过程仿真工程 节能减排技术或绿色建筑技术 开发新模型 拓展系统性能 提升针对性
Monitoring and simulation of an existing solar powered absorption cooling system in Zaragoza (Spain) Applied Thermal Engineering
In 2007 and 2008 the performance of a solar powered absorption cooling installation was analyzed. The solar cooling system consists of 37.5 m of flat plate collectors, a 4.5 kW, single effect, LiBr–H2O rotary absorption chiller and a dry cooler tower. The performance analysis of the solar driven chiller shows average values of COP close to 0.6 in 2007 and between 0.46 and 0.56 in 2008. Concerning to the average cooling power, the chiller reaches values between 4.0 and 5.6 kW in 2007 and between 3.6 and 5.3 kW in 2008.
During the analysis phase, a detailed model of the solar cooling system was developed using the simulation environment TRNSYS. The results of the simulation were validated with the experimental ones, and presented in this paper. The measured data as well as the simulation results of the installation show the strong influence of the cooling water temperature and the generator driving temperature on the COP. For this reason an alternative heat rejection sink was design. Among the alternatives, a geothermal sink was chosen since there is a water well located in the surroundings of the solar cooling installation. The first results of the studies carried out show an improvement on the COP up to 42%.
1. Introduction 2. Scope of the work 3. Description of the installation 4. Simulation model and validation 5. Methodology 6. Results 6.1. Data analysis 6.2. New heat rejection system 7. Conclusions Acknowledgements Nomenclature
Applying a multi-objective optimization approach for Design of low-emission cost-effective dwellings Building and Environment 多目标家居环境与建筑环境设计 优化设计与成本/节能减排
Modern buildings and their HVAC systems are required to be not only energy-efficient but also produce fewer economical and environmental impacts while adhering to an ever-increasing demand for better environment. Research shows that building regulations which depend mainly on building envelope requirements do not guarantee the best environmental and economical solutions. In the current study, a modified multi-objective optimization approach based on Genetic Algorithm is proposed and combined with IDA ICE (building performance simulation program). The combination is used to minimize the carbon dioxide equivalent (CO2-eq) emissions and the investment cost for a two-storey house and its HVAC system. Heating/cooling energy source, heat recovery type, and six building envelope parameters are considered as design variables. The modified optimization approach performed efficiently with the three studied cases, which address different summer overheating levels, and a set of optimal combinations (Pareto front) was achieved for each case. It is concluded that: (1) compared with initial design, 32% less CO2-eq emissions and 26% lower investment cost solution could be achieved, (2) the type of heating energy source has a marked influence on the optimal solutions, (3) the influence of the external wall, roof, and floor insulation thickness as well as the window U-value on the energy consumption and thermal comfort level can be reduced into an overall building U-value, (4) to avoid much of summer overheating, dwellings which have insufficient natural ventilation measures could require less insulation than the standard (inconsistent with energy saving requirements) and/or additional cost for shading option.
1. Introduction 2. House and its HVAC system 2.1. General description 2.2. Initial designs 2.3. Simplified model including operable window 3. Formulation of the optimization problem
3.1. Design variables 3.2. Objective functions 3.3. Constraint function 4. The modified optimization approach 5. The simulation-optimization approach 6. Results and discussion 6.1. Case 1 6.2. Case 2 (DH24 ≤ 2400 ° h) C 6.3. Case 3 (DH24 ≤ 1000 ° h) C 7. Comparison with results from a brute-force search method 8. Comparison of the three cases 9. Conclusions Acknowledgements
Proposal and analysis of a high-efficiency combined desalination and refrigeration system based on the LiBr–H2O absorption cycle—Part 2: Thermal performance analysis and discussions Energy Conversion and Management
This paper continues and concludes the study of the proposed high-efficiency combined desalination and refrigeration system based on the LiBr–H2O absorption cycle introduced in the paper that is Part 1 [Proposal and analysis of a high-efficiency combined desalination and refrigeration system based on the LiBr–H2O absorption cycle––Part 1: System configuration and mathematical model. Energy Convers Manage 2010;52:220–7], in which also the mathematical model and its validation are presented in detail. Specifically, the thermal performance of the proposed ARHP–MEE (absorption refrigeration heat pump integrated with a multi-effect evaporation desalter) system, is analyzed, and a parametric sensitivity analysis and a rough economic evaluation are carried out, to clarify and quantify the performance of this combined refrigeration and water system. Typically, driving steam with saturation pressure of 0.15–0.35 MPa and corresponding saturation temperature of 111.4–138.9 ° is applied to run the C system. The combined system has good internal synergy, as demonstrated by an energy saving rate of 42% compared with the separate refrigeration-only and water-only systems in a base-case study. The refrigeration-heat cogenerated ARHP subsystem is the main reason for the synergy, with a coefficient of
performance of about 1.6 and exergy efficiency above 60% when driven by 0.25 MPa saturated steam. A rough economic analysis indicates qualitatively that there is no penalty in capital equipment for an ARHP–MEE system when compared with the two single-purpose systems, and the higher energy utilization rate of the system makes the energy/operating cost lower.
