Simulation analysis of passive solar heated buildings—Preliminary results

Solar gains through windows, walls, modified walls, skylights, clerestory windows, and roof sections provide an opportunity to dramatically reduce the total heating energy requirements of a building. Many such passive solar heating elements are currently available to a designer presenting a large number of possible system designs. A computer simulation analysis has been employed to aid in the selection of components. The results indicate that a performance comparable to that of a conventional active solar heating system should be achievable in an optimized design passive solar heating system. The placement and type of thermal storage is crucial to good performance. Movable insulation of the window increases the performance. When used in conjunction with a conventional heating system, temperature variations in the building can be reduced to those normally experienced.     

Overall and zonal energy end use in an energy conscious office building

An office building of unusual design has been monitored for more than three years. Numerous submeters allow tracking of energy end use. The building was designed to make significant use of daylighting, with some passive solar heating, and an emphasis on night ventilation cooling of thermal mass. The overall building end usages are compared to those of three zones of varying orientation, spatial character, size, and population. Insights about daylight-sensing controls of indirect electric lighting, “task heating,” and night ventilation of mass and air quality are presented.     

Review of passive systems and passive strategies for natural heating and cooling of buildings in Libya

By proper passive design concepts which essentially consist of collection, storage, distribution, and control of thermal energy flow, an energy saving of 2.35% of the world energy output is possible. The basic methods of heating and cooling of buildings are solar radiation, outgoing longwave radiation, water evaporation, and nocturnal radiation cooling. A Trombe-Michel wall consists of a large concrete mass, exposed to sunlight through large, south-facing windows; it is used for heating buildings. Solar absorption cooling and solar dehumidification and evaporative cooling are two approaches that utilize solar energy for the generation of the working fluid and the cooling of dwellings. Outgoing longwave radiation is the most practical way of cooling buildings in desert climates and is effective on roof surfaces, emitting the radiations from the surface of earth to the atmosphere and to outer space. Water evaporation in desert coolers is the usual method of cooling in arid regions. Nocturnal radiation both heats in winter and cools in summer, in suitable climates, and does so with no nonrenewable energy other than a negligible amount required to move the insulation twice a day. The study of 24 different locations in Libya divides the country into regions with distinct passive strategies. The northern region and the Mediterranean coast need passive heating. The buildings in this region should restrict conductive heat flow, prevent infiltration and promote solar heat gains. The southern region, a part of the Sahara desert, needs passive cooling. The buildings in this region need high thermal mass and should promote natural ventilation, restrict solar heat gains and encourage evaporative and radiant cooling. The difficulties encountered in passive solar design are the large exposed area required with suitable orientation for the collection of energy and the large space requirement for the storage of thermal energy. This paper reviews these passive systems and discusses suitable strategies to be adopted for Libya.     

Façade solar collectors

Rational use of energy in buildings leads to a concept of active energy façades such as transparently insulated massive walls, solar thermal or PV façades, advanced glazings for daylighting purposes or double ventilated façades. The paper is concerned with the façade-integrated solar thermal collectors concept for water heating in the existing building stock in the Czech Republic (panel and brick blocks of flats), which are ready for major renovations. Thermal behavior of façade collectors compared with standard roof-located collectors in solar DHW systems was investigated. Façade solar collectors should have an area increased by approximately 30% to achieve the usual 60% solar fraction compared with conventional roof solar collectors with a 45° slope. Further increases in the solar fraction above 70% lead to a required area comparable with roof collectors but with less stagnation periods compared with roof collectors. Application of façade solar collectors affects the indoor comfort in buildings in a reasonable range. Indoor temperatures increase by no more than 1 K in all investigated configurations. Building behavior is not strongly affected by façade collectors when sufficient insulation layers are present.     

THE HIGH-RISE OPPOSING FACADE IN CLEAR SKY CONDITIONS—NOT ALWAYS AN “OBSTRUCTION” TO DAYLIGHT

The opposing building facade is an omnipresent feature for buildings in the urban commercial setting. In clear sky conditions, there are large surfaces of building facades that have the potential of reflecting sunlight incident on them. When the sun is behind a building (so that the solar facade azimuth is greater than 90°), the building opposite potentially acts as a passive daylighting device to it. The work discussed in this paper shows that the performance of this device varies for each floor and for different building densities. Using the ADELINE simulation software, a street with high rise buildings opposite each other is modelled in clear skies, and daylighting is calculated in rooms at different floor levels. Comparisons are made with daylighting of the same rooms without an obstructing building in order to observe the effect of the “obstructing building” to daylighting. Preliminary results indicate that the opposite facade of high rise buildings has the potential to be considered a passive daylighting device in particular contexts. As a passive device, the opposing facade could be given attention by urban designers and planners, as well as by those drawing up building legislation for the urban built environment. It would be desirable and important for users of the built environment, to determine future developments from the point of view of how opposing facades affect daylighting. This approach could have implications for energy efficiency and conservation and would utilise the free resource of solar radiation more effectively.     

