The deviatoric map—a simple tool in design by analysis

The usage of the deviatoric map as a tool in the visualization of structural behavior under the influence of multiple actions or repeatedly applied actions is shown. Special emphasis is given to its usage in shakedown checks.     

COSSOR—a transient simulation program for a solid absorption solar refrigerator

An algorithm for the computer simulation of a solid absorption solar refrigerator, COSSOR, is presented. The algorithm is based on a detailed transient mathematical model of the system. It is a sequential modular program which consists of a relatively short main program and about 50 subprograms which are called by name by the main program or other subprograms. The program is coded in QBASIC, is highly flexible, accurate and fast, and has been tested on a wide variety of personal computers. Predictions of the refrigerator performance obtained using COSSOR compare very well with experimental data over a wide range of operating conditions. It is therefore a useful tool for computer aided design, performance prediction and analysis of the refrigerator, and may find applications in other solar thermal systems. Typical predicted results for some stations are given.     

A flexible techno-economic analysis tool for regional hydrogen hubs – A case study for Ireland

The increasing urgency with which climate change must be addressed has led to an unprecedented level of interest in hydrogen as a clean energy carrier. Much of the analysis of hydrogen until this point has focused predominantly on hydrogen production. This paper aims to address this by developing a flexible techno-economic analysis (TEA) tool that can be used to evaluate the potential of future scenarios where hydrogen is produced, stored, and distributed within a region. The tool takes a full year of hourly data for renewables availability and dispatch down (the sum of curtailment and constraint), wholesale electricity market prices, and hydrogen demand, as well as other user-defined inputs, and sizes electrolyser capacity in order to minimise cost. The model is applied to a number of case studies on the island of Ireland, which includes Ireland and Northern Ireland. For the scenarios analysed, the overall LCOH ranges from €2.75–3.95/kgH₂. Higher costs for scenarios without access to geological storage indicate the importance of cost-effective storage to allow flexible hydrogen production to reduce electricity costs whilst consistently meeting a set demand.     

Electrochemical impedance spectroscopy analysis of V–I characteristics and a fast prediction model for PEM-based electrolytic air dehumidification

PEM-based electrolytic air dehumidification is innovative due to its high efficiency, compact size and cleanness. However, high polarization loss and severe performance degradation have been observed, especially at high applied voltages (>2.5 V). Understanding the V–I characteristics is critical to performance optimization. This study experimentally investigated the V–I characteristics and internal response of materials under various operating conditions, with in-situ Electrochemical Impedance Spectroscopy (EIS) methods. Real-time mass transfer, electrochemical polarization and reaction dynamics of PEM components during dehumidification were derived by EIS. Then, a fast prediction model was built to directly predict the dehumidification rate and attenuation without any iteration, suitable for online monitoring and adjustment. Compared to other models, this model can take a quick understanding of the impact of operating conditions on the material characteristics inside the PEM element. The deviations of current density, PEM proton conductivity and moisture removal were 3%, 11.2% and 15.3%, respectively, compared to experiment data. Results showed that when the applied voltage changed from 1.5 to 3.5 V, the high-frequency resistance of the PEM element increased from 1.69 to 2.69 Ω, and the PEM proton conductivity decreased by about 38 times. The sharp drop in PEM proton conductivity resulted in a current attenuation. With this model, requirements for key components of PEM dehumidification were also obtained. Analysis of the overpotential distribution showed that increasing the water retention and reducing the dependence of proton conductivity on water molecules of the PEM can effectively improve the performance. This research provides guidance for the performance optimization and material selection of PEM-based dehumidification.     

Advanced control systems engineering for energy and comfort management in a building environment—A review

Given restrictions that comfort conditions in the interior of a building are satisfied, it becomes obvious that the problem of energy conservation is a multidimensional one. Scientists from a variety of fields have been working on this problem for a few decades now; however, essentially it remains an open issue. In the beginning of this article, we define the whole problem in which the topics are: energy, comfort and control. Next, we briefly present the conventional control systems in buildings and their advantages and disadvantage. We will also see how the development of intelligent control systems has improved the efficiency of control systems for the management of indoor environment including user preferences. This paper presents a survey exploring state of the art control systems in buildings. Attention will be focused on the design of agent-based intelligent control systems in building environments. In particular, this paper presents a multi-agent control system (MACS). This advanced control system is simulated using TRNSYS/MATLAB. The simulation results show that the MACS successfully manage the user’s preferences for thermal and illuminance comfort, indoor air quality and energy conservation.     

