Building Services Engineering Research & Technology

Air source absorption heat pump is promising in energy saving and emission reduction of heating and domestic hot water, but performs badly or even cannot work in cold climate. The ammonia/absorbent air source absorption heat pump with low-pressure boosting is proposed to solve the problem. The hybrid air source absorption heat pump + compressor system is modeled and the compression ratio is optimized to obtain maximum primary energy efficiency. The integrated system is simulated with air temperature ranging from −30℃ to 10℃ and hot water temperature from 30℃ to 60℃. Comparative simulations on three working fluids reveal that NH₃–LiNO₃ system has the lowest compression ratio and the highest primary energy efficiency value. By pressure boosting, the air source absorption heat pump can operate under air temperatures as low as −30℃. Primary energy efficiency of the hybrid system is about 15–50% higher than that of coal boiler, showing great potential for heat supply in cold regions.

Practical application: Heating and domestic hot water consumes a large amount of energy every year. Air source absorption heat pump can be a potential alternative to the traditional boiler systems in the point view of primary energy efficiency. However, air source absorption heat pump performs badly or cannot work when the air temperature is low. This paper presents a hybrid air source absorption heat pump with pressure boosting to improve the performance of the air source absorption heat pump heating system, making it operate under lower outdoor air temperatures with higher primary energy efficiency. The novel heat supply system is expected to make contributions to building energy saving as well as pollution reduction.

Heat transfers into refrigerated cabinets from their surroundings. Currently, this heat transfer is ignored in building design compliance protocols (National Calculation Methodology), and a heat gain to the zone is included in modelling the retail floor, to represent the energy use of the refrigeration system, although this is normally outside of this zone. Previous work has established that a store designed for energy reduction with the heat transfers to refrigerated cabinets from the surroundings included in the modelling could have at least 20–35% lower energy demand (and CO₂ emissions) than a store modelled and ‘optimised’ on the National Calculation Methodology basis. This paper therefore offers an appropriate algorithm for ‘negative gains’ relating to refrigerated cabinet heat transfers for use in design and compliance modelling of supermarket buildings.

Practical application: The algorithm offered, when incorporated into design modelling, will enable significantly improved identification of the sensitivity of the thermal balance of the supermarket building to variation of building envelope parameters, and thereby enable significantly improved energy savings to be realised.

Building more air-tight dwellings is having a deleterious impact on indoor air quality. In a range of recently completed dwellings CO₂ concentrations were measured in occupied bedrooms at unacceptable concentrations (occupied mean peak of 2317 ppm and a time weighted average of 1834 ppm, range 480–4800 ppm). Such high levels confirm that air-tight dwellings with only trickle ventilators as the ‘planned’ ventilation strategy do not meet the standards demanded by the Building Regulations. Reducing ventilation rates to improve energy efficiency and lower carbon emissions, without providing a planned and effective ventilation strategy is likely to result in a more toxic and hazardous indoor environment, with concurrent and significant negative long-term and insidious impacts on public health. Furthermore, the methodology underpinning the current regulations cannot be considered as creditable. While the complexity around numerical modeling often leads to conclusions based upon simplistic and unrealistic assumptions around all doors in a dwelling being open and trickle ventilators being unobstructed, this paper demonstrates that in ‘real life’ situations, this is not the case and could lead to significant risks of under ventilation. This is particularly the case when standards and guidance are based upon theoretically modeled scenarios that are not representative of real-life operation. The consequences of this are important in terms of the likely negative impacts on occupant health.

Since radiant floor heating systems utilise part of the building as a system for controlling the indoor environment, the integrated analysis considering the interaction between the building and the system needs to be conducted for the performance evaluation. Integrated simulation can be applied for this purpose; however, it is somewhat difficult to evaluate the impact of the system hardware such as hydronic circuits and heat sources due to the lack of modeling information. Although the experimental methods can guarantee the most reliable results, they have a limitation on the repetitive comparison due to the restriction of time, space and cost. For this reason, this study presents an emulation method that can mitigate the disadvantage of the simulation as well as experimental methods, especially for the performance evaluation of radiant floor heating systems. To achieve this, the factors to be considered in radiant floor heating systems were examined by reviewing the previous studies on the emulation. This study suggested an emulation method that can physically represent pressure loss in the hydronic circuits and heat output from the floor structure, which are distinguishing features of radiant floor heating systems. With the developed emulation method, this study showed that the control performance and energy consumption of a radiant floor heating system can be investigated.

Practical application: This study presents an emulation method to evaluate the energy consumption and control performance of radiant floor heating systems. The proposed emulation method will be able to supplement a pure simulation and to contribute to the development of an evaluation method considering the impact of system hardware on the overall performance of radiant floor heating systems. Therefore, it is expected that the results will be helpful to researchers for indoor environment, heating, ventilating and air conditioning engineers, system manufacturers and those who want to analyse the energy performance of radiant floor heating systems.

