Güneş bacası güç santrallerinde kule çapının çıkış gücüne etkisi

Güneş bacası güç santralleri düşük bakım maliyetleri ve sıfır CO2 salınımları ile çok cazip güneş enerjisi sistemleridir. İlk uygulaması olan Manzanares tesisinden sonra geometrik ve iklimsel parametrelerin sisteme etkisi ile ilgili sayısız çalışma yapıldı. Bu çalışmada literatürde yeterince irdelenmeyen baca çapı değişiminin sisteme etkisi detaylı olarak incelendi. ANSYS ticari yazılımı ile oluşturulan 3 boyutlu CFD modelinde güneş ışın izleme algoritması ve DO (ayrık koordinatlar) modeli ile RNG k-ε türbülans modelleri kullanılarak simülasyonlar yapıldı. Diğer geometrik parametreler için referans tesis örnek alınarak baca çapı 4.865-64.866 m arasında değiştirilmek suretiyle sistem davranışı araştırıldı. Baca çapı değişiminin ilk olarak sistem içerisindeki basınç ve hız dağılımına etkisi referans durumla karşılaştırılarak analiz edildi. Ayrıca baca çapı değişiminin sistemin güç çıkışı, kütlesel debisi, verimi ve türbin konumunda ortalama basınç farkına etkisi değerlendirildi. Manzanares pilot tesisi için maksimum performans veren baca çapı değerinin 24.325 m olduğu sonucuna varıldı. Baca çapı 24.325 m yapıldığında referans duruma göre güç çıkışının % 85.9 artarak 101 kW olacağı tespit edildi. Benzer şekilde verim de referans duruma göre % 94 artış göstererek % 0.194 olarak hesaplandıSolar chimney power plants (SCPPs) are very attractive solar energy systems with low maintenance costs and zero CO2 emissions. After its first application, the Manzanares facility, numerous studies were conducted related to the impact of geometric and climatic parameters on the system. In this study, the impact of chimney diameter change on the system, which has not been adequately examined in literature, has been investigated in detail. In the 3D CFD model created with ANSYS commercial software, simulations have been conducted by using the solar ray tracing algorithm and DO (discrete ordinates) model along with RNG k-ε turbulence model. By referencing the Manzanares facility for the other geometric parameters, system behaviour has been assessed by changing the chimney diameter between 4.865-64.866 m. The impact of the change in tower diameter on the pressure and velocity distribution in the system has been analysed first in comparison with the reference situation. In addition, the influence of diameter change on the power output, mass flow rate, efficiency of the system and the average pressure difference at the turbine position has been evaluated. It has been concluded that the chimney diameter value that gives maximum performance for the Manzanares pilot plant is 24.325 m. When the chimney diameter has been configured as 24.325 m, it has been seen that the power output will improve by 85.9% compared to the reference situation and will be 101 kW. Similarly, the efficiency rises by 94% in comparison with the reference case, and becomes 0.194%

Dünden bugüne güneş bacası güç santralleri: sistem güç çıkışına etki eden performans parametreleri

