Solar Updraft Tower Research Articles

Influence of thermal energy storage system on flow and performance parameters of solar updraft tower power plant: A three dimensional numerical analysis

A 3D numerical model is developed for solar updraft tower to identify the effect of thermal energy storage system. Flow parameters such as temperature, velocity, pressure, and density are estimated, analyzed and compared for 2 different models, model - 1 (without thermal energy storage) and model −2 (with thermal storage). The collector diameter of 3.5 m, chimney height of 6 m, chimney diameter of 0.6 m, inlet gap of 0.15 m, slope of the collector 30° are the dimensions considered for model - 1. Model – 2 consists of the same dimensions of model – 1 with additional thermal energy storage system. Sand-rock mixture is considered as energy storage material and it has the thickness of 0.15 m and diameter of 3.5 m. Numerical simulations are performed under steady state condition for both the models at various times (10.00 a.m., noon, 1.00 p.m., 2.00 p.m. and 4.00 p.m.) in a day and for model – 2 up to 8.00 p.m. Results are compared with experimental and theoretical data from literature and found that the results are matching. Performance parameters such as power output, collector efficiency and overall efficiency of system were estimated and it was found that the values of model – 2 are lower because of heat stored by thermal storage device. Maximum power output for both models (79.92 W for model – 1 and 63.8 W for model – 2) was obtained at 1.00 p.m. The addition of thermal storage system enhanced the plant operation time till 8.00 p.m.

Experimental study of performance dependence on absorber and number of air inlets of solar updraft tower

Experimental study of performance dependence on absorber and number of air inlets of solar updraft tower

Numerical analysis of flow parameters on solar updraft tower (SUT) with and without thermal energy storage (TES) system

Effect of thermal energy storage (TES) system of solar updraft tower (SUT) is studied in this work. A 3D numerical model was developed to analyze the same and estimate the performance parameters. Two models were developed: case-I and case-II. Case-I is without TES system and the case-II with TES system. The collector diameter 3.5 m, chimney height 6 m, chimney diameter 0.6 m, inlet gap 0.15 m, slope of the collector 30° were the dimensions considered for the model of case-I. Case-II consisted of same dimensions of case-I with additional storage material of thickness 0.15 m and diameter of 3.5 m. Steady-state pressure-based solver with realizable k–ɛ turbulent model and solar ray-tracing algorithm were employed. SIMPLE scheme was used for pressure–velocity coupling and in spatial discretization; first order upwind for momentum and second-order upwind for energy were used. Flow parameters such as velocity, pressure, density, and temperature were estimated for both the cases. Results from the numerical simulations showed that adding TES to the SUT plant decreases the pressure, velocity, and temperature of air because certain amount of heat energy was stored in case-II setup.

Effect of chimney height and collector roof angle on flow parameters of solar updraft tower (SUT) plant

Solar updraft tower (SUT) is a viable option to produce electrical energy from solar energy. Extensive studies needed to estimate the flow parameters and analyse this set-up. A 3D numerical model is developed to analyse the flow parameters such as pressure, temperature and velocity of SUT plant. Effect of geometrical parameters such as chimney height and collector roof angle is studied numerically in this work. The diameter of absorber plate and chimney as 3.5 m and 0.6 m and the collector roof angle, chimney height and inlet gap as 30o, 6 m and 0.1 m, respectively, are selected for numerical simulation. A parametric study is performed for varying chimney heights from 3 to 8 m and collector roof angle 20o–35o with an increment of 5o each case. The airflow inside the SUT is turbulent, renormalization group (RNG) k-e model is selected, and (discrete ordinates) DO model is incorporated for evaluation of radiation effect inside the domain. From the simulation results, it is concluded that when collector roof angle is increased, air velocity is increased and also air temperature is slightly dropped. It is found that there is 31% velocity enhancement when the chimney height is increased from 3 to 8 m.

Numerical Investigation on the Effects of Baffles with Various Thermal and Geometrical Conditions on Thermo-Fluid Dynamics and Kinetic Power of a Solar Updraft Tower

Solar updraft towers (SUTs) are used for renewable power generation, taking advantage of the thermal updraft air flow caused by solar energy. Aerodynamic devices have been applied to SUTs to improve their performance and the baffle is one such device. Here, we investigate the effect of baffle installation on the thermo-fluid dynamic phenomena in the collector of an SUT and how it enhances the overall SUT performance using computational fluid dynamics analysis. Two geometric parameters (height and width of baffle) and two thermal boundary conditions of the baffle (adiabatic condition and heat flux condition) were tested through simulations with 10 different models. The vortex generated by the baffle has a positive effect on the delivery of heat energy from the ground to the main flow; however, one disadvantage is that the baffle inherently increases the resistance of the main flow. Over 3% higher kinetic power was achieved with some of the simulated baffle models. Therefore, an optimum design for baffle installation can be achieved by considering the positive and negative thermo-fluid dynamics of baffles.

