Considering the vital role of electricity in the energy consumption and electricity transportation being a bottleneck of high proportion renewable energy development in China, this paper assessed the current and future flow from a provincial perspective. According to the electricity flow in 2015, we found that most provinces mainly relied on local electricity power supply, while there was massive curtailment of the utilization of wind and solar power in some provinces due to the lack of electricity transportation capacity. From the perspective of provincial China-TIMES model in reference scenario, the southern and eastern provinces with large population or GDP will need to import electricity from northern and western provinces with high proportion integration of renewable energy. In the case study of Inner Mongolia and Henan in low carbon scenarios, the demand for electricity output capacity of Inner Mongolia is increasing and further optimization of the national electricity transportation capacity is needed as the increase in electricity flow.
CO2 conversion into the useful compound is gaining increasing interest in recent years but a huge amount of energy is required to activate CO2. Recently, plasma have been appearing as an attractive alternative for CO2 activation. Among plasma technologies, a low current plasma can be a competitive and valuable alternative because it is available at atmospheric pressure and room temperature and is easy to operate. In this study, the high efficiency of CO2 activation was demonstrated using a low current arc plasma. In addition, the effect of addition of γ-Al2O3 and CaO on the CO2 conversion and energy efficiency was investigated. The CO2 conversion and energy efficiency were 10.9% and 19% without catalyst. By adding CaO, they increased to 23.3% and 46%, respectively.
The paper outlines our ongoing efforts on building a framework for a flexible refined products supply chain. Current refined products supply chain faces the risks of supply and demand fluctuation, refineries and transport facilities (i.e. pipelines) disruption, and depots accidents. These risks will lead to the unmet demand of the sales market and affect social and economic developments. The framework integrates a basic mixed-integer linear programming model for current refined products supply chain simulation, a reliability assessment method, and an expanded model considering facilities expansion and multi-energy sources supplement. We introduce the concept and importance of refined products supply chain flexibility study, the conceptual framework and its integrated components. Finally, we summarize the current research challenges and give a conclusion.
As a large energy prosumer in the urban energy systems, on the one hand, datacenters consume a large amount of electricity to ensure the IT facilities and ancillary power supply and cooling systems work properly; on the other hand, datacenters produce a large amount of waste heat due to the high heat dissipation rates of the IT facilities. To date, a systematic review of datacenters from the perspective of energy prosumers, which considers both integration of the upstream green energy supply and downstream waste heat reuse, is still lacking. This study fills in this gap and provides such a review. By providing a full picture of datacenters in the urban energy systems, this study aims to search new opportunities for improving datacenter overall energy efficiency and reducing carbon emissions
D-mannitol (DM) is a phase change material (PCM) for medium temperature thermal energy storage. In this paper the preparation of microencapsulated d-mannitol by a sol-gel process is reported. The microencapsulation of d-mannitol was confirmed by characterization using a scanning electronic microscope (SEM) and Fourier transform infrared spectroscopy (FT-IR) analysis. The thermal properties of the microencapsules were measured by a differential scanning calorimeter (DSC) instrument. The thermal stability of the synthesized DM microencapsules was investigated by means of thermogravimetric analyzer (TGA). The results show that the microencapsulated d-mannitol have a high phase change latent heat of 220.3 J/g and improved thermal stability.
CaO-based CO2 sorbents play a significant role in sorption enhanced methane steam reforming process for hydrogen production and CO2 emission reduction. In this work, pretreatment of CaO/Ca3Al2O6 sorbents in steam atmosphere at different temperatures was investigated for its influence on CO2 sorption capacity and cyclic stability. The sorbents were synthesized to contain a CaO to Al2O3 mass ratios of 9:1, and then subjected to cycling tests with repeated carbonation and calcination process. Results showed that the sorbents pretreated by steam at 250 °C obtained a minimum CaO grain size of 37.9 nm and a maximum surface area of 17.4 m2·g-1 . This resulted in an increase in CO2 sorption capacity, up to 8.53 mmol CO2·g-1 sorbent. After 50 cycles, the CO2 sorption capacity decreased, but still remained 10% above those for the original (no pretreatment) sample. The mechanism about the improved CO2 sorption performance of the pretreated sorbents was also postulated.
