Test Results From a Concentrated Solar Microturbine Brayton Cycle Integration

2011 ◽  
Author(s):  
Brian Dickey
Keyword(s):  
Solar Energy ◽  
Open Loop ◽  
Working Fluid ◽  
Small Scale ◽  
Brayton Cycle ◽  
Test Results ◽  
Market Place ◽  
Initial Development ◽  
Electrical Efficiency ◽  
Concentrated Solar Energy

Capstone Microturbine and Heliofocus Solar Thermal Solutions in a partnership built an open loop Brayton cycle system using a 65 kW Capstone Microturbine and a concentrated solar energy receiver. This system was built for initial development testing to validate the ability to generate electricity on a small scale at high efficiencies using only solar energy as the input. A secondary goal was to demonstrate the ability of the receiver to transfer sun energy into the working fluid of air at efficiencies that would support the target overall system electrical efficiency of 21%. Concentrating Solar Power systems in the 20 kW to 100 kW electrical output power range currently do not exist in the market place today. Demand for this type of power generation is high due to its small footprint per kW of energy produced, its ability to be distributed in small kW increments to meet site demand and space, its relatively high electrical efficiency and its projected low cost per kilowatt of generated electricity. This initial testing was done without the production configuration dish concentrator component and instead a solar tower with a field of Heliostats provided the sunlight to the solar generation system. Test results showed that the receiver met the efficiency goal set forth and that the overall system was capable of producing 25kW of electricity to the electric grid. The receiver efficiency measured was 89% at or near the needed airflow and air temperature levels required by the Microturbine to support an overall system efficiency of 21%. The next step in the development process would be to integrate the development system onto a concentrating solar dish and demonstrate the total conversion efficiency at the target 21% prior to commercialization.

SUNTRACKER

2015 ◽  
Author(s):  
Jon W. Teets ◽  
J. Michael Teets
Keyword(s):  
High Temperature ◽  
Solar Energy ◽  
Electric Power ◽  
Power Electronics ◽  
Turbine Rotor ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Compressor Impeller ◽  
Temperature Application ◽  
Output Electric Power

A SUNTRACKER (illustrated in figure1), is a Concentrating Solar Power (CSP) unit, in the category of solar dish engines. The novel solar dish engine module (shown in figure 2) is designed to provide 10.1kW electric power (measured at the engine output electric power lugs), from a conversion of 21kW solar energy from the solar dish reflective sun light to the high temperature receiver focal point. Total electric power output from the solar dish engine module is attributed to combined cycles, closed brayton cycle (CBC) and a organic rankine cycle (ORC), both of which are hermetically sealed to atmosphere. The CBC engine receives 21kW solar energy from a solar dish, estimated to have 27 square meters (291 square feet) reflective surface area. However, unlike the photovoltaic (PV) units, the SUNTRACKER will provide increased use of available solar energy from sunlight. Concentrated sunlight from the dish will focus on the CBC engine receiver, which in turn heats the working fluid media to as much as 1600F, pending the ratio of solar dish to receiver areas. A specific gas mixture of xenon/helium, with excellent thermodynamic properties is used for the high temperature application. Turbomachinery in the CBC engine has one moving part / assembly (compressor impeller, alternator rotor and turbine rotor), mounted on compliant foil bearings. Reference figure 4 as an example. The engine operates with a compressor impeller stage pressure ratio 1.6, and is recuperated. Electric power, measured at the CBC engine electric power lugs, is 6.4kW. The CBC engine is not new, (a closed Brayton cycle, sealed to atmosphere) [1], [4], [8], [18], [19]. However, the application to extract thermal energy from the sunlight and provide electric power in commercial and residential use is (patented). In addition, to increase the efficiency of solar energy conversion to electric power, waste heat from the CBC engine provides thermal energy to an ORC engine, to generate an additional electrical output of 3.7kW (measured at the output electric power lugs). With use of an ORC system, the size of the radiator (CBC unit) for heat rejection is reduced significantly. Working fluid HFC-RC245fa [10] was selected for the ORC unit, based on the low temperature application. Also, as with the CBC turbomachinery, the ORC rotor assembly has one moving part, comprised of a pump impeller, alternator rotor and turbine rotor. With the two engines combined, total system thermal efficiency is 48% (10.1kW electric power out / 21kW solar energy in). However, power electronics are needed for conversion of high frequency voltage at the engine output electric power leads to 60/50 Hz power, for customer use. Power electronics losses for this machine, debits the power 0.5 kW. Thus total electric power to the customer, as measured at power electronics output terminals, is 9.6kW. With solar energy, from the reflective sunlight solar dish 21kW and measured output power from the power electronics 9.6kW, the conversion of solar energy to useful electric power an efficiency 46% (i.e. 9.6kW / 21kW). In addition, the design does not require external water / liquid for cooling.

