Evaluation of bioenergy resources with a global land use and energy model formulated with SD technique

Bioenergy is expected to become one of the key energy resources for global sustainable development. However, bioenergy cannot be infinite, because the land area available for biomass production is limited and a certain amount of biomass must be reserved for food and materials. The purpose of this study is to evaluate global bioenergy potential: for this purpose, the authors developed a global land-use and energy model (GLUE) formulated using a SD (System Dynamics) technique. Through a simulation, the following results were obtained. (1) There will be a certain potential for energy crops harvested from surplus arable land in the developed regions of the world. However, care must be taken because the potential is sensitive to the global food supply and demand. (2) There will be a large bioenergy potential for biomass residues, such as cereal-harvesting residues, animal dung, roundwood felling residues, and timber scrap. The ultimate bioenergy potential, from all the biomass residues, will be 277 EJ/yr in A.D. 2100 in the world. (3) The mature-forest area in the developing regions decreases from 2.1 billion ha in 1990 to 0.8 billion ha in 2100, although it is assumed that the felling area is reforested completely after A.D. 2025. Thus, there will not be much room to obtain more fuelwood from forests in the developing regions.     

Steps towards the development of a certification system for sustainable bio-energy trade

It is expected that international biomass trade will significantly increase in the coming years because of the possibly lower costs of imported biomass, the better supply security through diversification and the support by energy and climate policies of various countries. Concerns about potential negative effects of large-scale biomass production and export, like deforestation or the competition between food and biomass production, have led to the demand for sustainability criteria and certification systems that can control biomass trade. Because neither such criteria and indicator sets nor certification systems for sustainable biomass trade are yet available, the objective of this study is to generate information that can help to develop them. For these purposes, existing certification systems, sets of sustainability criteria or guidelines on environmental or social sound management of resources are analyzed with the purpose to learn about the requirements, contents and organizational set ups of a certification system for sustainable biomass trade. First, an inventory of existing systems was made; second, their structures were analyzed. Key finding from the analysis of internationally applied certification systems was that they are generally led by an international panel that represents all countries and stakeholders involved in the biomass production and trade activities. In third and fourth steps different approaches to formulate standards were described and a list of more than 100 social, economic, ecological and general criteria for sustainable biomass trade was extracted from the reviewed systems. Fifth, methods to formulate indicators, that make sustainability criteria measurable, and verifiers that are used to control the performance of indicators are described. It is recommended to further develop the criteria and indicator (C&I) sets for sustainable biomass trade by involvement of the relevant stakeholders (e.g. biomass producer and consumer) and the analysis of local conditions (e.g. local production potentials and limits, and preferences of local people).     

The impact of oil prices on bioenergy,emissions and land use

We evaluate how alternative future oil prices will influence the penetration of biofuels, energy production, greenhouse gas (GHG) emissions, land use and other outcomes. Our analysis employs a global economy wide model and simulates alternative oil prices out to 2050 with and without a price on GHG emissions. In one case considered, based on estimates of available resources, technological progress and energy demand, the reference oil price rises to $124 by 2050. Other cases separately consider constant reference oil prices of $50, $75 and $100, which are targeted by adjusting the quantity of oil resources. In our simulations, higher oil prices lead to more biofuel production, more land being used for bioenergy crops, and fewer GHG emissions. Reducing oil resources to simulate higher oil prices has a strong income effect, so decreased food demand under higher oil prices results in an increase in land allocated to natural forests. We also find that introducing a carbon price reduces the differences in oil use and GHG emissions across oil price cases.     

Scenario analysis of bioenergy resources and CO2 emissions with a global land use and energy model

The purpose of the present study is to evaluate bioenergy supply potentials, land use changes, and CO₂ emissions in the world, using a global land use and energy model (GLUE) including land use competitions and overall biomass flows. Through a set of simulations, the following results were obtained: (1) Supply potentials of energy crops produced from surplus arable lands will be strongly affected by food supply and demand parameters in the future, such as animal food demand per capita. (2) The policy option, i.e. the world, large-scale introduction of modern fuelwood by felling and planting in existing forest, will cause drastic reduction of the mature forest area but will cause little reduction of the accumulated CO₂ emissions coming from both energy and forest sectors. One reason for this is that the additional CO₂ emissions owing to the land use conversion from the mature forest to the growing forest will partly cancel out the CO₂ reduction owing to the fuel substitution from fossil fuels to fuelwood. (3) When energy recovery of paper scrap is given priority to material recycling, bioenergy will substitute partly for fossil fuels; however the decrease in recycled paper scrap will cause an increase in roundwood felling demand. Hence, the results will be similar to those of (2).     

