•Elemental sulfur is a low-cost and high-performance storage medium for low- to high- temperature TES.•Experimentally validated CFD model elucidates heat transfer performance of sulfur in low ...temperature range.•Thermal charge and discharge rates of sulfur for low temperature TES operation are reported.•Functional correlation relating transient liquid fraction and “solid–liquid buoyancy-Fourier number” is developed.
Elemental sulfur provides a low-cost, high-performance thermal storage option for a wide range of applications and over an exceptionally wide range of temperatures (50 °C to over 600 °C). In previous efforts we have shown impressive performance for 200–600 °C, while in this study we examine the low-temperature (50–200 °C) thermal charge and discharge behavior of isochoric sulfur-based storage using a detailed computational model solving for the conjugate heat transfer and solid-liquid phase change dynamics. The model provides excellent agreement with experimental results. We show that sulfur exhibits lower viscosity because of reduction in the chain-length of polymeric sulfur caused by trace amounts of organic substances resulting in attractive charge and discharge performance. The results from the parametric analysis of pipe diameter on the charge and discharge heat transfer characteristics are used to develop a simple, generalized correlation that relates the transient sulfur temperature and liquid fraction evolution as a function of dynamically evolving buoyancy-Fourier number due to the solid-liquid phase change. This solid-liquid buoyancy-Fourier, BFs-l, correlation can be used for effectively designing sulfur-based thermal energy storage systems for transient operation in low temperature applications.
The ELFIN Mission Angelopoulos, V.; Tsai, E.; Bingley, L. ...
Space science reviews,
2020/8, Letnik:
216, Številka:
5
Journal Article
Recenzirano
Odprti dostop
The Electron Loss and Fields Investigation with a Spatio-Temporal Ambiguity-Resolving option (ELFIN-STAR, or heretoforth simply: ELFIN) mission comprises two identical 3-Unit (3U) CubeSats on a polar ...(∼93
∘
inclination), nearly circular, low-Earth (∼450 km altitude) orbit. Launched on September 15, 2018, ELFIN is expected to have a >2.5 year lifetime. Its primary science objective is to resolve the mechanism of storm-time relativistic electron precipitation, for which electromagnetic ion cyclotron (EMIC) waves are a prime candidate. From its ionospheric vantage point, ELFIN uses its unique pitch-angle-resolving capability to determine whether measured relativistic electron pitch-angle and energy spectra within the loss cone bear the characteristic signatures of scattering by EMIC waves or whether such scattering may be due to other processes. Pairing identical ELFIN satellites with slowly-variable along-track separation allows disambiguation of spatial and temporal evolution of the precipitation over minutes-to-tens-of-minutes timescales, faster than the orbit period of a single low-altitude satellite (T
orbit
∼ 90 min). Each satellite carries an energetic particle detector for electrons (EPDE) that measures 50 keV to 5 MeV electrons with
Δ
E/E < 40% and a fluxgate magnetometer (FGM) on a ∼72 cm boom that measures magnetic field waves (e.g., EMIC waves) in the range from DC to 5 Hz Nyquist (nominally) with <0.3 nT/sqrt(Hz) noise at 1 Hz. The spinning satellites (T
spin
∼
3 s) are equipped with magnetorquers (air coils) that permit spin-up or -down and reorientation maneuvers. Using those, the spin axis is placed normal to the orbit plane (nominally), allowing full pitch-angle resolution twice per spin. An energetic particle detector for ions (EPDI) measures 250 keV – 5 MeV ions, addressing secondary science. Funded initially by CalSpace and the University Nanosat Program, ELFIN was selected for flight with joint support from NSF and NASA between 2014 and 2018 and launched by the ELaNa XVIII program on a Delta II rocket (with IceSatII as the primary). Mission operations are currently funded by NASA. Working under experienced UCLA mentors, with advice from The Aerospace Corporation and NASA personnel, more than 250 undergraduates have matured the ELFIN implementation strategy; developed the instruments, satellite, and ground systems and operate the two satellites. ELFIN’s already high potential for cutting-edge science return is compounded by concurrent equatorial Heliophysics missions (THEMIS, Arase, Van Allen Probes, MMS) and ground stations. ELFIN’s integrated data analysis approach, rapid dissemination strategies via the SPace Environment Data Analysis System (SPEDAS), and data coordination with the Heliophysics/Geospace System Observatory (H/GSO) optimize science yield, enabling the widest community benefits. Several storm-time events have already been captured and are presented herein to demonstrate ELFIN’s data analysis methods and potential. These form the basis of on-going studies to resolve the primary mission science objective. Broad energy precipitation events, precipitation bands, and microbursts, clearly seen both at dawn and dusk, extend from tens of keV to >1 MeV. This broad energy range of precipitation indicates that multiple waves are providing scattering concurrently. Many observed events show significant backscattered fluxes, which in the past were hard to resolve by equatorial spacecraft or non-pitch-angle-resolving ionospheric missions. These observations suggest that the ionosphere plays a significant role in modifying magnetospheric electron fluxes and wave-particle interactions. Routine data captures starting in February 2020 and lasting for at least another year, approximately the remainder of the mission lifetime, are expected to provide a very rich dataset to address questions even beyond the primary mission science objective.
