(iii)
Community ( Scheffler ) Solar Cooker
The unique feature of this cooker is that it is possible to cook food
indoor using solar energy within the kitchen itself and can
cater to 40 to 50 persons.
Configuration
The cooker is of paraboloid type having primary and secondary
reflectors. The parabolic frame of the primary reflector is made of
metallic square tubes. The reflector is made of aluminium facet (plates / rods) in which reflecting mirrors of glass / acrylic /
polyester film are fixed to reflect the solar rays towards secondary
reflector placed inside the kitchen. Secondary reflector sheet /
mirror is so curved in shape that it reflects the incoming rays
towards the bottom of the vessel. The stand on which the reflector
frame is fixed is made of iron structure suitably painted. The
movement of the rotating support on which the frame is fixed is done
with the help of automatic tracking device. There is a pendulum clock
work device with provision for seasonal adjustment.
Working Principle
The 7 sq.m large reflector standing outside the kitchen reflects solar
rays into the kitchen through an opening in its north wall, while the
secondary reflector further concentrates the rays to the bottom of the
pot / frying pan which is painted black, to absorb heat faster and
better.
In view of high temperature (400° C) at focal point, the cooking rate
is significantly faster than that in other types of solar cookers. It
is possible to cook two meals a day in places where solar insolation
is good during most part of the year. It can cook almost all
traditional dishes including chappathis, poories, dosas etc. and
can eliminate use of conventional fuel like gas, electricity etc.
Potential for use:
-
Cooking in residential schools, institutions, ashrams
-
Cooking
in hotels, hostels, hospitals etc.
-
Cooking for industrial canteens
Economics
(Tentative)
-
Costs about Rs 50 000.
-
Subsidy
is 30% subject to a maximum of Rs 15000 for rural areas.
-
Use of this can save about 35 to 40 LPG cylinders per annum (Rs.12 000
per year). The payback period is 2 years with subsidy.
-
The metallic structures will last for 15 years and the reflecting
mirror for 5 years. O & M expenditure is about 2 to 3 % per annum.
Limitations
-
The kitchen wall should be
north facing
-
A single storey building is
preferred to avoid shadows.
-
It must be ensured that
there is no other buildings / structure / trees to cast shadow on
the reflector frame.
-
6 to 8 m distance should be
available from the kitchen’s north wall for installing the cooker.
Manufacturers
View the list of manufacturers
(iv)
Steam Cooking ( Parabolic concentrators )
Configuration
Solar steam cooking system can cook food for several thousand persons
at a time.
The system uses automatic tracking solar dish concentrators which
convert water into high pressure steam and consists of shell type
receiver made of mild steel, 35 cm in diameter, connected to two
concentrators on either side, which focus sunlight on both sides of
the receiver. Several such receivers are connected to a 12” dia header
pipe which is half-filled with demineralized water.
The receivers and
the header pipes are insulated to avoid any heat losses. Each receiver
is integrated with two pipes of 1 ½” and ½” diameter from inside,
which help in thermo-siphonic flow of water from receivers to header
and back. When the water gets heated in the receiver, it starts moving
up in the header through one pipe and the cold water from the header
starts coming into the receiver. The cycle goes on and a high pressure
steam is generated in the header pipe after some time.
Working of the System
Before the system is put into operation in the morning, all the header
pipes are half-filled with water using a high pressure reciprocating
pump. All the concentrators are then arranged manually in the
direction of the sun with the help of a central tracking arrangement.
Once this is done, all the concentrators then track the sun
automatically with the help of a small DC motor run by PV panel. A
timer relay is used for adjustment of tracking time relay.
The steam pressure starts building up in the header pipes immediately
and is sufficient to deliver the steam to the kitchen in an hour or
so. This steam can be drawn any time in the day even at the time of
power failure as the feed water pump is not required to feed water and
push the steam. An oil-fired boiler can be connected to the system to
ensure that required steam is always available in the kitchen if the
sun shine on a particular day is not adequate.
Potential for Use
MNRE Assistance
For
2007-08, 50 % of the cost of the system subject to a maximum of
Rs.5,000 per sq.m of dish area for non-profit making
institutions / organisations and 35 % of the cost of the system
subject to a maximum of Rs.3,500 per sq.m of dish area for
commercial / industrial organisations (subject to changes).
Limitations
The system will be successful only in places where exclusive staff are
available for operation and maintenance. These places could be
religious ashrams, temples, gurdwaras, army canteens etc.
It has to be hooked up with conventional steam generating system to
make it reliable under all climatic conditions.
Economics (Tentative)
-
Cost of cooking system for 1000 people is about Rs.80 lakhs.
(Special workshop facilities are required at site for installing the
system besides back up boiler and cooking utensils.)
-
MNRE provides
capital subsidy upto 50 % of the cost.
-
Saving in fuel
cost (furnace oil) would be about Rs.20 lakhs / year. The payback period
varies from 3 to 5 years depending upon size of the system.
Systems Installed (all India)
Manufacturers
View
the list of manufacturers
Others
Solar Stills
Desalination is one of several methods used for converting saline
water to potable water. Under the desalination method, the
saline water is evaporated using solar thermal energy and resulting
steam is collected and condensed as a distilled water, Solar stills
are useful for desalination of water in small quantity. One sq.m.
of solar still can yield 1 to 2 litres of distilled water per day. Its
tentative cost is Rs.9,000/- per still of 1 sq. m. (made of Fibre
Reinforced Plastic (FRP)).
Akshay Urja Shops
(one per district)
-
Soft loan @ 7% to a maximum of 85% of the
cost of establishment of the shop subject to a maximum of Rs.10.00
lakhs through banks payable over a period of 5 years.
-
Monthly recurring grant of Rs. 5000/- per
month
-
Incentive of Rs.5000/- per month based on
minimum turnover of Rs.50000/- per month during 1st year and Rs.1.00
lakh per month during 2nd year
