A model to design and optimize multi-energy systems in buildings at the design concept stage

Increasing interest is currently being addressed to multi-energy systems in buildings. These systems integrate different energy sources, at least one of which is renewable, in order to cover the thermal and electrical loads of a building. Since the design and operation of such systems are very complicated for many reasons (e.g. the intermittent nature of the renewable sources, the highly interlinked system layouts), it is of the foremost importance to provide tools to help select the best system configuration and energy sources mix.A modelling approach to multi-energy systems in buildings, based on the energy hub concept is presented in this work. This approach allows the coupling between the energy demand and the energy supply in a building to be modelled in a synthetic way. The model was customised to be used at the concept stage of the building design, either as a system simulation tool or as a system selection tool. If the prices and the characteristics of the energy converters and of the energy-wares are known, it is possible, with a certain set of constraints, to determine the configuration that minimises the initial investment costs, the use of non-renewable sources or the life-cycle costs. This approach makes it possible to avoid the simulation and ranking of a set of different system configurations, and also permits the study of the behaviour of such systems in an open configuration and not as individual systems. An application of the methodology to a case study is provided.     

Towards zero carbon design in offices: Integrating smart facades,ventilation, and surface heating and cooling

This paper discusses an overall strategy for reducing energy demand in non-domestic buildings, mainly focusing on office developments. It considers four areas: reducing internal heat loads; addressing passive design through the building construction; using efficient and responsive HVAC systems and focusing on chilled (heated) surface systems; integrating renewable energy supply systems into the building design. The impact on energy use and carbon dioxide emissions will be discussed. The paper will draw from a range of design projects carried out in Europe, where this integrated approach has been applied, and then explore the benefits in relation to applications in the Middle East and China. Energy modeling results, to inform the design process will be presented, using energy simulation for three case study locations, in Zurich, the Chongqing and Abu Dhabi.     

A comparative analysis for multiattribute selection among renewable energy alternatives using fuzzy axiomatic design and fuzzy analytic hierarchy process

Renewable energy is the energy generated from natural resources such as sunlight, wind, rain, tides and geothermal heat which are renewable. Energy resources are very important in perspective of economics and politics for all countries. Hence, the selection of the best alternative for any country takes an important role for energy investments. Among decision-making methodologies, axiomatic design (AD) and analytic hierarchy process (AHP) are often used in the literature. The fuzzy set theory is a powerful tool to treat the uncertainty in case of incomplete or vague information. In this paper, fuzzy multicriteria decision- making methodologies are suggested for the selection among renewable energy alternatives. The first methodology is based on the AHP which allows the evaluation scores from experts to be linguistic expressions, crisp, or fuzzy numbers, while the second is based on AD principles under fuzziness which evaluates the alternatives under objective or subjective criteria with respect to the functional requirements obtained from experts. The originality of the paper comes from the fuzzy AD application to the selection of the best renewable energy alternative and the comparison with fuzzy AHP. In the application of the proposed methodologies the most appropriate renewable energy alternative is determined for Turkey.     

Design optimization for the hybrid power system of a green building

This paper proposes an optimal design procedure for a green building equipped with renewable energy, energy storages, and proton exchange membrane fuel cells (PEMFCs). First, we introduce the hybrid power system of the green building and construct a simulation model using Matlab/SimPowerSystem?. The model parameters are tuned so that the system responses can be estimated without extensive experiments in the optimization processes. Second, we define the cost and reliability indexes to optimize the system design using three steps: component selection, component sizing, and power management (PM) adjustment. We further define the safety index to evaluate the system's sustainability under extreme conditions when no renewable energy is available. Last, we apply the proposed procedures to the green building and demonstrate the benefits of the optimal design. The proposed method can be directly applied to develop customized hybrid power systems in the future.     

