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• This paper focuses on daily natural gas consumption forecasting. • A novel hybrid model is developed for daily natural gas consumption forecasting. • The most recent datasets of four cities in three climate zones are collected. • An improved singular spectrum analysis is first proposed. In daily natural gas consumption forecasting, the accuracy of forecasting models is vulnerably affected by the noise data in historical time series. Singular spectrum analysis (SSA) is often introduced into hybrid models for denoising. However, as a deterministic-based algorithm, SSA does not give good results when a time series is contaminated with a high noise level. Considering this fact, this paper proposes an improved SSA (ISSA) that modifies the determination method of subseries selection in the reconstruction stage of SSA. Combining ISSA with long short-term memory (LSTM), a novel hybrid model, ISSA-LSTM, is thus developed. Additionally, for validating the robustness and superiority of ISSA-LSTM, the historical datasets of four representative cities located in three climate zones are collected as the training and testing datasets, and a comparison of ISSA-LSTM with five advanced models is performed. The results reveal that SSA would generate negative values when time series close to zero and the contribution of SSA in improving the forecasting accuracy of LSTM is insignificant. In contrast, ISSA avoids generating negative values and reduces the mean absolute range normalized error (MARNE) of LSTM by a range of 0.86–11.86%. Among the models, ISSA-LSTM achieves the best performance and its MARNEs for London (temperate zone), Melbourne (subtropical zone), Karditsa (subtropical zone), and Hong Kong (tropical zone) are 4.68%, 5.72%, 5.76%, and 14.10%, respectively. The MARNE of the tropical city is higher than that of others, which is caused by the complex natural gas consumption pattern of itself. [ABSTRACT FROM AUTHOR]

This paper reports a new knowledge-driven engineered feature learning approach in response to the Global AI Challenge for Building E&M Facilities held by the Electrical and Mechanical Service Department (EMSD) of the Hong Kong SAR. The results were awarded with a Grand Prize by the competition organizer. A dynamically engineered multi-modal feature learning (DEMMFL) method is proposed for predicting the cooling load of two office buildings. The DEMMFL model is estimated with the Lasso-ridge regression and compared with other well-known methods such as the Lasso. The novel approach applies control system knowledge to engineer useful features and explore load patterns for multi-mode modeling. Deep learning methods including LSTM, GRU, and AutoGluon are implemented for automated machine learning and tested in parallel to compare the performance of the proposed model with existing methods. The proposed model is demonstrated to predict long-term cooling load most accurately using engineered features from weather information only. • A new dynamic feature engineering method for office building cooling load prediction. • Slow and fast dynamic features engineered from available weather data only. • Control-knowledge based feature to learn on-hours dynamic responses. • Multi-modal approach with eight day-type features to learn occupancy loads. • Deep recurrent learning and AutoML methods compared to the proposed method. [ABSTRACT FROM AUTHOR]

• A new concept and feature of grid-responsive building and the needs are presented. • Opportunities/challenges for buildings to provide ancillary services are presented. • Applications/methods for HVAC systems to provide ancillary services are investigated. • Potential capacities of HVAC systems to provide ancillary services are quantified. Renewable electricity generations have been growing rapidly in recent years worldwide as a result of efforts to address the global energy issue. However, it has also imposed increasing challenges on the balance of power grids due to their intermittent nature. Building sector, as the largest consumer, is expected increasingly to play an important role in providing ancillary services (AS) to relieve stress and reduce the needs of investment for power balance of the smart grids. Grid-responsive building therefore becomes a worthwhile and essential feature of buildings today and in the future. This paper provides an overview of the classification, benefits, applications as well as methods/technologies for HVAC systems in non-residential buildings to provide ancillary services, as fast responses (i.e., in the magnitude of seconds or minutes) to the needs of smart grids. In addition, the challenges of applications and potential solutions are investigated and summarized. The potential capacities of HVAC systems in the entire non-residential building sector in Hong Kong for providing frequency regulation (FR) and spinning reserve are also quantified. [ABSTRACT FROM AUTHOR]

