THE EARLY DESIGN MODEL FOR PREDICTION OF ENERGY AND COST PERFORMANCE OF BUILDING DESIGN OPTIONS

In order to encourage the use of computer modelling in building environmental analysis, it is necessary to provide a model developed from the designer's point of view. Detailed simulation models require a high degree of expertise and familiarity, further, there is also a need for detailed information not available in the early stages of the design process. Simplified models play an important role in the early stages of a design to achieve an integrated design: firstly, they are easy to use and, secondly, they require information easily available at the start of a design. In the Early Design Model (EDM) the solar gain utilisation factor has been determined as a continuous function of thermal mass. The differences between the annual energy predictions of EDM and SERI-RES ranges from 0.1% to 4.6% for time constants ranging from 378 to 2.52 h. The differences between the two sets of predictions on monthly basis ranges from ?3.6% to ?6.48% (EDM's predictions being larger) during the heating season, and from +2.86% to a maximum of +51% (EDM's predictions being smaller) in the remaining part of the year. In addition to energy predictions, EDM incorporates a facility which gives cost indications.     

Evaluation and analysis of a proxy indicator for the estimation of gate-to-gate energy consumption in the early process design phases: The case of organic solvent production

Gate-to-gate process energy consumption is an important metric for sustainability as it affects both costs and environmental impact. As only little process information is available in early phases of chemical process design, a detailed energy consumption calculation is substantially restrained. Therefore, a reliable estimation of energy consumption in early phases of process design is an important alternative. In this work, an index representing process energy consumption was evaluated and tested for 14 organic solvent case studies. By using simplified process models the indices were calculated and compared to literature values for gate-to-gate energy consumption. The predictability of the process energy consumption on the basis of this indicator, including possible modifications in its original definition, was evaluated with the Pearson's and Spearman's correlation coefficients. The results further validated the use of the EI (energy index) in its original form as a proxy indicator of the process energy consumption for decision making in early stages of process design. For assessing the production of new classes of chemicals the EI should be evaluated as shown in this paper in order to establish its practicability. In certain cases an adjustment of the indicator categories may be necessary.     

Optimum thermal design of office buildings

Proper design and selection of building components at the early stages of the design process can greatly help in achieving thermal comfort with minimum reliance upon HVAC systems and, therefore, minimum energy requirements. Given today's complexities in building design as well as advances in computer technology, optimization techniques can be used as an aid to building designers in their decision making process. Office buildings are characterized by being ‘internal-load’ dominated with internal heat generation determining the need for energy to air-condition such buildings. This paper presents the results of applying an optimization model to the design of energy conserving office buildings in different climatic regions to test the impact of mainly envelope related parameters on the thermal performance of offices. Optimum sets of building design variables for three different sizes office building in four U.S. and two Saudi Arabian cities are presented with the objective of minimizing annual energy consumption for those buildings. © 1997 John Wiley & Sons, Ltd.     

Multi-scale model based design of membrane reactor/separator processes for intensified hydrogen production through the water gas shift reaction

This work aims to first quantify the impact of various diffusion models (Maxwell-Stefan, Wilke, Dusty-Gas) on the predictions of a multi-scale membrane reactor/separator mathematical model, and to then demonstrate this model's use for the design and process intensification of membrane reactor/separator systems for hydrogen production. This multi-scale model captures velocity, temperature and species' concentration profiles along the catalyst pellet's radial direction, and along the reactor's axial direction, by solving the momentum, energy, and species transport equations, accounting for convection, conduction, reaction, and diffusion mechanisms. In the first part of work, the effect of pellet-scale design parameters (mean pore diameter, volumetric porosity, tortuosity factor, etc.) and various species' flux models on the model predictions is studied. In the second part, the study focuses on the comparison, in terms of their process intensification characteristics, of various hydrogen production processes. These include a conventional high-temperature shift reactor (HTSR)/low-temperature shift reactor (LTSR) sequence, a novel HTSR/membrane separator (MS)/LTSR/MS sequence, and a process that involves low-temperature shift membrane reactors-LTSMR in a series.     

