Energies

Research

2110 KiB

Open AccessArticle

The Hidden Burden of Food Waste: The Double Energy Waste in Italy

by Matteo Vittuari, Fabio De Menna and Marco Pagani

Energies 2016, 9(8), 660; https://doi.org/10.3390/en9080660 - 19 Aug 2016

Cited by 30 | Viewed by 8274

The energy intensity of modern food systems represents a major issue in a scenario of decreasing oil resources and increasing population. Beside the use of renewable energy, an increased efficiency in food systems could contribute to reduce fossil fuels dependence. In this sense, [...] Read more.

The energy intensity of modern food systems represents a major issue in a scenario of decreasing oil resources and increasing population. Beside the use of renewable energy, an increased efficiency in food systems could contribute to reduce fossil fuels dependence. In this sense, food losses and waste (FLW) have crucial consequences on the energy balance. Based on the concept of “embodied energy”, food wastage can be framed as a double waste of energy, both in terms of non-consumed food energy and the inputs used for production. Secondary data regarding direct and indirect energy inputs and FLW have been collected for the Italian food chain to estimate the embodied energy of food waste. Since in 2011 the production and distribution of food implied the use of 822 PJ and 18 Mt of food was discarded, 67 PJ of food energy and 100 PJ of embodied energy were wasted. These figures are equivalent to 12.2% of the total nutritional energy output and to 1.3% of the final energy use in Italy, respectively. The concept of double energy waste sheds new light on the intertwined relationship between energy and food security, suggesting that appropriate food waste reduction policies could result in a higher food production level and relevant energy savings. Full article

(This article belongs to the Special Issue Waste Energy Harvesting)

► Show Figures

Graphical abstract

7688 KiB

Open AccessArticle

Performance Analysis of a Reciprocating Piston Expander and a Plate Type Exhaust Gas Recirculation Boiler in a Water-Based Rankine Cycle for Heat Recovery from a Heavy Duty Diesel Engine

by Gunnar Latz, Olof Erlandsson, Thomas Skåre, Arnaud Contet, Sven Andersson and Karin Munch

Energies 2016, 9(7), 495; https://doi.org/10.3390/en9070495 - 29 Jun 2016

Cited by 16 | Viewed by 8000

Abstract

The exhaust gas in an internal combustion engine provides favorable conditions for a waste-heat recovery (WHR) system. The highest potential is achieved by the Rankine cycle as a heat recovery technology. There are only few experimental studies that investigate full-scale systems using water-based [...] Read more.

The exhaust gas in an internal combustion engine provides favorable conditions for a waste-heat recovery (WHR) system. The highest potential is achieved by the Rankine cycle as a heat recovery technology. There are only few experimental studies that investigate full-scale systems using water-based working fluids and their effects on the performance and operation of a Rankine cycle heat recovery system. This paper discusses experimental results and practical challenges with a WHR system when utilizing heat from the exhaust gas recirculation system of a truck engine. The results showed that the boiler’s pinch point necessitated trade-offs between maintaining adequate boiling pressure while achieving acceptable cooling of the EGR and superheating of the water. The expander used in the system had a geometric compression ratio of 21 together with a steam outlet timing that caused high re-compression. Inlet pressures of up to 30 bar were therefore required for a stable expander power output. Such high pressures increased the pump power, and reduced the EGR cooling in the boiler because of pinch-point effects. Simulations indicated that reducing the expander’s compression ratio from 21 to 13 would allow 30% lower steam supply pressures without adversely affecting the expander’s power output. Full article

(This article belongs to the Special Issue Waste Energy Harvesting)

► Show Figures

Graphical abstract

7389 KiB

Open AccessArticle

Optimization Design of an Inductive Energy Harvesting Device for Wireless Power Supply System Overhead High-Voltage Power Lines

by Wei Wang, Xueliang Huang, Linlin Tan, Jinpeng Guo and Han Liu

Energies 2016, 9(4), 242; https://doi.org/10.3390/en9040242 - 26 Mar 2016

Cited by 48 | Viewed by 12800

Abstract

Overhead high voltage power line (HVPL) online monitoring equipment is playing an increasingly important role in smart grids, but the power supply is an obstacle to such systems’ stable and safe operation, so in this work a hybrid wireless power supply system, integrated [...] Read more.