Modelling of hybrid energy system—Part II: Combined dispatch strategies and solution algorithm

Computer simulation is an increasingly popular tool for determining the most suitable hybrid energy system type, design and control for an isolated community or a cluster of villages. This paper presents the development of the optimum control algorithm based on combined dispatch strategies, to achieve the optimal cost of battery incorporated hybrid energy system for electricity generation, during a period of time by solving the mathematical model, which was developed in Part I of this tri-series paper.The main purpose of the control system proposed here is to reduce, as much as possible, the participation of the diesel generator in the electricity generation process, taking the maximum advantage of the renewable energy resources available.The overall load dispatch scenario is controlled by the availability of renewable power, total system load demand, diesel generator operational constraints and the proper management of the battery bank. The incorporation of a battery bank makes the control operation more practical and relatively easier.     

Multi-objective optimal design of hybrid renewable energy systems using PSO-simulation based approach

Recently, the increasing energy demand has caused dramatic consumption of fossil fuels and unavoidable raising energy prices. Moreover, environmental effect of fossil fuel led to the need of using renewable energy (RE) to meet the rising energy demand. Unpredictability and the high cost of the renewable energy technologies are the main challenges of renewable energy usage. In this context, the integration of renewable energy sources to meet the energy demand of a given area is a promising scenario to overcome the RE challenges. In this study, a novel approach is proposed for optimal design of hybrid renewable energy systems (HRES) including various generators and storage devices. The ε-constraint method has been applied to minimize simultaneously the total cost of the system, unmet load, and fuel emission. A particle swarm optimization (PSO)-simulation based approach has been used to tackle the multi-objective optimization problem. The proposed approach has been tested on a case study of an HRES system that includes wind turbine, photovoltaic (PV) panels, diesel generator, batteries, fuel cell (FC), electrolyzer and hydrogen tank. Finally, a sensitivity analysis study is performed to study the sensibility of different parameters to the developed model.     

A knowledge-based approach to the design of integrated renewableenergy systems

Integrated renewable systems utilize two or more renewable energy resources and end-use technologies to supply a variety of energy needs, often in a stand-alone mode. A knowledge-based design approach that minimizes the total capital cost at a preselected reliability level is presented. The reliability level is quantified by the loss of power supply probability. The procedure includes some resource-need matching based on economics, the quality of energy needed, and the characteristics of the resource. A detailed example is presented and discussed to illustrate the usefulness of the design approach     

Technico-economic analysis of off grid solar PV/Fuel cell energy system for residential community in desert region

A technico-economic analysis based on integrated modeling, simulation, and optimization approach is used in this study to design an off grid hybrid solar PV/Fuel Cell power system. The main objective is to optimize the design and develop dispatch control strategies of the standalone hybrid renewable power system to meet the desired electric load of a residential community located in a desert region. The effects of temperature and dust accumulation on the solar PV panels on the design and performance of the hybrid power system in a desert region is investigated. The goal of the proposed off-grid hybrid renewable energy system is to increase the penetration of renewable energy in the energy mix, reduce the greenhouse gas emissions from fossil fuel combustion, and lower the cost of energy from the power systems. Simulation, modeling, optimization and dispatch control strategies were used in this study to determine the performance and the cost of the proposed hybrid renewable power system. The simulation results show that the distributed power generation using solar PV and Fuel Cell energy systems integrated with an electrolyzer for hydrogen production and using cycle charging dispatch control strategy (the fuel cell will operate to meet the AC primary load and the surplus of electrical power is used to run the electrolyzer) offers the best performance. The hybrid power system was designed to meet the energy demand of 4500 kWh/day of the residential community (150 houses). The total power production from the distributed hybrid energy system was 52% from the solar PV, and 48% from the fuel cell. From the total electricity generated from the photovoltaic hydrogen fuel cell hybrid system, 80.70% is used to meet all the AC load of the residential community with negligible unmet AC primary load (0.08%), 14.08% is the input DC power for the electrolyzer for hydrogen production, 3.30% are the losses in the DC/AC inverter, and 1.84% is the excess power (dumped energy). The proposed off-grid hybrid renewable power system has 40.2% renewable fraction, is economically viable with a levelized cost of energy of 145 $/MWh and is environmentally friendly (zero carbon dioxide emissions during the electricity generation from the solar PV and Fuel Cell hybrid power system).     