ANN–supported control strategy for a solid oxide fuel cell working on demand for a public utility building

The idea of control strategy of SOFC operating to meet demand of a public utility building was presented. The strategy was formulated with the support of Artificial Neural Network. The network was used to predict the demand for electricity. The calculations were carried out on the example of a building of the Institute of Heat Engineering Warsaw University of Technology. The control strategy is influenced by various factors depending on changes in market conditions and operating characteristics of the cell. We can define different objective functions eg: working for own needs, for maximum profit and maximum service life. The article presents a simulation of SOFC operation for demand profile of the IHE building from the selected time period.     

SHAM—a simulation model for designing straw fuel delivery systems. Part 1: model description

Straw is a renewable biomass that has a large potential as an energy resource in Sweden. The costs for harvest, transport and storage of this bulky fuel are, however, high, because it is produced over large areas and must be collected during a limited amount of days into intermediate storages before being ultimately transported to heating plants. This paper presents a dynamic simulation model for analysis of various delivery alternatives in order to improve and optimize system performance and to reduce the costs and energy needed in straw handling. The model, called SHAM (Straw HAndling Model), is based on submodels associated with infrastructural and geographical aspects, as well as with field drying and weather conditions. A simplified empirical field drying model has been developed, which is used to predict the straw moisture content at any time. The harvesting seasons can be simulated to compare different machinery chains, management strategies and plant locations. A large number of system performance measures can be studied, for example, utilization times of machinery, the time the straw has to wait for different resources, and the amount of straw that the machines are able to harvest per season. The validity of SHAM has been established by comparisons with existing harvesting systems.     

SHAM—a simulation model for designing straw fuel delivery systems. Part 2: model applications

A dynamic simulation model for designing straw fuel delivery systems, called SHAM (Straw HAndling Model), has been used to evaluate the performance, costs and energy needs of various straw handling systems. The prerequisites of straw harvest were investigated for three Swedish regions with different climatic and geographical conditions. As a fuel in district heating plants, the simulations showed that straw has the best opportunity of becoming economically competitive in agricultural districts in south Sweden. The simulations demonstrated, however, that the costs can be lowered and the system performance increased for these places by using appropriate management strategies. SHAM was also used to determine the number of machines in the handling operations in order to minimize the total fuel costs for a straw- and oil-fired district heating plant. The optimizations showed that straw can be delivered to the plant at a cost of 29.9 SEK GJ⁻¹. Finally, two alternatives to the conventional high-density baler systems were evaluated; systems based on compact rolls and systems based on chopped straw stored outdoors. It was demonstrated that these technologies cost about 5–20% more compared with high-density bales. However, their prospects of becoming competitive harvest methods for the future are good.     

Feedback on household electricity consumption: a tool for saving energy?

Improved feedback on electricity consumption may provide a tool for customers to better control their consumption and ultimately save energy. This paper asks which kind of feedback is most successful. For this purpose, a psychological model is presented that illustrates how and why feedback works. Relevant features of feedback are identified that may determine its effectiveness: frequency, duration, content, breakdown, medium and way of presentation, comparisons, and combination with other instruments. The paper continues with an analysis of international experience in order to find empirical evidence for which kinds of feedback work best. In spite of considerable data restraints and research gaps, there is some indication that the most successful feedback combines the following features: it is given frequently and over a long time, provides an appliance-specific breakdown, is presented in a clear and appealing way, and uses computerized and interactive tools.

Assessing a regional building applied PV potential – Spatial and dynamic analysis of supply and load matching

Electricity production by PV is growing world-wide, and grid parity of PV-electricity can be found in many countries, even in low sunlight countries, such as Sweden (at latitude 58°). High installation-rate of PV-systems poses a challenge to the grid-operator. Building-integrated PV-supply potential analysis was performed for Linköping municipality in Sweden based on GIS-data for all the buildings in the municipality. The Linköping model provides a high spatial resolution (>180 000 buildings). The data are sorted based on azimuth and tilt, categorized in steps of 10°, and then used to construct hourly power supply data. The supply data are fed into the existing electricity load-profile of Linköping municipality. The strength and novelty of the method is that it provides the possibility of varying the installation-rate in different spatial directions to better match the load-profile.The results indicate a solar supply-rate of 19, 43 and 88% respectively if using the tilted roofs (>900 kWh/m² × yr), the flat-roofs optimized with tilted panels for a winter solar supply and the fully available PV-area on existing buildings (8.1 km²). Nevertheless, in approximately 70, 1400 and >3000 h/yr, respectively, surplus-power is created, which could be used to match a future load in a wider electro-mobility scenario.     

