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.

Primary Study on Carbon Dioxide Power Cycle of HTGR

2008 ◽  
Author(s):  
Chengjie Duan ◽  
Xiaoyong Yang ◽  
Jie Wang ◽  
Suyuan Yu
Keyword(s):  
Carbon Dioxide ◽  
High Temperature ◽  
Physical Properties ◽  
Critical Pressure ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Power Cycle ◽  
Pressure Cycle ◽  
Cycle Efficiency ◽  
Thermal Physical Properties

At present, power cycles used in HTGR are indirect steam Rankine cycle and helium Brayton cycle. Using water or helium as working fluid which transform thermal energy into mechanical energy for HTGR power cycle has many disadvantages. Steam cycle could choose steam system which is similar to conventional coal-fired power plant, but because of the limit of material and equipments, there is big temperature difference between the steam and the helium, that makes big loss of thermal power and lowers the cycle efficiency. Helium can reach a high temperature in HTGR Brayton cycle and it has good stability, but because of helium has big isentropic exponent and low density, it is difficult to compress and makes helium turbine has shorter blades and more stages than normal gas turbine. Carbon dioxide has good thermal stability and physical properties. To avoid the reaction of CO2 with graphite and canning of fuel element at high temperature, it should be used in an indirect cycle as second loop working fluid. CO2 has appropriate critical pressure and temperature (7.38MPa, 304.19K) and can choose three types of cycle: supercritical cycle, subcritical-pressure cycle and trans-critical-pressure cycle (CO2 sometimes works under supercritical pressure, some times under subcritical-pressure). Carbon dioxide cycle works in a high pressure, so it makes pressure loss lower. When CO2 works close to its critical point, its density become larger than other conditions, and not change very much, this permits to reduce compress work. The thermal physical properties of carbon dioxide are totally different from helium due to CO2 works as real gas in the cycle. That causes the calculation of CO2 thermal physical properties, heat transfer and power cycle efficiency become difficult and need to be iterated. A systematic comparison between helium and carbon dioxide as working fluid for HTGR has been carried out. An empirical equation had been selected to estimate the thermal physical properties of carbon dioxide. Three types of carbon dioxide power cycle have been analyzed and the thermal efficiency has been calculated. A detailed introduction to the basic calculation process of the CO2 cycle thermal efficiency had been presented in the paper.

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.

Parametric Investigation of Brayton Cycle for High Temperature Gas-Cooled Reactors

Volume 4 ◽  
2004 ◽  
Author(s):  
Chang H. Oh ◽  
Richard L. Moore
Keyword(s):  
Carbon Dioxide ◽  
High Temperature ◽  
Supercritical Carbon Dioxide ◽  
Working Fluid ◽  
Brayton Cycle ◽  
Pebble Bed ◽  
Engineering Research ◽  
Cycle Efficiency ◽  
High Temperature Gas ◽  
Supercritical Carbon

The Idaho National Engineering and Environmental Laboratory (INEEL) has investigated a Brayton cycle efficiency improvement on a high temperature gas-cooled reactor (HTGR) as part of Generation-IV nuclear engineering research initiative. In this study, we are investigating helium Brayton cycles for the secondary side of an indirect energy conversion system. Ultimately we will investigate the improvement of the Brayton cycle using other fluids, such as supercritical carbon dioxide. Prior to the cycle improvement study, we established a number of baseline cases for the helium indirect Brayton cycle. The baseline cases are based on a 250 MW thermal pebble bed HTGR. In this study, we used the HYSYS computer code for optimization of the helium Brayton cycle and the balance of plant (BOP). In addition to the HYSYS process optimization, we performed parametric study to see the effect of important parameters on the cycle efficiency. For these parametric calculations, we also used a cycle efficiency model that was developed using the Visual Basic computer language. The results from this study are applicable to other reactor concepts such as a very high temperature gas-cooled reactor (VHTR), fast gas-cooled reactor (FGR), supercritical water reactor (SWR), and others. As part of this study we are currently investigated single-shaft vs. multiple shaft arrangement for cycle efficiency and comparison, which will be published in the next paper. The ultimate goal of this study is to use supercritical carbon dioxide for the HTGR power conversion loop in order to improve the cycle efficiency to values great than that of the helium Brayton cycle. This paper includes preliminary calculations of the steady state overall Brayton cycle efficiency based on the pebble bed reactor reference design (helium used as the working fluid) and compares those results with an initial calculation of a CO2 Brayton cycle.