A modular design approach for PEM electrolyser systems with homogeneous operation conditions and highly efficient heat management

Because of its advantages, which are fast response times, high power densities and, therefore, compact system design, using polymer electrolyte membrane electrolyser (PEMEL) technology is a promising way to store the excess energy generated by renewable energy sources. With the approach of hydraulic cell compression homogeneous pressure and current distribution is guaranteed, and waste heat management as well as high-pressure operation are improved compared to conventional mechanically compressed PEMEL stacks. The new design approach presented in this work brings the concept of hydraulic cell compression close to an industrial design while preserving the mentioned advantages and providing a high level of modularity. The concept was experimentally validated for hydrogen production using a laboratory scale stack consisting of five single cells having an active cell area of 25 cm² each. A study on process water independent stack temperature control was performed using water as a hydraulic medium. Furthermore, the capability of high-pressure operation was investigated up to a process media pressure of 30 bar.     

Market design for renewable energy auctions: An analysis of alternative auction formats

Auctions are widely used to determine the remuneration for renewable energies. They typically induce a high concentration of renewable energy plants at very productive sites far-off the main load centres, leading to an inefficient allocation as transmission line capacities are restricted but not considered in the allocation, resulting in an inefficient system configuration in the long run. To counteract these tendencies effectively, we propose a combinatorial auction design that allows to implement regional target capacities, provides a simple pricing rule and maintains a high level of competition between bidders by permitting package bids. By means of extensive numerical experiments we evaluate the combinatorial auction as compared to three further RES auction designs, the current German nationwide auction design, a simple nationwide auction, and regional auctions. We find that if bidders benefit from high enough economies of scale, the combinatorial auction design implements system-optimal target capacities without increasing the average remuneration per kWh as compared to the current German auction design. The prices resulting from the combinatorial auction are linear and anonymous for each region whenever possible, while minimal personalised markups on the linear prices are applied only when necessary. We show that realistic problem sizes can be solved in seconds, even though the problem is computationally hard.     

Financing investments in renewable energy : the impacts of policy design

The costs of electric power projects utilizing renewable energy technologies (RETs) are highly sensitive to financing terms. Consequently, as the electricity industry is restructured and new renewables policies are created, it is important for policymakers to consider the impacts of renewables policy design on RET financing. This paper reviews the power plant financing process for renewable energy projects, estimates the impact of financing terms on levelized energy costs, and provides insights to policymakers on the important nexus between renewables policy design and financing. We review five case studies of renewable energy policies, and find that one of the key reasons that RET policies are not more effective is that project development and financing processes are frequently ignored or misunderstood when designing and implementing renewable energy policies. The case studies specifically show that policies that do not provide long-term stability or that have negative secondary impacts on investment decisions will increase financing costs, sometimes dramatically reducing the effectiveness of the program. Within U.S. electricity restructuring proceedings, new renewable energy policies are being created, and restructuring itself is changing the way RETs are financed. As these new policies are created and implemented, it is essential that policymakers acknowledge the financing difficulties faced by renewables developers and pay special attention to the impacts of renewables policy design on financing. As shown in this paper, a renewables policy that is carefully designed can reduce renewable energy costs dramatically by providing revenue certainty that will, in turn, reduce financing risk premiums.     

Design of isolated renewable hybrid power systems

Isolated electrical power generating units can be used as an economically viable alternative to electrify remote villages where grid extension is not feasible. One of the options for building isolated power systems is by hybridizing renewable power sources like wind, solar, micro-hydro, etc. along with appropriate energy storage. A method to optimally size and to evaluate the cost of energy produced by a renewable hybrid system is proposed in this paper. The proposed method, which is based on the design space approach, can be used to determine the conditions for which hybridization of the system is cost effective. The simple and novel methodology, proposed in this paper, is based on the principles of process integration. It finds the minimum battery capacity when the availability and ratings of various renewable resources as well as load demand are known. The battery sizing methodology is used to determine the sizing curve and thereby the feasible design space for the entire system. Chance constrained programming approach is used to account for the stochastic nature of the renewable energy resources and to arrive at the design space. The optimal system configuration in the entire design space is selected based on the lowest cost of energy, subject to a specified reliability criterion. The effects of variation of the specified system reliability and the coefficient of correlation between renewable sources on the design space, as well as the optimum configuration are also studied in this paper. The proposed method is demonstrated by designing an isolated power system for an Indian village utilizing wind-solar photovoltaic-battery system.     