CO2 sorbents for a sorption-enhanced water–gas-shift process in IGCC plants: A thermodynamic analysis and process simulation study

A sorption-enhanced water–gas-shift reaction process (SEWGS) combines the WGS reaction and CO₂ removal into a single process step in an integrated gasification combined cycle (IGCC) power plant. In the SEWGS, a solid sorbent is employed to capture the CO₂ generated by the WGS reaction. A key technical issue for the SEWGS is to identify and develop sorbents that can capture CO₂ under high pressure and high temperature syngas conditions and minimize or even eliminate the need for WGS catalysts. We present the results from a thermodynamic analysis and process simulation study that aimed to identify sorbents and optimal temperature windows to maximize the thermal efficiency of an IGCC + SEWGS plant. The results from the thermodynamic analysis identified two metal oxides, one silicate, three zirconates, and one titanate sorbents that are suitable for the SEWGS application. The results from the process simulation study revealed that the overall thermal efficiency of a 1187 MW_th (thermal input) IGCC + SEWGS plant gasifying an Illinois coal, and using the seven sorbents selected from the thermodynamic analysis, was between 0.5 and 2.4 percentage points greater than that of a reference IGCC + Selexol plant.     

China’s rural electricity market—a quantitative analysis

The objective of this paper is to quantify the development of the rural electricity market at county level and below in China. A sectorial energy demand analysis and forecasting model was developed to analyze six Chinese provinces with different economic backgrounds. Historical data for over 20 years were collected on rural economic development, households, population, per capita income, community infrastructure development, capital investment, electricity consumption, output values in agriculture sector, and township and village enterprises (TVEs). This paper concludes that by 2010, annual electricity demand will increase at a rate between −1.40% and 15.60% (depending on the sectors and provinces). It also recommends a preferred order for future rural electricity investment: Jiangsu, Hebei, Henan, Shaanxi, Liaoning and Xinjiang, i.e. from the most to the least developed provinces, if the investment objectives are to find the best market return and the greatest impact on rural market development.     

Industrial waste heat potential in Germany—a bottom-up analysis

Industrial waste heat may be one of the answers to future energy demands. Depending on the temperature, industrial waste heat may be used to produce electricity or meet cooling or heating demands at different temperature levels. However, in order to estimate the influence the waste heat may have in future energy systems, the magnitude of the industrial waste heat in the different countries need to be estimated. For Germany, so far, only top-down analyses of the waste heat potential exist, using key figures derived from other studies in other countries. In this paper, the first bottom-up approach for estimating the industrial waste heat potential in Germany is presented. For this approach, an algorithm to evaluate and test the mandatory emission report data from German production companies was developed. In a second step, round about 81,000 data sets have been evaluated to calculate a conservative and lower boundary value for the industrial waste heat. As this conservative, lower boundary based on the collected data from the German industry, the waste heat volume was evaluated as 127 PJ/a or 13 % of the industrial fuel consumption. Results were used to derive key figures with which the missing share of the data was approximated.     

An all-condition simulation model of the steam turbine system for a 600 MW generation unit

Coal-fired generation units in China often operate under off-design loads. The off-design performance has important influence on operation energy consumption of generation units. An all-condition model is of critical importance for studying the off-design performance. In this paper, an all-condition simulation model of the steam turbine system for a 600 MW generation unit is built. Based on the actual system composition, the steam turbine system is divided into several sub equipment. A sub model is established for each device. In the turbine model, a parameter M is defined as the intermediate variable to calculate the extraction pressure of turbine. The operating data from a 600 MW generation unit are used to verify the all-condition model. The heater fouling conditions are also calculated. The result shows that the model successfully predicts the operation parameters under different loads and forecasts the thermal performance of typical equipment failure.     

