Series of experiments for empirical validation of solar gain modelling in building energy simulation codes - experimental setup, test cell characterization, specifications and uncertainty analysis

Empirical validation of building energy simulation codes is an important component in understanding the capacity and limitations of the software. Within the framework of Task 34/Annex 43 of the International Energy Agency (IEA), a series of experiments was performed in an outdoor test cell. The objective of these experiments was to provide a high-quality data set for code developers and modelers to validate their solar gain models for windows with and without shading devices. A description of the necessary specifications for modeling these experiments is provided in this paper, which includes information about the test site location, experimental setup, geometrical and thermophysical cell properties including estimated uncertainties. Computed overall thermal cell properties were confirmed by conducting a steady-state experiment without solar gains. A transient experiment, also without solar gains, and corresponding simulations from four different building energy simulation codes showed that the provided specifications result in accurate thermal cell modeling. A good foundation for the following experiments with solar gains was therefore accomplished

Potencial de economia de energia elétrica através do uso da luz natural e da ventilação híbrida em edifícios comerciais em Florianópolis

O objetivo deste estudo é estimar o potencial de economia de energia elétrica com o uso da luz natural integrada ao sistema de iluminação artificial e a utilização da ventilação híbrida em edifícios comerciais localizados em Florianópolis, SC. O trabalho foi baseado em simulações computacionais nos programas EnergyPlus e Daysim. Foram simulados modelos de ambientes de edificações comerciais, com três geometrias, três dimensões de sala por geometria, dez áreas de janela por modelo e quatro orientações. Os modelos foram examinados por meio de quatro estudos de caso. No Caso 1 (referência), a edificação opera com sistemas de iluminação e de condicionamento artificiais; no Caso 2, ocorre a integração da iluminação natural com a artificial, com condicionamento artificial; já no Caso 3, utilizam-se a ventilação híbrida e a iluminação artificial; no Caso 4, adotam-se a iluminação natural integrada com a artificial e a ventilação híbrida. Os consumos de eletricidade do Caso 1 foram comparados com os demais casos. Assim, foi estimado o potencial de economia de energia elétrica gerado pelo uso da luz natural e ventilação híbrida. Conclui-se que a utilização da iluminação natural e da ventilação híbrida em edificações comerciais localizadas em Florianópolis apresenta potencial de economia de energia elétrica de até 64,9% e que essas estratégias podem ser utilizadas para aumentar a eficiência energética desse tipo de edificação

A novel clustering-enhanced adaptive artificial neural network model for predicting day-ahead building cooling demand

To accurately predict hourly day-ahead building cooling demand, year-round historical weather profile needs to be evaluated. The daily weather profiles among different time periods result in various features of historical datasets. The different appropriate structure and parameters of artificial neural network models may be identified for training datasets with different features. In this study, a novel clustering-enhanced adaptive artificial neural network (C-ANN) model is proposed to forecast 24h-ahead building cooling demand in subtropical areas. The uniqueness of the proposed adaptive model is that k-means clustering is implemented to recognise representative patterns of daily weather profile and thus categorize the annual datasets into featuring clusters. Each cluster of the weather profile, along with the corresponding time variables and cooling demand, is adopted to train one ANN sub-model. The optimal structure and parameters of each ANN sub-model are selected according to its featuring training datasets; thus the ANN sub-models are adaptive. The proposed C-ANN model is tested on a representative office building in Hong Kong. It is found that the mean absolute percentage error of the training and testing cases of the proposed predictive model is 3.59% and 4.71%, which has 4.2% and 3.1% improvement compared to conventional ANN model with a fixed structure. The proposed adaptive predictive model can be applied in building energy management system to accurately predict day-ahead building cooling demand using the latest forecast weather profile

Direct evidence that thromboxane mimetic U44069 preferentially constricts the afferent arteriole

The thromboxane A2 (TXA2) mimetic U44069 has been demonstrated to reduce the GFR and filtration fraction of the normal isolated perfused rat kidney markedly, suggesting a predominant constriction of preglomerular vessels. To assess this possibility directly, effects of U44069 on the renal microvessels of the isolated perfused hydronephrotic kidney were examined. At 10(-6) mol/L, U44069 elicited a 27 +/- 2% decrease in afferent arteriolar (AA) diameter (from 18.8 +/- 0.3 to 13.7 +/- 0.3 micron, P < 0.001). In contrast, efferent arteriolar (EA) diameter decreased by only 9 +/- 1% (from 16.4 +/- 0.5 to 15.0 +/- 0.5 micron, P < 0.001). These effects on both AA and EA were completely reversed by the TXA2 receptor antagonist SQ29548. The calcium antagonist diltiazem reversed U44069-induced AA constriction by 83 +/- 5%. The U44069-induced EA constriction was insensitive to the vasodilator action of diltiazem at concentrations from 10(-8) to 10(-6) mol/L, but at 10(-5) mol/L, diltiazem increased the EA diameter significantly, albeit modestly. Nifedipine also reversed the U44069-induced AA constriction (81 +/- 7%), but failed to inhibit the EA constriction at concentrations from 10(-9) to 10(-6) mol/L. These findings constitute the first direct evidence that a TXA2 agonist preferentially constricts the afferent arteriole. Furthermore, the ability of both the calcium antagonist and SQ29548 to reverse the renal microvascular actions of TXA2 agonists suggests a potential utility of these agents in ameliorating TXA2-induced renal hemodynamic abnormalities

Divergent effects of KCl-induced depolarization on afferent and efferent arterioles

We have previously proposed that renal microvessels exhibit a unique regional heterogeneity. Studies with calcium channel agonists and antagonists suggest that potential-dependent calcium channels may play a more prominent role in the activation of the afferent arteriole than the efferent arteriole. Because KCl-induced depolarization elicits vasoconstriction exclusively by the activation of potential-dependent calcium channels, we tested this postulate directly by ascertaining the vasoconstrictor effects of KCl and countervailing effects of a calcium channel blocker on the afferent and efferent arteriole of isolated perfused hydronephrotic kidneys. Increasing media potassium concentration from 5 to 30 mM resulted in a marked renal vasoconstriction decreasing renal perfusate flow by 61 +/- 4%. An examination of the microvascular response to KCl revealed a predominant response of the afferent arteriole. Thus afferent arteriolar diameter decreased by 38 +/- 6% (i.e., from 20.7 +/- 1.5 to 13.0 +/- 1.8 microns, P less than 0.005), whereas efferent arteriolar diameter decreased by only 12 +/- 4% (i.e., from 15.8 +/- 1.6 to 13.8 +/- 1.4 microns, P = 0.05). Nifedipine completely returned afferent arteriolar diameter to control levels with a mean effective dose of 41 +/- 2 nM. These findings indicate that the afferent arteriole is more responsive to depolarization-induced vasoconstrictor stimuli than is the efferent arteriole and suggest a greater prevalence of potential-dependent calcium channels in this vessel