Design and transient-based analysis of a power to hydrogen (P2H2) system for an off-grid zero energy building with hydrogen energy storage

In this study, zero energy building (ZEB) with four occupants in the capital and most populated city of Iran as one of the biggest greenhouse gas producers is simulated and designed to reduce Iran's greenhouse emissions. Due to the benefits of hydrogen energy and its usages, it is used as the primary energy storage of this building. Also, the thermal comfort of occupants is evaluated using the Fanger model, and domestic hot water consumption is supplied. Using hydrogen energy as energy storage of an off-grid zero energy building in Iran by considering occupant thermal comfort using the fanger model has been presented for the first time in this study. The contribution of electrolyzer and fuel cell in supplying domestic hot water is shown. For this simulation, Trnsys software is used. Using Trnsys software, the transient performance of mentioned ZEB is evaluated in a year. PV panels are used for supplying electricity consumption of the building. Excess produced electricity is converted to hydrogen and stored in the hydrogen tank when a lack of sunrays exists and electricity is required. An evacuated tube solar collector is used to produce hot water. The produced hot water will be stored in the hot water tank. For supplying the cooling load, hot water fired water-cooled absorption chiller is used. Also, a fan coil with hot water circulation and humidifier are used for heating and humidifying the building. Domestic hot water consumption of the occupants is supplied using stored hot water and rejected heat of fuel cell and the electrolyzer. The thermal comfort of occupants is evaluated using the Fanger model with MATLAB software. Results show that using 64 m² PV panel power consumption of the building is supplied without a power outage, and final hydrogen pressure tank will be higher than its initial and building will be zero energy. Required hot water of the building is provided with 75 m² evacuated tube solar collector. The HVAC system of the building provided thermal comfort during a year. The monthly average of occupant predicted mean vote (PMV) is between ?0.4 and 0.4. Their predicted percentage of dissatisfaction (PPD) is lower than 13%. Also, supplied domestic hot water (DHW) always has a temperature of 50 °C, which is a setpoint temperature of DHW. Finally, it can be concluded that using the building's rooftop area can be transformed to ZEB and reduce a significant amount of greenhouse emissions of Iran. Also, it can be concluded that fuel cell rejected heat, unlike electrolyzer, can significantly contribute to supplying domestic hot water requirements. Rejected heat of electrolyzer for heating domestic water can be ignored.     

Thermal-comfort analysis and simulation for various low-energy cooling-technologies applied to an office building in a subtropical climate

Simulation of buildings’ thermal-performances is necessary to predict comfort of the occupants in buildings and to identify alternate cooling control-systems for achieving better indoor thermal environments. An analysis and prediction of thermal-comfort using DesignBuilder, based on the state-of-the-art building performance simulation software EnergyPlus, is carried out in an air-conditioned multi-storeyed building in the city of Rockhampton in Central Queensland, Australia. Rockhampton is located in a hot humid-region; therefore, indoor thermal-comfort is strongly affected by the outdoor climate. This study evaluates the actual thermal conditions of the Information Technology Division (ITD) building at Central Queensland University during winter and summer seasons and identifies the thermal comfort level of the occupants using low-energy cooling technologies namely, chilled ceiling (CC), economiser usages and pre-cooling. The Fanger comfort-model, Pierce two-node model and KSU two-node model were used to predict thermal performance of the building. A sophisticated building-analysis tool was integrated with the thermal comfort models for determining appropriate cooling-technologies for the occupants to be thermally comfortable while achieving sufficient energy savings. This study compares the predicted mean-vote (PMV) index on a seven-point thermal-sensation scale, calculated using the effective temperature and relative humidity for those cooling techniques. Simulated results show that systems using a chilled ceiling offer the best thermal comfort for the occupants during summer and winter in subtropical climates. The validity of the simulation results was checked with measured values of temperature and humidity for typical days in both summer and winter. The predicted results show a reasonable agreement with the measured data.     