On the use of an energy certification database to create indicators for energy planning purposes: Application in northern Italy

Energy certification of buildings, mandatory under the European Directive EPBD provides interesting data on the thermo-physical properties and geometry of existing buildings. Although the energy certificate is intended to provide the characteristics of individual buildings, so stimulating the real estate market toward ever better energy performance, data management of the certificates issued over time, using a national or regional energy cadastre, makes available a data base which is useful for energy planning in the building sector.This paper provides the needed results of a benchmarking study on data from the energy cadastre of the Lombardy Region, northern Italy. By integrating data from the energy cadastre (175.778 energy certificates) with the statistical data obtained from the national census, indicators were obtained on the energy performance of existing buildings.The energy indicators obtained, characterised by building type and construction period, normalised as a function of Degree-Days, become an effective tool for energy planning at local and regional scales. In the specific case, the energy indicators have been used to estimate the potential for energy retrofit of existing buildings in the Lombardy Region. The same indicators can also be used by municipalities for energy planning at the municipal or district level.     

Synergistic planning of an integrated energy system containing hydrogen storage with the coupled use of electric-thermal energy

Regional integrated energy systems (RIES) can economically and efficiently use regional renewable energy resources, of which energy storage is an important means to solve the uncertainty of renewable energy output, but traditional electrochemical energy storage is only single electrical energy storage, and the energy efficiency level is low. Hydrogen energy storage has the advantages of large energy storage capacity, long storage time, clean and pollution-free, and can realize the synergistic and efficient utilization of electricity and thermal power. Based on this, this paper proposes a synergistic planning method for an integrated energy system with hydrogen storage taking into account the coupled use of electric-thermal energy, which effectively reduces the system carbon emission and improves the comprehensive energy efficiency level. Firstly, this paper constructs an electric-thermal coupling model of the hydrogen energy storage unit and proposes an optimization strategy for the integrated energy system containing hydrogen storage taking into account the utilization of electricity and thermal power. Secondly, a planning optimization model with the lowest economy and carbon emission and the highest comprehensive energy efficiency was constructed. Third, the CSPO-GE optimization algorithm is proposed for solving the problem, which significantly improves the solution efficiency. Finally, a planning optimization simulation of RIES for a residential community W in northern China verifies the effectiveness of the model and method proposed in this paper. The comparative analysis of the three schemes shows that compared with the integrated energy system with conventional electrochemical energy storage and heat storage tank as the main form of energy storage and the integrated energy system with only hydrogen storage, the integrated energy system with hydrogen storage and heat storage tank can reduce carbon emissions by 43.8% and 7.61%, respectively, and improve the integrated energy efficiency level by 337.14% and 14.44%.     

Application of cool storage air-conditioning in the commercial sector: an integrated resource planning approach for power capacity expansion planning and emission reduction

An assessment is presented of the evaluation of the application of cool storage air-conditioning (CSA) in the commercial sector as a resource in the electricity generation expansion planning. The resultant impacts of analysis of emission costs on annual emissions from power generation are also discussed. A building energy simulation tool is used for assessment of potential savings and peak load shifting of CSA application in commercial buildings. In this study, an integrated resource planning (IRP) model is used to evaluate the economic effectiveness of the CSA option. The IRP analysis with emission costs results in deferring the installation of four units of 1000-MW coal-fired power plant from 2010 to 2011, and one unit of 1000-MW coal-fired power plant and one 200-MW CSA option are removed from the IRP plan. Results show that the CSA option is a viable resource in the least-cost planning and reducing environmental emissions.     

Random preferences towards bioenergy environmental externalities: A case study of woody biomass based electricity in the Southern United States

This paper contrasts alternate methodological approaches of investigating public preferences, the random parameter logit (RPL) where tastes and preferences of respondents are assumed to be heterogeneous and the conditional logit (CL) approach where tastes and preferences remain fixed for individuals. We conducted a choice experiment to assess preferences for woody biomass based electricity in Arkansas, Florida, and Virginia. Reduction of CO₂ emissions and improvement of forest habitat by decreasing risk of wildfires and pest outbreaks were presented to respondents as attributes of using green electricity. The results indicate that heterogeneous preferences might be a better fit for assessing preferences for green electricity. All levels of both attributes were positive contributors to welfare but they were no statistically significant. Respondents expressed a positive mean marginal willingness to pay (WTP) for each attribute level. The total WTP for green electricity per kilowatt hour was $0.049 kWh or $40.5 per capita year^{− 1} when converted into future total annual expenditures.     

