Auxiliary Heating System Research Articles

The effect of magnetic equilibrium on auxiliary heating schemes and fast particle confinement in Wendelstein 7-X

The performance of the auxiliary heating systems ion cyclotron resonance heating and neutral beam injection is calculated in three different magnetic mirror configurations foreseen to be used in future experiments in the Wendelstein 7-X stellarator: low, standard and high mirror. This numerical work is implemented with the SCENIC code package, which is designed to model three-dimensional magnetic equilibria whilst retaining effects such as anisotropy and the influence of including a finite orbit width of the particles. The ability to simulate NBI deposition in three-dimensional equilibria, the implementation of the realistic beam injector geometry, and the modification of the SCENIC package to permit the investigation of the 3-ion species heating scheme, are recent developments. Using these modifications, an assessment of the advantages and disadvantages of these two fast-ion producing auxiliary heating systems is made in the three different magnetic mirror equilibria. For NBI heating, the high mirror configuration displays the best global confinement properties, resulting in a larger collisional power transfer to the background plasma. The standard mirror has the best particle confinement in the core region, but the worst towards the edge of the plasma. The low mirror has the largest lost power and thus the lowest total collisional power. For ICRH, the displacement of the RF-resonant surface significantly impacts the heating performance. Due to the large toroidal magnetic mirror in the high mirror equilibrium, resonant particles easily become trapped and cannot remain in resonance, generating only small energetic particle populations. Despite this, global confinement is still the strongest in this equilibrium. The low mirror is the only equilibrium to produce peaked on-axis collisional power deposition, with associated peaked on-axis fast ion pressure profiles. A highly energetic particle population is then produced but this results in larger lost power as this equilibrium is not sufficiently optimised for fast ion confinement. A comparison between the two heating methods concludes that NBI produces a smaller fraction of lost to input power, and a reduced sensitivity of the performance to variations of the toroidal magnetic mirror. The main limit of NBI which does not apply to ICRH is the production of highly energetic particle populations, with predictions of energetic particles of E ∼ 0.45 MeV.

EU DEMO EC system preliminary conceptual design

The engineering design and R&D of auxiliary heating systems and their sub-systems are a key activities in the frame of the present conceptual design phase for a first of a kind DEMOnstration Fusion Power Plant in order to develop a system capable of achieving and controlling burning plasmas. In the frame of the EU DEMO reference design, the R&D activities consider the injection of about 50 MW of Electron Cyclotron (EC) power to support and assist different plasma phases. As the project is still in the conceptual phase, a range of options for gyrotrons, transmission lines and antennas is under assessment taking into account the guidelines for the integration of the EC system in a nuclear reactor and a maximal achievable reliability and availability of the EC power during operation.

Time-dependent behavior of a recompression cycle with direct CO2 heating through a parabolic collector array

The theoretical transient analysis of a recompression cycle is considered while directly heating the working fluid, CO2, in a solar trough field. The analysis explores the temporal behavior of the system’s performance for three distinct, minute-based, solar irradiation profiles: (i) daylong perfectly clear skies, (ii) instantaneous on-off cloud shading and (iii) partially cloudy day. The key objective is to study the effect of the solar intermittency on the heat exchangers, solar collector and on the overall cycle’s behavior – the thermal capacitance of the two first components is considered. The calculations reveal that, even though auxiliary heating systems was not considered, the heat capacitance of the working fluid and parabolic collector assembly is capable of instantaneously smoothing out the cycle’s performance for on-off clouding conditions, such as the net power and thermodynamics efficiencies – note that the cycle’s performance disregards the parabolic trough efficiency. Differently, the overall system’s efficiency, which is regarded as the product of the efficiencies of the cycle and parabolic trough, is much more sensitive to irradiation changes. The study also specifically considers the effect of the clouding intensity and time, with the former being measured as fraction of clear sky irradiation on the system’s performance. The analysis shows that it is possible to quantify the time scale available such that an auxiliary heating system delivers heat to the working fluid during a clouding scenario allowing the plant to work steadily.