Modelling and simulation of elements for solar heating and daylighting

Through the development of highly efficient transparent insulation materials (TIM), new opportunities are appearing in the field of daylighting and passive solar space heating. The simulation program WANDSIM, developed at the Fraunhofer-Institut für Solare Energiesysteme (ISE), models the dynamic performance of three important elements for daylighting and passive solar space heating: window glazing; transparently insulated masonry; transparently insulated glass wall. Selected simulation results of each type are represented and compared under thermal and daylighting aspects. The advantages of the transparently insulated glass wall, a new combined passive space heating and daylighting system, in economy and comfort are verified.     

Evaluation of dichroic material for enhancing light pipe/natural ventilation and daylighting in an integrated system

Integration of natural ventilation and daylighting in a single installation would make both technologies more attractive. One method for the integration is the use of concentric light pipe and ventilation stack. By constructing the light pipe using dichroic materials, the infrared part of the solar radiation is allowed to be transmitted to the stack but the visible light is guided by the light pipe into a room. The heat gain to the interior can be reduced and the thermal stack effect strengthened. Work presented here involved the experimental and computational evaluation of dichroic materials for enhancing both natural stack ventilation and daylighting. The transmittance of a dichroic light pipe was found to be similar to that of a light pipe with a 95% specular reflectance. The infra-red radiation transmitted through the dichroic material into a passive stack was found to enhance the natural ventilation flow by up to 14%. The effect is greater in summer than in winter, which is highly desirable as there is often a lack of driving force for natural stack ventilation in summer.     

The intelligent envelope: The current state of the art

Solar components integrated in the building envelope can provide an important contribution to the utilisation of renewable energy sources for the climatization of the building indoor space, when these components are designed for optimal efficiency and when they are equipped with an appropriate control of their operating parameters.The aim of the R & D in this field is to modify the characteristics of windows and curtain walls in order to improve the thermal and lightning performances and to develop facade-integrated components, performing active functions of indoor climatization and remote space daylighting. The utilisation of this components, operating under automatic control, reduce the energy consumption in winter, increase the reduction of overheating in summer and operate mechanical ventilation for indoor spaces. The main design objective of researchers and producers is to produce reliable, low cost, high efficient industrialised solar components which can be integrated in a wide range of building typologies. The introduction of automation into the operation of movable elements of the passive solar systems could solve several problems.     

A passive solar building for ecological research in Argentina: the first two years experience

An energy-efficient building, featuring energy conservation, passive solar heating, and natural cooling strategies, was designed and built in La Pampa, a province in the temperate semi-arid region of central Argentina. Of compact design, it houses 350 m² of useful floor area in a roughly linear scheme, with the main spaces facing north and ancillary spaces (services) facing south. Solar windows running from above spandrel and up to ceiling height are provided for all the main spaces, and clerestory windows are provided for the solar gain to the south-facing spaces. An integrated sunspace is incorporated into the centre bay of the north facade, providing additional heat to inner spaces as well as functional and visual expansion. In the design stage, a simulation analysis was performed to assess the environmental and energy performance of the alternatives. The main energy features of the resulting building are a volumetric loss coefficient of 1.09 W m⁻³ °C⁻¹, and a predicted solar savings fraction of 70%. The summer cooling strategy includes the passive induction of exterior air into the building through earth-coupled ducts. Cooling by cross-ventilation is made possible during the night, but to preserve the security of the building from sudden storms, this occurs only when the building is occupied. Shading devices protect all windows in summer. Provisional monitoring, started during the 1995 winter period, showed encouraging possibilities of energy savings with adequate comfort conditions, demonstrating the technical feasibility of the scheme.     

Solar passive features in vernacular architecture of North-East India

Energy consumption in the buildings sector is very high and is expected to increase further due to improvements in living standard and increase in the world’s population. Incorporating appropriate solar passive features in climate responsive buildings are good options for energy conservation. This kind of building design integrates the micro-climate and architecture with human thermal comfort conditions and improves the building energy efficiency. From ancient times, people have used solar passive techniques in vernacular architectures throughout the world. However, still there is a lack of understanding, both in qualitative and quantitative aspects of solar passive techniques in vernacular architectures of North-Eastern India. A field study has been carried out to find out the various solar passive features in these naturally ventilated vernacular buildings in different bioclimatic zones of the region. The methodology of this work consists of survey of 150 households (50 houses in each bioclimatic zone) and, interacting with 300 occupants in each zone. The photographic evidences of solar passive features in these buildings are also collected. In this paper, the solar passive features related to building form and orientation, envelope design, shading, use of natural ventilation, internal space arrangements and activities of the habitants are explained for all the climatic zone of the region.     