基于风电不确定性模糊量化的综合能源系统规划方法研究

综合能源系统是能源结构转型与发展过程中的关键环节,也是高比例可再生能源并网型能源互联网的具体实现。由于多种能源耦合以及可再生能源不确定性等因素的影响,综合能源系统规划设计对经济性和环保性提出了更高要求。文章提出了考虑风电不确定性的综合能源系统能源供给单元容量协调规划决策方法。首先结合风电不确定性集合的区间数量化方法,建立了基于直觉模糊集的风电不确定性量化模型;然后通过对电力系统、热力系统、天然气系统的能源供给单元经济成本和环境成本进行分析,提出考虑风电不确定性的综合能源系统能源供给单元容量协调规划决策模型及求解方法,最大限度降低综合能源系统经济成本和环境成本,提高风电的并网容量;最后通过算例仿真验证了所提规划方法的正确性和有效性。     

A model for sustainable land use in biofuel production: An application to the state of Alabama

The Renewable Fuel Standard aims to increase the production of biofuels to improve energy efficiency and decrease carbon dioxide emissions in the US. The effectiveness of this regulation is being debated by the scientific community regarding carbon emissions from direct and indirect land-use change. A valid alternative may be to design policies that stimulate sustainable land use in biofuel production. This article develops a model that simulates a voluntary program to increase the land use efficiency in production of biofuels. This stochastic dynamic model optimizes the sustainability of biofuels producible by including climate information and participatory decisions on land use. The model is parameterized using the Maximum Entropy econometric technique to present a simulation of the program in the State of Alabama. The results of this simulation show that participatory decisions on land-use may increase the net energy value of produced biofuel up to 215.68% and reduce the carbon emissions by 19.67% towards the state energy goals.     

Comparison of renewable fuels based on their land use using energy densities

In this article energy densities of selected renewable fuels are determined. Energy density is defined here as the annual energy production per hectare, taking energy inputs into account. Using 5 scenarios, consisting of 1 set focusing on technical differences and 1 set focusing on geographical variations, the range of energy densities currently obtained in Europe was determined for the following fuels: biodiesel from rapeseed; bioethanol from sugar beet; electricity from wood, wind and solar PV.The energy densities of the fuels produced from biomass were calculated by determining the energy contained in the energy carrier produced from the crop annually produced on 1 ha, from which the energy inputs for crop cultivation and conversion were subtracted. For wind and solar electricity, the energy density calculation was based on the energy production per turbine or cell and the number of turbines or cells per hectare after which the manufacturing energy was subtracted.Comparing the results shows that, for the average energy density scenarios, the ratio between the energy densities for wind, solar, and biomass is approximately 100:42:1, with wind electricity also having the highest energy output/input ratio.A case study was done in which the energy density was used to calculate the distance a vehicle can cover using the energy carrier annually produced per hectare. This was done for 3 regions, in Mid-Sweden, North-Netherlands, and South-East Spain. The results of the case show that wind electricity results in the largest distance covered, except in Spain, where solar electricity is the most favourable option.     

Internalization of the external costs of global environmental damage in an integrated assessment model

This study simulates the internalization of the external costs of major global environmental issues using an optimal economic growth model. We merged two existing models: an integrated assessment model (IAM) and a life-cycle impact assessment (LCIA) model. We sought to achieve simultaneously the following three objectives: (i) to incorporate environmental issues including global warming in the IAM; (ii) to assess environmental impacts with a bottom-up approach from the LCIA; and (iii) to internalize external costs obtained from the environmental impact study. The study also provides initial simulation results obtained from the merged model.     

