Proposed Energy System Research Articles

Retail Market Equilibrium in Multicarrier Energy Systems: A Game Theoretical Approach

Multicarrier energy systems have provided the opportunity for users who are experiencing only must-run loads to participate in demand response programs by using self-generation units. In this paper, a bilevel game between so-called energy retailers and consumers with firm loads (as subsystems) is formulated in a multicarrier energy system. In the first level of this game, energy retailers offer selling prices for different energy carriers to maximize their profit. Consequently, consumers react to the offered prices by managing their purchasing power from the retail market to minimize their energy bill in the second level. The proposed approach leads to a mixed integer nonlinear programming problem which is sophisticated to solve. To simplify this complex problem, a solution method based on discretization technique is introduced to approach to an epsilon Nash point. The better performance of the proposed energy system model is shown in comparison with the base case and its effectiveness is validated experimentally over a practical benchmark system. The simulation results show a noticeable reduction in the energy production cost and users’ energy bill. Moreover, energy retailers gain more profit in the proposed approach.

Health risk perception and shale development in the UK and US

In this paper, we examine discourse in public deliberations in pre-development locales in the UK and US about advantages and disadvantages of future shale development (‘fracking’). We aimed to understand how people anticipate potential health effects, broadly construed, of environmental toxicity and disturbance in the context of planned, but not yet implemented, energy development. In day-long deliberations with small, diverse groups in two cities in each country (London, Cardiff in the UK; Los Angeles, Santa Barbara in the US), participants discussed impacts on health and well-being using three main rubrics: ‘It’s money or health’, ‘Why take chances?’ and ‘Beyond the tipping point’. Throughout, participants framed health as an intrinsically moral issue, with collective responsibility as a dominant normative frame. We identify the concept of compound risk to underscore effects of multiple risks and hazards on people’s sensibilities about anticipated future health and environmental harm. The findings demonstrate how and why diverse publics in pre-impact sites in both countries saw shale extraction as high stakes development that poses significant, often unacceptable, risks to human and environmental health and well-being. Risks extended beyond toxicity to broad threats to health, including, for some, the end of life as we know it on the planet. Overall, participants’ discussions of health were more connected to social categories and their underlying moral principles than to technological details. This work contributes evidence of blurred boundaries between environment and health as well as the importance people place on social risks in the context of proposed energy system change.

Thermodynamic and economic analysis of the integration of high-temperature heat pumps in trigeneration systems

Polygeneration energy systems are proven to be a reliable, competitive and efficient solution for energy production. The recovery of otherwise wasted energy is the primary reason for the high efficiency of polygeneration systems. In this paper, the integration of a high-temperature heat pump within a trigeneration system is investigated. The heat pump uses the low-temperature heat from the condenser of the absorption chiller as heat source to produce hot water. A numerical model of the heat pump cycle is developed to evaluate the technical viability of current heat pump technology for this application and assess the performance of different working fluids. An exergy analysis is performed to show the advantages of the novel trigeneration system with respect to traditional systems for energy production. Moreover, a levelized cost of electricity method is applied to the proposed energy system to show its generic economic feasibility. Finally, actual energy demand data from an Italian pharmaceutical factory are considered to evaluate the economic savings obtainable with the integrated system, implemented in a case study. A two-level algorithm is proposed for the economic optimization of the investment. The synthesis/design problem is addressed by a genetic algorithm and the optimal operation problem is solved by a linear programming method. Results show that the integration of a high-temperature heat pump within a trigeneration system provides flexibility to cover variable energy demands and achieve valuable economic and energy performances, with global cost savings of around 40% with respect to separate production and around 10% with respect to traditional cogeneration and trigeneration systems.

