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Abstract The improvement of thermodynamic efficiency of power plants is of great interest for the whole energy industry. The use of Kalina cycle has a great potential to improve the thermal efficiency of a nuclear power plant. This cycle uses a mixture of ammonia and water as working fluid. In this paper, we discuss the development of an Ammonia-Water mixture Property Code (AWProC). The estimation of the mixture properties are based on the Gibbs free energy functions. The code is verified and validated against experimental data available in the literature and REFPROP code. It is shown that AWProC can accurately estimate the thermodynamic properties of ammonia-water mixtures over a wide range of conditions, including high temperature and pressure regions. The code is then used to investigate the feasibility of applying the Kalina cycle to a typical Pressurizer Water Reactor (PWR) plant as an effective way to improve the plant efficiency. The fundamental of Basic-Kalina (B-K) cycle is described in detail firstly. Then, two modified configurations, Recuperation-Kalina (R-K) and Flash-Kalina (F-K) cycles respectively, are proposed for a typical 1000 MWe PWR. The simulation results indicate that the R-K type cycle can reach about 31.2% efficiency with simple equipment requirements, while the F-K type cycle can reach efficiencies up to about 34.8%, but at the expenses of a slightly more complex design. The present work demonstrates the applicability of the Kalina cycle as a way to improve the thermal efficiency of a nuclear power plant. This concept is meaningful for improving nuclear power plants economic and competitiveness.

In this paper, we compare 2015 satellite-derived natural gas (gas) flaring data with the greenhouse gas reduction targets presented by those countries in their nationally determined contributions (NDC) under the United Nations Framework Convention on Climate Change (UNFCCC) Paris Agreement. Converting from flaring to utilization is an attractive option for reducing emissions. The analysis rates the potential role of reduction of gas flaring in meeting country-specific NDC targets. The analysis includes three categories of flaring: upstream in oil and gas production areas, downstream at refineries and transport facilities, and industrial (e.g., coal mines, landfills, water treatment plants, etc.). Upstream flaring dominates with 90.6% of all flaring. Global flaring represents less than 2% of the NDC reduction target. However, most gas flaring is concentrated in a limited set of countries, leaving the possibility that flaring reduction could contribute a sizeable portion of the NDC targets for specific countries. States that could fully meet their NDC targets through gas flaring reductions include: Yemen (240%), Algeria (197%), and Iraq (136%). Countries which could meet a substantial portion of their NDC targets with gas flaring reductions include: Gabon (94%), Algeria (48%), Venezuela (47%), Iran (34%), and Sudan (33%). On the other hand, several countries with large flared gas volumes could only meet a small portion of their NDC targets from gas flaring reductions, including the Russian Federation (2.4%) and the USA (0.1%). These findings may be useful in guiding national level efforts to meet NDC greenhouse gas reduction targets. Keywords: VIIRS, Gas flaring, Nightfire, Nationally determined contributions, UN climate agreement

This article is categorized under: Energy Research & Innovation > Science and Materials Energy Research & Innovation > Economics and Policy Energy Research & Innovation > Systems and Infrastructure Energy Research & Innovation > Climate and Environment

Abstract This paper summarises studies undertaken towards the development of a laminated composite aluminium/hexadecane phase change material (PCM) drywall based on previous analytical work. The study also covered the selection and testing of various types of adhesive materials and identified Polyvinyl acetate (PVA) material as a suitable bonding material. For the purpose of comparison pure hexadecane and composite aluminium/hexadecane samples were developed and tested. The test results revealed faster thermal response by the aluminium/hexadecane sample regarding the rate of heat flux and also achieved about 10% and 15% heat transfer enhancements during the charging and discharging periods respectively. Its measured effective thermal conductivity also increased remarkably to 1.25 W/mK as compared with 0.15 W/mK for pure hexadecane. However there was about 5% less total cumulative thermal energy discharged at the end of the test which indicates that its effective thermal capacity was reduced by the presence of the aluminium particles. The study has shown that some of the scientific and technical barriers associated with the development of laminated composite PCM drywall systems can be overcome but further investigations of effects of adhesive materials are needed.

