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[en] Import of a huge proportion of electrical energy from the Southern African Power Pool, and the geographical location and population distribution of Botswana stimulated the need to consider renewable energy as an alternative to imported power. The paper describes a systematic experimental study on a mini-solar chimney system. Particular attention is given to measurements of air velocity, temperature and solar radiation. The results for the selected 5 and 6 clear days of October and November, respectively, are presented. These results enable the relationship between average insolation, temperature difference and velocity for selected clear days to be discussed. (author)
[en] Highlights: • We develop an economic model different from related models. • We evaluate the initial investment cost of a plant built in northwest China. • We analyze the cost and benefit of a plant built in northwest China. • By the sensitivity analysis, we examine the sensitivity of TNPV to many parameters. - Abstract: This paper develops a model different from existing models to analyze the cost and benefit of a reinforced concrete solar chimney power plant (RCSCPP) built in northwest China. Based on the model and some assumptions for values of parameters, this work calculates total net present value (TNPV) and the minimum electricity price in each phase by dividing the whole service period into four phases. The results show that the minimum electricity price in the first phase is higher than the current market price of electricity, but the minimum prices in the other phases are far less than the current market price. The analysis indicates that huge advantages of the RCSCPP over coal-fired power plants can be embodied in phases 2–4. In addition, the sensitivity analysis performed in this paper discovers TNPV is very sensitive to changes in the solar electricity price and inflation rate, but responds only slightly to changes in carbon credits price, income tax rate and interest rate of loans. Our analysis predicts that RCSCPPs have very good application prospect. To encourage the development of RCSCPPs, the government should provide subsidy by setting higher electricity price in the first phase, then lower electricity price in the other phases
[en] Highlights: ► The simulation code predicts temperatures to within 1.5% of recorded data. ► The ventilation is predicted to within 5% accuracy. ► Effects of heat inertia cause the actual drying path to deviate from the simulated path. ► The two paths converge in the end with a final moisture content prediction to within 10%. ► The simulation code can be used to compare and refine the dryer designs for optimum drying performance. - Abstract: A simulation procedure describing the drying process within a Chimney-Dependent Solar Crop Dryer (CDSCD) has been developed. The simulation follows the authors’ experimental work on the effect of varying drying chamber roof inclination on the ventilation and drying processes, and their work on the development of simulation code to help optimise ventilation in such dryers. The current paper presents the modelling and subsequent validation of the drying process inside the dryer, to come out with a design tool for the CDSCD. The work considers the height of the crop shelf above the drying-chamber base, crop resistance to airflow and the shading on the drying-chamber base and their effects on the drying process. The under-load condition temperatures and velocities are predicted to within a relative difference of 1.5% and 10%, respectively of the observed values. Even though the heat inertia of the physical model causes deviation between the predicted drying path and the observed drying path, the two paths tend to converge at the end of each drying cycle, with a general prediction to within 10% relative difference of the observed crop moisture content. The validation results show that the simulation code can serve as an effective tool for comparing and refining the designs of the CDSCD for optimum drying performance
[en] Highlights: • Transpired solar collector updraft tower has been studied experimentally. • Transpired solar collector updraft tower efficiency ranges from 60 to 80%. • A comparison has been made with other SUT prototypes. • Three times higher efficiency compared to the glazed collectors of conventional solar towers. - Abstract: A novel solar updraft tower prototype, which consists of transpired solar collector, is studied, its function principle is described and its experimental thermal performance is presented for the first time. A test unit of transpired solar collector updraft tower was installed at the campus of Trakya University Engineering Faculty in Edirne-Turkey in 2014. Solar radiation, ambient temperature, collector cavity temperatures, and chimney velocities were monitored during summer and winter period. The results showed that transpired solar collector efficiency ranges from 60% to 80%. The maximum temperature rise in the collector area is found to be 16–18 °C on the typical sunny day. Compared to conventional solar tower glazed collectors, three times higher efficiency is obtained. With increased thermal efficiency, large solar collector areas for solar towers can be reduced in half or less.