Thermoeconomic assessment of a novel integrated CHP system incorporating solar energy based biogas-steam reformer with methanol and hydrogen production

This paper deals with a novel solar-biogas fueled combined heat and power system with methanol and hydrogen production. The proposed energy system consists following subsystems: solar based biogas-steam reformer, gas turbine cycle, Rankine and organic Rankine cycles, pressure swing adsorption, carbon capture and sequestration and methanol synthesis unit. The selected solar system is molten salt tower-based concentrated solar thermal plant that provides required thermal energy for reforming process. The multigeneration system is comprehensive analyzed thermoeconomically and exergoenvironmentally. A parametric study is conducted to find the effects of key parameters on the system performance. The considered key parameters include steam to carbon ratio of reforming process, operating temperature and pressure of reformer. The results show that Tr is the most effective parameters for improving system performance. A 200 K increase in reforming temperature, from 923 K to 1123 K, leads to decreases of 15% and 10% in the energy and exergy efficiencies, respectively. The opposite trend is observed for net power output and mass flow rate of produced methanol when key parameters change. Nevertheless, mass flow rate of produced methanol plays most important role for evaluating energy and exergy efficiencies. Also, gas turbine cycle and reformer have highest exergy destruction rate of 140 MW and 134 MW, respectively when system operates in optimum condition. Moreover, best exergoenvironmental parameters are obtained at higher value of reforming temperature and lower values of reforming pressure and steam to carbon ratio of reforming process.

Feasibility Study of Off-Grid Sustainable Energy System for Coastal Bhasan Char to Rehabilitate Rohinga Refugees

Government of Bangladesh (GoB) is implementing an emergency humanitarian project at coastal island Bhasan Char under Hatiya of Noakhali District, from September 2017 to temporarily rehabilitate a portion of incoming Rohinga refugees before they can repatriate to their home land, Myanmar. Under this project, GoB will carry out land development, construction of embankment as well as other infrastructures. This study is aimed at providing partial basic energy support to the government’s initiative of rehabilitating 103,200 Rohinga refugees. Under the study, we check the feasibility of establishing off-grid sustainable energy system. We also perform the financial analysis of the proposed energy system by considering 20 years life-span of the project. Our study shows that annual average solar insolation in Bhasan char is 4.82kWh/m2/day and daily bright sunshine hour varies from 3 hours to 11 hours. Wind flow data of Bhasan char shows the average annual wind speed of 3.74m/s which is available round the clock and throughout the year. These data justify the suitability of environment friendly off-grid solar energy system as well as wind energy system for Bhasan Char. However, considering the effective generation hours, to diversify energy sources and basing on analysis result using HOMER (Hybrid Optimization of Multiple Energy Resources) software – we are proposing a hybrid energy system with 40% contribution from wind and rest 60% from solar. Our financial analysis of the project shows a total cost of 43.848 Crore (USD 0.525 Crore) over 20-year life span. Therefore, a BDT 2.192 Crore/year is quite economical and justifiable, considering the long-term impact that it might provide to displaced 103,200 refugees as well as the solution that we are providing to adverse negative socio-economic impact on Bangladesh from Rohinga issue.

Designing and Optimization of Stand-alone Hybrid Renewable Energy System for Rural Areas of Punjab, Pakistan

Increasing energy demand accompanied by diminishing of natural resources is the prime reason behind the growing popularity of renewable energy resources. Hence to develop a power system model for sustainable and efficient power deliverance is inevitable. To serve the purpose, we proposed in this paper a hybrid renewable energy system (HRES) that consists of run-off canal micro hydro/PV/wind integrated with a diesel generator. Main purpose is the electrification of remote areas of province Punjab, Pakistan. The authors selected the BS link canal-I located at 300 52’ N and 730 55’ E in Punjab, Pakistan, for the proposed HRES. Beforehand, load and resource profile of selected site was evaluated to present an economically optimized model of the proposed energy system. Moreover, Hybrid Optimization Model for Electric Renewables (HOMER) was used as an optimization tool to perform techno-economic feasibility of the micro hydro/PV/wind energy system to entertain the evaluated load of the location. Mainly three strategies are employed due to scarcity of hydro resources and based on the availability of the energy resources. First strategy suggests to use diesel generator integrated with solar and wind power systems, HOMER declares this strategy most expensive with total Net Present Cost (NPC) of $ 670,121 and Cost of Energy (COE) of $ 0.0936/kWh. The recovery period of the hybrid energy system under this strategy is 13 years. The second strategy focuses on the water management strategy using 100 % renewable energy. NPC diminishes to $ 479,835 and the COE reduces to $ 0.0670/kWh. The system recovers all the incurred cost in 5.5 years. The last one enacts renewable energy systems with capacity shortage scheme. NPC and the COE reduces to $ 284,877 and $ 0.0437/kWh respectively from the previously discussed strategy. The system recovers all the incurred cost in 1.7 years. Based on the NPC, the COE and the minimum payback period, HOMER executes the optimization analysis on all the proposed strategies and found 1 st strategy to be the least feasible and 3 rd strategy the most feasible respectively.

