Optimum design of an off-grid hybrid renewable energy system for an office building

Ataei, Abtin,Nedaei, Mojtaba,Rashidi, Reza,Yoo, Changkyoo American Institute of Physics 2015 Journal of renewable and sustainable energy Vol.7 No.5

Simultaneous water and energy saving of wet cooling towers, modeling for a sample building

Ataei, Abtin,Choi, Jun-Ki,Hamidzadeh, Zeinab,Bagheri, Navid Techno-Press 2015 Advances in environmental research Vol.4 No.3

This article outlines a case study of water and energy savings in a typical building through a modelling process and analysis of simultaneous water-energy saving measures. Wet cooling towers are one of the most important equipments in buildings with a considerable amount of water and energy consumption. A variety of methods are provided to reduce water and energy consumption in these facilities. In this paper, thorough the modeling of a typical building, water and energy consumption are measured. Then, After application of modern methods known to be effective in saving water and energy, including the ozone treatment for cooling towers and shade installation for windows, i.e. fins and overhangs, the amount of water and energy saving are compared with the base case using the Simergy model. The annual water consumption of the building, by more than 50% reduction, has been reached to 500 cubic meters from 1024 cubic meters. The annual electric energy consumption has been decreased from 405,178 kWh to 340,944 kWh, which is about 16%. After modeling, monthly peak of electrical energy consumption of 49,428 has dropped to 40,562 kWh. The reduction of 18% in the monthly peak can largely reduce the expenses of electricity consumption at peak.

Indoor air quality and ventilation requirement in residential buildings: A case study of Tehran, Iran

Ataei, Abtin,Nowrouzi, Ali,Choi, Jun-Ki Techno-Press 2015 Advances in environmental research Vol.4 No.3

The ventilation system is a key device to ensure both healthful indoor air quality (IAQ) and thermal comfort in buildings. The ventilation system should make the IAQ meet the standards such as ASHRAE 62. This study deals with a new approach to modeling the ventilation and IAQ requirement in residential buildings. In that approach, Elite software is used to calculate the air supply volume, and CONTAM model as a multi-zone and contaminant dispersal model is employed to estimate the contaminants' concentrations. Amongst various contaminants existing in the residential buildings, two main contaminates of carbon dioxide ($CO_2$) and carbon monoxide (CO) were considered. CO and $CO_2$ are generated mainly from combustion sources such as gas cooking and heating oven. In addition to the mentioned sources, $CO_2$ is generated from occupants' respirations. To show how that approach works, a sample house with the area of $80m^2$ located in Tehran was considered as an illustrative case study. The results showed that $CO_2$ concentration in the winter was higher than the acceptable level. Therefore, the air change rate (ACH) of 4.2 was required to lower the $CO_2$ concentration below the air quality threshold in the living room, and in the bedrooms, the rate of ventilation volume should be 11.2 ACH.

Application of ozone treatment in cooling water systems for energy and chemical conservation

Ataei, Abtin,Mirsaeed, Morteza Ghazi,Choi, Jun-Ki,Lashkarboluki, Reza Techno-Press 2015 Advances in environmental research Vol.4 No.3

In this study, a complete set of recirculating cooling water system and the required instruments were built in a semi-industrial-scale and a 50 g/h ozone generation plant and a chlorine system were designed for cooling water treatment. Both chlorination and ozonation treatment methods were studied and the results were analyzed during two 45-days periods. The concentrations of ozone and chlorine in recirculating water were constant at 0.1 mg/lit and 0.6 mg/lit, respectively. In ozone treatment, by increasing the concentration cycle to 33%, the total water consumption decreased by 26% while 11.5% higher energy efficiency achieved thanks to a better elimination of bio-films. In case of Carbon Steel, the corrosion rate reached to 0.012 mm/yr and 0.025 mm/yr for the ozonation and chlorination processes, respectively. Furthermore, consumptions of the anti-corrosion and anti-sedimentation materials in the ozone cooling water treatment were reduced about 60% without using any oxidant and non-oxidant biocides. No significant changes in sediment load were seen in ozonation compared to chlorination. The Chemical Oxygen Demand of the blow-down in ozonation method decreased to one-sixth of that in the chlorination method. Moreover, the soluble iron and water turbidity in the ozonation method were reduced by 97.5% and 70%, respectively. Although no anaerobic bacteria were seen in the cooling water at the proper concentration range of ozone and chlorine, the aerobic bacteria in chlorine and ozone treatment methods were 900 and 200 CFU/ml, respectively. The results showed that the payback time for the ozone treatment is about 2.6 years.

Toward residential building energy conservation through the Trombe wall and ammonia ground source heat pump retrofit options, applying eQuest model

Ataei, Abtin,Dehghani, Mohammad Javad Techno-Press 2016 Advances in energy research Vol.4 No.2

The aim of this research is to apply the eQuest model to investigate the energy conservation in a multifamily building located in Dayton, Ohio by using a Trombe wall and an ammonia ground source heat pump (R-717 GSHP). Integration of the Trombe wall into the building is the first retrofitting measure in this study. Trombe wall as a passive solar system, has a simple structure which may reduce the heating demand of buildings significantly. Utilization of ground source heat pump is an effective approach where conventional air source heat pump doesn't have an efficient performance, especially in cold climates. Furthermore, the type of refrigerant in the heat pumps has a substantial effect on energy efficiency. Natural refrigerant, ammonia (R-717), which has a high performance and no negative impacts on the environment, could be the best choice for using in heat pumps. After implementing the eQUEST model in the said multifamily building, the total annual energy consumption with a conventional R-717 air-source-heat-pump (ASHP) system was estimated as the baseline model. The baseline model results were compared to those of the following scenarios: using R-717 GSHP, R410a GSHP and integration of the Trombe wall into the building. The Results specified that, compared to the baseline model, applying the R-717 GSHP and Trombe wall, led to 20% and 9% of energy conservation in the building, respectively. In addition, it was noticed that by using R-410a instead of R-717 in the GSHP, the energy demand increased by 14%.