A conceptual chemical looping combustion power system design in a power-to-gas energy storage scenario

Increasing global energy demand and the continued reliance on non-renewable energy sources, especially in developing countries, will cause continued increases in greenhouse gas emissions unless alternative electricity generation methods are employed. Although renewable energy sources can provide a clean way to produce electricity, the intermittent nature of many existing renewable energy sources, such as energy from the wind or sun, can cause instability in the energy balance. Energy storage systems such as power-to-gas may provide a clean and efficient way to store the overproduced electricity. In this work, a power-to-gas energy storage system coupled with a chemical looping combustion combined-cycle power generation system is proposed to provide base and intermediate load power from the unused electricity from the grid. Enhanced process integration was employed to achieve optimal heat and exergy recovery. The simulation results using ASPEN Plus V8.8 suggest that electric power generation with an overall energy efficiency of 56% can be achieved by using a methane chemical looping combustion power generation process with additional hydrogen produced from a solid oxide electrolysis cell. The proposed system was also evaluated to further improve the system's total energy efficiency by changing the key operating parameters.     

Dynamic life cycle assessment (LCA) of renewable energy technologies

Before new technologies enter the market, their environmental superiority over competing options must be asserted based on a life cycle approach. However, when applying the prevailing status-quo Life Cycle Assessment (LCA) approach to future renewable energy systems, one does not distinguish between impacts which are ‘imported’ into the system due to the ‘background system’ (e.g. due to supply of materials or final energy for the production of the energy system), and what is the improvement potential of these technologies compared to competitors (e.g. due to process and system innovations or diffusion effects). This paper investigates a dynamic approach towards the LCA of renewable energy technologies and proves that for all renewable energy chains, the inputs of finite energy resources and emissions of greenhouse gases are extremely low compared with the conventional system. With regard to the other environmental impacts the findings do not reveal any clear verdict for or against renewable energies.Future development will enable a further reduction of environmental impacts of renewable energy systems. Different factors are responsible for this development, such as progress with respect to technical parameters of energy converters, in particular, improved efficiency; emissions characteristics; increased lifetime, etc.; advances with regard to the production process of energy converters and fuels; and advances with regard to ‘external’ services originating from conventional energy and transport systems, for instance, improved electricity or process heat supply for system production and ecologically optimized transport systems for fuel transportation.The application of renewable energy sources might modify not only the background system, but also further downstream aspects, such as consumer behavior. This effect is, however, strongly context and technology dependent.     

An integrated system framework for fuel cell-based distributed green energy applications

The environmental pollution and diminishing conventional fuel sources and global warming problems make it more attractive for considering renewables as alternative energy sources, such as solar, wind and micro hydro, etc. Recent advances in hydrogen and fuel cell technologies further facilitate these energy options to supply electrical power to various communities. Hydrogen fuel cell systems coupled with renewable energy sources stand out as a promising solution. This paper presents an integrated system framework for fuel cell-based distributed energy applications. Five components are included in this framework: a physical energy system application, a virtual simulation model, a distributed coordination and control, a human system interface and a database. The integrated system framework provides a means to optimize system design, evaluate its performance and balance supplies and demands in a hydrogen assisted renewable energy application. It can either be applied to a distributed energy node that fulfills a local energy demand or to an energy-network that coordinates distributed energy nodes in a region, such as a hydrogen highway. The proposed system framework has been applied in the first phase of our multi-phases project to investigate and analyze the feasibility and suitability of hydrogen fuel assisted renewable power for a remote community. Through integration with an available renewable energy profile database, the developed system efficiently assists in selecting, integrating, and evaluating different system configurations and various operational scenarios at the application site. The simulation results provide a solid basis for the next phase of our demonstration projects.     

IRES—A program to design integrated renewable energy systems

Integrated renewable energy systems (IRES), which utilize different resources such as wind, solar heat, solar radiation, biomass, and falling water to satisfy various energy needs, are well suited for remote rural areas. In this paper, we present an approach to design an IRES based on the loss of power-supply probability (LPSP) as the key system parameter and minimization of the initial capital investment. Also, a computer program named IRES is developed for use as a design tool. A numerical example is included to demonstrate the design procedure.     

