Showing papers in "Journal of Renewable and Sustainable Energy in 2015"

Heating and cooling energy trends and drivers in buildings

Abstract: The purpose of this paper is to provide a source of information on thermal energy use in buildings, its drivers, and their past, present and future trends on a global and regional basis. Energy use in buildings forms a large part of global and regional energy demand. The importance of heating and cooling in total building energy use is very diverse with this share varying between 18% and 73%. Biomass is still far the dominant fuel when a global picture is considered; the role of electricity is substantially growing, and the direct use of coal is disappearing from this sector, largely replaced by electricity and natural gas in the most developed regions. This paper identifies the different drivers of heating and cooling energy demand, and decomposes this energy demand into key drivers based on a Kaya identity approach: number of households, persons per household, floor space per capita and specific energy consumption for residential heating and cooling; and GDP, floor space per GDP, and specific energy consumption for commercial buildings. This paper also reviews the trends in the development of these drivers for the present, future – and for which data were available, for the past – in 11 world regions as well as globally. Results show that in a business-as-usual scenario, total residential heating and cooling energy use is expected to more or less stagnate, or slightly decrease, in the developed parts of the world. In contrast, commercial heating and cooling energy use will grow in each world region. Finally, the results show that per capita total final residential building energy use has been stagnating in the vast majority of world regions for the past three decades, despite the very significant increases in energy service levels in each of these regions.

Evaluation and comparison of the levelized cost of tidal, wave, and offshore wind energy

Abstract: In the current context of environmental degradation and depletion of fossil fuels, marine energy has emerged as an alternative to traditional energy resources. However, being in an initial step of development, extracting energy from the ocean is often regarded as difficult and uneconomical. The existing models for assessing marine energy costs are often oversimplified, leading to uncertainties that may hold investors back and slow down the market penetration of this renewable. Therefore, an accurate prediction of marine energy costs is fundamental to drawing conclusions about its competitiveness. Among the different possibilities of marine energy, this paper focuses on the economic analysis of tidal, wave, and offshore wind energy. The individual costs involved in the construction of these offshore energy parks and operation and maintenance tasks during their lifetime are determined. With this information, the levelized cost (€/MW h) is calculated for offshore wind, wave and tidal energy (€165/MW h, €225/MW h and €190/MW h, respectively). It is found that these renewables have a higher energy cost than traditional energy sources; however, considering factors such as the learning rate or externalities enhances their competitiveness. In the second part of this paper, combined energy systems, such as hybrid converters, are presented as a future solution to boost the development of marine energies. The synergies between these renewables are outlined, as well as the cost savings that can be achieved through diversified energy systems.

Experimental and kinetic study on anaerobic digestion of food waste: The effect of total solids and pH

Abstract: This paper presents the results of laboratory experiments carried out on an anaerobic digestion of food waste with respect to the effect of solid concentration and pH. Total solid (TS) content ranging from 5.0% to 15.0% and pH value ranging from 5 to 9 were analyzed. Laboratory scale experiments using 2 l bioreactors were performed in batch mode operated at mesophilic temperature condition with a hydraulic retention time of 30 days. The cumulative volume of biogas produced was used to measure the reactor performance. The methane and carbon dioxide composition of the gas produced was measured using infra-red gas analyzers. The kinetics of biogas produced has been predicted using three different models (Gompertz model, modified Gompertz model, and Logistic model). The experimental results showed that the solid concentration 7.5% of TS and 7 pH produced a maximum biogas yield. The kinetic study showed that modified Gompertz model produced perfect goodness of fit and root mean square error when compared to other two models.