Son yıllarda artan insan nüfusu ve teknolojik gelişmeler doğrultusunda enerji tüketimi hızlaartmakta buna bağlı olarak enerji üretiminde kullanılan birincil kaynakların tüketimihızlanmaktadır. Bu durum bütün bilim insanlarını ve araştırmacıları bu konuya yoğunlaşmayaitmiştir. Çevre kirliliğine ve CO2 emisyonuna sebep olan birincil kaynaklar yerine yenilenebilirve temiz enerji arayışı araştırmacıların odak noktası olmuştur. Çeşitli yenilebilir enerjikaynakları bulunmasına rağmen rüzgâr ve güneş enerjisi geniş coğrafyalarda kullanılma imkânıile daha fazla ön plana çıkmaktadır. Güneş enerjisinin konut ve su ısıtma amacıyla kullanımıçok eskiye dayanırken son yıllardaki teknolojik gelişmeler ile güneşten elektrik elde edilmesiyaygınlaştı. Güneşten elektrik elde etmek için fotovoltaik sistemler popülaritesini korusa da sonyıllarda güneş enerjisinin basit fiziksel yasalar ile elektrik enerjisine dönüştürüldüğü güneşbacası güç santralleri üzerine araştırmalar hızlanmıştır. Güneş bacası güç santralleriperformansları ve sıfır CO2 emisyonu ile araştırmalarda fazlaca yer almıştır. Toplayıcısı ilealdığı güneş ışınımını bünyesindeki havaya aktararak hava hareketini bacaya yönlendirip türbinaracılığıyla rüzgâr enerjisini elektrik enerjisine dönüştüren bu sistemlerin genel olaraktoplayıcı, baca ve türbin olmak üzere 3 temel elemandan oluşur. Güneş bacası güç santrallerininperformansını temelde iklimsel ve geometrik parametreler belirlemektedir. İklimselparametreler sistemin kurulduğu lokasyona bağlı olmakla birlikte sonradan değiştirilmesimümkün olmayan etkileri içerir. Geometrik parametreler ise baca yüksekliği, toplayıcı yarıçapı,baca çapı, toplayıcı yüksekliği ve toplayıcı eğimi gibi sistemin tasarımından kaynaklanır. Buparametrelerin sisteme etkisi farklı çalışmalarda araştırmacılar tarafından değerlendirilmiştir.Bu çalışmada sistemin boyutsal olarak 2 temel elemanı olan toplayıcı yarıçapı ve bacanınboyutlarındaki değişimin sistemin performansına etkisi değerlendirilir. Toplayıcı yarıçapındakiartışın sistemin performansını genel olarak arttırdığı belirtilse de bazı araştırmacılar yarıçap içinbelirli bir üst sınır olduğunu bu sınırdan sonra güç çıkışının artmayacağını vurguladılar. Benzerşekilde baca yüksekliğindeki artışın sistemin performansını genel olarak arttırdığı ancak bazıaraştırmacılar bu artışın belirli bir noktadan sonra sistemin güç çıkışını arttırmayacağını iddiaederler. Çalışmada geometrik tutarlılık açısından Manzanares prototipini referans alançalışmalar karşılaştırılarak baca yüksekliği ve toplayıcı yarıçapının sistemin güç çıkışına etkisideğerlendirilir.</p

Performance approach to solar chimney power plants: Chimney and collector effect

Solar chimney power plants are an important solar energy system in terms of CO2 emissions and maintenance costs. The system, which was first implemented in the Manzanares region of Spain in the 1980s, has a chimney height of approximately 200 m and a collector diameter of 244 m. The translucent collector is responsible for transferring the solar radiation falling on it to the system and creating a closed cover. The thermal energy of the sun passes through the translucent collector and reaches the system air and from there to the ground. Meanwhile, the system air is exposed to the thermal effects of the sun and the solar radiation reaching the ground causes an increase in temperature on the ground. The system air, whose temperature increases due to the solar radiation falling on it and the convection effects on the ground, accelerates upwards with the vacuum effect created by the high chimney in the collector centre, towards the chimney entrance, and from there it accelerates upwards through the chimney. Meanwhile, electricity is produced by the turbine positioned at a certain height inside the chimney. In the study, the maximum performance range for the collector and chimney, which are the most important building blocks of the system, is examined. The increase in chimney height and collector size not only improves the performance of the system, but also causes a large increase in cost. Look for optimum values for collector size and chimney height.&nbsp;</p

Potential of waste heat use in solar chimney power plants: Performance enhancement through soil-based heat storage medium

The sun is the favourite of renewable energy sources due to its potential. Its popularity is increasing day by day, especially with its ability to be used in wide geographies and different usage areas. Solar chimney power plants can convert the sun's thermal energy into electricity without the need for an additional system. It heats the air trapped in its large-area collector both by direct solar radiation and indirectly by the greenhouse effect. Additionally, the semi-permeable collector allows solar radiation to reach the ground. In this way, the temperature increase on the floor contributes to the continuous heat transfer to the system air. Solar chimney power plants can also provide power output during hours when the sun is not shining. To achieve this, the use of an energy storage unit on the ground is required. In this study, it is aimed to obtain continuous power output from the system by integrating the waste heat of a power plant into the ground of the solar chimney power plants. The thermal conductivity of the floor material becomes important at this point. The heat provided by the continuous waste heat in the underground piping system allows the solar chimney power plant to provide 24-hour power output. In the study, the power output that can be obtained at different radiation intensities and temperatures during the day is calculated. In addition, during hours when there is no sun, only the power output provided by the driving force of the chimney and the heat transfer obtained from waste heat is evaluated. Current power outputs are evaluated for different performance parameters and a comparison is presented with the results obtained from similar studies in the literature. It is seen that the performance of the system, which gives approximately 50 kW power output in the reference case, gives twice as much power output as the hybrid system.</p