Performance analysis of a waste heat driven activated carbon based composite adsorbent – Water adsorption chiller using simulation model

This study aims at improving the performance of a waste heat driven adsorption chiller by applying a novel composite adsorbent which is synthesized from activated carbon impregnated by soaking in sodium silicate solution and then in calcium chloride solution. Modeling is performed to analyze the influence of the hot water inlet temperature, cooling water inlet temperature, chilled water inlet temperatures, and adsorption/desorption cycle time on the specific cooling power (SCP) and coefficient of performance (COP) of the chiller system with the composite adsorbent. The simulation calculation indicates a COP value of 0.65 with a driving source temperature of 85 °C in combination with coolant inlet and chilled water inlet temperature of 30 °C and 14 °C, respectively. The most optimum adsorption–desorption cycle time is approximately 360 s based on the performance from COP and SCP. The delivered chilled water temperature is about 9 °C under these operating conditions, achieving a SCP of 380 W/kg.     

Electric ferry ecosystem for sustainable inter-island transport in the Philippines: a prospective simulation for Davao City – Samal Island Route

The development of a prospective simulation will serve as a guide in converting a diesel engine into 100% electric engine, this conversion will solve the problems facing nowadays in an energy crisis and greenhouse gas emission. The simulation derives the estimated power engine, the battery pack to be installed and the photovoltaic wattage for charging while transporting passengers and goods from Davao City to Samal Island Philippines. The results give an estimated power engine of 24.07?kW, 7.1?kA- hour battery bank and 64?kW of the photovoltaic module to charge the battery while on voyage. This study further helps the boat owner to find the suitable engine requirement in converting into the electric ferry. The prospective simulation is the stepping-stone in moving towards green energy source and electric mobilisation in the maritime sector.     

Irreversibility analysis for Casson thermo-fluidics inside a cone: Cattaneo–Christov heat flux

In this communication, thermodynamic irreversibility arising in dissipative Casson fluid flow inside a cone is investigated. The boundary–layer flow is considered wherein the motion is caused due to a point sink at the cone's vertex and the movement of the wall of the cone. The wall of the cone is subjected to mass transpiration that alters the flow and thermal regime. The cone having fluid-saturated porous medium experiences Cattaneo–Christov heat flux. The configuration admits a similarity transformation that yields a boundary value problem (BVP) comprising an ordinary differential equation. The BVP is treated by the fourth-order R-K method along with the shooting algorithm. The system yields a dual solution for momentum and energy, which gives rise to a dual regime for entropy distribution. Numerical computations provide quantities of interest viz. velocity and temperature distributions, skin friction coefficient, Nusselt number, and entropy distribution. Phenomena exhibited through profiles/tables for velocity, temperature, entropy, streamlines, and other quantities of interest reveal interesting results.     

Life cycle analysis of hydrogen – A well-to-wheels analysis for Portugal

A life cycle analysis of hydrogen is presented involving several processes of H₂ production. The main goal was to adapt the GREET 1.8c model in order to represent the European reality and more specifically the Portuguese energy sector. GEMIS model was used in order to obtain energy consumption and pollutant emissions related to the production of photovoltaic panels and wind towers, since GREET model consider zero emissions in renewable technologies. The integration between these two models generated MACV2H₂ model that was calibrated.     

Conductors crystallization—a condition for synthesizing new dopant compounds

We examine some possible cases of synthesizing new dopant compounds and their substitution solid solutions by growing crystal layers of Si, Ge, GaSb, CuInSe₂ and CdTe, which are of interest for investigating impurity voltaic effects.     

Nonlinear stability analysis and a new design methodology for a PEM fuel cell fed DC–DC boost converter

The dynamical behaviour of a fuel cell feeding a boost converter is studied in this paper. A nonlinear model of the combined system is derived including the effect of the switching action of the converter. Using Filippov's theory, it is possible to analytically study the bifurcation patterns of the system and to demonstrate that the system loses stability through a period doubling bifurcation. To overcome this instability, we inject a high frequency sinusoidal signal into the system that forces the system to remain stable while at the same time retaining its basic slow scale properties (like the steady state error). This controller is simple to implement and does not require any special hardware. The stability analysis and new controller design method presented in this paper allow for the re-design of the converter to stabilize circuit operation with a substantially reduced inductor size, reducing the size and cost of the converter while maintaining its average currents and voltages and other circuit steady-state behaviour characteristics. The results are confirmed by using numerical and analytical tools.