On the physics of power,energy and economics of renewable electric energy sources – Part I

Environmental concerns have increasingly led to the installation of Renewable Energy Technologies (RETs) despite the fact that they are recognized as expensive. Innovative efforts within the area are beset with difficulties [1], and they are at risk of producing misdirected or insignificant improvements in terms of the cost effectiveness of total energy conversion systems. This paper investigates how RETs can be evaluated, in terms of economy and engineering solutions, by studying the fundamental physics of renewable energy sources and how it matches with the RETs. This match is described by the “Degree of Utilization”. The findings indicate that new innovations should focus on the possible number of full loading hours. RETs that are correctly matched to their energy source generate a higher amount of electric energy and have a higher potential of becoming more competitive. In cases where this aspect has been ignored, leading to relatively small degrees of utilization, it can be understood as an engineering mismatch between installed power, converted energy, and the fundamental physics of the renewable energy sources. Since there is a strong and possibly biased support for so-called mature RETs and already existing solutions, a clarification of how fundamental physical laws affect the cost of investments and payback of investments is needed. The present paper is part I out of II and it focuses on the difference between power and energy and the physics of different energy sources and their utilization.     

Modelling of hybrid energy system—Part III: Case study with simulation results

This paper presents the results of the application of model (developed in part I) and simulation algorithm (developed in part II) for determining the techno-economics of battery storage type hybrid energy system intended to supply the load of a rural remote area having a cluster of nine villages (grid isolated). The hour-by-hour simulation model is intended to simulate a typical one month period of system operation. For simulation purpose, hourly solar insolation data and load data have been generated and used as an input data. Demand side management (DSM) is used in this study to smooth out the daily peaks and fill valleys in the load curve to make the most efficient use of energy sources. The economic analysis has resulted in the calculation of optimized hourly, daily, and monthly system unit cost of proposed hybrid energy system. The obtained results represent also a helpful reference for energy planners in Uttarakhand state and justify the consideration of hybrid energy systems more seriously.     

Rail transportation by hydrogen vs. electrification – Case study for Ontario,Canada, II: Energy supply and distribution

Locomotives offer an efficient mode of transportation when compared to buses, personal vehicles or airplanes for mass transportation over frequent intercity distances. For example, a Bombardier Regina EMU train with 272 seats and a load factor of 53% will consume under 0.07 kWh/passenger-km, which is typically much lower than corresponding values for other transportation modes in similar circumstances. European countries have invested significantly over the years in train electrification. Environmentally friendly methods of transferring power to the wheels are direct electrification and hydrogen fuel cells. Various methods to produce hydrogen for utilization with fuel cell train operation are examined in this paper.     

Investment in oil and gas field materials technology – the key to a secure energy supply

Abstract

Many national and international programmes have renewable energies as a prime focus for long term R&D investment. This focus arises from an environmental perspective and the objective of a carbon abatement energy society, and may also be fuelled by often over-dramatised reports of declining oil and gas reserves. It is argued that investment in oil and gas must be a vital component of R&D planning and energy policy if energy supplies are to be assured, and that advances in materials and materials technologies will be key to these efforts.     

Techno-economic analysis of using corn stover to supply heat and power to a corn ethanol plant – Part 2: Cost of heat and power generation systems

This paper presents a techno-economic analysis of corn stover fired process heating (PH) and the combined heat and power (CHP) generation systems for a typical corn ethanol plant (ethanol production capacity of 170 dam³). Discounted cash flow method was used to estimate both the capital and operating costs of each system and compared with the existing natural gas fired heating system. Environmental impact assessment of using corn stover, coal and natural gas in the heat and/or power generation systems was also evaluated. Coal fired process heating (PH) system had the lowest annual operating cost due to the low fuel cost, but had the highest environmental and human toxicity impacts. The proposed combined heat and power (CHP) generation system required about 137 Gg of corn stover to generate 9.5 MW of electricity and 52.3 MW of process heat with an overall CHP efficiency of 83.3%. Stover fired CHP system would generate an annual savings of 3.6 M$ with an payback period of 6 y. Economics of the coal fired CHP system was very attractive compared to the stover fired CHP system due to lower fuel cost. But the greenhouse gas emissions per Mg of fuel for the coal fired CHP system was 32 times higher than that of stover fired CHP system. Corn stover fired heat and power generation system for a corn ethanol plant can improve the net energy balance and add environmental benefits to the corn to ethanol biorefinery.     