• A multi-model and multi-method ensemble approach for wind resource projection is proposed. • Future wind potential in Hong Kong is assessed for the first time. • Robustness of the climate change signal is evaluated. • An increase in wind power density during summer (+23.7 %) and a decrease during autumn (–15.1 %) in 2081–2100 are projected for SSP5-8.5. Harvesting renewable wind energy is among the most cost-efficient means of reducing carbon emissions and achieving carbon neutrality. However, wind resource is susceptible to climate change impacts since the global temperature increase will reshape atmospheric circulation patterns. To facilitate the evaluation of fine-scale wind energy potential under climate variability, this paper proposes and validates a multi-model and multi-method ensemble wind resource projection approach. Then this approach is utilized to investigate the future variation of wind resources in Hong Kong based on the combined use of global climate models from Coupled Model Intercomparison Project Phase 6 and long-term observations from meteorological stations. It is found that there is a significant increase in future wind resources during summer, while a remarkable decline is projected during autumn. Nevertheless, the variations of wind resources in winter and spring are relatively insignificant. The outcomes of this study are expected to offer a framework for fine-scale wind resource assessment under climate change, and facilitate the economic and risk assessments of future wind farm projects. [ABSTRACT FROM AUTHOR]

The paper studies the horizontal global, direct-beam and sky-diffuse solar irradiance data measured in Hong Kong from 2008 to 2013. A machine learning algorithm was employed to predict the horizontal sky-diffuse irradiance and conduct sensitivity analysis for the meteorological variables. Apart from the clearness index (horizontal global/extra atmospheric solar irradiance), we found that predictors including solar altitude, air temperature, cloud cover and visibility are also important in predicting the diffuse component. The mean absolute error ( MAE ) of the logistic regression using the aforementioned predictors was less than 21.5 W/m 2 and 30 W/m 2 for Hong Kong and Denver, USA, respectively. With the systematic recording of the five variables for more than 35 years, the proposed model would be appropriate to estimate of long-term diffuse solar radiation, study climate change and develope typical meteorological year in Hong Kong and places with similar climates. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports the investigation results of the energy payback time (EPBT) and greenhouse-gas payback time (GPBT) of a rooftop BIPV system (grid-connected) in Hong Kong to measure its sustainability. The 22kWp PV array is facing south with inclined angle of 22.5°. The hourly solar irradiance and ambient air temperature from 1996 to 2000 were used as weather data input. The annual power output was found to be 28,154kWh. The embodied energy for the whole system in the lifespan was 205,816kWh, including 71% from PV modules and 29% from balance of system (BOS). The percentage of embodied energy for silicon purification and processing reached 46%. The EPBT of the PV system was 7.3years, and the GPBT was estimated to be 5.2years considering fuel mixture composition of local power stations. This paper also discussed the EPBTs for different orientations, ranging from 7.1years (optimal orientation) to 20.0years (west-facing vertical PV façade). The results show that the ‘sustainability’ of a PV system is affected by its installation orientation and location. Choosing locations and orientations with higher incident solar irradiance is one key for the sustainability of BIPV technology applications. [ABSTRACT FROM AUTHOR]

This paper investigates the potential and feasibility of the offshore wind energy in Hong Kong. The potential offshore wind farm locations are selected after considering the man-made activities in Hong Kong waters that may come into conflict with the development of the offshore wind farms. The hourly wind data of ten years (2002–2011) in the corresponding potential wind farms are analyzed. The assessment for offshore power potential is obtained with the potential wind farm being optimized using the Multi-Population Genetic Algorithm (MPGA) which aims at getting a minimum cost of energy (COE) with a maximum power generation. The optimal wind turbine layout configurations are proposed with an economic analysis and monthly power generation. Results show that the potential offshore wind farm area in and beyond (2 km away from its boundary) Hong Kong is 357.78 km 2 (21.68% of the HK water area) and southeastern water area is the most suitable location for offshore wind farm development. In additions, the potential annual offshore wind power generation is 112.81 × 10 8 kW h which accounts for 25.06% of the total annual power consumption in 2011 if the wind turbine layout is optimized. The potential monthly offshore wind power contribution to the electricity demand is the highest in October (46.46%) and lowest in August (7.93%). [ABSTRACT FROM AUTHOR]

Abstract: Currently one of the most promising power solutions for remote rural areas and isolated islands which are far away from utility grid is the stand-alone solar photovoltaic (PV) renewable energy system or hybrid solar–wind power system. This paper presents the investigation results of a real remote solar PV project on an island in Hong Kong. The stand-alone PV system, rated at 19.8kWp, is established on a remote island for power generation to local residents. Power on this island was originally supplied by diesel generators and this new solar energy system has significantly reduced fuel costs and alleviated environmental pollution. The on-site entire system’s operating data was collected for one whole year in 2011, and the energy performance of the PV array, inverters, battery bank and the entire PV system were analyzed in terms of daily energy balance, normalized performance parameters and overall system energy utilization ratio. The results from this long term system monitoring and its evaluation enables a detailed inspection of system operating performance with respect to the technical issues, which provides a useful reference for future applications of solar photovoltaics in remote islands. [Copyright &y& Elsevier]

