The recent studies on thermal performance enhancement of the flat plate solar air collectors are critically reviewed primarily regarding the absorber surface modifications, multiple-passes of air, porous absorbers, air-jet impingement on absorber surface, integration of heat storage materials, dual-purpose hybrid collectors and hybrid photovoltaic/thermal solar collectors. The formation of a laminar viscous layer over the surface causes poor heat transfer to airflow. Enhanced heat transfer surface area and residence time of air are vital factors for heat transfer augmentation using baffles, turbulators, roughness, and obstacles. The streamwise pitch ratio of the jet plate has the maximum contribution to friction and, subsequently, the heat transfer. The thermal efficiency of finned and porous absorber varies from 71.4% to 93%. The integration of phase change material and fins with solar air collector enhance daily thermal efficiency by 0.1%–4%, increasing further with honeycomb and porous structures. The application of agriculture waste as sensible heat storage material is an effective alternative to replace conventional materials. Electrical and thermal efficiencies of hybrid solar collector increased with the addition of thermal energy storage by 9% and 5%, which further enhanced by 3% with the addition of fins into the phase change materials. Thermo-economic performance of the dual-purpose collector and hybrid photovoltaic/thermal solar air collector is comparatively cost-effective with environmental benefits. This review article provides an insight into the recent critical findings on the thermal performance enhancement of the flat plate solar air collector to stimulate further developments towards the betterment of sustainable development.

A review on recent developments in thermal performance enhancement methods of flat plate solar air collector

Increasing household solar energy penetration through load partitioning based on quality of life: The case study of Nigeria

Cooling buildings in summer is one of the main environmental problems for architects and occupants in many hot dry countries. The summer temperature during these countries reaches peaks of more than 40°C in some. Mechanical air conditioners can solve the problem, but they put a heavy strain on the electricity consumption. Egypt in general has rich sunny and clear skies. Therefore, these conditions encourage to enhance evaporating with natural ventilation and save energy. This paper develops an integration of direct evaporative cooling tower with a solar chimney multi-zone thermal ventilation model. Simulation is done using commercial couple multi-zone airflow under COMIS-TRNSYS software (Madison, WI, USA) to assess natural ventilation and indoor thermal comfort. The results show that the system generates 130.5 m 3 /h under the effect of solar radiation only and minimum 2 ACH without pressure coefficient which is considered the minimum requirement of ACH. The findings show that the new integrated system interacts with the building envelope and weather conditions to achieve a decrease in indoor temperatures that reach 10°C to 11.5°C compared to outdoor temperatures.

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Integration of evaporative cooling technique with solar chimney to improve indoor thermal environment in the New Assiut City, Egypt

Optimal electricity development by increasing solar resources in diesel-based micro grid of island society in Thailand

In this paper, the solar radiation on diversely oriented surfaces and optimum tilts for solar absorbers were assessed. The KT solar radiation model was coded in the MATLAB-based environment to compute the monthly solar radiation values. Seven years data of monthly average daily solar radiation on a horizontal surface in Bangi, Malaysia (latitude = 3° N) was adopted as input in the simulation programme, and the results were compared with the local optimum tilt angle at solar noon and other solar radiation model. The contour mappings of solar irradiation at various orientations in 12 months were presented. Results showed that the surface tilted at ≤20° could intercept a relatively high solar intensity, which was less sensitive to the variation of azimuths with average insolation deviation of 11.82%. The monthly optimum tilt angle altered throughout the year, ranging from -24° (in equator direction) to +22° (in north direction). The estimated annual optimum slope, 1.4° facing to the equator, was close to local latitude. Based on the seasonal analysis, the north-facing surface was able to intercept higher daily average solar radiation energy compared to south-facing plane. The optimum angles for seasonal south- and north-facing surfaces were found to be 14.4° and 14.8°, respectively, with a tolerable slope deviation of ±5° from the optimal values in the present work.

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Assessment of solar radiation on diversely oriented surfaces and optimum tilts for solar absorbers in Malaysian tropical latitude

This work optimises the collection of solar energy within the period of its availability in order to increase its utilisation and also to enhance performance of heating systems that depend on it through appropriate determination of optimum solar collector tilt angles. Buoyancy-induced flow equation in solar collector pipe was established by continuity, energy and Navier–Stokes equations in cylindrical coordinates. Fundamental solar radiation equations were programmed to determine optimum tilt angles in locations within latitudes 1° and 14°. A set of data recorded from a pryanometer located on latitude 6.45° north of the equator was used to generate average monthly radiation over the latitudes. Graphs obtained from latitude 6° and 13° data were analysed to investigate solar radiation on some tilt angles. The optimum tilt angles for solar heating for periodic tracking of the sun in the region within latitudes 1° and 14° were predicted as ∅ + 25° for November, December and January; ∅ + 15° for February, September and October; ∅ − 15° for August; ∅ − 25° for May, June and July; and ∅ for March and April. The results of this work confirmed that solar radiation on tilted surface increases with latitude.

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Oyewola M Olarenwaju

Papers

Determination of optimum tilt angles for solar collectors in low-latitude tropical region