Pricing and affordability of renewable energy in China – A case study of Shandong Province

The global warming and climate change have put enormous pressure on both governments and industries to re-think their attitudes and behaviours towards sustainability issues. The past decades have witnessed a number of renewable energy developments across the world. Even though these developments are not issue-free, it is generally recognized that the benefits outweigh disadvantages. However, there is an increasing level of concern on the high initial cost associated with the renewable energies, which was claimed as one of critical barriers to the promotion of its further developments. A case study approach is adopted in this study to investigate the pricing and affordability issues associated with the renewable energy in China. The policy framework and related statistics are critically reviewed in order to discuss these issues from different stakeholders’ perspective in Shandong province, China. It is concluded that the affordability remains a critical issue despite numerous efforts have been made by the Chinese Government and Shandong Provincial Government on renewable power pricing. This study offers a useful reference to pricing and affordability of renewable energy.     

Energy,environmental and economic comparison of different powertrain/fuel options using well-to-wheels assessment,energy and external costs – European market analysis

The well-to-wheels assessment is widely used in the automotive sector to analyze the efficiency and competitiveness of different powertrain/fuel options. The paper proposes a global index that takes into account both the energy and environmental aspects on an uniform basis, through the assignment of the costs associated to the energy and to the pollutant emissions. The European market is analyzed and other pollutants (NO_x, PM and SO_x) are added to the traditional well-to-wheels evaluations (energy and GHG). The proposed well-to-wheels global index offers a useful place-list that takes into account both energy and environmental aspects and, at the current market conditions, it results that the energy cost prevails (70–85%) over the environmental costs, and among the analyzed external costs, the main contribution is due to the GHG emissions. Natural gas-derived fuels seem to be the most promising. The global index for battery electric vehicle from a European mix are closely linked to the driving range. Conventional biofuels are very critical at present, while significant improvement of the well-to-wheels global index is foreseen for when new generation biofuels will be mature (2030 forecast). In short, even though the proposed global index is not an exhaustive index, it could be a useful tool for decision makers.     

Centralized and decentralized electrolysis-based hydrogen supply systems for road transportation – A modeling study of current and future costs

This work compares the costs of three electrolysis-based hydrogen supply systems for heavy road transportation: a decentralized, off-grid system for hydrogen production from wind and solar power (Dec-Sa); a decentralized system connected to the electricity grid (Dec-Gc); and a centralized grid-connected electrolyzer with hydrogen transported to refueling stations (Cen-Gc). A cost-minimizing optimization model was developed in which the hydrogen production is designed to meet the demand at refueling stations at the lowest total cost for two timeframes: one with current electricity prices and one with estimated future prices. The results show that: For most of the studied geographical regions, Dec-Gc gives the lowest costs of hydrogen delivery (2.2–3.3€/kgH₂), while Dec-Sa entails higher hydrogen production costs (2.5–6.7€/kgH₂). In addition, the centralized system (Cen-Gc) involves lower costs for production and storage than the grid-connected decentralized system (Dec-Gc), although the additional costs for hydrogen transport increase the total cost (3.5–4.8€/kgH₂).     

Assessing the impact of renewable energy sources on the electricity price level and variability – A quantile regression approach

The literature on renewable energy sources indicates that an increase of the intermittent wind and solar generation affects significantly the distribution of electricity prices. In this article, the influence of two types of renewable energy sources (wind and solar photo voltaic) on the level and variability of German electricity spot prices is analyzed. The quantile regression models are built to estimate the merit order effect for different quantiles of electricity prices. The results indicate that both types of renewable generations have a similar, negative impact on the price level, approximated by the price median. When the price volatility, measured by the inter-quantile range (IQR), is considered, the outcomes show that wind and solar influence prices differently. Conditional on the level of the total demand, the wind generation would either increase (when the demand is low) or decrease (when the demand is high) the IQR. Meanwhile, the increase of solar power stabilizes the price variance for moderate demand level. Thus, policy supporting the development and integration of RES should search for a balance between the wind and solar power.     

Food transport refrigeration – Approaches to reduce energy consumption and environmental impacts of road transport

Food transport refrigeration is a critical link in the food chain not only in terms of maintaining the temperature integrity of the transported products but also its impact on energy consumption and CO₂ emissions. This paper provides a review of (a) current approaches in road food transport refrigeration, (b) estimates of their environmental impacts, and (c) research on the development and application of alternative technologies to vapour compression refrigeration systems that have the potential to reduce the overall energy consumption and environmental impacts. The review and analysis indicate that greenhouse gas emissions from conventional diesel engine driven vapour compression refrigeration systems commonly employed in food transport refrigeration can be as high as 40% of the greenhouse gas emissions from the vehicle’s engine. For articulated vehicles over 33 ton, which are responsible for over 80% of refrigerated food transportation in the UK, the reject heat available form the engine is sufficient to drive sorption refrigeration systems and satisfy most of the refrigeration requirements of the vehicle. Other promising technologies that can lead to a reduction in CO₂ emissions are air cycle refrigeration and hybrid systems in which conventional refrigeration technologies are integrated with thermal energy storage. For these systems, however, to effectively compete with diesel driven vapour compression systems, further research and development work is needed to improve their efficiency and reduce their weight.     

