Performance evaluation of a passive solar building in Western Himalayas

Under the Passive Solar Building Programme, more than 100 buildings have been constructed in the high altitude region of the Indian State of Himachal Pradesh. A policy decision has been taken by the State that all government/semi-government buildings are to be designed and constructed as per passive solar housing technology. The evaluation studies of some of these buildings have been carried out by our group. In the present study, the thermal performance of a passive solar bank building at Shimla, has been evaluated. This solar building incorporates a heat-collecting wall and a roof-top solar air heater with an electric heating backup, sunspaces and double-glazed windows. The monitoring of the building shows that the solar passive features in the building results in comfortable living conditions. The study shows that the high cost central electric/gas/wood-fired heating systems can be replaced by a low cost solar heating system with backup heaters. This will result not only in reducing higher installation costs of these systems but also the annual running and maintenance costs. It is shown that the solar passive features save electricity required for space heating and reduce the heat losses in the building by about 35%. The strategy to be followed for the propagation of passive solar technology on large scale in this Himalayan State or in any other cold hilly region is also presented.     

Computational methods for passive solar simulation

The use of network models and a range of computational methods for the simulation of passive solar buildings are described, compared, and assessed. The following methods are considered: (i) Steadystate methods; (ii) Finite difference methods, explicit and implicit; (iii) Modal or analytic spectral methods; (iv) Fourier series methods. Methods (ii) to (iv) are compared by applying them to a series of numerical examples using the same data. In particular, the effect of network nodes with small thermal mass and the effect of increasing network size are considered. With explicit methods it is shown that it is important to approximate building components with small thermal mass by zero-mass nodes. Generally, the modal and implicit finite difference methods are the most efficient.     

A passive solar water heating system for vineyard frost protection

The threat of frost during spring time (after ‘bud burst’) is an ever present danger to the vineyard owner. To minimise the risk, in addition to good site selection and vineyard management, a number of active frost protection systems are available. Most active methods of frost protection are costly in monetary terms and can also have a detrimental effect on the environment. This work presents the design and performance of a passive solar water heating quilt system under real vineyard operating conditions. Two vineyard sites were selected, and the solar water heating quilt design was evaluated over a three-month period. Detailed measurements of the temperature below and above the soil surface, levels of incident solar radiation and the wind direction and speed were recorded. Field study results indicate that the quilts can improve the solar collection and heat retention of the soil, resulting in increased temperatures during frost events of up to 1 °C in air space immediately adjacent to the solar quilts when compared to conditions off the protected area. In addition, the time period during which the frost remains a danger to the vine is also reduced. When heat collection, storage and extraction rates are investigated, simplified calculations indicate that the solar quilt can improve collection by 38.5% over bare soil, resulting in the release of 32% more heat. Extrapolated to vineyard coverage, this could result in an extra 3500 MJ of heat per hectare per (typical frost event condition) day.     

Thermal performance evaluation of active and passive water heat-storage schemes for solar energy applications

Because of easy availability and low cost, water is commonly used as a sensible heat-storage medium in solar energy applications. In this investigation two schemes of water thermal storage (active and passive) were designed and constructed from readily available materials. A dynamic computer model was developed to predict the thermal performance of the water thermal-storage systems under various charging and discharging conditions. Experimental tests were also conducted. The simulated results and measured data compared favourably, and these results showed that the water thermal-storage systems responded well to step and fluctuating input temperature changes. The water thermal storage may be satisfactorily used in varied solar energy applications where energy storage is necessary.     

The passive solar heated school in Wallasey. V. Energy requirements for A passive school building

The near-south-facing glazed wall of the Wallasey School admits large solar gains in sunny weather, sufficient to meet in full the heat need in cold weather. It permits large heat losses, however, and during dull weather, and during the long winter nights there is little or no compensating solar gain. The net effect of such glazing over a season might be either to save, or to waste energy as compared with a windowless building, according to the sunniness and coldness of the climate and the window characteristics. To examine the action of the glazing, use was made of 50 years of daily mean ambient temperature, and contemporary sunshine hours, in conjunction with the solar gain factor for the translucent and pinboarded areas of the solar wall, and for certain values of design temperature and ventilation rate. It is concluded that such glazing leads to modest savings, of around 5 to 10 W/m² daily average. Most of the saving appears to be achievable by around 30 per cent glazing; further glazed area tends to supply unwanted solar gain in sunny periods while increasing the losses in sunless conditions. The annual electricity consumptions are noted for the 20 year life of the building. Their costs suggest that the building has been economical to heat.     

