scholarly journals MonkeyDB: effectively testing correctness under weak isolation levels

2021 ◽  
Vol 5 (OOPSLA) ◽  
pp. 1-27
Author(s):  
Ranadeep Biswas ◽  
Diptanshu Kakwani ◽  
Jyothi Vedurada ◽  
Constantin Enea ◽  
Akash Lal
Keyword(s):  
Social Networking ◽  
Large Scale ◽  
Storage Systems ◽  
Storage System ◽  
Trade Off ◽  
Read Operation ◽  
A Value ◽  
Logical Specification ◽  
Good Coverage

Modern applications, such as social networking systems and e-commerce platforms are centered around using large-scale storage systems for storing and retrieving data. In the presence of concurrent accesses, these storage systems trade off isolation for performance. The weaker the isolation level, the more behaviors a storage system is allowed to exhibit and it is up to the developer to ensure that their application can tolerate those behaviors. However, these weak behaviors only occur rarely in practice and outside the control of the application, making it difficult for developers to test the robustness of their code against weak isolation levels. This paper presents MonkeyDB, a mock storage system for testing storage-backed applications. MonkeyDB supports a key-value interface as well as SQL queries under multiple isolation levels. It uses a logical specification of the isolation level to compute, on a read operation, the set of all possible return values. MonkeyDB then returns a value randomly from this set. We show that MonkeyDB provides good coverage of weak behaviors, which is complete in the limit. We test a variety of applications for assertions that fail only under weak isolation. MonkeyDB is able to break each of those assertions in a small number of attempts.

Performance of Thermal Enhancement Materials in High Pressure Metal Hydride Storage Systems

2008 ◽  
Author(s):  
Timothe´e L. Pourpoint ◽  
Aaron Sisto ◽  
Kyle C. Smith ◽  
Tyler G. Voskuilen ◽  
Milan K. Visaria ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
High Pressure ◽  
Metal Hydride ◽  
Large Scale ◽  
Storage Systems ◽  
Storage System ◽  
Hydrogen Gas ◽  
Thermal Enhancement ◽  
Hydrogen Systems ◽  
Hydride Powder

Over the past two years, key issues associated with the development of realistic metal hydride storage systems have been identified and studied at Purdue University’s Hydrogen Systems Laboratory, part of the Energy Center at Discovery Park. Ongoing research projects are aimed at the demonstration of a prototype large-scale metal hydride tank that achieves fill and release rates compatible with current automotive use. The large-scale storage system is a prototype with multiple pressure vessels compatible with 350 bar operation. Tests are conducted at the Hydrogen Systems Lab in a 1000 ft2 laboratory space comprised of two test cells and a control room that has been upgraded for hydrogen service compatibility. The infrastructure and associated data acquisition and control systems allow for remote testing with several kilograms of high-pressure reversible metal hydride powder. Managing the large amount of heat generated during hydrogen loading directly affects the refueling time. However, the thermal management of hydride systems is problematic because of the low thermal conductivity of the metal hydrides (∼ 1 W/m-K). Current efforts are aimed at optimizing the filling-dependent thermal performance of the metal hydride storage system to minimize the refueling time of a practical system. Combined heat conduction within the metal hydride and the enhancing material particles, across the contacts of particles and within the hydrogen gas between non-contacted particles plays a critical role in dissipating heat to sustain high reaction rates during refueling. Methods to increase the effective thermal conductivity of metal hydride powders include using additives with substantially higher thermal conductivity such as aluminum, graphite, metal foams and carbon nanotubes. This paper presents the results of experimental studies in which various thermal enhancement materials are added to the metal hydride powder in an effort to maximize the effective thermal conductivity of the test bed. The size, aspect ratio, and intrinsic thermal conductivity of the enhancement materials are taken into account to adapt heat conduction models through composite nanoporous media. Thermal conductivity and density of the composite materials are measured and enhancement metrics are calculated to rate performance of composites. Experimental results of the hydriding process of thermally enhanced metal hydride powder are compared to un-enhanced metal hydride powder and to model predictions. The development of the Hydrogen Systems Laboratory is also discussed in light of the lessons learned in managing large quantities of metal hydride and high pressure hydrogen gas.