Elemental sulfur is a promising storage material for low to high temperature thermal energy storage (TES) applications due to its high chemical stability, high heat transfer rate, and low cost. In ...this study, we investigate the performance of sulfur-based TES systems (SulfurTES) in a single-tank thermal battery configuration. In general, the results show that a moderate shell aspect ratio and standard tube diameters can be used to provide a range of high performance. An experimentally validated 2D numerical model is used here. The model predicts system-level performance based on the energetic and exergetic efficiencies for a range of geometric parameters and operating mass flow rates. This analysis shows the competing effects of the design and operating conditions on the performance parameters, and reveals governing parameter spaces unique to the specified performance targets. We have proposed a strategy to identify this parameter space, for which, the SulfurTES system will achieve required thermal performance, and a design procedure to incorporate such parameter space in system design. This work provides a systematic approach in TES performance investigation, and establishes an important framework to design industrial-scale SulfurTES systems that will offer high thermal performance using low-cost materials.
•A high-fidelity numerical model is developed for sulfur-based thermal energy storage system with experimental validation.•The model is employed to perform a parametric study that reveals relationship between design/operation and system performance.•A design strategy is formulated to determine appropriate system design and operation that provides attractive performance.•The study proposes a systematic approach for TES performance investigation and sound basis for cost analysis.
We review comprehensive observations of electromagnetic ion cyclotron (EMIC) wave-driven energetic electron precipitation using data collected by the energetic electron detector on the Electron ...Losses and Fields InvestigatioN (ELFIN) mission, two polar-orbiting low-altitude spinning CubeSats, measuring 50-5000 keV electrons with good pitch-angle and energy resolution. EMIC wave-driven precipitation exhibits a distinct signature in energy-spectrograms of the precipitating-to-trapped flux ratio: peaks at >0.5 MeV which are abrupt (bursty) (lasting ∼17 s, or
Δ
L
∼
0.56
) with significant substructure (occasionally down to sub-second timescale). We attribute the bursty nature of the precipitation to the spatial extent and structuredness of the wave field at the equator. Multiple ELFIN passes over the same MLT sector allow us to study the spatial and temporal evolution of the EMIC wave - electron interaction region. Case studies employing conjugate ground-based or equatorial observations of the EMIC waves reveal that the energy of moderate and strong precipitation at ELFIN approximately agrees with theoretical expectations for cyclotron resonant interactions in a cold plasma. Using multiple years of ELFIN data uniformly distributed in local time, we assemble a statistical database of ∼50 events of strong EMIC wave-driven precipitation. Most reside at
L
∼
5
−
7
at dusk, while a smaller subset exists at
L
∼
8
−
12
at post-midnight. The energies of the peak-precipitation ratio and of the half-peak precipitation ratio (our proxy for the minimum resonance energy) exhibit an
L
-shell dependence in good agreement with theoretical estimates based on prior statistical observations of EMIC wave power spectra. The precipitation ratio’s spectral shape for the most intense events has an exponential falloff away from the peak (i.e., on either side of
∼
1.45
MeV). It too agrees well with quasi-linear diffusion theory based on prior statistics of wave spectra. It should be noted though that this diffusive treatment likely includes effects from nonlinear resonant interactions (especially at high energies) and nonresonant effects from sharp wave packet edges (at low energies). Sub-MeV electron precipitation observed concurrently with strong EMIC wave-driven >1 MeV precipitation has a spectral shape that is consistent with efficient pitch-angle scattering down to ∼ 200-300 keV by much less intense higher frequency EMIC waves at dusk (where such waves are most frequent). At ∼100 keV, whistler-mode chorus may be implicated in concurrent precipitation. These results confirm the critical role of EMIC waves in driving relativistic electron losses. Nonlinear effects may abound and require further investigation.
•Elemental sulfur is a promising low-cost candidate for thermal energy storage.•Transient performance of sulfur-based shell and tube thermal battery is investigated.•Results show preferred designs ...that provide high exergetic efficiency and low system cost.
Thermal energy storage (TES) is an important energy storage technology that can be coupled to intermittent energy sources to improve system dispatchability. Elemental sulfur is a promising candidate storage fluid for high temperature TES systems due to its high energy density, moderate vapor pressure, high thermal stability, and low cost. This study uses a transient, two-dimensional numerical model to investigate the design and performance of a thermal energy storage (TES) system that uses sulfur stored isochorically in an intermodal shell and tube thermal battery configuration. Parametric analyses of key design and operating parameters show that there is a preferred tube diameter based on the competing influence of system-level energy storage utilization, exergetic efficiency, and cost. The results show that designs with smaller tube dimensions in the range of 2″ NPS to 4″ NPS provide exergetic efficiencies close to 95% while tube dimensions in the range of 4″ NPS to 8″ NPS meet the Department of Energy cost target of $15/kWh with costs being as low as $8.41/kWh. Finally, a table of preferred designs that meet the DOE cost goals is presented to help guide future design and experimentation efforts.
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