Scenario development during commissioning operations on the National Spherical Torus Experiment Upgrade

The National Spherical Torus Experiment Upgrade (NSTX-U) will advance the physics basis required for achieving steady-state, high-beta, and high-confinement conditions in a tokamak by accessing high toroidal fields (1 T) and plasma currents (1.0–2.0 MA) in a low aspect ratio geometry (A = 1.6–1.8) with flexible auxiliary heating systems (12 MW NBI, 6 MW HHFW). This paper describes the progress in the development of L- and H-mode discharge scenarios and the commissioning of operational tools in the first ten weeks of operation that enable the scientific mission of NSTX-U. Vacuum field calculations completed prior to operations supported the rapid development and optimization of inductive breakdown at different values of ohmic solenoid current. The toroidal magnetic field (BT0 = 0.65 T) exceeded the maximum values achieved on NSTX and novel long-pulse L-mode discharges with regular sawtooth activity exceeded the longest pulses produced on NSTX (tpulse > 1.8 s). The increased flux of the central solenoid facilitated the development of stationary L-mode discharges over a range of density and plasma current (Ip). H-mode discharges achieved similar levels of stored energy, confinement (H98y,2 > 1) and stability (βN/βN-nowall > 1) compared to NSTX discharges for Ip ⩽ 1 MA. High-performance H-mode scenarios require an L–H transition early in the Ip ramp-up phase in order to obtain low internal inductance (li) throughout the discharge, which is conducive to maintaining vertical stability at high elongation (κ > 2.2) and achieving long periods of MHD quiescent operations. The rapid progress in developing L- and H-mode scenarios in support of the scientific program was enabled by advances in real-time plasma control, efficient error field identification and correction, effective conditioning of the graphite wall and excellent diagnostic availability.

Simulation of Airflow in the Burning Cave of an Auxiliary Heating System in a Greenhouse

Abstract. In this study, numerical simulations of airflow were carried out in the burning cave of an auxiliary heating system. Experimental measurements were also conducted to verify the performance of the numerical model, and turbulent airflow in the burning cave was considered. The numerical simulation in the burning cave was performed for three cases:(1) with a baffle at the bottom of the burning cave entrance, (2) without a baffle at the burning cave entrance, and (3) with a baffle at the top of the burning cave entrance. The turbulent airflow was modeled using the realizable k-e turbulence model as well as the non-equilibrium wall function. The airflow velocity was assessed in the burning cave, and some suggestions were given to improve the performance of the burning cave. The results showed that the airflow entering the burning cave differed due to different positions of the baffle. The smoldering combustion was more even and the burning rate could be controlled more easily when the baffle was placed at the top of the burning cave entrance, making the airflow enter the burning cave through the bottom of the baffle. The results also showed that the maximum airflow velocity in the burning cave increased with increased distance between the baffle and the bottom of the burning cave. Keywords: Airflow, Burning cave, Greenhouse, Simulation.

Overview of the preliminary design of the ITER plasma control system

An overview of the preliminary design of the ITER plasma control system (PCS) is described here, which focusses on the needs for 1st plasma and early plasma operation in hydrogen/helium (H/He) up to a plasma current of 15 MA with moderate auxiliary heating power in low confinement mode (L-mode). Candidate control schemes for basic magnetic control, including divertor operation and kinetic control of the electron density with gas puffing and pellet injection, were developed. Commissioning of the auxiliary heating systems is included as well as support functions for stray field topology and real-time plasma boundary reconstruction. Initial exception handling schemes for faults of essential plant systems and for disruption protection were developed. The PCS architecture was also developed to be capable of handling basic control for early commissioning and the advanced control functions that will be needed for future high performance operation. A plasma control simulator is also being developed to test and validate control schemes. To handle the complexity of the ITER PCS, a systems engineering approach has been adopted with the development of a plasma control database to keep track of all control requirements.

