Microturbine Model Research Articles

Wind Microturbine with Adjustable Blade Pitch Angle

The article presents the results of research on the operation of a wind microturbine model with an adjustable blade pitch angle. The physical basics of wind turbine operation and the methods of its optimal control are discussed. The results of the measurements carried out for the selected blade geometry with the possibility of adjusting the pitch angle are presented. The tests were carried out for a resistive load with a linear characteristic and for a load with a non-linear characteristic of a Li-Po battery. The results of the operation of a simple MPPT control algorithm are presented. The practical methods of controlling larger wind turbines are not optimal for small and very small turbines. The conducted research focused on determining the possibility of using blades with an adjustable angle setting, depending on the rotational speed in wind microturbines. The use of a simple mechanism for changing the pitch angle of the blades depending on the rotational speed of the turbine can increase the efficiency of the microturbine in a wider range of wind speeds.

Dynamic Interactions between Local Energy Systems Coupled by Power and Gas Distribution Networks

Supplied with electricity and natural gas, local energy systems (LESs) with gas-fired generations increase the operational flexibility of urban energy supply. However, the increasing usage of these LESs may lead to adverse impacts on the urban energy system supply via power and/or gas distribution networks. Dynamic interactions between the LESs, electricity, and gas networks subject to different disturbances need to be investigated due to the complexity of the problem. To address this issue, this paper first presents the topology and operating mode of the LESs as well as the relationship with power and gas networks. Second, an extended microturbine model is developed to reflect the nonlinear dynamic propagation of disturbances between the two networks. A general model of the interconnected LESs is developed to analyze the mutual impacts between gas and electricity networks under different modes. Finally, an iterative method is proposed to simulate the mechanism of disturbance propagation between the electricity network, gas network, and LESs, incorporating the impacts of loads and renewables. Case studies reveal that simultaneous regulation of multiple gas-fired generators would reduce the minimum pressure to 50% of the steady-state value. The resulted pressure drop is even lower than the case with higher total gas demand but only one gas-fired generator regulated. Moreover, it is shown that state fluctuations of the gas system last 20 times longer than the electricity system within the LESs. The electrical link between LESs, such as soft opening point with shorter response time, could smooth the fluctuations.

Off-design modeling of a microturbine combined heat & power system

There is increasing interest in decision support software tools that evaluate the techno-economic potential of distributed energy system technologies for deployment in combined heat and power (CHP) applications, such as commercial buildings, microgrids, and connected communities. This trend is particularly evident among end-users looking to integrate renewable resources with more traditional CHP technologies for on-site generation and enhanced resiliency. However, many of these software tools do not account for part-load and off-design characteristics of prime mover and heat recovery equipment, resulting in lower accuracy for both the optimal selection and sizing and the economic value proposition of integrated hybrid renewable energy-CHP systems. Microturbine technology is an attractive distributed energy resource whose performance is sensitive to both part-load and off-design (i.e., excursions of ambient conditions away from the design point temperature and pressure) operating conditions but is widely unreported. In the present work, we address this deficiency by developing a detailed, thermodynamic model of a commercial 200 kW microturbine CHP system and paramaterizing results for incorporation into the Renewable Energy Optimization (REopt) tool developed by the National Renewable Energy Laboratory. The details of the microturbine model, including model benchmarking and validation, are presented. Microturbine off-design modeling includes part-load analysis, assessment of ambient sensitivities, and mapping heat recovery heat exchanger response to hot water grade requirements. The model is then exercised in several illustrative examples to depict the numerous factors which alter electric power, electric efficiency, and hot water recovery. Model results show, for example, predictions of a 4 percentage point electric efficiency range occurring between intake air temperatures of -18 to 50 °C. Likewise, the model closely predicts the 25 % loss in heat recovery while at -18 °C and the 8 % gain in heat recovery while at 35 °C. An additional case shows how heat recovery may increase or decrease by 9.5 % of the design value when changing the return water temperature plus-or-minus 22 °C. In particular, the impact of ambient conditions on best-possible microturbine performance is conveyed through hourly simulations of the system subjected to the weather of different geographic locations within the United States. • A model of a 200 kW microturbine configured for hot water recovery is developed. • Part-load modeling approach and simulation results for both electric efficiency and waste heat recovery are detailed. • Off-design performance as functions of ambient temperature and pressure is explored. • Heat recovery performance maps as functions of return and supply hot water temperatures are developed.