Nowadays, the most applied insulation material in the building sector is the expanded polystyrene. Different types of expanded polystyrene are used but more widely used is the graphite added type. Our research focuses on the analysis of heat conductivity and sorption properties of expanded polystyrene as these two are the most important physical properties from energy saving point of view. In this paper, the variation of heat transfer coefficient of an insulated wall is analysed in function of humidity content of insulation material. Brick and concrete walls with 0.4 m thickness were chosen for substrate and 0.1 m expanded polystyrene (30, 100, 150, 200 and the so-called grey expanded polystyrene) materials were applied as insulating layers. The investigations of sorption behaviour of the materials are important from the point of view of fundamental research and building technology as well. Sorption data taken from our previous measurements results were used for predicting the change of the overall heat transfer coefficients of different wall structures constituted this way.

Practical application: The present technical note is based on our previous measurement results. Water can cause undesirable changes in the building structures and introduced in this article. During the fixing procedure of the additional insulating of a given building bad weather conditions (high relative humidity and/or low external temperature) can dominate. These phenomena can be imagined for building new houses. By the ‘in-building’ of the moisture into the wall structure, numerous and measurable change can happen in the U-value of the building envelope. The presented changes are estimations only, but can be used and can also help for planning and executing the insulating process.

Renewable energy plays a crucial role in replacing major part of fossil fuels to generate sustainable, inexhaustible, clean, and safe energy. In Hong Kong, solar energy has been identified suitable for wide-scale applications. Photovoltaic (PV) and solar water heating (SWH) facilities are the two promising solar-based conversion technologies. Electricity and hot water generations via solar energy means fossil fuel saved together with the likely pollutants and greenhouse gases reductions. However, there are a number of barriers including high initial cost and large installation space required. This paper studies the cost, energy, and environmental issues when PV and SWH systems are widely used in Hong Kong. The energy expenditures in the forms of electricity, gas, and hot water, and the global solar radiation in Hong Kong were analyzed. The total required land areas, the financial implications, and the environmental benefits for such solar energy applications were estimated and reported.

Practical application: Solar energy plays an important role in replacing fossil fuels to generate electricity without emitting pollutants and requiring no fuel. This paper analyzes the energy, financial, and environmental aspects for solar thermal and solar electric installations. The findings in this study provide the information when active solar energy systems are widely applied in Hong Kong.

Increasing building tightness is one of the measures taken by the construction industry to reduce energy losses, but leading to unhealthy environments. Efficient ventilation strategies with low energy consumption are necessary in order to design and improve the existing forced ventilation systems. This paper assesses the potential use of different strategies, independently from the architectural design, to achieve efficient ventilation. To this end, the airflow pattern and the age of air have been assessed in an en suite bedroom within a Spanish house with the use of computational fluid dynamics predictions. The computational fluid dynamics model predictions were validated by the comparison against experimental measurements, with good agreement. An alternative ventilation strategy is proposed, not affecting the architectural design of the room. Statistical analysis is used to assess and compare the results obtained for the different cases simulated. Results show that although the room has a forced ventilation system, air stagnates and ventilation are not homogeneous. Statistical analysis shows that this strategy produces a significant impact on indoor air quality, particularly in bedroom areas where air tends to stagnate.

Practical application: The Spanish Building Code provides a minimum level of air quality within the buildings although it does not ensure an efficient design of the ventilation system, being necessary the use of guidelines or other recommendations to advise the designers in order to achieve efficient ventilation designs. Implementation of strategies independent from the architectural design, as studied in this work, can improve the indoor air quality and therefore reduce the global building energy consumption. In addition, these solutions are recommended for construction works requiring quick-easy implementation without disturbing the inhabitants of a house and allowing the normal use of the building during the refurbishment works.

Energy-saving elevator dispatching has been recognized as a challenging issue in building transportation, and we develop a novel energy-saving dispatching strategy for regenerative group-elevator system. Group-elevator dispatching is a typical combinatorial optimization problem, and three keys of the dispatching optimization are optimization method, objective, and model. The three keys of energy-saving-oriented elevator dispatching are studied in this paper. First, robust optimization method is introduced to handle dispatching optimization under uncertain elevator traffic flows; uncertain flows influence energy-saving dispatching seriously. Second, dispatching energy-objective function for regenerative group-elevator system is derived both schedule energy for four traffic patterns (up-peak, down-peak, up/down-mixed, and night) and return energy for two peak patterns (up-peak and down-peak) are considered. Third, four robust optimization-dispatching models for four traffic patterns are built, and optimization objectives of four models are minimizing the energy-objective function. Moreover, because we cannot solve robust optimization models with uncertain parameters directly, model counterpart transformation is studied. Finally, we solve the four transformed models by Linear Interactive and General Optimizer software and obtain robust optimization-dispatching solutions. In practice, four energy-saving-dispatching robust optimization models are switched according to real-time traffic patterns, and elevators are dispatched based on the dispatching solutions. We reduce elevator system-energy consumption effectively and keep average waiting time of the passengers acceptable under multi-traffic patterns. Simulation results demonstrate the validity of our strategy.

Practical application: Group-elevator system spends much unnecessary energy because of the uncertainty of elevator passenger-traffic flows. This paper develops an energy-saving elevator-dispatching optimization strategy, which is immune to the uncertainty of four typical traffic flows. In practice, we update the group-elevator controller by our algorithm to realize energy-saving dispatching of regenerative group-elevator system under multi-traffic patterns.