Nomenclature 1. Introduction 2. Base-case performance 3. Sensitivity analysis and parameter range 3.1. Sensitivity to the generator approach temperature ?T1–6 3.2. Sensitivity to the LiBr–H2O strong-and-weak solution concentration difference ?X 3.3. Sensitivity to the condensation temperature T10 of the heating steam in ED1 3.4. Sensitivity to the motive steam pressure p1 4. Discussion 5. Conclusions Acknowledgements
Energetic performance analysis of a ground-source heat pump system with latent heat storage for a greenhouse heating Energy Conversion and Management
In this study, a ground-source heat pump heating system with a latent heat thermal storage tank was designed while its thermal energy storage performance was investigated. The heating system mainly consists of a ground heat exchanger, a heat pump, a cylindrical latent heat thermal storage tank, measuring units and a heating space of model-sized glass greenhouses with 30 m , located in the greenhouse district of F?rat University, Elaz??, in Turkey. In the experiments, the performance characteristics of a ground-source heat pump greenhouse heating system with a 246 m horizontal 12.7 mm nominal diameter horizontal closed-loop ground heat exchanger and the use of phase change materials (PCM) for energy saving and management in greenhouses were investigated.
The heating coefficient of performances of the ground-source heat pump (COPHP) and the overall system (COPsys) are obtained, to be in the range of 2.3–3.8 and 2–3.5 respectively. Although significant savings are possible with this heating system, a substantial investment in equipment and facilities may be required. The experiments results were obtained from October to May in heating seasons of 2005–2006. The results showed that the utilization of ground-source heat pump-PCM is suitable for greenhouse heating in this district.
Nomenclature 1. Introduction 2. Experimental set-up and performing the experiments 2.1. Measurements 2.2. Test procedure 3. Analysis of energy balance for the greenhouse 5. Conclusions Acknowledgements
Advancement of solar desiccant cooling system for building use in subtropical Hong Kong 香港太阳能制冷/降温用设备/空调系统 先进技术及其实施效果
The solar desiccant cooling system (SDCS) had a saving potential of the year-round primary energy consumption as compared to the conventional air-conditioning system for full fresh air application in the subtropical Hong Kong. In order to further enhance its energy efficiency, advancement of the basic SDCS was carried out through a strategy of hybrid design. Six hybrid system alternatives of SDCS were therefore proposed, three for full fresh air design while another three for return air design for the building zone. Year-round performance evaluation of each solar hybrid desiccant cooling system was conducted for typical office application under different climatic and loading conditions. All the six hybrid system alternatives were found technically feasible, with up to 35.2% saving of year-round primary energy consumption against the conventional air-conditioning systems. Among the hybrid alternatives,
recommendations were made on the SDCS hybridized with vapour compression refrigeration for full fresh air design; and the SDCS hybridized with vapour absorption refrigeration for return air design, since they had the saving potentials of both primary energy and initial cost. These two hybrid system alternatives used evacuated tubes, a more economical type of solar collectors compared to the PV or PVT panels.
Nomenclature 1. Introduction 2. Design of solar hybrid desiccant cooling systems 2.1. SDCSFA-VCR 2.2. SDCSFA-DVCRPV 2.3. SDCSFA-DVCRPVT 2.4. SDCSRA-DVCRPV 2.5. SDCSRA-DVCRPVT 2.6. SDCSRA-VAR 3. Dynamic simulation for year-round operation 3.1. Desiccant wheel 3.2. DC-driven vapour compression refrigeration cycle 3.3. Vapour absorption refrigeration cycle 4. Details and parameters of system simulation 4.1. Building zone 4.2. General design of system alternatives of solar hybrid desiccant cooling 4.3. Desiccant wheel 4.4. DC-driven vapour compression refrigeration chiller 4.5. Vapour absorption refrigeration chiller 5. Results and discussion 5.1. Performance indicators 5.2. Comparison among SDCS, hybrid system alternatives and conventional air-conditioning systems
5.2.1. Solar fraction and coefficient of performance 5.2.2. Primary energy consumption 5.2.3. Benchmarking with conventional centralized air-conditioning systems 5.2.4. Monthly performances of different alternatives of solar hybrid desiccant cooling system 6. Conclusion Acknowledgements
The solar desiccant cooling system had primary energy saving potential. energy efficiency was made through hybrid design. refrigeration was recommended. recommended.
