How much energy we can save ? Energy needed to treat water Average energy use for water treatment drawn from southern California studies is 652 kWh per acre-foot (AF), where one AF = 325,853 gallons. Thermal Energy in Coal The thermal power plants consume about 0.45 kg of coal per kWh. Energy output/fire power plant A typical 500 megawatt coal power plant produces 3.5 billion kWh per year. CO₂ Emission Taking coal to contain 50 percent carbon, which combines with oxygen during burning to form CO₂, we can arrive at 1.83 kg CO₂ for every 1 kg of coal burned.
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To calculate the savings, we need to first determine reduction in waste- water generation for given 7 million population of Hongkong, only 1 million people in HK using low flush toilet and low shower head/ 1 million leaky toilet and faucet. Assume all use shower.
Conventional Water fixtures
|
End-Use |
Conventional fixtures |
Usage pattern |
Population |
Daily Usage |
|
Toilets |
3.5 gal/flush |
4 flushes/per/day |
6 million |
3.5*4*6 = 84 million gallons |
|
Showers |
5 gal/min |
5 min/shower |
6 million |
5*5*6 = 150 million gallons |
|
Faucets |
4 gal/min |
2.5 min/per/day |
6 million |
4*2.5*6 = 60 million gallons |
|
Leaks |
10% of total use |
- |
- |
0.1*(84+150+60) = 29.4 million gallons |
|
Total |
|
|
|
323.4 million gallons |
Water efficient fixtures
|
End-Use |
Water efficient fixtures |
Usage pattern |
Population |
Daily Usage |
|
Toilets |
1.6 gal/flush |
4 flushes/per/day |
1 million |
1.6*4*1 = 6.4 million gallons |
|
Showers |
2.5 gal/min |
5 min/shower |
1 million |
2.5*5*1 = 12.5 million gallons |
|
Faucets |
2 gal/min |
2.5 min/per/day |
1 million |
2*2.5*1 = 5 million gallons |
|
Leaks |
2 % of total use |
- |
- |
0.02*(6.4+12.5+5) = 0.478 million gallons |
|
Total |
|
|
|
24.378 million gallons |
Per day reduction in waste-water generation = 323.4 - 24.378
Per day reduction in waste-water generation = 299.022 million gallons
Total water saving per year in galloon 109143.03 million gallons. (299.022 *365)
- How much energy we can save?
Calculation of Energy saving
Given that Average energy use for waste-water treatment = 652 KWh per AF for 325,853 gallons
Average energy use for 1-gallon waste-water treatment = 0.002 KWh (652/325,853)
Per day Average energy use for 299.022 million gallons waste-water treatment = 299022000*0.002
Pre day energy saving =598044 KWh
- How much coal (kg) we can save?
Given that thermal power plant consumes about 0.45 kg of coal per KWh
From above step - Per day energy saving = 598044 KWh
Per day coal saving = 0.45*598044
Per day coal saving = 269119.8 kg
- How much CO2 we can reduce?
Given that 1.83 kg of CO2 is released for every 1 kg of coal burning
From above step -Per day coal saving = 269119.8 kg
Per day reduction in CO2 = 1.83 * 269119.8
Per day reduction in CO2 = 492489.234 kg
- How many African children (1 Litres/kid/day) we can support?
Per day reduction in waste-water generation = 299.022 million gallons
Noted that 1 gallons = 3.785 Litres
299.022 million gallons = 299.022*3.785 million Litres
Per day reduction in waste-water generation = 1131.8 million Litres
Given rate of consumption of African children = 1 Litres/kid/day
Number of African children that can support = 1131.8 million Litres /day 1 Litres/kid/day
Number of African children that can support = 1131.8 million
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