Analysis of photovoltaic mini-grid systems for remote locations: A techno-economic approach

This paper presents a techno-economic analysis of photovoltaic mini-grid systems (PMs), using a group of remote houses in 3 locations in Nigeria, as case studies. It uses a worst-case users' load demand approach for the design and analysis of the proposed energy system, according to international technical standards. It presents detailed capacity, yield and losses, battery state of charge (SoC), reliability, users' load demand increase (Ldi), and life cycle economic analyses by using the Hybrid Optimisation for Electric Renewables (HOMER) simulation tool. The effect of 25% Ldi is also considered in the paper. The study can be used to develop a practical energy model to address the poor energy situation in those locations when they are implemented. Results indicate that PMs of 68, 76, and 61 kW can meet the users' demand of ~63 500 kWh/year with an availability of 99.2% for the locations, respectively. By including a 30-kVA diesel generator to the PMs' model, an availability of 100% was obtained, demonstrating that the issue of loss of energy supply for several days in the year due to users' Ldi and the cloudy days is being addressed. The results further show that although the hybrid energy systems have relatively higher initial capital, total life cycle and replacement costs, and the cost of energy, they achieve a higher reliability compared with the proposed PMs. The research can be useful for planning solar PV infrastructure for remote locations around the world.

Control strategy of switching regulators for fuel‐cell power applications

It is often assumed that the input voltage source of a switch-mode power supply is constant or shows negligible small variations. However, the last assumption is no longer valid when a fuel-cell stack is used as input source. A fuel-cell stack is characterised by low and unregulated DC output voltage, in addition, this voltage decreases in a non-linear fashion when the demanded current increases; henceforth, a suitable controller is required to cope the aforementioned issues. In this study, an average current-mode controller is designed using a combined model for a fuel-cell stack and a boost converter; moreover, a selection procedure for the controller gains ensuring system stability and output voltage regulation is developed. The proposed energy system uses a fuel-cell power module (polymer electrolyte membrane fuel cells) and a boost converter delivering a power of 900 W. Experimental results confirm the proposed controller performance for output voltage regulation via closed-loop gain measurements and step load changes. In addition, a comparison between open- and closed-loop measurements is made, where the controller robustness is tested for large load variations and fuel-cell stack output voltage changes as well.

Feasibility analysis on distributed energy system of Chongming County based on RETScreen software

A reference scheme of a multiple energy complementation system is of great importance of Chongming's energy system development. In this paper, four feasible scenarios which are distinguished by energy supply forms have been discussed based on RETScreen software. Economic analysis as well as the renewable sources penetration was taken into account. The outcome of equipment size optimization of each subsystem was summarized and the comparison between different scenarios was afterwards conducted in order to provide some thoughtful comments for the future energy system construction. Results indicate that the introduction of natural gas based CHP system and biomass system is a necessity for covering the energy demand and minimizing the energy import. The CHP scenario achieves the most annual balance (0.3272 billion yuan) and net present value (2.556 billion yuan) and cuts down the GHG emission by 1.978 Mt per year. Moreover, the net present value of the proposed energy system is sensitive to the variation in energy policy. When the financial aids fluctuates by 50%, the net present value can change in the range from 60% to 70%. However, even when the policy is extremely unfavorable, the economical profit of CHP scenario is still obvious.

Life Cycle Assessment (LCA) of biogas-fed Solid Oxide Fuel Cell (SOFC) plant

The Life Cycle Assessment (LCA) of biogas-fed Solid Oxide Fuel Cell (SOFC) integrated with a CO2 recovery system is presented in this work. The goal of the work is to evaluate the environmental performance of an SOFC fueled with sewage biogas and to compare it with traditional technologies (internal combustion engines and microturbines) using the same fuel. CO2 recovery is performed through a tubular photobioreactor, fixing the recovered carbon in the form of a micro-algae.The analysis takes into account both the biogas production line (anaerobic digester) and its exploitation into the fuel cell (i.e., the power generator).Results show that the SOFC manufacturing activity is highly intensive since it requires a large amount of use of electricity. During operation, instead, the highest burden is associated with the fuel production. We analyzed two scenarios for biogas operation underlining the benefits of introducing sludge pre-thickening before the anaerobic digestion process. The use of a sludge pre-thickening system can reduce the inlet flow of natural gas into the plant, thus affecting the fuel chain contribution and reducing the overall impact.The photobioreactor results in consuming more energy than what it produces (looking at the operation phase only; the manufacturing phase was not even included) and being responsible for more carbon emissions than the amount fixed in algae. On the other side, data for the photobioreactor system were based on a real system at the proof-of-concept level. Therefore significant improvements are expected for an industrial-size system.Finally, the SOFC environmental burdens have been compared with main competitors in the same field (internal combustion engines and microturbines), showing the superior environmental performance. The proposed energy system is thus an interesting choice for cleaner energy production.

Optimized design of a hybrid PV‐wind‐diesel energy system for sustainable development at coastal areas in Bangladesh

Power generation capacity of Bangladesh needs to be enhanced to support the rising electricity demand. Bangladesh has predominantly used fossil fuel generators for the past decades. Saint Martin's Island and Kuakata are two significant areas that lie at or near the coast of Bangladesh with an average annual solar radiation of 4.81 and 4.65 kWh m−2 day−1, respectively. The monthly average wind speeds at a height of 25 meters are 4.79 and 4.54 m s−1, respectively. Considering this data and the benefits of the optimized hybrid systems, HOMER (Hybrid Optimization Model for Electric Renewable) is used to optimize a system for each of these areas. The costs of energy found from the proposed optimized PV‐wind‐diesel hybrid Energy system for Saint Martin's island and Kuakata are 0.393 and 0.392 USD kW−1 h−1, respectively, the net present cost (NPC) also has been evaluated as 168767.831 USD which are quite reasonable with respect to the present situation in Bangladesh. The major objective of this proposed optimized design is to supply the maximum load demand using renewable sources with the minimum cost of energy (COE) and reduce the burning of fuel and also reduce the emission of CO2. The proposed energy system is able to meet 67.3 and 62.3% load demand using renewable sources, which helps to reduce the GHG (Green Houses Gas) emission by 67 and 64% for Saint Martin's island and Kuakata, respectively when compared to a diesel system. Total load served throughout the year is 33,611 kWh, which is 16% higher than the previously designed system with approximately equivalent COE. © 2016 American Institute of Chemical Engineers Environ Prog, 36: 297–304, 2017

Retrofitting domestic appliances for PV powered DC Nano-grid and its impact on net zero energy homes in rural India

There is a growing interest in employing renewable energy conversion systems for supplying power to rural households in India. Such systems have to be designed with maximum efficiency and with minimum intermediate stages. In this context, modifications are proposed for two commonly used rural household appliances; the wet-grinder and the dough-maker for Net zero energy Homes (NZEH). In this paper, AC motors that are conventionally employed for the above two appliances are replaced by Permanent Magnet DC (PMDC) motors, thereby avoiding inverters in the system. The power electronic interfaces for the PMDC motor are also developed. Investigations have been presented to show an increase in energy efficiency and reduction in the cost of the appliances, as a result of this replacement. Roof Top Photo-Voltaic (RTPV) array is the main power source of the proposed NZEH. The new architecture of the NZEH has RTPV and loads directly powered by the PV array, thus creating a DC Nano-grid. The sizes of the PV array required for this NZEH are found to have been reduced with the proposed modifications. Analysis on embodied energy and payback period for the proposed energy system are also presented. This article also presents the energy balance study for a rural home with the new appliances.

Modeling of an Optimized Hybrid Energy System for Kutubdia Island, Bangladesh

This paper presents an optimized energy system model for a small locality in Kutubdia Island, Bangladesh at latitude of 21.82 °N, longitude of 91.86 °E. This isolated island is located at the southern coast of Bangladesh, separated from the main land by the Kutubdia channel. At present, grid connection from the mainland is not present and is not planned in the near future. The proposed energy system comprises Solar PV, Wind turbines, Biogas generators for power generation whereas a diesel generator has been used as backup power supply and batteries have been considered to facilitate energy storage. Hybrid Optimization Model for Electric Renewable (HOMER) has been used to obtain an optimized system comprising all the renewable energy resources present. The designed energy system consists of 28 kW Solar PV panels, 30 kW Wind Turbines, 8 kW Biogas Generator, 9 kW Diesel Generator. The system generates electricity with a renewable fraction of 97%. The cost of electricity has been estimated as US$ 0.42/kWh considering 10% Rate of Return with an initial capital cost of US$ 199,541.

Maximum Power Point Tracking of Hybrid Tidal Current—Supercapacitor Energy Conversion System

This paper proposes control of maximum power tracking system of tidal current energy system. A permanent magnet synchronous generator (PMSG) works as a variable speed generator in the proposed energy system. A controller was applied to achieve the maximum power control of tidal current turbine on a wide range of water current speed change. A dynamic model and simulation of the energy system coupled with current change are presented. The measured DC voltage and DC current are used to determine the position of maximum power point that controls the DC/DC boost converter duty cycle depending on the Hill Climb Search (HCS) algorithm. This algorithm doesn’t require any information or measurements about current’s speed change or generator’s characteristics. A supercapacitor added to fix the load voltage despite of tidal current speed or load variations. Simulation results show the effectiveness of the controller proposed system.

Techno-economic Feasibility Study of a Solar PV-Diesel System for Applications in Northern Part of Bangladesh

Renewable energy offers convenient energy solution to the population live in isolated areas. The residents can utilize the locally available energy resources for fulfilling their need for electricity. The availability of electricity in the darkness of night facilitates higher productivity irrespective of gender. In this paper, design of a solar PV-diesel mini-grid system has been presented for a locality in Char Parbotipur (25.75°N 89.66°E). This island is situated 20 km north-east from Kurigram district, Bangladesh and surrounded by Brahmaputra river and Dudhkumar river, far from the national grid. Very few residents use stand-alone Solar Home Systems (SHS) and diesel generators. Diesel generators have environmental concern which can be minimized by using hybrid renewable energy systems. This paper aims at designing an optimal energy system consisting solar PV having diesel generator for fulfilling the load demand. The proposed energy system can generate electricity at a cost of $0.461/kWh for a load of 115 kWh/day. Sensitivity analysis is presented to understand the effect of diesel price and solar irradiation on the cost of electricity and net present cost of the system. Comparison between the proposed hybrid renewable energy system and an energy system comprising diesel generator only are also presented to understand the effect of solar PV integration with diesel generators for environmental benefits.

Thermodynamic Analysis of Coupling a SOEC in Co‐Electrolysis Mode with the Dimethyl Ether Synthesis

AbstractThis work describes a thermodynamic model of an integrated system for the production of a syngas, via a solid oxide electrolysis cell (SOEC), coupled with a subsequent catalytic upgrading into dimethyl ether (DME). The proposed energy system has been investigated on a thermodynamic basis, including exergy analysis.The syngas composition required for the catalytic upgrading is strongly affecting the SOEC design. SOEC operating conditions have been chosen in order to reach an H2/CO ratio close to 1 while avoiding carbon formation. The produced syngas from the SOEC is then pre‐treated and DME is synthesized in a one‐step reactor in which both methanol synthesis and dehydration occur. Two different plant configurations have been investigated including an ambient pressure and a pressurized system. The layout and operating parameters have been chosen in order to maximize the purity of the produced DME without affecting the overall efficiency and yield. The global heat demand has been assessed with the waste heat recovery method. In the optimal configuration, an improvement in the DME content of the final product is obtained, reaching a value of 99.8% in mass. Therefore, such configuration would allow the final product to be readily used for transportation applications.