Coupled wake boundary layer model of wind-farms

Abstract: We present and test a coupled wake boundary layer (CWBL) model that describes the distribution of the power output in a wind-farm. This model couples the traditional, industry-standard wake model approach with a “top-down” model for the overall wind-farm boundary layer structure. The wake model captures the effect of turbine positioning, while the “top-down” portion of the model adds the interactions between the wind-turbine wakes and the atmospheric boundary layer. Each portion of the model requires specification of a parameter that is not known a-priori. For the wake model, the wake expansion coefficient is required, while the “top-down” model requires an effective spanwise turbine spacing within which the model's momentum balance is relevant. The wake expansion coefficient is obtained by matching the predicted mean velocity at the turbine from both approaches, while the effective spanwise turbine spacing depends on turbine positioning and thus can be determined from the wake model. Coupling of the constitutive components of the CWBL model is achieved by iterating these parameters until convergence is reached. We illustrate the performance of the model by applying it to both developing wind-farms including entrance effects and to fully developed (deep-array) conditions. Comparisons of the CWBL model predictions with results from a suite of large eddy simulations show that the model closely represents the results obtained in these high-fidelity numerical simulations. A comparison with measured power degradation at the Horns Rev and Nysted wind-farms shows that the model can also be successfully applied to real wind-farms

Sizing and techno-economic analysis of stand-alone hybrid photovoltaic/wind/diesel/battery power generation systems

Abstract: This paper introduces a new proposed design and optimization simulation program for the techno-economic sizing of a stand-alone hybrid photovoltaic/wind/diesel/battery energy system using the iterative optimization. The main function of the new proposed simulation program is to determine the optimum size of each component of a hybrid renewable energy system for the lowest price of generated energy and the lowest value of dummy energy at highest reliability. An accurate methodology for pairing between five Saudi Arabia sites and ten wind turbines from different manufacturers to maximize energy production and minimize the price of the generated power is introduced. This methodology changes the penetration ratio of the renewable energy sources in certain increments to meet the load requirements of the sites under study. A detailed economic methodology to obtain the price of the generated energy is introduced. The new proposed simulation program is implemented in flexible fashion, which is not possible for th...

A new wind-farm parameterization for large-scale atmospheric models

Abstract: In this article, a new model is developed to parameterize the effect of wind farms in large-scale atmospheric models such as weather models. In the new model, wind turbines in a wind farm are parameterized as elevated sinks of momentum and sources of turbulence. An analytical approach is used to estimate the turbine-induced forces as well as the turbulent kinetic energy (TKE) generated by the turbines inside the atmospheric boundary layer (ABL). In addition, the proposed model can take into account not only the effect of wind-farm density but also the effect of wind-farm layout and wind direction. The performance of the new model is tested with large-eddy simulations of ABL flows over very large wind farms with different turbine configurations. The results show that the new model is capable to accurately predict the turbine-induced forces as well as the TKE generated by the turbines inside the ABL.

Investigating wind turbine impacts on near-wake flow using profiling lidar data and large-eddy simulations with an actuator disk model

Abstract: Wind turbine impacts on the atmospheric flow are investigated using data from the Crop Wind Energy Experiment (CWEX-11) and large-eddy simulations (LESs) utilizing a generalized actuator disk (GAD) wind turbine model. CWEX-11 employed velocity-azimuth display (VAD) data from two Doppler lidar systems to sample vertical profiles of flow parameters across the rotor depth both upstream and in the wake of an operating 1.5 MW wind turbine. Lidar and surface observations obtained during four days of July 2011 are analyzed to characterize the turbine impacts on wind speed and flow variability, and to examine the sensitivity of these changes to atmospheric stability. Significant velocity deficits ( VD) are observed at the downstream location during both convective and stable portions of four diurnal cycles, with large, sustained deficits occurring during stable conditions. Variances of the streamwise velocity component, σu, likewise show large increases downstream during both stable and unstable conditions, with ...

