ABSTRACT
Small-scale concentrated solar power systems have a higher levelized cost of electricity than large-scale systems. Therefore, this study aims to evaluate small-scale concentrated solar power systems, which use thermal energy directly without having to produce electricity, with particular emphasis on the use of solar cooking. The sun’s rays are reflected using a huge number of mirrors and focused on a focal point (the target), in this study, the bottom of the cooking pot. The study encompasses three main parts: 1) the design and manufacture of a small-scale central receivers model for solar cooking; 2) the installation of an automated solar tracking system; and 3) the experimental studies. The area of the proposed model is 1 m2, while the heliostat area is 0.56 m2. For the tracking procedure, the astronomical almanac method was utilized to estimate the sun’s position; this technique is not affected by ambient conditions like clouds. Despite employing normal flat mirrors and conducting the tests in inclement weather (winter), the results were excellent and suggested a possible interest. A half-liter of water took 20 minutes to heat up to the point of starting boil, and 193°C was the oil’s highest measured temperature. This result can be improved by using high-absorptivity cooking pots and specialized mirrors such as Fresnel lenses. Efficiency for the water studies varied from 50% to 76%, where a half litter took only 18 minutes to get to the highest temperature, while for a half litter of oil, efficiency was 79%.
Nomenclatures
A | = | Heliostats area |
cp | = | Specific heat capacity |
DNI | = | Direct normal irradiation |
H | = | Cartesian coordinates |
H | = | Target height |
H | = | heliostat height |
m | = | Mass |
Nh | = | Number of mirrors |
q | = | Heat energy |
R | = | Perpendicular distance between the heliostat’s central points and the target |
T | = | Temperature |
t | = | Time |
Greek symbols | = | |
ε | = | Absorptivity of the mirrors |
= | Efficiency | |
Ψ | = | Second law efficiency |
∅ | = | Front angle |
λ | = | Target angle |
θ | = | Tower rim angle |
Abbreviations | = | |
amb | = | Ambient |
i | = | Initial |
f | = | Final |
eff | = | Effective |
opt | = | Optical |
Δt | = | Time increment |
SWH | = | Solar water heating |
Acknowledgements
Implementations of the experiments were carried out at the Department of Mechanical Engineering, Faculty of Engineering, Sabratha University. The author also gratefully acknowledges the bachelor’s students: E. Yousf and R. Melod for their contribution to conducting this work.
Disclosure statement
No potential conflict of interest was reported by the author(s).