Numerical performance modelling of solar chimney power plants: Influence of chimney height for a pilot plant in Manzanares, Spain

3D axisymmetric CFD model is developed for a solar chimney power plant (SCPP) in Manzanares, Spain, and potential impacts of chimney height (H) on main performance parameters are comprehensively analysed. Mesh-independent solutions are achieved, and accuracy justification is done over the previous numerical and experimental attempts prior to parametric research. Discrete ordinate (DO) non-grey radiation model with solar ray tracing approach is adopted in the research. A very good accordance is achieved between the numerical findings and in-situ data. For five different H values, temperature, pressure and velocity distributions within the pilot plant are achieved as well as maximum air velocity, mass flow rate of air, temperature rise in collector, dynamic pressure difference at the turbine position, overall system efficiency and potential electrical power. It is found that maximum air velocity thus mass flow rate shows an exponential growth in H. On the contrary, temperature rise in collector notably reduces with the increasing H. Overall system efficiency is determined to be 0.67% whenH = 500 m. Power output (P) linearly rises with H. The system is capable of generating 55 and 134 kW electrical power, for H = 200 and 500 m, respectively

THE EFFECT OF THE BARRIER DESIGN ON THE HEAT CONDUCTION IN DOUBLE GLASS WINDOWS

In daily life, people spend most of their time indoors. This situation increases the need to keep indoorenvironments warm in winter and cool in summer. This directly increases energy consumption. Since energydependence is dependent on fossil fuels and causes severe environmental pollution, energy consumption canbe significantly reduced with insulation applications to be made in buildings. Windows are responsible forapproximately 40% of the heat transfer in buildings. For this, reducing heat losses through windows cansignificantly reduce energy consumption. This study aims to restrict air movement with barriers in doubleglazedwindows. By preventing the air movement between the double glazing, the natural convection effectswill weaken and decrease the heat transmission coefficient. The 2D CFD model is verified by using ANSYSengineering commercial software and the heat transfer coefficient (Uw) of the insulated glass with air within20 mm is determined as approximately 1.6 W/m2K. Then, the change in the heat transfer coefficient of theinsulating glass is evaluated with differently positioned barriers. It is seen that the barrier placed diagonallyreduces the heat transfer coefficient. It is seen that the heat transfer coefficient of the insulating glass with thebarriers placed in two different ways is 1.4 W/m2K and 1.52 W/m2K, respectively. Similarly, it is understoodthat the thickness of the insulating glass also affects the heat transfer coefficient. This study shows that theheat loss from the windows can be reduced by up to 12.5% by using a barrier.</p

Collector factor in a solar chimney power plant: CFD analysis for the pilot plant in Manzanares SAULĖS KAMINO ELEKTRINĖS KOLEKTORIAUS KOEFICIENTAS: MANSANARESO BANDOMOSIOS JĖGAINĖS SKAIČIUOJAMOSIOS SKYSČIŲ DINAMIKOS (CFD) ANALIZĖ

Solar chimneys are popular systems for their simple structures and clean energy generation. Thanks to its semi-permeable structure, the collector, one of the system’s basic elements, transfers solar radiation to the system. As a result of the heating of the system air under the collector by the solar radiation passing through the collector, it is directed to the high chimney in the collector centre. During the upward movement of the system air, it converts its energy into electricity via a tur-bine. Due to its large structure, estimating the amount of energy entering the collector system creates a great cost. The ideal size for the collector is therefore important. This study offers a recommendation for the ideal collector size for the pilot plant in Manzanares in terms of collector size and power output. While 59 kW power output is obtained with the system with a collector radius of 122 m in the reference case, it is observed that the power output increases by 78% when the collector radius is increased to 170 m and the collector area is doubled. The ratio of the ideal collector radius to the reference size for the pilot plant should be in the range of 1–1.5