Theories and methodology of complementary hydro/photovoltaic operation: Applications to short-term scheduling

Abstract: The recently implemented Longyangxia 320 MW complementary hydro/photovoltaic (PV) project provides a novel operation mode for utility-scale PV power plants. In this paper, the principle of complimentary hydro/PV operation is presented. In short-term scheduling, hydropower can improve the power quality of PV by compensating for the sawtooth-shaped power output curve of PV and for the intermittent and random output of PV. Conversely, in mid- to long-term scheduling and during peak load regulation, PV can compensate the hydro energy deficiency of hydropower via the electricity generated. The concept of virtual hydropower is also proposed. The ability of hydropower to compensate for PV is analyzed, and curtailment situations for solar energy and water as well as their causes are detected. Finally, a calculation model for complementary hydro/PV operation is developed based on the Longyangxia project. The results show that complementary hydro/PV operation can remarkably improve the power quality of PV and is better able to reduce the peak load than a standalone hydropower plant.

An intelligent control strategy of fractional short circuit current maximum power point tracking technique for photovoltaic applications

Abstract: This paper presents an improved Fractional Short Circuit Current (FSCC) Maximum Power Point Tracking (MPPT) technique in which an additional control loop is used to find the proper moment to measure the SCC. The target is to reduce the power losses in MPPT process that occur as a result of intermittent time based short circuit current measurements. The proposed modification enables the conventional FSCC MPPT to decide intelligently about the measurement of SCC thus reduces the number of times the photovoltaic (PV) module is isolated from the load. Although number of algorithms for tracking MPPT has been reported, the proposed method suits well for low cost PV applications. A Matlab/Simulink based model is employed to test the functional abilities of the proposed method. The comparison of the proposed method and conventional time based FSCC method is also presented in the simulation analysis. Finally, a 130W prototype based on the dSPACE DS1104 controller and experimental results are presented to verify the effectiveness of the proposed method. The technique is verified under uniform shading conditions. The results show satisfactory performance against test conditions. V C 2015 AIP Publishing LLC .[ http://dx.doi.org/10.1063/1.4906982]

Potential wave energy production by different wave energy converters around Sicily

Abstract: The performance of several Wave Energy Converter devices is evaluated at three sites located on the west side of Sicily. To select the most energetic site, the average potential wave energy along the coasts of Sicily is evaluated by adopting a third-generation spectral wave propagation model using as boundary conditions the European Centre for Medium-Range Weather Forecasts operational archive wave and wind data. The most energetic sites are on the western side of Sicily. In the three hotspots identified, the mean energy flux is within the range of 5.33–7.52 kW/m. The analysis shows that all considered devices have a low capacity factor in their original configurations (2.19%–5.12%). The main causes of the poor results in terms of energy production are related to the fact that such devices are optimized for high-energy waves. A resizing of the devices on the basis of the local wave climate showed that a capacity factor that exceeds 30% could be obtained.

The effects of mean atmospheric forcings of the stable atmospheric boundary layer on wind turbine wake

Abstract: Interactions between the nocturnal atmospheric boundary layer (ABL) and wind turbines (WTs) can be complicated due to the presence of low level jets (LLJ), a region which creates wind speeds higher than geostrophic wind speed. A study has been performed to isolate the effect of mean forcings of the ABL on turbulence energetics and structures in the wake of WT. Large eddy simulation with an actuator line model has been used as a tool to simulate a full-scale 5-MW WT under two different realistic atmospheric states of the stable ABL corresponding to low- and high-stratification. The study clearly demonstrates that the large-scale forcings of thermally stratified atmospheric boundary characterized by shear- and buoyancy-driven turbulence significantly influence the wake structure of a wind turbine. For the WT in low-stratified ABL, the jets occur above the WT resulting in a strong mixed layer behind the WT. High turbulence results in a faster wake recovery. For the WT in high-stratified ABL, the jets occur near the hub-height resulting in an asymmetric wake structure. The jets confine the mixing to hub-height resulting in a slower wake recovery. Vertical shear causes the interaction of the root- and lower-tip vortices resulting in the instability of the root vortex leading to an enhanced shear stress and turbulent kinetic energy. The tip vortices exhibit mutual inductance between adjacent vortex filaments resulting in vortex merging. LLJs are an important metric associated with mean atmospheric forcings that dictate the turbulence generated in WT wake and the wake recovery of a WT in a stable ABL.