Overhead high voltage power line (HVPL) online monitoring equipment is playing an increasingly important role in smart grids, but the power supply is an obstacle to such systems’ stable and safe operation, so in this work a hybrid wireless power supply system, integrated with inductive energy harvesting and wireless power transmitting, is proposed. The energy harvesting device extracts energy from the HVPL and transfers that from the power line to monitoring equipment on transmission towers by transmitting and receiving coils, which are in a magnetically coupled resonant configuration. In this paper, the optimization design of online energy harvesting devices is analyzed emphatically by taking both HVPL insulation distance and wireless power supply efficiency into account. It is found that essential parameters contributing to more extracted energy include large core inner radius, core radial thickness, core height and small core gap within the threshold constraints. In addition, there is an optimal secondary coil turn that can maximize extracted energy when other parameters remain fixed. A simple and flexible control strategy is then introduced to limit power fluctuations caused by current variations. The optimization methods are finally verified experimentally. Full article

(This article belongs to the Special Issue Waste Energy Harvesting)

► Show Figures

Graphical abstract

1339 KiB

Open AccessArticle

Synergistic Optimization of Thermoelectric Performance in P-Type Bi_0.48Sb_1.52Te₃/Graphene Composite

by Dewen Xie, Jingtao Xu, Guoqiang Liu, Zhu Liu, Hezhu Shao, Xiaojian Tan, Jun Jiang and Haochuan Jiang

Energies 2016, 9(4), 236; https://doi.org/10.3390/en9040236 - 25 Mar 2016

Cited by 34 | Viewed by 6920

Abstract

We report the synergistic optimization of the thermoelectric properties in p-type Bi_0.48Sb_1.52Te₃ by the additional graphene. Highly dense Bi_0.48Sb_1.52Te₃ + graphene (x wt%, x = 0, 0.05, 0.1 and 0.15) composites have been [...] Read more.

We report the synergistic optimization of the thermoelectric properties in p-type Bi_0.48Sb_1.52Te₃ by the additional graphene. Highly dense Bi_0.48Sb_1.52Te₃ + graphene (x wt%, x = 0, 0.05, 0.1 and 0.15) composites have been synthesized by zone-melting followed by spark plasma sintering. With the help of scanning electron microscopy, the graphene has been clearly observed at the edge of the grain in the composites. Due to the additional graphene, the composites show an improved power factor of 4.8 × 10⁻³ Wm⁻¹K⁻² with modified carrier concentration and suppressed lattice thermal conductivity. Consequently, synergistic optimization in electrical and lattice properties by additional graphene leads to a great improvement in the figure of merit ZT (1.25 at 320 K). Full article

(This article belongs to the Special Issue Waste Energy Harvesting)

► Show Figures

Figure 1

2135 KiB

Open AccessArticle

Optimum Electric Boiler Capacity Configuration in a Regional Power Grid for a Wind Power Accommodation Scenario

by Da Liu, Guowei Zhang, Baohua Huang and Weiwei Liu

Energies 2016, 9(3), 144; https://doi.org/10.3390/en9030144 - 1 Mar 2016

Cited by 30 | Viewed by 6565

Abstract

Wind power generation reduces our reliance on fossil fuels and can thus reduce environmental pollution. However, rapid wind power development has caused various issues related to power grid restructuring. A high proportion of the generating capacity of northeast China is based on combined [...] Read more.

Wind power generation reduces our reliance on fossil fuels and can thus reduce environmental pollution. However, rapid wind power development has caused various issues related to power grid restructuring. A high proportion of the generating capacity of northeast China is based on combined heat and power (CHP), whose inflexible response to the peak regulation of power grids hinders the ability to accommodate wind power; thus, wind power curtailment is prevalent. Electric boilers can directly consume the excess wind power to supply heat during low load periods and thus mitigate the heat supply stress of CHP units. Therefore, electric boilers improve the power grid’s ability to accommodate additional wind power. From a regional power grid perspective, this paper discussed the feasibility of such a strategy for increasing the ability to accommodate wind power during the heat supply season. This paper analysed the optimum electric boiler capacity configuration of a regional power grid based on various constraint conditions, such as the heat-power balance, with the objective of maximising the associated social benefits. Using the Beijing-Tianjin-Hebei power grid as an example, the optimum electric boiler capacity of the studied power grid is approximately 1100 MW. Full article

(This article belongs to the Special Issue Waste Energy Harvesting)

► Show Figures

Figure 1

4446 KiB

Open AccessArticle

A Study on the Power Generation Capacity of Piezoelectric Energy Harvesters with Different Fixation Modes and Adjustment Methods

by Zhixiang Li, Gongbo Zhou, Zhencai Zhu and Wei Li

Energies 2016, 9(2), 98; https://doi.org/10.3390/en9020098 - 19 Feb 2016

Cited by 20 | Viewed by 6055

Abstract

The power generation capacity of piezoelectric energy harvesters (PEHs) is not only related to the properties of the piezoelectric material, the vibration magnitude and the subsequent conditioning circuit, but also to the fixation modes and adjustment methods. In this paper, a commercial piezoelectric [...] Read more.

