Techno-economic Analysis of Different Liquid Air Energy Storage Configurations

With the increasing use of renewables in energy systems, grid stability becomes a major issue due to the intermittent nature of energy sources such as solar and wind. To compensate for the unstable renewable energy sources, storage technologies have been regarded as effective methods. Liquid air energy storage (LAES) has gained wide attention due to its inherent advantages: geographically unconstrained and high energy density. This work presents a techno-economic analysis of an LAES system with a storage capacity of 10 MW / 80 MWh. Three different layouts of the LAES are evaluated and compared based on net present value (NPV) and payback period. The economic results show that the LAES system with a 2-stage compressor and a 3-stage expander (Case 1) has the largest NPV of 918.1 M$, which is 33.7 % and 10.7 % larger than a system with a 4-stage compressor and a 4-stage expander without (Case 2) / and with (Case 3) an additional Organic Rankine Cycle (ORC). In addition, the shortest payback period of 6.2 y is obtained in Case 1 compared to 6.9 and 6.4 y for Cases 2 and 3. This means that Case 1 is the most profitable layout for the studied LAES systems. Copyright © 2022, AIDIC Servizi S.r.l.Techno-economic Analysis of Different Liquid Air Energy Storage ConfigurationspublishedVersio

Relative Age Effect Among the Best Norwegian Track and Field Athletes of All Time: Comparisons of Explosive and Endurance Events

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Energy, economic and environmental analysis of a BOG re-liquefaction process for an LNG carrier

Due to tighter environmental regulations, newly built liquefied natural gas (LNG) carriers are equipped with a re-liquefaction system to minimize combustion of surplus boil-off-gas (BOG). Thus, this paper comparatively analyzes the re-liquefaction system for a low-pressure gas injection engine according to the refrigerant (no external refrigerant or single mixed refrigerant) with three key performance indicators: energy, economic, and environmental aspects. For an energy efficiency analysis, we proposed several process alternatives and optimized them to minimize the specific power consumption required to liquefy BOG. In economic analysis, minimizing total annualized cost is the objective. For an environmental analysis, CO2 emissions at each optimal point is calculated and comparatively analyzed. The results show that the process without external refrigerant has 10% better performance in terms of economy, while the single mixed refrigerant process is suitable in terms of energy efficiency (6%) and environmental (15%) impact.Energy, economic and environmental analysis of a BOG re-liquefaction process for an LNG carrierpublishedVersio

Decadal trends in ocean acidification from the Ocean Weather Station M in the Norwegian Sea

The Ocean Weather Station M (OWSM) is situated at a fixed position in the Norwegian Sea, one of the major basins of the Nordic Seas, which represents an important area for uptake of atmospheric CO2 as well as deep water formation. At OWSM, the inorganic carbon cycle has been regularly monitored since 2001, and significant interannual changes of the carbonate system have been determined. Data collected at this site since the 1990s have been included, and over the 28 last years the surface fugacity of CO2 (fCO2) has increased by 2.92 ± 0.37 μatm/yr, while surface pH and aragonite saturation (ΩAr) have decreased by -0.0033 ± 0.0005/yr and -0.018 ± 0.003/yr, respectively. This corresponds to a surface pH change of -0.092 over 28 years, which is comparable to the global mean pH decrease of -0.1 since the onset of the industrial revolution. Our estimates suggest that 80% of the surface pH trend at OWSM is driven by uptake of CO2 from the atmosphere. In the deepest layer, ΩAr has decreased significantly (-0.006 ± 0.001/yr) over the last 28 years, now occasionally reaching undersaturated values (ΩAr < 1). As a rough estimate, the saturation horizon has shoaled by 7 m/yr between 1994 and 2021. The increase in surface fCO2 is confirmed by semi-continuous measurements of CO2 from the site (2.69 ± 0.14 μatm/yr), and thus, the area has become less of a net sink for atmospheric CO2, taking into consideration an atmospheric CO2 increase at OWSM of 2.27 ± 0.08 μatm/yr.publishedVersio