Effects of solar photovoltaic panels on roof heat transfer

Indirect benefits of rooftop photovoltaic (PV) systems for building insulation are quantified through measurements and modeling. Measurements of the thermal conditions throughout a roof profile on a building partially covered by solar photovoltaic (PV) panels were conducted in San Diego, California. Thermal infrared imagery on a clear April day demonstrated that daytime ceiling temperatures under the PV arrays were up to 2.5 K cooler than under the exposed roof. Heat flux modeling showed a significant reduction in daytime roof heat flux under the PV array. At night the conditions reversed and the ceiling under the PV arrays was warmer than for the exposed roof indicating insulating properties of PV. Simulations showed no benefit (but also no disadvantage) of the PV covered roof for the annual heating load, but a 5.9 kWh m⁻² (or 38%) reduction in annual cooling load. The reduced daily variability in rooftop surface temperature under the PV array reduces thermal stresses on the roof and leads to energy savings and/or human comfort benefits especially for rooftop PV on older warehouse buildings.     

Thermal performance of adobe structures with domed roofs and moist internal surfaces

The inside air and the mean radiant temperatures of two buildings, one built of brick having a flat roof and the other built of lightweight adobe and having a domed roof, were estimated through a thermal network analysis. The analysis was repeated for both buildings when their ceilings and inside wall surfaces were kept moist and evaporatively cooled. A design day for a hot, arid region was considered for the analysis. It is shown that the temperature of the moist surfaces is reduced appreciably and the floor and the air temperatures are also reduced by their heat transfer to the moist surfaces. When natural ventilation rate is high, the room air does not become uncomfortably humid.With low mean radiant temperature in the moist buildings, thermal comfort can be maintained for the occupants. The total area and the duration when the surfaces are kept moist, along with the natural ventilation rate, can be controlled by the occupants to provide thermal comfort when it is otherwise uncomfortable. The use of a domed roof with a hole in its crown can ensure high ventilation rates at low wind velocities and in buildings which cannot otherwise be sufficiently vented.     

The bioclimatic design approach to low-energy buildings in the Klang Valley, Malaysia

Formulating passive energy design strategies require an understanding of the climatic influence on buildings and the thermal comfort of their occupants. This paper presents the bioclimatic approach in building design as well as the techniques which are applied to formulate various strategies in order to achieve indoor comfort conditions. The paper deals with the Bioclimatic Chart, the Building Psychrometric Chart, Mahoney Tables and the Control Potential Zones which utilise the thermal neutrality concept. Regional climatic data from the Klang Valley area in Malaysia were utilised in formulating the design strategies. The most appropriate design strategies for hot, humid regions were then deduced. The most preferred strategies found were the use of ventilation, dehumidification and shading. Consequently, a full recommendation for the integral use of these three passive methods are suggested to be used in all buildings in Malaysia.     

城市住宅结构及耗能设备节能潜力的调查分析

于2007年9月对中国七个典型城市住宅的住宅结构、主要耗能设备、生活方式、舒适性及空气品质和能源使用情况等方面进行了详细的问卷调查,本文分析了住宅结构和主要耗能设备两方面的情况,从而得知户型过大,围护结构保温性能差,住户节能意识不高等已成为实现我国建筑节能必须解决的问题。     

BIPV/T技术在新徽派民居中的应用探索

针对新徽派民居中存在的建筑能耗大、热舒适性差及室内空气品质低等问题,探索在保持建筑典型特点的前提下,将太阳能光伏光热建筑一体化（BIPV/T）新技术和新方法在新徽派民居中综合运用。文章主要基于作者团队最新的研究,探讨了兼顾“黛瓦”的光伏瓦技术、兼顾“粉壁”的集热-除甲醛多效墙体技术、兼顾“马头墙”的通风-除菌杀毒多效太阳能烟囱技术、兼顾“青砖”的光伏装饰技术、兼顾“门楼”的平板型PV/T技术、兼顾“花格窗”的碲化镉光伏通风窗技术在新徽派民居中应用的可行性。通过一典型案例设计,基于Energyplus软件对其全年发电量、热水、室温、房间冷热负荷及通风性能进行模拟研究。结果表明,BIPV/T技术可以在发电的同时降低空调负荷、改善室内环境,节能效果显著。     

Roof-top solar energy potential under performance-based building energy codes: The case of Spain

The quantification at regional level of the amount of energy (for thermal uses and for electricity) that can be generated by using solar systems in buildings is hindered by the availability of data for roof area estimation. In this note, we build on an existing geo-referenced method for determining available roof area for solar facilities in Spain to produce a quantitative picture of the likely limits of roof-top solar energy. The installation of solar hot water systems (SHWS) and photovoltaic systems (PV) is considered. After satisfying up to 70% (if possible) of the service hot water demand in every municipality, PV systems are installed in the remaining roof area. Results show that, applying this performance-based criterion, SHWS would contribute up to 1662 ktoe/y of primary energy (or 68.5% of the total thermal-energy demand for service hot water), while PV systems would provide 10 T W h/y of electricity (or 4.0% of the total electricity demand).     