Surface Hardening of Steel Using Highly Concentrated Solar Energy Process

1999 ◽  
Vol 121 (1) ◽  
pp. 36-39 ◽  
Author(s):  
A. Ferriere ◽  
C. Faillat ◽  
S. Galasso ◽  
L. Barrallier ◽  
J-E. Masse
Keyword(s):  
Solar Energy ◽  
Surface Hardening ◽  
Solar Furnace ◽  
Small Scale ◽  
Single Spot ◽  
Energy Process ◽  
Concentrated Solar Energy ◽  
Compressive Stresses ◽  
Hardening Process ◽  
Continuous Scanning

A recent French contribution in the field of surface hardening of steel using concentrated solar energy is presented. Single spot and continuous scanning processes have been investigated in a small-scale solar furnace. Hardened regions of 0.5–1.5 mm in thickness have been obtained on specimens of carbon steel, resulting from the transformation hardening process. Compressive stresses are induced in the thermally affected layer, without tensile peak in the bulk.

Cycle Calculations of a Small-Scale Heat Removal System With Supercritical CO2 As Working Fluid

2017 ◽  
Author(s):  
Marcel Strätz ◽  
Jörg Starflinger ◽  
Rainer Mertz ◽  
Michael Seewald ◽  
Sebastian Schuster ◽  
...  
Keyword(s):  
Power Plant ◽  
Supercritical Co2 ◽  
Heat Removal ◽  
Working Fluid ◽  
Small Scale ◽  
Brayton Cycle ◽  
Additional Heat ◽  
Decay Heat ◽  
Heat Removal System ◽  
Removal System

In case of an accident in a nuclear power plant with combined initiating events, (loss of ultimate heat sink and station blackout) additional heat removal system could transfer the decay heat from the core to and diverse ultimate heat sink. On additional heat removal system, which is based upon a Brayton cycle with supercritical CO2 as working fluid, is currently investigated within an EU-funded project, sCO2-HeRo (Supercritical carbon dioxide heat removal system). It shall serve as a self-launching, self-propelling and self-sustaining decay heat removal system to be used in severe accident scenarios. Since a Brayton cycle produces more electric power that it consumes, the excess electric power can be used inside the power plant, e.g. recharging batteries. A small-scale demonstrator will be attached to the PWR glass model at Gesellschaft für Simulatorforschung GfS, Essen, Germany. In order to design and build this small-scale model, cycle calculations are performed to determine the design parameters from which a layout can be derived.

System and component modelling of a low temperature solar thermal energy conversion cycle

2013 ◽  
Vol 24 (4) ◽  
pp. 51-62
Author(s):  
Shadreck M. Situmbeko ◽  
Freddie L. Inambao
Keyword(s):  
Low Temperature ◽  
Solar Energy ◽  
Thermal Energy ◽  
Electrical Power ◽  
Solar Thermal ◽  
Working Fluid ◽  
Small Scale ◽  
Solar Thermal Energy ◽  
Solar Field ◽  
Conversion Technology

Solar thermal energy (STE) technology refers to the conversion of solar energy to readily usable energy forms. The most important component of a STE technology is the collectors; these absorb the shorter wavelength solar energy (400-700nm) and convert it into usable, longer wavelength (about 10 times as long) heat energy. Depending on the quality (temperature and intensity) of the resulting thermal energy, further conversions to other energy forms such as electrical power may follow. Currently some high temperature STE technologies for electricity production have attained technical maturity; technologies such as parabolic dish (commercially available), parabolic trough and power tower are only hindered by unfavourable market factors including high maintenance and operating costs. Low temperature STEs have so far been restricted to water and space heating; however, owing to their lower running costs and almost maintenance free operation, although operating at lower efficiencies, may hold a key to future wider usage of solar energy. Low temperature STE conversion technology typically uses flat plate and low concentrating collectors such as parabolic troughs to harness solar energy for conversion to mechanical and/or electrical energy. These collector systems are relatively cheaper, simpler in construction and easier to operate due to the absence of complex solar tracking equipment. Low temperature STEs operate within temperatures ranges below 300oC. This research work is geared towards developing feasible low temperature STE conversion technology for electrical power generation. Preliminary small-scale concept plants have been designed at 500Wp and 10KWp. Mathematical models of the plant systems have been developed and simulated on the EES (Engineering Equation Solver) platform. Fourteen candidate working fluids and three cycle configurations have been analysed with the models. The analyses included a logic model selector through which an optimal conversion cycle configuration and working fluid mix was established. This was followed by detailed plant component modelling; the detailed component model for the solar field was completed and was based on 2-dimensional segmented thermal network, heat transfer and thermo fluid dynamics analyses. Input data such as solar insolation, ambient temperature and wind speed were obtained from the national meteorology databases. Detailed models of the other cycle components are to follow in next stage of the research. This paper presents findings of the system and solar field component.

