Dynamic Simulation and Optimization of an Experimental Micro-CSP Power Plant

2015 ◽  
Author(s):  
Matthias Mitterhofer ◽  
Matthew Orosz
Keyword(s):  
Control Strategy ◽  
Low Cost ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Economic Benefits ◽  
Solar Thermal ◽  
Small Scale ◽  
Pinch Point ◽  
Simulation And Optimization ◽  
Dynamic Representation

Small scale solar thermal systems are increasingly investigated in the context of decentralized energy supply, due to favorable costs of thermal energy storage (TES) in comparison with battery storage for otherwise economical PV generation. The present study provides the computational framework and results of a one year simulation of a low-cost pilot 3kWel micro-Concentrated Solar Power (micro-CSP) plant with TES. The modeling approach is based on a dynamic representation of the solar thermal loop and a steady state model of the Organic Rankine Cycle (ORC), and is validated to experimental data from a test site (Eckerd College, St. Petersburg, Florida). The simulation results predict an annual net electricity generation of 4.08 MWh/a. Based on the simulation, optimization studies focusing on the Organic Rankine Cycle (ORC) converter of the system are presented, including a control strategy allowing for a variable pinch point in the condenser that offers an annual improvement of 14.0% in comparison to a constant condensation pinch point. Absolute electricity output is increased to 4.65 MWh/a. Improvements are due to better matching to expander performance and lower condenser fan power because of higher pinch points. A method, incorporating this control strategy, is developed to economically optimize the ORC components. The process allows for optimization of the ORC subsystem in an arbitrary environment, e.g. as part of a micro-grid to minimize Levelized electricity costs (LEC). The air-cooled condenser is identified as the driving component for the ORC optimization as its influence on overall costs and performance is of major significance. Application of the optimization process to various locations in Africa illustrates economic benefits of the system in comparison to diesel generation.

1-D Model Analysis of Tesla Turbine for Small Scale Organic Rankine Cycle (ORC) System

2017 ◽  
Author(s):  
Jian Song ◽  
Chun-wei Gu
Keyword(s):  
Large Scale ◽  
Low Cost ◽  
Organic Rankine Cycle ◽  
Axial Flow ◽  
Rankine Cycle ◽  
Expansion Ratio ◽  
Working Fluid ◽  
Small Scale ◽  
Low Grade ◽  
D Model

Energy shortage and environmental deterioration are two crucial issues that the developing world has to face. In order to solve these problems, conversion of low grade energy is attracting broad attention. Among all of the existing technologies, Organic Rankine Cycle (ORC) has been proven to be one of the most effective methods for the utilization of low grade heat sources. Turbine is a key component in ORC system and it plays an important role in system performance. Traditional turbine expanders, the axial flow turbine and the radial inflow turbine are typically selected in large scale ORC systems. However, in small and micro scale systems, traditional turbine expanders are not suitable due to large flow loss and high rotation speed. In this case, Tesla turbine allows a low-cost and reliable design for the organic expander that could be an attractive option for small scale ORC systems. A 1-D model of Tesla turbine is presented in this paper, which mainly focuses on the flow characteristics and the momentum transfer. This study improves the 1-D model, taking the nozzle limit expansion ratio into consideration, which is related to the installation angle of the nozzle and the specific heat ratio of the working fluid. The improved model is used to analyze Tesla turbine performance and predict turbine efficiency. Thermodynamic analysis is conducted for a small scale ORC system. The simulation results reveal that the ORC system can generate a considerable net power output. Therefore, Tesla turbine can be regarded as a potential choice to be applied in small scale ORC systems.

Novel Parabolic Trough Collectors Driving a Small-Scale Organic Rankine Cycle System

2007 ◽  
Author(s):  
P. Kohlenbach ◽  
S. McEvoy ◽  
W. Stein ◽  
A. Burton ◽  
K. Wong ◽  
...  
Keyword(s):  
Steel Substrate ◽  
Low Cost ◽  
Sheet Steel ◽  
Organic Rankine Cycle ◽  
Glass Tube ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Small Scale ◽  
Inlet Temperature ◽  
Parabolic Trough

This paper presents component performance results of a new parabolic trough collector array driving an organic Rankine cycle (ORC) power generation system. The system has been installed in the National Solar Energy Centre at CSIRO Energy Technology in Newcastle, NSW, Australia. It consists of four rows of 18 parabolic mirrors each in a 2×2 matrix with a total aperture area of approximately 132m2. The absorber tube is a laterally aligned, 40mm copper tube coated with a semi-selective paint and enclosed in a 50mm non-evacuated glass tube to reduce convection losses. The mirror modules, which are light-weight and robust, are made from thin low iron back silvered glass bonded to a sheet steel substrate. They are supported by a box truss on semi circular hoops running on rollers for single axis tracking. The mirror design has been chosen to allow low-cost manufacturing as well as simple commissioning and operation. The ORC unit is a FP6 unit sourced from Freepower Ltd. with a net power output of 6kWel at 180°C inlet temperature and a total heat input of 70 kWth. It uses a two-stage expansion process with hydrofluoroether as the working fluid. A wet cooling tower is used to dissipate the reject heat from the ORC. The two key components of the envisioned system are the trough reflector/receiver and the ORC unit. The optical performance of the mirror elements was investigated with regard to the flux mapping onto the receiver tube. The ORC unit has been tested separately using an electrical oil heater as the heat source. This paper presents results for irradiation capture and intensity over the receiver width of a single trough mirror module. The complete system including trough collectors and ORC has not been in transient operation yet, thus experimental steady-state results of the ORC unit are presented.