Thermal comfort in apartments in India: Adaptive use of environmental controls and hindrances

Energy used in buildings in India is ever-increasing. About 47% of total energy in Indian residential buildings is used for ventilation controls alone. Comfort temperatures defined in Indian codes are inappropriate (23–26 °C). There are no thermal comfort field studies in residences reported from India. The author conducted a field study in apartments in Hyderabad, in summer and monsoon seasons in 2008. The present paper discusses the occupants’ methods of environmental control, behavioural adaptation and impediments.Due to poor adaptive opportunities, about 60% of occupants were uncomfortable in summer. The comfort range obtained in this study (26.0–32.5 °C), was way above the standard. Fanger’s PMV always overestimated the actual sensation.The occupants adapted through the use of personal environmental controls, clothing, metabolism and many behavioural control actions. Use of fans, air coolers and A/c s increased with temperature, and was impeded by their poor efficacy and noise, occupant’s attitudes and economic affordability. Air-coolers and A/c s were mostly used in top- floors, as the available adaptive opportunities were insufficient. Behavioural adaptation was higher in summer and was limited in higher economic groups always. Subjects frequently exposed to A/c environments, tolerated thermal extremes little, and desired “thermal indulgence”. This study calls for special adaptation methods for top-floor flats.     

Comparative studies of the occupants’ behaviour in a university building during winter and summer time

The paper focuses on the assessment of indoor comfort and energy consumption of a university building in Cyprus, during winter and summer of 2012 and 2013. The aim was to make a comparative study of the occupants’ behaviour and its effects on the building's energy consumption, along with the indoor thermal and visual comfort between the two seasons. American Society of Heating, Refrigerating and Air conditioning Standards are used through a questionnaire campaign and the thermal comfort of occupants is analysed with the indicators of predicted mean vote and predicted percentage dissatisfied. The answers are analysed using SPSS software. The air temperature, the relative humidity and the lighting levels of the building are monitored using temperature, humidity and lux meter tools. The monthly energy consumption cost is also calculated. The results are analysed and comparative studies of the occupants’ behaviour conclude to various patterns of effects on the thermal and visual comfort of the building, as well as on its energy consumption.     

A simple procedure for assessing thermal comfort in passive solar heated buildings

The Fanger thermal comfort equation is linearized and used to develop a procedure for assessing thermal comfort levels in passive solar heated buildings. In order to relate comfort levels in non-uniform environments to uniform conditions, a new thermal index called the “equivalent uniform temperature” is introduced.     

Optimal design of an integrated renewable-storage energy system in a mixed-use building

The rise of mixed-use buildings contributes to the sustainable development of cities but are still met with challenges in energy management due to the lack of energy efficiency and sustainability guidelines. The use of integrated renewable-storage energy systems is a more beneficial solution to this problem over individual solutions; however, most design studies only focused on single-type buildings. Thus, this study aims to optimally design an integrated energy system for mixed-use buildings using HOMER Grid. The objective is to minimize the net present costs, subject to capacity limits, energy balances, and operational constraints. Economic metrics were used to evaluate and compare the proposed system to the varying design cases such as business-as-usual, stand-alone renewable source, and stand-alone energy storage. The case study considered a mixed-use building in a tropical area, with a solar photovoltaic system as the renewable energy source and lithium-ion battery as the energy storage system technology. The results show that the integrated system is the most financially attractive design case. It has a levelized cost of electricity of 0.1384 US$ kWh⁻¹, which is significantly less than the 0.2580 US$ kWh⁻¹ baseline. The system also provides electricity cost savings of 294 698 US$ y⁻¹, excess electricity of 35 746 kWh, and carbon emission reduction of 550 tons annually for a mixed-use building with daily average consumption of 4557-kWh and 763-kW peak demand.     