The power generation capacity of piezoelectric energy harvesters (PEHs) is not only related to the properties of the piezoelectric material, the vibration magnitude and the subsequent conditioning circuit, but also to the fixation modes and adjustment methods. In this paper, a commercial piezoelectric ceramic plate (PCP) in simply supported beam fixation mode and cantilever beam fixation mode were analyzed through finite element simulations and experiments, and furthermore, two ways of adjusting the natural frequency of PCP are studied and compared. As a result, some guidelines are proposed for the application of PCPs according to the simulation and experimental results which showed that: (1) the simply supported beam fixation mode is suitable for environments in which the exciting frequency exceeds 50 Hz, while the cantilever beam fixation mode fits the circumstance where the exciting frequency is below 50 Hz; (2) the maximum generation power a PCP produces in simply supported beam fixation mode is larger than that in cantilever beam fixation mode; (3) adjusting the weight of the mass block affixed on the PCP can change the natural frequency of PCP more efficiently than length-width ratio does. Full article

(This article belongs to the Special Issue Waste Energy Harvesting)

► Show Figures

Figure 1

6802 KiB

Open AccessArticle

Numerical Investigation of a Tuned Heave Plate Energy-Harvesting System of a Semi-Submersible Platform

by Kun Liu, Haizhi Liang and Jinping Ou

Energies 2016, 9(2), 82; https://doi.org/10.3390/en9020082 - 28 Jan 2016

Cited by 15 | Viewed by 7565

Abstract

A novel tuned heave plate energy-harvesting system (THPEH) is presented for the motion suppressing and energy harvesting of a semi-submersible platform. This THPEH system is designed based on the principle of a tuned mass damper (TMD) and is composed of spring supports, a [...] Read more.

A novel tuned heave plate energy-harvesting system (THPEH) is presented for the motion suppressing and energy harvesting of a semi-submersible platform. This THPEH system is designed based on the principle of a tuned mass damper (TMD) and is composed of spring supports, a power take-off system (PTO) and four movable heave plates. The permanent magnet linear generators (PMLG) are used as the PTO system in this design. A semi-submersible platform operating in the South China Sea is selected as the research subject for investigating the effects of the THPEH system on motion reduction and harvesting energy through numerical simulations. The numerical model of the platform and the THPEH system, which was established based on hydrodynamic analysis, is modified and validated by the results of the flume test of a 1:70 scale model. The effects of the parameters, including the size, the frequency ratio and the damping ratio of the THPEH system, are systematically investigated. The results show that this THPEH system, with proper parameters, could significantly reduce the motions of the semi-submersible platform and generate considerable power under different wave conditions. Full article

(This article belongs to the Special Issue Waste Energy Harvesting)

► Show Figures

Figure 1

4430 KiB

Open AccessArticle

Power Generation from Concentration Gradient by Reverse Electrodialysis in Dense Silica Membranes for Microfluidic and Nanofluidic Systems

by Sang Woo Lee, Hyun Jung Kim and Dong-Kwon Kim

Energies 2016, 9(1), 49; https://doi.org/10.3390/en9010049 - 15 Jan 2016

Cited by 40 | Viewed by 9302

Abstract

In this study, we investigate power generation by reverse electrodialysis in a dense silica membrane that is between two NaCl solutions with various combinations of concentrations. Each silica membrane is fabricated by depositing a silica layer on a porous alumina substrate via chemical [...] Read more.

In this study, we investigate power generation by reverse electrodialysis in a dense silica membrane that is between two NaCl solutions with various combinations of concentrations. Each silica membrane is fabricated by depositing a silica layer on a porous alumina substrate via chemical vapor deposition. The measured potential-current (V-I) characteristics of the silica membrane are used to obtain the transference number, diffusion potential, and electrical resistance. We develop empirical correlations for the transference number and the area-specific resistance, and present the results of power generation by reverse electrodialysis using the fabricated silica membranes. The highest measured power density is 0.98 mW/m². In addition, we develop a contour map of the power density as a function of NaCl concentrations on the basis of the empirical correlations. The contour map shows that a power output density of 1.2 mW/m² is achievable with the use of silica membranes and is sufficient to drive nanofluidic and microfluidic systems. The dense silica membrane has the potential for use in micro power generators in nanofluidic and microfluidic systems. Full article