Conceptual design of the EU DEMO EC-system: main developments and R&D achievements

For the development of a DEMOnstration Fusion Power Plant the design of auxiliary heating systems is a key activity in order to achieve controlled burning plasma. The present heating mix considers electron cyclotron resonance heating (ECRH), neutral beam injection (NBI) and ion cyclotron resonance heating (ICRH) with a target power to the plasma of about 50 MW for each system. The main tasks assigned to the EC system are plasma breakdown and assisted start-up, heating to L-H transition and plasma current ramp up to burn, MHD stability control and assistance in plasma current ramp down. The consequent requirements are used for the conceptual design of the EC system, from the RF source to the launcher, with an extensive R&D program focused on relevant technologies to be developed. Gyrotron: the R&D and Advanced Developments on EC RF sources are targeting for gyrotrons operating at 240 GHz, considered as optimum EC Current Drive frequency in case of higher magnetic field than for the 2015 EU DEMO1 baseline. Multi-purpose (multi-frequency) and frequency step-tunable gyrotrons are under investigation to increase the flexibility of the system. As main targets an output power of significantly above 1 MW (target: 2 MW) and a total efficiency higher than 60% are set. The principle feasibility at limits of a 236 GHz, conventional-cavity and, alternatively, of a 238 GHz coaxial-cavity gyrotron are under investigation together with the development of a synthetic diamond Brewster-angle window technology. Advanced developments are on-going in the field of multi-stage depressed collector technologies. Transmission line (TL): different TL options are under investigation and a preliminary study of an evacuated quasi-optical multiple-beam TL, considered for a hybrid solution, is presented and discussed in terms of layout, dimensions and theoretical losses. Launcher: remote steering antennas have been considered as a possible launcher solution especially under the constraints to avoid movable mirrors close to the plasma. With dedicated beam tracing calculations, the deposition locations coverage and the wave absorption efficiency have been investigated, considering a selection of frequencies, injection angles and launching points. An option for the EC system structure is proposed in clusters, in order to allow the necessary redundancy and flexibility to guarantee the required EC power in the different phases of the plasma pulse. Number and composition of the clusters are analysed to have high availability and therefore maximum reliability with a minimum number of components.

Beam Sweeping for Long-Pulse Operation of an Ion Source in Neutral Beam Injectors

Long-pulse operation has been initially and successfully demonstrated during a 100-s stable beam extraction in the neutral beam test stand (NBTS) system of the Korea Atomic Energy Research Institute (KAERI) for the positive ion source (IS) of the JT-60SA neutral beam injector. The NBTS system was constructed at KAERI to develop 300-s deuterium beam extractions of 100 kV/50 A as an auxiliary heating system of the Korea Superconducting Tokamak Advanced Research (KSTAR). The IS of the JT-60SA neutral beam injector is composed of a plasma generator and a set of tetrode accelerators. The beamline components include an optical multichannel analyzer duct, a neutralizer, a bending magnet (BM), a calorimeter, and a vacuum pump system. The beam power deposition of the IS and the beamline components along the NBTS have been measured by water flow calorimetry (WFC), and a total of 99.7% of the extracted beam power (Vacc∙Iacc) was counted for a hydrogen beam of 82 kV/25 A (2.05 MW) during 100-s beam extraction. To reduce the localized heat load on the calorimeter plate, a method of small-angle deflection for the ion beam particles was applied using a small alternate current of 8 A, 0.5 Hz for the BM coil.

Energy saving potential of pipe-embedded building envelope utilizing low-temperature hot water in the heating season

An active pipe-embedded building envelope has been verified to be effective for reducing heat transfer through building envelopes in summer. To decrease the energy consumption of heating, air source heat pumps are proposed for generating low-temperature hot water for the pipe-embedded building envelope in this study. A comprehensive numerical model is adopted to simulate the dynamic heat transfer in the pipe-embedded structure, and the model has been validated by experiment. The energy consumption and operation cost of the novel system are analyzed for different water temperatures. The seasonal performance in different cities and orientations is evaluated in winter conditions. The results show that 84% of the heat transfer on the internal surface can be reduced, whereas the heat dissipation on the external surface is increased by only 18% in Beijing. The proposed system is more suitable for cold regions because more heat transfer can be reduced there. The reduction ratios of the pipe-embedded system are close for all of the orientations, but the reduction amount on the north is 40% more than that on the south. The water temperature has a significant impact on the performance of the system, and room temperature water is suggested. Overall, the proposed system is effective as an auxiliary heating system.

