Question : Studies show that the major energy consumption in Fijian villages is wood which is used for cooking over open fires. Typical consumption of wood is 1 kg person–1day–1. (a) Estimate the heat energy required to boil a 2-liter pot full of water. Assuming this to be the cooking requirement of each person, compare this with the heat content of the wood, and thus estimate the thermal efficiency of the open fire. (b) How much timber has to be felled each year to cook for a village of 200 people? Assuming systematic replanting, what area of crop must the village therefore set aside for fuel use if it is not to make a net deforestation? Hint: refer to Table 10.4. (c) Comment on the realism of the assumptions made, and revise your estimates accordingly. Answer: (a) mcDT ≈ 0.6 MJ (heat losses from pot imply actual requirement is higher). h ≈ 3%. (b) 70 tonnes; 7 ha.
Question : Studies show that the major energy consumption in Fijian villages
is wood which is used for cooking over open fires. Typical
consumption of wood is 1 kg person–1day–1.
(a) Estimate the heat energy required to boil a 2-liter pot full of
water. Assuming this to be the cooking requirement of each
person, compare this with the heat content of the wood, and
thus estimate the thermal efficiency of the open fire.
(b) How much timber has to be felled each year to cook for a
village of 200 people?
Assuming systematic replanting, what area of crop must the
village therefore set aside for fuel use if it is not to make a net
deforestation? Hint: refer to Table 10.4.
(c) Comment on the realism of the assumptions made, and revise
your estimates accordingly.
Answer: (a) mcDT ≈ 0.6 MJ (heat losses from pot imply actual requirement is higher). h ≈ 3%.
(b) 70 tonnes; 7 ha.
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