(This article belongs to the Special Issue Waste Energy Harvesting)

► Show Figures

Graphical abstract

5099 KiB

Open AccessArticle

Optimal Allocation of Thermal-Electric Decoupling Systems Based on the National Economy by an Improved Conjugate Gradient Method

by Shuang Rong, Weixing Li, Zhimin Li, Yong Sun and Taiyi Zheng

Energies 2016, 9(1), 17; https://doi.org/10.3390/en9010017 - 29 Dec 2015

Cited by 14 | Viewed by 5874

Abstract

Aiming to relieve the large amount of wind power curtailment during the heating period in the North China region, a thermal-electric decoupling (TED) approach is proposed to both bring down the constraint of forced power output of combined heat and power plants and [...] Read more.

Aiming to relieve the large amount of wind power curtailment during the heating period in the North China region, a thermal-electric decoupling (TED) approach is proposed to both bring down the constraint of forced power output of combined heat and power plants and increase the electric load level during valley load times that assist the power grid in consuming more wind power. The operating principles of the thermal-electric decoupling approach is described, the mathematical model of its profits is developed, the constraint conditions of its operation are listed, also, an improved parallel conjugate gradient is utilized to bypass the saddle problem and accelerate the optimal speed. Numerical simulations are implemented and reveal an optimal allocation of TED which with a rated power of 280 MW and 185 MWh heat storage capacity are possible. This allocation of TED could bring approximately 16.9 billion Yuan of economic profit and consume more than 80% of the surplus wind energy which would be curtailed without the participation of TED. The results in this article verify the effectiveness of this method that could provide a referential guidance for thermal-electric decoupling system allocation in practice. Full article

(This article belongs to the Special Issue Waste Energy Harvesting)

► Show Figures

Figure 1

3799 KiB

Open AccessArticle

Waste-to-Energy in China: Key Challenges and Opportunities

by Dongliang Zhang, Guangqing Huang, Yimin Xu and Qinghua Gong

Energies 2015, 8(12), 14182-14196; https://doi.org/10.3390/en81212422 - 16 Dec 2015

Cited by 83 | Viewed by 17482

Abstract

China—the largest developing country in the world—is experiencing both rapid economic maturation and large-scale urbanization. These situations have led to waste disposal problems, and the need to identify alternative energy sources. Waste-to-energy (WTE) conversion processes, a source of renewable energy, are expected to [...] Read more.

China—the largest developing country in the world—is experiencing both rapid economic maturation and large-scale urbanization. These situations have led to waste disposal problems, and the need to identify alternative energy sources. Waste-to-energy (WTE) conversion processes, a source of renewable energy, are expected to play an increasingly important role in China’s sustainable management of municipal solid waste (MSW). The purpose of this research is to investigate the key problems and opportunities associated with WTE, to provide recommendations for the government. This paper begins by describing China’s current MSW management situation and analyzing its waste disposal problems. The major challenges associated with China’s WTE incineration are then discussed from economic, environmental and social points of view. These include the high costs associated with constructing necessary facilities, the susceptibility of facilities to corrosion, the lower heating value of China’s MSW, air pollutant emissions and especially public opposition to WTE incineration. Since discarded waste can be used to produce energy for electricity and heat—thus reducing its volume and the production of greenhouse gas (GHG) emissions—with government policies and financial incentives, the use of WTE incineration as a renewable energy source and part of a sustainable waste management strategy will be of increasing importance in the future. The paper concludes by summarizing the management, economic and social benefits that could be derived from developing the country’s domestic capacity for producing the needed incineration equipment, improving source separation capabilities, standardizing regulatory and legal responsibilities and undertaking more effective public consultation processes. Full article

(This article belongs to the Special Issue Waste Energy Harvesting)

► Show Figures

Figure 1

4514 KiB

Open AccessArticle

Modelling of Evaporator in Waste Heat Recovery System using Finite Volume Method and Fuzzy Technique

by Jahedul Islam Chowdhury, Bao Kha Nguyen and David Thornhill

Energies 2015, 8(12), 14078-14097; https://doi.org/10.3390/en81212413 - 12 Dec 2015

Cited by 31 | Viewed by 9320

Abstract

The evaporator is an important component in the Organic Rankine Cycle (ORC)-based Waste Heat Recovery (WHR) system since the effective heat transfer of this device reflects on the efficiency of the system. When the WHR system operates under supercritical conditions, the heat transfer [...] Read more.

