Method for modelling space conditioning aggregated daily load curves: Application to a university building

Physically based load modelling methodologies have been widely developed and used because of their ability to predict the energy load dynamic response. Most building energy programs predict energy consumption and energy system performance through a whole building energy simulation as well as a global analysis of building thermal processes and heating, ventilation and air-conditioning (HVAC) system performance. A different approach is presented in this paper by introducing a new method for modelling the daily load profile of a group of air-conditioning systems. This method is based on the simulation of a single HVAC system, a set of end-use electrical measurements, and a detailed walk-through and energy audit. The basic methodology allows deducing the aggregated load of a group of space conditioning devices by the addition of the daily simulation of each individual physical system. As an application, the space conditioning daily demand curve of a university building is studied and results are presented.     

Utilization of wind energy in space heating and cooling with hybrid HVAC systems and heat pumps

Approximately one-third of the primary energy resources are consumed in space heating, cooling, and air-conditioning with a very low exergetic efficiency. The depleting nature of primary energy resources, negative environmental impact of fossil fuels and low exergetic efficiencies obtained in conventional space heating and cooling are the main incentives for developing alternative heating, ventilating, and air-conditioning (HVAC) techniques which can employ low density and interrupted energy sources. In this respect, in spite of difficulties primarily encountered in coupling wind energy with conventional space heating and cooling equipment, wind energy seems to be an exciting alternative provided that synectic combinations are pursued and applied. In this paper, a new wind turbine coupled hybrid HVAC system is presented, which consists of an optimum combination of convective and radiant heating and cooling systems with in-space thermal energy storage. A design case for a single family home is presented. In this study a 6 kW(e) wind turbine drives a ground source heat pump (GSHP) which is coupled to a hybrid HVAC system to satisfy the thermal loads of a 100 m² home. In this example, sensible heating and cooling loads are satisfied by the high mass radiant floor which matches the daily peak demand and the available peak wind energy. Latent heating and cooling loads, along with ventilation requirements are satisfied by a forced-air system. Variable radiant and convective split type of control is implemented, and both systems are served by the same GSHP which also satisfies the domestic hot water (DHW) demand.     

小型太阳能复合供热系统的应用与设计

结合欧洲太阳能应用的经验及国内的实际情况,介绍了小型太阳能复合供热系统(包括生活热水和供暖)常用形式的流程和特点。介绍了集热器、蓄热水箱、辅助热源的设计。     

Simulation of hybrid ground-coupled heat pump with domestic hot water heating systems using HVACSIM+

A hybrid ground-coupled heat pump (HGCHP) with domestic hot water (DHW) supply system has been proposed in this paper for space cooling/heating and DHW supply for residential buildings in hot-climate areas. A simulation model for this hybrid system is established within the HVACSIM+ environment. A sample system, applied for a small residential apartment located in Hong Kong, is hourly simulated in a typical meteorological year. The conventional GCHP system and an electric heater for DHW supply are also modeled and simulated on an hourly basis within the HVACSIM+ for comparison purpose. The results obtained from this case study show that the HGCHP system can effectively alleviate the imbalanced loads of the ground heat exchanger (GHE) and can offer almost 95% DHW demand. The energy saving for DHW heating is about 70% compared with an electric heater. This proposed scheme, i.e. the HGCHP with DHW supply, is suitable to residential buildings in hot-climate areas, such as in Hong Kong.     

Minimisation of energy consumption of a bioclimatic building based on heat balance study and stand-alone PV system sizing using LLP

Bioclimatic buildings are very comfortable habitats for significant savings in the consumption of daily energy. They help to protect the environment by preventing the emission of dust and pollutant gases into the atmosphere. In this paper, a sizing method is proposed that ensures a suitable internal climate with adequate comfort. First, a simple algorithm is used for the estimation of the heat balance and performance of a typical bioclimatic house in the region of Laghouat, Algeria. Second, the load demand is assured using an optimal stand-alone photovoltaic system sizing method based on the loss of load probability method (LLP) while ensuring the minimum cost of the system. The results show the effectiveness of the proposed method that can be used to develop an optimal building sizing project in all its dimensions, in particular to reduce the overall budget of the operation.     

