Major Project Report File.docx

1. HISTORY: In 1903, Spanish colonel of the Isadora Cabanyes first proposed a solar chimney power plant in the magazine la energia electrica.  One of the earliest descriptions of a solar chimney power plant was written in 1931 by a German author, Hanns Gunther.

Beginning in 1975, Robert E. Lucier applied for patents on a solar chimney electric power generator; between1978 and 1981 these patents (since expired) were granted in austrailia, Canada, Israel, and the USA. For many years Professor Jorge Schlaich and his team at Schlaich bergermann and Partner (SBP) of Stuttgart, Germany, have been vitally interested in large scale solar energy applications. In the late 1970’s and early 1980’s the team developed a detailed proposal for a Solar Tower. An experimental 50 kW capacity pilot plant was then built to SBP’s design in manzanares, spain, some 50 km south of Madrid, which collapsed in a sand storm after six years.

2. SET UP OF MODELLED SOLAR CHIMNEY

2.1 ASSUMPTIONS: The main assumptions used in the present study are summarized in table (1).

Parameters

values

Chimney height (Hch)

7 feet

Chimney diameter (Dch)

90 mm

Collector diameter (Dcoll)

5 feet

Distance from ground to the cover

(Hcoll)

2 feet

Solar irradiance (G)

198.32 W/m2

Collector efficiency factor (F’)

-

Ambient temperature (Tamb.)

27 C

2.2 Total Efficiency of SCPP Total efficiency 𝜂𝑡𝑜𝑡 is determined here as a product of the individual components efficiencies: 𝜂𝑡𝑜𝑡 = 𝜂𝑡𝑢𝑟 𝑥 𝜂𝑐𝑜𝑙𝑙 𝑥 𝜂𝑐h ---(1) Where, 𝜂𝑐𝑜𝑙𝑙 is the efficiency of the collector, in other words the effectiveness with which solar radiation is converted into heat, 𝜂𝑐h is the efficiency of the chimney and describe the effectiveness with which the quantity of heat delivered by the collector is converted into flow energy, 𝜂𝑡𝑢𝑟 stands for the efficiency of the wind turbine generator. For example, with a chimney height of 1000 m and standard conditions for temperature and pressure, the chimney efficiency 𝜂𝑐h achieves the maximal value of 3 %. Considering collector efficiency (𝜂𝑐𝑜𝑙 ) of 60 % and turbine efficiency (𝜂𝑡𝑢𝑟 ) of 80 %, the total system efficiency (𝜂𝑡𝑜𝑡) reaches 1.4%, as shown below: 𝜂𝑡𝑜𝑡 = 𝜂𝑡𝑢𝑟 𝑥 𝜂𝑐𝑜𝑙𝑙 𝑥 𝜂𝑐h = 0.8 x0.6 x 0.03 x 0.014 = 1.4%