Renewable energy sources: Their global potential for the first-half of the 21st century at a global level: An integrated approach

The risk of human-induced climate change and the volatility of world oil markets make non-fossil fuel options important. This paper investigates the potential for wind, solar-PV and biomass (WSB) to deliver energy. The focus is on land opportunities and constraints and on production costs as a function of resource availability and depletion and of innovation dynamics. The context is provided by the IPCC SRES scenarios as simulated with the IMAGE 2.2 model. We explicitly consider several sources of uncertainty, aspects of the food vs. energy trade-off and the effects of interaction between the three options through their claims on land. We show that ‘potential production’ concepts are strongly dependent on the chosen land-use scenario—and should therefore be used with an indication of the underlying assumptions. Our results indicate a potential for liquid biofuels in the order of 75–300 EJ year⁻¹ and for electricity from WSB options at production costs below 10 ¢ kWh⁻¹ of 200–300 PWh year⁻¹. Theoretically, future electricity demand can be amply met from WSB sources in most regions by 2050 below 10 ¢ kWh⁻¹, but major uncertainties are the degree to which land is actually available and the rate and extent at which specific investment costs can be reduced. In some regions, competition for land among the three WSB options may significantly reduce the total potential as estimated from simple addition—which is another source of uncertainty.     

Assessment of the reactor network approach for integrated modelling of an SOFC system

Incorporation of Solid-oxide fuel cells (SOFC) into hybrid systems with CHP capabilities is an attractive option for clean and efficient decentralised electricity generation. SOFC system operation on practical liquid fuels requires an efficient preparation system for the formation of a homogeneous reformate mixture. This can be accomplished with the use of a stabilized cool flame vapouriser (SCFV) combined with a thermal partial oxidation (T-POX) reformer, and such systems are already under development. The successful and efficient thermochemical operation of an SOFC system requires an accurate determination of the optimum conditions for each constituent component (e.g. fuel processing unit, fuel cell stack, off-gas burner) and for the integrated system. The present work demonstrates a computational methodology for the thermochemical assessment of a novel SOFC system operated on liquid fuels. Simulations have been performed, both at component and system levels, using a reactor network approach, involving a simplified flow and mixing representation, while retaining full detailed chemistry. Computations are performed at a component level with reactor networks specially formulated for the SCFV and the T-POX reactors, derived on the basis of CFD calculations, coupled with detailed kinetic mechanisms for n-heptane, a reasonable diesel fuel surrogate. Model predictions are compared against experimental data, wherever possible. The individual components are integrated at a system level and parametric analyses are performed so as to determine optimum conditions for efficient and clean operation.     

Parametric optimum design of an irreversible heat-transformer based on the thermo-economic approach

The thermo-economic objective function of a heat transformer may include other objective functions such as the coefficient of performance and specific heat pumping load. It is defined as the heat-pumping load divided by the total cost per unit time and its expression is derived from the general cycle model of an irreversible heat-transformer. The general objective function is used to analyze the thermoeconomic and thermodynamic optimum performance of a heat transformer affected by multi-irreversibilities. The bounds of some important parameters are determined. The problem of how to choose optimally these parameters are discussed. The results obtained here can provide some new theoretical guidance for the optimal design and operation of heat transformers and heat engines.     

Energy station and distribution network collaborative planning of integrated energy system based on operation optimization and demand response

In the energy station and distribution network collaborative planning of integrated energy system (IES), it is difficult to consider station and network interaction in IES operation at the same time. For resolving this problem, the model and solution of planning and operation alternative optimization are proposed considering multiagent interest balance. First, the three-stage optimization framework and model of station and network planning of IES are proposed based on the operation scheduling of IES and the response of energy station and users as different subjects, aiming at optimization of station and network cost-effectiveness, respectively. Second, the distribution network simplification method is proposed based on topological equivalence principle. The topological structure characteristics of distribution network is analyzed, the rapid generation strategy of single tie line network based on broken circle method is proposed, and then an encoding/decoding scheme is proposed based on particle swarm optimization algorithm. Third, considering the load characteristics and energy station demand response based on flexible comfort level of users, a dynamic spot price optimization method and operation strategy of IES are proposed. And then the station and network collaborative planning solution is presented based on the operation optimization of IES. Finally, an example is given to verify the practicability and effectiveness of the proposed method in this paper.     

Reliability evaluation of power system incorporating wind farm for generation expansion planning based on ANLSA approach

