Air-Handling-Unit Discharge Air Temperature Reset Based on Outdoor Air Temperature and Cooling Energy Performance in an Office Building

As building systems account for almost half of the total energy consumed by the building sector to provide space heating, cooling, and ventilation, efficiently designing these systems can be the key to energy conservation in buildings. Dual VAV systems with an effective control strategy can substantially reduce the energy consumption in buildings, providing a significant scope of further research on this system configuration. This paper proposes to utilize the warm air duct of the dual VAV system as a dedicated outdoor air (DOA) unit when no heating is required, which allows the cooling load to be effectively distributed between two ducts. A specific control sequence is proposed with different supply air temperature reset strategies to estimate the heating, cooling loads, and fan power energy consumption of the proposed system. A simple two-zone office building is taken as a preliminary case study to simulate the airflow rates and fan power of a single duct VAV and proposed dual VAV systems to illustrate the concept. Finally, a larger multi-zone office building is simulated to measure the annual heating, cooling loads, and fan power energy and compare the energy savings among the systems. The results show significant fan power reduction ranging from 1.7 to 9% and notable heating energy reduction up to 76.5% with a small amount of cooling load reduction varying from 0.76 to 2.56% depending on the different locations for the proposed dual VAV systems. Further energy savings from different supply air temperature reset strategies demonstrate the opportunity of employing them according to climates and case studies. The proposed dual VAV system proves to have the potential to be adapted in buildings for the purpose of sustainability and energy savings.

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Air Distribution and Air Handling Unit Configuration Effects on Energy Performance in an Air-Heated Ice Rink Arena

Energies ◽

10.3390/en12040693 ◽

2019 ◽

Vol 12 (4) ◽

pp. 693 ◽

Cited By ~ 3

Author(s):

Mehdi Taebnia ◽

Sander Toomla ◽

Lauri Leppä ◽

Jarek Kurnitski

Keyword(s):

Temperature Gradient ◽

Air Temperature ◽

Indoor Air ◽

Energy Demand ◽

Energy Performance ◽

Air Distribution ◽

Air Handling Unit ◽

Cooling Coil ◽

Indoor Conditions ◽

Cooling Energy Demand

Indoor ice rink arenas are among the foremost consumers of energy within building sector due to their exclusive indoor conditions. A single ice rink arena may consume energy of up to 3500 MWh annually, indicating the potential for energy saving. The cooling effect of the ice pad, which is the main source for heat loss, causes a vertical indoor air temperature gradient. The objective of the present study is twofold: (i) to study vertical temperature stratification of indoor air, and how it impacts on heat load toward the ice pad; (ii) to investigate the energy performance of air handling units (AHU), as well as the effects of various AHU layouts on ice rinks’ energy consumption. To this end, six AHU configurations with different air-distribution solutions are presented, based on existing arenas in Finland. The results of the study verify that cooling energy demand can significantly be reduced by 38 percent if indoor temperature gradient approaches 1 °C/m. This is implemented through air distribution solutions. Moreover, the cooling energy demand for dehumidification is decreased to 59.5 percent through precisely planning the AHU layout, particularly at the cooling coil and heat recovery sections. The study reveals that a more customized air distribution results in less stratified indoor air temperature.

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Microbiome in an Office Building Using a Cooling Trench as an Outdoor Air Duct

E3S Web of Conferences ◽

10.1051/e3sconf/201911106045 ◽

2019 ◽

Vol 111 ◽

pp. 06045

Author(s):

Mizuki Niimura ◽

U Yanagi

Keyword(s):

Relative Humidity ◽

Energy Saving ◽

Air Temperature ◽

Indoor Air ◽

Principal Coordinate Analysis ◽

Office Building ◽

Metagenomic Analysis ◽

Outdoor Air ◽

Energy Saving Technique ◽

Building Cooling

Subterranean temperature at a depth of 10 m is almost equal to the average outdoor air temperature of the same area. Therefore, if a building cooling trench is used as an outdoor air duct, outdoor air can be cooled in summer and warmed in winter. This energy-saving technique is often used in Japan. However, since the relative humidity in a cooling trench is high, microbe numbers tend to increase in summer. The present study sought to characterize the microbiome status in the cooling trench of such an office building in Japan. Specifically, we performed a metagenomic analysis in which we analyzed DNA directly upon collection from the environment, without intervening cultivation. The results showed the presence of bacteria of the genera Pseudomonas, Lactobacillus, Nesterenkonia, Staphylococcus, Deinococcus, Acinetobacter, Enhydorobacter, and Corynebacterium. Bacteria of the genera Nesterenkonia, Deinococcus, Enhydorobacter, and Corynebacterium predominated on the surface of the trench. Notably, bacteria of the genus Nesterenkonia constituted >50% of the organisms on the surface of the downstream end of the cooling trench. Principal coordinate analysis was used to compare bacterial inhabitants of outdoor air, indoor air from 2nd- and 3rdfloor offices, and the region downstream of the cooling trench. The results suggested that the microbiome of air in this cooling trench influenced indoor air within the building.