Energy analysis of façade-integrated photovoltaic systems applied to UAE commercial buildings

Developments in the design and manufacture of photovoltaic cells have recently been a growing concern in the UAE. At present, the embodied energy pay-back time (EPBT) is the criterion used for comparing the viability of such technology against other forms. However, the impact of PV technology on the thermal performance of buildings is not considered at the time of EPBT estimation. If additional energy savings gained over the PV system life are also included, the total EPBT could be shorter. This paper explores the variation of the total energy of building integrated photovoltaic systems (BiPV) as a wall cladding system applied to the UAE commercial sector and shows that the ratio between PV output and saving in energy due to PV panels is within the range of 1:3–1:4. The result indicates that for the southern and western façades in the UAE, the embodied energy pay-back time for photovoltaic system is within the range of 12–13 years. When reductions in operational energy are considered, the pay-back time is reduced to 3.0–3.2 years. This study comes to the conclusion that the reduction in operational energy due to PV panels represents an important factor in the estimation of EPBT.     

Analysis of design approaches to improve the comfort level of a small glazed-envelope building during summer

An architect applies glazing to a building envelope to express an expansiveness and hi-tech quality through transparency. However, in small over-glazed buildings, the glazed envelopes often lead to an inadequate comfort level in summer, when much cooling energy is needed to improve the comfort level and occupants are forced to avoid the use of glazed envelopes. This paper presents the results of comfort survey and measurements on the indoor environment of an architecturally significant small glazed-envelope building that has received many awards for its architectural design quality, and analyzes design approaches to improve the comfort level of its occupants. During the late summer of 2002, the comfort survey was conducted, polling responses from 57 office workers, while simultaneously measuring air/surface temperatures and daylight factors. Numerical simulations were performed to investigate 13 design approaches for the improvement of the comfort level. From the temperature/daylight factor measurements, the indoor air temperature did not maintain the set-point temperature of 24.0 °C even with the operation of the air-conditioning system. When using the roller shades, the intensities of illumination and luminance on each measured desk surface were unevenly distributed from 650 Lux and 51 cd/m² to 6291 Lux and 310 cd/m². From the survey, office workers suffered thermal discomfort and uncomfortable glare from high or non-uniform brightness distributions in the working areas. From the numerical analyses using computer simulations, the double-skin envelopes with the sufficient intermediate space and shading devices were suggested to improve the comfort level.     

Photovoltaic system assessment for a school building

The installation of photovoltaic panels (PVs) on the roof of residential and commercial buildings is getting widespread as these areas stand normally idle and can be used for another purpose without losing an inhabited space. Considering the solar potential of Turkey, a significant amount of electricity generation is possible using current PV technology. For this reason, a two-story detached school building located in ?zmir, Turkey was taken into consideration and monthly as well as annual coverage ratio of an on-grid PV system for its entire energy requirement (including heating, cooling and lighting) was investigated. The PVs were installed on the south face of the school building roof. A heat pump, with a typical coefficient of performance (COP) value of 2.5, was used for supplying required cooling and heating. The heating, cooling and lighting loads were determined on a monthly basis. The average monthly electrical energy generation of the mounted PVs was calculated using a written code in Energy Equation Solver (EES) software. As a result, the monthly as well as yearly electrical energy demand coverage ratio values for the school using the installed PVs were revealed. Since the school building has a large south faced roof, the installation of PVs is very suitable to meet the cumulative electrical energy need of the heat pump and the lighting load. For Case 1, 180 PVs, which supply the entire yearly demand (with a 110% coverage ratio), were taken into consideration, while for Case 2, 265 PVs, which cover 75% of the roof area, were evaluated. The results showed that between November and March, PV electrical energy generation is not sufficient to meet all energy need of the school for both cases. However, significant coverage ratio values were observed for the rest of the year. In a yearly basis, the PV generation exceeded the building demand by 62% for the Case 2. This conclusion points out that the school can meet its yearly electricity need with the considered PV system and can even have an additional financial profit by selling its surplus PV electricity to the grid. Economic and environmental payback time values as well as simple payback time value were also computed for both investigated cases. The results pointed out a simple payback time of 7.9 years for Case 1 and 7.6 years for Case 2. Energy payback time was determined as 5 years for both systems. The greenhouse gas payback time of 2.7 years and 5.9 years was encountered for coal based and natural gas based calculations.     

Thermal comfort temperature range for factory workers in warm humid tropical climates

The ability to operate factory buildings as free running will be very useful in the context of saving energy needed for providing adequate thermal comfort for workers in warm humid tropical climatic conditions. The upper limits of thermally comfortable temperatures were established with comfort surveys carried out in three factory buildings without much ventilation. The surveys were then repeated to determine the effects of ventilation as well. The comfort surveys indicated that workers acclimatized to warm humid climatic condition could tolerate up to 30 °C without much ventilation when engaged in light factory work. This comfort temperature limit can be increased up to 34 °C when indoor air velocities are maintained as high as 0.6 m s⁻¹. It is also shown that these studies validate the earlier predictions of adaptive models for warm humid climates. The ability of workers to tolerate elevated temperatures could be used to highlight some concepts that can be considered in the planning of large-scale industrial parks, so that factories could be operated with minimum energy allocated for providing thermal comfort.     