Outdoor performance of organic photovoltaics: Diurnal analysis, dependence on temperature, irradiance, and degradation

Abstract: The outdoor dependence of temperature and diurnal irradiance on inverted organic photovoltaic (OPV) module performance has been analysed and benchmarked against monocrystalline-silicon (c-Si) photovoltaic technology. This is first such report and it is observed that OPVs exhibit poorer performance under low light conditions, such as overcast days, as a result of inflexion behaviour in the current-voltage curves, which limits the open-circuit voltage (VOC) and fill factor. These characteristics can be removed by photo-annealing at higher irradiance levels, which occur diurnally as irradiance increases after sunrise. We also report the first temperature coefficients for OPVs from outdoor data; the OPV modules showed a positive temperature coefficient, which compared to a negative coefficient from the c-Si modules. Overall, the cell degradation outdoors appears very severe for these modules and highlights the need for improved barrier.

Sustainable production of energy from microalgae: Review of culturing systems, economics, and modelling

Abstract: The first generation biofuels primarily produced from crops compete with other food crops for arable land and are recently susceptible as safe and reliable renewable energy resources. The second generation biofuels produced from non-food feedstocks, mainly being microalgae, have been paid increasing attention to. Compared to the first generation biofuels, there are some advantages for microalgae such as high productivity, less land use, low requirement of water quality, environmental use (for wastewater treatment and carbon dioxide (CO2) biomitigation), etc. This paper reviews the current status of the use of microalgae for sustainable production of biofuels and specifically addresses issues to do with culturing systems, processes, economics, and modelling. Open ponds and a variation of closed photobioreactor culturing systems were described in detail. The culture processes are introduced briefly. Techno-economic analyses and analyses of environmental effect mainly due to CO2 biomitigation are performed. Life cycle assessments and the model studies of microalgae production are also reviewed comprehensively in addition.

Performance of smart maximum power point tracker under partial shading conditions of photovoltaic systems

Abstract: Partial shading on photovoltaic (PV) modules reduces the generated power of the PV system than the maximum power generated from each module separately. The shaded PV module acts as a load to unshaded ones which can lead to hot-spot. To alleviate the effect of partial shading, bypass diodes should be connected across each PV modules. Connecting several PV modules together produces multiple peaks (one global peak (GP) and multiple local peaks (LPs)) on partial shading conditions. Maximum power point tracker conventional techniques are designed to follow the GP but they stuck around LPs such as fuzzy logic controller (FLC). In this paper, modified particle swarm optimization (MPSO) using genetic algorism has been used to follow the GP under any operating conditions. MPSO has been studied and compared with the FLC technique to show the superiority of this technique under all operating conditions. Co-simulation between Matlab/Simulink and PSIM has been used to model the PV system under partial shading conditions. The simulation results show that the MPSO technique is more effective than FLC in following the GP. The generated power increases considerably with the MPSO than the FLC technique in shading conditions.

Computational fluid dynamics analysis of the vertical axis wind turbine blade with tubercle leading edge

Abstract: The performance of a vertical axis wind turbine (VAWT) blade with NACA0015 airfoil section has been investigated using the commercial computational fluid dynamics software ANSYS FluentTM. The Semi Implicit Method for Pressure Linked Equations algorithm is chosen to solve the incompressible Navier-Stokes equations. The k-ω shear stress transport turbulence model was selected for the turbulence flow simulations. The simulation results of lift and drag coefficients between angles of attack of 0° and 40° were first validated with the experimental data in order to confirm the boundary layer distributions. The grid numbers and time step sizes were then examined to confirm the simulation accuracy. To exam the 3D effect, a 2.5D model was additionally developed and compared with 2D model. Finally, the predictions of thrust obtained from the blade with tubercle leading edge were compared with the ones from the straight blade. Overall, the thrusts of VAWT with modified turbine blades were lower than the ones with straight blade. The values of the thrust decreased with increasing amplitudes and decreasing wavelengths, mainly due to the structure of the vortices generated at the leading edge of the turbine blade.