2.3 Solar Collector Modeling The earth itself, which is covered by glass or other transparent materials, acts as a heat absorption layer (collector). The periphery of the solar air collector is open to the atmosphere, and its center is connected with the base of the solar chimney. A solar collector converts available solar radiation (G) onto the collector surface Area (Acoll ), into heat output. Collector efficiency (𝜂𝑐𝑜𝑙 ) can be expressed as a ratio of the heat output of the collector as heated air (𝑄 ) and the solar radiation (G) measured in W/m2 times 𝐴𝑐𝑜𝑙𝑙 . 𝜂𝑐𝑜𝑙𝑙 = 𝑄 /𝐺𝐴𝑐𝑜𝑙𝑙………………………………..(2) Heat output 𝑄 under steady conditions can be expressed as a product of the mass flow 𝑚 , the specific heat capacity of the air Cp and the temperature difference between collector inflow and outflow (𝛥𝑇 = 𝑇𝑜𝑢𝑡 − 𝑇 𝑖𝑛).The energy balance equation is given below: 𝑄 = 𝑚 𝐶𝑝𝛥𝑇 = 𝜏𝛼 𝐴𝑐𝑜𝑙𝑙 𝐺 – 𝛽𝛥𝑇𝑎 𝐴𝑐𝑜𝑙𝑙 = 𝐺 𝐴𝑐𝑜𝑙𝑙 𝜂𝑐𝑜𝑙𝑙 ……………….(3) Where, 𝛥𝑇𝑎 is the difference between the mean collector plate temperature 𝑇𝑝𝑚, and ambient temperature (𝛥𝑇𝑎 = 𝑇𝑝𝑚 − 𝑇𝑎𝑚𝑏) And, 𝑚 is the mass flow rate of hot air passing through the solar chimney, and can be calculated using the following equation. 𝑚 = 𝜌𝑎𝑖𝑟 𝐴𝑐h 𝑉𝑐h……………………..(4) Substituting by 𝑛𝑑 𝑚 from equations 2 and 3 into equation (1) gives: 𝜂𝑐𝑜𝑙𝑙 = 𝜌𝑎𝑖𝑟 𝐴𝑐h 𝑉𝑐h 𝐶 (𝛥𝑇) / 𝐺𝐴𝑐𝑜𝑙𝑙…………………………… (5) The efficiency of the solar collector can also be expressed, using𝑄 = (𝜏𝛼) 𝐴𝑐𝑜𝑙𝑙 𝐺 − 𝛽 𝛥𝑇𝑎 𝐴𝑐𝑜𝑙𝑙 . From equation (2) and substituting into equation (1) gives: 𝜂𝑐𝑜𝑙𝑙 = (𝜏𝛼) − 𝛽𝛥𝑇𝑎 /𝐺……………….(6) By equating equations (5) and (6), the link between air speed at the collector outflow velocity𝑉𝑐𝑕 and temperature rise (𝛥𝑇 = 𝑇𝑜𝑢𝑡 − 𝑇 𝑖𝑛) can be expressed as: 𝑉𝑐h = (𝜏𝛼 𝐴𝑐𝑜𝑙𝑙 𝐺 − 𝛽𝛥𝑇𝑎 𝐴𝑐𝑜𝑙𝑙)/ 𝜌𝑎𝑖𝑟 𝐴𝑐h 𝑝 𝛥𝑇……….(7) The above equation is independent of collector roof height because friction losses and ground storage in the collector are neglected. where, 𝐴𝑐h is the cross-sectional area of the solar chimney, 𝐴𝑐𝑜𝑙𝑙 is the area to receive solar radiation, G stands for solar irradiance measured in W/m2, (ατ) represents the product of absorbance and transmittance of the solar collector, β is the heat loss coefficient of the solar collector, 𝜌𝑎𝑖𝑟 is the density of air at the outlet of the solar collector. To evaluate collector performance, it is necessary to know the mean fluid and mean plate temperatures, which could be estimated as follows [1,4, 26].

𝑇𝑓𝑚 = 𝑇 𝑖𝑛 + 𝑄 (1 − 𝐹′′) / 𝐴𝑐𝑜𝑙𝑙 𝛽𝐹𝑅 ………(8) 𝑇𝑝𝑚 = 𝑇 𝑖𝑛 + 𝑄 (1 − 𝐹𝑅) / 𝐴𝑐𝑜𝑙𝑙 𝛽𝐹𝑅 …………(9) Where, the heat removal factor, 𝐹𝑅, can be expressed as, 𝐹𝑅 = (𝑚 / 𝐶𝑝 𝐴𝑐𝑜𝑙𝑙 𝛽) (1 − 𝑒𝑥𝑝 (𝐴𝑐𝑜𝑙𝑙 𝛽𝐹′/ 𝑚 𝐶𝑝))……………. (10) Where, F\is the efficiency factor of the solar collector, F\\ is the collector flow factor which is given as, 𝐹′′ = 𝐹𝑅 / 𝐹′ ……………………………….(11) The mean fluid temperature is required to solve the model, which could be found from the arithmetic mean of the inlet temperature and the mean plate temperature. 𝑇𝑓𝑚 = (𝑇𝑖𝑛 + 𝑇𝑝𝑚) / 2…………………………(12)