Comparative study of various correlations in estimating hourly diffuse fraction of global solar radiation

Proper design and performance predictions of solar energy systems require accurate information on the availability of solar radiation. The diffuse-to-global solar radiation correlation, originally developed by Liu and Jordan, has been extensively used as the technique providing accurate results, although it is latitude dependent. Thus, in the present study, empirical correlations of this type were developed to establish a relationship between the hourly diffuse fraction (k_d) and the hourly clearness index (k_t) using hourly global and diffuse irradiation measurements on a horizontal surface performed at Athalassa, Cyprus. The proposed correlations were compared against 10 models available in the literature in terms of the widely used statistical indicators, rmse, mbe and t test. From this analysis, it can be concluded that the proposed yearly correlation predicts diffuse values accurately, whereas all candidate models examined appear to be location-independent for diffuse irradiation predictions.     

A review of wind energy technologies

Energy is an essential ingredient of socio-economic development and economic growth. Renewable energy sources like wind energy is indigenous and can help in reducing the dependency on fossil fuels. Wind is the indirect form of solar energy and is always being replenished by the sun. Wind is caused by differential heating of the earth's surface by the sun. It has been estimated that roughly 10 million MW of energy are continuously available in the earth's wind. Wind energy provides a variable and environmental friendly option and national energy security at a time when decreasing global reserves of fossil fuels threatens the long-term sustainability of global economy. This paper reviews the wind resources assessment models, site selection models and aerodynamic models including wake effect. The different existing performance and reliability evaluation models, various problems related to wind turbine components (blade, gearbox, generator and transformer) and grid for wind energy system have been discussed. This paper also reviews different techniques and loads for design, control systems and economics of wind energy conversion system.     

Reevaluation of Turkey's hydropower potential and electric energy demand

This paper deals with Turkey's hydropower potential and its long-term electric energy demand predictions. In the paper, at first, Turkey's energy sources are briefly reviewed. Then, hydropower potential is analyzed and it has been concluded that Turkey's annual economically feasible hydropower potential is about 188 TWh, nearly 47% greater than the previous estimation figures of 128 TWh. A review on previous prediction models for Turkey's long-term electric energy demand is presented. In order to predict the future demand, new increment ratio scenarios, which depend on both observed data and future predictions of population, energy consumption per capita and total energy consumption, are developed. The results of 11 prediction models are compared and analyzed. It is concluded that Turkey's annual electric energy demand predictions in 2010, 2015 and 2020 vary between 222 and 242 (average 233) TWh; 302 and 356 (average 334) TWh; and 440 and 514 (average 476) TWh, respectively. A discussion on the role of hydropower in meeting long-term demand is also included in the paper and it has been predicted that hydropower can meet 25–35% of Turkey's electric energy demand in 2020.     

Simple equations to correlate theoretical stages and operating reflux in fractionators

Natural gas is an important source of primary energy. Virtually all gas processing plants producing natural gas liquids require at least one fractionator to produce a liquid product which can meet sales specifications. Fractionation is one of the pivotal unit operations in refineries, gas processing and other industries utilized to separate mixtures into individual products. However, it is capital and energy intensive and, with decreasing relative volatility, the size and energy requirements of a column tend to increase. The primary parameters involved in the design of fractionators are the number of stages and the reflux ratio. The aim of this study is to develop easy-to-use equations, which are simpler than current available models involving a large number of parameters and requiring more complicated and longer computations, for an appropriate prediction the operating reflux ratio for a given number of stages. Alternatively, for a given reflux ratio, number of stages can be determined. The accuracy of the proposed equations was tested and found to be in excellent agreement with the reported data for the wide range of conditions, wherein the average absolute deviation percent of proposed equations being 1.5%. These simple-to-use equations can be of immense practical value for the engineers. In particular, process engineers would find the proposed approach to be user friendly involving no complex expressions with transparent calculations.     