The Design and Manufacture of the Neutral Beam Injection Thermal Shield for the EAST Tokamak

Neutral beam injection (NBI) is a high-power auxiliary heating system for the EAST device. We present a thermal shield (TS) structure to protect the neck pipe of the EAST equatorial port to avoid damage from the NBI beam. Since the EAST port has a big trumpet structure, a straight section, and a small trumpet structure, to accommodate the port structure, a TS concept is put forward including its cooling system. The cooling loops and the sub-branches were designed with interfaces between the inner cooling branches. The heat removal capability is verified by a thermal hydraulics analysis based on ANSYS code. In particular, fabrication is addressed with technical processing technology, especially for the embedded cooling pipes in the heat sinks. The pipes are checked for leaks after bending and the embedding processing. The assembly activities are demonstrated in the spatial space zones of the port before the engineering installation. It is confirmed that the TS structure is safe and will run feasibly in the EAST discharge. It is indicated that the TS structure can provide thermal shielding and remove heat for the NBI device in the port region.

ENERGETIC PERFORMANCE ASSESSMENT OF A THERMO-SOLAR GREENHOUSE FISH (NILE TILAPIA) HATCHERY

Energetic performance of a thermo-solar greenhouse representing a fish hatchery system was suggested, developed and investigated. The developed system was mainly consisted of a double cover greenhouse coupled with solar collector and heat exchanger for water heating. The main aim was to control the water environment, namely temperature and dissolved oxygen, of a fish (Nile Tilapia) hatchery at the desired levels. The main experimental work was carried out during the period from December 2014 to February 2015. The suggested and investigated system based mainly on solar energy as the source of power. However, an auxiliary heating system, namely an electric heater was used upon request. The experimental system was constructed and investigated at the research farm, Faculty of Agriculture, Kafrelsheikh University (31.07oN and 30.57oE) Kafrelsheikh governorate, Egypt. Environmental parameters; namely temperature, solar radiation, relative humidity, wind speed and water quality in terms of dissolved oxygen were monitored. The results indicated an efficient control in water temperature and quality. The average temperature and dissolved oxygen concentration of fish pond water throughout the whole experimental period were 26.8 (SD = 0.15) °C and 7.62 (SD =0.68) ppm respectively. The average value of air temperature rise inside the greenhouse was 8.4 °C. The average value of total daily water energy gained via the heat exchanger system was 18.185 MJ/ day per m2of the fish pond water surface area at an average value of 13.433 MJ/ (m2.day) of the incident solar radiation on the horizontal plane. As a conclusion the weekly average percentage of energy contribution of both greenhouse action and heat exchanger operating times were 58.13 and 41.87% respectively as a percentage of the whole operating time.

A modernized control system of the “Victoria” pulse modulator complex

The results of designing an automated control system (ACS) of the Victoria pulse modulator complex, which is used for the high-voltage power supply of auxiliary plasma heating systems on the Т-10 and Т-15 tokamaks and gyrotron test benches, are considered. The ACS is based on digital and microprocessor devices and ensures control of the power circuit of high-voltage modulators, monitoring of the load parameters, and emergency protection of the power electrical equipment.

Energy assessment of solar cooling thermally driven system configurations for an office building in a Nordic country

