Abstract

To promote the development of solar photovoltaics, dozens of countries implemented Feed-in-Tariff (FiT) Scheme in succession. However, accompanied with the increasing installed solar capacity, the issue of unequal distribution of the subsidies also arises due to its implementation. In China, a large number of solar PV stations concentrate in the more developed areas, which means that these areas could get more subsidies from the central government, whilst the burden is borne by all the electricity consumers. In 2014, China launched the Photovoltaic Poverty Alleviation Project (PPAP) to construct solar PV stations for the poor, indicating that the poor can also enjoy the subsidies derived from FiT Scheme. This paper is intended to illustrate the distributional justice of FiT subsidies in mainland China, so as to fulfill the gap of empirical studies in this field. What’s more, whether the implementation of the PPAP could enhance energy justice and become a reference for other countries is also discussed. The results suggest that the distribution of per capita subsidy was increasingly even during the past five years. However, the per area subsidy is significantly correlated with the local economic development, which is inseparable from the provincial preferential policies. As for the PPAP, it can improve the distributional justice to some extent but the impact is slender at current stage.

Abstract

Geothermal heating technology is critical in urban sustainable development and climate change mitigation. This research paper conducts a numerical simulation and multi-objective optimisation for geothermal heating systems based on factors such as ground demand, profitability regulation modes, and region areas. It’s indicated that well spacing and production rate are the two main factors affecting production performance as well as emission reduction efficiency of geothermal heating systems. The heating mode also plays a vital role in the utilization of geothermal reservoirs. There is a delay in the formation time of thermal breakthroughs of the regulated geothermal heating system. The radius of the cold front shrinks, while production performance and emission reduction efficiency also decrease. Comparing the regulated geothermal heating system to the unregulated geothermal heating system, the construction investment of geothermal wells and the annual water consumption both decrease by up to 30% and 60%, respectively. Additionally, electricity costs increase by 5% to 25%. The regulated geothermal heating system with well spacing of 300m and production rate of 100m3/h generates the highest efficiencies in terms of heat production, emission reduction, and economic performance, all of which are most suitable for this project in Qingfeng. The simulation method and optimisation model of this research paper can be extended to other regions.

Abstract

With huge reserves, marine natural gas hydrate is one of the most potential unconventional alternative energy sources after shale gas, coalbed methane and tight gas. The research and pilot engineering of natural gas hydrate exploitation technology mainly adopts the depressurization method at home and abroad, all of which refer to the exploitation technology of conventional oil and gas. However, if the depressurization method is used to exploit the weak cementing and unstable non-diagenetic marine natural gas hydrate, the hydrate will be decomposed disorderly and uncontrollably, and 6 great risks will be faced. Therefore, the project team led by Academician Zhou of the Chinese Academy of Engineering divided the hydrate into the kind of diagenetic and non-diagenetic, proposed the technological strategy of 6 “utilize”, firstly created the technological principle of solid fluidization exploitation of non-diagenetic natural gas hydrate and the technological process of hydrate mining, crushing, ejection and fluidization of seawater, separation and backfill of sand, slurry lift and deep separation and re-backfill in the platform, and achieved the safe and green exploitation which let nature take its course, turned the harm into a benefit, and turned the uncontrollable into controllable. Based on this principle, Southwest Petroleum University invented the experimental simulation method and technology, cooperating with China National Offshore Oil Corporation and Sichuan Honghua Petroleum Equipment Co. Ltd. The overall process simulation of solid fluidization exploitation with water depth of 1500 m and pipeline length of 4500 m is achieved. The world’s first large physical experimental simulation system of solid fluidization exploitation of marine natural gas hydrate is researched and developed, which has full independent intellectual property rights and includes 3 modules and 12 subsystems of sample preparation of hydrate, crushing and slurry modulation, high-efficient pipeline transportation and separation of slurry, image capture in real-time, data collection and automation of security control and so on. Moreover, the experiment of solid fluidization exploitation is carried out systematically for the first time, which provided an important basis for the formulation of the test scheme, the optimization design of the process and the research and development of downhole tools, supported the world’s first successful test exploitation of solid fluidization method, and proved the scientific feasibility of the principle and the technology of solid fluidization exploitation. The experimental simulation technology and system, as well as the first testing results, were reported in the Journal Science. The successful research and development and the further upgrading of the system are expected to promote the technology of solid fluidization exploitation of marine nondiagenetic natural gas hydrate to become a disruptive technology leading the world’s frontiers, and are expected to accelerate the commercial development of natural gas hydrate in China and even the whole world.