Effect of Thermal Barrier Coating on the Thermal Stress of Gas Microturbine Blades and Nozzles

Thermal barrier coatings play a key role in the operational life of microturbines because they reduce thermal stress in the turbine components. In this work, numerical computations were carried out to assess new materials developed to be used as a thermal barrier coating for gas turbine blades. The performance of the microturbine components protection is also evaluated. The new materials were 8YSZ, Mg2SiO4, Y3Ce7Ta2O23.5, and Yb3Ce7Ta2O23.5. For testing the materials, a 3D gas microturbine model is developed, in which the fluid-structure interaction is solved using CFD and FEM. Temperature fields and stress magnitudes are calculated on the nozzle and blade, and then these are compared with a case in which no thermal barrier is used. Based on these results, the non-uniform temperature distributions are used to compute the stress levels in nozzles and blades. Higher temperature gradients are observed on the nozzle; the maximum temperature magnitudes are observed in the blades. However, it is found that Mg2SiO4 and Y3Ce7Ta2O23.5 provided better thermal insulation for the turbine components compared with the other evaluated materials. Mg2SiO4 and Y3Ce7Ta2O23.5 presented the best performance regarding stress and thermal insulation for the microturbine components. Keywords: thermal barrier coating, gas microturbine, turbine blade, thermal stress

Hydrodynamic water tunnel for characterization of hydrokinetic microturbines designs.

The enormous inroads made by renewable energy in recent years have been the key to the development of new technologies designed to obtain energy from a range of resources. Hydrokinetic microturbines used to harness kinetic energy from rivers, tidal and marine currents epitomize such developments. As the reservoir is dispensed with, the water footprint normally associated with conventional hydroelectric generation is minimized. The new prototypes being developed require laboratories with water tunnel infrastructures where they can be accurately reproduced under controlled conditions. However, the construction of a water tunnel demands considerable investment, which prevents many research groups from completing their prototype design work. This paper charts the design of a low-cost hydrodynamic water tunnel at the University of Oviedo, indicating the mechanical and electronic elements as well as the software developments that make up the facility. This construction is a part of a research strategy focused on making the study of new hydrokinetic microturbines designs economically feasible. Moreover, it includes a description of a special software application used to perform the characterization of a hydrokinetic microturbine model in the water tunnel and a demonstration of the scope of the facility in the experimental study of a unit with a Darrieus rotor.Graphic abstract

Industrial integrated energy system optimization with considering thermal power transferring process

In the regional integrated energy system, multiple resources on the demand side and supply side should be considered in integrated planning. In particular, how to realize measuring heat energy grade as well as considering thermal energy transferring medium characteristics in the integrated energy system optimization operation and resource allocation is a urgent research area to explore. In this paper, a typical industrial park integrated energy system considering thermal energy transferring process is established. In the beginning, multi-energy flows complementary characteristics of the industrial park have been introduced, which could improve energy usage efficiency by energy conversion, energy storage and energy substitution. Then the models of storage battery, micro-turbine and other resources have been established. In addition, the model of heat energy pipe network has been built considering thermal energy unidirectional transmission and various heat grade. Based on the previous models, the objective function of industrial park economic operation. Finally, the simulation results show that the proposed multi-energy flows model could satisfy the economical operation as well as energy supply balance while obeying energy conservation law and transferring process limit.