Abstract: Energy consumption by passenger transport in Hong Kong increased rapidly in the past decades and in 2008 it accounted for 19.7% of total energy use. Improving energy efficiency has been widely regarded as an effective way for reducing energy use in the transport sector. However, the expected energy savings from energy efficiency improvement are likely to be discounted due to the existence of rebound effect. This paper employs econometric models to estimate the direct rebound effect for private passenger transport in Hong Kong. We find that the magnitudes of the direct rebound effect are respectively 45% and 35% for 1993–2009 and 2002–2009, which indicates that there was a declining trend in the direct rebound effect for passenger transport over time. It also indicates that the direct rebound effect needs to be taken into consideration in assessing the impact of energy efficiency measures on reducing energy use in Hong Kong. [Copyright &y& Elsevier]

Abstract: The shading-type BIPV claddings can act as power generators as well as external shading devices and insulation panels. There is little available information about the impacts of orientations and inclinations on the combined energy effects of the shading-type BIPV claddings, including the power output of PV modules, the cooling load reduction of windows and concrete walls. It is worth studying the effects of different shading-type BIPV cladding designs on the total energy saving in order to maximize the system’s energy performance. By considering the meteorological conditions in Hong Kong, the energy effect of the shading-type BIPV claddings with different surface azimuth angles, in terms of electricity generation and cooling energy consumption reduction is analyzed in this paper. Based on the investigations, the optimum design of the shading-type BIPV claddings for different orientations can be achieved. [Copyright &y& Elsevier]

Abstract: In metropolitan cities like Hong Kong where land value is high, highrise commercial and residential buildings with “central core” design are developed. The lift lobbies in the buildings are usually located in the centre of the building to free up peripheral areas to provide valuable exterior view. The lift lobbies have no window provisions and electric lighting is switched on for 24h continuously consuming non-renewable energy. Different types of light guides/light pipes have been proven to be capable to transfer daylight into deep floor plan during both clear sky and overcast periods. However, the thickness of light guide requires 3m headroom clearance for installation whilst the headroom of the highrise buildings is usually limited to 2.8m in order to build more storeys. In this research, a remote source lighting system (RSL) is introduced to illuminate the enclosed lift lobbies. The system composed of prismatic light pipe and optic fiber to address the problem of limited headroom. Simulation of the system was carried out and reported in the paper, indicating that this lighting system can solve the energy consumption problem in the lift lobby in terms of renewable energy use and natural lighting application. This research concentrates on highrise residential buildings. [Copyright &y& Elsevier]

Abstract: Photovoltaic (PV) is one of the promising solar energy applications. Measured data can give the realistic performance of PV systems under actual operating environments for product selection and system design. This paper studies a grid-connected PV system installed in an institutional building. Technical data including available solar radiation and output energy generated were systematically recorded and analyzed. The performance of the PV system is elaborated in terms of energy, environmental and financial aspects. Feed-in-tariff (FIT) schemes with high electricity selling price can encourage the deployment of PV system. The monetary payback period (MPBP) for the PV system was computed to be 72.4years when the electricity buying price is equal to the electricity selling price. If carbon trading was considered, the payback was shortened to 61.4years. The embodied energy payback period (EEPBP) was estimated to be 8.9years. The findings would be useful for planning grid-connected PV installations and applicable to other spaces with similar architectural layouts. [Copyright &y& Elsevier]

Abstract: The ground-coupled heat pump (GCHP) system is becoming attractive for air-conditioning in some moderate-weather regions due to its high energy efficiency and reliable operation capability. However, when the technology is used in buildings where there is only cooling load in hot-weather areas like Hong Kong, the heat rejected into the ground by the GCHP systems will accumulate around the ground heat exchangers (GHE). This heat accumulation will result in degradation of system performance and increment of system operating costs. This problem can be resolved by using the hybrid ground-coupled heat pump (HGCHP) system, which uses supplemental heat rejecters to reject the accumulated heat. This paper presents a practical hourly simulation model of the HGCHP system by modeling the heat transfer process of the system’s main components. The computer program based on this hourly simulation model can be used to calculate the hour-by-hour operation data of the HGCHP system. As a case study, both a HGCHP system and a traditional GCHP system are designed for a hypothetic private residential building located in Hong Kong, and the economic comparisons are conducted between these two types of systems. The simulation results show that the HGCHP system can effectively solve the heat accumulation problem and reduce both the initial costs and operating costs of the air-conditioning system in the building. [Copyright &y& Elsevier]

