Energy crisis is governing the country in the recent past. Many projects have been implemented by Government of India to solve the energy crisis. Even states like Tamilnadu is facing acute power crisis. Electricity is consumed more by the consumers for water heating and cooking purposes. To minimize the energy crisis, solar energy is used for water heating, cooking and other applications. Solar energy is used in two forms such as thermal (heat energy) and electrical applications (Photo voltaic – production of electricity from light energy) by human kind. The general phenomenon of concentrating type solar cookers is that they will receive all direct radiations from sun and focus it on to a particular point. At the point of focus (focal point), an absorber is placed to heat water and also to cook various food items. Such types of concentrating type solar cookers are in use for heating and cooking purpose over a long time.

Generally the concentrating type solar cookers have three major limitations such as frequent tracking adjustment of the reflector towards the direction of sun, deterioration of the reflecting surface with use and its relatively poor performance during windy days. In spite of these limitations, concentrating type solar cookers are used to achieve very high temperatures (above 200^oC) (1 – 4). For many industrial and commercial applications, working fluids of very high temperature (above 100^oC) are needed. In order to attain such high temperatures, it is necessary to increase the amount of radiation that falls on the absorber. This can be achieved by suitable reflectors which collect solar radiations over a large area and focus it on to a much smaller area (5, 6). It is noted that the reflecting area of the conventional concentrating type cookers made by experimentalists are not large. Recently MNRE (Ministry of New and Renewable Energy Sources), Govt. of India has given a specification of parabolic dish solar cooker of width 1.4 m for cooking application. Taking the above parameter into consideration, a new concentrating dish solar cooker has been deduced from an unused dish antenna for water heating and cooking purpose.

Nowadays, the usage of bigger sized dish antennas in India is greatly reduced due the centralized networking of cable channels, Direct to Home (DTH) type dishes and private single user cable connection etc. Many of such bigger sized dishes were kept idle (unused) by its users. It is called as e-waste. (Electronic waste) In this study, an attempt has been made to use such an unused dish antenna (e-waste) as dish solar cooker for water heating, oil heating and cooking purposes. Here an unused aluminium perforated dish antenna of width 6 ft. (1.8 m) is deduced as a dish solar cooker. The focal length of any dish antenna (dish type cooker) can be determined by an empirical formula which is given below. A black painted aluminium vessel is kept at the focal point for perfect usage. A thin aluminized foil is pasted on the perforated dish surface for perfect reflection.

A dish antenna of width 180 cm (6 ft.) with perforated aluminium sheet as the surface is modified as a dish solar cooker. By properly cleaning the surface with water, emery sheet, soap water and petrol, an aluminium foil is pasted with utmost care for higher reflectivity.

The focal length of the dish is determined by the following formula:

f = ( D * D ) / ( 16 * c )

Focal length = f , Depth = c, Diameter = D

The diameter of the dish (D) = 180 cm.

The depth of the dish from the center to extreme ends ( c ) = 9 cm,

By applying the above formula, the focal length is calculated as 90 cm.

By removing the unused Low Noise Booster (LNB – satellite signal receiver) from the existing unused dish antenna, a suitable arrangement is made to keep the absorber (cooking vessel) at the focal point. It is shown in Figures 1 & 2. A black painted aluminium vessel of diameter 20 cm is placed as the absorber at the focal point. This complete dish solar cooker set up is placed on a stand for tracking adjustment. The complete structure is shown in Figure 3. In order to qualitatively asses the degree of accuracy of the reflector surface, a photo graph of the dish solar concentrator is taken. It is seen from the Figure 4, that the entire radiations are falling at the bottom of the absorber (black painted vessel) giving the intercept factor of nearly one.

Figure 1. – Perforated Unused Dish Antenna

Figure 2. – Dish Antenna with Absorber Assembly

Figure 3. – Dish Cooker with Black Absorber while Operating

Figure 4. Focus of Entire Radiations at the Bottom of the Absorber

The performance of a concentrating type solar cooker is generally assessed by water heating tests (7 – 9). The following observations were made with the assumption that the vessel and water are heated to the same temperature and the shadowing effect of the absorber is neglected. We have carried out the water heating test and saturation test on this dish solar cooker on a bright sky day. Water heating test and saturation test for castor oil were taken by insulating and not-insulating the absorber (black painted aluminium vessel) to analyse the maximum temperature attained in each case and also to estimate the heat dissipation due to radiation to the surroundings. Insulation is done with plastic thermo cool material. Tracking is done on every 30 minutes for higher efficiency.

1.Total quantity of water in the aluminium vessel is 1000 cc. Water boiled in 15 min.
2. Total quantity of castor oil in the aluminium vessel is 1000 cc. Maximum temperature attained is 223^oC.
3. Measured solar intensity (direct radiation) was 1020 W/ m².
4. Aperture area of the concentrator is 2.54 m2 .
5. Average wind velocity at that instant is 20 – 30 Kmph.

Cooking tests have been performed to determine the time of cooking for various food items like Raw Rice, Dal and wheat rava. The values are presented in the Table 1.

Table 1. Cooking Tests for Various Food Items

An unused dish antenna of width 1.8 m (180 cm) has been converted as dish solar cooker. Its performance as a cooker has been analysed. It can be seen from Table 2, that 1000 ml of water was brought to boil in about 15 minutes. Further, it is studied that this type of cookers can be used for baking chapattis. The cooking times for various cooking materials are tabulated in Table 1. The time consumption is appreciably less. From Table 2, it can be observed that, the boiling temperature can be attained quickly when the absorber is insulated properly. The saturation test for oil predicts that temperature above 200^oC can be easily achieved with this type of cooker. (From Table 3) This is mainly due to the high optical efficiency of the concentrating type cooker. Figure 5 shows Water Boiling Experiment for 1000 cc of water (without & with insulation) and Figure 6 shows Saturation Test for Castor oil (without & with insulation).

Table 2. Water Heating Test

Table 3. Saturation Test for Castor Oil
 

Figure 5. Water Boiling Experiment for 1000 cc of water (without & with insulation)

Figure 6. Saturation Test for Castor oil (without & with insulation)

The design calculations for this type of concentrating type cooker are quite simple and conversion is also not a difficult one. Further, this type of concentrating type cookers can be easily modified with unused dish antennas which are kept at home as a useless material. Hence, it is concluded (Energy from Waste) that from an unused material, it is possible to convert a cooker for heating and cooking purposes.

Further investigation is under progress to have a dish solar cooker cum satellite signal receiver (Low Noise Booster) in a single dish antenna. Also the efficiency of this type of concentrator with other commercial type of concentrating type cooker is also under progress.