UNESCO resource kit - science and technology educa...

UNESCO Module 19: Combined heat and power - Teacher's Notes ------------
Notes on the activities, answers to questions
Page 2
Page 2, 3: These pages introduce the idea of a district heating system supplied
by a combined heat and power (CHP) plant.
Some points for consideration in the discussion (Activity 1):
• In some countries, few homes have central heating systems with radiators,
which would be required for connecting to a district heating scheme.
• If a CHP plant breaks down, many people will get cold. This can be avoided
by having several plants supplying a single district.
• In many countries, the climate is such that people do not require much
home heating for appreciable parts of the year. This means that CHP is
relatively inappropriate.
Page 3: Activity 2 encourages students to think about the energy and material
inputs and outputs fora CHP plant. This should emphasise to them the rules of
conservation of matter and energy.
Activity 3 requires them to find out about electrostatic dust precipitators, and to
list environmental protection measures associated with a CHP plant.
page 4: Activity 4 requires students to calculate energy efficiencies. Answers:
90%; 35%; 40%.
Activity 5 requires some brainstorming. In practice, little use is made of waste
hot water from thermal power stations.
Page 5: The design task (Activity 6) will emphasise to students the great
volume of hot water which must be stored for a CHP system, in order to match
supply to demand. This could be extended to a practical task, in which students
model such a system on a reduced scale using, say, 2 litres of water instead of
20000 m".
Activity 7 emphasises the importance of multiple supply systems.