Further advancement of
SDCS hybridized with vapour compression
SDCS hybridized with vapour absorption refrigeration was also
Performance analysis of liquid desiccant based air-conditioning system under variable fresh air ratios
In conventional air-conditioning system, fresh air volume is always restricted to save energy, which sacrifices indoor air quality (IAQ) to some extent. However, removing the latent load of air by liquid desiccant rather than by cooling is an alternative way of reducing energy consumption. Therefore, IAQ can be improved by increasing the volume of fresh air introduced into an air-conditioning system. In this paper, a liquid desiccant based air-conditioning system is studied, with the system performance under various fresh air ratios analyzed using simulation tests. In addition, the proposed system and a conventional system are compared. In the proposed system, with the increase in fresh air ratio, the heating load for solution regeneration rises, the dehumidification efficiency increases and the regeneration efficiency drops. The coefficient of performance (COP) of the liquid desiccant based system decreases sharply when the fresh air ratio exceeds 60%. The results also show that the proposed system can save power notably. The maximum power saving ratio is 58.9% when the fresh air ratio is 20%; however, the ratio drops when the fresh air ratio increases. These findings will be beneficial in the selection of fresh air ventilation strategies for liquid desiccant based air-conditioning systems.
Nomenclature 1. Introduction 2. System description and performance simulation 2.1. System description 2.2. Air handling process 2.3. Performance simulation 3. Results and discussion 4. Conclusions Acknowledgements
Comparing different control strategies for indoor thermal comfort aimed at the evaluation of the energy cost of quality of building
The rapid improvement in the standard of living requires more detailed and sophisticated methods of evaluating comfort conditions. But, maintaining thermal comfort conditions in confined environments may require complex regulation procedures and the proper management of heating, ventilating and air conditioning (HVAC) systems. In turn, the requirements for indoor thermal comfort do not necessarily coincide with those of energy saving purposes, which in the last years are becoming a crucial issue owing to the enactment of the European Energy Performance of Buildings Directive (EPBD).
The aim of this work is to compare different indoor control thermal comfort strategies in view of the evaluation of the energy cost of quality in buildings.
In particular, a new PID-fuzzy controller is presented and compared with a classic ON–OFF controller. The performances of the two controllers are quantified and compared by means of two cost functions that are based on the quadratic forms of the overall energy required by the thermal fluid and of the deviation from the preferred set point of the predicted mean vote (PMV). It is found that the application of the PID-fuzzy controller results in lower costs of energy input and lower deviation from set point of PMV.
2. Indexes adopted for evaluating the performance of HVAC control systems 2.1. Indexes of thermal comfort performance 2.2. Indexes of energy performance 3. Controllers comparison 3.1. The classic hysteresis ON/OFF controller 3.2. The adopted PID-fuzzy controller system 4. Results and discussion 5. Conclusions Appendix. Simplified test dynamic model Nomenclature
A choice experiment to estimate the effect of green experience on preferences and willingness-to-pay for green building attributes
As the number and complexities of green building developments are mainly driven by market demands, understanding of end-user behaviors towards their development eventually should play a crucial role on determining their successes. However, very few studies have been attempted to explore end-user behaviors towards green building development. This study successfully applied discrete choice experiments to reveal whether residents with green experience will have different preference and willingness-to-pay values for enhancements on various aspects of environmental performance in green buildings. Generally, both green and conventional residents had strong preferences and were willing to pay more for improving various aspects of environmental performance in green residential developments. They are found to be willing to pay more for energy conservation, than indoor air quality improvement, noise level reduction, landscape area enlargement, or water conservation. No significant differences are found in the preferences between green and conventional residents for energy conservation, indoor air quality improvement, indoor noise reduction, or water conservation, However, green residents were found to be willing to pay significantly less than the conventional residents for enlarging the landscape area within a residential development, despite it was perceived by green residents as one of the major elements that differentiate a green from a conventional development.
