• Energy Research
• Renewable Energy close
• Chinese Academy of Sciences close

Abstract In the present study, Ru modified hierarchical zeolites xRu-MZSM were developed for cellulose fast pyrolysis. Comprehensive catalyst characterizations including XRD, XPS, N2 adsorption-desorption, Py-IR and so on, were performed to unveil the essential structural properties. The chemical modification and Ru decoration remarkably regulated the distribution of Bronsted/Lewis acid sites. The presence of RuOx species would supply abundant strong Lewis acid sites for participating catalytic cracking, dehydration, decarbonylation, decarboxylation, cyclization, aromatization, etc., in cooperation with Bronsted acid sites. In-situ generated active Ru0 centers during cellulose pyrolysis might facilitate the proceeding of deoxygenation, hydride transfer, and dehydrogenation. Among the as-prepared catalysts screened, 2Ru-MZSM was much more efficient in aromatics production from cellulose fast pyrolysis compared to parent ZSM, wherein the total aromatics yield achieved 16.8% at temperature of 650 °C and heating rate of 10 °C/ms with corresponding E value as low as 23.40 kJ/mol. Also, plausible reaction mechanism for xRu-MZSM involved cellulose fast pyrolysis was proposed in detail.

The silicon vertical multi-junction (VMJ) solar cell has low costs and low series resistance, thus it has a good potential in concentration photovoltaics. However, there were few discussions about the thermal and electrical performance of silicon VMJ cell under non-uniform illumination. In this work, the thermal performance of silicon VMJ cell under 1D non-uniform illumination of 500 suns was calculated using finite element method first, and then the electrical performance of the cell was calculated using SPICE software based on the thermal simulation results. It was found that the mean temperature of the cell increased with the degree of non-uniform illumination when the area ratio of the sink to the cell was 500X, and the mean temperature changed few when the area ratio was 2500X. The efficiency of the cell did not decrease with the increase of the degree of non-uniform illumination when the area ratio was 500X, and the efficiency increased with the degree of non-uniform illumination when the area ratio was 2500X. Thus, the silicon VMJ cell had better performance than silicon planar junction cell under 1D non-uniform illumination of 500 suns.

Abstract The hydrothermal geothermal heating depends heavily on the existence of hot water reservoir and the shallow ground source heat pump occupies large area. Here a single well geothermal heating (SWGH) technology is shown, which does not depend on the existence of hot water reservoir. An experimental research on SWGH is carried out and a mathematical model describing the heat transfer through surrounding rock to well tube as well as inside the geothermal well is developed. The mathematical model validated by experimental data is then used to predict the performance of SWGH. It is found that the average extracted thermal output is respectively 448.49 and 413.63 kW in the first and tenth heating seasons. By changing the injection water temperature and velocity, SWGH system can meet the requirement of building heating load varying with the outdoor air temperature and adjust the imbalance of the extracted thermal output among different heating seasons. Understanding these will enable us to better apply SWGH technology.

Abstract Development of Internet of Thing requires the high efficiency indoor energy harvesting solution using photovoltaic cells. This study presents the experimental investigation of the power performance of the solar harvester using crystalline silicon (c-Si) and Cu(In, Ga)Se2 (CIGS) photovoltaic cells. Experimental studies include the optical environment setting, indoor source selection, the light source calibration and power measurements. The measured efficiencies of c-Si and CIGS cells are in the range of 1.5%–7.4% with strong source-dependency. Efficiencies of power conversion module varies in the range of 65%–75%. Furthermore, the efficiencies of solar cells and modules vary with the change of level of illuminance. Correction factors of cell efficiency and module efficiency are derived from experimental data. In general, c-Si and CIGS cells showed acceptable performance under wideband light source. However, their power outputs are limited under the various narrowband indoor light sources. Future development of the indoor-used photovoltaic cells may focus on the narrowband indoor light applications.

Abstract Enhanced Geothermal System (EGS) is an essential approach to entrap heat from deep hot dry rock (HDR), a low-carbon and renewable energy. Understanding the long-term productivity performance of the EGS and its sensitivity to different reservoir parameters can help to achieve efficiently the optimized exploitation of a designated reservoir. The Qiabuqia geothermal area, located in the northeastern margin of the Gonghe basin, Tibetan Plateau, is one of the areas that have the greatest HDR geothermal resources exploration and development potential in China so far. Based on the geological data of the GR1 borehole at the Qiabuqia geothermal area, northeast Tibetan plateau, a 3D thermo-hydraulic coupled numerical model is established in this study with the method of finite element to assess the heat production potential. The mathematical model presented in this study is validated by the analytical solution of a single fracture model. By varying several key reservoir parameters (e.g. thermal conductivity, permeability, porosity, injection mass flow rate, injection fluid temperature, and lateral well spacing), the sensitivity analysis of the long-term production temperature and electric power rate evolution is implemented. The simulation results indicate that in the basal granitic reservoir with a depth of 2900 m–3400 m and a corresponding initial temperature of 160 °C–180 °C, the temperature produced and effective electric power can maintain at 173.4 °C and 2.48 MW for the first 7 years of simulation under the combination of 50 kg/s of injection flow rate, 60 °C of the injection fluid temperature and a 300 m of lateral well spacing. At the end of the 40-year operation period, the outlet temperature decrease to 162.8 °C, as well as a drop of 9.7% in the electric power. Sensitivity analysis with the method of ‘One Factor At a time’ suggests that the permeability is the parameter that affects the production temperature and energy extraction the most compared with the thermal conductivity and porosity. For a specified geothermal field with a known distribution of permeability, thermal conductivity and porosity, the injection mass flow rate has the most significant effect on the electric power output, followed by the injection temperature and the lateral well spacing. The results from the complete factorial experimental design simulation suggest the electric power performance of the reservoir can be increased by a reasonable multi-parameter combination. For a doublet well extraction system, based on the Qiabuqia geothermal area, a combination of 70 kg/s injection flow rate, 60 °C injection temperature, and 500 m lateral well spacing can attain an effective electric power output of 3.47–3.50 MW. Thus, this study compares the different heat mining performance potential under various reservoir parameters and their combinations through the aforementioned sensitivity analysis and can greatly promote the establishment and development of EGS program in the Qiabuqia geothermal area in the future.

Abstract In this paper, biomass and coal has been used as blending feedstock for synthetic natural gas (SNG) production to originally shift H2/CO ratio in syngas during gasification step that benefits downstream methanation process. The recycling ratio of unreacted gas is controlled to avoid huge exergy destruction during methanation, thus providing opportunity for supplementary power generation. The remaining gas is directed to chemical looping combustion (CLC) for power generation, and carbon capture is inherently achieved. Besides capture and storage of photosynthetically-derived CO2 from biomass by means of CLC offers possibilities for negative greenhouse gas emissions. The energy efficiency and exergy efficiency of this proposed process are 53.19% and 50.81%, respectively. Meanwhile approximately 16.86% of energy consumption and 98.74% of carbon emissions have been reduced compared with standalone reference system. In terms with the captured CO2 quality, it meets the requirement of suggested restrictions at biomass share of 40% (wt. %). Within this biomass share, the oxygen-to-carbon ratio (O/C), steam-to-carbon ratio (S/C), and recycling ratio of unreacted gas (Ru) have been found to be optimum at 0.4, 0.5 and 0.7, respectively.