Dynamic modeling gas-electricity combined system with wind power and its stability control method

The micro turbine (MT) is scheduled to catch up wind power uncertainty and thus lead to great variations in the state of natural gas system (NGS). To meet this challenge, firstly, a dynamic model of gas-electricity combined system with wind power is established, the dynamic model of NGS is based on differential equations, so that it can connect with MT model easily, and a droop control module is added to the Rowen's MT model, so that the improved model can adjust the output power according to the scheduling instructions. Then, a stability control method based on the variable regulation ratio gas pressure regulator is proposed, the essence of this method is to reduce the variation of natural gas storage in the gas pipeline, so as to ensure the stability of pressure. The simulation results show that the dynamic model is correct and the stability control method is effective.

Optimized FOPID controller for improving steady state and transient response of Microturbine Generation system

The power system structure is complicated and the demand is increasing rapidly. In order to minimize the power losses and to reduce the power shortage, Distribution Generation (DG) is added in the power system. Microturbine Generation (MTG) is a new type of DG which has become popular source of electric power industries due to their fuel flexibility, reliability, power quality and its size. In this paper, the modelling and simulation analysis of the MTG system are carried out with Fractional Order Proportional Integral Derivative (FOPID) controller to improve the overall performance of MTG system. The performance of the MTG system is studied under various linear and non-linear load conditions. The Microturbine model and converter controller models are simulated using MATLAB Software. FOPID controller is used to maintain constant voltage for various load conditions by maintaining the torque of the Microturbine (MT) system. The power quality of MTG system is analyzed using Fast Fourier Transform (FFT) Analysis. To improve the power quality, LCL filter is added in this paper. The overall performance of MTG system is analyzed with and without FOPID controller. When the results are compared with conventional PI controller, the MTG system shows better performance in FOPID controller.

A model development and experimental verification for a vapour microturbine with a permanent magnet synchronous generator

Vapour microturbines with permanent magnet synchronous generators are implemented in micropower plants for dispersed power generation systems. The dynamic model of such a microturbine set was developed and presented. The developed relations result from the generic equations. Experimental data for two different working medium were used for model verification. A microturbine set model was tested during the changes in the parameters of a working medium or an electrical load. Examples of a comparison between the experimental results and simulations are shown and discussed. The developed model ensures comparable accuracy as gas microturbine models found in the literature. In the case of vapour microturbine sets, in addition to accuracy, provides a larger area of operation. An operation during a start-up process was also analysed. Due to model simplifications, the accuracy decreases for a start-up operation from a cold state. The developed model can be a useful tool for some engineering applications or for studying the various operational aspects of vapour microturbines with permanent magnet synchronous generators.

Life cycle-based enviroeconomic and thermal analyses of the inlet air-cooled microturbine systems with liquefied natural gas cold energy

Liquefied natural gas cold utilization systems are used in the processes of three different inlet air-cooled microturbine systems to investigate the overall performances with respect to the life cycle-related enviroeconomic and thermal approaches as new defined aspects. The inlet air cooling applications increase the thermal efficiency and the power generation rate roundly by 3.2 and 7.7%, respectively, while the payback period of the inlet-air cooled system is closely higher than the conventional case. The life cycle-based environmental payback periods of the inlet air-cooled systems are found 3.25, 7.77, and 6.16% less than the conventional systems since the inlet air cooling applications achieve 3.25, 2.54, and 2.47% emission reductions of 30, 65, and 200 kW microturbine models, respectively. The integration of the life cycle assessment parameters increases the classical enviroeconomic parameters roundly by 100%. Moreover, different electricity and gas prices are studied to have more reliable data about the real engineering applications of the proposed systems. India, USA and Mexico are selected as the LNG importer countries for the case studies, and it is seen that the cold energy based inlet air cooling applications are more commercially viable for the regions where the fuel costs are relatively high whereas the systems become unfeasible with the low electricity prices.