Chemical looping combustion allows the carbon dioxide capture by using an oxygen carrier, which transports the oxygen required for combustion from the air to the fuel. But complete combustion of a solid fuel is not achieved when low cost materials were used as oxygen carriers. Manganese‑iron mixed oxide doped with titanium has been identified as a promising oxygen carrier to improve combustion efficiency due to its oxygen uncoupling capability. The objective of this work was to assess the potential of this oxygen carrier when burning coal in a chemical looping unit. The coal combustion efficiency and carbon dioxide capture were evaluated as a function of the operating conditions both in the fuel and air reactor. Carbon dioxide capture was affected by the solids residence time in the fuel reactor. Coal combustion efficiency increased as the oxygen uncoupling capability was enhanced by using suitable operating conditions in the air reactor. Almost full coal combustion (99.4%) was achieved by setting an air reactor temperature of 880 °C, an air excess of 1.8, a fuel reactor temperature of 925 °C, and an oxygen carrier to fuel ratio >3. The oxygen carrier showed magnetic properties, allowing its re-use after being separated from ash. This work was partially supported by the project ENE2016-77982-R (AEI/FEDER, UE) and project ENE2017-89473R (AEI/FEDER, UE), and by the Consejo Superior de Investigaciones Científicas (CSIC project: 2017-80E035). 10 Figures, 4 Tables.-- © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/ Peer reviewed

Abstract A LOWTRAN 5 based flux model has been developed to calculate downwelling infrared irradiance from a clear night atmosphere onto a horizontal or tilted surface. This model is based on the transmittance/radiance code LOWTRAN 5 which can calculate the radiance from the atmosphere for user defined paths, atmospheric conditions and spectral intervals. Included in the model is the addition of a zeroth order scattering approximation to the LOWTRAN 5 code, methods of integrating LOWTRAN 5 calculated radiances over the sky hemisphere to obtain the downwelling flux, and a method for calculating the radiance from the atmosphere at wavenumbers outside the range of LOWTRAN 5. The accuracy of this model is verified by comparison of calculations based on radiosonde data with surface flux measurements taken concurrent with radiosonde ascent. Agreement is excellent for both horizontal and tilted surfaces with the deviation between measurements and calculations of the flux on a horizontal surface being less than 4 per cent.

Abstract Natural gas has been promoted as a ‘‘bridge’’ fuel toward a low-carbon future by offering near-term emissions reductions at lower cost. Existing literature is inconclusive on the short-term emissions benefits of more abundant natural gas. The long-lived nature of natural gas infrastructure also threatens to lock in emissions levels well above longer-term targets. If natural gas can offer short-to-medium term benefits, how much of a bridge should we build? Using ARTIMAS, a foresighted computable general equilibrium model of the US economy, we interact scenarios developed by the EMF-34 study group related to abundant natural gas, low-cost renewables, and a carbon tax to examine the role of natural gas in a carbon-constrained future. We find that abundant natural gas alone does not have a significant impact on CO2 emissions. We also find that, under a higher carbon tax, natural gas investment of approximately $10 billion per year declines to zero at a tax of about $40/ton and existing natural gas assets face significant risk of impairment. Last, the presence of abundant natural gas lowers the marginal welfare cost of abating small amounts of CO2 but is likely to raise the cost of abatement levels consistent with common climate objectives. The integrated welfare costs of climate policy depend on how much abatement we must undertake.

In this study, the effect of recycling the non-condensable gases (NCG) in the catalytic pyrolysis of hybrid poplar using FCC catalyst was investigated. A 50mm bench scale fluidized bed reactor at 475°C with a weight hourly space velocity (WHSV) of 2h(-1) and a gas recycling capability was used for the studies. Model fluidizing gas mixtures of CO/N(2), CO(2)/N(2), CO/CO(2)/N(2) and H(2)/N(2) were used to determine their independent effects. Recycling of the NCG in the process was found to potentially increase the liquid yield and decrease char/coke yield. The model fluidizing gases increased the liquid yield and the CO(2)/N(2) fluidizing gas had the lowest char/coke yield. The (13)C-NMR analysis showed that recycling of NCG increases the aromatic fractions and decreases the methoxy, carboxylic and sugar fractions. Recycling of NCG increased the higher heating value and the pH of the bio-oil as well as decreased the viscosity and density.