Plant-based vegetation systems are economically feasible and energy-efficient applications to reduce particle matters and volatile organic compounds in indoor environments. The impact of these systems depends on their location and operating conditions. This study focuses on the impact of a real plant-based green wall system, which consists of 128 plants, on a real Lshaped office environment with a total area of 162 m2. The steady-state numerical model is constituted for the whole office area and the trends of air velocity and the air exchange per hour are investigated in the office. The results are compared to the same office environment without green wall scenario, and it is seen that the air exchange per hour is improved by more than 40% for the whole office environment at 1 meter level above the office ground. The outputs of the steady-state model are also found useful for further simulation cases including a transient investigation.
Indoor greenery is an energy-efficient and sustainable solution for living spaces thanks to its positive impacts on indoor air and environmental quality. This study presents experimental research to see the impact of a living green wall based on vegetation systems on the removal of total volatile organic compounds (TVOCs). The living space is a real office environment with a number of 15 people while the outdoor environment is a tropical climate. The study collects continuous and long-term TVOC data using Demand Based Biological Air Purification System (DBBAPS) supported by cloud-based data storage. Sensors are located in various parts of the office and the results show that the present green wall can remove TVOCs up to 95% over a five-week period.
In this work, a modified model considering partial penetration and finite conductivity of hydraulic fractures is introduced to estimate the carbon sequestration capacity of depleted shale reservoir with multiple fractured horizontal well. Firstly, the conservation equations, initial conditions as well as boundary conditions for matrix, natural fractures and hydraulic fractures are deduced with the consideration of partial penetration, finite conductivity, CO2 diffusion, adsorption and seepage. Then, by means of Laplace transform, Pedrosa transform as well as Fourier transform, the pressure response in real domain is acquired. Finally, based on the pressure response of injection well, the influence of penetration degree combined with hydraulic fracture conductivity and hydraulic fracture half length on carbon storage capacity are analyzed, which were always ignored in the conventional methodologies. The results indicate that the penetration degree has significant impact on the early and mid-stage of carbon storage. With the increase of hydraulic fracture half length and conductivity, the influence of penetration degree decreases gradually. Compared with conventional methodologies, the modified model can provide more precise predictions for carbon storage capacity of shale reservoirs.
In order to meet global climate goals and to reduce CO2 emissions, Germany is gradually decarbonizing not only the energy industry but also other sectors such as the chemical and steel industries. To this end, Germany will, e.g., completely phase out coal-fired power generation by 2038. This will inevitably lead to an energy and structural transformation that must be ecologically and economically sustainable. Making this change sustainable necessitates an interdisciplinary approach and understanding for the problems and issues to be solved. Against the background of the coal phase-out in the lignite mining region of the Rhenish region, the Doctoral School Closed Carbon Cycle Economy (DS CCCE) of the Ruhr-Universität Bochum focuses on research on topics related to the necessary energy and structural change and thus trains experts at graduate level. The involved disciplines are Applied Energy, Humanities, Natural Science and Social Science. The PhD projects are largely disciplinary in order to train specialists in the respective fields. At the same time, the DS CCCE offers interdisciplinary networking formats, in order to promote the necessary interdisciplinary understanding and to develop a common language in between disciplines. The DS CCCE is presented in this paper and the PhD projects funded by the DS CCCE are briefly outlined.
Catalytic hydrotreatment of macroalgal bio-oil using supported palladium and copper chromite catalysts was systematically studied. The aqueous fraction of brown algal bio-oil (BABO) produced by fast pyrolysis was used as feedstock and was hydrotreated in temperature range of 250-400 °C at LHSV 0.48 h-1 and 10 MPa H2 using a trickle bed reactor. The yields of the organic phase products over the 5wt% Pd/Al2O3 and CuCr2O4 catalysts were maximal 42.33 wt% and 39.73 wt% at 350 °C, respectively. When the reaction temperature increased, the H/C ratio of the organic products increased with decreasing the O/C ratio. The carbon double bonds along with proof of unsaturated compounds were saturated by catalytic hydrotreatment. The supported palladium catalysts produced more furans and esters with increasing carboxylic acids in aqueous phases, whereas the copper chromite increased the heterocyclics and phenolics.