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Experimental Performance of an Advanced Air-Type Photovoltaic/Thermal (PVT) Collector with Direct Expansion Air Handling Unit (AHU)

Sustainability ◽

10.3390/su13020888 ◽

2021 ◽

Vol 13 (2) ◽

pp. 888

Author(s):

Jin-Hee Kim ◽

Sang-Myung Kim ◽

Jun-Tae Kim

Keyword(s):

Air Temperature ◽

Electrical Energy ◽

Energy Generation ◽

Energy Performance ◽

Hot Water ◽

Electrical Performance ◽

Direct Expansion ◽

Air Handling Unit ◽

Building Integrated Photovoltaic ◽

Electrical Energy Generation

In addition to electrical energy generation, photovoltaic/thermal (PVT) systems utilize heat from building-integrated photovoltaic (BIPV) modules for domestic hot water and space heating. In other words, a PVT system can improve the electricity efficiency of BIPVs while using the waste heat of BIPVs as a source of thermal energy for the building. By generating thermal and electrical energies simultaneously, PVT systems can improve the utilization of solar energy while enhancing the energy performance of buildings. To optimize the performance of an air-type PVT collector, it is necessary for the system to extract more heat from the PV module. Consequently, this approach decreases PV temperature to improve PV electrical energy generation. The thermal and electrical performance of an air-type PVT collector depends on its design, which affects airflow and heat transfer. Moreover, the performances of the PVT collector can differ according to the coupled facility in the building. In this study, the thermal and electrical performances of an advanced air-type PVT collector with a direct expansion air handling unit (AHU) were analyzed experimentally. For this purpose, six prototypes of an advanced air-type PVT collector were developed. Furthermore, a direct expansion AHU with a heat recovery exchanger (HRX) was designed and built. The advanced PVT collectors with a total capacity of 740 Wp were installed in an experimental house and were coupled to the direct expansion AHU system with a maximum airflow of 700 CMH. The performance of PVT collectors was analyzed and compared with the BIPV system. Results showed that building-integrated photovoltaic/thermal (BIPVT) collectors produced 30 W more power than the BIPV system. When operating the AHU system, the temperature of the BIPVT collector was generally lower than the BIPV. The maximum difference in temperature between BIPVT and BIPV was about 22 °C. During winter season, the BIPVT collector supplied preheated air to the AHU. The supplied air temperature from the BIPVT collector reached 32 °C, which was 15 °C higher than outdoor air temperature.

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Design and Operation of a Polygeneration System in Spanish Climate Buildings under an Exergetic Perspective

Energies ◽

10.3390/en14227636 ◽

2021 ◽

Vol 14 (22) ◽

pp. 7636

Author(s):

Ana Picallo-Perez ◽

Jose Maria Sala-Lizarraga

Keyword(s):

Energy Savings ◽

Energy Performance ◽

Point Of View ◽

Office Building ◽

Air Handling Unit ◽

Depth Analysis ◽

Energy And Exergy ◽

Polygeneration System ◽

Almost All

This work defines and analyzes the performance of a polygeneration system in five different locations in Spain to maintain the thermal comfort and air quality of an office building. The facility is based on a chiller and a CHP engine with PV panels that provide almost all the electricity demand of the chiller. According to the energy performance analysis results, the installation working in Bilbao is a full polygeneration system since no electricity needs to be imported from the grid in summer. To quantify the energy savings related to a separated production facility, polygeneration indicators (percentage of savings PES/PExS and equivalent electric efficiency EEE/EExE) have been calculated in energy and exergy terms. The main motivation for using exergy is based on the ambiguity that can arise from the point of view of the First Law. As expected, the exergetic indicators have lower values than the energetic ones. In addition, an in-depth analysis was conducted for the air-handling unit components. The study shows the behavior of components over the year and the efficiency values from both an energy and exergy point of view. From these facts, the need arises to develop methodologies based on exergy.