1st Environmental conference of Thessaly region, 8–10 September 2012, Hotel Skiathos Palace,Koukounaries, Skiathos Island,Greece

This study was conducted with the aim to assess the potential performance of a photovoltaic thermal mechanical ventilation heat recovery (PV/T MVHR) system. The device is currently considered for the application to the Z-en house project undertaken by Scottish homebuilder. The house’s whole energy demand was calibrated based on the UK Government’s standard assessment procedure for energy rating of dwellings, while the PV/T performance was estimated using an ‘EESLISM’ energy and environmental design simulation tool developed by Kogakuin University. This study concluded that PV generates heat, which makes the fresh air running under the PV roof 10–15?°C warmer than the outside temperature even during the Scottish winter and this warm air extracted from roof-integrated PV modules can be used to help reduce the domestic space-heating demand. Thus, the building-integrated PV/T MVHR system was considered as one of the effective means to assist the net zero energy operation of housing in cool and cold climates, whose dominant domestic energy comsumption derives from space heating.     

复合式太阳能供热系统的应用与设计

太阳能供热采暖是一项新的节能技术。文中介绍了一种典型的复合式太阳能供热系统(包括采暖和生活热水)流程和特点,然后分析了集热器、蓄热水箱、辅助热源设计方法及选型要点。     

Long term operation of a solar assisted ground coupled heat pump system for space heating and domestic hot water

This paper introduces a solar-assisted ground-coupled heat pump (SAGCHP) system with heat storage for space heating and domestic hot water (DHW) supply. The simulation results of the system's detailed operating performance are presented. The optimization of the system design is carried out by the TRNSYS and a numerical simulation is performed for continuous operation of 20 years under the meteorological conditions of Beijing. Different control strategies are considered and the operational characteristics of each working mode are studied. The simulating results show that the long term yearly average space heating efficiency is improved by 26.3% compared to a traditional ground coupled heat pump (GCHP) system because the solar thermal collecting system is used to elevate the thermal energy in the soil and to provide direct space heating with heat storage. At the same time, the underground heat load imbalance problem for a heating load dominated GCHP is solved by soil recharging during non-heating periods, while extra solar energy is utilized to supply DHW. The flexibility and high efficiency of the SAGCHP system could offer an alternative for space heating and DHW supply by heat pump technology and solar energy in cold winters of northern China.     

Energy load predictions for buildings based on a total demand perspective

The outline of this work was to develop models for single family buildings, based on a total energy demand perspective, i.e., building-climate-inhabitants. The building-climate part was included by using a commercial dynamic energy simulation software. Whereas the influence from the inhabitants was implemented in terms of a predicted load for domestic equipment and hot water preparation, based on a reference building. The estimations were processed with neural network techniques. All models were based on access to measured diurnal data from a limited time period, ranging from 10 to 35 days. The annual energy predictions were found to be improved, compared to models based on only a building-climate perspective, when the domestic load was included. For periods with a small heating demand, i.e., May-September, the average accuracy was 7% and 4% for the heating and total energy load, respectively, whereas for the rest of the year the accuracy was on average 3% for both heating and total energy load.     

A modelling study for the integration of a PEMFC microCHP in domestic building services design

Fuel cell based micro-combined heat and power( CHP) units used for domestic applications can provide significant cost and environmental benefits for end users and contribute to the UK 's 2050 emissions target by reducing primary energy consumption in dwellings. Lately there has been increased interest in the development of systematic methods for the design of such systems and their smoother integration with domestic building services. Several models in the literature,whether they use a simulation or an optimisation approach,ignore the dwelling side of the system and optimise the efficiency or delivered power of the unit. However the design of the building services is linked to the choice of heating plant and its characteristics. Adding the dwelling's energy demand and temperature constraints in a model canproduce more general results that can optimise the whole system,not only the micro-CHP unit. The fuel cell has various heat streams that can be harvested to satisfy heat demand in a dwelling and the design can vary depending on the proportion of heat needed from each heat stream to serve the energy demand. A mixed integer non-linear programming model( M INLP) that can handle multiple heat sources and demands is presented in this paper.The methodology utilises a process systems engineering approach. The model can provide a design that integrates the temperature and water flowconstraints of a dwelling's heating system with the heat streams within the fuel cell processes while optimising total CO2 emissions. The model is demonstrated through different case studies that attempt to capture the variability of the housing stock. The predicted CO2 emissions reduction compared to a conventionally designed building vary from 27%to 30%and the optimum capacity of the fuel cell ranges between 1. 9 kW and3. 6 kW. This research represents a significant step towards an integrated fuel cell micro-CHP and dwelling design.     