Modeling, simulation and optimization of general solar updraft towers

Abstract A model to describe a solar chimney power plant with a generally sloped collector field and for the general situation of humid air is presented. This is a significant development of existing simple models for solar updraft towers with planar collector fields for the situation of purely dry air. The model describing the gas dynamics in the collector and in the chimney includes a turbine model, friction and heat transfer losses, evaporation and condensation models etc. However, the relevant physics can be modeled in one space dimension. It is the result of a fully compressible gas dynamic model in the small Mach number limit. A numerical algorithm is defined which admits very fast simulations. Therefore optimization procedures can easily be applied. Numerical results on optimization with respect to geometric and physical parameters which may be considered both in the planning and the operational phase are presented. The results are compared qualitatively and – if available – quantitatively to prototype data and to simulations from the literature.

CFD analysis on flow and performance parameters estimation of solar updraft tower (SUT) plant varying its geometrical configurations

ABSTRACTA 3D numerical model is developed to estimate and analyze the flow and performance parameters of solar updraft tower (SUT) plant. The effects of geometrical parameters, such as chimney height and collector roof angle are studied. A turbulent, renormalization group (RNG) k-ε model and discrete ordinates (DO) model is used to solve the governing equations. It is concluded that with an increase in collector roof angle, air velocity increases but air temperature decreases. There is 31% velocity enhancement when the chimney height is increased from 3 to 8 m. The overall, chimney and collector efficiencies and power output are estimated to be 0.00354%, 0.0465%, 81.4% and 0.255 W, respectively.

Design and Fabrication of Solar Updraft Tower and Estimation of Power Generation; Initially Focused on Bangladesh

In our studies we focused on area of sourcing, converting and delivering sustainable energy, concentrating at the potential role of solar power. Power generation through a solar updraft tower (SUT) has been a promising approach for sustainable generation of renewable energy. Developing nations are faced with many challenges. Conventional sources are insufficient to meet the increasing demand of a developing, industrious nation (e.g. Bangladesh). Our project aims in reducing electricity crisis and forming a solution for our country, Bangladesh. The electricity generated can be supplied to the national grid. This will mean reduced cost for the government in the long run and also allow the government to reduce its dependency on costly and unsustainable fossil fuel. This cost reduction benefit can be passed on to the public as reduced energy cost or preferably through nationwide energy infrastructure development. This technology will not only help with the energy concern of Bangladesh but also will help to improve the situations of other developing countries alike Bangladesh. All in all implementing this technology will pave the way towards a better world and form a part of an integrated ecosystem of sustainable energy technology.

Thermal analysis of solar updraft tower by using different absorbers with convergent chimney

An experimental analysis of the solar updraft tower (SUT) with convergent chimney was undertaken by using different absorbers. Four different types of absorber materials were used in the experiment to store the solar intensity and exchanging it to the air being heated. The SUT comprised the three basic parts named as the solar collector, the tower or chimney and the turbine. An analysis for the solar updraft tower has been carried out, which describes the performance of solar updraft tower based on energy and exergy analysis. The maximum temperature distinction between ambient air and collector outflow was obtained in the case of SUT with small stone pieces (16.4 °C). The maximum average collector efficiency, collector exergy efficiency and overall efficiency of the SUT were acquired with the small stone pieces. The benefit of SUT system is that it would be favorable in the region with magnificent sunbeams to satisfy the demand of electricity.

Hybrid transpired solar collector updraft tower

A novel hybrid solar updraft tower prototype, which consists of photovoltaic panels and transpired solar collector, is studied, its function principle is described and its experimental 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 2015. PV modules cover 42% of transpired solar collector area. PV and turbine power output, solar radiation, ambient temperature, temperature rise, collector cavity temperatures, and chimney velocities were monitored during 18 months. The results showed that hybrid solar updraft tower efficiency increased by about 2% in average compared to stand-alone PV system. The temperature rise in hybrid solar updraft tower is found to be 12–14 °C on the typical sunny day. Energy was produced continuously for 24 h. The results showed that solar utilization ranges from 60% to 80% during daytime.

Performance parameter evaluation, materials selection, solar radiation with energy losses, energy storage and turbine design procedure for a pilot scale solar updraft tower

Performance investigation of a prototype of solar updraft tower (SUT) power plant is carried out in this study. The diameters of the solar collector and chimney are of the 3.5 and 0.6m respectively. The objective of this work is to investigate the performance of SUT and to tabulate all the inputs and estimated parameters with the materials of a SUT power plant. All the three main components’ (turbine, solar collector and a chimney) process parameters are estimated and discussed. Appropriate materials are discussed and selected for solar collector, chimney, turbine and heat storage materials. Solar beam, diffuse and global radiation are estimated to analyze the performance of collector cover. Energy losses in solar collector cover and transmissivity estimations are performed to calculate theoretical energy collected in solar collector. Pressure drop inside the chimney is estimated and from that the actual power output of the turbine is calculated. The quantity of heat storage materials needed is evaluated in terms of both mass and volume. Theoretically the maximum velocity of air is achieved at the chimney base and is 2m/s. The maximum overall efficiency of the plant is estimated as 0.0028%. The maximum theoretical power output of the plant is 0.633W.

