Thermal Inertia Of Buildings Research Articles

Integrated electricity and heating demand-side management for wind power integration in China

The wind power generation system will play a crucial role for developing the energy conservative, environmentally friendly, and sustainable electric power system in China. However, the intermittency and unpredictability of wind power has been an obstacle to the deployment of wind power generation, especially in the winter of northern China. In northern China, a combined heat and power (CHP) unit has been widely utilized as a heat and electricity source.Considering the flexible operation of CHP with introduction of electric heat pumps (EHPs), this paper proposes a new method of electricity and heating demand side management to facilitate the wind power integration with the purpose of energy conservation in a unit-commitment problem. The thermal characteristics of demand side such as the thermal inertia of buildings and thermal comfort of end users are taken into consideration. Moreover the distributed electric heat pumps (EHPs) widely used by city dwellers are introduced into the wind-thermal power system as the heating source and spinning reserve so as to increase the flexibility of heating and electricity supply. The simulation results show that the new method can integrate more wind power into power grid for electricity and heating demand to reduce the coal consumption.

Assessing energy savings in cooling demand of buildings using passive cooling systems based on ventilation

The objective of this article is to develop and test a simplified method to compute the savings in building cooling demand by use of passive cooling systems based on ventilation (direct night ventilation, air–soil heat exchangers, controlled thermal phase-shifting, evaporative cooling, as well as possible combinations thereof). The systems are characterized in terms of a climatic cooling potential, independently of any building, which is then compared to the cooling load of a particular building. The method is tested against an extensive numerical simulation campaign, combining diverse passive cooling systems and sizes with diverse constructive and operational modes for an administrative building situated in Geneva. The key point of the simplified method is to choose an appropriate time resolution, for taking into account the building thermal inertia. Although best results are obtained with a daily resolution, good results are also obtained with monthly data, where an overestimation of the passive cooling fraction remains less than 20% in half of the cases. This opens way for using the method for first assessing the potential of these passive cooling techniques on a large spatiotemporal scale, for which integrated building and system simulation becomes prohibitive.

Influence of the Thermal Inertia in the European Simplified Procedures for the Assessment of Buildings’ Energy Performance

This study aims to highlight the importance of thermal inertia in buildings. Nowadays, it is possible to use energy analysis software to simulate the building energy performance. Considering Italian standards, these analyses are based on the UNI TS 11300 that defines the procedures for the national implementation of the UNI EN ISO 13790. These standards require an energy analysis under steady-state condition, underestimating the thermal inertia of the building. In order to understand the inertial behavior of walls, a cubic Test-Cell was modelled through the dynamic calculation code TRNSYS and three different wall types were tested. Different stratigraphies, characterized by the same thermal transmittance value, composed by massive elements and insulating layers in different order, were simulated. Through TRNSYS, it was possible to define maximum surface temperatures and to calculate thermal lag between maximum values, both external and internal. Moreover, the attenuation between external surface temperatures and internal ones during summer (July) was calculated. Finally, the comparison between Test-Cell’s annual energy demands, performed by using a commercial code based on the Italian standard UNITS 11300 and the dynamic code, TRNSYS, was carried out.

An Integrated Approach for an Historical Buildings Energy Analysis in a Smart Cities Perspective

Currently, the study of the energy performance of buildings is based on a simplified calculation that estimates the thermal loads using monthly or seasonal average outdoor temperatures. In addition, the employed software require technical data such as the specific heat capacity of materials, but at the same time they are not able to properly consider the thermal inertia of buildings. The more precise evaluation allows to assess the correct interventions for energy requalification under a smart cities perspective. This study was performed considering a stationary software (Aermec MC11300) and a dynamic software (TRNSYS). Three simulations considering transparent elements characterized by progressively improved properties of thermal transmittance and solar gain factor have been performed. It has been performed a comparison between the outputs of the two software in order to highlight the different ways of evaluating the energy contributions on thermal loads. Finally, the models were validated by means of an in-situ measurement campaign using a heat flow meter - in order to measure the thermal transmittance of the opaque walls - and a thermographic camera. This modus operandi allowed to appreciate how the use of a dynamic software is more appropriate to deal with the inertial properties of the structure to calculate in a more detailed way the annual thermal loads and to obtain more information on individual heating zones.

Experimental and Numerical Study of a Usual Brick Filled with PCM to Improve the Thermal Inertia of Buildings

The integration of a PCM layer into an external building wall diminished the amplitude of the instantaneous heat flux through the wall. The types of PCM, its location in the wall and its amount, have been studied in this paper. A two-dimensional transient heat transfer model has been developed and solved numerically using the commercial Computational Fluid Dynamics (CFD) package Fluent. The numerical results have been verified and validated with an experimental model. The considered model consists of usual brick with square holes used as construction materials for residential buildings in Algeria, some of these square holes are filled with PCM. The results showed that the PCM introduced in square holes can improves considerably the thermal inertia of brick and a combination of the types of PCM, its location in the wall and its amount, is very important for improve reduction of heat gain before it reaches the indoor space.