Estimating operating cell temperature of BIPV modules in Thailand

Several models have been developed to estimate the operating cell temperatures of photovoltaic (PV) modules because they directly affect the performance of each PV module. In this study, two prediction models used most commonly, the nominal operating cell temperature (NOCT) model and the Sandia National Laboratory temperature prediction model (SNL), were investigated for their suitability in the prediction of PV module's temperatures for building integrated photovoltaic (BIPV) installation in the tropical climate conditions of Thailand. It was found that, in general, the SNL model tends to give better results of temperature prediction than those of the NOCT model. Nevertheless, both models are strongly over-biased in temperature predictions. The discrepancies of the predictions are basically caused by the dissimilarity of the BIPV installation and the standard installation as specified by the models, rather than the effect of differences in climatic conditions between the temperate and tropical zones. In the worst case, it was found that the highest value of the mean bias error (MBE) is +8 °C, or equivalent to +21% of the mean observed temperature, and the root mean square error (RMSE) is ±10 °C, or equivalent to ±24% of the mean observed temperature. However, although these errors were large, their effects on the accuracy of the final prediction of the electrical power output generated by the PV module over a long term would not be great. The error of the expected generated energy output would not be more than 6% of the averaged actual energy output, which is acceptable for most applications.     

Smart energy storage management via information systems design

Enabled by smart meters and Internet of Things (IoTs) technologies, we are now able to harness information systems and automatize the management of energy storages. Motivated by applications such as renewables integration and electrification of transportation, the paradigm shift towards smart-cities naturally inspires information systems design for energy storages. The goal of this paper is to understand the economic value of future market information to increase the efficiency of the energy market. From storages’ perspective, we investigate energy storages’ optimal decentralized buying and selling decisions under market uncertainty. Different potential policy interventions are discussed: (1) providing a publicly available market forecasting channel; (2) encouraging decentralized storages to share their private forecasts with each other; (3) releasing additional market information to a targeted subset of storages exclusively. Through these system level discussions, we evaluate different information management policies to coordinate storages’ actions and improve their profitability. The key findings of this work include (1) a storage's payoff first increases then decreases in its private information precision. The over-precision in forecasts can lead to even lower payoffs; (2) communication among the storages could fail to achieve a coordinated effort to increase market efficiency; (3) it is optimal to release additional information to a subset of energy storages exclusively by targeted information release.     

Simple tool to evaluate energy demand and indoor environment in the early stages of building design

A simplified building simulation tool to evaluate energy demand and thermal indoor environment in the early stages of building design is presented. Simulation is performed based on few input data describing the building design, HVAC systems and control strategies. Hourly values for energy demand and indoor temperature are calculated based on hourly weather data. Calculation of the solar energy transmitted through windows takes into account the dependency of the total solar energy transmittances on the incidence angle, shades from far objects and shades from the window recess and overhangs. Several systems including heating, cooling, solar shading, venting, ventilation with heat recovery and variable insulation can be activated to control the indoor temperature and energy demand. Predicted percentages of dissatisfied occupants are calculated for a given time period to support decisions concerning the thermal indoor environment. The simplified building simulation tool gives reliable results compared to detailed tools and needs only few input data to perform a simulation. The tool is therefore useful for preliminary design tasks in the early design stages where rough estimates of the building design are given and rough estimates of energy use and thermal indoor environment are needed for decision support.     

Method for simulating predictive control of building systems operation in the early stages of building design

A method for simulating predictive control of building systems operation in the early stages of building design is presented. The method uses building simulation based on weather forecasts to predict whether there is a future heating or cooling requirement. This information enables the thermal control systems of the building to respond proactively to keep the operational temperature within the thermal comfort range with the minimum use of energy. The method is implemented in an existing building simulation tool designed to inform decisions in the early stages of building design through parametric analysis. This enables building designers to predict the performance of the method and include it as a part of the solution space. The method furthermore facilitates the task of configuring appropriate building systems control schemes in the tool, and it eliminates time consuming manual reconfiguration when making parametric analysis. A test case featuring an office located in Copenhagen, Denmark, indicates that the method has a potential to save energy and improve thermal comfort compared to more conventional systems control. Further investigations of this potential and the general performance of the method are, however, needed before implementing it in a real building design.     