[en] In this paper two main events and their causes have been investigated and a potential alternative supporting system will be provided. The first event to be addressed is the Station Blackout (SBO) caused by the inherent unreliability of the Emergency Diesel Generators (EDGs) and Alternative AC (AAC) power sources. Different parameters affect The EDG unreliability; for instance, mechanical, operational, maintenance and surveillance. Those parameters will be analyzed and linked to plant safety and Core Damage Frequency (CDF). Also the AACs, the SBO diesel generators, will be studied and their operational requirements similarity with the EDGs will be discussed. The second event to be addressed is the Loss of Ultimate Heat Sink (LUHS) caused by the degradation of heat exchange effectiveness, that is, the poor heat transfer to the Ultimate Heat Sink (UHS). Different causes to such case were observed; intake lines blockages due to ice and foreign biological matters formation and oil spill near the heat sink causing the oil leakage to the heat exchangers tubes. The later cause, oil spill, has been given a special attention here due its potential effects for different nuclear power plants (NPPs) around the world; for example, Finland and the United Arab Emirates (UAE). For the Finnish case, the Finnish nuclear regulator (STUK) took already countermeasures for such scenario by introducing alternative heat sink, cooling towers, for the primary used heat sink, sea water, for one of its nuclear power plants. The abundance of the solar irradiation in the UAE region provides a perfect condition for the implementation of solar power applications. Utilizing this unique characteristic of that region may provide promising alternative and diverse options for solving potential safety related issues of their NPPs. The Solar Chimney Power Plant (SCPP) could be employed to serve as a supporting system to provide emergency power, in the case of SBO, and emergency cooling, in the case of LUHS. In addition to its dual functionality; it provides a complete independent and diverse means of safety functions supporting, a free carbon oxide power production source and allow following the world's trend toward the usage of renewable energy sources. The Solar Chimney Power Plant was suggested to be employed as a supporting system for NPPs to provide emergency power, in case of SBO, and emergency cooling, in case of LUHS. It provides a complete independent and diverse means of safety function supporting. Following the SCPP operation requirements of the availability of high solar irradiation, the UAE region provides a perfect environment for its implementation; furthermore, it can be linked to the under-construction NPPs at Al-Barakah site to deliver alternative emergency power and emergency cooling. Due to the inherent unreliability of the currently utilized EDGs and the AAC power sources, a postulated SBO event could affect the safety of the NPP in general, and for the specific case of the UAE NPPs, a LUHS caused by oil spill accident in the UHS could be experienced, given the massive oil related activates being performed in the Arabian Gulf. Comparing the similarity between Al-Barakah site and the Loviisa NPP in Finland; looking for solution and alternatives for the enhancement of their reactors safety should be considered by the UAE nuclear regulator
[en] The Solar and Wind Energy Resource Assessment (SWERA) database is used to prepare and discuss scenarios for solar thermal applications in Brazil. The paper discusses low temperature applications (small and large scale water heating) and solar power plants for electricity production (concentrated solar power plants and solar chimney plants) in Brazil. The results demonstrate the feasibility of large-scale application of solar energy for water heating and electricity generation in Brazil. Payback periods for water heating systems are typically below 4 years if they were used to replace residential electric showerheads in low-income families. Large-scale water heating systems also present high feasibility and many commercial companies are adopting this technology to reduce operational costs. The best sites to set up CSP plants are in the Brazilian semi-arid region where the annual energy achieves 2.2 MW h/m2 and averages of daily solar irradiation are larger than 5.0 kW h/m2/day. The western area of Brazilian Northeastern region meets all technical requirements to exploit solar thermal energy for electricity generation based on solar chimney technology. Highlights: ► Scenarios for solar thermal applications are presented. ► Payback is typically below 4 years for small scale water heating systems. ► Large-scale water heating systems also present high feasibility. ► The Brazilian semi-arid region is the best sites for CSP and chimney tower plants.
[en] Highlights: • Three different electrohydrodynamic layouts are applied in the solar chimney pilot. • Effective parameters of electrohydrodynamic is represented in every layout. • The air velocity and heat transfer were increased outstandingly. • The temperature distribution in the absorber surface and the fluid is investigated. • The performance and the efficiency of the solar chimney pilot are increased. - Abstract: The effect of the electrohydrodynamic system with various electrode layouts on a solar chimney pilot is investigated experimentally. A pilot setup was constructed which consisted of a chimney with 3 m height and 3 m collector diameter. The purpose of this research was to enhance the solar chimney performance with the electrohydrodynamic system for the parallel, radial, and symmetric layouts. By using of corona wind, the outlet fluid temperature is increased, and the outlet absorber is decreased. For the three layouts, the most growth in the outlet fluid temperature is 14 °C, which is observed in the parallel layout. Also, in the parallel array, the most outlet absorber temperature drop is 7 °C. The results show that parallel layout with six electrodes and 3 cm spacing between the electrodes has the best performance. Also, various hours of the day are studied and the best time for turning on the electrohydrodynamic system is 1:00 p.m. The electrohydrodynamic system makes an increase in the fluid velocity from 1.7 to 2.3 m s"−"1_, and this growth improves the performance about 28%.
[en] Offshore wind energy is gaining significance around the world as the most suitable source of renewable energy. India, blessed with 7500 km of coastline has already announced the offshore wind energy policy based on feasibility studies for offshore wind potential. National Institute of Wind Energy (NIWE) and M/s Suzlon Energy Limited have installed first LiDAR-based offshore measurement platform with the technical expertise of the National Institute of Ocean Technology (NIOT), MoES in the Gulf of Khambhat and the Gulf of Kachchh. This article illustrates the analysis, design methodology and various innovative strategies involved in the installation of LiDAR-based measurement platforms. (author)
[en] Solar Chimney is an interesting unconventional method for production of electricity from the sun. It consists of a large greenhouse which purpose is to heat the air and create air flow directing it to the base of the chimney and then through the pressure-staged turbine array. Solar Chimney can be used for pick load operation. Australia plans 200 MW solar plant for the and of 2004, which will be the tallest man made structure in the world with a height of almost 1 km and greenhouse diameter reaching 7.5 km. It is a result of Australia's commitment to find alternative energy solutions in order to reduce the environmental impact of fossil and nuclear technologies for electric power production. (Author)
[en] Trombe Walls and solar chimneys are examples of passive solar air heating systems. However, the airflow and thermal efficiency characteristics of this type of system are not well understood, and partly for this reason, they are not commonly utilised. This paper reports on an experimental investigation into buoyancy-driven convection in a test rig designed to simulate the operation of a passive solar collector. The test rig comprised a vertical open-ended channel, approximately 1a square, heated from one side. The channel depth could be varied from 20mm to 110mm, and heating inputs varied from 200W to 1000W. Temperatures and airflow rates were measured and recorded, to characterise both steady-state and transient performance. The principal findings are: 1. Time constants (for heating)ranged typically between 30 and 70 minutes. 2. Flow regimes were mainly laminar (Reynolds number varing from ∼500 to ∼4000, depending on heat input and channel depth. 3. The thermal efficiency (as a solar collector and the heat transfer coefficient were functions of heat input, and were not depended on the channel depth. 4. The mass flow rate through the channel increased bath as the heat input increased and as the channel depth increased. The paper presents these findings and discusses their implications in more detail.(Author)