Micro Gas Turbine Integrated With a Supercritical CO2 Brayton Cycle Turbine: Layout Comparison and Thermodynamic Analysis

2020 ◽  
Author(s):  
Fabrizio Reale ◽  
Raniero Sannino ◽  
Raffaele Tuccillo
Keyword(s):  
Gas Turbine ◽  
Supercritical Co2 ◽  
Waste Heat ◽  
Thermal Power ◽  
Energy Systems ◽  
Working Fluid ◽  
Small Scale ◽  
Brayton Cycle ◽  
Part Load ◽  
Micro Gas Turbine

Abstract In an energetic scenario where both distributed energy systems and smart energy grids gain increasing relevance, the research focus is also on the detection of new solutions to increase overall performance of small-scale energy systems. Waste heat recovery (WHR) can represent a good solution to achieve this goal, due to the possibility of converting residual thermal power in thermal engine exhausts into electrical power. The authors, in a recent study, described the opportunities related to the integration of a micro gas turbine (MGT) with a supercritical CO2 Brayton Cycle (sCO2 GT) turbine. The adoption of Supercritical Carbon Dioxide (sCO2) as working fluid in closed Brayton cycles is an old idea, already studied in the 1960s. Only in recent years this topic returned to be of interest for electric power generation (i.e. solar, nuclear, geothermal energy or coupled with traditional thermoelectric power plants as WHR). In this technical paper the authors analyzed the performance variations of different systems layout based on the integration of a topping MGT with a sCO2 GT as bottoming cycle; the performance maps for both topping and bottoming turbomachinery have been included in the thermodynamic model with the aim of investigating the part load working conditions. The MGT considered is a Turbec T100P and its behavior at part load conditions is also described. The potential and critical aspects related to the integration of the sCO2 GT as bottoming cycle are studied also through a comparison between different layouts, in order to establish the optimal compromise between overall efficiencies and complexity of the energy system. The off-design analysis of the integrated system is addressed to evaluate its response to variable electrical and thermal demands.

Transient Heat Delivery and Storage Process in a Thermocline Heat Storage System

2009 ◽  
Author(s):  
Jon T. Van Lew ◽  
Peiwen Li ◽  
Cho Lik Chan ◽  
Wafaa Karaki ◽  
Jake Stephens
Keyword(s):  
Solar Energy ◽  
Power Systems ◽  
Heat Storage ◽  
Low Cost ◽  
Storage System ◽  
Filler Material ◽  
Working Fluid ◽  
Efficient Computation ◽  
Concentrated Solar Energy ◽  
Feasible Option

Parabolic trough power systems utilizing concentrated solar energy have proven their worth as a means for generating electricity. However, one major aspect preventing the technologies widespread acceptance is the deliverability of energy beyond a narrow window during peak hours of the sun. Thermal storage is a viable option to enhance the dispatchability of the solar energy and an economically feasible option is a thermocline storage system with a low-cost filler material. Utilization of thermocline storage facilities have been studied in the past and this paper hopes to expand upon that knowledge. The current study aimed to effectively model the heat transfer of a working fluid interacting with filler material. An effective numerical method and efficient computation schemes were developed and verified. A thermocline storage system was modeled under specific conditions and results of great significance to heat storage design and operation were obtained.

Investigation on Solar-Powered Turbines Using Refrigerant R-134A

2014 ◽  
Author(s):  
Jihad Rishmany ◽  
Michel Daaboul ◽  
Issam Tawk ◽  
Nicolas Saba
Keyword(s):  
Power Generation ◽  
Solar Energy ◽  
Fossil Fuels ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Small Scale ◽  
Combustion Gases ◽  
Water Heaters ◽  
Wide Range ◽  
R 134A

Renewable energy has become a promising solution to substitute fossil fuels in power generation. In particular, the use of solar energy is stretched to a wide range of applications, e.g. photovoltaic cells, solar water heaters, solar space heating, solar thermal plants. However, the combination of solar energy with the Rankine cycle is limited to few applications only. In this context, this study aims in investigating the practicality of employing solar heaters to operate a Rankine cycle for small scale power generation. The working fluid in this study is refrigerant R-134a. Sizing and calculations of the various components of the system are carried out based on a net output power of 1 kW. In comparison with available electricity sources in Lebanon, it was found that the proposed system is currently more expensive than public electricity. However, it can compete with private generators that currently fill the gap in electricity shortage. The main advantage herein lies in the friendly environmental load due to the absence of combustion gases.