Design concepts of hydrogen supply chain to bring consumers offshore green hydrogen

This study presents design concepts for hydrogen supply chains as a way to investigate how to transport green hydrogen from offshore sites to onshore sites where it would be available to consumers. The six concepts suggested are based on compressed hydrogen, a pipeline, liquefied hydrogen, liquid organic hydrogen carriers (LOHC), ammonia, and a subsea cable. Most of the concepts transported the hydrogen from production to consumption sites, but in the case of the subsea cable transferred electricity from the offshore wind farm. All the design concept were created to satisfy the same specific case study. For this case study, the East Sea was selected as the hydrogen production site, Busan port was chosen as the hydrogen consumption site. The six concepts were applied to the suggested case study before being compared from the viewpoint of each system's complexity. The results show that the pipeline- and subsea cable-based hydrogen supply chains are relatively simple relative to the other concepts, the LOHC- and ammonia-based hydrogen supply chains are inherently more complex because they require de-hydrogenation and cracking processes to extract hydrogen from the LOHC and ammonia. On the other hand, ammonia and liquefied hydrogen have advantages in terms of ship transportation because they both provide high volumetric densities. In the case of ammonia, the infrastructure required would be significantly reduced if it could be directly used as a fuel without the cracking and purification processes. This study proposes and compares various hydrogen supply chain concepts with the goal that the results will prove helpful to those attempting to create an offshore hydrogen supply chain by providing fundamental data to decision-makers in the early design stages.     

TRANSIENT THERMAL STRESSES IN A THIN ELASTIC PLATE DUE TO A RAPID DUAL-PHASE-LAG HEATING

Thermal stresses generated within a thin plate as a result of a fast heating rate are investigated numerically using the dual-phase-lag heat conduction model. The quantitative and qualitative predictions of the dual-phase-lag model for the thermal stresses are compared with the predictions of the diffusion (parabolic) and wave (hyperbolic) heat conduction models. It is found that the predictions of the three models differ in the early stages of the heating process and then give almost the same predictions as they approach the steady-state limit.     

Experimental study of distribution of energy during EDM process for utilization in thermal models

Electrical discharge machining (EDM) has steadily gained importance over the years because of its ability to cut and shape a wide variety of materials and complicated shapes with high accuracy. The effectiveness of the EDM process is evaluated in terms of the material removal rate, relative wear ratio and the surface roughness of the work piece. The input discharge energy during this process is distributed to various components of the process, which further influences the material removal rate and other machining characteristics like surface roughness. Since during this process the electrical energy is converted into heat energy, hence the theoretical modeling of this process is based upon the heat transfer equations and in all existing thermal models the fraction of the energy transferred to the workpiece, is one of the important parameters. The accurate prediction of the fraction of energy effectively transferred to the workpiece will help to reduce the errors of the thermal models. In this study experiments have been performed to study the percentage fraction of energy transferred to the workpiece utilizing heat transfer equations, at different EDM parameters. This study also relates the optimum parameters with the optimum utilization of input discharge energy and hence will help to improve the technological performance of this process.     

Structural design of spars for 100-m biplane wind turbine blades

Large wind turbine blades are being developed at lengths of 75–100 m, in order to improve energy capture and reduce the cost of wind energy. Bending loads in the inboard region of the blade make large blade development challenging. The “biplane blade” design was proposed to use a biplane inboard region to improve the design of the inboard region and improve overall performance of large blades. This paper focuses on the design of the internal “biplane spar” structure for 100-m biplane blades. Several spars were designed to approximate the Sandia SNL100-00 blade (“monoplane spar”) and the biplane blade (“biplane spar”). Analytical and computational models are developed to analyze these spars. The analytical model used the method of minimum total potential energy; the computational model used beam finite elements with cross-sectional analysis. Simple load cases were applied to each spar and their deflections, bending moments, axial forces, and stresses were compared. Similar performance trends are identified with both the analytical and computational models. An approximate buckling analysis shows that compressive loads in the inboard biplane region do not exceed buckling loads. A parametric analysis shows biplane spar configurations have 25–35% smaller tip deflections and 75% smaller maximum root bending moments than monoplane spars of the same length and mass per unit span. Root bending moments in the biplane spar are largely relieved by axial forces in the biplane region, which are not significant in the monoplane spar. The benefits for the inboard region could lead to weight reductions in wind turbine blades. Innovations that create lighter blades can make large blades a reality, suggesting that the biplane blade may be an attractive design for large (100-m) blades.     

