Fuel Efficeint Stoves

  The most commonly used stoves in most  households for cooking 
  are either mud stoves or three stone stoves, also referred as 
  traditional  cookstoves (TCs). The efficiency of these stoves 
  are less than  10%. Applying the principles of combustion and 
  heat transfer,  wood and other biomass burning fuel efficient 
  stoves have been  designed by  ASTRA (ASTRA, Indian Institute 
  of  Science ),  also  called  as  Astra  stoves  or  Improved 
  cookstoves (ICs). In Astra stoves complete combustion of fuel 
  wood  takes place with as little excess air as practicable to 
  generate  the  highest  temperature  of  flue  gases. In  ICs, 
  combustion  of  fuel  wood  is carried out over a grate in an 
  enclosed  fuel  box  with ports of suitable size for entry of 
  air. The  grate  helps in  entry of air below the fuel bed to 
  burn the char as well as for separation of ash from fuel. Air 
  required  for  burning  the  volatile  matter  released  as a 
  consequence  of  heating the fuel (also referred as secondary 
  air), enters  through  a  port  at a level slightly above the 
  grate. Heat  gets transferred to the pans by the mechanism of 
  conduction, convection and radiation. Fuel efficiency studies  
  have  shown  that  the  fuel  need  for  cooking   is   about 
  1.92(avg)±1.02(Sd) kgs/person/day  in TCs, while in ICs it is 
  about 1.1(avg)±0.78(Sd) kgs/person/day. This means that there 
  is a  saving  of  about  42% of fuel by switching over to ICs 
  from TCs. The  average fuel  consumption for water heating in 
  traditional stoves(efficiency 10-16%) is about 1.68(avg)±0.80 
  (Sd) kgs/person/day, while  in  improved  stoves  (efficiency 
  35-60%), it is  about 1.36(avg)±0.63(Sd) kgs/person/day. This 
  result based on sample  households shows a potential of 19 to 
  24%  saving  in  improved  design. Traditional stoves in most 
  villages are without chimney. With the chimney,the efficiency 
  of the stove  increases and is about 22%.  In improved stoves 
  the  fuel  is  allowed  to  burn  over a cast iron grate. Air 
  required  for  burning  is  allowed through the grate so that 
  combustion  is  controlled. Rate of burning (to a temperature 
  of 45-50°C) in  improved  stoves  is about  30 minutes for 50 
  litres.