Design Considerations for Heat-Pipe Solar Receivers

1990 ◽  
Vol 112 (3) ◽  
pp. 169-176 ◽  
Author(s):  
Douglas R. Adkins
Keyword(s):  
Solar Energy ◽  
Heat Pipe ◽  
Focal Point ◽  
Liquid Sodium ◽  
Working Fluid ◽  
Concentrated Solar Energy ◽  
Stirling Engines ◽  
Parabolic Dish ◽  
Parabolic Dish Concentrator ◽  
Solar Receiver

Heat pipes are being developed to transfer solar energy from the focal point of a parabolic dish concentrator to the working fluid of Stirling engines. With these receivers, concentrated solar energy that is absorbed on the concave surface of a dome is removed by the evaporation of liquid sodium on the convex side of the dome. Vaporized sodium then condenses on an engine’s heater tubes and transfers energy to the working fluid of the engine. The condensed sodium returns to the absorber surface where it is redistributed across the dome by the capillary action of a wick. Issues concerning the flow of sodium in a heat-pipe solar receiver are investigated in this paper. A comparison is made between various wick options, and general issues concerning the design of heat-pipe receivers are also discussed.

Numerical Optimization of a Cogenerating Parabolic Solar Collector Receiver

2008 ◽  
Author(s):  
Catalina Gonzalez ◽  
Jinny Rhee
Keyword(s):  
Heat Transfer ◽  
Solar Energy ◽  
Solar Collector ◽  
Photovoltaic Cells ◽  
Electricity Consumption ◽  
Photovoltaic System ◽  
Working Fluid ◽  
Electrical Efficiency ◽  
Solar Systems ◽  
Electricity Costs

The motivation for this study comes from the need for a clean, renewable energy source, which is greater now more than ever to reduce the country’s dependence on fossil fuels. Cogenerating solar systems can provide heat and electricity for many industrial applications such as power generation and absorption refrigeration systems. For example, data centers that run on conventional refrigeration systems are one of the largest electricity consumers in the nation, accounting for 1.2% of the total electricity consumption in 2005. This electricity consumption, almost half of which is used to run the data center’s air conditioning units, translates to $2.7 billion in electricity costs for that year. Using cogenerating solar systems for these types of applications could represent a significant amount of savings in electricity costs. The objective of this paper is to numerically optimize a receiver for a cogenerating photovoltaic and thermal parabolic solar collector that will produce both heat and electricity. The solar cogeneration system studied will convert solar energy into both heat and electricity by using a combination of photovoltaic cells, a parabolic trough thermal collector, and water as the liquid heat exchanger on the photovoltaic cells. The peak electrical efficiency of the multi-junction gallium arsenide Spectrolab photovoltaic cells used in this study is about 32%, with the rest of the solar energy being absorbed as heat. These temperature gains in the cells can lead to a decrease in efficiency. However, in cogenerating systems, water is used as a working fluid to remove heat from the photovoltaic cells, thus aiding in increasing the electrical efficiency of the photovoltaic system as well as increasing the thermal energy gained from the solar thermal collector. The numerical analysis for this project will use Flotherm, a CFD tool used to solve fluid and thermal problems. A single-phase water cooled square duct receiver subjected to non-uniform heating will be analyzed in Flotherm to determine the optimal parameters for the best convection heat transfer between the working fluid and the photovoltaic cells. To enhance the heat transfer between photovoltaic cells and working fluid, the inner surface of the receiver tube receiving the heat flux will be improved by adding fins to increase heat transfer and induce turbulent flow. The initial receiver design will be compared with other receivers to determine the optimal design. Results will be presented parametrically for a range of flow rates and receiver geometry.

Cycle Calculations of a Small-Scale Heat Removal System With Supercritical CO2 as Working Fluid

2019 ◽  
Vol 5 (1) ◽  
Author(s):  
Marcel Straetz ◽  
Joerg Starflinger ◽  
Rainer Mertz ◽  
Dieter Brillert
Keyword(s):  
Carbon Dioxide ◽  
Power Plant ◽  
Heat Removal ◽  
Working Fluid ◽  
Small Scale ◽  
Brayton Cycle ◽  
Additional Heat ◽  
Decay Heat ◽  
Heat Removal System ◽  
Removal System

In the case of an accident in a nuclear power plant with combined initiating events (loss of ultimate heat sink and station blackout), an additional heat removal system could transfer the decay heat from the core to an ultimate heat sink (UHS). One specific additional heat removal system, based upon a Brayton cycle with supercritical carbon dioxide (CO2) as working fluid, is currently investigated within the European Union-funded project “sCO2-HeRo” (supercritical carbon dioxide heat removal system). It serves as a self-launching, self-propelling, and self-sustaining decay heat removal system used in severe accident scenarios. Since this Brayton cycle produces more electric power than it consumes, the excess electric power can be used inside the power plant, e.g., for recharging batteries. A small-scale demonstrator is attached to the pressurized water reactor (PWR) glass model at Gesellschaft für Simulatorschulung (GfS), Essen, Germany. In order to design and build this small-scale model, cycle calculations are performed to determine the design parameters from which a layout can be derived.

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