Study and Effect of Orientation Two Room of Buildings Located in Ghardaia, Algeria

Thermal comfort plays a major factor in building infrastructure sector. It has a big impact on building interior temperature as well as on energy balance and environment. In the current paper the influence of thermal isolation, building orientation and thermal inertia of building envelop on interior ambient temperatures have been studied. To meet our objective, a methodological procedure has been followed. It consists of elaboration of computing program written in MATLAB code to simulate the proposed mathematical model. The main objective of the proposed mathematical proposed model is to compute different delivered temperatures under real climatic and environment conditions. Confrontation of the results found through simulation with those found experimentally shows a clear consistence. Thus the theoretical model is experimentally validated. It can be concluded that: The most effective measure to achieve a better results is thermal insulation. The orientation of thermally isolated building doesn’t have a considerable impact on interior temperature. Thermal inertia of buildings may thus generate thermal comfort. It was revealed that an adequate use of stone thermal inertia is essential to achieve a better building thermal comfort.

A field study on building inertia and its effects on indoor thermal environment

Energy consumption in Spanish school buildings is higher during spring seasons. Thermal inertia of buildings can help to reduce such consumption, improve comfort, and even replace HVAC systems. This thermal inertia is usually associated to heavy wall construction, but the truth is there are other parameters that can have a significant effect on this property. This paper describes a field case study of school buildings with different types of wall construction, aimed at demonstrating real thermal inertia effects on indoor conditions. Besides air temperature measurements, HAM tools were used to simulate indoor air conditions. Results showed a good agreement between simulated and experimental air temperature results, and that other building construction parameters, such as the use of permeable coverings, may have a large impact on indoor thermal conditions and energy consumption.

Thermal building behaviour in summer: long-term data evaluation using simplified models

This study focuses on the impact of the meteorological environment and the building's thermal inertia on the indoor temperature performance in a passively cooled office building with night ventilation. Data from a long-term monitoring campaign and short-term measurements are used to identify the correlation between outdoor and indoor temperature in a building under ordinary use and to derive the energy balance of an office room. Temperature performance and energy balance are merged in a comprehensive thermodynamic model, which takes steady-state conditions, short-term and long-term dynamics into account. In contrast to extensive simulation studies, the presented method is based on a straightforward mathematical model using Fourier analysis of temperature time series and an energy balance model, which focuses on fundamental information.

Modeling and experimental study on an innovative passive cooling system—NVP system

A kind of innovative building energy efficiency system—Night Ventilation with PCM Packed Bed Storage (NVP) system is proposed. The mathematical model of NVP system is built to analyze its thermal behavior. The building thermal inertia, the model of Latent Heat Thermal Energy Storage (LHTES) system and the ventilation scheme are all taken into considered in the mathematical model. An experimental installation of NVP system used in Beijing is introduced. Its thermal performances including the effect on decreasing the room temperature and the energy consumption are discussed. Experimental results show that NVP system has great potential in the field of energy efficiency building. And the mathematical model of NVP system is validated with the experimental data.

Electrical energy saving in a passive-solar-heated residence using a direct gain attached sunspace

This paper deals with the thermal analysis and the auxiliary electrical energy saving in a passive-solar-heated residence. The particular residence is using an attached sunspace of inclined walls and roof and an electrically heated thermal storage floor as backup to satisfy the heating requirements. The thermal analysis and the corresponding electrical energy saving are determined using three different methods which are applied for thermostatically controlled temperature regime. The first is a simplified method based on three parameters: (1) the solar/load ratio (SLR), (2) the building thermal inertia and (3) the monthly unutilizability (UU). The other methods are, namely: the UU method and the SLR method.

A new simplified method for evaluating the thermal behaviour of direct gain passive solar buildings

A new simplified method for calculating the monthly solar heating fraction of direct gain buildings is presented. Two different operating regimes have been considered: (1) thermostatically controlled temperature, typical of buildings with auxiliary heating systems; and (2) free-floating temperature, typical of buildings without auxiliary heating systems. In the latter case, to quantify the thermal behaviour of the building, a comfort solar fraction is introduced. In this method, the solar fraction is a function of three parameters: (1) the solar/load ratio; (2) the building thermal inertia; and (3) the monthly non-utilizability. Some examples of the application of the new method are presented, as well as comparisons with the results from existing methods.

Developments in degree-day methods of estimating energy use

This paper extends established methods of estimating the heating energy consumption of buildings. It describes how month-by-month degree-day calculations may be developed to capture effects of building thermal inertia and of day to day variations of incidental gains. It also demonstrates how the part-load efficiency of heating appliances may be included and how the methodology may be applied to bivalent heating systems.