Experimental Study of Concentrated Solar Power on Heat Feed Water Heaters in Steam Power Plants in Iraq

For generating power, solar energy is counted a good exporter. Iraq is located in a hot zonewith latitude from 32 degree N to 36 degree N. In Iraq, the average solar radiation is about 7kilowatt hours / day.In this work, central receiving tower was used to obtain steam using the available solar energyin summer and winter. To heat the feed water heater of South Baghdad Electrical Steam PowerPlant, steam utilization for this purpose. In the project, manufacturing the central receivertower, which is consisting of 150 mirrors fixed upon 75 manual tracking heliostats arranged forutilization the solar radiation concentrated on the central receiving tank (CRT). Pipes systemswere used for hot water or steam exits from receiver. In this study, the central receiver tank(0.5m*1m) was filled with 157 liter of water. The experimental work was run for one yearfrom June 2015 – May 2016. The outlet temperature of water from central tower receiver wassteam for (July and August 2015) and hot water with high temperature for other months of theyear. The results obtained from our system, solar shares for heating the feed water heater ofSouth Baghdad Electrical Steam Power Plant up to 1.86 % and an annual average of 1.03%.Temperature, power concentration factor and system efficient are greatly influenced by thenumber of heliostats used. A sample of calculations is used to evaluate the mathematical dataof hot water and steam temperatures obtained from this study. These values are approximatewith experimental data when compared together.


Introduction
Solar energy is most abundant renewable power source which is readily available anywhere the sun shines [1]. Solar energy is easy to collect and use with relatively lower overall cost comparing with the other renewable energy sources [2]. Even though solar energy has benefits of being nonpolluting and minimal environmental impact, it does have limitations such as intermittent energy supply as the sun shines only at daytime, and energy conversion efficiency can be low [4]. Many applications of It is possible to obtain hot water, steam, heating and cooling by using clean energy, which is solar energy. Solar energy can be converted into electric energy or thermal energy. Flat panels and concentrators can be used to obtain electrical energy using high solar radiation density. [3] For this work, 3-sizes for central receiver tanks that utilizing in this work that various

Central Receiver Tank (CRT):
The CRT was manufactured with (50cm) D and (100cm) L. Standing on top of a manufacturing structure. Four piping perforation were manufacturing for connecting piping, as shown in Figure (1).

Tower Steel Structure:
The structure of the tower was manufactured locally in the form of a letter from steel metal with the measurements (60*60*5) mm that the height of the tower is 2 meter.

Pipes Network:
The layout of piping system consists of a set of galvanized iron pipes that provide water with D 1.27cm, with pump that connect the water from the water storage tank to the CRT. Also plastic pipes with 1.27 cm D for provide

No.30-(3) 2021 Journal of Petroleum Research & Studies (JPRS)
E140 the water from CRT to exchanger and set of piping 1.27cm to return the hot water from heat exchanger to central receiver tank.

Heliostats:
Heliostat consists of a number of mirror, which is about 50 and the dimension is (50×50) cm hold upon the steel structure. The steel structure consists of rectangular frame (50×100) cm supported at height 65cm on checker plate (60×60) cm. The frame is manufacturing from aluminum with two plates (50×50) cm.

Heat exchanger:
A feed water heater in steam power plant for heating the water before entering the boiler by using solar energy was used. The test section is made of one pass shell and tube heat exchanger which is Bowman type(3740-6), having dimension of(1200 mm) L overall ,(1000 mm) L eff , which contain (52) copper tube of (11 mm) ID and (13.5 mm) OD. The tubes are arrangement with a triangular staggered. The clearance between two adjacent tubes is (1.5 mm).

Measuring devices:
(1) Rotameter: two vertical variable area rotameters are used to measure the flow rates of the hot and cold water. For the hot and cold water circulation, a flow meter of (50 -420) LPH range is used.
(2) Temperature: for measuring temperature a thermocouples type K, and then transferred data into lap-top by using 1G-SD Card which connected with data logger system (Lutron-Model BTM-4208SD). Water temperature and the ambient temperature every hour are measured.

Mathematical Formulation
The useful energy delivered by the collector is given by the energy balance Equation (1). (1) The useful heat produced by concentrator is given by: The temperature of the water for each hour can be estimated by substituting equation (2) in (1) which results represented as: The concentration of solar radiation is achieved by reflecting or refracting the flux incident on an aperture area onto a smaller receiver/absorber area .
The heat gained and a heat loss from the central receiver tank is explained by Figure (2).

Fig. (2) The energy that loss from central receiver tower.
The thermal efficiency of a concentrator system is given by: In this equation: The heat transfer coefficient (h) can be determined by using these equations: Monthly and annual contribution of solar collector system is calculated by using F-chart method:

Results and Discussions
The mathematical models in this work and experimental measurements for the CRT are summarized in Table (1) as shown below.

Monthly and Annual Solar Energy Contributions
Monthly and annual solar energy contribution for energy required to heat the feed water heater in the South Baghdad Thermal Electrical Power Plant were estimated by using the equations of F-chart method. The heat supplied by solar collector system that exists in Table (3). From South Baghdad Thermal Electrical Power Plant the thermal load was used is 5Mw (180000MJ).

No.30-(3) 2021 Journal of Petroleum Research & Studies (JPRS)
E145  From the experimental work, the temperature of the exit fluid that recorded every hour daily was obtained. These data were calculated from the equations that mentioned in mathematical formulation. The calculated temperatures were higher than that measured (12%) percentage error. This was because of many reasons, such as diffusing the solar radiation, cloudy, dusty and heat losses because there is no insulation used, as shown in Figures (3-16).

5.
The following conclusions are drowning: 1. The contribution of solar energy to heat feed water heater is increased by increasing the surface area of mirrors 2. Increasing the volume of water decrease the exit temperature but gives better contribution because of the high flow rate.
3. The highest exit temperature for water occurred in (June, July and August) due to the high intensity of solar radiation. 4. Although the sharing of solar energy in winter season is low, the load in this season also low, so the sharing of solar energy will be acceptable. 5. It can be design the concentrating solar collector in the form of groups to reduce the size of the receiver.