• Energy Research

The UK government’s Clean Growth Strategy unambiguously described the decarbonisation of heat as the UK’s greatest policy and technical challenge in meeting our carbon targets. Maximising the potential for energy efficiency in the existing domestic stock is critical to the low-carbon heat transition. Good information exists on the technical potential for energy efficiency measures in the UK stock, however, a lack of knowledge about current stock conditions and in-use factors places considerable uncertainty on how much of this technical potential is achievable in practice. \ud This study uses data from the fifth carbon budget (CB5) policy projections and updates the in-use factors using measured data from the National Energy Efficiency Database (NEED). This results in a 26% shortfall by 2035 in the anticipated energy savings through cavity, solid wall, and loft insulation compared to what is assumed in the CB5 projections. This will have costly implications for meeting future carbon budgets. Risks and policy implications are discussed. The practical potential for energy efficiency measures beyond cavity, solid wall, and loft insulation is explored.

Natural ventilation is gaining more attention from architects and engineers as an alternative way of cooling and ventilating indoor spaces. Based on building types, it could save between 13 and 40% of the building cooling energy use. However, this needs to be implemented and operated with a well-designed and integrated control system to avoid triggering discomfort for occupants. This paper seeks to review, discuss, and contribute to existing knowledge on the application of control systems and optimisation theories of naturally ventilated buildings to produce the best performance. The study finally presents an outstanding theoretical context and practical implementation for researchers seeking to explore the use of intelligent controls for optimal output in the pursuit to help solve intricate control problems in the building industry and suggests advanced control systems such as fuzzy logic control as an effective control strategy for an integrated control of ventilation, heating and cooling systems.

In arid climates, a significant portion of the urban peak energy demand is dedicated to cooling and air-conditioning during the summer. The rapid urbanization rates in developing countries, particularly in the Gulf Cooperation Council (GCC), have intensified the pressure on energy resources to meet the indoor comfort needs of residents. As a result, there has been a substantial increase in energy demand, with a 2.3% rise recorded in 2018. Electricity consumption in residential buildings accounted for over 48.6% of the total electricity consumption. The choice of building fabrics used in a residential building can significantly impact the building’s passive performance and carbon footprint. This study aimed to enhance our understanding of how specific fabric details influence cooling energy usage in arid climates. To achieve this, a validation simulation model was initially created as a base case for a residential housing typology in Al Ain, UAE. This was followed by a parametric energy evaluation of various building envelope features. The evaluation was based on the reduction of yearly cooling load energy. The simulation results indicate that incorporating 50 mm of expanded polystyrene insulation into the outside walls significantly reduced energy consumption for cooling requirements in the arid UAE climate. Furthermore, no substantial difference was observed in the various roofing choices, including cool and green roofs, gravels, and sand roofs. Additionally, we concluded that the total solar energy transmittance (g-value) of windows played a more significant role than thermal transmittance (U-value) in reducing solar heat gain within the spaces. These findings should guide strategic decisions on building envelope upgrading for sustainable societies.

We present the design, construction and operation of a novel building systems laboratory, the BubbleZERO—Zero Emission Research Operation. Our objective was to design a space to evaluate the performance of Swiss-developed low exergy building systems in the tropical climate of Singapore using an integrated design approach. The method we employed for evaluation in the tropics was to design and build a test bed out of the shipping containers that transported the prototype low exergy systems from Switzerland to Singapore. This approach resulted in a novel laboratory environment containing radiant cooling panels and decentralized air supply, along with a self-shading, inflated “bubble” skin, experimental low emissivity (LowE) glazing, LED lighting, wireless sensors and distributed control. The laboratory evaluates and demonstrates for the first time in Singapore an integrated high-temperature cooling system with separate demand-controlled ventilation adapted for the tropics. It is a functional lab testing system in real tropical conditions. As such, the results showing the ability to mitigate the risk of condensation by maintaining a dew point below 18 °C by the separate decentralized ventilation are significant and necessary for potential future implementation in buildings. In addition, the control system provides new proof of concept for distributed wireless sensors and control for reliable automation of the systems. These key results are presented along with the integrated design process and real-life tropical operation of the laboratory.

High temperature cooling is gaining more attention in commercial buildings of the tropical climates where temperature and humidity is high all year round. In this air-water system, radiant-convective cooling is provided into conditioned space through using higher chilled water temperature compared to conventional all air system. Radiant cooling panel, radiant slab cooling, passive/active chilled beams are the main design strategies for implementing this concept into buildings. This paper reviewed and summarized the recent published papers on applications of high temperature cooling systems in tropical buildings. The reported outcomes and conclusions from these studies were extracted and discussed to get a better understanding on overall performance of the systems which are designed based on this concept. The potential energy saving of this strategy was estimated to be in the range of 6–41% depending on design strategies and operational scenarios of system. Comfortable and healthy indoor environment is achievable for this design when a parallel air system satisfies latent load and ventilation requirement of space. Low air movement was the only reported comfort concern for this design since locally acclimatized occupants in the tropics prefer higher air movement compared to dry and temperate climates. Regarding the parallel air system strategy, DOAS with ceiling supply-ceiling exhaust is suggested to be the best choice to be coupled with high temperature cooling system. In addition, incorporation of energy recovery systems like membrane based air to air heat exchanger into DOAS can improve the overall efficiency of this design.

The use of air-conditioning, the largest energy demand for buildings in the tropics, is increasing as regional population and affluence grow. The majority of installed systems are split type air-conditioners. While the performance of new equipment is much better, the influence of the microclimate where the condensing units are installed is often overlooked. Several studies have used CFD simulations to analyse the stack effect, a buoyancy-driven airflow induced by heat rejected from condensing units. This leads to higher on-coil temperatures, deteriorating the performance of the air-conditioners. We present the first field measurements from a 24-storey building in Singapore. A network of wireless temperature sensors measured the temperature around the stack of condensing units. We found that the temperatures in the void space increased continuously along the height of the building by 10–13 °C, showing a significant stack effect from the rejected heat from condensing units. We also found that hot air gets stuck behind louvres, built as aesthetic barriers, which increases the temperature another 9 °C. Temperatures of around 50 °C at the inlet of the condensing units for floors 10 and above are the combined result, reducing the unit efficiency by 32% compared to the undisturbed design case. This significant effect is completely neglected in building design and performance evaluation, and only with an integrated design process can truly efficient solutions be realised. Energy and Buildings, 71 ISSN:0378-7788 ISSN:1872-6178

The deployment of low exergy concepts in buildings, which promotes high temperature cooling HVAC systems introduces alternative solutions in the tropical climate. This study evaluates the performance of a decentralized dedicated outdoor air system combined with a radiant cooling system (decentralized DOAS-RCS) in terms of occupant thermal comfort and indoor air quality for the tropical context. Different sets of operational scenarios (experiments) have been conducted in the BubbleZERO laboratory to realize the impact of system related parameters like ventilation rate and supply chilled water temperature on thermal comfort and indoor air quality. The results show that supply chilled water temperature and space cooling load have strong impacts respectively on the capacity of decentralized units and cooling panel, which consequently influence indoor air condition. Indoor air was predicted to be in comfort range (−0.2 < PMV < 0.2) only at specific periods of the day and an automatic control was required to modulate the system under various indoor and outdoor conditions. Main challenges of implementing DDOAS coupled with radiant cooling in the tropics include the condensation risk on the radiant panels, non-uniformity of panel surface temperature and low air movement inside the space.