An Experimental Study of Flat Radial Fresnel Len Solar Collector for High Temperature Thermal System

The largest quantity of fossil fuel is used for power generating process nowadays, which release enormous of carbon dioxide and other defilement to the environment. More significantly, fossil fuel will disappear from our planet in the near future. In order to save our environment together with develop our civilization sustainably and less harm to living things, humans are exploring new source of substitute clean energy and solar energy is renewable which can serve as a sustainable energy source. Moreover, it will significantly become a crucial part of the future energy structure. Because of the advantages of flat radial Fresnel lens such as small volume, light-weight, mass production with low cost, it recently have been one of the best choices in the field of concentrated solar energy applications. This research aims to design and build the flat radial Fresnel lens collector with solar tracking system using in high temperature solar energy thermal system. The 9 pieces of 40×40 cm with 230 mm focus length of Fresnel lens are used for the sunlight concentration to the focal point. The temperature at the focal points are measured by the data logger and Programmable Logic Controller (PLC) is used for controlling stepping motors in the sun tracking system. The working fluid used in the experiments was water has a volume of 30 liters and flow rate of 3 l/min. beside, water circulation system. The result of the experiments which collected between 11.00 A.M. – 02.00 P.M. Beginning, the average temperature which measured at 11.00 A.M. is 24C and the average maximum temperature is 42C at 2.00 P.M., which is able to generate the thermal power at 2,240 kJ. The rate of heat transposition is at 207.41 W/h and average efficiency is equal to 6.2% at average solar radiation value is 978 W/m during 3 hrs. Operating time at the average atmospheric temperature of 21C. The performance of solar concentrator which depend on many factors such as reflection of solar intensity, sun beam, mechanism and controller of the sun tracking accuracy of sun path.

necessitated an urgent search for alternative energy sources to meet our demands for the immediate future and for generations to come. Solar energy has the greatest potential of all the sources of renewable energy [2]. This energy is the enormous power which is fallen and given the energy at 1367 W/m 2 [3] by average. Using solar energy can be inevitable when other energy sources are nearly shortage. Thus, it would be a great idea if we could produce our own energy and may not need to buy energy from the others for the better future of the word.
Francia and more, [6,7,8] they were designed a one and two axis microprocessor based sun tracking device for using in PV f at plate solar panels or with parabolic ref ectors. It was optimally tilted around one axis and controls the azimuth angle with another axis. This work showed that elevated temperatures could be reached using such systems. DAVID et al., [9] who evaluates Compact Linear Fresnel Ref ector (CLFR) concepts suitable for large scale solar thermal electricity generation plants. Yabe et al., [10] they had developed a solar-pumped laser system with 7%-9% slope eff ciencies. The solar-energy-pumped laser with Fresnel lenses system. A Fresnel lens (2 m ×2 m, f = 2000 mm) was mounted on a two-axis sun tracker platform and focuses solar radiation toward laser cavity. and W.T. Xie et al., [11] who study of solar energy concentration technology using Fresnel lens is an effective way to make full use of sunlight. All research and development works suggest that Fresnel lens solar concentrators will bring a breakthrough of commercial solar energy concentration application technology in the near future.
The research team by the current authors has challenged the development and design of the flat radial Fresnel lens collector with solar tracking system to concentrate solar radiation combining at absorbed radiation tube which is located at the focal point of the flat radial Fresnel lens. The novel system design essentially accomplished a goal of highly safe and eff cient solar heating and heat storage. This model can be developed for further research as the appropriateness of the model relies on the efficiency of the heat energy such the accuracy of model, the sun mission, controlling and driving mechanism and wind speed. As a result, this paper is aimed to study the design and creation of prototype of the flat radial Fresnel lens collector with solar tracking system.

A. Basic concept of Fresnel lens
The Flat Fresnel lens are shaped like a dart board, with concentric rings of prisms around a lens that's a magnifying glass. All of these features let them focus scattered light from the Sun into a tight beam. The flat radial Fresnel lens is a shape which can reflect sunlight or radiation where is incident parallel to the axis of the radial Fresnel lens into another (the focus). They are used in Thermal Concentrated Solar (CSP) and Low concentration PV applications, as shown in Fig. 1. Thermal efficiency of the solar collector which influence on the adjustment in temperature of focusing collector is consists of the heat transformation rate of fluid flow within the pipe is water which is The heat transfer (Q u ) was calculated from temperatures.
The heat energy (q) was calculated from temperatures.
The efficiency (η) of the solar concentrator is:  hours. Finally these results will be plotted to find the relationships.

A. Result of solar radiation with time
This experiment was conducted in April-May by collecting data every 1 minute for an average time of one hour from 11:00 A.M. to 2:00 P.M. for three hours. The latter is choosing the results in any day with a clear sky and sunny throughout the day. The solar radiation is shown in Fig. 5.  T1  T2  T3  T4  T5  T6  T7  T8  T9  According to Fig. 6, it illustrates the comparison between temperatures with time at different positions.
The graph show that temperatures each day are similar at the same time and the temperatures will reach a peak at 2:00 P.M. The beginning average temperature which measured at 11.00 A.M. is 24°C and the average maximum temperature is 42°C at 2.00 P.M. as shown in Fig. 7 at volume of water 30 liters and flow rate of 3 l/min. While the average temperature of the ambient temperature is 21 °C . T1  T2  T3  T4  T5  T6  T7  T8  T9 Temp.  T1  T2  T3  T4  T5  T6  T7  T8  T9  The experiment data as shown by the line graph in Fig. 8 and the contour chart in Fig. 9, the solar radiation intensity during the day are expressed the temperatures at focal of Fresnel lens in Fig. 8 and the values of the color contour in Fig. 9 are similar to the values of the solar intensity and temperatures in Fig. 6. As a result, The combined heat power at flow rate 3 l/min and volume of water 30 liters will obtain the higher heat power and given power of heat by average 2,240 kJ at flow rate of 3 liters per minute and the rate of heat transposition is at 207.41 W/h.

III. CONCLUSIONS
The 9 flat radial Fresnel lens with a focal length of 230 mm and area of 40×40 cm 2