Study of a Lab-Scale Organic Rankine Cycle for the Ultra-Low-Temperature Waste Heat Recovery Associated With Data Centers

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Sebastian Araya ◽  
Aaron P. Wemhoff ◽  
Gerard F. Jones ◽  
Amy S. Fleischer
Keyword(s):  
Data Center ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Data Centers ◽  
Waste Heat ◽  
Low Cost ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Economic Benefits ◽  
Fluid Temperature

Abstract The ongoing growth in data center rack power density leads to an increased capability for waste heat recovery. Recent studies revealed the organic Rankine cycle (ORC) as a viable means for data center waste heat recovery since the ORC uses waste heat to generate on-site, low-cost electricity, which can produce economic benefits by reducing the overall data center power consumption. This paper describes the first experimental and theoretical study of a lab-scale ORC designed for ultralow grade (40–85 °C) waste heat conditions typical of a data center server rack, and it outlines the implementation of a similar ORC system for a data center. The experimental results show thermal efficiencies ranging from 1.9% at 43 °C to 4.6% at 81 °C. The largest contributors to ORC exergy destruction are the evaporator and condenser due to large fluid temperature differences in the heat exchangers. The average isentropic efficiency of the expander is 70%. A second-law analysis estimates a reduction of 4–8% in data center power requirements when ORC power is fed back into the servers at a waste heat temperature of 90 °C. The data from the lab-scale experiment, when complemented by the thermodynamic model, provide the necessary first step toward advancing this type of waste heat recovery for data centers (DCs).

Efficiency Enhancement of a Small Scale Closed Solar Thermal Brayton Cycle by a Combined Simple Organic Rankine Cycle

2012 ◽  
Author(s):  
H. Riazi ◽  
N. A. Ahmed
Keyword(s):  
Power Output ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Solar Thermal ◽  
Small Scale ◽  
Brayton Cycle ◽  
Efficiency Enhancement ◽  
Power Cycles ◽  
Micro Turbine ◽  
Net Power Output

In this paper efficiency enhancement of a small scale closed solar thermal Brayton cycle is investigated by combining it to a simple organic Rankine cycle. Brayton power cycles are generally known as the enabling technology for high temperature solar power towers due to their higher efficiencies compared to other power cycles. Unlike conventional solar-thermal plants, which concentrate the sun’s energy to generate steam for driving a turbine, the Brayton thermodynamic does not use water. Instead, the concentrated solar energy is used to heat compressed air, which then expands through a gas turbine to generate power. Irreversible loss in compressor and turbine, the operating temperature of solar collector and recuperator effectiveness are the main features that limit the net power output of the system which should be considered and analyzed. The exhaust of the gas turbine is still at high temperature that should be cooled down before entering the compressor. Thus, this heat can be utilized to operate a low temperature Rankine cycle and increase the system efficiency and power generation. Operating points of off the shelf micro-turbines and steam turbine with parabolic solar dish concentrator of various concentrating ratios are considered. Thermodynamic analysis is applied, by using the first and second law of thermodynamics, to obtain the optimum temperature of solar collector, minimum irreversibility rates to maximize the efficiency and net power output of the system at various steady-state conditions. Results show that for the closed solar thermal Brayton cycle the maximum overall first law efficiency of the system can be increased of more than 5% by combining a simple Rankine cycle to recover the exhaust heat and a significant 20% increase in the second law efficicency. The system efficiency is related to the solar concentration ratio with an optimum operating temperature and the choice of micro-turbine. On this basis, both the overall efficiency and the total output power may reach their maximum value by optimizing the pressure ratio. In a small scale closed solar thermal Brayton cycle combined by a Rankine cycle with a micro turbine operating at its highest compressor efficiency, the operating conditions can be optimized in such a way that the system produces maximum net power output or having the highest overall efficiency.

scholarly journals Energy, exergy, and environmental assessment of a small-scale solar organic Rankine cycle using different organic fluids

Heliyon ◽  
2021 ◽  
Vol 7 (9) ◽  
pp. e07947
Author(s):  
Geanette Polanco Piñerez ◽  
Guillermo Valencia Ochoa ◽  
Jorge Duarte-Forero
Keyword(s):  
Environmental Assessment ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Small Scale ◽  
Organic Fluids

Dynamic Simulation of an Organic Rankine Cycle (ORC) System Driven by Exhaust

2015 ◽  
Vol 738-739 ◽  
pp. 986-990
Author(s):  
Zhi Gang Wang ◽  
Jia Guang Cheng ◽  
Yan Wang ◽  
Qiang Shen
Keyword(s):  
Low Temperature ◽  
Control Strategy ◽  
Fossil Fuels ◽  
Moving Boundary ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Energy Crisis ◽  
Transient Phenomena ◽  
Simulation Results ◽  
Boundary Model

Organic Rankine Cycle (ORC) is one of the most promising technologies for low-temperature energy conversion. In recent years, it has gotten more attention due to the energy crisis and environmental problems caused by the combustion of fossil fuels. In this paper, a moving boundary model is introduced to describe the transient phenomena of evaporator and condenser, which are the important components of ORC. The simulation results are given to illustrate the efficiency and feasibility of the proposed control strategy.

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