Combining simulation techniques and design expertise in a renewable energy system design package, RESSAD

Computer simulation is an increasingly popular tool for determining the most suitable renewable energy system type, design and control for an isolated community or homestead. However for the user without any expertise in system design, the complicated process of system component and control selection using computer simulation takes on a trial and error approach. Our renewable energy system design package, RESSAD, has been developed to simulate a wide range of renewable power supply systems, and to go beyond system simulation, by combining design expertise with the simulation model. The knowledge of the system designer is incorporated into the package through a range of analysis tools that assist in the selection process, without removing or restricting individual choices. The system selection process is analysed from the early stages of renewable resource assessment to the final evaluation of the results from a simulation of the chosen system. The approach of the RESSAD package in this selection process is described and its use is illustrated by two case studies in Western Australia.     

Solar energy integration into advanced building design for meeting energy demand and environment problem

The dangerous effects of burning fossil fuels on global warming, alternative energy sources will become indeed important in the future. Because of fossil fuels energy sources shall run out by the early 22nd century given the present rate of consumption. Atmospheric concentration of greenhouse gases is trapping heat radiated from the Earth's surface, which cause global warming and environmental problems such as greenhouses effect, stratospheric ozone depletion, acid precipitation, and flooding of coastal settlements. This implies that sooner or later humanity will rely heavily on renewable energy sources. Here we have introduced light energy at an idealized large‐scale application to produce solar energy, where exterior skin and roof of buildings shall be at least 25% blackbody‐assisted photovoltaic to capture solar energy during the whole year. Simply, it is a calculative reaction of solar irradiance on innovative building design to capture sunlight most efficiently that would be the cutting edge technology for the ultimate solution of global energy, environment, and climate crisis. Copyright © 2016 John Wiley & Sons, Ltd.     

Insights on performance and an improved model for full scale electrolysers based on plant data for design and operation of hydrogen production

Developers and operators of energy systems based on renewable energy require effective models of these systems, including those with hydrogen storage where electrolysers are critical components. However, electrolyser models are often either too detailed to be computationally efficient within whole system model, or too inaccurate at times of low production of renewable energy. Our novel model addresses this by combining the Tafel equation and an original model for Faradaic efficiency. It was validated and tested on plant data from the 250 kW electrolyser at Bright Green Hydrogen's Levenmouth Community Energy Project in Methil, Scotland. The model estimated hydrogen consumption more accurately than the ‘Linear Model’ habitually used in industry. Our data also emphasized the importance of an optimised control scheme for minimizing hot standby losses. Pressurisation during start-up, purging and pressure-driven fluctuations also contributed significant losses and scatter when inspecting minute-by-minute data. This knowledge should inform whole system analysis and control.     

Marine current energy resource assessment and design of a marine current turbine for Fiji

Pacific Island Countries (PICs) have a huge potential for renewable energy to cater for their energy needs. Marine current energy is a reliable and clean energy source. Many marine current streams are available in Fiji's waters and large amount of marine current energy can be extracted using turbines. Horizontal axis marine current turbine (HAMCT) can be used to extract marine current energy to electrical energy for commercial use. For designing a HAMCT, marine current resource assessment needs to done. A potential site was identified and resource assessment was done for 3 months. The coordinates for the location are 18°12′1.78″S and 177°38′58.21″E; this location is called Gun-barrel passage. The average depth is 17.5 m and the width is nearly 20 m – the distance from land to the location is about 500 m. A multi cell aquadopp current profiler (ADCP) was deployed at the site to record marine currents. Strong marine currents are recorded at this location, as a combination of both tidal and rip currents. The maximum current velocity exceeds 2.5 m/s, for days with large waves. The average velocity was 0.85 m/s and power density for the site was 525 W/m². This site has good potential for marine current and HAMCT can be installed to extract power. A turbine with diameter between 5 and 8 m would be suitable for this site. Therefore, a 5 m HAMCT is designed for this location. The HF10XX hydrofoils were used from blade root (r/R = 0.2) to tip (r/R = 1.0). HF10XX series hydrofoil sections were designed to operate at varying turbine operating conditions; these hydrofoils have good hydrodynamic characteristics at the operating Reynolds number. The turbine is designed to operate at rated marine current speed of 1.5 m/s, cut in speed of 0.5 m/s and cut off speed of 3 m/s at a tip speed ratio (TSR) of 4.2.