Impact of support pillars on the thermal insulation performance of vacuum glazing

People spend most of their daily lives indoors and indoor environments should be warm in winter and cool in summer to be considered comfortable. With the increasing human population, more energy needs arise due to the required comfort conditions, therefore, energy efficiency gains great importance. Thermal insulation of windows in closed environments is extremely important to reduce energy use. This study presents a new approach on supporting pillars in vacuum glass technology, which has gained importance in recent years. The effect of using divergent and convergent cylindrical pillars instead of traditional cylindrical pillars on window thermal insulation performance was evaluated. With the 2D CFD model, firstly, after the verification from the company data and literature, the simulations were repeated by changing the thermal properties of the glass and pillars material. The effect of this change on the window heat transfer coefficient (Uw) was examined. In all analyses, the outdoor temperature was assumed to be 5 degrees centigrade and the indoor temperature to be 25 degrees centigrade. It was seen that the Uw value in the reference state was 1.21 W/m2K. With divergent cylindrical pillars, the Uw value decreased by 37.5% to 0.76 W/m2K; with convergent cylindrical pillars it decreased by 24.4% to 0.919 W/m2K. It was understood that for vacuum glass, the thermal properties of glass were more decisive than the properties of pillars. It was also understood that better insulation would be obtained in vacuum glass by using divergent cylindrical pillars. In the study, the results of Uw were given for values ranging between 0.1-0.4 W/mK for glass and 0.04-0.20 W/mK for pillars.Keywords:</p

ANALYSIS OF THE EFFECT OF THE ENERGY STORAGE UNIT ON THE PERFORMANCE OF THE SOLAR CHIMNEY POWER PLANT WITH DIVERGENT CHIMNEY DESIGN THROUGH THE MANZANARES PILOT PLANT

The increasing use of fossil fuels for the increasing energy demand in the world in the last century has caused serious environmental pollution. One of the energy sources needed to correct this situation is the sun. It is a renewable energy source that can be an alternative to fossil fuels in terms of solar potential. The sun, which has different uses, has had an important place in human life since ancient times. In recent years, the usage areas of solar energy have been increasing, and researchers have been carrying out intensive studies on this subject. It is seen that researchers use solar energy effectively, except for indoor heating and water heating purposes only with traditional methods.</p

NUMERICAL ANALYSIS OF THE EFFECT OF ADDING PARALLEL GROOVES ON FIN PERFORMANCE IN RECTANGULAR FIN DESIGN

Performance is extremely important in electronic devices. Especially during use, any pause or freezing may cause undesirable results. This is even more important for critical tools. Although there are many parameters that affect performance in electronic devices, warming is one of the most important parameters after the production process. In particular, the device temperature, which affects the service life and performance, should be kept under control and should not exceed the maximum level. This study is about fin structures added for cooling in electronic devices. They are structures that aim to remove more heat by convection from a hot surface by increasing the fin surface area. It is impossible to add a cooling system, especially for smallscale electronic structures. In this case, it is tried to improve the convection effects by providing more surface area with fin structures. In the study carried out, the effect of the parallel rectangular groove structure in the fins on the heat dissipation is evaluated with the 3D CFD model using the student version of ANSYS engineering commercial software. First, the efficiency of the rectangular fin is measured at 400 K fin bottom temperature and 300 K ambient temperature. Then, the effect of the parallel rectangular grooves to be placed on the wing on the heat removal from the wing and the efficiency of the wing is interpreted. For a heat convection coefficient of 20 W/m2K, the efficiency is 78.11% for the non-corrugated fin in the reference state. With 1 row of rectangular grooves positioned in parallel, the fin efficiency increases by 5% and becomes 82.375%. It is seen that the wing efficiency increases with rectangular grooves placed in 2,3 and 4 rows, but the increase tends to converge.&nbsp;</p