Hybrid thermal seasonal storage and solar assisted geothermal heat pump systems for greenhouses

Ataei, Abtin,Hemmatabady, Hoofar,Nobakht, Seyed Yahya Techno-Press 2016 Advances in energy research Vol.4 No.1

In this research, optimum design of the combined solar collector, geothermal heat pump and thermal seasonal storage system for heating and cooling a sample greenhouse is studied. In order to optimize the system from technical point of view some new control strategies and functions resulting from important TRNSYS output diagrams are presented. Temperatures of ground, rock bed storage, outlet ground heat exchanger fluid and entering fluid to the evaporator specify our strategies. Optimal heat storage is done with maximum efficiency and minimum loss. Mean seasonal heating and cooling COPs of 4.92 and 7.14 are achieved in series mode as there is no need to start the heat pump sometimes. Furthermore, optimal parallel operation of the storage and the heat pump is studied by applying the same control strategies. Although the aforementioned system has higher mean seasonal heating and cooling COPs (4.96 and 7.18 respectively) and lower initial cost, it requires higher amounts of auxiliary energy either. Soil temperature around ground heat exchanger will also increase up to $1.5^{\circ}C$ after 2 years of operation as a result of seasonal storage. At the end, the optimum combined system is chosen by trade-off between technical and economic issues.

Application of impulse damper in control of a chaotic friction-induced vibration

Mansour Ataei,Ali Asghar Atai,Sajjad Mirjavadi,Mohammad Sahebnasagh,Mansour Nikkhah-Bahrami 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.2

Friction-induced vibration is an important phenomenon with adverse effects on many dynamic systems involving friction. In this study,a very simple and well-known one-dimensional friction-induced dynamic system is considered in which the novel PZT stack impulse damper is incorporated into the system. It has been shown that by appropriately tuning the damping parameters, the chaotic behavior is removed quickly and efficiently. It has also been demonstrated that the system is sensitive to parameter change, and minimal modification of these parameters can revert the chaotic or periodic motion.

The effect of small scale and intermolecular forces on the pull-in instability and free vibration of functionally graded nano-switches

Hosein Ataei,Yaghoub Tadi Beni,Milad Shojaeian 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.4

Pull-in instability and free vibration of cantilever and clamped-clamped beam-type nanoactuators, which are made of Functionally graded materials (FGMs), are investigated using the Modified strain gradient theory (MSGT) under the influence of electrostatic and intermolecular forces. It is assumed that the functionally graded nano-beam made of nickel and silicon nitride and mechanical properties of the nano-beam vary continuously and smoothly in the thickness direction by a simple power-law distribution. Differential quadrature method (DQM), Differential transformation method_Pade approximant (DTM_Pade) and Lumped parameter model (LPM) are used to solve the nonlinear governing equation of the nano-beam, and the obtained results from these methods are compared together. In the end, the effects of size, variation of the length scale parameter, and the volume fraction are discussed and examined. The results show that there are a good agreement between the MSGT and the experimental results, so it can be conclude that the size effect has a substantial impact on the pull-in instability and free vibration results of the beam-type micro/nanoactuator.

Finite Element Analysis of Severe Plastic Deformation by Rectangular Vortex Extrusion

H. Ataei,M. Shahbaz,H. S. Kim,N. Pardis 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.4

In this research, conventional extrusion and twist extrusion are combined to propose a new design for single-pass severeplastic deformation technique, which is called Rectangular Vortex Extrusion (RVE). The effects of different parameters likeRVE die twist angle as well as friction condition at the die-sample interface were studied using finite element analysis. Itwas shown that RVE can be successfully performed as a single-pass severe plastic-deformation technique to impose highstrain values within the sample. It was revealed that the die geometry has the primary role in imposing torsion on the sample,while friction does not significantly increase the process potential for imposing additional torsion. Meanwhile, friction atthe interfaces was found to be effective for increasing the intensity of the velocity gradient within the deformation zone. Theresults show that increasing the die twist angle and friction condition have a synergetic effect on increasing the accumulatedstrain values.

Electric Arc Furnace Voltage Flicker Mitigation by Applying a Predictive Method with Closed Loop Control of the TCR/FC Compensator

Kiyoumarsi, Arash,Ataei, Mohhamad,Hooshmand, Rahmat-Allah,Kolagar, Arash Dehestani The Korean Institute of Electrical Engineers 2010 Journal of Electrical Engineering & Technology Vol.5 No.1

Modeling of the three phase electric arc furnace and its voltage flicker mitigation are the purposes of this paper. For modeling of the electric arc furnace, at first, the arc is modeled by using current-voltage characteristic of a real arc. Then, the arc random characteristic has been taken into account by modulating the ac voltage via a band limited white noise. The electric arc furnace compensation with static VAr compensator, Thyristor Controlled Reactor combined with a Fixed Capacitor bank (TCR/FC), is discussed for closed loop control of the compensator. Instantaneous flicker sensation curves, before and after accomplishing compensation, are measured based on IEC standard. A new method for controlling TCR/FC compensator is proposed. This method is based on applying a predictive approach with closed loop control of the TCR/FC. In this method, by using the previous samples of the load reactive power, the future values of the load reactive power are predicted in order to consider the time delay in the compensator control. Also, in closed loop control, two different approaches are considered. The former is based on voltage regulation at the point of common coupling (PCC) and the later is based on enhancement of power factor at PCC. Finally, in order to show the effectiveness of the proposed methodology, the simulation results are provided.