Multi-objective optimisation of renewable energy systems for pollution mitigation – a case study of Kavaratti Island,India

Islands represent a unique challenge in terms of electrical energy supply. A great deal of work has been carried out on this specific aspect of energy supply on different islands in the world. Unfortunately, due to island-specific energy usage profile, resources and different kinds of environmental conditions, a study of one island cannot be easily extended to other islands. The Lakshadweep group of islands in the Arabian Sea is one of the two major groups of islands in India having diesel generators (DGs) as the main source of electricity. Considering the remoteness of the island and the polluting nature of existing DGs, it is desirable to adopt a strategy to utilise the available potential of non-polluting renewable energy sources (RESs) for these ecologically sensitive islands. A multi-objective optimisation methodology is applied in Kavaratti Island, Lakshadweep, where various RESs exist and can be exploited to generate electrical energy and to mitigate environmental pollution. A specific mathematical model is developed with two objective functions, namely cost and environmental pollution that work reversibly. Application of the proposed mathematical tool leads to a Pareto set, satisfying the multiplicity of criteria, namely environmental pollution, energy demand, per-unit generation cost and resource constraints.     

H2RES,Energy planning tool for island energy systems – The case of the Island of Mljet

When it comes to the energy planning, computer programs like H₂RES are becoming valuable tools. H₂RES has been designed as support for simulation of different scenarios devised by RenewIsland methodology with specific purpose to increase integration of renewable sources and hydrogen into island energy systems. The model can use wind, solar, hydro, biomass, geothermal as renewable energy sources and fossil fuel blocks and grid connection with mainland as back up. The load in the model can be represented by hourly and deferrable electricity loads of the power system, by hourly heat load, by hydrogen load for transport and by water load depending on water consumption. The H₂RES model also has ability to integrate different storages into island energy system in order to increase the penetration of intermittent renewable energy sources or to achieve a 100% renewable island. Energy storages could vary from hydrogen loop (fuel cell, electrolyser and hydrogen storage) to reversible hydro or batteries for smaller energy systems. The H₂RES model was tested on the power system of the Island of Porto Santo – Madeira, the islands of Corvo, Graciosa, and Terrciera – Azores, Sal Island – Cape Verde, Portugal, the Island of Mljet, Croatia and on the energy system of the Malta. Beside energy planning of the islands, H₂RES model could be successfully applied for simulation of other energy systems like villages in mountain regions or for simulation of different individual energy producers or consumers.     

An assessment on the planning and construction of an island renewable energy system – A case study of Kinmen Island

During the last 50 years, Kinmen's economy has gone from military-based to increasingly tourism-based, Kinmen has been putting various constructions into action, and hence, the demand for electricity supply is getting higher relatively while the province is pushing various constructions. Nowadays, Kinmen County Government has made directions for future developments already and kept on promoting the sustainable development of Kinmen Island in order to make it a suitable place for living. According to the development blueprint, the future resident population will increase to around 150 ～ 200 thousand people so the relative electricity consumption in Kinmen Island will cause serious problems for Taipower in addition to large scale environmental pollution. The present study researches on both the limitation and independence of this particular island and presumes the electricity power supply will be provided through renewable energy sources, such as solar energy, wind energy, and tidal power generation and so on, whereby it will achieve the target of energy saving and carbon reduction successfully soon. Upon the construction process of the renewable energy sources, this study will simultaneously assess the eco-environment and social conditions on the island to evaluate the feasibility of existing renewable energy technologies which are more mature and determine the optimum renewable energy system that shall be constructed in the Kinmen region in the near future, in order to replace traditional energy sources. Meanwhile, it will assist the related energy industries to create an ultra-clean environment in Kinmen with self-developing power and enhance international competition forces so as to establish a positive international image of environmental protection by achieving a habitat with energy self-sufficiency, and ultimately the empirical model can be duplicated and promoted to other islands.     