Application of latent heat thermal energy storage in buildings: State-of-the-art and outlook

Latent heat thermal energy storage (LHTES) is becoming more and more attractive for space heating and cooling of buildings. The application of LHTES in buildings has the following advantages: (1) the ability to narrow the gap between the peak and off-peak loads of electricity demand; (2) the ability to save operative fees by shifting the electrical consumption from peak periods to off-peak periods since the cost of electricity at night is 1/3–1/5 of that during the day; (3) the ability to utilize solar energy continuously, storing solar energy during the day, and releasing it at night, particularly for space heating in winter by reducing diurnal temperature fluctuation thus improving the degree of thermal comfort; (4) the ability to store the natural cooling by ventilation at night in summer and to release it to decrease the room temperature during the day, thus reducing the cooling load of air conditioning. This paper investigates previous work on thermal energy storage by incorporating phase change materials (PCMs) in the building envelope. The basic principle, candidate PCMs and their thermophysical properties, incorporation methods, thermal analyses of the use of PCMs in walls, floor, ceiling and window etc. and heat transfer enhancement are discussed. We show that with suitable PCMs and a suitable incorporation method with building material, LHTES can be economically efficient for heating and cooling buildings. However, several problems need to be tackled before LHTES can reliably and practically be applied. We conclude with some suggestions for future work.     

Energy-efficient terrace houses in Sweden: Simulations and measurements

Reducing energy use in buildings is essential to decrease the environmental impact. Outside Gothenburg in Sweden, 20 terrace houses were built according to the passive house standard and completed in 2001. The goal was to show that it is possible to build passive houses in a Scandinavian climate with very low energy use and to normal costs. The houses are the result of a project including research, design, construction, monitoring and evaluation. The passive house standard means that the space heating peak load should not exceed 10 W/m² living area in order to use supply air heating. This requires low transmission and ventilation losses and the building envelope is therefore highly insulated and very airtight. A mechanical ventilation system with approximately 80% heat recovery is used. The electric resistance heating in the supply air is 900 W per living unit. Solar collectors on the roof provide 40% of the energy needed for the domestic hot water. The monitored delivered energy demand is 68 kWh/m² a. Energy simulations show that main differences between predicted and monitored energy performance concern the household electricity and the space heating demand. Total delivered energy is approximately 40% compared with normal standard in Sweden.     

长江流域居住建筑不同供暖模式下的负荷特性分析

通过分析长江流域冬季供暖特点,采用建筑环境动态负荷分析软件DeST-h对该地区典型城市重庆居住建筑在连续供暖和间歇供暖2种供暖模式下的冬季逐时热负荷进行了计算,分析了2种供暖模式下的负荷分布特性。连续供暖的热负荷总体水平较低,波动较小,且与室外空气温度呈负相关,而间歇供暖的热负荷波动较大,具体表现为开始阶段热负荷较大,而后迅速降低并稳定。据此进一步分析了该负荷特性对长江流域居住建筑的空气源热泵机组选型及运行调节的影响。分析得出:按照夏季供冷工况进行设备选型,机组名义工况下的制热量能满足连续供暖的最大热负荷需求和间歇供暖稳定阶段的热负荷需求;连续供暖条件下部分负荷率主要分布在25%~75%之间,机组的运行调节可采用定容量压缩机台数控制方式;间歇供暖条件下部分负荷率主要分布在50%~100%之间,建议采用变容量调节方式。     

A user-centric space heating energy management framework for multi-family residential facilities based on occupant pattern prediction modeling

Space heating is the highest energy consumer in the operation of residential facilities in cold regions. Energy saving measures for efficient space heating operation are thus of paramount importance in efforts to reduce energy consumption in buildings. For effective functioning of space heating systems, efficient facility management coupled with relevant occupant behaviour information is necessary. However, current practice in space heating control is event-driven rather than user-centric, and in most cases relevant occupant information is not incorporated into space heating energy management strategies. This causes system inefficiency during the occupancy phase. For multi-family residential facilities, integrating occupant information within space heating energy management strategies poses several challenges; unlike with commercial facilities, in multi-family facilities occupant behavior does not follow any fixed activity-schedule pattern. In this study, a framework is developed for extracting relevant information about the uncertainties pertaining to occupant patterns (i.e., demand load) in multi-family residential facilities by identifying the factors affecting space heating energy consumption. This is achieved using sensor-based data monitoring during the occupancy phase. Based on the analysis of the monitoring data, a structure is defined for developing an occupant pattern prediction model that can be integrated with energy management strategies to reduce energy usage in multi-family residential facilities. To demonstrate the developed framework, a multi-family residential building in Fort McMurray, Canada, is chosen as a case study. This paper shows that integrating the developed occupant pattern prediction model within space heating energy management strategies can assist facility managers to achieve space heating energy savings in multi-family residential facilities.     

