Abstract

The potential for saving on energy related cost with timely and accurate Fault Detection and Diagnosis (FDD) in the air-conditioning system which is as one of the major energy consumer in buildings has been estimated to huge. In recent years, the research on fault diagnosis of air-conditioning systems has mostly focused on single fault or multiple faults. While, there is less research on simultaneous faults because of the complexity of simultaneous faults. This paper proposes a diagnosis method based on deep convolutional neural network, which can effectively diagnose the common two simultaneous faults and three simultaneous faults in variable flow systems. The results show that this method can effectively isolate faults in the case of multiple faults and multiple-simultaneous faults. The diagnostic accuracy is over 98%, and the Hamming loss value is lower 1. 5%.

Abstract

This study considers the prediction of the two-phase frictional pressure drop with water–steam flows through helically coiled steam generator, special emphasis is given to the annular flow present in helical systems. An empirical correlation based on the Lockhart-Martinelli parameter is proposed and fitted using an experimental pressure drop database containing 698 points. A new pressure drop correlation for helically tubes is proposed to increase prediction and knowledge in this class of systems, selecting only annular flow data. The new correlation is suitable for the following operation variables, the mass flux in the range of 192 to 810 kg/(m^2 s), the quality from 0.13 to 0.89, the pressure from 1.7 to 6.3 MPa and heat flux from 43.68 to 232.87 kW/m^2

Abstract

When capturing CO2 from biomass fired combined heat and power plants, the dynamic changes in the feedstock and the heat and electricity demands can clearly affect the operation of the boiler, which can further affect the performance of chemical absorption
CO2 capture. To handle such dynamic changes, control systems are needed. This work aims to compare the performance of two control strategies that can control the reboiler duty in the stripper to achieve a constant capture rate. Control strategy A uses the reboiler
temperature as input based on a PID controller; and control strategy B is a modification of control strategy A by introducing a feedforward compensation based on the flowrate of rich solution when regulating the reboiler duty. Based on dynamic simulations, it is found that control strategy B can reduce the settling time and capture more CO2 with a lower average energy penalty within a certain time length.

Abstract

Heat transfer deterioration (HTD) of supercritical CO2 heated in a tube will influence the thermal efficiency and safe operation of the energy system due to the occurrence of local high temperatures. To suppress the HTD of supercritical CO2, the Helmholtz oscillator is applied at the inlet of the test section. The experiments are conducted at the conditions of the mass flux from 121 to 600 kg m-2 s-1 and the heat flux from 14.7 to 106.1 kW m-2 with the operating pressure of 8.0 MPa. The heat transfer and comprehensive thermal performance are discussed with and without the Helmholtz oscillator. The results show that it can significantly suppress the HTD, and the overall thermal performance factor can be up to 2.28. The main reason is that the Helmholtz oscillator can strengthen the mutual disturbance between near-wall fluid with high temperature and central fluid. Therefore, the buoyancy effect is weakened and heat transfer to supercritical CO2 gets enhanced.

Abstract

The explosive growth of New-Energy Vehicles (NEV) worldwide, combined with heated development in autonomous driving industries, has introduced a new demand for more controllable and reliable vehicle braking systems. Nowadays, the electro-mechanical brake (EMB) system is replacing the hydraulic or pneumatic ones, with lower mechanical complexity, high reliability, better individual wheel control and lower service and operating costs. This paper is focused on achieving accurate clamping force control of a force sensor-less electro-mechanical braking system, with the major technical objectives being: to analyze existing clamping force control methods for sensor-less EMB systems, to achieve clamping force estimation for sensor-less EMB systems, and to experimentally verify that the developed clamping force control strategy is accurate and well controlled.

Abstract

While global health concerns and risks have risen in the Post COVID era, methods of sustainable and resilient energy strategies are needed for making green recovery in cities to reduce CO2 emissions and environmental risks. Cities are to be designed and redeveloped for being more sustainable and resilient to meet climate, urban and societal challenges. To pursue consensus for making effective community actions to mitigate urban carbon emissions, an urban digital platform is proposed to facilitate above systems design processes from scenario making, data analytics and performance evaluation to urban design plan making. The paper designs an urban digital platform to be open in data sharing, and transparent in decisions to empower users, communities and stakeholders to co-generate common goals for zero emission urban future.

Abstract

The major objective of this research is to support future-proof applications of rooftop photovoltaics (PV) and electric vehicles (EV) as batteries for urban decarbonization. Although extensive research has been conducted, the feasible pathways have often been limited due to the complexity of analyzing interdependencies of energy, environment, and cost effects as well as a lack of sectoral analysis for cities which could offer stepwise application strategies. Therefore, this research conducted techno-economic analyses for rooftop PV + EV with respect to multiple cities in South Korea using System Advisory Model (SAM), and different building sectors in Seoul using MATLAB. The results showed that CO2 emissions can be reduced about 49% when applying rooftop PV combined with EV in Seoul in 2030. The results also indicate that the investment of PV and EV in residential buildings should be prioritized in Seoul. This research will contribute to providing decarbonization pathways for Korean cities, and ultimately alleviating global warming.

Abstract

In the light of decarbonsation of existing building stock energy efficiency performance of all building periods should be evaluated. The focus of the paper lies on building built after the collapse of the Soviet Union and before stringent energy efficiency measures came into force. Complex analysis of energy performance parameters, indoor air quality, and in-situ measurements of thermal resistance of walls were performed. Results show that legislative norms have a significant impact on the thermal performance of thermal envelope, but there are no significant changes in ventilation heat losses. Analysis of energy consumption for heating indicates that the energy efficiency benchmark set for renovated buildings in Latvia is set too high and does not promote decarbonisation of existing building stock.

Abstract

Nowadays, large numbers of electric vehicles have been used all around the world. Moreover, in the near future, electric vehicles will continuously replace the petrol vehicles, and reduce carbon emissions in transportation systems. At the same time, considering a large numbers of electric vehicles (EVs) running on the real-world transportation systems, the temporal spatial electricity charging in real-time is an essential problem for the underlying power system. In this paper, we present a real-time simulation platform for the coupling of both the real-world transportation network and the power system. In this proposed platform, an open source traffic simulator called SUMO is adopted to simulate the electric vehicle charging in the real-world transportation network. And, a power system simulator implemented in Matlab is adopted to simulate the electric vehicle charging in the power system. The real-time communication interface is deployed to exchange message between transportation network and power system, which is implemented by a typical TCP/IP message protocol. The simulation results demonstrate that the proposed platform can real-time simulate the coupling of the real-world transportation network and power system and improve the efficiency of the simulation process.

Abstract

In the light of an urge for conceptually new ideas for raising energy efficiency to meet 2050 EU decarbonisation plans, building thermal envelopes could be given new functionalities. Thus, to compensate the irregularities in the availability of solar energy, phase change materials might serve as the energy storage medium in the building envelope. Paper presents the comparison of two phase change materials with different melting temperatures 21 ˚C and 28˚C for application in building thermal envelopes. Conditions of four seasons in Northern Europe climate are simulated in laboratory testing. The average temperature in phase change materials and small-scale indoor space are compared.