Dynamic characteristics and operation strategy of the discharge process in compressed air energy storage systems for applications in power systems

In the context of the rapid development of large-scale renewable energy, large-scale energy storage technology is widely considered as the most effective means of improving the quality and security of electricity. In the existing energy storage technology, advanced adiabatic compressed air energy storage (AA-CAES) technology has broad application prospects because of its advantages of low pollution, low investment, flexible site selection, and large capacity. However, the lack of an in-depth understanding of the dynamic characteristics of CAES systems has severely limited the development of system design and control strategy, resulting in a lack of commercial operation of large-scale CAES systems. This paper describes the design and implementation of a CAES plant and its controller for applications in the distribution network level. The dynamic mathematical models of AA-CAES were established and a feasible control strategy for the grid-connected process was developed to analyze the dynamic characteristics of the system in the discharge stage. The work done in this study provided a data reference for the deep understanding of the dynamic characteristics of AA-CAES, system design, and control strategy in the industry.     

New directions in renewable energy education

The renewable energy industry is growing rapidly amidst rising concerns about oil depletion and climate change. Renewable energy is seen by many as part of the appropriate response to these concerns and some national Governments have put programs in place to support the wider use of sustainable energy systems. This has led to a rapid increase in demand for renewable energy specialists who are able to design, install and maintain such systems. Most engineers are not trained to use these renewable energy technologies and most are not aware of the principles of sustainability. There is therefore an urgent need to develop and implement new courses that prepare engineers, scientists and energy planners to work with renewables to produce sustainable energy generation systems.Renewable energy education is a relatively new field and previously it formed a minor part of traditional engineering courses. These days it has an identity of its own, with special techniques, standards and requirements which are not normally encountered in other disciplines. Attempts to add one or two units of study on renewables into traditional science and engineering degrees are unlikely to produce graduates with sufficient knowledge or understanding to use renewables effectively. Modern renewable energy education includes a study of the technology, resources, systems design, economics, industry structure and policies in an integrated package. This prepares the graduates to design sound systems from amongst the range of options available. There are more pitfalls in the use of renewables than there are in using the more mature conventional technologies and systems. Designers, installers and service personnel need to be particularly aware of the industry and the characteristics of the various firms and their technologies.Over the past decade several new approaches have emerged to renewable energy education that seek to address the needs of the 21st century for sustainable energy supply systems.This paper will describe the aims, philosophy, structure and outcomes of several of these initiatives. It includes courses in renewable energy science, renewable energy engineering, renewable energy policy and planning and renewable energy technician training. The paper will also describe some aspects of the training of researchers in cooperation with the renewable energy industry.     

绿色建筑中可再生能源利用方案的设计

通过对《绿色建筑评价标准》(GB/T 50378-2006)中关于可再生能源利用条文的分析解读,总结了在绿色建筑中可再生能源利用方案评价的主要内容和评价方法。结合实际工作经验,就不同的可再生能源利用方式在不同建筑类型中的应用方案选择进行了分析与探讨,并提出了绿色建筑中可再生能源利用的发展方向。     

How to design a sustainable heavy industrial estate

The Mid West of Western Australia, south of the Pilbara, is developing as the next major mineral province in Australia. The province will be served by a new port at Oakajee and will be backed by a 4000 + ha greenfield industrial area. LandCorp, the State Government's land development agency intends that the Oakajee Industrial Estate (OIE) will be a “sustainable industrial estate”.This paper describes the design process used to produce a flexible and adaptable layout of the estate to maximise use of renewable energy and minimise carbon emissions. The design and planning was complex because it had to anticipate a 50 year development program. Issues addressed included site characteristics and context, land allocation to optimise energy efficiency, embedding a multi-user co/tri-generation system in the middle of the estate, identify and estimating the production of energy from on-site and regional sources of renewable energy, options for reducing greenhouse emissions, waste reduction and reuse; and issues relating to the governance and management of the estate that will enable these site innovations to occur.