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Bin Weather Data for HVAC Systems Energy Calculations

Energies ◽

10.3390/en14123501 ◽

2021 ◽

Vol 14 (12) ◽

pp. 3501

Author(s):

Konstantinos T. Papakostas ◽

Dimitrios Kyrou ◽

Kyrillos Kourous ◽

Dimitra Founda ◽

Georgios Martinopoulos

Keyword(s):

Air Temperature ◽

Air Conditioning ◽

Energy Performance ◽

Climatic Conditions ◽

Weather Data ◽

Climatic Data ◽

Outdoor Air ◽

Energy Demands ◽

Hourly Temperature

The increase in global air temperature is well documented, as during the last several years each decade has been consecutively warmer than the preceding. As climatic conditions affect the energy performance of buildings, the changes in outdoor air temperature and humidity will inevitably lead to significant alterations in energy consumption and costs for the heating, ventilating and air conditioning (HVAC) of buildings. The availability and quality of climatic data play an important role in the accuracy of energy analysis results. In this study, the hourly temperature and relative humidity of outdoor air measurements, for a period of three decades (1983–2012), recorded at the climatic station of the National Observatory of Athens were processed, and an up-to-date set of specific data for the application of bin methods was produced and presented. The data were then used to calculate changes in the energy demands in a typical office building throughout the specified period. Results showed a progressive reduction in the low and increase in the high temperature intervals, leading to an increase in the building’s annual energy requirements for air conditioning of up to 14.5% from the first to the third decade, with decrease in the energy demands for heating and increase in the energy demands for cooling.

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ENERGY CONVERSION MODES DEPENDING ON THE OUTDOOR TEMPERATURE FOR AN AIR HANDLING UNIT WITH A HEAT PUMP

The 11th International Conference ENVIRONMENTAL ENGINEERING 11th ICEE SELECTED PAPERS ◽

10.3846/enviro.2020.602 ◽

2020 ◽

Author(s):

Anton Frik ◽

Vytautas Martinaitis ◽

Juozas Bielskus

Keyword(s):

Energy Conversion ◽

Heat Pump ◽

Air Temperature ◽

Ambient Air ◽

Operating Efficiency ◽

Outdoor Air ◽

Characteristic Energy ◽

Flow Rates ◽

Air Handling Unit ◽

Wide Range

Modern air handling units (AHU) are increasingly finding solutions in which the main energy transformers are an air heat pump (HP) and a heat recovery exchanger (HRE). The energy conversion modes of such devices are constantly changing in accordance with the constant change on the state of the outdoor air (temperature, humidity). Flexibility, being able to respond to ever-changing ambient air parameters, is an important feature of energy transformation component mode control. The overall seasonal efficiency of the air handling unit depends on this. In this work, a thermodynamic analysis of the characteristic energy transformations of the air handling unit is performed, linking the outdoor and ventilated indoor air and HP refrigerant states, flow rates and component loads. Such parametric analysis with respect to the changing outdoor air temperature allowed to clearly reveal, through various indicators, the influence of the individual components on the operating efficiency of the air handling unit. Combinations of parameters have been obtained that enable the selection of the optimal control concept for the energy conversion mode of the components in the air handling unit (component loads, fluids state parameters and flow rates) over a wide range of outdoor air temperatures.

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Selected Aspects of Indoor Climate in a Passive Office Building with a Thermally Activated Building System: A Case Study from Poland

Energies ◽

10.3390/en14040860 ◽

2021 ◽

Vol 14 (4) ◽

pp. 860

Author(s):

Piotr Michalak

Keyword(s):

Air Temperature ◽

Thermal Conditions ◽

Office Building ◽

Normal Operation ◽

Indoor Climate ◽

Thermally Activated ◽

System A ◽

Warm Sensation ◽

Building System ◽

Heating Energy Consumption

Modern buildings with new heating, ventilation and air conditioning (HVAC) systems offer possibility to fit parameters of the indoor environment to the occupants’ requirements. The present paper describes the results of measurements performed in an office room in the first Polish passive commercial office building during four months of normal operation. They were used to calculate parameters describing thermal comfort: vertical air temperature profile, floor surface temperature, predicted mean vote (PMV) and predicted percent of dissatisfied (PPD). Obtained results confirmed good thermal conditions in the analysed room. The average temperature of the floor’s surface varied from 20.6 °C to 26.2 °C. The average vertical air temperature, calculated for working days, was from 22.5 °C to 23.1 °C. The temperature difference between the floor and 5 cm below the ceiling was from −0.9 °C to 6.3 °C. The PMV index varied from 0.52 to 1.50 indicating ‘slightly warm’ sensation, in spite of ‘neutral’ reported by employees. Also measured cooling and heating energy consumption was presented. The performed measurements confirmed the ability of thermally activated building system (TABS) to keep good thermal conditions.

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