scholarly journals A Study of Control Methodologies for the Trade-Off between Battery Aging and Energy Consumption on Electric Vehicles with Hybrid Energy Storage Systems

Energies ◽  
2022 ◽  
Vol 15 (2) ◽  
pp. 600
Author(s):  
Kevin Mallon ◽  
Francis Assadian
Keyword(s):  
Energy Consumption ◽  
Energy Storage ◽  
Electric Vehicle ◽  
Energy Management ◽  
Storage Systems ◽  
Storage System ◽  
Energy Storage System ◽  
Trade Off ◽  
Hybrid Energy ◽  
Hybrid Energy Storage

Hybrid and electric vehicle batteries deteriorate from use due to irreversible internal chemical and mechanical changes, resulting in decreased capacity and efficiency of the energy storage system. This article investigates the modeling and control of a lithium-ion battery and ultracapacitor hybrid energy storage system for an electric vehicle for improved battery lifespan and energy consumption. By developing a control-oriented aging model for the energy storage components and integrating the aging models into an energy management system, the trade-off between battery degradation and energy consumption can be minimized. This article produces an optimal aging-aware energy management strategy that controls both battery and ultracapacitor aging and compares these results to strategies that control only battery aging, strategies that control battery aging factors but not aging itself, and non-optimal benchmark strategies. A case study on an electric bus with variously-sized hybrid energy storage systems shows that a strategy designed to control battery aging, ultracapacitor aging, and energy losses simultaneously can achieve a 28.2% increase to battery lifespan while requiring only a 7.0% decrease in fuel economy.

scholarly journals Influence of Efficiency, Aging and Charging Strategy on the Economic Viability and Dimensioning of Photovoltaic Home Storage Systems

Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7673
Author(s):  
Nina Munzke ◽  
Felix Büchle ◽  
Anna Smith ◽  
Marc Hiller
Keyword(s):  
Large Scale ◽  
Storage Systems ◽  
Storage System ◽  
Energy Transition ◽  
Pv System ◽  
Technical Parameters ◽  
Economic Framework ◽  
Ion Storage ◽  
Framework Conditions ◽  
Charging Strategy

PV in combination with Li-ion storage systems can make a major contribution to the energy transition. However, large-scale application will only take place when the systems are economically viable. The profitability of such a system is not only influenced by the investment costs and economic framework conditions, but also by the technical parameters of the storage systems. The paper presents a methodology for the simulation and sizing of PV home storage systems that takes into account the efficiency of the storage systems (AC, DC standby consumption and peripheral consumption, battery efficiency and inverter efficiency), the aging of the components (cyclic and calendar battery aging and PV degradation), and the intelligence of the charging strategy. The developed methodology can be applied to all regions. In this paper, a sensitivity analysis of the influence of the mentioned technical parameters on the dimensioning and profitability of a PV home storage is performed. The calculation is done for Germany. Especially, battery aging, battery inverter efficiency and a charging strategy to avoid calendar aging have a decisive influence. While optimization of most other technical parameters only leads to a cost reduction of 1–3%, more efficient inverters can save up to 5%. Even higher cost reductions (more than 20%) can only be achieved using batteries that age less, especially batteries that are less sensitive to calendar aging. In individual cases, a small improvement in the efficiency of the storage system can also lead to higher costs. This is for example the case when smaller batteries are combined with a large PV system and the battery is used more due to the higher efficiency. This results in faster ageing and thus earlier replacement of the battery. In addition, the paper includes a detailed literature overview on PV home storage system sizing and simulation.