Abstract

In this paper, the quantitative investigation of the free-surface effect on tidal turbine performance by using a multi-phase flow formulation is presented. The computational formulation is briefly introduced. The free-surface effect is rigorously studied by the simulations performed for a single turbine and two back-to-back turbines using different inflow conditions and immersion depths. The thrust and power coefficients of the tidal turbines in free-surface flows are quantified. It is found that the presence of free-surface has a significantly negative effect on tidal turbine performance by decreasing the thrust and power coefficients in idealized inflow conditions, such as uniform inflow and Airy wave inflow conditions. The comparison with pure hydrodynamics simulation results shows that pure hydrodynamics simulations are unable to provide accurate predictions and the free-surface effect must be taken into account in the modeling and simulations of tidal turbines, especially for shallow immersion depth.

Abstract

Storage is going to be a crucial part of the electrical grid of the future, with the penetration of renewables. It is necessary to have a long-term storage method to take care of seasonal variations of Solar Energy. The system must be environmentally friendly and must not have hazardous materials. A thermoelectric storage system is proposed in this work to take care of these challenges. Cooling of a Phase Change Material can be done via Peltier modules and the energy to supply latent heat of fusion can be considered as the charging process. By operating the Peltier modules as a thermoelectric generator (i.e. Seeback Effect) the discharging of the cell can be done. The system must be suitably insulated to prevent heat loss. Coefficient of performance and efficiencies of the thermoelectric modules may be a deterrent but by modulating power judiciously via Power Electronics the technology can be scaled up.

Abstract

Although CO2 foam flooding is a proven technology to improve oil recovery; it has been criticized for lack of long term stability in saline environment and in the presence of crude oil. To generate a more stable foam front in the presence of crude oil and to overcome the capillary forces destabilizing the foam lamella, polyelectrolyte complex nanoparticles (PECNP) conjugated with surfactant oligomers were introduced to the lamella generated by high salinity aqueous phase to improve the EOR performance and produced water compatibility of supercritical CO2 (scCO2) foams. The formation of vesicular structures containing electrostatically hinged complexes of PECNP and surfactant was verified via transmission electron microscopy (TEM) while the structural changes associated with molecular complexation were identified using Raman spectroscopy. Accordingly, optimized ratios of PECNP: surfactant were employed to generate the most stable scCO2 foam in high salinity produced water and to improve the recovery of the foam flooding process. Conducting core-flooding experiments in wide range of salinities indicated that the highest incremental oil recovery and the lowest residual oil saturation were achieved by prioritizing PECNP: surfactant scCO2 foam flood.

Abstract

The virtual water and CO2 along with the energy trade has reshaped the water resources utilization and CO2 emissions, making the energy, water and carbon emission management more complicated. We employed the multi-regional input-output analysis to examine the virtual water-CO2 trade-offs driven by energy demand among Chinese regions in 2010. We observe different spatial distribution for water and CO2 footprints, which have high intensity in south and north China respectively, though most coastal provinces have high water and CO2 footprints than inland provinces. The virtual water and CO2 are transferring from central and west provinces to the coast, consistent with the energy transmission network, but at the risk of aggravating the water stress and CO2 emissions in especially Yellow River region (including Shanxi, Shaanxi, Henan, Inner Mongolia). By paying attention to different energy sectors, the major exporters are different, indicating the higher water pressure in Yangtze River region (including Anhui, Hunan, Hubei, Jiangxi), higher CO2 emission increase in Yellow River region induced by electricity sector, while the northeast region in both aspects induced by oil refining sector. To mitigate water consumption and CO2 emission both directly and indirectly, the sector interactions between energy and others highlight the upstream water use by agriculture, and the electricity sector’s water use and CO2 emissions. The environmental impacts driven by the same energy demand in each province are examined. Finally, policy implications are discussed based on the findings.