Thermal cooling systems are particularly attractive in locations supplied by district heating based on cogeneration heating plants (CHP). Moreover, solar thermal energy is a major renewable source for the provision of thermal energy, fulfilling demands for space heating, domestic hot water, process heat, and cooling. This energy source can be suitably used also in Nordic Countries.The presented paper focuses on two configurations of a cooling solar-driven thermal system for an office building located in Finland. Dynamic simulation approach has been used through TRNSYS software. In particular, the configurations differ from the connection between the hot storage tank, the solar collectors and the chiller. Particularly, in the first configuration only the tank can supply the chiller (Case 1), while in the second, the chiller can be supplied either by the tank or the solar collectors directly (Case 2). System performance indexes, in case of district heating as main building heating supply system in winter and as auxiliary heating system for the chiller in summer, have been evaluated as a function of the tank and solar thermal field sizes.Results show that Case 2 has better performance than Case 1, because of the versatility shown in summer. Particularly, when the solar irradiance is low, Case 2 solutions perform far better than Case 1 solutions, benefitting from the direct connection between the solar collectors and the chiller. This study has highlighted also the potential of this technology in cold climate areas supplied by means of DH based on CHP plants. Indeed, the adoption of such cooling technology, in addition to reduce both heating and cooling consumed energy and to shave summer electricity peaks, can potentially allow some CHP plants to operate also in summer, fulfilling the future energy networks aims: being able to provide electricity, heat and cooling energy.

Replacing traditional materials with polymeric materials in solar thermosiphon systems – Case study on pros and cons based on a total cost accounting approach

The pros and cons of replacing traditional materials with polymeric materials in solar thermosiphon systems were analysed by adopting a total cost accounting approach. In terms of climatic and environmental performance, polymeric materials reveal better key figures than traditional ones like metals. In terms of present value total cost of energy, taking into account functional capability, end user investment cost, O&M cost, reliability and climatic cost, the results suggest that this may also be true when comparing a polymeric based thermosiphon system with a high efficient thermosiphon system of conventional materials for DHW production in the southern Europe regions.When present values for total energy cost are assessed for the total DHW systems including both the solar heating system and the auxiliary electric heating system, the difference in energy cost between the polymeric and the traditional systems is markedly reduced. The main reason for the difference in results can be related to the difference in thermal performance between the two systems. It can be concluded that the choice of auxiliary heating source is of utmost importance for the economical competiveness of systems and that electric heating may not be the best choice.

Performance investigation of a novel solar hybrid air conditioning and humidification–dehumidification water desalination system

Parametric and economic studies of the performance of a solar hybrid air conditioning (A/C) and humidification–dehumidification (HDH) water desalination system are presented. The system is integrated with thermal storage and auxiliary heating systems for steady-state operation. Fresh water production rate, fresh water recovery, cooling capacity, electrical power consumption, coefficient of performance and system economical index are studied at different operating and design parameters. The results show that (i) the electrical consumption of the auxiliary heater decreases with decreasing outdoor air flow rate and increasing both of outdoor air temperature, outdoor air humidity and temperature difference across the heating system, (ii) the increase in outdoor air temperature, outdoor humidity and temperature difference across the heating system increase the fresh water production and recovery rates, cooling capacity and the electric power consumption of the proposed system. Comparison with a basic air conditioning system showed that the proposed system has higher water production, cooling capacity, coefficient of performance (COP) and lower power/electricity consumptions at hot and humid regions. A cost analysis reveals that the saving in the total operating cost increases with increasing outdoor air temperature, and outdoor humidity and decreases with increasing temperature difference across the heating system.

Solar-Active-Houses – Dynamic System Simulations to Analyze Building Concepts with High Fractions of Solar Thermal Energy

Abstract In the German national research and development project “HeizSolar” the building concept of Solar-Active-Housesis analyzed. The concept allows for a high fraction of solar thermal energyof more than 50% of the total heat supply. Within the project nine existing buildings have been monitored since the beginning of the heating period of 2011. The technology applied for this kind of supply concept has been introduced in [1,2]. Based on the data obtained from the in-situ monitoring, typical operation conditions have been identified and analyzed in [3]. The measured datawas also used to derive parameters to calibratea dynamic system simulation model for Solar-Active-Houses[4]. Theelaborated model focuses on the performance of the solar thermal collector as well as the solar circuit. What is more, the dynamic interaction between the solar thermal heat generator and the auxiliary heating systems as well as the heat distribution system are incorporated in detail. Finally the diffuse heat flux resulting of the integration of large hot water storage tanks into the building envelope is implemented to the model. This model is applied in the following to analyze the general thermal behavior of the supply concept and to derive optimization potentials. In detail the systems performance in regard to different types of heat transferal systems for space heating is demonstrated. Also the dimensioning in regard to the key parameters of collector area and the thermal capacity of the storage system consisting of a hot water storage tankare stated.

