces and UV illumination on the output of hybrid unit are also analyzed, the open-circuit output voltage of the device was significantly influenced by UV illumination. To demonstrate the practical applications of flexible hybrid unit NG, it exhibits high performance with a maximum power density of 0.97 mW/cm3. The device is able to charge a 33-μF capacitor to 3.6 V within a short time span (60 s) and drive a red LED for a few seconds. This work explores new prospects for UV-protective energy harvesting which can eventually boost up the self-powered electronic robotics and wearable systems based on renewable energy.

Flexible Organic Thermoelectric Materials and Devices for Wearable Green Energy Harvesting.

In the past few decades, organic thermoelectric materials/devices, which can exhibit remarkable potential in green energy conversion, have drawn great attention and interest due to their easy processing, light weight, intrinsically low thermal conductivity, and mechanical flexibility. Compared to traditional batteries, thermoelectric materials have high prospects as alternative power generators for harvesting green energy. Although crystalline inorganic semiconductors have dominated the fields of thermoelectric materials up to now, their practical applications are limited by their intrinsic fragility and high toxicity. The integration of organic polymers with inorganic nanoparticles has been widely employed to tailor the thermoelectric performance of polymers, which not only can combine the advantages of both components but also display interesting transport phenomena between organic polymers and inorganic nanoparticles. In this review, parameters affecting the thermoelectric properties of materials were briefly introduced. Some recently developed n-type and p-type thermoelectric films and related devices were illustrated along with their thermoelectric performance, methods of preparation, and future applications. This review will help beginners to quickly understand and master basic knowledge of thermoelectric materials, thus inspiring them to design and develop more efficient thermoelectric devices.

Synergistic effect of polydopamine-polyethylenimine copolymer coating on graphene oxide for EVA nanocomposites and high-performance triboelectric nanogenerators.

While the demand for lightweight high-strength nanocomposites is immense, their progress has been severely limited due to inferior filler dispersion and filler–matrix interface adhesion. This article reports a novel modification of graphene oxide (GO) encapsulated by the copolymer of polydopamine (PD) and polyethylenimine (PEI) via a Michael addition reaction, aiming to create robust ethylene vinyl acetate copolymer (EVA) nanocomposites even at very low amounts of filler loading by overcoming the above hindrances. It has been found that the addition of only 1.2 wt% modified GO (i.e., PD–PEI–rGO) increased the tensile strength, Young's modulus and storage modulus of EVA composites by 80%, 50% and 24%, respectively. These increments surpass many recent claims on relevant composites. Excellent molecular level dispersion was also observed from the fracture surface SEM images. Being amine-rich with high electron-donating capability and mechanically robust, the nanocomposite served as an outstanding tribopositive material, thereby generating 7.49 V and 4.06 μA output voltage and current, respectively, when employed in a triboelectric nanogenerator (TENG). The high electrical outputs led the device to light up 43 blue LEDs instantaneously upon hand pressing, demonstrating that the nanocomposite is indeed a promising candidate for harvesting green energy. Moreover, the nanogenerator displayed outstanding cyclic performance stability (even after 8000 cycles) and environmental durability.

Green energy generation through PEHF – a blueprint of alternate energy harvesting

ABSTRACTIn this work, an attempt has been made to harvest green energy from piezoelectric material using fluid flow in a conduit. Piezoelectric Energy Harvesting using Fluid Flow (PEHF) experimental model has been designed and the outputs obtained are compared with results obtained from simulations using ANSYS (computational fluid dynamics) and also with the mathematical modeling. The PEHF model has been utilized to analyze the effect of flow rate of water with reference to energy extracted. The full wave bridge rectifier and voltage doubler circuits have been used to obtain the direct current (DC) from the PEHF model. It is observed that the output obtained using experiments holds good in agreement with the results retrieved through simulations and mathematical results. The increase in flow rate of fluid leads to initially increase and then decrease in output of PEHF model as the maximum energy generated when flow rates (external force) matches with the frequency of excitation of the systems, i.e., at its resonance. The maximum energy output is generated at its resonance frequencies. It is observed that the full wave bridge rectifier circuit gives greater output as compared to a voltage doubler circuit.

Towards energy efficient service composition in green energy powered Cyber–Physical Fog Systems

After decades of fast development in Cyber–Physical System (CPS), CPS services are becoming more and more ubiquitous. While, the still growing trends on ambient intelligence asks for more smart CPS applications. Meanwhile, fog computing may also exhibit advantage on the energy efficiency as the fog nodes are distributed in the environment and can harvest green energy from the environment. Fog computing has been regarded as an ideal platform for the distributed and diverse CPS applications. In this paper, we are motivated to investigate how to explore the energy generation diversity in fog computing platform to achieve energy efficient service composition in a green energy powered Cyber–Physical Fog System (CPFS), with the joint consideration of source rate control, load balancing and service replica deployment. The energy efficiency problem is formulated as a mixed integer linear programming (MILP) and proved as NP-hard. To address the computation complexity, we further propose a heuristic algorithm. Extensive simulation studies are conducted and the results show the high energy efficiency of our algorithm by the fact it performs much close to the optimal solution.