1. Introduction 2. Methodology 2.1. Introductory section on awareness and understandings of a green residential development 2.1.1. Eliciting preferences for a green residential development 2.1.2. Identification of attributes and levels of attributes 2.1.3. Blocking design 2.2. Data collection 2.3. Data analysis and procedures 3. Results 3.1. Participants’ personal characteristics 3.1.1. Perception and awareness of green residents 3.2. Quality assurance 3.3. Evaluated residential development quality 3.3.1. Green experiences 3.3.2. Tradeoff among different attributes 3.3.3. Willingness-to-pay for enhanced environmental performance of a residential development 4. Discussions and conclusions Acknowledgements
Performance analysis of a liquid desiccant and membrane contactor hybrid air-conditioning system
The present study examines the performances of a hybrid air-conditioning system in which a vapour-compression inverse cycle is integrated with an air dehumidification system working with hygroscopic solution and hydrophobic membrane. This model may be a valid alternative to traditional summertime air-conditioning system, in which the air is cooled to below its dew-point temperature and subsequently reheated.
The proposed hybrid system involves simultaneously cooling and dehumidifying the air conveyed to the conditioned ambient in an air-solution membrane contactor. An LiCl solution is cooled by means of a
vapour-compression inverse cycle using the refrigerant KLEA 407C. The solution is regenerated in another membrane contactor by exploiting the heat rejected by the condenser.
A SIMULINK calculation programme was designed in order to simulate the system under examination in steady-state conditions. The performances of the system were analysed on varying a few significant operating parameters, and were compared with those of a traditional direct-expansion air-conditioning plant in typical summertime conditions. The results of the simulations revealed significant energy savings, which, in particular operating conditions, may exceed 50%.
1. Introduction 2. Description of the system 3. Case study 4. Results and discussion 5. Conclusions List of symbols Appendix A. Mathematical model of membrane contactors A.1. Determination of ρa A.2. Determination of G v A.2.1. Vapour mass transfer in the gas phase A.2.2. Vapour mass transfer through the membrane A.3. Water mass transfer in the liquid phase A.4. Determination of TwB and TwA
Capturing energy-saving opportunities in make-up air systems for cleanrooms of high-technology fabrication plant in subtropical climate
Operation of make-up air units (MAUs) for cleanrooms of high-technology fabrication plant in subtropical climates is very energy intensive, in that it is expected to deliver conditioned air at elevated airflow rates, compared to conventional commercial applications. Optimizing the design of MAU via reducing or displacing mechanical cooling or electrical heating processes can improve energy efficiency in
cleanrooms since cleanroom air-conditioning systems typically use 30–65% of the total energy consumption in a high-tech fabrication plant . This paper investigates the difference in energy efficiency performance of MAU systems with different pre-cooling and preheating/humidification schemes. Additionally, a comparative study was carried out for humidification schemes including wet media, directly atomized water, steam, and two-phase flow. The results show that energy recovery by DCC water return method exhibits the best energy efficiency among a total of eight schemes evaluated in this study. In addition, wet media scheme is the best humidification scheme in winter time, compared with the other three types of humidification schemes.
1. Introduction 2. Objectives 3. MAU design characteristics and methodology 3.1. MAU base design 3.2. Alternative MAU design and operation 4. Results and discussion 4.1. Different pre-cooling/reheating scheme for MAUs 4.2. Different heating/humidification energy consumption for MAU 5. Conclusions
Air-conditioning systems typically use 30–65% of the energy in a high-tech fab. water return method is the best energy-recovery method studied. energy efficient humidification scheme investigated.
Dry Cooling Coil
Wet media scheme is the most
Infrared thermovision technique for the assessment of thermal transmittance value of opaque building elements on site
Due to new regulations in the field of energy saving, international standards concerning energy requirements of buildings have been developed. In this field, during the design phase, one of the most important parameters to be considered is the value of heat losses coefficient through the envelope.
Anyway, very often a great difference is experienced between predicted performance of building elements as calculated using the methods prescribed in technical standards, and the one considering as-build conditions, particularly in the field of building renovation where the envelope thermal transmittance value must be measured on site. Till now, the only method accepted by international standards is the heat flowmeter (HFM) that presents some restriction and some uncertainty in the results. In this study a faster and less invasive method is proposed, the infrared thermovision technique (ITT) whose full potentiality has never been investigated yet, in order to acquire quantitative data of real thermal transmittances of the building envelope in a quasi-steady state condition. The theoretic background is presented together with the application in three case studies. The results indicate that, following a specific methodology, it is possible to record significant data useful to perform a proper assessment of energy performance of existing buildings.