This paper proposes a self-adaptive principle of current differential protection for AC transmission line in AC-DC hybrid power grid. By analyzing the post-fault transient characteristics of inverter-side AC current with commutation failure occurred, the principle is proposed by using the promoted instantaneous energy ratio of currents from line terminals. The principle eliminates the influence of commutation failure by constructing instantaneous energy of terminal currents using trigonometric method. Besides, based on the feature that zero-sequence network of inverter AC system is isolated from DC system, the principle promotes the sensibility in high resistance-ground fault situations by constructing self-adaptive criterion with promoted instantaneous energy of zero-sequence AC current. PSCAD/EMTDC simulations are provided to verify the reliability of proposed principle and the results show that the novel principle is unaffected from commutation failure and is suitable for AC transmission line protection in AC-DC hybrid grid.
The fuel utilized in spark-ignition aviation piston engine is undergoing a transformation from gasoline to heavy fuels (kerosene and diesel) for security reasons. To overcome the problem that kerosene is difficult to be ignited by spark but easy to cause engine knocking, in this paper, short-chain alcohols were used to blend with kerosene to improve fuel physical and chemical properties. Specifically, three kind of alcohols namely ethanol, n-propanol and n-butanol were blended with kerosene by volume fraction of 30%, 50%, 70%, respectively. Results indicated that alcohol/kerosene blends could reach higher brake thermal efficiency (BTE) (alcohol ratio ≥ 50%) compared to gasoline. The low energy density of alcohols led to the increase in brake special fuel consumption (BSFC). Excessive ratio of ethanol and n-propanol (70%) led to higher maximum pressure rising rate (MPRR). For the main gaseous emissions aspects, CO and NOx emissions of blend fuels decreased. However, the unburned hydrocarbons (UHC) and soot emissions were relatively higher. Notably, nbutanol/kerosene exhibited better emission characteristics, which have the lowest CO, UHC and soot emissions, compared with other blends. With the increase of alcohol proportion in blends, the downward trends of CO, UHC as well as soot emissions were more pronounced, while NOx emissions increased first and then decreased for ethanol/kerosene and n-propanol/ kerosene. N-butanol in 70% volume fraction led to extremely high NOx emissions.
Barriers exist against the emergence of any new technology. For algal biorefineries, these barriers manifest in competition for resources, slow capacity growth, and the diminishing urgency of environmental issues, which worsen as the algae-based biofuel is diffused. Given the dynamic nature of the problem, a system dynamics model is developed with the objective of identifying areas for intervention that can promote diffusion with minimal negative feedback. The model contains four dynamic hypotheses, representing areas that hamper the diffusion of algae-based biofuel. These hypotheses are the economic, social, and environmental sectors that are affected by the operations of algal biorefineries. A sensitivity analysis of parameters revealed the strategies which ensured the successful propagation of the technology relied on good anticipation of market growth and the maximized energy yield growth from investments. This was compared to traditional solutions such as incentives for adoption and penalties against emissions, and linear models. The results indicated that the linear models failed to capture the dynamicism of the problem. The contribution of this study is a new perspective on managing the growth of algal biorefineries.
Microalgae-based biomass are an emerging technology and an alternative source to biofuels. It has a high lipid content and is composed of other biocompounds which is essential for high-valued products. The biorefinery concept is a means to efficiently convert microalgae into biofuels and other high-value products. However, biorefineries require large capital investments that must be wisely planned and decided across the lives of the investments. This study proposes a multi-period multi-objective mixed integer non-linear programming (MINLP) model that simultaneously maximizes net present value (NPV) and minimizes greenhouse gas (GHG) emissions through optimal investment scheduling and operational decisions of an algal biorefinery. The model capabilities are demonstrated through an illustrative case study and scenario analysis.