Numerical Study of Classical and Composite Solar Walls by TRNSYS

The laboratory LAMTI has worked for several years on the study and the optimization of the thermal performances of passive solar walls like solar Trombe wall. These components of the buildings envelope have very complex behaviour because they are the seat of various coupled heat transfers modes and are subjected to the random variations of the meteorological parameters. Using the finite difference method （FDM） and starting from experimental results recorded during several years, a simulation model was developed and validated concerning the ＂composite＂ Trombe wall. In order to make this work more accessible to the community of the heat engineers, it appears interesting to build a simulation model which can be integrated into the library of elements of the TRNSYS software. A ＂Type＂ was thus carried out and the results obtained compared with those of the FDM model. In this work we compare the obtained results with these two numerical ways. The assumptions and the results of simulations are also confronted with those of an existing module in TRNSYS （Type 36） established for the ＂classical＂ Trombe wall. The study shows that the models that we developed are very precise and that certain assumptions must be used with a lot of precautions. The advantages of the composite Trombe solar wall compared to the Classical Trombe wall are highlighted for cold and/or cloudy climates.

CFD Simulations of Wind Effect on Net Solar Heat Gain of South Walls with Internal Insulation

Computational fluid dynamics( CFD) techniques are used to investigate effects of both wind direction and wind speed on net solar heat gain of south wall with internal insulation in winter.Results show that wind effect has a significant influence on the net solar heat gain,where the impact of wind direction is stronger than that of wind speed. For regions in lower reaches of the Yangtze River,difference of their average net solar heat gains( NSHGS) is about 20% due to various wind speeds and wind directions.Buildings in districts with a dominant wind direction of north achieve the highest solar energy utilization.

Designing an Automatic Control System for the Improved Functioning of a Solar Wall with Phase Change Material (PCM)

Solar walls constitute an important green architectural feature that positively contributes to energy saving in buildings. Different configurations may be proposed, such as, solar wall with Phase Change Material (PCM), composite solar wall, photovoltaic solar wall, zigzag solar wall, and solar hybrid wall. Being environmentally friendly, these passive solar components can provide thermal comfort and help save energy. Their disadvantages include principally unpredictable heat transfer, heat losses by night for some systems or inverse thermo-siphon phenomenon. Appropriate energy management techniques can be used to control and optimize the performances of solar walls. An experimental study for energy management of a PCM based solar wall is described in this paper. The experimental results show the effectiveness of the proposed automatic control system in regulating the capture of solar energy.

Energy-saving Technology of Vent in Passive Solar Wall of Rural House of Severe Cold Region

This paper aims at solving the problems of low thermal collection rate,inconvenient maintenance,hindering indoor using during the application of passive solar technologies in rural houses in severe cold region.All these defects prevent the passive solar houses' further development. This paper chooses trombe wall,which has higher thermal efficiency of the passive solar house,as research object. The traditional vent is improved into a new type of ventilation device. This improvement overcomes the shortcoming,which traditional vent loses huge heat,and simplifies the construction of vent. Comparing with traditional trombe wall,the energy saving rate is 15. 69%.

Steel-Tinplate as a Solar Wall Panel and Its Effectiveness

The aim of the research was to investigate black colored steel-tinplate use for absorber and covering material of the collector and compare the efficiency of three types of air heating collectors. This heated air can be exploited for drying of agricultural products, room ventilation and room heating etc. 0.1 × 0.5 × 1.0 meter long FPC （fiat-plate collector） with a sun following platform was built. Air velocity at the experiments was v = 0.9 m/s. Collectors of insulated and un-insulated surfaces with steel-tinplate absorber as a covering material warmed the ambient air up to 10-12 and 5-6 degrees correspondingly （at irradiance 800 W/m^2）. This difference indicates the great importance of insulating the collector body. It can be explained with intense heat exchange between the absorber and ambient air which reduces the efficiency of the collector. There was good correlation with irradiance and the air heating degree. The investigations showed that more effective FPC had the collector with absorber tinplate in the middle of the collector body. At favorable weather conditions the heating degree of the ambient air at the outlet reaches 6-8 degrees more that at the outlet of the insulated collector covered by steel-tinplate.

SOLAR WALL SYSTEM, THE SUN-CENTERED APPROACH TOWARD ECOSYSTEM

Energy costs are continuing to rise as the Earth’s fossil fuel resources diminish. In addition, the population of the earth is increasing, meaning that the use of these scarce resources will increase at a faster rate than in the past. Inevitably, the result will be continuing increases in the Earth’s temperature, resulting in widespread climate change that could have devastating environmental impacts. Thus, as the Earth is moving rapidly toward an energy crisis, sustainable architecture with enhanced energy efficiency takes on great importance in seeking to establish a reasonable balance between human needs and the environment. To achieve this balance, it is essential that we use every available means to manage and reduce people’s basic needs-such as heating or cooling of living spaces-in order to minimize our use of non-renewable energy sources. The Sun is one of the largest and cheapest sources of energy. This tremendous resource has the ability to meet a large portion of human needs. In recent decades, solar energy has been used extensively to achieve environmental sustainability. One of these applications is the use of solar energy to provide warm air in buildings. The purpose of this paper is to investigate renewable energy sources, particularly solar energy and the solar systems currently in use around the world. By assessing their positive and negative attributes, we also intend to propose an alternative solar wall for producing warm air in buildings. Thus, in addition to addressing the weaknesses of previous products and approaches, we intend to augment the energy savings and decrease the costs associated with such systems by combining the positive attributes of several different systems to produce more efficient air heating, lighting, air circulation, and air purification.

Lattice Boltzmann Simulation for Complex Flow in a Solar Wall

In this letter,we present a lattice Boltzmann simulation for complex flow in a solar wall system which includes porous media flow and heat transfer,specifically for solar energy utilization through an unglazed transpired solar air collector(UTC).Besides the lattice Boltzmann equation(LBE) for time evolution of particle distribution function for fluid field,we introduce an analogy,LBE for time evolution of distribution function for temperature.Both temperature fields of fluid(air) and solid(porous media) are modeled.We study the effects of fan velocity,solar radiation intensity,porosity,etc.on the thermal performance of the UTC.In general,our simulation results are in good agreement with what in literature.With the current system setting,both fan velocity and solar radiation intensity have significant effect on the thermal performance of the UTC.However,it is shown that the porosity has negligible effect on the heat collector indicating the current system setting might not be realistic.Further examinations of thermal performance in different UTC systems are ongoing.The results are expected to present in near future.

Trombe walls with nanoporous aerogel insulation applied to UK housing refurbishments

There is an opportunity to improve the efficiency of passive Trombe walls and active solar air collectors by replacing their conventional glass covers with lightweight polycarbonate panels filled with nanoporous aerogel insulation.This study investigates the thermal performance,energy savings,and financial payback period of passive Aerogel Trombe walls applied to the existing UK housing stock.Using parametric modeling,a series of design guidance tables have been generated,providing estimates of the energy savings and overheating risk associated with applying areas of Trombe wall to four different house types across the UK built to six notional construction standards.Calculated energy savings range from 183 kWh/m2/year for an 8 m2 system retrofitted to a solid walled detached house to 62 kWh/m2/year for a 32 m2 system retrofitted to a super insulated flat.Predicted energy savings from Trombe walls up to 24 m2 are found to exceed the energy savings from external insulation across all house types and constructions.Small areas of Trombe wall can provide a useful energy contribution without creating a significant overheating risk.If larger areas are to be installed,then detailed calculations would be recommended to assess and mitigate potential overheating issues.