Reliability evaluation of power‐generating systems gives a mechanism to guarantee proper system operations in the face of different uncertainties including equipment failures. It is regularly not attainable to identify all possible failure states to figure the reliability indices because of the large number of system states engaged with system operations. Therefore, a hybrid optimization technique is required to analyse the reliability of the power system. This paper proposes a hybrid optimization technique to evaluate the reliability of a power system for the generation expansion planning incorporating wind energy source. The proposed hybrid methodology is the joined execution of both ant lion optimization algorithm (ALO) and lightning search algorithm (LSA), and it is named as ANLSA. ALO searching behavior is enhanced by LSA. Through the inherent convergence mechanisms, ANLSA search the meaningful system states. The most probable failure states contribute reliability indices of power generating system including mean down time (MDT), loss of load probability (LOLP), loss of load expectation (LOLE), loss of load frequency (LOLF), and expected demand not supplied (EDNS). Furthermore, ANLSA is utilized to assess the reliability of system under normal condition, integration of wind farm with capacity of 150 MW, and considering spinning reserve requirement (SRR). By then, the proposed work is actualized in MATLAB/Simulink platform and it is demonstrated on IEEE reliability test system (IEEE RTS‐79). Furthermore, the statistical analysis of proposed and existing techniques such as Monte Carlo simulation (MCS) and discrete convolution (DC) is considered. The comparison results demonstrate that proposed approach confirms its ability for evaluating the power system reliability.     

Optimization of Stirling engine performance based on an experimental design approach

The Stirling engine performances depend on several physicals characteristics and functioning parameters. The influence of each parameter and of their interactions is difficult to achieve with classical univariate studies. The experimental design is an alternative to identify the parameters sets allowing optimal Stirling engine performances. Hence, a four factor Central Composite Rotatable Design was used to observe the effect of cooling water flowrate, initial charge pressure, heating temperature, and operation time on a Stirling engine brake power. The influence of each parameter and the effect of the interaction between two or three parameters on the engine performances are presented and discussed. Using the surface response method, it appears that initial charge pressure and heating temperature are the more influencing parameters on the Stirling engine performances. With modeling, optimal conditions for the Stirling engine functioning are the following: charge pressure of 8 bar, heating temperature of 500 °C, and cooling water flow rates of 7.34 l/min, independent of the engine operation time. Copyright © 2012 John Wiley & Sons, Ltd.     

Tuning the composition of tri-metal iron based phosphides integrated on phosphorus-doped vertically aligned graphene arrays for enhanced electrocatalytic activity towards overall water splitting

Iron-based metal phosphides (IMPs) have emerged as a new type of bifunctional electrocatalyst for overall water splitting with high efficiency and good stability. We report IMPs nanoparticles' fabrication with different metal element compositions anchored on phosphorus-doped vertically aligned graphene arrays (IMPs/P-VG), which is successfully achieved by tuning the different phosphates in the electroless plating solution. Compared with other metal ratios of electrocatalysts, Fe_0.5Co_1.5Ni_0.5P/P-VG exhibits the best apparent and intrinsic activity in 1 M KOH, and it also shows good stability up to 12 h without any significant degradation. Moreover, benefiting the unique hierarchical vertical arrays nanostructure of the substrate and the trimetallic phosphides' synergetic effects, the Faraday efficiency of the electrolytic cell based on Fe_0.5Co_1.5Ni_0.5P/P-VG double electrode for the overall water-splitting is up to 90%. This study suggests that proper tuning of the composition of metal elements in IMPs and integrated on compatible substrates can effectively improve the electrocatalytic activity of IMPs for water splitting.     

Spatial optimization of Jatropha based electricity value chains including the effect of emissions from land use change

Jatropha was identified as a potential feedstock to satisfy off-grid and on-grid energy solutions. However, the potential has been questioned due to agronomic frustrations, the lack of an organized value chain and heavy criticism on biofuels due to emissions triggered by land use change (LUC). To contribute to the realistic integration of Jatropha in rural development, this article proposes a modeling approach to probe the feasibility of Jatropha-based electrification in rural Africa and the layout of such a value chain.A multi-component modeling setup is presented, featuring a life cycle inventory, spatial modeling and the optimization model, OPTIMASS. In this modeling setup, OPTIMASS is parameterized with data regarding the global warming potential and the potential location of each operation in the value chain including cultivation sites and related LUC emissions. This enables OPTIMASS to spatially design the Jatropha-based on-grid and off-grid electrification value chain (i.e. cultivation, transport and storage, biofuel production and electricity generation) in Southern Mali with minimal GWP to reach 10% substitution of fossil fuels for Jatropha in electricity production for a current and two future electricity demand scenarios.Analysis of the optimization results demonstrates that emissions from transporting the oil are lower than LUC emissions per harvestable seed of other sites. Finally, it can be said that harnessing the entirety of the Jatropha value chain is crucial to make it GWP competitive relative to fossil fuels in which the location of plantations is crucial to attain low LUC-related emissions and viable yields.