Toward the accuracy of prediction for energy savings potential and system performance using the daylight responsive dimming system

Choi, H.,Hong, S.,Choi, A.,Sung, M. Elsevier Sequoia S.A 2016 Energy and buildings Vol.133 No.-

This study attempts to verify the accuracy of energy savings prediction using a daylight responsive dimming system. To accomplish this, the real-time power consumption of electrical lighting in a mock-up space was compared with the power consumption that was calculated using 'the prediction method' (Method A), which was suggested to improve the accuracy of the predicted amount of energy savings. In addition, this study suggested the 'indirect illuminance' concept (Method B) to improve the system performance and predict the lighting energy savings potential of a system because certain inherent problems that are caused by the open-loop proportional control algorithm used were identified. Regarding the accuracy of the prediction method, 'Method A' considers the non-linear dimming curve of the luminaires and thus generated data that were more similar to the real measured lighting power consumptions. 'Method B' generated higher energy savings potential (e.g., 36.9-73.8%) compared with those of Method A (e.g., 27.6-72.9%) on each day.

CFD study on aerodynamic power output of a 110kW building augmented wind turbine

Heo, Y.G.,Choi, N.J.,Choi, K.H.,Ji, H.S.,Kim, K.C. Elsevier Sequoia S.A 2016 Energy and buildings Vol.129 No.-

Building augmented wind turbine (BAWT) has been studied numerically. BAWT is a new technology trend to combine wind turbine with building and it has several advantages compared with the conventional stand-alone wind turbine such as minimization of electrical transmission loss and construction cost for the distributed power source and by using existing building. In this paper, a 110kW horizontal axis wind turbine blade is designed and CFD analysis is carried out with various reference wind speed and flow angle for the 110kW BAWT. The results show that aerodynamic power output of 110kW BAWT is higher than that of 110kW stand-alone wind turbine due to the concentration effect caused by the wind speed acceleration between buildings. Also this kind of advantage appeared in flow angle between -30<SUP>o</SUP> and 15<SUP>o</SUP>. Due to the fixed rotational direction of the wind turbine, the effect of flow angle shows asymmetric nature. It is also shown that to exceed Betz limit of 0.593 is possible by the effect of buildings similar to the ducts and shrouds. The results of this study can be applied to the research and development of various BAWT and enhancement of energy efficiency of wind turbine.

Evaluation of clean air delivery rates and operating cost effectiveness for room air cleaner and ventilation system in a small lecture room

Noh, K.C.,Yook, S.J. Elsevier Sequoia S.A 2016 Energy and buildings Vol.119 No.-

In general, room air cleaners are rated according to clean air delivery rate (CADR). However, ventilation systems have not yet been assessed using a metric similar to CADR. This study establishes a new mass balance equation that compares the CADRs of a ventilation system and a room air cleaner. Experiments and CFD simulations were conducted to evaluate and compare the CADRs of room air cleaners and ventilation system in the view of removing particles from indoor air. In addition, the operating cost effectiveness of ventilation system and room air cleaner was investigated. The results showed that the room air cleaners showed their performance independently, even when two or more room air cleaners were operated simultaneously. In the ventilation system, an air filter with MERV11 or higher rating was recommended to reduce the indoor particle concentration when 100% outdoor air was supplied. It was possible to select an air filter with MERV11or lower rating when the recirculation airflow rate was increasing up to 70%. The CADR of the room air cleaner was higher than that of the ventilation system regardless of the particle size and the filter performance when the airflow rate was same. The operating cost effectiveness (CADR/kW) of the room air cleaner was higher than that of the ventilation system at the same airflow rate. Therefore, the room air cleaner must be more cost-effective than the ventilation system for reducing particle concentration indoors.