Design and assessment of a solar energy based integrated system with hydrogen production and storage for sustainable buildings

The current study investigates a holistically developed solar energy system combined with a ground-sourced heat pump system for stand-alone usage to produce power, heat, and cooling along with domestic hot water for residential buildings. An integrated system is proposed where three types of building-integrated photovoltaic plant orientation are considered and integrated with a vertical-oriented ground-sourced heat pump system as well as an anion exchange membrane electrolyser for hydrogen-based energy storage along with proton exchange membrane fuel cells. The ground-sourced heat pump system covers the heating requirements and exploits the available thermal energy under the ground. Hydrogen subsystem enables the integrated system to be used anytime by compensating the peak periods with stored hydrogen via fuel cell and exploiting the excess energy to produce hydrogen via electrolyser. The photovoltaic plant orientations are extensively designed by considering geometries of three different applications, namely, rooftop photovoltaic, building-integrated photovoltaic façade and photovoltaic canopy. The shading and geometrical losses of photovoltaic applications are extensively identified and considered. In addition, the openly available high-rise building load profiles are obtained from the OpenEI network and are modified accordingly to utilize in the current study. The building requirements are considered for 8760 h annually with meteorological data and energy usage characteristics of the selected regions. The integrated system is assessed via thermodynamic-based approach from energy and exergy points of views. In order to increase generality, the proposed building energy system is analyzed for five different cities around the globe. The obtained results show that a 20-floor building with approximately 62,680 m² residential area needs between 550 kWp and 1550 kWp of a photovoltaic plant in five different cities. For Ottawa, Canada, the overall energy and exergy efficiencies are found as 18.76% and 10.49%, respectively, in a typical meteorological year. For the city of Istanbul in Turkey, a 20-floor building is found to be self-sufficient by only using the building's surface area with a 495 kWp BIPV façade and a 90 kWp rooftop PV.     

BIPV: a real-time building performance study for a roof-integrated facility

Building integrated photovoltaic system (BIPV) is a photovoltaic (PV) integration that generates energy and serves as a building envelope. A building element (e.g. roof and wall) is based on its functional performance, which could include structure, durability, maintenance, weathering, thermal insulation, acoustics, and so on. The present paper discusses the suitability of PV as a building element in terms of thermal performance based on a case study of a 5.25?kW_p roof-integrated BIPV system in tropical regions. Performance of PV has been compared with conventional construction materials and various scenarios have been simulated to understand the impact on occupant comfort levels. In the current case study, PV as a roofing material has been shown to cause significant thermal discomfort to the occupants. The study has been based on real-time data monitoring supported by computer-based building simulation model.     

Thermal performance and environmental impact of residential buildings’ heating in Morocco

The seasonal energy requirements and fuel consumption for heating purposes in residential buildings are influenced by the architectural design, construction materials characteristics, meteorological temperature measurements, internal gains and air exchange rate of the building. The goal of this study is to assess the thermal performance and environmental impact of residential buildings’ in Morocco taking into account all these factors and considering two sources of energy: liquefied petroleum gas (LPG) and electricity. The study concludes that the heating energy requirements for the prototype building vary between 2 and 253 kWh/m².year depending on localities, glazing type, glazing area percentage, the internal gains and the air exchange rates. The electricity consumption is 2.6 times greater than that of LPG in terms of kg oil equivalent, and by using LPG instead of electricity the emissions of greenhouse gases can be 3.4 times reduced.     

Optimizing opening dimensions for naturally ventilated buildings

Since naturally ventilated buildings respond to site conditions and microclimate, we cannot establish a “one set of criteria” for every naturally ventilated building. So natural ventilation should be optimized to deal with thermal comfort in passive buildings during summer. A survey of existing tools for natural ventilation simulation shows the dominance of so-called “analysis” tools over “design” tools. In this present work, we will propose a new method to size natural ventilation openings based on inverse calculation, reduction of the number of independent parameters and optimization of occupants thermal comfort.