Work and Heat Integration: An emerging research area

The extension from Heat Integration (HI) and design of Heat Exchanger Networks (HENs) to including heating and cooling effects from pressure changing equipment has been referred to as Work and Heat Integration and design of Work and Heat Exchange Networks (WHENs). This is an emerging research area of Process Synthesis, however, WHENs is a considerably more complex design task than HENs. A key challenge is the fact that temperature changes (related to heat) and pressure changes (related to work) of process streams are interacting. Changes in inlet temperatures to compressors and expanders resulting from heat integration will influence work consumption and production. Likewise, pressure changes by compression and expansion will change the temperatures of process streams, thus affecting heat integration. As a result, Composite and Grand Composite Curves will change shape due to pressure changes in the process. The thermodynamic path of process streams from supply (pressure, temperature) to target state is not known and depends on the sequence of heating, cooling, compression and expansion. This paper introduces a definition and describes the development of WHENs. Future research challenges related to methodology development and industrial applications will be addressed. The potential of WHENs will be indicated through examples in literature.Work and Heat Integration: An emerging research areaacceptedVersio

Work Exchange Networks (WENs) and Work and Heat Exchange Networks (WHENs): A review of the current state of the art

This paper provides a current state-of-the-art review of literature on work exchange networks (WENs) and work and heat exchange networks (WHENs). Heat exchange networks (HENs) and mass exchange networks (MENs) have been widely adopted and extensively studied for heat and material recovery to save energy and other resources. However, work recovery can also result in significant energy savings in the process industries, such as oil refineries, petrochemical plants, and cryogenic processes (e.g., the production of liquefied natural gas (LNG) and air separation units (ASUs)). The concept of WENs was first proposed and identified as a new research topic in process synthesis in 1996. This research area has broadened considerably during the last 5–10 years, and it covers both flow work (material streams) and shaft work (energy streams or nonflow processes). Flow work recovery is referred to as direct work exchange and shaft work recovery is referred to as indirect work exchange. More recently, there has also been considerable development in the combined problem of WENs and HENs. This problem is referred to as work and heat exchange networks (WHENs). The WHENs problem is generally studied by pinch based methods and mathematical programming. The corresponding literature is reviewed, analyzed, and compared in this paper. The present review covers WENs (both flow work and shaft work) and WHENs (with a focus on both mechanical energy and thermal energy). The development progress, current state, challenges, and future research in WENs and WHENs are discussed and analyzed thoroughly.acceptedVersio

The importance of thermodynamic insight in Work and Heat Exchange Network Design

Work and Heat Exchange Network (WHEN) design has been an emerging topic in the area of Process Synthesis and has attracted increasing research interest in the past few years. Not only temperature changes but also pressure changes of process streams have been taken into consideration in WHEN design. As a result, pressure changing equipment such as compressors, expanders, pumps, valves, etc., as well as traditional heat exchange equipment is included in WHEN design. Similar to HEN design problems, both graphical and mathematical optimization approaches have been under development for WHEN design. The graphical approaches utilize fundamental thermodynamic insight while mathematical optimization approaches enable dealing with large size problems. This paper focuses on a comparison between the graphical and mathematical optimization approaches for WHEN design. A case study is used to illustrate the importance of thermodynamic insight in WHEN design even in the case of using mathematical optimization approaches.publishedVersio

Use of exergy efficiency for the optimization of LNG processes with NGL extraction

In this paper, processes for liquefied natural gas (LNG) production with upstream or integrated natural gas liquids (NGL) removal have been optimized and compared. Since the NGL and LNG production systems use both work and heat to deliver products with different energy quality, it is challenging to measure accurately the thermodynamic efficiency by using conventional energy performance indicators. Thus, two different objective functions, specific energy consumption and exergy efficiency, have been applied in the optimization of these complex systems in order to evaluate the effectiveness of the two performance indicators. The results indicate that use of the exergy-based objective function results in a richer NGL and a larger amount of LNG production with a marginal increase in energy consumption, showing a higher thermodynamic efficiency than the result with the energy-based objective function. Besides, integrated NGL extraction shows a lower thermodynamic performance than upstream removal, indicating that further advanced schemes are required for effective integration of the NGL extraction part in the LNG process