Analysis of fluid flow and heat transfer on a solar updraft tower power plant coupled with a wind turbine using computational fluid dynamics

The objective of this study was to develop a more realistic numerical model for solar updraft tower power plants. To accomplish this, a three-dimensional (3-D) simulation for the geometric parameters of the Manzanares prototype coupled with a real turbine was carried out using computational fluid dynamics (CFD). The RNG k-ε turbulence closure, discrete ordinates (DO) non-grey radiation model and solar ray-tracing algorithm were employed. In addition, a comparatively simpler simulation using a reverse fan model to implement pressure drop across the turbine was conducted. The pressure, velocity and temperature distributions through the system were considered, and the results of the simplified model were compared to those of a system coupled with a real turbine, to assess the proper pressure jump value to be assigned in the reverse fan model. Results showed that, compared to the real turbine model pressure drop, the reverse fan model with a 43.7% lower assigned pressure jump predicted the same performance. The numerical model developed in this study provides a highly accurate and reliable approach for predicting the performance of a solar updraft tower power plant, taking into account all the main phenomena of the system.

Thermodynamic analysis of the drying process of bananas in a small-scale solar updraft tower in Brazil

This paper presents a thermodynamic analysis of the drying of bananas inside a small-scale prototype solar updraft tower in Belo Horizonte, Brazil. A model based on the first and second laws of thermodynamics was developed, using the ambient conditions and airflow parameters data obtained in the experimental prototype. The exergy rates were determined, and it was concluded that the incident solar radiation plays an important role on the drying process of bananas, the higher the solar radiation, the higher the exergy rates. The exergetic efficiency was compared to that obtained without products inside the solar updraft tower, and it was found that the exergetic efficiency increased from about 20% to 27% with load.

Wind effects on a solar updraft power plant

A solar updraft power plant (SUPP) technology is a promising large-scale utilizing technology of renewable energy resource. Since the feasibility of the technology was demonstrated by the successful operation of the Manzanares pilot prototype, the plant performance has been widely studied. This paper carries out computational fluid dynamics (CFD) simulations of an SUPP, analyzes the characteristics of the mean and fluctuating wind pressures on the internal and external surfaces of solar updraft tower (SUT) and the upper and lower surfaces of solar collector roof, examines the effects of the SUT and baffle to the pressure on the roof's upper and lower surfaces, and discusses the effects of vortexes to the plant surface pressures and the potential effect of vortex shedding to the tower structural dynamics. It is hoped that this paper will guide further study and accurate design on this interesting power plant.

DESIGN AND CONSTRUCTION OF A PROTOTYPE SOLAR UPDRAFT CHIMNEY IN ASWAN/EGYPT

This work is part of a joint project funded by the Science and Technology Development Fund (STDF) of the Arab republic of Egypt and the Federal Ministry of Education and Research (BMBF) of the Federal Republic of Germany. Continuation of the use of fossil fuels in electricity production systems causes many problems such as: global warming, other environmental concerns, the depletion of fossil fuels reserves and continuing rise in the price of fuels. One of the most promising paths to solve the energy crisis is utilizing the renewable energy resources. In Egypt, high insolation and more than 90 percent available desert lands are two main factors that encourage the full development of solar power plants for thermal and electrical energy production. With an average temperature of about 40 °C for more than half of the year and average annual sunshine of about 3200 hours, which is close to the theoretical maximum annual sunshine hours, Aswan is one of the hottest and sunniest cities in the world. This climatic condition makes the city an ideal place for implementing solar energy harvesting projects from solar updraft tower. Therefore, a Solar Chimney Power Plant (SCPP) is being installed at Aswan City. The chimney height is 20.0 m, its diameter is 1.0m and the collector is a four-sided pyramid, which has a side length of 28.5 m. A mathematical model is used to predict its performance. The model shows that the plant can produce a maximum theoretical power of 2 kW. Moreover, a CFD code is used to analyse the temperature and velocity distribution inside the collector, turbine and chimney at different operating conditions. Static calculations, including dead weight and wind forces on the solar updraft chimney and its solar collector, have been performed for the prototype. Mechanical loading and ambient impact on highly used industrial structures such as chimneys and masts cause lifetime-related deteriorations. Structural degradations occur not only from rare extreme loading events, but often as a result of the ensemble of load effects during the life-time of the structure. A Structural Health Monitoring (SHM), framework for continuous monitoring, is implemented on the solar tower. For the ongoing case study, the types of impacts, the development of the strategic sensor positioning concept, examples of the initially obtained results and further prospects are discussed. Additional wind tunnel tests have been performed to investigate the flow situation underneath the solar collector and inside the transition section. The flow situation in and around the SCPP has been simulated by a combination of the wind tunnel flow and a second flow inside the solar tower. Different wind tunnel velocities and volume flow rates have been measured respectively. Particle Image Velocimetry (PIV) measurements give some indication of the flow situation on the in- and outside of the solar tower and underneath the collector roof. Numerical simulations have been performed with the ANSYS Fluent to validate the experimental tests.