1. Introduction 1.1. Aim of the paper 2. The heat flowmeter method 3. Infrared thermovision technique 3.1. Equipment 3.2. Theoretical basis 3.3. The measurement of emissivity 3.4. Other temperature reading 4. Case studies 4.1. Case study A 4.1.1. Results with the HFM method 4.1.2. Results with the ITT method 4.1.3. Comments on the results 4.2. Case study B 4.3. Case study C 5. Conclusions
Characterization and performance evaluation of a full-scale activated carbon-based dynamic botanical air filtration system for improving indoor air quality
A dynamic botanical air filtration system (DBAF) was developed for evaluating the short and long-term performance of botanical air cleaning technology under realistic indoor conditions. It was a fan-assisted with controlled air-flow, activated-carbon/hydroculture-based potted-plant unit. The DBAF was first tested using a full-scale stainless chamber to evaluate its short-term performance. It was then integrated in the HVAC system of a new office space (96.8m ) to study the effects of moisture content in the root bed on the removal efficiency, and the long-term performance. The results indicated that 5% outdoor air plus botanical filtration lead to the similar indoor formaldehyde/toluene concentration level as 25% outdoor air without filtration, which means that the filtration system was equivalent to 20% outdoor air (476m /h). The DBAF was effective for removing both formaldehyde and toluene under 5% to 32% volumetric water content of the root bed. It also performed consistently well over the relatively long testing period of 300 days while running continuously. The reduction in outdoor ventilation rate while using the botanical filtration system to maintain acceptable air quality would lead to 10 to 15% energy saving for the cold climate (Syracuse, NY), based on simulation analysis using EnergyPlus. For winter condition, the filter was also found to increase the supply air RH by 20%, which would decrease the dryness of air. For summer condition, the increase of RH in summer would be within 15% of the RH condition when no botanical air filtration is present.
Energy performance analysis on telecommunication base station
Telecommunication base station (TBS) has high indoor IT heat dissipation rate, and cooling load exists almost all year around. Energy consumption of air-conditioning system consumes 30% 50% of the TBS
entire energy. Envelop and heat pipe assisted air-conditioning system performances are investigated by using annual hourly simulation software. In cold city Harbin, high insulation envelop is recommend to avoid heating requirement in winter; and in warm city Guangzhou, low insulation envelop is recommend to reduce the annual cooling load. Shading and roof ventilation have little impact on the reduction of cooling load. Simplified analysis method based on daily average steady values is proposed, which can reveal the main performance influencing factors and clearly direct the main approach in energy saving. The simplified method can accord well with numerical results and tested results available in literature. Contribution of each heat source can be clearly gained and analyzed, solar radiation doesn’t possess large effect in TBS. Ideal thermal resistance with no heating or cooling requirement is then derived, envelop can be easily optimized and contribution of using heat pipe such kind of outdoor cooling source method can be easily obtained.
Experimental study on thermal behavior of a building structure using rubberized exterior-walls 独立式建筑物/设施的外墙设计规范与原则 实验研究开发方法
Addition of scrap-tire pieces into cementitious composites improves their thermal insulation performance.
Development of such construction materials with lower thermal transmittance reusing these wastes is a challenging issue since it provides a combined solution for today's energy saving and environmental pollution concerns. In favor of this, recent European Union directives have brought quiet strict limits to reduce energy consumption and landfill disposal of solid wastes. A model room whose exteriors are fully made with scrap-tire added concrete is built here to increase its thermal protection. A standard/conventional room at identical dimensions but surrounded by ordinary concretes is also built to examine influence of scrap tire addition on room's thermal protection. Long-term thermal behaviors of these two rooms are investigated and compared under real atmospheric environments. Their indoor temperatures reveal that addition of scrap tire pieces lowers both indoor temperature variations and the effect of outdoor conditions. As an example, mean values of yearly thermal time lag are found to be 3.28 and 2.96 hours respectively for the rooms built with and without using scrap tire pieces, corresponding to nearly 11% improvement in thermal protection. Results in overall verify that scrap tire addition improves thermal protection of the room and it is a cost effective solution for people with low income and/or individuals living in rural areas.
