A large part of energy cost on cooling applications is attributable to heat income through external walls. The best way to save energy is to use the optimum insulation thickness. In this study, the optimum insulation thicknesses, insulation-energy costs, and savings resulting from the use of these insulations is calculated in cities selected from four different climate zones in Turkey for four various insulation materials such as foamboard, extruded polystyrene (XPS), rock wool, and expanded polystyrene (EPS) in cold storage applications. Calculations show that rock wool insulation material yields the highest savings. Optimum insulation thicknesses vary between 0.074 and 0.159 m, energy savings vary between 30.59 and 80.61 $/m(2), and payback periods for investment cost vary between 3.15 and 3.73 years for the cooling. DOI: 10.1061/(ASCE)EY.1943-7897.0000085. (C) 2013 American Society of Civil Engineers.
Availability of cooling water has been one of the major issues in the selection of nuclear power plant sites. Cooling water issues have frequently disrupted the normal operation at some nuclear power plants during heat waves and long droughts. One potential solution is to use ice thermal storage (ITS) systems that reduce cooling water requirements and boost the plants' thermal efficiency in hot hours. The ITS uses cheap off-peak electricity to make ice and uses the ice for supplemental cooling during peak demand time. The ITS also provides a way to shift a large amount of electricity from off-peak time to peak time. For once-through cooling plants near a limited water body, adding ITS can bring significant economic benefits and avoid forced derating and shutdown during extremely hot weather. For the new plants using dry cooling towers, adding the ITS systems can effectively reduce the efficiency loss during hot weather so that new plants could be considered in regions with a lack of cooling water. This paper will review light water reactor cooling issues and present the feasibility study results. DOI: 10.1061/(ASCE)EY.1943-7897.0000089. (C) 2013 American Society of Civil Engineers.
An experimental and theoretical study was performed to investigate the thermal performance of heat pipes as a heat exchanger. A series of experiments was conducted using R410A, R134a, R22, and R407C as working fluids. The dimensions of the heat pipes that were used in the test rig included 660 mm length, 20 mm outer diameter and 4 mm fin spacing with staggered arrangements. During the tests, the dry bulb temperature of the evaporator inlet was varied from 35 to 55 degrees C and the condenser inlet dry bulb temperature was varied from 20 to 25 degrees C. The influence of face velocity on the performance of the heat pipe heat exchanger was also studied. Many investigations were made to obtain the thermal performance and to ensure efficient and reliable operation of the heat pipe heat exchanger, and the results are presented in the present paper. Tests showed that using R410A, R134a, and R22 provided comparative results, whereas R407C was the least effective. The experimental thermal effectiveness of the heat pipe heat exchanger obtained from the experiments varied between 25 and 70% for R410A, R134a, and R22, whereas the experimental thermal effectiveness of R407C varied between 15 and 50%. A computer simulation program based on the effectiveness method and the number of transfer units was developed to estimate the thermal performance of the heat pipe heat exchanger and to compare the theoretical and experimental results. DOI: 10.1061/(ASCE)EY.1943-7897.0000091. (C) 2013 American Society of Civil Engineers.
In this work, the performance of proton exchange membrane (PEM) fuel cells has been analyzed for different oxidant (air and oxygen) flow rates (supplied at the cathode side). The performance analysis of a single PEM fuel cell coupled with a direct current (DC) permanent magnet motor (as load) was analyzed for air and oxygen. With an increase in the air flow rate, the maximum current values of the PEM fuel cell increase due to the reduction in the concentration of polarization losses (in the polarization curve) and the voltage regulation for the load increases. The maximum power production in a PEM fuel cell is a logarithmic function of different air flow rates. In this system, a DC permanent magnet motor with a reduction gear was used as a load on the PEM fuel cell. With the increase in air flow supply rates, the starting torque of the DC permanent magnet motor load improves. Also, a performance analysis was conducted for pure oxygen, and it has been observed that the PEM fuel cell provides a very good performance, even at the reduced supply flow rate of pure oxygen. For this work, a test bench was developed at Kocaeli University (Turkey), which consists of a PEM electrolyzer, a PEM fuel cell, and a DC permanent magnet motor with an air pump. The results of this work will be very useful for comparing the performances of the PEM fuel cell for different air and oxygen (as oxidants) flow rates for the dynamic loads (e.g., fuel cell vehicles with a DC permanent magnet motor). DOI: 10.1061/(ASCE)EY.1943-7897.0000090. (C) 2013 American Society of Civil Engineers.
Development of a huge wind-sailing solar cell raft (SCR) with dimensions of 5 x 5 km is proposed, which can generate electricity comparable to a 1,000-MW nuclear power plant in low-latitude Pacific Ocean. Solar energy of 8 k . Wh/m(2)/day or more is targeted because the SCR navigates in fine weather using weather satellites. The generated electricity will be transported by battery tankers loaded with a tremendous number of high-energy-density batteries. Studies based on available data indicate that there are vast open seas in the tropical Pacific Ocean, where the maximum solar energy attains 7 k . Wh/m(2)/day annually on average and conditions of winds, waves, and sea currents are favorable for the solar energy system to operate. Three major technologies for breakthrough to realize this system are discussed from their future perspectives. DOI: 10.1061/(ASCE)EY.1943-7897.0000088. (C) 2013 American Society of Civil Engineers.
