Sustaining economic growth while reducing reliance on fossil fuels for environmental protection is a global challenge. Efforts are made to decrease energy utilization by enhancing energy efficiency and discovering clean, renewable energy sources. Cryogenic energy storage (CES) is a grid-scale energy system where electricity is stored in the form of liquefied air. It is regarded as a solution because it allows for increased electricity generation while also providing economic benefits by avoiding costly operational consequences. The three CES system configurations: standalone adiabatic, waste heat integration, and combustion integration were modelled and simulated in Aspen HYSY V8.8. Unlike in the conventional CES, Dowtherm-Q was used as the thermal fluid due to its thermal stability, non-corrosiveness, and high temperature resistance.
The results indicated that the higher the adiabatic efficiency of the turbine, the greater the power generated; also, increasing the turbine inlet temperature enhanced the performance of the system configuration by lowering the pressure and increasing the power of the turbine. The economic analysis revealed that the waste heat-based system has both the lowest operating cost, capital cost, utility cost, and higher energy savings. Waste heat integration produces the most power (653.70 KW) and saves the most energy (69.58%), with lower capital costs, operating costs, and utility costs due to the increased adiabatic efficiency of the turbine. It implies that CES with waste heat integration is economically more promising compared to adiabatic standalone and the integration of combustion.
Table of Contents
1. INTRODUCTION
1.0 Background
1.2 Aim and Objectives of the Study
1.3 Significance of the Study
1.4 Scope of Study
1.5 Limitation
2. LITERATURE REVIEW
2.1 Liquid Air Energy Storage Generation, Storage and Utilization
2.2 Developments in cryogenic energy storage
2.3 Configurations of Adiabatic cryogenic energy storage systems
2.3.1. Principle of operation of a CES system
2.3.2. System Design and Operational Parameters
2.4 Charging Processes of a CES
2.4.1 Liquefaction process
2.4.2 Cold Storage Configurations assessed in the context of CES
2.5 Discharging Processes Configurations assessed in the context of CES
2.6 System integration
2.7 Classification, characteristics and benchmarking of Energy Storage technologies
2.7.2 Characteristics of Energy Storage technologies
2.8 Sensitivity Analysis of CES system
2.9 Economic analysis of CES system
2.9.1 Capital Expenditures (CAPEX)
2.9.2 Operating expenditure (OPEX)
2.9.3 Utilities Expense
2.9.4 Desired rate of return
3. MATERIALS and METHODS
3.1 Materials
3.1.1 Aspen HYSYS V8.8
3.1.2 Description of the various Aspen HYSYS components or the blocks of CES system
3.1.2.1 Compressor (CM)
3.1.2.2 Cooler (C)
3.1.2.3 Splitter (TEE-100)
3.1.2.4 Expander (EX)
3.1.2.5 Mixer (MIX-100)
3.1.2.6 Heat Exchangers (cold box, heat box)
3.1.2.7 Throttling Valve (TV)
3.1.2.8 Flash Separator (FS)
3.1.2.9 Tank (CT)
3.1.2.10 Pump (CP)
3.1.2.11 Heater (H)
3.1.2.12 Recycler (RCY-1)
3.3.2 Assumptions made in the simulation
3.4 Process Flow Description of the Cryogenic Energy Storage System Configurations
3.5.1 Method of sensitivity analysis
3.5.2 Steps used to conduct sensitivity analysis
3.6 Economic analysis
4. RESULTS and DISCUSSION
4.1 Modelling and Simulation of CES System
4.2 Sensitivity Analysis
4.3 Economic Analysis
5. CONCLUSION and RECOMMENDATION
5.1. Conclusion
5.2. Recommendations
Research Objectives and Thematic Focus
This study aims to perform a comprehensive techno-economic evaluation of cryogenic energy storage (CES) systems to determine their viability as a solution to grid-scale energy storage challenges in regions like Nigeria. By utilizing process simulation software, the research identifies the most efficient and economically promising operational configuration among three specific system designs.
- Techno-economic modeling and steady-state simulation of CES configurations using Aspen HYSYS.
- Comparative analysis of standalone adiabatic, waste heat integrated, and combustion integrated storage systems.
- Implementation of parameter sensitivity analysis to evaluate system performance regarding adiabatic efficiency, power generation, and temperature variables.
- Economic assessment involving CAPEX, OPEX, utility costs, and energy savings to identify the optimal configuration.