Advancement in heterogeneous base catalyzed technology: An efficient production of biodiesel fuels

Abstract: Price fluctuation of petroleum-based diesel, climate change, emerging mandate obligations, availability of new feedstock and the upgrading of conversion technologies are expected to drive biodiesel market to grow robustly in the next coming 10 years. However, the current bottleneck in biodiesel production is the lack of economical sustainable conversion technologies. Generally, industrial production of biodiesel is greatly relied on alkaline homogeneous transesterification reaction. Limitation of the technology, such as multistep process which incur extra pre-step for high acid oil treatment and post-step for biodiesel purification and alkali washing as diminished the economic feasibility and low environmental impact of the entire biodiesel process. Heterogeneous catalysis offers immense potential to develop simple transesterification process, including one step reaction, easy separation, reusability of catalyst, and green reaction. Thus, the aim of this paper is to review the biodiesel production technologies such as blending, micro-emulsion, pyrolysis, and transesterification. Furthermore, recent studies on heterogeneous catalyzed transesterification were presented by discussing the issues such as catalytic performance on different types of biodiesel feedstock, transesterification reaction conditions, limitations encountered by heterogeneous catalysts, and reusability of solid catalysts. The heterogeneous catalysts presented in this review is mainly focused on solid base catalysts, which include single metal oxides, supported metal oxide, binary metal oxide, hydrotalcite, and natural waste shell-based catalyst. Furthermore, current perspectives on application of heterogeneous catalyzed technology in biodiesel industry were discussed herein.

Technical and economic assessment of perovskite solar cells for large scale manufacturing

Abstract: In this paper, we have carried out detailed technical and economic assessment of perovskite solar cells for large scale manufacturing. For ultra-small area of the order of 0.1 cm2, efficiency of 20% or so are reported. However, for area of 25 cm2, the efficiency is about 10%. Based on the photovoltaic module manufacturing requirements of no constraint on the supply of raw materials, low variability of every key process and process-induced defects, low cost of manufacturing, prospects for further cost reduction in the future, green manufacturing, and long-term reliability, there are absolutely no prospects of manufacturing perovskite solar cells. No one has commercialized perovskite solar cells. Thus, contrary to hype in the literature, there is no truth that perovskite solar cells will replace silicon solar cells. We have also examined the role of perovskite solar cells for increasing the efficiency of silicon solar cells and found unsuitable both for two and four terminal device architectures.

Wind power curve modeling in complex terrain using statistical models

Abstract: The simplest power curves model wind power only as a function of the wind speed at the turbine hub height. While the latter is an essential predictor of power output, wind speed information in other parts of the vertical profile, as well as additional atmospheric variables, are also important determinants of power. The goal of this work was to determine the gain in predictive ability afforded by adding wind speed information at other heights, as well as other atmospheric variables, to the power prediction model. Using data from a wind farm with a moderately complex terrain in the Altamont Pass region in California, we trained three statistical models—a neural network, a random forest and a Gaussian process model—to predict power output from various sets of aforementioned predictors. The comparison of these predictions to the observed power data revealed that considerable improvements in prediction accuracy can be achieved both through the addition of predictors other than the hub-height wind speed and the...

Hydrokinetic energy harvesting using tethered undersea kites

Abstract: In this work an emerging hydrokinetic energy technology, Tethered UnderSea Kites (TUSK), is studied. One TUSK concept uses an axial-flow turbine mounted on a rigid underwater kite to extract power from an ocean current or tidal flow. A second concept removes the turbine from the kite, and instead generates power by transmitting hydrodynamic forces on the kite through the flexible underwater tether to a generator on a floating buoy. TUSK systems have potential advantages, mainly the TUSK systems should be able to extract more power from an ocean current or tidal flow than a same-sized fixed marine turbine. This is possible because TUSK kites can move in cross-current motions at velocities significantly higher than the current velocity to increase power output compared to same sized marine turbines. Maximum theoretical power output is estimated for TUSK systems, and detailed comparisons of key performance parameters between TUSK and conventional marine turbines are made. Initial design considerations for TUSK system components are discussed including the underwater kite, buoyancy systems, the floating buoy and mooring system, underwater kite tether, the mounted turbine, and required control systems. Governing equations of motion to study the dynamics of the kite and tether in a TUSK system are developed, and a baseline simulation is studied to estimate kite trajectories, kite pitch, roll and yaw dynamics, power output, kite aerodynamic forces, and tether tensions. The issue of cavitation in TUSK systems at turbine blade tips and on the kite airfoil is studied. Standard cavitation theory is applied to TUSK systems to identify critical cavitation curves as a function of kite operation depth, kite lift-to-drag ratio, and turbine airfoil minimum pressure coefficient.