Multi-stream heat exchanger is one of the most important components in CO2 purification process, which is characterized as high efficiency, low consumption and high energy density. This work aims to develop a CFD model for a multi-stream heat exchanger, based on which the impact of the impurities on heat transfer characteristics is studied. Three streams are considered, including two streams flowing in two concentric pipes and one stream flowing perpendicularly to the pipes. Based on the model, this work calculates the pressure drop and the average heat transfer coefficient which is calculated from the average heat transfer coefficient of two interfaces formed from these three fluids. It is found that the average heat transfer coefficient and friction pressure drop have an obvious downward trend with the increase of the volume fraction of impurity gas; under the same volume fraction of impurity gas, both of them increase with the increase of refrigerant velocity.
In order to limit the negative effects of large circumferential thermal gradient in parabolic trough collectors (PTCs), enhancing the flow and heat exchange of the working fluid by embedding spiral slices in the absorber tube is a promising method. The absorber tube with the secondary reflector (SRAT) was proposed which solar flux is significantly uniformly distributed. The thermodynamic performance of the embed spiral slices absorber tube (ESAT) is analyzed and compared with that of the SRAT by building a thermal-structure coupled model. It can be found that compared to traditional absorber tubes, the circumferential temperature difference of ESAT with different pitches is reduced by 13%-53%, and the maximum thermal stress displacement is reduced by 32%-50%, which is much less than that of SRAT. However, under the simulated conditions, ESAT eliminates the high-temperature boundary zone of the working fluid and the useful energy of the working fluid increases by about 7% compared to SRAT, but the outlet pressure loss increases. This research can improve the energy efficiency, economy, and reliability of parabolic trough collectors.
In the context of climate change and the increasing demand for sustainable solutions in the energy sector, it is of particular interest to consider environmental impacts of alternative energy systems or transformation pathways. In this study, this is achieved by combining an energy system model with a life cycle assessment, enabling the consideration and optimization of factors such as global warming potential, metal depletion potential and land occupation potential in addition to system costs. The individual optimization of these four objectives is extended by a multi-objective optimization using the augmented ε-constraint method. This is applied to the Rhenish Mining Area, a lignite region in Germany that currently undergoes significant structural change, with an electricity system expansion planning for 2040. Depending on the objective, gas-fired power plants or onshore wind energy are strongly preferred. For every objective, the electricity generation in the considered region decreases, especially when environ-mental impacts are minimized, which transforms the Rhenish Mining Area from a current electricity export region to an import region.
The effects of anaerobic co-digestion at household level with waste activated sludge and food waste as co-substrates were studied in a GD-BMP test with mix ratio volatile solids basis of 20:80, 30:70, 50:50, 70:30 and 80:20 (WAS/OW) respectively. The results obtained were used to assess the feasibility of energy generation and the volume of each waste that can be treated. The highest specific methane yield calculated was of 431.31mLCH4/gVSadded from the 30:70 mix ratio sample with an RSD of 4.68%. It was hypothesized that the benefits of adding food waste will shift the C/N ratio leading to a potential coverage to reduce the energy demand from households by 50%. In addition, the benefits from a house scale SBR with microbubble aeration followed by SCSTR anaerobic co-digestor. Using the 30:70 mix ratio analyzed, a calculation to obtain the electrical energy that can be recovered from a single household resulted in a 30% reduction of energy coming from the grid. This paper reflects that biogas can be used as a replacement of fossil fuels, reducing the carbon dioxide footprint and the strong link to the WEF Nexus cycle, and discusses the implications.
An optical-thermal coupled model was developed to study the performance of a typical molten-salt solar power tower, which was proven to be reliable by comparing with testing data. It is found that the mean absolute deviations between simulation and testing data are about 0.8% for the receiver efficiency under full-power condition. The model reveals that the detailed distributions of the solar flux and temperature in the receiver are extremely non-uniform, which resulted in high thermal stress at the tube crown. Moreover, failure analysis of the receiver indicates that the high strain introduced by high flux can result in fatigue failure, but it can be avoided by reasonable aiming strategy. The validated model and results from this work can offer helps for appropriate performance predictions in solar power tower.