Fabrication of the flexible nanogenerator from BTO nanopowders on graphene coated PMMA substrates by sol-gel method

Sankar Ganesh, R.,Sharma, Sanjeev K.,Abinnas, N.,Durgadevi, E.,Raji, P.,Ponnusamy, S.,Muthamizhchelvan, C.,Hayakawa, Y.,Kim, Deuk Young Elsevier Sequoia S.A 2017 Materials chemistry and physics Vol.192 No.-

<P><B>Abstract</B></P> <P>Nanostructured bismuth titanate (Bi<SUB>4</SUB>Ti<SUB>3</SUB>O<SUB>12</SUB>) or BTO powders were synthesized by the combustion method. The crystalline phase of BTO nanopowders was evaluated from X-ray diffraction (XRD) and further confirmed by selected area electron diffraction (SAED) pattern. The SEM and TEM micrographic images clearly showed the nanosheets like morphology of BTO nanopowder. The EDS spectrum of BTO nanopowder showed the elemental peaks of O, Bi and Ti at 0.53 keV, 2.41 keV and 4.49 keV, respectively. FTIR band peaks were observed at 815 and 595 cm<SUP>−1</SUP> corresponding to the stretching vibrations of BiO and TiO. The red shift in optical absorption of BTO was observed and the bandgap decreased from 3.18 to 3.08 eV as the calcined temperature increased from 600 to 800 °C. The sandwich structure, called the nanogenerator, Graphene/BTO-PDMS/Graphene (G/BTO/G), was fabricated on graphene coated polymethyl methacrylate (PMMA) substrates, which produced a peak voltage (10 mV) by applying the pressure from human's finger. The switching mechanism of BTO nanosheets was observed to be dependent on the polarity and intrinsic dipole formation.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Bi<SUB>4</SUB>Ti<SUB>3</SUB>O<SUB>12</SUB> (BTO) nanosheets synthesized from a simple combustion method. </LI> <LI> SEM & TEM images confirmed the nanosheets structure with a hexagonal shape. </LI> <LI> XRD and SAED pattern of BTO nanosheets confirmed the orthorhombic crystal structure. </LI> <LI> Flexible G/BTO/G nanogenerator fabricated by sol-gel method. </LI> <LI> Peak voltage was observed to be 10 mV by applying pressure from human's finger. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Performance assessment and multi objective optimization of an Organic Rankine Cycle driven cooling air conditioning system

Nasir, Muhammad Tauseef,Ali, Muhammad Ansab,Khan, Tariq S.,Al-Hajri, Ebrahim,Kadri, Muhammad Bilal,Kim, Kyung Chun Elsevier Sequoia S.A 2019 Energy and buildings Vol.191 No.-

<P><B>Abstract</B></P> <P>Present work aims to investigate the thermal performance assessment of different combinations of working fluids for an Organic Rankine Cycle powered Vapor Compression Cycle (ORC-VCC) for air-conditioning applications. Analysis of system performance is conducted for a fixed cooling load of a small conditioned space having a sensible heat factor of 0.7, at different ambient conditions. A preliminary evaluation of the system at the baseline conditions was conducted considering the second law efficiency, overall heat capacity of exchangers, overall internal exergy destruction, and overall Coefficient of Performance. Afterwards, parametric study was performed for the best performing candidates from the preliminary analysis using second law efficiency and overall heat capacity of heat exchangers. The system parameters considered for the study include saturated temperatures of heat exchangers, ORC boiler superheat, pinch points and the sub-cooling of both the ORC and VCC condensers. Then, multi objective optimization was performed using Genetic Algorithm followed by multi-criteria decision-making using Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) to select the best optimal solutions from the Pareto front. Sixteen combinations comprising of four working fluids, R245fa, R600, R600a, and R134a were analyzed. The optimization results showed R245fa ORC-R600a VCC to be the best candidate at ambient conditions of 30 °C, while at 35 °C and 40 °C, R600a ORC-R245fa VCC was found to be the most suitable candidate.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The prospects of different working fluids and their combinations in an ORC driven air conditioning system are investigated. </LI> <LI> Ambient conditions considering the outdoor temperatures of 30 °C, 35 °C and 40 °C with 50% relative humidity is selected. </LI> <LI> Working fluids R245fa, R134a, R600a, and R600, and their combinations are the investigated. </LI> <LI> Sensitivity analysis of different parameters on the second law efficiency and UA values of heat exchangers is evaluated. </LI> <LI> Multi-objective optimization of the exergetic efficiency and the UA values of heat exchangers is carried out. </LI> </UL> </P>