Investigation of meshing strategies and turbulence models of computational fluid dynamics simulations of vertical axis wind turbines

Abstract: Making good use of vertical axis wind turbines (VAWTs) is an attractive and potential way to deal with the energy and environmental issues due to the unique superiorities of it. Computational Fluid Dynamics (CFD) technology is a useful tool for the design process of VAWTs. Various turbulence models have been developed and available for turbulent flow simulations. Currently, there have been few researchers studying on meshing strategies and turbulence model selections of VAWT simulations. In this paper, 2D unsteady models under 4 meshing strategies and 6 turbulence models were established and simulated to investigate the effect of the above two aspects on numerical simulations of VAWTs. The numerical results were compared with the experimental data of Oler et al. (“Dynamic stall regulation of the Darrieus Turbine,” SAND Report No. 83–7029, Sandia National Laboratories, Albuquerque, 1983, pp. 67–96) and the analytical solution of Deglaire et al. (Eur. J. Mech., B: Fluids 28(4), 506–520 (2009)). The results reveal that a mesh of 213 656 grids is sufficient to meet the requirements of grid independence with the help of boundary layer and size function techniques. Besides, the realizable k-e model enables the closest CFD simulation of the experimental data and shows better prediction performance than the analytical model of Deglaire et al. and other turbulence models.

Constrained optimal control of a point absorber wave energy converter with linear generator

Abstract: This paper investigates a method for optimal control of a point absorbing wave energy converter by considering the constraints on motions and forces in the time domain. The problem is converted to an optimization problem with the cost function being convex quadratic and the constraints being nonlinear. The influence of the constraints on the converter is studied, and the results are compared with uncontrolled cases and established theoretical bounds. Since this method is based on the knowledge of the future sea state or the excitation force, the influence of the prediction horizon is indicated. The resulting performance of the wave energy converter under different regular waves shows that this method leads to a substantial increase in conversion efficiency.

Photovoltaic power generation and its economic and environmental future in Bangladesh

Abstract: Bangladesh is facing an energy crisis that is likely to become worse in the future because of insufficient power generation. Approximately 50% of the total population lives without grid-connected electricity. Moreover, the people connected to the grid are unable to access an even and continuous power supply on a daily basis. This research investigated the potential of renewable energy technologies, specifically photovoltaic (PV) power generation, and its economic and environmental impacts in Bangladesh. The concerns about the costs of PV technologies for Bangladesh were addressed by scenario modeling analysis and calculating the net present cost, cost of energy (COE), and bill savings for a 21-yr period. Results showed that 1 and 2 kWp systems could reduce the total energy cost by US$4495.856 and US$2191.69, respectively, and decrease the COE by 0.198 and 0.096 per kW h in a 21-yr period. Over a 21-yr period, 1 kWp PV systems could lower future emissions by a total of 10 162 kg of CO2, 65 kg of SO2, 30 kg of NOx, and 6 kg of CO, whereas 2 kWp PV systems could reduce future emissions by a total of 20 302 kg of CO2, 129 kg of SO2, 60 kg of NOx, and 12 kg of CO.