Performance enhancement of conventional combined cycle power plant by inlet air cooling, inter-cooling and LNG cold energy utilization
This paper has proposed an integrated advanced thermal power system to improve the performance of the conventional combined cycle power plant. Both inlet air cooling and inter-cooling are utilized within the proposed system to limit the decrease of the air mass flow contained in the given volume flow as well as reduce the compression power required. The latent heat of spent steam from a steam turbine and the heat extracted from the air during the compression process are used to heat liquefied natural gas (LNG) and generate electrical energy. The conventional combined cycle and the proposed power system are simulated using the commercial process simulation package IPSEpro. A parametric analysis has been performed for the proposed power system to evaluate the effects of several key factors on the performance. The results show that the net electrical efficiency and the overall work output of the proposed combined cycle can be increased by 2.8% and 76.8 MW above those of the conventional combined cycle while delivering 75.8 kg s
of natural gas and saving 0.9 MW of electrical power by
removing the need for sea water pumps used hitherto. Compared with the conventional combined cycle, the proposed power system performance has little sensitivity to ambient temperature changes and shows good off-design performance.
2. Description of the proposed combined power system 3. Analyses 4. The cycle performance 5. Parameter sensitivity analysis and discussion 6. Conclusion Acknowledgements
Active pipe-embedded structures in buildings for utilizing low-grade energy sources: A review
Low-grade energy sources such as geothermal energy, favorable ambient air and industrial waste heat etc. exist widely. Sufficient utilization of these low-grade energy sources may reduce our daily dependence on high-grade energy sources such as electricity resulting in reduced emission of green house gas for environmental conservation. Active pipe-embedded structure as floor/ceiling usually with water as the medium to carry heat or coolth may utilize these low-grade energy sources for providing space air-conditioning. Compact arrangement of pipes in the structure may significantly enlarge heat transfer surface between the slab mass and water in the pipe allowing substantial heat flows even for relatively small temperature differences. Application of the heat or coolth storage capacity of this structure for preheating or pre-cooling is also one among the advantages of this structure for shifting load and exploiting the nighttime cheap electricity tariff in some regions. This paper presents the technology of the active pipe-embedded structure for utilizing widely existing low-grade energy sources following by a comprehensive review on the heat transfer calculation models of this structure and its practical applications in real building systems for space air-conditioning. This review shows that more works on the active structure, especially simple and transient models for dynamic and accurate performance prediction and easy integration with existing building energy simulation packages, are worthwhile for further promoting the practical application wherever the low-grade energy sources are favorable.
1. Introduction 2. The technology 2.1. Open system coupled with cooling towers
2.2. Closed system coupled with chillers/heat pumps 2.3. Open system using ground water 2.4. Closed system coupled with ground heat exchangers 2.5. Miscellaneous systems 3. Calculation models of pipe-embedded structures 4. Practical application and performance evaluation 5. Conclusion Acknowledgements
The effects of roof covering on the thermal performance of highly insulated roofs in Mediterranean climates 屋顶冷却系统效益分析
While the EU Directive 2002/91/CE on the Energy Performance of Buildings (EPBD) clearly establishes regulations for the thermal insulation of buildings for saving energy in winter, the summer strategy is described by a little more than qualitative provisions. As a consequence, in the national requirements, the high insulation of the building envelope is considered as the principal strategy to control energy consumption even in summer, regardless of the different climates. This approach leads to a homologation of the building trade, and imposes construction technology and materials which do not adhere to the traditional way of making buildings, like in Southern Europe. Here, the “over insulation” of buildings runs the risk of reducing the effectiveness of traditional passive cooling strategies (thermal mass, air permeability of the roof covering, roof ventilation) and could have adverse effects on internal comfort. In this paper, we focus on the effects of over insulation on the thermal performance of roofs in summer, by analyzing experimental data from monitoring a full-scale mock-up in Italy. Results show how an increase in insulation thickness reduces the effectiveness of traditional passive cooling strategies, as an effect of the thermal decoupling between the interior and the upper layers of the roofs.
Nomenclature 1. Introduction
2. Scientific background 3. Materials and methods 4. Assessment of the overall performance of highly insulated roofs 5. Influence of roof covering features on thermal performance 6. Conclusions
Transient hygrothermal behaviour of a hemp concrete building envelope
The sustainable world's economic growth and people's life improvement greatly depend on the use of alternative products in the architecture and construction, such as industrial wastes conventionally called green materials. For this purpose, hemp concrete is more and more recommended by the eco-builders because hemp is a renewable plant, recyclable and does not degrade within time. It corresponds perfectly to the requirements of high environmental quality buildings. The objective of this article is to study transient hygrothermal behaviour of hemp concrete at whole building level. The physical model is one-dimensional and was implemented into the object-oriented simulation environment SPARK, using the finite difference technique with an implicit scheme. The numerical result showed that the use of hemp concrete wall in buildings can ensure good indoor air quality and energy savings in winter. Besides, the combined effect of moisture buffering with the adequate ventilation strategies increases hemp concrete building performance. Our results also suggest that taking into account the hygrothermal transfer at whole building level with heat and moisture production sources has significant effects on predictions.