2.4 Solar Chimney Modeling The efficiency of the chimney, i.e. the conversion of heat into kinetic energy is determined by the ambient temperature at the ground level and the height of the chimney. The chimney efficiency is expressed as follows: 𝜂𝑐h = 𝑊𝑡𝑜𝑡 / 𝑄 = 𝑔𝐻𝑐h / 𝐶𝑝 𝑇𝑎𝑚𝑏………………………… (13) Where, 𝐻𝑐h is the height of the chimney (m), g is the gravity (m/s2), 𝐶𝑝 is the air heat [J/kg·K] and 𝑇𝑎𝑚𝑏 is the ambient temperature [K]. As shown in eq.(13) it is clear that the chimney efficiency is only dependent on chimney height. While, flow speed, and temperature rise in the collector are not included. Thus the power contained in the flow 𝑊𝑡𝑜𝑡 from eq.(13) can be expressed as follows with the aid of Eqs.(13) : 𝑊𝑡𝑜𝑡 = 𝜂𝑐h 𝑄 = 𝑔𝐻𝑐h / 𝑇𝑎𝑚𝑏 𝜌𝑎𝑖𝑟 𝑉𝑐h 𝐴𝑐h (𝑇𝑜𝑢𝑡 − 𝑇 𝑖𝑛)……..(14) The pressure difference, 𝛥𝑃, which is produced between the chimney base(collector outflow) and the surroundings, is calculated by, 𝛥𝑃 = 𝜌𝑎𝑖𝑟 𝑔𝐻𝑐h (𝛥𝑇/ 𝑇𝑎𝑚𝑏) …….(15)

3. Design of Experiment 3.1 SpaceMeasurement Available Space: Classroom of 15ft 5” (whiteboard) by 15ft 10” [About 4.7m by 4.826m] Classroom height of 11ft available [3.3528m]

3.2 Procedure • Arrange the physical setup • Note initial values (Tambient; TTop, TBottom; vTop, vBottom; VTurbine, ITurbine) • Turn on the heat lamps and start the timer. • Record 1st reading at 15 minutes • Take interval readings every 15 minutes.

3.3 Bill of material for Mechanical Structure S/N 1. 2. 3. 4. 5. 6. 7. 8.

ITEM Chimney Turbine Conducting wires Toughened glass Silicon glue and glue gun Cardboard sheet Measuring instruments Metallic stand

QUANTITY 1 1 As per required 5 1 pack 5 As per require 1

4. Fabrication 4.1

Fabrication of Chimney

A metallic cone stand is used as the base of our prototype solar chimney. Holes were drilled at equal spacing for securing of support wires. Rectangular sections of the cone were cut off to allow for air flow from under the apron to the chimney. A long PVC pipe was used as our chimney. These are joined together and air-sealed using duct tape.

4.2

Fabrication of Ground

Roof concrete act as the “ground” of the entire setup. They are selected to be grey so as to prevent the ground from absorbing all the light (and thus, heat) as well as absorb sufficient amount of irradiation, allowing the air inside the apron to absorb more heat to create a larger temperature differential. To help identify the middle of the setup, a cross was made from four corners of the ground. After positioning the chimney, the point was marked for future reference.

4.3 Fabrication of turbine The turbine was made of a DC motor and an appropriately sized fan blade. After attaching the blades to our motor, the entire setup was attached to a frame support which is then hot glued to the insides of our chimney. The seven fan blade selected were 2.5” and 3” and were intended to fit our chimneys with inner diameter of 3” and 3.5” respectively.

4.4 Electrical setup With data that states the 7mW output of Solar Tower, the circuit was scaled small as our power output is predicted to be in the milliwatts range. Resistors of 0.25W rating were purchased as we do not need the higher power ratings for this experiment. A basic schematic as shown below connecting the motor generator M1 to a resistor load R1 is used, along with the measuring tools Ammeter and Voltmeter. A 10 resistor is used as R1. Alligator clips act as connecting wires between the various parts.

4.5

Fabrication of solar plate collector

For our collector, five pieces of toughened glass was bought. We then cut out a sheet of plastic, with an opening in the centre to fit over the chimney. Fishing lines were tied from the chimney base to surrounding stand to suspend the glasses, letting it act as our collectors.

5. SUT Experimental Setups

Given below are the images regarding our project setups:-

5.1 Turbine Fan

5.2 Modelled Setup

5.3 Dynamo

6. POTENTIAL OF SOLAR ENERGY IN INDIA

 About 5000 trillion kwh/year   

 

energy is incident over India’s land area. Most parts receiving 4-7 kwh/m2/day. 1% of land area is sufficient to meet electricity needs of India till 2031. Highest annual global radiation is received in Rajasthan (5.5-6.8 kwh/m2/day) and Northern Gujarat. Most of India has solar insolation above 1800kwh/m2/day. 250-300 clear and sunny days in a year.