On the Influence of Collector Size on the Solar Chimneys Performance

Performance of solar chimney power plant system is highly influenced by the design geometries. The collector size is logically enhances the solar chimney performance, but the trend of enhancement is not yet investigated. In the present work, experimental and numerical investigations have been carried out to ascertain, in terms of qualitative and quantitative evaluation, the effect of the collector diameter. Daily thermal efficiency has been determined at four different collector diameter. Two different collector diameters, 3.0 and 6.0 m, have been investigated experimentally, and then scaled up, to 9.0 and 12.0 m, by numerical simulation using ANSYS-FLUENT®15 software. Results demonstrated that collector diameter has effectively influenced the system performance. Larger collector diameter imposed increase in the velocity, temperature and the daily average thermal efficiency of the system. From the experimental results, increasing the collector diameter from 3.0 to 6.0 m has increased the daily average thermal efficiency of the collector from 9.81 to 12.8. Simulation results at 800 W/m2 irradiation revealed that the velocity in the chimney have increased from 1.66 m/s at 3.0 m collector diameter to 2.34, 2.47 and 2.63 m/s for 6.0, 9.0 and 12.0 m collector diameters, respectively

Removal of non-CO2 greenhouse gases by large-scale atmospheric solar photocatalysis

Large-scale atmospheric removal of greenhouse gases (GHGs) including methane, nitrous oxide and ozone-depleting halocarbons could reduce global warming more quickly than atmospheric removal of CO2. Photocatalysis of methane oxidizes it to CO2, effectively reducing its global warming potential (GWP) by at least 90%. Nitrous oxide can be reduced to nitrogen and oxygen by photocatalysis; meanwhile halocarbons can be mineralized by red-ox photocatalytic reactions to acid halides and CO2. Photocatalysis avoids the need for capture and sequestration of these atmospheric components. Here review an unusual hybrid device combining photocatalysis with carbon-free electricity with no-intermittency based on the solar updraft chimney. Then we review experimental evidence regarding photocatalytic transformations of non-CO2 GHGs. We propose to combine TiO2-photocatalysis with solar chimney power plants (SCPPs) to cleanse the atmosphere of non-CO2 GHGs. Worldwide installation of 50,000 SCPPs, each of capacity 200 MW, would generate a cumulative 34 PWh of renewable electricity by 2050, taking into account construction time. These SCPPs equipped with photocatalyst would process 1 atmospheric volume each 14–16 years, reducing or stopping the atmospheric growth rate of the non-CO2 GHGs and progressively reducing their atmospheric concentrations. Removal of methane, as compared to other GHGs, has enhanced efficacy in reducing radiative forcing because it liberates more °OH radicals to accelerate the cleaning of the troposphere. The overall reduction in non-CO2 GHG concentration would help to limit global temperature rise. By physically linking greenhouse gas removal to renewable electricity generation, the hybrid concept would avoid the moral hazard associated with most other climate engineering proposals

Type and quality of energy and water in a tropical hospital

A hospital is considered an energy gobbler and a water consumer. The energy and water go for many activities in hospital system. HVAC that includes wet cooling tower is the main energy and water consumer in a hospital due to its continuous operation. Conservation of both resources partially depends on the way nexus is managed at the end user. Mapping the energy and water in term of type and quality is proposed as the starting point in managing both as nexus. This article focuses on that part in purpose of integrating energy and water system in a hospital. SUTH, a 120 beds hospital located in tropical area in Thailand that operates daily with 146 m3 water and 1.5 MW of electricity becomes the case of the study. The input and output of energy and water of each subsystem are exposed in addition to subsystems that are described in some different methods. The results show flows of energy and water as by-product that can be used for other systems. Radiology and HVAC release very low enthalpy heat that could not be managed for other utilization, but hemodialysis releases very low heat that is used for its own process. Autoclaves can releases heat that be used for laundry and its own pre-heating. HVAC release brine and distilled water through blow down system and condensation respectively. Electricity is very dominant energy supply of the hospital