The evaporator is an important component in the Organic Rankine Cycle (ORC)-based Waste Heat Recovery (WHR) system since the effective heat transfer of this device reflects on the efficiency of the system. When the WHR system operates under supercritical conditions, the heat transfer mechanism in the evaporator is unpredictable due to the change of thermo-physical properties of the fluid with temperature. Although the conventional finite volume model can successfully capture those changes in the evaporator of the WHR process, the computation time for this method is high. To reduce the computation time, this paper develops a new fuzzy based evaporator model and compares its performance with the finite volume method. The results show that the fuzzy technique can be applied to predict the output of the supercritical evaporator in the waste heat recovery system and can significantly reduce the required computation time. The proposed model, therefore, has the potential to be used in real time control applications. Full article

(This article belongs to the Special Issue Waste Energy Harvesting)

► Show Figures

Figure 1

6992 KiB

Open AccessArticle

Dynamic Modeling of the Solar Field in Parabolic Trough Solar Power Plants

by Lourdes A. Barcia, Rogelio Peón Menéndez, Juan Á. Martínez Esteban, Miguel A. José Prieto, Juan A. Martín Ramos, F. Javier De Cos Juez and Antonio Nevado Reviriego

Energies 2015, 8(12), 13361-13377; https://doi.org/10.3390/en81212373 - 25 Nov 2015

Cited by 30 | Viewed by 7653

Abstract

Parabolic trough solar power plants use a thermal fluid to transfer thermal energy from solar radiation to a water-steam Rankine cycle in order to drive a turbine that, coupled to an electrical generator, produces electricity. These plants have a heat transfer fluid (HTF) [...] Read more.

Parabolic trough solar power plants use a thermal fluid to transfer thermal energy from solar radiation to a water-steam Rankine cycle in order to drive a turbine that, coupled to an electrical generator, produces electricity. These plants have a heat transfer fluid (HTF) system with the necessary elements to transform solar radiation into heat and to transfer that thermal energy to the water-steam exchangers. In order to get the best possible performance in the Rankine cycle and, hence, in the thermal plant, it is necessary that the thermal fluid reach its maximum temperature when leaving the solar field (SF). Also, it is mandatory that the thermal fluid does not exceed the maximum operating temperature of the HTF, above which it degrades. It must be noted that the optimal temperature of the thermal fluid is difficult to obtain, since solar radiation can change abruptly from one moment to another. The aim of this document is to provide a model of an HTF system that can be used to optimize the control of the temperature of the fluid without interfering with the normal operation of the plant. The results obtained with this model will be contrasted with those obtained in a real plant. Full article

(This article belongs to the Special Issue Waste Energy Harvesting)

► Show Figures

Figure 1

4422 KiB

Open AccessArticle

Simplified Process for Manufacturing Macroscale Patterns to Enhance Voltage Generation by a Triboelectric Generator

by Jun-Ho Yang, Young-Keun Kim and Jae Young Lee

Energies 2015, 8(11), 12729-12740; https://doi.org/10.3390/en81112340 - 11 Nov 2015

Cited by 12 | Viewed by 7039

Abstract

This paper proposes a simple, yet effective and affordable, manufacturing process to enhance the overall efficiency of voltage generation by a triboelectric generator (TEG) using 3D printers for energy-harvesting applications. The proposed method can be classified as macroscale surface patterning, in contrast to [...] Read more.

This paper proposes a simple, yet effective and affordable, manufacturing process to enhance the overall efficiency of voltage generation by a triboelectric generator (TEG) using 3D printers for energy-harvesting applications. The proposed method can be classified as macroscale surface patterning, in contrast to micro- and nanoscale patterning of TEG proposed in previous studies. Experiments were conducted using a designed test-bed system that allowed the control of external factors, such as the magnitude and frequency of the frictional force and the relative humidity, and an output voltage increase of up to 67% was obtained from a TEG with macroscale patterns that increased the surface area by 14%. The peak voltage generated by the TEG was as high as 18 V, and the addition of a designed analog circuit that uses no external power enabled storage of a DC voltage of 0.4 V. In comparison with previous methods that employ micro- or nanoscale patterns, the proposed patterning method is faster and more suitable for mass production. Full article

(This article belongs to the Special Issue Waste Energy Harvesting)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Waste Energy Harvesting

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Benefits of Publishing in a Special Issue

Published Papers (13 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI