Distributed Energy Generation Research Articles

Grid emulator for small scale distributed energy generation laboratory

This paper presents the design of a grid emulator dedicated to test small scale distributed energy generation. laboratory The proposed emulator aims to test its performances under different power quality conditions considering grid codes and standards. The developed emulator can generate common grid faults and line impedance variations. This last point is an additional feature versus common grid emulators. The paper discusses design and implementation aspects. Emulator performance analysis are investigated under special operating conditions. Simulation results are carried out to illustrate theoretical developments and a set of experimental results are provided to demonstrate the effectiveness of the proposed emulator.

Strategic Behavior of Retailers for Risk Reduction and Profit Increment via Distributed Generators and Demand Response Programs

Following restructuring of power industry, electricity supply to end-use customers has undergone fundamental changes. In the restructured power system, some of the responsibilities of the vertically integrated distribution companies have been assigned to network managers and retailers. Under the new situation, retailers are in charge of providing electrical energy to electricity consumers who have already signed contract with them. Retailers usually provide the required energy at a variable price, from wholesale electricity markets, forward contracts with energy producers, or distributed energy generators, and sell it at a fixed retail price to its clients. Different strategies are implemented by retailers to reduce the potential financial losses and risks associated with the uncertain nature of wholesale spot electricity market prices and electrical load of the consumers. In this paper, the strategic behavior of retailers in implementing forward contracts, distributed energy sources, and demand-response programs with the aim of increasing their profit and reducing their risk, while keeping their retail prices as low as possible, is investigated. For this purpose, risk management problem of the retailer companies collaborating with wholesale electricity markets, is modeled through bi-level programming approach and a comprehensive framework for retail electricity pricing, considering customers’ constraints, is provided in this paper. In the first level of the proposed bi-level optimization problem, the retailer maximizes its expected profit for a given risk level of profit variability, while in the second level, the customers minimize their consumption costs. The proposed programming problem is modeled as Mixed Integer programming (MIP) problem and can be efficiently solved using available commercial solvers. The simulation results on a test case approve the effectiveness of the proposed demand-response program based on dynamic pricing approach on reducing the retailer’s risk and increasing its profit.

Low-grade waste heat integration in distributed energy generation systems - An economic optimization approach

This paper proposes a Mixed-Integer Linear Programming (MILP) formulation for the economic optimization of the synthesis, design, and operation of an energy supply system of a manufacturing company. The multi-period approach incorporates both Heat Upgrading Technologies (HUTs) and conventional Distributed Energy Ressources (DER). Temperature requirements of heating and cooling demands are addressed explicitly and fluctuating ambient temperatures are considered, this gives rise to the possibility of temperature dependent modeling of technology efficiencies. The model enables the planner to consider waste heat recovery from hot process streams or from refrigeration cycles via direct heat integration or HUTs, such as mechanical heat pumps. Furthermore, it enables the planner to evaluate the complex interactions of HUTs with Combined Heat and Power (CHP) plants. To illustrate the practicability of the presented modeling approach, it is applied to a real-world case study. Furthermore, we exemplify how the optimal design is adjusted if HUTs and DER are investigated integrally in contrast to an isolated optimization.

Decentralized optimization of coordinated electrical and thermal generations in hierarchical integrated energy systems considering competitive individuals

Along with the popularity of distributed energy generations and hybrid energy appliances, the optimization of integrated energy system combining various kinds of energy has drawn more and more attention. In this paper, we establish a hierarchical model of integrated energy system, which composes of fundamental units such as energy converters, supply networks, and consumers. The fundamental units are modeled as individuals which operate independently and interact with others through mutual information. The fundamental units constitute low-level systems and the combinations of low-level systems make up high-level systems. In order to protect the information privacy of each individual and make full use of the limited mutual information, a decentralized optimization method is presented to optimize the operation strategy of the hierarchical system considering competitive activities between individuals. The individuals participate in an iterative process, interacting with others through an energy pricing mechanism until the system equilibrium achieved. Simulation studies are conducted on several integrated energy systems to investigate the performance of the proposed hierarchical model and decentralized optimization of coordinated electrical and thermal generations. Furthermore, the proposed method is applied to a practical case of Guangzhou Higher Education Mega Center, and the daily operation strategy of the energy supplier is optimized.

Combined use of biogas from sanitary landfill and wastewater treatment plants for distributed energy generation in Brazil

Biogas is a fuel which has a high potential energy and it is produced from the anaerobic degradation of organic material. It can be used for many applications such as heat and electrical generation and fueling vehicles. Given that anaerobic reactors and landfills are the main forms for treating domestic solid waste in Brazil, this current article presents a five scenario analysis on the energy potential and economic viability of the combined use of biogas produced in these structures for generating electricity in the city of Itajubá, Brazil. From the energy point of view, the best case scenario is the combined use of biogas from sanitary landfill and sewage treatment station. This scenario resulted in an installed power of 685 kW, with an annual energy production capable of supplying approximately 10% of the city’s energy. Concerning the economic aspect, the best option is the use of biogas from sanitary landfill in an isolated manner, due to the shorter distance of the transport of the gas, in comparison with other scenarios. The results demonstrate the potential and possibility of economic viability for the use of biogas in urban structures for these microregions in Brazil, indicating that the development of biogas use in small cities can be accomplished within the resolutions of distributed microgeneration. Such potential tends to increase as basic sanitation grows throughout the country.

Energy Harvester from Waste Heat using Thermoelectricity

Currently there are many methods available to harvest energy from renewable sources. However, the method to harvest energy from waste heat sources still not fully explored. This paper focused on using thermoelectricity as a main component to utilized waste heat from household appliance especially from air conditioning system. The objective of this paper is to develop a thermoelectric generator system (TEG) based on heat release from compressor of the air conditioner system. Experimental data input was acquired from the compressor of the air conditioner system includes hot and cold side temperature. Then, Matlab SIMULINK has been used as a tool to analyse the acquired input data and output voltage, while current and power was calculated from the model. As result, maximum voltage obtained from the TEG system are 3.44 V with the temperature difference of 77.6 K at 16 °C, 0.73 A current, while power produced at 1.62 W. In conjunction to the power produced, the waste heat from air-conditioning system could light up the bulb in a room with the energy harvested using thermoelectric principle. The TEG system can also be utilize as an alternative energy sources for distributed energy generation (DEG) application.

Overview of distributed energy storage for demand charge reduction

ABSTRACT

Feasibility study on the low temperature district heating and cooling system with bi-lateral heat trades model

A Novel low temperature district heating and cooling system with auxiliary heat storage pipe system is proposed for reflecting new features of bi-lateral energy trades effectively in emerging energy prosumer based new energy business platform. The newly proposed district heating and cooling system can provide more favorable operating conditions to implement bi-lateral heat trades system between the heat supplier and the prosumers, who operating their own distributed energy generation unit such as a cogeneration etc., connected to the network being able to utilize low-exergy level of waste heats available in consumer side. In this study, the appropriate system configuration for reliable operation, the optimal operation rules, the functionality of auxiliary heat storage pipe on bi-lateral heat trades and its operating characteristics etc. are analyzed extensively by developing simplified simulation models of the DHC network using Matlab/Simulink without any support by experiment or field measurement. The simulation results show that the newly suggested low temperature DHC system with auxiliary heat storage pipe can add improved rooms of operating flexibility to maintain stable supplying temperature conditions and is superior to conventional system in handling bi-lateral heat trades model. It is also shown that the new concept of DHC system can alleviate the inefficiency arising from mismatching of heat demand and supply in consumer side significantly, not to mention of the heat losses during the operation.

Mitigating Household Energy Poverty through Energy Expenditure Affordability Algorithm in a Smart Grid

One of the criteria for measuring household energy poverty is the percentage of the household’s income spent on energy expenses. In this work, an autonomous income-based energy scheduling demand side management (DSM) technique called energy expenditure affordability algorithm (EEAA) is proposed to ensure that household energy expenditure is below the nation’s approved energy expenditure threshold. The EEAA problem was formulated as a mixed integer linear programming (MILP) problem and verified with real household data collected from families living in bachelor flats in Johannesburg, South Africa. Consumer preferences and satisfaction were enhanced by using the dynamic time warping (DTW) technique to minimize the distance between nominal and EEAA load profiles. Furthermore, the effects of distributed energy generation (DEG) and distributed energy storage (DES) were also investigated in light of energy expenditure affordability for improved consumer-friendly and satisfying DSM. The EEAA-DSM technique is shown to reduce household energy expenditure below the energy expenditure threshold, offering energy expenditure affordability as well as utility grid peak demand reduction (PDR). Furthermore, grid reliability and sustainability, environmental preservation and gendered energy poverty are consequential benefits of the EEAA. It also offered the households considered an average financial savings from 12% to 82%, depending on the level of implementation of distributed storage and generation to the consumer’s local energy mix.

Post evaluation of distributed energy generation combining the attribute hierarchical model and matter-element extension theory

Abstract Distributed energy supply has a prominent impact on solving the contradiction between energy supply and demand, environmental degradation, and other issues. This paper analyzes the application of distributed energy supply for specific power projects. We developed a systematic post project evaluation index and evaluation model using the theory of matter-element extension, and determined weights for all indicators that influenced distributed energy generation projects, combined with the attribute hierarchical model. The proposed model was verified experimentally, and shown to enhance evaluation of distributed generation projects. In addition, (1) Distributed energy systems have been widely applied across the world due to their inherent advantages of flexibility, convenience, environmentally friendliness, and high reliability, so it is necessary to study. (2) This paper combined the matter-element extension theory (MEET) and the attribute hierarchical model (AHM) to develop an evaluation model for distributed generation projects. The proposed model was verified experimentally using actual distributed energy project data. (3) This paper enhances the evaluation theoretical research on the post-evaluation of distributed generation projects and capturing experience and lessons for subsequent projects.

Genetic algorithms to optimize the operating costs of electricity and heating networks in buildings considering distributed energy generation and storage

This paper deals with the optimization of the operating costs of electricity and heating networks in buildings with distributed energy generation and electric storage via batteries and thermal storage for heating. The problem considers distributed energy sources such as electric grid, renewable sources (including thermal, photovoltaic and wind power), boilers, Cooling, Heating and Power (CHP) systems, as well as storage systems as electric batteries and thermal storage. Both electric and heating networks are coupled by the consideration of the CHP that joins both networks, increasing the complexity of the optimization problem and emerging as a critical network element. The objective is to obtain the optimal configuration of energy supply from the energy sources or from the energy storage systems to fulfill the electric and heating demands each 15 min period, which minimizes the operating costs. The proposed mathematical model was firstly solved using Gurobi optimization commercial software that provided a very confident benchmark for the problem. Gurobi provided the optimum in most of the cases within the 15 min slot, but for specific instances the optimum could not be obtained in such slot. We implemented two genetic algorithm approaches differencing the crossover genetic operator: a basis genetic algorithm (BGA) and a segmented genetic algorithm (SGA). Both genetic algorithm implementations provided appropriate results within the time slot when compared to the benchmark. However, SGA provided better solutions than BGA considering both time convergence and quality of solutions appearing as an appropriate approach for solving real life cases. The system was successfully implemented at the premises of the School of Engineering of the University of Seville.

A discrete particle swarm optimisation algorithm to operate distributed energy generation networks efficiently

This paper deals with the optimisation of the operating costs in a distributed electric and heating energy generation network. The network considers different options to supply the electric and heating demand of a large consumer building: the electricity can be directly bought from the grid, can be taken from renewable energy sources or can be produced from gas using a combined heat and power system. In the same line, the heating can be taken from a thermal solar renewable system, from the boiler or from the combined heat and power system. In addition, the large consumer has batteries to store electricity excesses and thermal storage systems to store the heating excess. The multicommodity flow mathematical formulation of the problem couples both electric and thermal models by considering cogeneration systems. The model is solved by a particle swarm optimisation (PSO) algorithm that is compared to the optimal solutions provided by Gurobi optimisation commercial software and a Monte Carlo algorithm. The PSO algorithm proved a very efficient performance in the available short time to provide the energy commands to the systems outperforming the alternative approaches.

A discrete particle swarm optimisation algorithm to operate distributed energy generation networks efficiently

A discrete particle swarm optimisation algorithm to operate distributed energy generation networks efficiently

Direct-Drive Conical-Rotor Permanent Magnet Synchronous Generator for Turbo-Expander, Accounting for Adaptive Equilibrium of Axial Force

The permanent magnet synchronous generator (PMSG) has been widely employed in high-speed direct-drive turbo-expander for distributed energy generation. However, for conventional PMSG based turbo-expander system, expensive mechanical balance devices should be installed on the rotor to restrain the axial force of turbine impeller under high-speed flow, which may cause both complex system structure and higher manufacturing cost. Thus, in this paper, a direct-drive conical-rotor PMSG (CR-PMSG) for turbo-expander is developed, which can generate an axial magnetic force as equilibrant to counteract the axial force of turbine impeller without mechanical balance device, so as to reduce the system complexity, improve the operating performance and extend the operating cycle. First, the structural features of the CR-PMSG are introduced and the basic principle of axial force balance is analyzed. Then, a 1.5 kW, 6000 rpm CR-PMSG with cone angle of 6° is designed. Using 3-D finite element analysis, the axial force of turbine impeller, the axial magnetic force of the rotor, and the electromagnetic performance are simulated. Also, the control strategy of d, q-axis currents is obtained to achieve the adaptive equilibrium of axial force. Finally, a CR-PMSG prototype is fabricated and tested to validate the theory.

The research of the schemes of regional distributed energy system

The distributed energy generation system is one of the main forms of the second-generation energy system currently. Three kinds of viable schemas of distributed energy supply system for nine users of the small region heat of Yangpu area combining with urban heating were proposed in this thesis, in which the gas turbines were selected. By analyzing the heat economy and pollutant emissions, the advantages and disadvantages of each schema were found out and the relatively better one was selected ultimately. Finally, some possible development trends and the prospects of the distributing energy supply system were also related and some complementary proposals were to table for some aspects of the system.

PHIL Test Bench for Online-Identification Methods of Complex Power Grid

Power generation is shifting towards renewable and distributed energy production due to increased awareness of climate change and the recent advancements in renewable technologies. Distributed energy generation typically consists of wind and solar power plants, virtually all of which are connected to power grid by an inverter. As a consequence, the stability issues generated by the active power electronic devices are continuously increasing. The increased requirements for the functionality of the grid-connected inverters require a sophisticated test bench for experimentation. Power hardware-in-the-loop methods allow combining of the simulations to actual hardware, and thus, enable running experiments on real devices in time-varying conditions. This paper presents the use of a power hardware-in-the-loop test bench for stability studies of grid-connected systems. Experimental MIMO measurements based on pseudo-random sequences injected with a three-phase grid-connected inverter are presented and used to demonstrate the effectiveness of the proposed method.

A method for the identification of low frequency oscillation modes in power systems subjected to noise

The high penetration of renewable energy sources and the consequent integration of such distributed energy generation systems into the grid have significantly increased the interaction between power sources, which can result in low frequency oscillations. Different control techniques are proposed in literature to suppress low frequency oscillations, but the first step to attenuate such oscillations is to characterize them in terms of their dominant modes. This paper combines different results from literature to propose a unified two-step methodology for the mode characterization of low frequency oscillations based on the signals acquired by wide area measurement systems. Since the measured signals typically contain noise, the first stage of the proposed method uses the basis pursuit denoising method combined with a Tunable Q-factor wavelet transform to increase the signal-to-noise ratio and improve the identification results. In a second stage, an improved version of the matrix pencil algorithm, as proposed in this paper, is used to identify the parameters of low frequency oscillation dominant modes. Both simulation and experimental results show that the proposed method has better characterization accuracy than traditional methods, especially when Gaussian noise is considered in the measurements. In addition, the processing time has proven to be reasonable for online identification and characterization of low frequency oscillations.

Utilization of Constrained Urban Spaces for Distributed Energy Generation – Development of Solar Paved Pedestrian Walkway

Distributed energy generation is a challenge in urban areas. Conventional solar systems cannot be installed in cities (rooftop space is limited) and there is need for innovative, dual-purpose designs like BIPV, car-ports and solar walkways. Smart cities of the future would rely heavily on this philosophy. One such system design is presented in this paper that incorporates several novel concepts - solar panels on an elevated structure that generates electricity and provides shelter to pedestrians from the environment, takes care of module cleaning by an automated water management system and harvests rain water. The use of micro-inverters increases energy generation from the system and also reduces issues with shading and pedestrian safety. A pilot of the proposed design is being commissioned at a favourable location in India and analysis of the data obtained will form the basis of future development of solar system design for constrained urban spaces.

(Invited) Role of Ion-Conducting Membranes in Synthesis and Use of Sustainable Fuels

Replacement of conventional catalytic technologies for synthesis of sustainable, carbon-neutral fuels with direct electrochemical synthesis has a potential for big energy savings due to reduction of number of process steps and pressure/temperature. In addition, electrochemical technologies are easily scaled down to allow for low capital, modular plants that match the scale of renewable energy production. The use of these fuels in electrochemical devices opens a path to cost-effective long-term energy storage and distributed energy generation. Development of low cost, ion-selective membranes with low area specific resistance is, along with electrocatalyst development, critical for the success of such technologies. Not less important is development of membrane manufacturing methods at a practical scale. This presentation will review prospective technologies using ion-selective membranes for synthesis of carbon-neutral fuels for chemical energy storage and their use for generation of electricity (using fuel cells) and hydrogen. Advantages of electrochemical synthesis of ammonia from nitrogen and hydrogen or water compared to the conventional Haber-Bosch process will be discussed. Other processes include direct electrochemical synthesis of alcohols from CO2. The requirements to ion-selective membranes for these processes and fuel cells will be presented. The Advanced Research Projects Agency (ARPA-E) funds high risk, high reward transformational research to reduce energy related emissions, reduce imports of energy from foreign sources, improve energy efficiency across all economic sectors, and ensure US technological lead in advanced energy technologies, including electrochemical energy storage and transformation for grid scale and automotive applications. The Renewable Electricity to Fuels through Utilization of Energy-dense Liquids (REFUEL) program funds the development of transformational technologies to reduce the barriers to widespread adoption of intermittent renewable energy sources by enabling the conversion of energy from these sources, water and air to energy-dense zero-carbon liquid fuels and their use for electricity or hydrogen generation. REFUEL projects targeting various ion conducting membranes as well as related projects supported by ARPA-E through OPEN program will be highlighted.

Distributed generation of electric energy in traction power-supply systems of railways based on wind-power plants

The assessment of the possibility to use the potential of wind energy for power supply of the traction railway network in the context of the area of Karatau in the southern region of the Republic of Kazakhstan, the main wind-energy characteristics of the region are determined. An comparison of the program is presented with the results of statistical processing of the data sets on the long-term monitoring of the wind indicators of the investigated region with wind-speed determination during a month, mathematical expectations, law of the probability density of wind-speed distribution for a month, diagrams of wind distribution according to days within a month, instantaneous values (gusts) of wind speed for 24 h, and average wind speed by time of day for a month. A diagram of a traction power-supply system with distributed energy generation is given based on wind-power plants, their equivalent circuit and design including the wind generators, rectifying and inverting converter units, as well as the electric-energy accumulator with the direct current converter. Theoretical dependences are obtained to determined additional electric-energy losses in the traction network during redistribution of energy in the traction power-supply system from the main traction substations to energy-storage units at the “wind” traction substations during periods of an unfavorable wind situation in the region. The operation regimes of the electric-power facilities incorporated into the traction powersupply system and “wind” traction substations are described taking into account the pure traction mode from the wind electricity generator, power supply of trains from energy-storage units under conditions of the insufficient wind force, and energy-recovery regimes during braking of the trains, as well as with qualitative determination of their operating parameters. The main electrical characteristics of the equipment of the “wind” traction substations are determined.