Vertical bearing behaviour of the composite bucket shallow foundation of offshore wind turbines

Abstract: A composite bucket shallow foundation (CBSF) has been proposed by Tianjin University to adapt the offshore soft geological conditions of China for wind turbines. Vertical bearing capacity modelling and observation tests regarding the CBSF are performed. The test results are accompanied by numerical simulations to provide a better understanding of the failure mechanism of the CBSF. The upper limit of the vertical bearing capacity of the bucket foundation is derived through the upper bound theorem of classical plasticity theory according to the failure mechanism. The soil damage rate is specified as a new empirical parameter in the formula and is defined as the rate between the thickness of the soil that is broken inside the foundation and the radius of the foundation, which indicates the range of soil failure. Furthermore, the range of the soil damage rate is obtained through vertical bearing capacity model tests. The relationship of the bearing capacity factor Nq and Nγ with the friction angle is also dis...

Preface to Special Topic: Marine Renewable Energy

Abstract: Marine renewable energy (MRE) is generates from waves, currents, tides, and thermal resources in the ocean. MRE has been identified as a potential commercial-scale source of renewable energy. This special topic presents a compilation of works selected from the 3rd IAHR Europe Congress, held in Porto, Portugal, in 2014. It covers different subjects relevant to MRE, including resource assessment, marine energy sector policies, energy source comparisons based on levelized cost, proof-of-concept and new-technology development for wave and tidal energy exploitation, and assessment of possible inference between wave energy converters (WEC).

Techno-economical assessment of renewable energies integrated with fuel cell for off grid electrification: A case study for developing countries

Abstract: One of the development parameters of each country is the accessibility of its different regions to energy resources, especially electrical energy. Therefore, construction of new power plants is inevitable. Nevertheless, limited fossil fuel energy resources and environmental pollutant emissions further proves the necessity toward renewable energy use. To overcome intermittent nature of renewable energies such as solar and wind, development of hybrid energy systems has been proposed. In this study, the feasibility of wind and solar renewable energies was investigated for Khorramabad city as an example of a city in a developing country using HOMER (hybrid optimization model for electric renewable) software. First, data for wind and solar energies were collected from renewable energy organization of Iran. Second, Geographic Information System (GIS) maps were plotted for solar and wind energies of the country and Lorestan Province where the city of Khorramabad is located. Third for Khorramabad city, the amount of electricity generated by wind, solar, and fuel cell sources were investigated in different months of a year, the contribution of each unit in costs, the amount of costs associated to different power plants, and the amount of pollutant emissions from fuel cell using HOMER. The results indicate that the use of fuel-cell system is not recommended for Khorramabad or similar cities in developing countries due to low performance and high initial costs. On the other hand, using a combined system of wind energy, solar energy, and diesel generator will be economical and is recommended.

Dependence of device performance on the thickness of compact TiO2 layer in perovskite/TiO2 planar heterojunction solar cells

Abstract: Planar heterojunction perovskite solar cells (PHJ-PSCs) based on CH3NH3PbI3/TiO2 with high-quality CH3NH3PbI3 films were fabricated by two-step interdiffusion technology. The photovoltaic performance of PHJ-PSCs, including short-circuit-current (Jsc) and open-circuit-voltage (Voc), was found to be strongly dependent on the thickness of TiO2 layer. The largest Jsc was obtained at an optimized TiO2 thickness of 65 nm, resulting in a moderate power conversion efficiency (PCE) of 8.40% with a device structure of fluorine doped SnO2/compact TiO2/CH3NH3PbI3/Spiro-MeOTAD/Ag. A thicker compact TiO2 film could lead to a lower Voc, and the physical mechanism between the Voc and the thickness of compact TiO2 layer was disclosed.

Storage scheduling for optimal energy management in active distribution network considering load, wind, and plug-in electric vehicles uncertainties

Abstract: The storage units decrease the operation cost of active distribution network considerably if they are managed optimally. In this paper, the short-term optimal scheduling of stationary batteries is presented. The point estimate method is used for considering uncertainty of load, wind-based distributed generation and plug-in electric vehicles as well as their influence on optimal scheduling. The optimal scheduling consists of minimizing cost objective function under technical constraints. In this paper, the cost objective function is composed of operation and reliability costs which are minimized using Tabu search algorithm. The storage units are used for several objectives, i.e., peak shaving, voltage regulation, and reliability enhancement. The numerical studies show the advantages of batteries for energy management in active distribution network, and the impact of uncertainties on optimal scheduling.