Combustion chemistry and flame structure of furan group biofuels using molecular-beam mass spectrometry and gas chromatography – Part III: 2,5-Dimethylfuran

This work is the third part of a study focusing on the combustion chemistry and flame structure of furan and selected alkylated derivatives, i.e. furan in Part I, 2-methylfuran (MF) in Part II, and 2,5-dimethylfuran (DMF) in the present work. Two premixed low-pressure (20 and 40 mbar) flat argon-diluted (50%) flames of DMF were studied with electron–ionization molecular-beam mass spectrometry (EI-MBMS) and gas chromatography (GC) under two equivalence ratios (? = 1.0 and 1.7). Mole fractions of reactants, products, and stable and radical intermediates were measured as a function of the distance to the burner. Kinetic modeling was performed using a reaction mechanism that was further developed in the present series, including Part I and Part II. A reasonable agreement between the present experimental results and the simulation is observed. The main reaction pathways of DMF consumption were derived from a reaction flow analysis. Also, a comparison of the key features for the three flames is presented, as well as a comparison between these flames of furanic compounds and those of other fuels. An a priori surprising ability of DMF to form soot precursors (e.g. 1,3-cyclopentadiene or benzene) compared to less substituted furans and to other fuels has been experimentally observed and is well explained in the model.     

Experimental study of an air-source heat pump for simultaneous heating and cooling – Part 1: Basic concepts and performance verification

This article presents the concepts of an air-source heat pump for simultaneous heating and cooling (HPS) designed for hotels and smaller residential, commercial and office buildings in which simultaneous needs in heating and cooling are frequent. The main advantage of the HPS is to carry out simultaneously space heating and space cooling with the same energy input. Ambient air is used as a balancing source to run a heating or a cooling mode. The second advantage is that, during winter, energy recovered by the subcooling of the refrigerant is stored at first in a water tank and used subsequently as a cold source at the water evaporator to improve the average performance and to carry out defrosting of the air evaporator using a two-phase thermosiphon. Unlike conventional air-source heat pumps, defrosting is carried out without stopping the heat production. A R407C HPS prototype was built and tested. Its performance on defined operating conditions corresponds to the data given by the selection software of the compressor manufacturer. The operation of the high pressure control system, the transitions between heating, cooling and simultaneous modes and the defrosting sequence were validated experimentally and are presented in the second part of this article [1].     

Economic impact of performances degradation on the competitiveness of energy storage technologies – Part 1: Introduction to the simulation-optimization platform ODYSSEY and elements of validation on a PV-hydrogen hybrid system

In this paper, a newly developed assessment platform Odyssey is introduced. This platform is dedicated to perform comprehensive techno-economic assessments of energy systems comprising renewable energy sources and energy storage units. The major strengths of this platform are described and it is then illustrated on an application example with the objective to provide elements of validation of the platform. This application case is related to the electrical energy supply of a weather station by the mean of a PV-hydrogen hybrid energy system combining PV modules and a hydrogen chain. Experimental results obtained on the fuel cell and electrolyser systems are confronted to simulation results.     

A one-dimensional,two-phase model for direct methanol fuel cells – Part I: Model development and parametric study

A one-dimensional, steady-state, two-phase direct methanol fuel cell (DMFC) model is developed to precisely investigate complex physiochemical phenomena inside DMFCs. In this model, two-phase species transport through the porous components of a DMFC is formulated based on Maxwell–Stefan multi-component diffusion equations, while capillary-induced liquid flow in the porous media is described by Darcy's equation. In addition, the model fully accounts for water and methanol crossover through the membrane, which is driven by the effects of electro-osmotic drag, diffusion, and the hydraulic pressure gradient. The developed model is validated against readily available experimental data in the literature. Then, a parametric study is carried out to investigate the effects of the operating temperature, methanol feed concentration, and properties of the backing layer. The results of the numerical simulation clarify the detailed influence of these key designs and operating parameters on the methanol crossover rate as well as cell performance and efficiency. The results emphasize that the material properties and design of the anode backing layer play a critical role in the use of highly concentrated methanol fuel in DMFCs. The present study forms a theoretical background for optimizing the DMFC's components and operating conditions.     

Synergies of carbon neutrality,air pollution control,and health improvement——a case study of China Energy Interconnection scenario

Climate change and air pollution are primarily caused by the combustion and utilization of fossil fuels.Both climate change and air pollution cause health problems.Based on the development of China,it is extremely important to explore the synergies of the energy transition,CO₂ reduction,air pollution control,and health improvement under the target of carbon peaking before 2030 and carbon neutrality before 2060.This study introduces the policy evolution and research progress related to...