Evaluation of a Novel Quadruple Combined Cycle with the Magnetohydrodynamic Generator based on 6E Analysis

2020 ◽  
pp. 1-28
Author(s):  
Mohammadamin Esmaeilzadehazimi ◽  
Mohammad Hasan Khoshgoftar Manesh ◽  
M. Majidi ◽  
Mohsen Nourpour
Keyword(s):  
High Temperature ◽  
Heat Source ◽  
Electric Power ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Combined Cycle ◽  
Brayton Cycle ◽  
Exergy Performance ◽  
Organic Fluids ◽  
First Time

Abstract The generation of the electric power through magnetohydrodynamic is one of the most advanced high -temperature energy conversions as it directly turns the heat into electricity. In this study, a quadruple cycle with magnetohydrodynamic generator was considered as the upstream cycle and a Brayton cycle was taken as the middle cycle through heating and an organic Rankine cycle and steam cycle were regarded as the downstream cycles using the heat loss of the magnetohydrodynamic generator and gas turbine, respectively. Energy, exergy, exergoeconomic, exergoenvironmental, emergoeconomic, and emergoenvironmental (6E) analyses were done in the proposed system simultaneously for the first time. In addition, advanced exergy, exergoeconomic, and exergoenvironmental analyses were performed for the proposed system to show the effect of irreversibility accurately and deeply. Despite the slight difference between the results of the emergoeconomic and emergoenvironmental sector with the exergoeconomic and exergoenvironmental sector, the obtained qualitative results were very similar showing that the emergoeconomic and emergoenvironmental analyses can be proper alternatives to the conventional exergoeconomic and exergoenvironmental analyses. The temperature of the heat source is one of the most important criteria for fluid selection in the organic Rankin cycles. Five organic fluids were selected and evaluated according to the desired hot source temperature for the Rankin organic cycle (262 °C). The results showed that the R141b with energy and efficiency of 15.25 and 58.05%, respectively had the best thermodynamic and exergy performance with the least amount of total costs using this fluid.

Spring and piston system for high temperature application

1997 ◽  
Author(s):  
R. Spivey ◽  
S. Breeding ◽  
J. Andrews ◽  
D. Stefanescu ◽  
S. Sen ◽  
...  
Keyword(s):  
High Temperature ◽  
High Temperature Application ◽  
Piston System ◽  
Temperature Application

scholarly journals Identification of Existing Challenges and Future Trends for the Utilization of Ammonia-Water Absorption–Compression Heat Pumps at High Temperature Operation

2021 ◽  
Vol 11 (10) ◽  
pp. 4635
Author(s):  
Marcel Ulrich Ahrens ◽  
Maximilian Loth ◽  
Ignat Tolstorebrov ◽  
Armin Hafner ◽  
Stephan Kabelac ◽  
...  
Keyword(s):  
High Temperature ◽  
Water Absorption ◽  
Industrial Sector ◽  
Heat Pumps ◽  
Working Fluid ◽  
Large Temperature ◽  
Future Trends ◽  
Ammonia Water ◽  
Starting Point ◽  
High Temperature Operation

Decarbonization of the industrial sector is one of the most important keys to reducing global warming. Energy demands and associated emissions in the industrial sector are continuously increasing. The utilization of high temperature heat pumps (HTHPs) operating with natural fluids presents an environmentally friendly solution with great potential to increase energy efficiency and reduce emissions in industrial processes. Ammonia-water absorption–compression heat pumps (ACHPs) combine the technologies of an absorption and vapor compression heat pump using a zeotropic mixture of ammonia and water as working fluid. The given characteristics, such as the ability to achieve high sink temperatures with comparably large temperature lifts and high coefficient of performance (COP) make the ACHP interesting for utilization in various industrial high temperature applications. This work reviews the state of technology and identifies existing challenges based on conducted experimental investigations. In this context, 23 references with capacities ranging from 1.4 kW to 4500 kW are evaluated, achieving sink outlet temperatures from 45 °C to 115 °C and COPs from 1.4 to 11.3. Existing challenges are identified for the compressor concerning discharge temperature and lubrication, for the absorber and desorber design for operation and liquid–vapor mixing and distribution and the choice of solution pump. Recent developments and promising solutions are then highlighted and presented in a comprehensive overview. Finally, future trends for further studies are discussed. The purpose of this study is to serve as a starting point for further research by connecting theoretical approaches, possible solutions and experimental results as a resource for further developments of ammonia-water ACHP systems at high temperature operation.

scholarly journals Component-Oriented Modeling of a Micro-Scale Organic Rankine Cycle System for Waste Heat Recovery Applications

2021 ◽  
Vol 11 (5) ◽  
pp. 1984
Author(s):  
Ramin Moradi ◽  
Emanuele Habib ◽  
Enrico Bocci ◽  
Luca Cioccolanti
Keyword(s):  
Electric Power ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Working Fluid ◽  
Pump Efficiency ◽  
Micro Scale

Organic Rankine cycle (ORC) systems are some of the most suitable technologies to produce electricity from low-temperature waste heat. In this study, a non-regenerative, micro-scale ORC system was tested in off-design conditions using R134a as the working fluid. The experimental data were then used to tune the semi-empirical models of the main components of the system. Eventually, the models were used in a component-oriented system solver to map the system electric performance at varying operating conditions. The analysis highlighted the non-negligible impact of the plunger pump on the system performance Indeed, the experimental results showed that the low pump efficiency in the investigated operating range can lead to negative net electric power in some working conditions. For most data points, the expander and the pump isentropic efficiencies are found in the approximate ranges of 35% to 55% and 17% to 34%, respectively. Furthermore, the maximum net electric power was about 200 W with a net electric efficiency of about 1.2%, thus also stressing the importance of a proper selection of the pump for waste heat recovery applications.

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