Abstract: This paper reports the investigation results on application of the solar assisted air source heat pump systems for hot water production in Hong Kong. A mathematical model of the system is developed to predict its operating performance under specified weather conditions. The optimum flow rate from the load water tank to the condenser is proposed considering both the appropriate outlet water temperature and system performance. The effect of various parameters, including circulation flow rate, solar collector area, tilt angle of solar collector array and initial water temperature in the preheating solar tank is investigated, and the results show that the system performance is governed strongly by the change of circulation flow rate, solar collector area and initial water temperature in the preheating solar tank. [Copyright &y& Elsevier]

Based on the data collected in recent surveys, models have been established to represent the energy characteristics of living and dining rooms and bedrooms in typical residential buildings in Hong Kong, in respect of the layout and construction; the density and pattern of occupation; the power intensities and operating patterns of lighting and appliances; and air-conditioner operation patterns. With the help of computer simulation, the impacts of varying these characteristics on the annual space cooling load have been evaluated, which allowed representative internal load patterns for residential units to be defined. These are essential data for predicting energy use in residential buildings, which, in turn, is an indispensable part of studies on ways to assess and minimise energy use in such buildings. This paper presents the building model and the internal load and air-conditioner operation patterns established in the study. [Copyright &y& Elsevier]

• A novel coupled optical-electrical-thermal model of the bifacial PV module is developed. • Global irradiances of the front and rear sides are calculated by view factor and irradiance model. • Over 22% of the average bifacial gain can be achieved via yearly performance estimation. • Suggestions for optimizing the bifacial PV module performance are proposed. The bifacial photovoltaic (PV) technology has become prevalent in the global market in recent years as it can simultaneously collect the sunlight from both front and rear sides to achieve high power generation, however, there is limited attention from academic circle on this new technology particularly theory study in multiphysics simulation. This paper develops a comprehensive optical-electrical-thermal model for the bifacial PV module, in which the global irradiances of the tilted front and rear surfaces are obtained through the optical model, the cell temperature through the thermal model, and the power output through the electrical model accordingly. After validation, the coupled model is employed to conduct daily and yearly performance estimations, demonstrating 25.58% and 28.21% of the daily bifacial gain for sunny and cloudy days, respectively, and more than 22% of the yearly bifacial gain for Hong Kong and Shanghai. Besides, it is found that the bifacial gain under low irradiance is relatively high due to high diffuse fraction, indicating that bifacial modules have an advantage in adapting to various weather conditions, especially cloudy days. Furthermore, some suggestions are proposed to optimize the bifacial module by considering the effects of various installation and weather parameters on the PV generation. A tracking bifacial module, installed at an optimum tilt angle with high albedo, elevation, irradiance and wind velocity, but low ambient temperature, could achieve high energy yield, while a bifacial module facing east with high albedo, tilt angle, elevation, diffuse fraction, ambient temperature and wind velocity could achieve high bifacial gain. [ABSTRACT FROM AUTHOR]

• There are wide opportunities for zero-carbon building policy formulation for Hong Kong. • Risks co-exist, particularly geographic ones, but are outweighed by opportunities. • Opportunities and risks are complex, interactive, interchangeable and context-specific. • Recommendations for mitigating the risks highlight policy and business strategy. • Stakeholder partnership and government and client leadership are critical. There is a worldwide policy agenda of reducing buildings' carbon emissions. Zero-carbon building has emerged as an advanced model with policy support, but high-rise remains a knowledge gap. This paper aims to contribute a better understanding of the opportunities and risks of formulating and implementing a zero-carbon building policy, and identify recommendations for maximising the opportunities and minimising the risks. Hong Kong as a typical high-rise high-density city was considered as the case for study. The research was conducted through the combination of a policy review, a questionnaire survey, interviews and focus group meetings with several hundred professionals and stakeholders carefully selected using stratified sampling. Wide opportunities were identified, with most important ones including raising public awareness of sustainable living, reducing buildings' energy use and carbon emissions, and promoting strategic urban planning. However, risks were found to co-exist, with most significant ones including geographical obstacles to domestic renewable energy generation, heavy reliance on fossil fuels, and resistance of practitioners to the policy. Nevertheless, the opportunities were considered to outweigh the risks. Recommendations were identified to mitigate the risks, which are centred on policy guidance, business strategy, stakeholder partnership, and government and client leadership. The findings reveal the complex, interactive, interchangeable and context-specific features of the opportunities and risks, which alert to reconstruct a dialectical system framework of implementing zero-carbon building policy for Hong Kong. The yielding policy implications and recommendations should shape the reconstruction of that framework for high-rise high-density cities. [ABSTRACT FROM AUTHOR]