Abstract

As the climate change casts its shadow on our future, while temperatures are rising in a noticeable pace, thermal comfort in buildings are subjected to that effect in terms of future levels. This paper aims at evaluating thermal comfort levels in a pilot Passivhaus building, while integrating building simulation software, implementing new tools alongside the Passivhaus Planning Package, to produce multiple parameters as a detailed output for assessing the building indoor thermal status of users, during current and different future timelines and CO2 emission scenarios. Findings have predicted a set of PPD values for different timeline-CO2 emissions combinations, including recording a jump in PPD from 35% at the historical recent timeline of 2003-2017, to 94% at the timeline of 2080s of high CO2 emission scenario, during summer peaks at each timeline. Results have also identified a set of descriptive outputs regarding psychrometry, thermal sensation, and effective temperatures.

Abstract

A large potential for energy savings can be found in building envelopes of the existing Swedish dwelling stock. This study analyzes the final energy savings and cost implications of energy efficiency measures for an existing multi-apartment building in Sweden. Energy efficiency improvements consisting of high-performance windows as well as doors, and additional insulation to attic floor and exterior walls were modelled to the building’s thermal envelope. Dynamic energy balance simulations were performed to determine the final energy savings of the improvements. The cost-effectiveness of the improvements were then analyzed considering the net present value of the energy cost savings and the investment costs of the improvement measures. The results showed that additional insulation to the attic floor is the only cost-effective measure for the building under the existing operating conditions. The other improvement measures give high final energy savings but are not cost effective due to their high investment costs.

Abstract

Reducing CO2 emissions from fossil fuel combustion is emergent, especially for China. As one of the most concerned techniques in CO2 capture process, the rather high energy consumption and cost in chemical absorption process is the leading obstacle interfering the development and deployment of CCS. In this paper, the energy consumptions during chemical absorption process in the literatures were collected, where the data distributions indicate that developing advanced absorbents may be a more efficient way in energy saving compared with improving separation process. Thus, a further verification is carried out based on idea separation process. Results show that improving separation process has limited possibility in reducing energy consumption compared with developing advanced absorbents, and the potential in improving separation efficiency for the former is one third as much as the latter.

Abstract

Model predictive control is an important controlmethod to reduce building heating and cooling energy consumptions. However, the mechanism by which the energy savings are achieved is not well understood. This paper investigates such mechanism using building energy simulation. The simulation results show that the better constrained indoor temperature leads to lower heating and cooling loads, which results in reduced energy consumptions. Comparing with a conventional 2 °C dead-band control, a model predictive control, which restricts the indoor temperature within 0.2 °C range of the set point, obtains an 8.5% and a 13.6% annual energy savings in heating and cooling respectively.

Abstract

The application of heterogeneous catalysis in biomass thermochemical conversion is considered as one of the most promising methods to improve biofuel production by minimizing its undesirable properties and producing renewable fuels and high-value chemicals. However, the catalyst used in practical industrial reforming application undergoes deactivation inevitably, which is a problem of great and continuing concern. In this study, molecular dynamics simulation with reactive force field is performed to gain atomic insights into the thermal stability of Ni nanocrystal and the effect of coke deposition on catalyst deactivation.

Abstract

Applying thermal barrier between batteries is one of the most effective method to mitigate thermal runaway (TR) of battery. This work investigated TR of a single battery considering the contact resistance between the battery internal cell and external hard shell, and TR mitigation using equivalent thermal barrier between batteries. The results indicate the contact resistance between the internal cell and external shell is around 0.0207 m2·K·W-1. For preventing TR propagation, resistance of thermal barrier should be higher than 0.01242 m2·K·W-1.

Abstract

This study reports the component of syngas and tar produced from oxidative pyrolysis of polypropylene with electron-injected air using a laboratory-scale reactor. This experiment was conducted using a cylindrical fixed bed reactor. The feedstock tested in this study was polypropylene. During experiments, the feedstock was heated by an electric heater to 500, 600, and 700°C with or without electron injection into the air. Under all experimental conditions, oxidative pyrolysis occurred immediately after the start of the test. The analysis results of syngas and tar samples show no significant effects of electron injection at 500°C while significant effects were observed at 600°C and 700°C. Electron injection gave a clear impact on syngas and tar production during the oxidative pyrolysis of polypropylene.

Abstract

With the development of renewable energy generating, the conventional power plants put forward higher requirements for flexible load regulation. While the heat flux distributions on water walls could change at varying load conditions. In the present study, the numerical simulation model of 600 MW tangentially coal-fired boiler was established to calculate the heat flux on water walls. The results revealed that the center of the heat flux area has a small offset with the geometric center of the furnace. The boiler load, primary air rate, air staging, burner and SOFA air swing were adopted as influencing factors to heat flux distribution, the heat flux deviation coefficient is selected as the index of evaluation. Orthogonal analysis indicated that the order of the influence of various factors was: boiler load >
burner swing > air staging > SOFA air swing > primary air rate. The research was expected to provide the suggestions for the boiler operation and retrofit.

Abstract

The Green-Blue infrastructures in sponge residential communities have important ecological benefits but are still lack of systematic evaluation methods. This study proposes an emergy-based classification and evaluation method for four types of Green-Blue infrastructures, including forest type, wetland type, grassland type, and special type. 20 typical sponge residential communities in 7 cities of China are surveyed. The results show that wetland type infrastructures (including biological retention pond and rainwater garden) can provide the highest ecological benefit per unit area. There is obvious spatial heterogeneity of GBIs’ ecological benefits. The results show that, compared with north cities, the construction of GBIs can provide higher ecological effects in south cities. The donor-side method can provide new ideas and references for the assessment of sponge residential communities.

Abstract

The asphalt pavement surfaces tend to absorb a large amount of heat through solar radiation and increase the urban air temperature. The thermal energy can be collected by water circulated through buried copper pipes and cool down the pavement surface, which decreases the air temperature and building cooling energy demand. This work aims to develop a method for determining the optimum areas to locate pavement solar collector (PSC) systems and simulate the reduction of ambient air and surface temperature by using a coupled computational modelling approach. A prototype of the PSC was developed, and lab-scale experiments were carried out for validation. Based on the simulated conditions, in the unshaded area, the near-surface temperature of the asphalt slab was reduced by up to 10℃, and the outlet water temperature increased by about 5℃. At the pedestrian height level, the reduction of air temperature was up to 4.6℃. This study further expands the investigation of the system by varying water velocity, inlet water temperature and air temperature. The proposed method could be used to optimise the positioning of the PSC to reduce urban surface and air temperature.