Identification of microturbine model for long-term dynamic analysis of distribution networks

As one of the most successfully commercialized distributed energy resources, the long-term effects of microturbines (MTs) on the distribution network has not been fully investigated due to the complex thermo-fluid-mechanical energy conversion processes. This is further complicated by the fact that the parameter and internal data of MTs are not always available to the electric utility, due to different ownerships and confidentiality concerns. To address this issue, a general modeling approach for MTs is proposed in this paper, which allows for the long-term simulation of the distribution network with multiple MTs. First, the feasibility of deriving a simplified MT model for long-term dynamic analysis of the distribution network is discussed, based on the physical understanding of dynamic processes that occurred within MTs. Then a three-stage identification method is developed in order to obtain a piecewise MT model and predict electro-mechanical system behaviors with saturation. Next, assisted with the electric power flow calculation tool, a fast simulation methodology is proposed to evaluate the long-term impact of multiple MTs on the distribution network. Finally, the model is verified by using Capstone C30 microturbine experiments, and further applied to the dynamic simulation of a modified IEEE 37-node test feeder with promising results.

Dynamic Modeling and Interaction of Hybrid Natural Gas and Electricity Supply System in Microgrid

Natural gas (NG) network and electric network are becoming tightly integrated by microturbines in the microgrid. Interactions between these two networks are not well captured by the traditional microturbine (MT) models. To address this issue, two improved models for single-shaft MT and split-shaft MT are proposed in this paper. In addition, dynamic models of the hybrid natural gas and electricity system (HGES) are developed for the analysis of their interactions. Dynamic behaviors of natural gas in pipes are described by partial differential equations (PDEs), while the electric network is described by differential algebraic equations (DAEs). So the overall network is a typical two-time scale dynamic system. Numerical studies indicate that the two-time scale algorithm is faster and can capture the interactions between the two networks. The results also show the HGES with a single-shaft MT is a weakly coupled system in which disturbances in the two networks mainly influence the dc link voltage of the MT, while the split-shaft MT is a strongly coupled system where the impact of an event will affect both networks.

Modelling and Simulation of a Microturbine during Transient Events

This paper deals with the performance of a microturbine connected to a LV grid during different transient events in the network. The study is based on the dynamic modelling of a microturbine and the simulation of different events in the Matlab/Simulink environment. The microturbine model has been validated with the measurements taken in several test of a real 28kW Capstone microturbine.

A Theoretical Solid Oxide Fuel Cell Model for System Controls and Stability Design

As the aviation industry moves toward higher efficiency electrical power generation, all electric aircraft, or zero emissions and more quiet aircraft, fuel cells are sought as the technology that can deliver on these high expectations. The hybrid solid oxide fuel cell system combines the fuel cell with a microturbine to obtain up to 70% cycle efficiency, and then distributes the electrical power to the loads via a power distribution system. The challenge is to understand the dynamics of this complex multidiscipline system and the design distributed controls that take the system through its operating conditions in a stable and safe manner while maintaining the system performance. This particular system is a power generation and a distribution system, and the fuel cell and microturbine model fidelity should be compatible with the dynamics of the power distribution system in order to allow proper stability and distributed controls design. The novelty in this paper is that, first, the case is made why a high fidelity fuel cell model is needed for systems control and stability designs. Second, a novel modeling approach is proposed for the fuel cell that will allow the fuel cell and the power system to be integrated and designed for stability, distributed controls, and other interface specifications. This investigation shows that for the fuel cell, the voltage characteristic should be modeled, but in addition, conservation equation dynamics, ion diffusion, charge transfer kinetics, and the electron flow inherent impedance should also be included.

Use of ARX algorithms for modelling micro-turbines on the distribution feeder

The deregulation of utilities and the emerging power markets are creating renewed interest in operating micro-turbines in parallel with the utility system. As micro-turbines proliferate, it is necessary to reduce the model order of each micro-turbine to enable computational analysis. The application of the autoregression with exogenous signal (ARX) identification algorithm is presented to compute low-order micro-turbine models, suitable for analysis. This algorithm consists of a procedure for calculating the transfer function of a micro-turbine from samples of its input and output. Each micro-turbine reduced-order model influences the grid in the same manner as an actual micro-turbine would, modulating real and reactive power in response to voltage and frequency changes on the grid.