Abstract

The load ratio of transformers could be improved with the integration of distributed generators. A calculation method for the maximum load ratio of transformer is proposed considering the distributed PV and storage. The feature of the method is that the distributed PV and storage system is handled as a special transformer, whose power supply capability is zero while improving other transformers’ load ratio. Taking power supply reliability as core index, the maximum load ratio values of transformers are explored. The effectiveness of the proposed method is verified by simulation results.

Abstract

Geological carbon dioxide (CO2) sequestration is the most sought after method to store CO2 in supercritical form. Of all the geological formations, deep saline aquifer are preferred due to their high storage capacities and wide availability. A saline aquifer based in Shuaiba formation of the United Arab Emirates, situated at a depth of 3000 m has been investigated. A numerical model has been developed in an open source code STOMP and sensitivity of CO2 plume to parameters such as salinity and Corey residual gas saturation has been studied. The results for total CO2 mass (aqueous and gas CO2) are plotted as a function of simulated time. The results show that the effect of salinity and Corey residual gas saturation is significant. The cost of CO2 storage in such deep saline aquifers is also estimated. The source of CO2 is considered from a chemical looping reforming plant producing hydrogen and capturing about 0.73 Mt/year. The cost of CO2 storage is estimated to be $4.58 per ton of CO2 stored. The results obtained are promising, however, more comprehensive assessments are required in order to increase the accuracy of the costs.

Abstract

With the rapid growth of electric vehicle (EV), EV charging load has a significant impact on the safe operation of the power grid. An ordered charging control strategy is proposed in the paper based on differentiated charging price. In the strategy, different charging prices, which are aimed at mobilizing the participation of ordered charging behavior, are accessible for EV users. In nature, relatively lower charging price is for the EV user’s license of the translation of EV charging load, i.e., the EV charging load is permitted to be moved to expected period during which the grid is with valley electricity load. The effectiveness of the proposed method is verified by the analysis of the benefits of various stakeholders.

Abstract

This paper evaluates a novel cryogenic carbon capture process to upgrade biogas produced from agricultural waste. The A3C cryogenic process offers simplicity and compactness with lower capital and operating costs compared to many alternative processes. The work addresses potential technical issues presented by trace contaminants in the raw biogas including hydrogen sulphide, organics and siloxanes. It is found that the A3C process offers high CO2 removal with minimal biomethane losses while requiring simple raw gas treatment.

Abstract

Microthrusters are special category of propulsion device used to propel micro sized satellites. It is designed as per the mission requirements. There are various kinds of propulsion requirements such as continuous mode operation for orbit transfer (from one planet to another), orbit shift or adjustment for asteroid mining, pulsed mode operation for attitude control of satellites, and gravitation or solar drag compensation in orbit. Continuous mode operation is a high propellant consuming operation and designed cautiously to reach the destination with onboard available propellant. While pulsed mode operation is widely used for LEO (Low earth orbit) applications, where gravitation drag, atmospheric drag and solar drags are dominating. This paper focuses on the pulsed mode operation of vaporization liquid microthruster in vacuum operating condition. The pulsed mode operation involves timely thrust generation for the fine tuning of the positioning of the microsatellites. The operational timing in this mode of operation ranges from milliseconds to a few seconds at maximum. The operating time is decided based on the adjustment requirement for the positioning of the microsatellites. Vaporizing liquid microthrusters use green propellant to produce thrust. Tests are conducted under vacuum condition to simulate the actual space conditions and corresponding results are plotted. Results has shown a maximum thrust value of 290 μN at 1 sec of valve operating time, 335 μN at 2 seconds, 413 μN at 3 seconds, 524 μN at 4 seconds and 590 μN at 5 seconds of valve operating time for 200°C of a constant VLM temperature respectively. The effect of the dibble volume has also been discussed for the vaporization liquid microthruster using di-ionized water as liquid propellant.

Abstract

Radiant cooling system is a promising technology in saving building energy consumption as well as achieving better thermal comfort. However, in design and simulation of radiant systems, there is a lack of information on one basic parameter: the radiant and convective split of internal heat gain. This study established the dynamic heat transfer model of rooms with radiant cooling systems and internal heat gain components like equipment, lighting and occupant. Through the parametric simulation results, we found the mean radiant temperature of rooms with radiant system could be decreased by 1.0 ⁰C. The radiant splits of internal heat gain are increased: from 0.50 to 0.56 for equipment, from 0.50 to 0.54 for lighting, while from 0.40 to 0.48 for occupant.

Abstract

Biomass CO2 gasification has attracted much attention as part of the CO2 utilization and mitigation. In this study, biomass CO2 gasification is investigated based on an equilibrium model. Parameter sensitive analysis is conducted to investigate the influence of CO2/C ratio and gasification temperature on the gasification process. The results show that the syngas production can be enhanced by increasing the CO2/C ratio of the biomass CO2 gasification. Higher gasification efficiencies are also obtained under higher gasification temperatures.

Abstract

Thermally driven pervaporation process exhibits great promise in desalination application due to its characteristics of combining low-grade heat with high selective membranes to attain efficient separation. The membrane with high and stable water permeation is of key importance in efficient utilization of thermal energy. In this work, high performance laminated graphene oxide (GO) membranes were prepared via pressure assisted filtration for desalination and waste water treatment by pervaporation. The interlayer spacing that affects the permeation and selectivity of GO membrane were tuned by inserting and crosslinking PVA in the GO lamination layers. The cross-linked GOPVA membranes displayed an outstanding and stable water flux of 98.1 kg/m2 ·h, high rejection over 99.9% and high thermal efficiency of 98% in desalinating 10 wt% NaCl solution at 85 °C. Moreover, the cross-linked membrane also exhibited intriguing separation performance in the treatment of organic-contaminated wastewater.

Abstract

Using renewable energy sources is an important pathway to meet the global energy demand, and the upgraded biogas has been prioritized. High pressure water scrubbing (HPWS) has been widely used for biogas upgrading, while the effect of H2S has not been studied well. The work aimed to study how H2S affects HPWS and to investigate whether and when an independent predesulfurization process is required for H2S removal. In this work, the H2S content in the raw biogas and the requirement on the upgraded biogas were surveyed, and the performance of HPWS was evaluated with different amounts of H2S in the raw biogas. The simulation shows that when H2S in the raw biogas is more than 1000 ppm, HPWS without any adjustment cannot meet the requirement of H2S removal; the removal of CO2 and H2S can be achieved by enhancing the desorption, leading to a slight increase of specific total annual cost, while the option of using hot air combined with a heat exchanger is worse than that of adding more air when the H2S in the raw biogas is more than 1600 ppm.

Abstract

In this work, aqueous pentaethylenehexamine (PEHA) was studied as a solvent for CO2 removal to produce purified bio-syngas from biomass gasification, but also as a first step towards negative carbon emissions applying carbon capture and storage (CCS) technologies. Capture of CO2 was tested both with synthetic gas (labscale) and real syngases from the pilot-scale gasifier fed with a wide range of forest-based biomasses. The results showed that the effects of the components other than CO2 and the impurities from the real syngas on the performance of PEHA for CO2 removal are negligible. Combined with previous research results from labtesting with pure CO2 absorption, the aqueous PEHA was shown to be a promising solvent for CO2 removal from syngas. PEHA was also tested as a biomass pre-treatment agent to improve gasification behavior, however, no significant improvement could be identified during the tests performed in this study.