Experimental verification of a virtual water flowmeter applicable to air conditioning systems

Kim, M.H.,Jeong, J.W. Elsevier Sequoia S.A 2017 Energy and buildings Vol.155 No.-

The main purpose of this research is to suggest a virtual water flowmeter applicable in hydraulic systems with low-cost sensors. Practical procedures for realizing virtual water flowmeters for constant flow pumps (i.e., Cases 1 and 2) and variable flow pumps (i.e., Cases 3 and 4) are proposed in this paper. In Case 1, for measuring the water flow rate through a constant flow pump, the pump head was measured and the water flow rate was estimated using the pump characteristic curve obtained from the manufacturer or by deriving an empirical model based on the field measurement data. In Case 2, the water flow rate through a valve with a constant flow pump was estimated by measuring the pressure head between the valve and the valve opening position. The valve characteristic curve can be obtained by deriving an empirical model based on the initial field test results. The water flow rate through the variable flow pump was calculated, using the pump affinity laws and an empirical model, by measuring the frequency (i.e., Case 3) or input power (i.e., Case 4). The initial setup and test procedures for virtual flowmeters are also proposed in this research for practical use in the field. To verify the proposed procedures, experiments were conducted using constant and variable flow pumps in a pilot system. It was found that the virtual water flowmeters showed 2.9% to 6.7% of root mean square error from Case 1 to Case 4, compared with an ultrasonic water flowmeter, through long-term experimental verification.

Working fluids selection and parametric optimization of an Organic Rankine Cycle coupled Vapor Compression Cycle (ORC-VCC) for air conditioning using low grade heat

Nasir, M.T.,Kim, K.C. Elsevier Sequoia S.A 2016 Energy and buildings Vol.129 No.-

This paper presents the thermal performance of several combinations of working fluids in the Organic Rankine Cycle (ORC) powered Vapor Compression Cycle (VCC), for the domestic air conditioning. Seven working fluids, R245fa, R123, R134a, R1234yf, R1234ze (E), Butane and Isobutane were considered and a total of forty nine candidates were analyzed. The objective was defined to provide air at 15<SUP>o</SUP>C to a space whose temperature was desired to be at 24<SUP>o</SUP>C, as the outdoor temperature varies from 30<SUP>o</SUP>C-40<SUP>o</SUP>C. The hot water at 100<SUP>o</SUP>C and 1.5atm was considered as the heat source. With pressure ratios, COP, mass flow rates and the ratio of COP to pressure ratio as the performance indicators, Isobutane gave the best performance in the standalone VCC. For the ORC as the prime mover for the VCC, by considering the system thermal efficiency, cycle pressure ratios, mass flow rates and expander outlet volumetric flow rates as the criteria, R134a was found to be the best candidate. Henceforth R134a ORC- Isobutane VCC was the best combination. And by optimizing the system parameters of the VCC condenser sub cooling, its condenser temperature and the ORC condenser pressure, this combination gave a COP of 0.219, with dry air at the VCC evaporator inlet and 0.281, with 50% relative humidity air at the VCC evaporator inlet.