Optimization of effective parameters on solar updraft tower to achieve potential maximum power output: A sensitivity analysis and numerical simulation

In this paper, an axisymmetric 2-D numerical simulation and sensitivity analysis are carried out to obtain the potential maximum power output in a solar updraft tower power plant. The geometrical dimensions of the physical model of the studied solar updraft tower are based on the prototype installed at Manzanares. The sensitivity analysis is performed by utilizing the Response Surface Methodology. The effects of various parameters on the maximum potential power output of the solar updraft tower power plant are investigated and include the entrance gap of collector (2m≤CG≤6m), tower diameter (5m≤DT≤10m), tower height (200m≤HT≤220m) and collector roof inclination (0°≤θ≤5°). It is found that the potential maximum power output enhances with the tower diameter and height, and reduces as the entrance gap of collector is increased. Additionally, the sensitivity analysis revealed that the sensitivity of the potential maximum power output to (CG), reduces as (CG), (DT) and (θ) are increased. Moreover, its sensitivity to (DT) reduces as (DT), (θ) and (HT) are increased but increases with (CG). It is also found that to maximize the potential maximum power output, the effective parameters must have the values of CG=2m, DT=10m, HT=220m and θ=0°.

Thermal performance of a transpired solar collector updraft tower

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.

A Review of the Hybrid Solar Chimney and Water Desalination Systems for Simultaneous Production of Electricity and Fresh Water

This paper provides an overview of the operation principles and characteristics of a novel solar energy sourced power generation system called solar chimney power plant (SCPP) or solar updraft tower (SUT). The discussion includes the physical concept, historical development, characteristics and operational feasibility, as deduced by previous researches and case studies. It also discusses the commercialization of this technology and the continuous efforts aimed at integrating SCPP with water desalination technologies (WDT). Consequently, the authors concluded that there is a significant prospect of integrating SCPP with liquid desiccant system (LDS) for the purpose of efficient simultaneous production of electricity and fresh water.

Tracking collector consideration of tilted collector solar updraft tower power plant under Malaysia climate conditions

SUPP (Solar Updraft Tower power plant) is a technology in the power generation sector. The power productivity and efficiency represent important performance characteristics of SUPP. In the present work a mathematical model was developed to estimate the performance of SUPP based on tracking solar collector consideration in Malaysia. The objective is to verify the suggested model and to optimize the slope angle of tilted tracking solar collector. Basically, the hourly solar data were analysed considering solar azimuth angle for tracking case calculation to determine the solar energy incident on the collector. Then, the useful energy gain was calculated based on heat transfer relations. The model was validated with experimental work and well agreement was achieved. Results revealed that the SUPP of slope collector angle of 10° can produce higher power generation over the whole the year. Also, the tracking solar consideration enhanced the performance characteristics especially the power productivity by around 3.5 kW over that of fixed collector. The maximum collector and SUPP efficiencies of 51% and 0.165% respectively were obtained.

A review of convective and artificial vortices for power generation

Thermal energy transfer in the atmosphere occurs from a high temperature zone to a low one by means of convective vortices where mechanical energy is produced. There are two ways of driving vertical flow in the core of a vortex: (1) by the direct action of buoyancy acting on hot air and (2) by producing a vertical pressure gradient along the axis of a vortex because of core development involving the lateral spread of the vortex with height. In particular, it indicates that the intensity of convective vortices depends on the depth of the convective layer via thermodynamic efficiency, the enthalpy perturbation across them, and the existence of sources of vorticity. The atmospheric vortex engine (AVE) is a device for producing an artificial vortex. The operation of AVE is based on the fact that the atmosphere is heated from the bottom and cooled at the top. By artificial vortex generation, it is aimed to eliminate the physical solar updraft tower and reduce the capital cost of solar chimney power plants. This paper reviews natural convective vortices and vortex creation via physical principles of vortex generation. Vortex analysis and modelling are presented. Furthermore, a new model of a solar vortex engine (SVE) is proposed and discussed. An idea on utilizing the solar energy as the heat source for establishing the vortex and operating the SVE model is adopted. The SVE model is feasible and promising for electrical power generation.