Energy planning and development in Malaysian Borneo: Assessing the benefits of distributed technologies versus large scale energy mega-projects

A contentious debate is taking place over plans for a series of mega-dams under development in Malaysian Borneo. There is little quantitative analysis of the energy options or cost and benefit trade-offs in the public discussion or the literature. To fill this gap we developed a model of the proposed energy system and alternative scenarios using the commercial energy market software PLEXOS. We prepared a 15 year long-term capacity energy expansion model for the state of Sarawak which includes existing generation, resource and operability constraints, direct and indirect costs. We explore a range of demand growth and policy assumptions and model the resulting generation mixes and economic trade-offs. Our central finding is that a diversified generation mix including solar and biomass waste resources can meet future demand at lower cost than additional dam construction.

Techno-economic analysis of hybrid photovoltaic/diesel/battery off-grid system in northern Nigeria

The rate of dependence on stand-alone diesel generator for individual electricity generation among households in Nigeria is geometrically increasing and has thus led to significant increase of the environment pollution. This is due to the inability of the utility company to meet the energy demand of its yearning consumers due to ageing and limitations in power infrastructures. This has led to about 40% of the country's population been cut off from the national grid. In view of these hazardous effects posed from the usage of these individual diesel-powered generations, this paper reports on the assessment of techno-economic viability of a hybrid photovoltaic diesel/battery off-grid system as an alternative solution to these threats. For that purpose, a remote area located far in the northern part of Nigeria was taken as the case study in which an international institution with peak demand of 90 kW was considered. The HOMER optimization software is used to evaluate both the technical and economic viability of the proposed energy system by taking into account the variations of both the solar radiation and diesel prices, as experienced in most part of Nigeria. The study reveals the potential capability of the hybrid photovoltaic/diesel energy system with battery backup as a good alternative energy source for individual household replacement for diesel-powered generator. In addition, the proposed system is of high energy potential as well as low carbon emission at affordable cost of electricity.

Wind Energy Based Packet Energy System

This paper proposes a wind turbine and battery storage based packet energy system. The proposed energy packet network can be used to make renewable energy sources more practical and supply energy on demand. The flow of energy in the energy packet network is controlled by a Smart Energy Dispatching Centres (SEDC). SEDCs receive the energy requests from the customers and it tries to optimize the energy flows by making the best use of renewable energy resources, existing price and policies. The proposed energy system can take energy flow instructions from a SEDC. In the present analysis a small wind energy system with battery storage has been simulated in Matlab/Simulink. The system has been modelled using low order transfer functions. Random switching has been done to get energy packets from the model. A prototype of the battery based energy storage system has been designed and implemented. Lab tests and simulation results indicates that the designed packet energy network system is able to provide energy packet as required by the grid. Additionally the output power from a very large energy packet network is also found to be stable with the existence of large load fluctuation.

Solar Heating and Nocturnal Cooling System Integrated in Refurbished Buildings

Green energy system for the old building retrofitting for energy efficiency upgrade was proposed in this paper, which was composed by solar radiant panels, energy storage, multi-source heat pump and low temperature difference energy supplier. This building energy system can make efficient use of solar energy, sky radiation and natural energy, through the radiant panel installed as the building envelop or on the roof. Two types of the proposed energy system were applied for building refurbishing and their performances were comprehensively studied. It is shown that the building energy consumption annually is less than 30kWh/m2 and the indoor temperature is over 18°C in winter and under 26°C in summer, fully meeting the comfort temperature requirements.