Nomenclature 1. Introduction 2. Mathematical models 2.1. Moisture transport in building materials 2.2. Mathematical model for the interface 2.3. Room modelling details 3. Numerical resolution and model validation 3.1. Simulation environment SPARK
3.2. Model validation 4. Properties of hemp concrete 5. Simulation conditions 6. Results and discussions 6.1. Effect of coupled heat and mass transfer in air-conditioned hemp concrete rooms 6.2. Sensitivity analysis 6.2.1. Transport coefficients 6.2.2. Thermal conductivity 6.2.3. Moisture buffering effect 6.3. Ventilation rates effect 6.4. External mortar layers effects 6.5. Comparison between hemp concrete room and cellular concrete room envelopes 6.6. Effect of ventilation strategies 7. Conclusions
The energy savings potential of using dynamic external louvers in an office building
This research is aimed at exploring the influence of external dynamic louvers on the energy consumption of an office building located in Abu Dhabi-UAE. The IES-VR software was used to predict the energy consumption of a representative office module in order to evaluate the overall energy performance of employing external louvers on the south, east and west oriented fa?ades. The use of dynamic fa?ades was compared to another simpler method of using light-sensor controlled light dimmers. The results show that the potential energy savings using light dimming strategy only was 24.4%, 24.45% and 25.19% for the south, east and west oriented fa?ades, respectively. The proposed dynamic louvers system with light dimming strategy achieved energy savings of 34.02%, 28.57% and 30.31% for the south, east and west orientations, respectively. Detailed analysis of the results showed that the fa?ade's optimal static angle was ?20° for the south oriented fa?ade and 20 ° for the east and west oriented fa?ades. Using these fixed optimal angles resulted in slightly lower energy savings than that of the dynamic fa?ades. This would seem to be a good tradeoff between savings in energy running cost and the investment required to install, operate and maintain a dynamic fa?ades system. 写字楼/办公室的新型节能化设计
Energy performance evaluation of a novel evaporative cooling technique 空调/制冷技术/方法/应用框架的能源效益评估
High summer conditioning consumption is becoming a tough and critical issue and consequently there is a need to provide buildings with new technologies for energy saving. Current European and Italian legislation is also working in this direction. We present a preliminary experimental evaluation of the energy performance of a new technology which is capable of canceling conduction gains through walls: “water-evaporative walls”, which are not only able to prevent the entrance of energy fluxes from the exterior to the interior, but also to reduce wall temperatures to below the values found indoors. This solution basically suggests equipping standard ventilated fa?ades with a proper water-evaporative system, which exploits the latent heat of water evaporation, in order to absorb summer cooling loads. From the technological point of view, it requires the insertion of a water spraying system and a proper insulating layer in the ventilated air chamber. The insulation will act not only as a standard insulating material, but also as a porous surface to store water sprayed by the system and then gradually release it when needed for cooling. The experimental analyses showed the effectiveness of this technology, which decreases the overall summer energy load in buildings by canceling conduction loads.
Nomenclature 1. Introduction 2. Related scientific background 3. Functional model of the water-evaporative wall 4. Materials and methods 4.1. General overview 4.2. Preliminary laboratory experiments 4.3. Numerical analyses 4.4. The outdoor experimental campaign 5. Testing campaigns and discussion of their results 5.1. Choice of the absorbing layer 5.2. The spraying system 5.3. Schedule of the experimental campaign 5.4. Results of the experimental campaign
5.5. Statistical analysis 6. Conclusions Acknowledgements
Development and experimental validation solar-assisted multifunctional heat pump
This paper proposes a novel indirect-expansion solar-assisted multifunctional heat pump (IX-SAMHP) which integrates a domestic heat pump with a solar water heater. The IX-SAMHP can not only work in operation modes included in the two household appliances, but also operate in four new energy-saving operation modes for the space cooling, space heating and water heating. All operation modes have functioned successfully and can be switched to each other smoothly on a purpose-built experimental setup. Experiments of the heat pump water heating mode at outdoor air temperatures of 8 ° and 15 ° C C and the solar-assisted space heating mode at indoor air temperatures of 20 ° have been investigated i n C detail. Electric heaters were used to simulate solar radiation intensity in different weather conditions. The experimental results show that the IX-SAMHP can produce hot water with much less electric consumption in cloudy days compared with a solar water heater and can operate in much higher coefficient of performance than a domestic heat pump in cold winter. The IX-SAMHP is especially suitable for the regions abundant in solar radiation where the space heating, space cooling and water heating are required all the year round.