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.     

Design tools for bio-climatic and passive solar buildings

Tools for design and evaluation of bio-climatic and passive solar buildings are presented. The paper discusses different kinds of tools for the various design stages. Accordingly, existing tools can be classified as either generative or evaluative tools. Generative design tools aid in the definition of the proper geometry and solution. Therefore, they are the best tools for the early design stages. Evaluative tools study in detail the performance of a given design. Hence, they fit advanced design stages. Moreover, evaluative tools may be used to derive design guidelines that are required for the early design stages. These guidelines can be embedded in expert systems as a knowledge base. Examples of such tools are presented. Emphasis is put on the early design stages.     

A sequential filter used for parameter estimation in a passive solar system

The use of a sequential least squares filter for estimating passive solar system parameters is presented as it applies to certain types of systems. The method given is used to identify parameters in a particular existing system, and the results are given. A discussion is also included on a comparison of various sampling rates used by the filter, with a view toward selecting a “reasonable” sampling rate.     

A wind-mixed layer model for solar ponds

A computer model is described which may be used for predicting transient salinity and temperature profiles in a salt gradient solar pond. It is intended for use in modeling large surface area ponds where wind-mixing would be expected to play an important part in the dynamics of the upper layer. The formulation predicts the depth of the upper convecting zone using a mixed-layer model which incorporates the wind-mixing algorithm described by Bloss and Harleman [1,2]. This is in contrast to earlier solar pond models which have generally assumed a constant value for this layer depth. Results have been obtained for a number of 1-yr simulations of a large hypothetical pond in Richmond, Virginia, and these have been used in testing the sensitivity of the model to several of the input parameters, including the radiation term and the form of the wind-mixing algorithm. The model output is also compared with field data from an operating solar pond and good agreement is found. Results have indicated that some measures will have to be taken to counteract the mixing action due to wind stress, if the upper mixed layer depth is to be maintained at an acceptable level. The model is expected to be useful in large-scale pond design.     

被动式太阳房热工计算设计软件发展

太阳房是太阳能热利用的一个重要领域,它的推广有利于节约常规能源,减少环境污染,改善生态环境,和谐人与自然的关系,具有重要的社会、经济效益。甘肃省科学院自然能源研究所研制的《被动式太阳能采暖房（动态）热工计算软件》可用来计算国内外最常用的直接受益式、集热墙式（含集热蓄热墙和对流环路式集热墙）、附加阳光间式三种典型太阳房及其组合型太阳房的动态热工性能,预测其在不同地点、不同时间及不同气象条件下的逐时室温;计算房间在控温运行时所需的逐时辅助热量;优选建筑热工设计参数及设计方案,提高太阳房和节能房的适用性和经济…     

A simplified nonlinear model for solar collectors

An explicit nonlinear model is presented which predicts the performance of a solar collector and includes the effects of radiative losses. This model was obtained from the empirical correlation of simulation data from a total of 3969 separate computer simulations which included 50 different collector designs and a wide range of operating conditions. The detailed computer model, which was used to generate the simulation data, included effects such as radiative losses, axial conduction, edge losses and temperature dependent fluid properties. Results are presented which show that the proposed nonlinear model agrees with the detailed computer simulation much better than does the linear Hottel-Whillier-Bliss model.     

Massive storage walls as passive solar heating elements: An analytic model

A simple analytic method for the prediction of the long-term thermal performance of passively-heated solar houses is presented. The treatment includes a new coarse method for “energy bookkeeping” and the use of a distribution function which represents the frequency of occurrence of different values of the solar load ratio. Due to its generality, this formalism is applicable to any passive heating element. As specific examples, the cases of direct gain and water wall houses are treated in detail. Relative to the parameterization of computer simulation results, this method offers the user a design tool that can be used to predict, in closed form, the thermal effect on the house of different building and climatic parameters and is not restricted to a “reference” building. Agreement with published numerical simulation results in satisfactory. The presentation is divided into two separate papers: a users guide for the reader who may not be interested in the details of derivation and validation, and the present paper, in which the theory is presented in detail.     