scholarly journals Hydrogen as a Long-Term Large-Scale Energy Storage Solution to Support Renewables

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2825 ◽  
Author(s):  
Subodh Kharel ◽  
Bahman Shabani
Keyword(s):  
Energy Storage ◽  
Hydrogen Storage ◽  
Large Scale ◽  
Storage Systems ◽  
Storage System ◽  
Unit Cost ◽  
South Australia ◽  
Point Of View ◽  
Cost Of Electricity

This paper presents a case study of using hydrogen for large-scale long-term storage application to support the current electricity generation mix of South Australia state in Australia, which primarily includes gas, wind and solar. For this purpose two cases of battery energy storage and hybrid battery-hydrogen storage systems to support solar and wind energy inputs were compared from a techno-economical point of view. Hybrid battery-hydrogen storage system was found to be more cost competitive with unit cost of electricity at $0.626/kWh (US dollar) compared to battery-only energy storage systems with a $2.68/kWh unit cost of electricity. This research also found that the excess stored hydrogen can be further utilised to generate extra electricity. Further utilisation of generated electricity can be incorporated to meet the load demand by either decreasing the base load supply from gas in the present scenario or exporting it to neighbouring states to enhance economic viability of the system. The use of excess stored hydrogen to generate extra electricity further reduced the cost to $0.494/kWh.

scholarly journals Dynamic Modelling and Techno-Economic Assessment of a Compressed Heat Energy Storage System: Application in a 26-MW Wind Farm in Spain

Energies ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 4739 ◽  
Author(s):  
Violeta Sánchez-Canales ◽  
Jorge Payá ◽  
José M. Corberán ◽  
Abdelrahman H. Hassan
Keyword(s):  
Energy Storage ◽  
Power Plant ◽  
Electricity Market ◽  
Large Scale ◽  
Storage Systems ◽  
Capital Expenditure ◽  
Renewable Energy Sources ◽  
Storage System ◽  
Dynamic Modelling ◽  
Heat Energy

One of the main challenges for a further integration of renewable energy sources in the electricity grid is the development of large-scale energy storage systems to overcome their intermittency. This paper presents the concept named CHEST (Compressed Heat Energy STorage), in which the excess electricity is employed to increase the temperature of a heat source by means of a high-temperature heat pump. This heat is stored in a combination of latent and sensible heat storage systems. Later, the stored heat is used to drive an organic Rankine cycle, and hereby to produce electricity when needed. A novel application of this storage system is presented by exploring its potential integration in the Spanish technical constraints electricity market. A detailed dynamic model of the proposed CHEST system was developed and applied to a case study of a 26-MW wind power plant in Spain. Different capacities of the storage system were assessed for the case under study. The results show that roundtrip efficiencies above 90% can be achieved in all the simulated scenarios and that the CHEST system can provide from 1% to 20% of the total energy contribution of the power plant, depending on its size. The CHEST concept could be economically feasible if its capital expenditure (CAPEX) ranges between 200 and 650 k€/MW.

Rethinking key–value store for parallel I/O optimization

2016 ◽  
Vol 31 (4) ◽  
pp. 335-356 ◽  
Author(s):  
Anthony Kougkas ◽  
Hassan Eslami ◽  
Xian-He Sun ◽  
Rajeev Thakur ◽  
William Gropp
Keyword(s):  
Cloud Storage ◽  
Large Scale ◽  
Storage Systems ◽  
Storage System ◽  
File Systems ◽  
Data Synchronization ◽  
Input Output ◽  
Parallel File Systems ◽  
Parallel File ◽  
And Performance

Key–value stores are being widely used as the storage system for large-scale internet services and cloud storage systems. However, they are rarely used in HPC systems, where parallel file systems are the dominant storage solution. In this study, we examine the architecture differences and performance characteristics of parallel file systems and key–value stores. We propose using key–value stores to optimize overall Input/Output (I/O) performance, especially for workloads that parallel file systems cannot handle well, such as the cases with intense data synchronization or heavy metadata operations. We conducted experiments with several synthetic benchmarks, an I/O benchmark, and a real application. We modeled the performance of these two systems using collected data from our experiments, and we provide a predictive method to identify which system offers better I/O performance given a specific workload. The results show that we can optimize the I/O performance in HPC systems by utilizing key–value stores.

