Energy consumption modelling of a passive hybrid system for office buildings in different climates

The use of energy for space cooling is growing faster than any other end use in buildings, justifying the search for improvements in the energy efficiency of these systems. A simplified model to predict cooling energy consumption in Brazilian office buildings was developed. Artificial neural networks (ANNs) were trained from consumption data obtained by building simulation. As it is intended to be applicable to different climates, a new climate indicator also appropriate for hot and humid climates was proposed and validated. The Sobol sensibility analysis was performed to reduce the number of input factors and thus the number of cases to be simulated. The data was built with the simulation of 250,000 cases in Energyplus. Studies were conducted to define the sample size to be used for the ANN training, as well as to define the best ANN architecture. The developed metamodel was used to predict the consumption of Heating, Ventilating and Air Conditioning (HVAC) system of 66,300 new unseen cases. The results showed that the new proposed climate indicator was more accurate than the usual climate correlations, such as cooling degree hours. The developed metamodel presented good performance when predicting annual HVAC consumption of the cases used to obtain the model (R2 = 0.9858 and NRMSE = 0.068) and also of the unseen cases (R2 = 0.9789 and NRMSE = 0.064).

Download Full-text

A STUDY ON THE ANNUAL VARIATION OF ENERGY CONSUMPTION IN OFFICE BUILDINGS

Journal of Environmental Engineering (Transactions of AIJ) ◽

10.3130/aije.72.81_1 ◽

2007 ◽

Vol 72 (615) ◽

pp. 81-87

Author(s):

Kazuhiko SAKAMOTO ◽

Saburo MURAKAWA ◽

Michimasa SHINOHARA ◽

Daisaku NISHINA ◽

Yoshiyuki UEMURA

Keyword(s):

Energy Consumption ◽

Annual Variation ◽

Office Buildings

Download Full-text

A novel hybrid liquefied natural gas process with absorption refrigeration integrated with molten carbonate fuel cell

International Journal of Low-Carbon Technologies ◽

10.1093/ijlct/ctab021 ◽

2021 ◽

Author(s):

Mehdi Mehrpooya ◽

Parimah Bahramian ◽

Fathollah Pourfayaz ◽

Hadi Katooli ◽

Mostafa Delpisheh

Keyword(s):

Energy Consumption ◽

Fuel Cell ◽

Natural Gas ◽

Hybrid System ◽

Liquefied Natural Gas ◽

Molten Carbonate Fuel Cell ◽

Cooling Load ◽

Absorption Refrigeration ◽

Molten Carbonate ◽

Carbonate Fuel Cell

Abstract The production of liquefied natural gas (LNG) is a high energy-consuming process. The study of ways to reduce energy consumption and consequently to reduce operational costs is imperative. Toward this purpose, this study proposes a hybrid system adopting a mixed refrigerant for the liquefaction of natural gas that is precooled with an ammonia/water absorption refrigeration (AR) cycle utilizing the exhaust heat of a molten carbonate fuel cell, 700°C and 2.74 bar, coupled with a gas turbine and a bottoming Brayton super-critical carbon dioxide cycle. The inauguration of the ammonia/water AR cycle to the LNG process increases the cooling load of the cycle by 10%, providing a 28.3-MW cooling load duty while having a 0.45 coefficient of performance. Employing the hybrid system reduces energy consumption, attaining 85% overall thermal efficiency, 53% electrical efficiency and 35% fuel cell efficiency. The hybrid system produces 6300 kg.mol.h−1 of LNG and 146.55 MW of electrical power. Thereafter, exergy and sensitivity analyses are implemented and, accordingly, the fuel cell had an 83% share of the exergy destruction and the whole system obtained a 95% exergy efficiency.

Download Full-text

A Fundamental Study on the Development of New Energy Performance Index in Office Buildings

Energies ◽

10.3390/en14082064 ◽

2021 ◽

Vol 14 (8) ◽

pp. 2064

Author(s):

Jin-Hee Kim ◽

Seong-Koo Son ◽

Gyeong-Seok Choi ◽

Young-Tag Kim ◽

Sung-Bum Kim ◽

...

Keyword(s):

Energy Consumption ◽

Energy Requirement ◽

Energy Performance ◽

Office Buildings ◽

Light Transmittance ◽

Wall Structure ◽

Fundamental Study ◽

Future Studies ◽

U Value ◽

The Impact

Recently, there have been significant concerns regarding excessive energy use in office buildings with a large window-to-wall ratio (WWR) because of the curtain wall structure. However, prior research has confirmed that the impact of the window area on energy consumption varies depending on building size. A newly proposed window-to-floor ratio (WFR) correlates better with energy consumption in the building. In this paper, we derived the correlation by analyzing a simulation using EnergyPlus, and the results are as follows. In the case of small buildings, the results of this study showed that the WWR and energy requirement increase proportionally, and the smaller the size is, the higher the energy sensitivity will be. However, results also confirmed that this correlation was not established for buildings approximately 3600 m2 or larger. Nevertheless, from analyzing the correlation between the WFR and the energy requirements, it could be deduced that energy required increased proportionally when the WFR was 0.1 or higher. On the other hand, the correlation between WWR, U-value, solar heat gain coefficient (SHGC), and material property values of windows had little effect on energy when the WWR was 20%, and the highest effect was seen at a WWR of 100%. Further, with an SHGC below 0.3, the energy requirement decreased with an increasing WWR, regardless of U-value. In addition, we confirmed the need for in-depth research on the impact of the windows’ U-value, SHGC, and WWR, and this will be verified through future studies. In future studies on window performance, U-value, SHGC, visible light transmittance (VLT), wall U-value as sensitivity variables, and correlation between WFR and building size will be examined.

Download Full-text