Study on Australian energy policy, socio-economic, and environment issues

Abstract: This article deals with the Australian total energy consumption related to economic growth and carbon dioxide (CO2) emission in which total energy consumption is sub-divided into renewable and non-renewable energy consumption. The aim of this study is to determine the nexus between all energy elements with gross domestic product and CO2 emission using the Cobb-Douglas equation. The study is based on the Australian panel data over the period from 1976–1977 to 2012–2013. Vector error correction model and generalized method of moments were used to estimate the variables for the relationship between energy variables. The proposed model shows good agreement with the data available on the bioenergy production and consumption in Organization for Economic Co-operation and Development countries. In this model, oil price, oil consumption, carbon tax, renewable energy technology, population growth, urbanization, etc., have been considered as model variables or governing factors. The results show the bidirectional re...

Slow pyrolysis of olive stones in a rotary kiln: Chemical and energy characterization of solid, gas, and condensable products

Abstract: The aim of this work is to investigate the slow pyrolysis of olive stones in a rotary kiln as a means to increase the fuel properties and potential use of this renewable solid fuel. The pyrolysis process takes place primarily at temperatures between 300 and 500 °C resulting in the transformation of the solid biomass into a biochar, a pyrolysis liquid (up to 38.1 wt. %) and a non-condensable gas fraction (up to 35.4 wt. %). This thermal treatment has a positive influence in the fuel properties of the solid fraction in terms of increased C content (up to 75.9 wt. %), reduced O/C and H/C ratios (down to 0.28 and 0.03), reduced volatile matter and moisture content (down to 6.9 wt. % and below 1.0 wt. %, respectively), increased fixed carbon (up to 90.2 wt. %), increased Lower Heating Value (LHVo up to 37.1 MJ/kg) and energy density (26.7 GJ/m3). The process also involved changes in the surface chemistry (increasingly hydrophobic nature) and textural properties of the solid (formation of cracks and internal voids, resulting in the development of a pore structure of up to 0.193 cm3/g and a surface area up to 507 m2/g). The condensable and gas fractions resulting from the pyrolysis process may also be used for their fuel properties. Thus, the pyrolysis liquid exhibited a high water content (62.5 wt. %), a mass density of 1.063 kg/m3, a viscosity of 1.33 cSt, and a Higher Heating Value (HHVo) of 16.9 MJ/kg. The gas fraction resulting from the pyrolysis of olive stones contains high concentrations of combustible gases like CO and H2, and lower proportions of light hydrocarbons. The gas fraction exhibited HHV up to 6.83 MJ/Nm3 due primarily to CO and H2, while the formation of light hydrocarbons was very limited. The energy distribution resulting from the pyrolysis of olive stone at 700 °C (following completion of the thermal degradation) is as follows: solid fraction 48.2%; oil fraction 11.0%; and gas fraction and energy losses (by difference) 40.8%.

CECO wave energy converter: Experimental proof of concept

Abstract: This paper presents the experimental proof of concept of CECO, an innovative wave energy converter designed to convert simultaneously the kinetic and the potential energy of ocean waves into electrical energy, based on the oblique motion of two floating modules. First, the main characteristics of CECO and its work principle are briefly presented. Then, the behavior of the device is analyzed for different wave conditions and modes of operation (power take-off damping levels and device inclinations), based on results obtained with a physical model built on a geometric scale of 1/20. CECO performance strongly depends on the incident wave characteristics, the device inclination angle, and the damping introduced by the power-take-off. Relative capture widths of up to 14% were reached in this initial study, confirming that CECO is a valid technology to extract energy from waves. The application of wavelets showed that CECO response occurs mainly in the frequency of incident waves during the entire test duration.