Zur Genauigkeit von Heizwärme‐Bilanzverfahren. Einführung eines Heizperiodenbilanzverfahrens mit analytischen Klimafunktionen

Precision of heating energy balance methods. Introduction of annual heating energy balance with analytical climate function. By smoothing the outdoor temperature and global radiation intensities to cosine functions it is possible to obtain the length of the heating period, the mean outdoor temperature and the radiation during the heating period as functions of the base temperatures. Neglecting the time difference between radiation intensities and outdoor temperature it is also possible to represent the mean base temperature as a simple function of building parameters and outdoor climate values. With these functions the accuracy of the monthly heating energy balance method and of the annual heating energy balance method according to the European Standard EN 832 can be tested for very low heat gains. Comparisons show, that the monthly heating energy balance method and even more the annual heating energy balance method according to EN 832 tend to underestimate the annual heating energy demand. With short heating periods, this tendency is stronger. At heating periods shorter than 4 months the qualification of the monthly heating energy balance method as reference method seems to be questionable. The analytic heating energy balance method, a simple completely analytical method using energy balance over the heating period for different energetic standards is introduced. The accuracy in the calculation of annual heating energy demand is checked in comparisons with the monthly heating energy balance method. For heating periods longer than 5 months the annual heating energy demand calculated with this method differs less than 2 percent from the equivalent value of the monthly heating energy balance method in most cases. The annual method of energy balance over the heating period introduced by Loga for buildings with different energetic standards is analysed and compared with the analytic balance method.     

Feedback simulation of duct design for alkali exhaust system in a semiconductor factory

Duct design for an exhaust system must not only considers the demand of volume flow rate, but also takes into consideration a number of issues including system pressure balance, velocity constraint, space limitation and energy conservation. Conventional duct design methods either fail to achieve pressure equilibrium or offer poor control of flow velocity or duct diameter. A new design method that comprises two major calculation procedures: system sizing and rating is proposed. Duct system sizing problem is solved by the initial design from the conventional design methods. Feedback simulation provides the rating procedure for system actual operating process. An example is presented in this study to understand the characteristics of the proposed method. It demonstrates that the new duct design method contains a simple computation procedure and considers the pressure equilibrium under certain limits on space or flow velocity. It also provides the energy conservation strategies for the actual operating process during the design stage.     

Thermal and economic windows design for different climate zones

Window design, especially glazing choices, is a critical factor for determining the effectiveness of passive solar design. Windows are like a knife has two side; one is useful and the other is harmful. In this paper the effects of windows’ U-value, window orientation and windows size on annual heating and cooling energy demand is studied considering the both energy and investment costs. The study has been performed for three different climate zones; Amman, Aqaba and Berlin. Four types of windows have been studied; single glazed, double glazed L, double glazed H and triple glazed.The results show that heating load is highly sensitive to windows size and type as compared with cooling load. Also, it is shown that with a well-optimized glazed window energy saving can be reached up to 21%, 20% and 24% for Amman, Aqaba and Berlin, respectively.     

Energy saving potential of an indirect evaporative cooler as a pre-cooling unit for mechanical cooling systems in Iran

The performance of indirect evaporative cooling system (IEC) to pre-cool air for a conventional mechanical cooling system has been investigated for four cities of Iran. For this purpose, a combined experimental setup consisting of an IEC unit followed by a packaged unit air conditioner (PUA) was designed, constructed and tested. Two air simulators were designed and used to simulate indoor heating load and outdoor design conditions. Using of experimental data and an appropriate analytical method, the performance and energy reduction capability of combined system has been evaluated through the cooling season. The results indicate IEC can reduce cooling load up to 75% during cooling seasons. Also, 55% reduction in electrical energy consumption of PUA can be obtained.     

解放军总医院海南分院医疗区生活热水系统设计及节能分析

医疗建筑生活热水用量比较大,要求高;不同于住宅、宾馆等其他公共建筑,生活热水系统所消耗的能量较大,如何合理设计医疗建筑生活热水系统、提高医疗建筑生活热水系统的可再生能源利用率?解放军总医院海南分院的生活热水利用太阳能和空气源热泵辅助加热直接供应,经过半年多实际运行的检验,节能效果很好。论文结合该工程,介绍了热水系统的设计,并简要分析节能情况。     

Organismes members du CIB La Nouvelle‐Zélande

Introducing a feature on the controlled storage and release of energy; especially captured solar energy; this article describes a design for a curtain wall which will provide seasonal heating and cooling in a passive solar building. It is being tested at the EEC Commission's Joint Research Centre at Ispra, Northern Italy: The principles and techniques employed in this phase-change concept produce a module which can collect, store and release solar heat at around 20 °C with forced air circulation. It is dimensioned to meet the daily energy demand for air conditioning during the summer and most of the heating demand in the winter.