Advanced bioclimatic architecture for buildings

The town-planning guide for the areas of the high speed rail station of Florence, is finalised at the synthesis of a comprehensive strategic design of the overall objectives bring out by the town-planning scheme of the city. The new bioclimatic strategies realised for the new buildings involved natural lighting systems, roof developed such green areas, passive solar glazed facades, passive natural ventilation, underground design strategies.     

Solar XXI building: Proof of concept or a concept to be proved?

Solar XXI building is a low energy office building where passive and active solar strategies have been applied to reduce the use of energy for heating, cooling and lighting, combining also an extensive photovoltaic façade for electricity production. Solar XXI opened in 2006 and is considered a high efficient building, close to a net zero energy building (NZEB), where the difference between the energy consumed and that produced is 1/10^th of the energy consumed by a Portuguese standard new office building. Its design includes many energy efficiency concepts, such as a high insulated envelope, south sun exposure, windows external shading, photovoltaic panels heat recovery, ground-cooling system, daylighting, stack effect and cross ventilation. The solar gains of the windows and the effectiveness of shading devices were evaluated in order to correlate solar radiation, external and indoor air temperatures. It was also verified that amplitude-dampening of ground-cooled air ranged between 5 and 8 °C, following the trend of the analytical solution for heat diffusion of a cylindrical air/soil heat-exchanger.     

Investigation of thermal performance of a passive solar building with floor radiant heating

This paper presents a theoretical study of an integrated radiant floor heating–direct gain passive solar system. Thermal mass is utilized both for storage of auxiliary heating energy and direct solar gains incident on the floor. An explicit finite difference model is developed to accurately model nonlinear effects and auxiliary heating control. The numerical simulation model is employed to study the performance of a passive solar outdoor test-room with different amounts of thermal mass under various control strategies with constant and sinusoidal room thermostat setpoints. A satisfactory thermal mass is determined based on energy savings, reduction of room temperature swings, and prevention of floor surface overheating. Control of auxiliary heating based on a room effective (operative) temperature is shown to result in improved thermal comfort and higher utilization of passive solar gains as compared to room air temperature control.     

An analysis of daylighting and solar heat for cooling-dominated office buildings

Computer simulation techniques were used to assess the energy performance of a generic commercial office building in Hong Kong. The simulation tool was DOE-2.1E. The thermal and energy performance of daylighting schemes were analysed in terms of the reduction in electric lighting requirement and the cooling penalty due to solar heat. Regression analysis was conducted to correlate the peak electricity demand and annual incremental electricity use with two fenestration variables, namely the solar aperture and the daylighting aperture. Contours of equal annual incremental electricity use were shown to be a function of the solar and daylighting apertures. It is envisaged that these simple charts can be a useful design tool for architects and engineers to assess the relative energy performance of different fenestration designs, particularly during the initial design stage when different building design schemes and concepts are being considered and developed.     

An optimal design analysis of a novel parabolic trough lighting and thermal system

In order to reduce the cost and improve the efficiency of daylighting, an innovative parabolic trough solar lighting and thermal (PTL/T) system is designed and analyzed in this paper. Parabolic trough solar lighting and thermal system uses parabolic trough collector (PTC) controlled by two‐axis solar tracking system as solar collector. The collected sunlight is split by a cold mirror into visible light and infrared. The visible light is reflected by cold mirror, re‐concentrated by a second‐stage Fresnel lens, and then delivered by plastic optical fiber to the buildings for daylighting. The infrared goes through cold mirror, reaches thermal system, and is used for heating generation. The basic structure of PTL/T was outlined and described. The dimension of fiber bundle and parabolic trough was chosen after an optimal analysis. The cost of illuminating unit area was expressed as a function of illumination space dimensions and critical components efficiency. A case study was conducted to get a specific optimized illumination area and PTC area for the first time. The optimized result is to use 8‐m² PTC as collector to illuminate 500‐m² office space. The total solar energy utilization efficiency is 39.4%, with the lighting efficiency of 16.3% and thermal efficiency of 23.1%. The maximum energy savings and simple payback period were calculated for 10 typical cities when applied in residential, commercial, and industrial sectors. The amounts of greenhouse gas‐emission reductions were also calculated. The payback period in Sunbelt region is as low as less than 10 years like in Los Angeles. The results show the proposed PTL/T system is competitive compared with traditional solar energy systems. Copyright © 2016 John Wiley & Sons, Ltd.     