Experimental and numerical model of wall like solar heat discharge passive system

The present work raises the use of solar energy as an aid for air conditioning by means of architectural envelope parts such as walls, basically as heat discharge systems. Using a thermal balance applied to these systems, an analytic model was formulated to simulate its behavior and to consider the time variation of the environmental temperature, solar radiation, heat storage in the wall and the temperature of the room to be ventilated. The analytical results were compared against experimental data, creating an experimentally validated model that gives confidence on the accuracy and trustworthiness of the analytic proposal. Six tests were carried out in the experimental model. In four of them, the heat flux simulation was performed with electrical resistors; in the other two, solar radiation was directly employed. The results show that the thermal performance of the system can be appropriately determined and described by the analytical model, within a small margin of error. The proposed analytic model can calculate the behavior of a heat discharge system in walls by simply knowing the dimensions of the prototype and the environmental conditions.     

Myths in passive solar design

For years passive solar design principles have been perpetuated without being reexamined or questioned regarding their relevance in the context of new materials and constructions. Rarely does an architect get quantitative feedback on system or concept performance after the building is built. The result has been the perpetuation of beliefs among conference papers, text books and popular articles, all too often based only on belief. In this paper examples of premises which likely deserve to be kept passive rather than acted on are challenged. Designers are encouraged to ask three questions when applying a commonly held rule or assumption: Does it address the right issue? Does it apply, given the properties of new components and materials? If the premise is violated, how badly is comfort or the energy balance affected? Examples taken from monitoring and sensitivity studies illustrate the importance of asking “stupid” questions.     

Equitable performance comparison and economic evaluation of active and passive solar energy systems

An evaluation of active and passive solar energy systems is made which assigns to both systems an equal energy demand. Active systems with baseline energy requirements equivalent to those of passive systems are identified by making a careful accounting of what passive solar energy properly belongs in the building load. This analysis allows an equitable economic comparison between the two alternative design solutions to the problem of maximizing life cycle savings for a system which supplies heat to a structure with specified floor area and heating load per unit floor area.     

Reverse ray-tracing model for the performance evaluation of stationary solar concentrators

The yearly energy collection efficiency of stationary solar concentrators can be evaluated using reverse ray-tracing, and a solar radiation model. In reverse ray-tracing, rays originating at the receiver of the concentrator are traced towards the surrounding hemisphere. The method allows for the evaluation of the absolute energy collection: new concentrators may be optimized for location and tilt, requiring one-time ray-tracing. The tilt of existing concentrators is optimized. Only possible solar incidence is considered by our model. The method is fast and realistic; it can be modified for concentrators in tilt operation.     

A flat-plate calorimeter for concentrated solar flux evaluation

In order to evaluate the energy arriving at the focus of a solar concentrator named DEFRAC (from its Spanish acronym, Device for the Study of Concentrated Radiative Fluxes) a calorimetric study was carried out. We studied the heat transfer in the receiving plate of a calorimeter; the distribution of temperatures during the transient and steady states were obtained both theoretically and experimentally. We show that the calorimeter is close to ambient temperature which validates the use of the cold water calorimetry technique. Since the heat losses are reduced it is possible to increase the exactitude and precision during the thermal evaluation. Based on an energy balance, the solar energy absorbed by the receiver of the DEFRAC and the global heat losses to the environment are quantified.     

被动式太阳能建筑设计

一前言 一般在利用太阳能的建筑中,太阳能利用分为两种方式:一种是被动式太阳能,另一种是主动式太阳能.所谓被动式太阳能,是指利用太阳能提供室内供热,而无需其他机械装置提供能源,被动式太阳能系统依靠传导、对流和辐射等自然热转换的过程,实现对太阳能的收集、储藏、分配和控制.而主动式太阳能与被动式太阳能正好相反,它是利用机械装置来收集、储藏、分配和控制太阳能热量的方法,如太阳能光电板式发电机、太阳能热水器等.对于被动式太阳能系统来说,它需要两方面的元素构成:一是利用朝阳方向的透明材料(玻璃或塑料等)或是深色材料来收集太阳能,二是收集、储存和分配太阳能热量的蓄热体能够最大限度的接收太阳能.     

The evaluation of heat capacity and choice of materials for short-term storage of diurnal solar heat surplus in passive solar heating systems

The results of numerical studies aimed to evaluate the heat capacity of short-term phase change heat accumulators applied in passive solar heating systems (PSHS) with a three-layer energy active translucent enclosure (TE) are presented. An example is given of calculation of specific (per unit of TE surface area) weight of heat accumulator using dimethyl sulfoxide, (СН₃)₂SO, with melting temperature 18.6°C and latent heat of phase transition 173 kJ/kg, as the heat storage agent.