Energy Storage System Survey and Battery Case Testing

2013 ◽  
Author(s):  
Inderjeet Duggal ◽  
Bala Venkatesh
Keyword(s):  
Energy Storage ◽  
Large Scale ◽  
Storage Systems ◽  
Storage System ◽  
Energy Storage System ◽  
Frequency Regulation ◽  
Energy Storage Systems ◽  
Battery System ◽  
Control Frequency ◽  
Battery Case

Energy storage and renewables are important parts of smart grid systems of the future. This paper surveys applications of energy storage systems. It reviews various types of battery systems, flywheels, compressed air energy storage systems and thermal energy storage systems. Then the paper surveys all possible uses of energy storage systems such as volt-var control, frequency regulation, energy arbitrage, etc. Thereafter, the paper presents a proposed testing of large scale battery system at Ryerson University using a 1.2 MWh of battery storage system with a 370 kW converter system connecting a 13.8 kV substation. Detailed system architecture is presented that includes details of the battery system, power electronics, etc. The proposed tests to be completed are outlined explaining potential outcomes in those tests.

Tiered Adaptive Large-Scale Storage System with High Performance

2013 ◽  
Vol 380-384 ◽  
pp. 2371-2374
Author(s):  
Lei Zhang ◽  
Li Gu Zhu ◽  
Sai Feng Zeng
Keyword(s):  
High Performance ◽  
Large Scale ◽  
Storage Systems ◽  
Storage System ◽  
Data Access ◽  
Traffic Load ◽  
Full Potential ◽  
Storage Devices ◽  
Reliability Characteristics ◽  
Cluster Storage

There are various calculations, transmission, and storage devices in terms of performance or reliability characteristics in great physical differences exist of large-scale cluster storage systems. Meanwhile, the actual traffic load data access for storage devices is also not uniform in space and time and there is a big difference. It is unrealistic and unwise if all the data stored on the high-performance devices. In order to resolve this problem effectively, we propose large-scale adaptive tiered storage system architecture in which structure can carry out effective monitoring access to the load and adapting allocation of storage resources based on the application environment. This can fulfill the full potential to the advantages of high-performance storage nodes to improve the performance of large-scale clustered storage systems.

Modeling an Energy Storage System Based on a Hybrid Renewable Energy System in Stand-alone Applications

2017 ◽  
Vol 68 (11) ◽  
pp. 2641-2645
Author(s):  
Alexandru Ciocan ◽  
Ovidiu Mihai Balan ◽  
Mihaela Ramona Buga ◽  
Tudor Prisecaru ◽  
Mohand Tazerout
Keyword(s):  
Renewable Energy ◽  
Energy Storage ◽  
Storage Systems ◽  
Renewable Energy Sources ◽  
Storage System ◽  
Energy Storage System ◽  
Compressed Air ◽  
Energy Sources ◽  
Energy Storage Systems ◽  
Hybrid Renewable Energy System

The current paper presents an energy storage system that stores the excessive energy, provided by a hybrid system of renewable energy sources, in the form of compressed air and thermal heat. Using energy storage systems together with renewable energy sources represents a major challenge that could ensure the transition to a viable economic future and a decarbonized economy. Thermodynamic calculations are conducted to investigate the performance of such systems by using Matlab simulation tools. The results indicate the values of primary and global efficiencies for various operating scenarios for the energy storage systems which use compressed air as medium storage, and shows that these could be very effective systems, proving the possibility to supply to the final user three types of energy: electricity, heat and cold function of his needs.

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