Impact of shading air-cooled condensers on the efficiency of air-conditioning systems
Shading is a technique used to reduce the cooling demand in buildings and save energy. This paper investigates the possibility of reducing the electrical demand and saving energy by shading the condensers of air-conditioning (A/C) equipment. A limiting analysis compares the performance of several A/C systems with ideal shade to those with ideal solar heat gain. The comparison is based on a theoretical model and data from equipment catalogs. The results show that the theoretical increase in the coefficient of performance (COP) due to shading is within 2.5%. Furthermore, this small improvement in ideal efficiency decreases at higher ambient temperatures, when enhancements to efficiency are more needed. A sensitivity analysis shows that the small COP enhancement is not significantly affected by assumed variables. The actual efficiency improvement due to shading is not expected to exceed 1%, and the daily energy savings will be lower. The findings indicate that condenser shading alone, without evapo-transpiration, is not an effective measure to improve efficiency or save energy.
1. Introduction 2. Approach 3. Analysis 4. Results and discussion 5. Conclusions Acknowledgements
Influence of the internal inertia of the building envelope on summertime comfort in buildings with high internal heat loads
The aim of this study was to assess the influence of thermal mass placed on the inner side of the building envelope, described as the dynamic internal areal heat capacity (International Standard ISO 13786), on the summertime thermal comfort in buildings characterised by high internal heat loads.
To that aim, simultaneous monitoring was carried out on rooms with high internal heat loads (school classrooms), varying the internal inertia of the envelope through the introduction of an insulating panel on the interior side. Analytical assessment was performed in order to include different inertia values and combinations of both external and internal heat loads.
The study allowed the threshold values of internal areal heat capacity to be determined with respect to the different periodic transmittance values of the walls, assessed according to the adaptive thermal comfort model described in Standard EN15251.
These values could be adopted in energy saving regulations which, being based on semi-stationary calculation models, tend to consider the performance of building envelopes as analogous even if there is different thermal inertia.
1. Introduction 2. Phases, materials, and methods
2.1. Phases 2.2. Description of the building 2.3. Experimental measuring procedure 2.4. Analytical study 3. Results and discussion 3.1. The data collected: comparison between walls with high and low mass on the inner side 3.2. Calibration of the simulation model by comparing it with the measured data 3.3. Results of parameter variations: effect of inertia with respect to the external and internal loads 3.4. Results of parameter variations: effect of inertia in different climate zones 3.5. Results of parameter variations: effect of thermal inertia with respect to adaptive window-opening 3.6. Some threshold values valid for the assessment of internal inertia in temperate climates 4. Conclusions
Energy performance and consumption for biogas heat pump air conditioner Energy 能源学学报 生物质液体燃料作为热泵空调的能源消耗与效益分析
Biogas engine-driven heat pump air conditioner is a new-style system which includes biogas engine-driven heat pump, primary heat exchanger, second heat exchanger, sprayed room and fans, pumps, etc. In summertime, the air can be reheated by the waste heat water from the biogas engine in the system, while the air can be reheated and humidified by the waste heat water in winter. Reducing or displacing electrical heating requirements can achieve the great opportunity for significant energy savings. This paper, therefore, aims to improve the energy performance of the AC system by using the waste heat from the biogas engine. The mathematic model was used to research the BHPAC. Explicitly, we investigated the influence of various factors including the outdoor air temperature and humidity in summer and winter. Results show that the biogas engine-driven heat pump air conditioner can save more energy than the electrical power heat pump. In summer, the minimum for percentage of primary energy saving for BHPAC is over 25%. With the outdoor air dry-bulb temperature and the relative humidity rises, the saving energy percentage rises. In winter, the minimum for percentage of primary energy saving for BHPAC is 37%. The more the outdoor air relative humidity of the outdoor air decreases,
the more the BHPAC saves energy. It is proved that the system which is a highly actively fully utilizing energy technology has good partial load characteristic and good effects of energy saving.
1. Introduction 2. Description for BHPAC system 3. Discussion for theoretical model 4. Results and discussions 4.1. Energy performance for BHPAC 4.2. Saving energy in BHPAC 5. Conclusions Acknowledgements