In search for sustainable globally cost-effective energy efficient building solar system - Heat recovery assisted building integrated PV powered heat pump for air-conditioning, water heating and water saving

Todorovic, M.S.,Kim, J.T. Elsevier Sequoia S.A 2014 Energy and buildings Vol.85 No.-

Obtained as a research result of conducted project, this paper presents an innovative, energy efficient multipurpose system for a sustainable globally cost-effective building's solar energy use and developed methodology for its dynamic analysis and optimization. The initial research and development goal was to create a cost-effective technical solution for replacing fossil fuel and electricity with solar energy for water heating for different purposes (for pools, sanitary water, washing) in one SPA. After successful realization of the initial goal, the study was proceeded and as a result, the created advanced system has been enriched with AC performance. The study success was based on understanding and combined measurements and by BPS made predictions of AC loads and solar radiation dynamics as well as on the determination of the synergetic relations between all relevant quantities. Further, by the performed BPS dynamic simulations for geographically spread buildings locations, it has been shown that the final result of the conducted scientific engineering R&D work has been the created system of confirmed prestigious to the sustainability relevant performance - globally cost-effective building integrated photovoltaic powered heat pump (HP), assisted by waste water heat recovery, for solar AC, water heating and saving.

Construction and calibration of a large-area heat flow meter apparatus

Yang, Inseok,Kim, Daeho,Lee, Sanghyun,Jang, Hyunmin Elsevier Sequoia S.A 2019 Energy and buildings Vol.203 No.-

<P><B>Abstract</B></P> <P>A large-area heat flow meter apparatus that can measure the thermal conductivity of a 900 mm × 900 mm insulating specimen was constructed in this work with a relative expanded uncertainty of 1.4%. By the use of a reference material certified with an assigned value of thermal conductivity, the heat flux transducers in the apparatus were calibrated in the mean temperature range of −10 °C to +50 °C. The following three tests on the robustness of measurement results were conducted: (1) assessment of the reproducibility upon reloading the specimen a few times into the apparatus, (2) use of various temperature differences on the two surfaces of the specimen, and (3) configuration of the vertical temperature profile around the specimen differently while maintaining the temperatures on the specimen surface and their difference the same. The results of the three robustness tests supported that the measurements were consistent and the uncertainty assessment for the thermal conductivity measurement using the constructed heat flow meter apparatus was valid.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A heat flow meter apparatus for a 900 mm × 900 mm insulation specimen was constructed. </LI> <LI> The apparatus was calibrated using a certified material from −10 °C to +50 °C. </LI> <LI> The thermal conductivity measurement was tested to be reproducible and robust. </LI> <LI> The expanded uncertainty of the thermal conductivity measurement was 1.4%. </LI> </UL> </P>

Experimental study on Venturi-type natural ventilator

Kim, Yeong Sik,Han, Dong Hun,Chung, Hanshik,Jeong, Hyomin,Choi, Soon-Ho Elsevier Sequoia S.A 2017 Energy and buildings Vol.139 No.-

<P><B>Abstract</B></P> <P>With the vigorous spread of renewable energy, much attention has been paid to natural ventilation. The natural ventilator is usually classified into a passive type and an active type. In this study, the Venturi-type ventilator, which is one of the passive type and basically operated by the Bernoulli’s principle, was experimentally investigated to evaluate the ventilation characteristics according to the outdoor wind velocities and the opening area of a wall. It was confirmed from the experimental results that the ventilation rate of the Venturi-type ventilator was linearly increased and that the ventilation rate was affected by an intake opening area. The wider the intake opening size gets, the more the ventilation rate increases. Furthermore, the new coefficient of β, which reflects the pressure loss from the intake opening to the mixing zone of the Venturi-type ventilator was introduced and experimentally evaluated. The value of β, which was evaluated as about 0.08, provides the simple calculation means to estimate the ventilation rate through the Venturi-type ventilator only if the geometric dimensions are known.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ventialtion rate measurements through Venturi-type natural ventilator. </LI> <LI> Area ratio effect (Intake opening area/Ventilator suction area) to ventilation rate. </LI> <LI> Saturation of ventilation rate over any fixed wind speed in a specific area ratio. </LI> <LI> Ventilation characteristics due to the wind velocity and the intake opening area. </LI> </UL> </P>