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3.4.1 Simulation of adiabatic standalone CES system configuration (C ASE A)
With the aid of the simulation software Aspen HYSYS, the CASE A, was simulated as shown in Figure 3.2 with the ambient temperature at 15 °C, the ambient pressure at 1.0 bar, according to the International Standard Atmosphere and a molar fraction of 0.79 for nitrogen and 0.21 for oxygen. In all systems, the inlet air to the compressor had a mass flow rate of 198.3 kg/s which was compressed to a pressure of 180 bar in a three-stage compression process, to regulate the air temperature so that the output air has the lower temperature with intercooling to 18–20 °C (Hamdy, 2019a). Thermal fluid (DOWTHERM-Q with 303 kg/s, 6 bar and 360 °C.) was used as a heat storage medium to recover and store the heat of compression. The high pressure air was further cooled and expanded until the dew point was reached. The slightly sub cooled liquid air exits the flasher and was stored in a simple cryogenic insulated storage vessel at near ambient pressure (1.1 bar) and a temperature of - 194 °C.
During discharge, the liquid air is pressurized to 150 bar, evaporated in heat exchange to the cold storage media, superheated and fed to the four stage expander with reheater. The cold storage uses two fluid tanks and two circulating working fluids number of refrigerants, R218 and methanol are shown to be advantageous with respect to toxicity, flammability, boiling and freezing temperatures. The cold in the temperature interval −180 to −61 °C is recovered by R218, while the cold at higher temperatures (−19 to −59 °C) is captured and stored using methanol. The amount of cold recovered is determined by the amount of air liquefied in the ratio of the mass flow rate of the liquefied air in liquefaction process. The mass flow rates of the cold storage media are therefore determined by the following expression (Hamdy et al., 2019).
Summary of Chapters
1. INTRODUCTION: This chapter defines the global challenges regarding energy supply and environmental sustainability, and introduces cryogenic energy storage as a versatile grid-scale solution.
2. LITERATURE REVIEW: The section covers existing cryogenic energy storage technologies, configurations, and the state of the art in charging and discharging processes, including economic factors and previous research findings.
3. MATERIALS and METHODS: This chapter outlines the software tools, specifically Aspen HYSYS, and the step-by-step methodologies used to model, simulate, and conduct sensitivity and economic analyses of the various system configurations.
4. RESULTS and DISCUSSION: This chapter presents the simulation outputs, graphical results of the sensitivity analysis regarding power generation and efficiency, and the subsequent economic comparison of the considered cases.
5. CONCLUSION and RECOMMENDATION: The final chapter summarizes the findings, highlighting that waste heat integration is the most promising configuration, and provides suggestions for future research in system optimization.
Keywords
Cryogenic energy storage (CES), Liquid Air Energy Storage (LAES), Techno-economic analysis, Aspen HYSYS, Power generation, Adiabatic efficiency, Waste heat recovery, Combustion integration, Economic viability, Grid-scale storage, Thermal energy storage, Sensitivty analysis, CAPEX, OPEX, System simulation.
Frequently Asked Questions
What is the primary focus of this dissertation?
The work focuses on the techno-economic performance of different cryogenic energy storage (CES) system configurations to assess their feasibility for grid-scale energy management.
What are the main research themes covered?
Key themes include the modeling and simulation of storage architectures, thermodynamic efficiency, energy storage, heat recovery, and capital/operating expenditure calculations.
What is the core objective of the research?
The objective is to model and simulate three specific CES configurations using Aspen HYSYS, perform sensitivity analysis, and identify the most economically promising operational model.
Which scientific methodology is employed?
The research uses process modeling and simulation techniques, incorporating mass and energy balances and thermodynamic property estimation within the Aspen HYSYS software environment.
What topics are discussed in the main analysis?
The main sections cover existing developments in cryogenic storage, the theoretical principles of charge/discharge processes, simulation assumptions, and the comparative results of three distinct design cases.
How are the results characterized by key terms?
The results are characterized by terms such as system integration, power output, capital costs, efficiency, and energy savings.
Why is DOWTHERM-Q used as a thermal fluid in this study?
DOWTHERM-Q is selected for its superior thermal stability, non-corrosiveness, and high-temperature resistance compared to conventional options like pressurized water or hot oils.
Which storage configuration demonstrates the best economic performance?
The analysis concludes that the "waste heat integration" configuration is the most economically promising, offering the lowest operating and capital costs along with higher energy savings.
How does adiabatic efficiency impact the power of the turbine?
The research demonstrates a positive correlation where higher adiabatic efficiency leads to an increase in both pressure regulation and the total power generated by the turbine.
- Quote paper
- Zakiyyu Muhammad Sarkinbaka (Author), 2024, Techno-Economic Analysis of a Modular Cryogenic Energy Storage System, Munich, GRIN Verlag, https://www.grin.com/document/1465891