English

Solar radiation is a source of energy that can be used directly by residences and industries. In this work, the efficiency of a solar collector type all-glass installed in a rural area in Parana, Brazil, in the winter period, was evaluated. Two daily showers were simulated in three different scenarios, to measure additional electrical consumption used to boost the heating of water. In the first scenario, the consumption was evaluated leaving the auxiliary heating system connected the entire day and, in the second, only in the afternoon period. This auxiliary heating system, controlled by a thermostat, was only connected when the temperature of the water in the boiler stayed below 40°C. In the third scenario, the auxiliary heating system was disconnected and the heating of the water occurred solely due to the solar heating system. These scenarios were compared with the use of the solar heating system together with an electric shower and with an electric shower alone. It was verified that the mean efficiency of the solar collector in the evaluated period was 51%. The electric shower, when used in conjunction with the solar heater, consumes 6.5 times less electrical energy than when used alone (192.55 kWh and 1240.34 kWh, respectively). Key words: Renewable energy, vacuum solar collector, solar water heater.

Implementation of a new Disruption Mitigation System into the control system of JET

A new Disruption Mitigation System (DMS) based on Massive Gas Injections (MGI) has been installed at the JET-tokamak. The key component of this system is a fast eddy current driven valve, which is capable of injecting up to 4.6×10−3MPam3 in less than 5ms. Along with this valve a new gas handling system has been installed, whose control had to be integrated into the JET-operation. The operation of the DMS requires interaction with several other systems. Although Massive Gas Injections are used to ameliorate potentially severe damage to the tokamak plant and plasma facing components caused by disruptions, they introduce a high risk for example to auxiliary heating systems or diagnostics, which could be damaged by high vacuum pressures. In addition to this, the presence of high pressure (of noble and flammable gases) in combination with high voltages represents a risk not only to the actual DMS plant itself (in case of a failure) but also to personnel in the vicinity. These varieties of risks have been addressed and are described in this article.

Optimization Design of Solar Hot Water System of Splited-Type Villa Type Building

With economic performance, effect, energy saving, safe and reliable, comprehensive performance unique advantages, more suitable for use in building the popularity of the villa with its solar water heaters and other energy-saving and environmental protection and the use of simple distinctions, by the majority of consumers, and has been the rapid development and wide application. Solar hot water system is not only energy use, more important role is to improve the environment, to meet the needs of the country with regard to energy conservation, but also for China to improve the energy structure, but also improve energy strategy considerations. Introduces the domestic and foreign common form of split solar water heating systems, analyzes the existing problems and causes, solar and electric auxiliary heating system, for example, to optimize the design ideas proposed split solar hot water system, proved that the system is stable reliable

Progress in the ITER electron cyclotron heating and current drive system design

An electron cyclotron system is one of the four auxiliary plasma heating systems to be installed on the ITER tokamak. The ITER EC system consists of 24 gyrotrons with associated 12 high voltage power supplies, a set of evacuated transmission lines and two types of launchers. The whole system is designed to inject 20MW of microwave power at 170GHz into the plasma. The primary functions of the system include plasma start-up, central heating and current drive, and magneto-hydrodynamic instabilities control. The design takes present day technology and extends towards high power CW operation, which represents a large step forward as compared to the present state of the art. The ITER EC system will be a stepping stone to future EC systems for DEMO and beyond.The EC system is faced with significant challenges, which not only includes an advanced microwave system for plasma heating and current drive applications but also has to comply with stringent requirements associated with nuclear safety as ITER became the first fusion device licensed as basic nuclear installations as of 9 November 2012.Since conceptual design of the EC system established in 2007, the EC system has progressed to a preliminary design stage in 2012, and is now moving forward towards a final design. The majority of the subsystems have completed the detailed design and now advancing towards the final design completion.