Abstract

—In order to solve the problems of deficient CO2 adsorption sites on Zn/Co zeolitic imidazolate frameworks(ZIFs), Zn/Co ZIFs were thermally treated to promote physical adsorption sites on Zn-N and Co-N bonds and then impregnated with polyethyleneimine (PEI) to promote -NH- and -NH2- chemical adsorption sites. The CO2 adsorption capacity detected on Micromeritics ASAP 2020C increased by 53% to 1.07mmol/g at 298K and 1bar, when Zn/Co ZIF was treated at optimal temperature of 450 ºC to obtain the maximum Me-N2 unsaturated adsorption sites. This was because of a partial cleavage of coordination bonds between Zn-N, Co-N, C=N and C-N along with dissociation of rationally free methyl groups in the framework ligands, which was supported on density functional theory (DFT) calculation. The Zn/Co ZIF treated at 450 ºC and then impregnated with 40wt% PEI exhibited the highest CO2 adsorption capacity of 1.82 mmol/g under the condition of at 298K and 1bar, which was 2.6 times higher than that of raw Zn/Co ZIF. In addition, this adsorbent is proved to be regenerable and stable during 9 cycle CO2 adsorptiondesorption tests, therefore, PEI- thermally treated Zn/Co ZIF exhibits a very promising application in CO2 capture from flue gas and natural gas.

Abstract

—Membrane technology is an attractive approach for CO2 capture from flue gas derived from coal-power plants, due to its inherent advantages such as high energy-efficiency, small footprint and potentially low cost. The state-of-theart membranes are based on polar poly(ethylene oxide) (PEO), which exhibit high CO2 permeability and high CO2/N2 selectivity. In this work, these PEO containing materials were doped with zeolitic imidazolate framework (ZIF-8) nanoparticles to improve CO2 permeability. Specifically, ZIF-8 was incorporated into polymers prepared from poly(ethylene glycol) diacrylate (PEGDA). These ZIF-8 nanoparticles had high porosities and average pore aperture of 0.34 nm that was between the molecule size of CO2 (0.33 nm) and N2 (0.364 nm), indicating their potential of achieving high CO2 permeability and CO2/N2 selectivity. The in situ synthesis of ZIF-8 provided uniform nanoparticle size of about 100 nm, enabling a good dispersion in polymers at loadings as high as 50 wt%. Increasing the ZIF-8 loading dramatically increased CO2 permeability. For example, adding 10 wt% ZIF-8 increased the CO2 permeability from 130.8 Barrers in a polymer prepared from PEGDA to 318.3 Barrers without changing the CO2/N2 selectivity. At a loading of 50 wt%, the nanocomposite exhibited a CO2 permeability of 1334.5 Barrers and CO2/N2 selectivity of 33.1 at 35 oC, which was one of the best separation properties reported in the literature.

Abstract

The increasing penetration of renewable energy sources (RES), battery energy storage systems (BESS), and other loads native to DC, raises the question if a DC backbone topology may be more suitable compared to the commonly used AC. A number of studies that focused on this question, demonstrate a wide range of results that depending on the application and external conditions simulated. In this work, simulated DC and AC topologies are tested in an office building located in Belgium using a modelling framework developed in Modelica. The building is assumed to have a large penetration of building-integrated photovoltaics (BIPV) and battery energy storage systems (BESS) and a wide range of key performance indicators (KPI) are used to quantify the comparison. The DC topologies demonstrate increased performance when the BIPV system produces large amounts of power. The performance gains may be further enhanced by sizing optimally the less efficiency system components.