Modeling, design and thermal performance of a BIPV/T system thermally coupled with a ventilated concrete slab in a low energy solar house: Part 1, BIPV/T system and house energy concept

This paper is the first of two papers that describe the modeling, design, and performance assessment based on monitored data of a building-integrated photovoltaic-thermal (BIPV/T) system thermally coupled with a ventilated concrete slab (VCS) in a prefabricated, two-storey detached, low energy solar house. This house, with a design goal of near net-zero annual energy consumption, was constructed in 2007 in Eastman, Québec, Canada - a cold climate area. Several novel solar technologies are integrated into the house and with passive solar design to reach this goal. An air-based open-loop BIPV/T system produces electricity and collects heat simultaneously. Building-integrated thermal mass is utilized both in passive and active forms. Distributed thermal mass in the direct gain area and relatively large south facing triple-glazed windows (about 9% of floor area) are employed to collect and store passive solar gains. An active thermal energy storage system (TES) stores part of the collected thermal energy from the BIPV/T system, thus reducing the energy consumption of the house ground source heat pump heating system. This paper focuses on the BIPV/T system and the integrated energy concept of the house. Monitored data indicate that the BIPV/T system has a typical efficiency of about 20% for thermal energy collection, and the annual space heating energy consumption of the house is about 5% of the national average. A thermal model of the BIPV/T system suitable for preliminary design and control of the airflow is developed and verified with monitored data.     

Highly insulating aerogel glazing for solar energy usage

Granular silica aerogels have been integrated into highly-insulating translucent glazing. This work was performed within the large R&D project ISOTEG pursued by the ZAE Bayern. To avoid settlement of the granules, which often occurred in earlier glazing concepts and even caused destruction of the glazing, the granules were sandwiched between a double skin sheet made of PMMA. The sheet was mounted between two low-e coated glass panes. To optimize the thermal insulation, krypton was used as filling gas. This construction allows to achieve heat transfer coefficients of less than 0.4 W/(m² K). Optimized granular layers provide high solar transmittance of 65% for a thickness of 20 mm. Thus a total solar energy transmittance of 35% for the whole glazing unit is achieved. The glazing has a thickness of less than 50 mm. Such aerogel glazings can be integrated into solar wall systems or used as lightscattering daylighting elements with vanishing energy losses over the heating period even for north facade integration. Optical and thermal properties of the developed granular aerogels as well as the thermal properties of the whole glazing unit are reported.     

Experimental and numerical evaluation of a solar passive cooling system under hot and humid climatic conditions

The thermal performance of a solar passive cooling system (SPCS) under a hot and humid climate is experimentally and numerically evaluated. The experimental data were obtained from two full scale cells, with identical walls, but different roof configurations. One cell has a highly-insulated roof and the other has an SPCS incorporated consisting of a thermal mass (water), which is cooled by evaporation and long wave nocturnal radiation. The study was conducted taking into account the local climatic conditions of Maracaibo, a topical city located in Venezuela. The numerical evaluation was accomplished using the computational code ‘EVITA’ which is based on the finite volume approach with high order bounded treatment of the convective terms. A PISO-like solution algorithm is used to solve the transient form of the continuity, momentum and energy equations. It has been demonstrated experimentally and numerically that under a hot and humid climate, it is possible to keep the indoor temperature below the outdoor temperature, using a passive cooling technique of a roof pond. The numerical results obtained using the model have demonstrated that the computational code used is a suitable cost-efficient alternative for the thermal performance evaluation of SPCS.     

Simulation of façade and envelope design options for a new institutional building

This paper presents a simulation case study of façade and envelope preliminary design options for the new Engineering building of Concordia University in Montreal. A major principle of the analysis was to create a high quality building envelope in order to optimally control solar gains, reduce heating and cooling energy demand and reduce electricity consumption for lighting, while at the same time maintain a comfortable and pleasant indoor environment. The stated approach of the design team was to aim for an energy-efficient building, employing innovative technologies and integrating concepts such as daylighting and natural ventilation. Detailed energy simulations were therefore performed from the early design stage, in order to present recommendations on the choice of façade, glazings, shading devices, lighting control options, and natural ventilation. Integrated thermal studies, a daylighting analysis and the impact of the above on HVAC system sizing were considered. Simulation results showed that, using an optimum combination of glazings, shading devices and controllable electric lighting systems, the energy savings in perimeter spaces can be substantial. Perimeter heating could be eliminated if a high performance envelope is used. The building is currently being commissioned.