Biomorph
Challenge #3 |
Water, Air, and Energy
Type, print out, and turn in BEFORE class.
10 points off for late work.
10 points off for lack of staple.
| 1. The Biomorphs keep trying to pull the wool over our eyes: "Our advanced Biomorph technology will require only 1.5 x 1014 kilowatts of power. We'll obtain this on Earth with solar energy." How do you respond to this challenge? Use a calculation to counter the Biomorph claim. (Hint: Facts below may be useful.) The
surface area of the Earth is 5.1 x 108 km2
= 5.1 x 1014 m2 So,
the Biomorphs would need to surround the entire planet Earth with
solar cells in order to obtain all its solar energy for their needs. |
Facts about Water and EnergyWater accounts for 60% of our total weight Water consumption Water use Useful conversions: 1 kg = 2.2 pounds |
| 2.
Use your graph of water saturation and temperature to solve these problems.
Suppose that a front of air containing 0.7% water vapor blows over Gambier. (a) What happens if the air cools to 10°F? What is now the relative humidity?
When the air cools to 10°F, 0.7% water vapor will be above saturation level (0.3%). So vapor will condense as fog, and probably fall as snow (given that 10°F is below freezing.)
(b) Inside your dorm, the air is heated to 65°F. What is now the relative humidity? What effect does it have on the human body?
At 65 °F, the relative humidity is given by the actual water fraction (0.3%) divided by the saturation level (1.5%), equaling 20%. At 20% relative humidity, the air feels dry, as dry as the Sahara desert. Skin may crack, and throat may feel irritated, more susceptible to infection.
3.
A camel can
lose 30% of its weight in water after 17 days in the desert without
drinking; then, when it finds water, it can drink enough in ten minutes
to replace it all. Suppose after 17 days in the desert a fully dehydrated
camel weighing 500 kg finds water; how much would it have to drink?
If the camel drinks water equal in mass to 30% of its original body weight:
0.7 W = 150 kg W
= 214 kg
4. A stillsuit is used on Dune to conserve water.
(a) Explain the function and the problems to be overcome in designing a stillsuit.
The stillsuit distills water evaporating from perspiration, and it filters water from urine and excrement. The energy for distillation and filtering comes from body movements in which "extra" energy is released, such as breathing and walking.
The key problem is how to obtain enough energy to cool the body and recycle the water, without adding energy load to the person walking. Our understanding of body motion shows that the energy available is 10-100 fold too small to cover the energy needed for evaporative cooling. Nevertheless, we can devise stillsuit-like power cells that provide modest amounts of power for devices such as a cell phone or a light.
Another problem is cleanliness; the filtrate from human wastes has to be carried all day.
(b) How much water is lost through human wastes? In a stillsuit, what happens to these wastes? What is the consequence for Fremen society; what's it like to be in a cave with a lot of Fremen?
Human water loss through breathing, perspiration, urine, and excrement totals: (0.5 + 0.9 + 1.5 + 0.1) liters = 3 liters per day (approximately). The filtrate (materials filtered out) plus excrement are stored in pouches on the thighs. These materials contain concentrated odorous substances, which need to be removed and recycled in "reclamation chambers." In Dune, the author often comments on the strong odor experienced around Fremen in their living quarters.
5. Suppose solar energy is used on this planet. Assume the facts listed above.
(a) Today, the best photovoltaic solar panels are able to convert 20% of the available energy to electricity. If a glowglobe uses as much electricity as a 25 W light bulb, how large an area of solar panels would be needed to light one glowglobe for each of the 1000 persons living in the sietch?
The
solar power available from a panel of one square meter: The area of solar panels needed: 25,000 Watts / 60 Watts/m2 = 417 square meters
(b) Suppose a "plantoid" alien being uses photosynthesis (with 20% solar efficiency) instead of eating food. Assume a human being eats food containing 2000 food Calories per day (1 food Calorie = 4.18 kilo-Joules). What surface area (in square meters, m2) would the plantoid need to sustain itself?
The daily energy obtained by the plantoid per square meter is: 60 Watts/m2 x 3600 seconds/hour x 24 hours/day = 5.184 x 106 Joules = 5.184 x 103 kilo-Joules/day The plantoid would need leaf-like appendages totaling an area of: 2000 Cal x 4.18 kilo-Joules/Cal / 5.184 x 103 kilo-Joules/day = 1.61 square meters
6. In human technology, the overall per capita power consumption (and the waste products of fuel) are increasing.
(a) Today in the United States, the per capita power consumption is 10,500 Watts. In Bangladesh, it is 265 Watts. For the Bangladeshi per capita power to grow exponentially to reach that of the United states by 2100 (assuming that of the U.S. remains constant) what doubling time would be needed?
The
time from year 2008 to year 2100 = 92 years. d = 92 x log(2) / log(10,500/265) = 17.3 years, doubling time for per capita power consumption
(b) In the year 1960, the CO2 level in Earth's atmosphere was 317 parts per million (ppm). In 2000, the CO2 level was 370 ppm. If CO2 increases exponentially, what is the doubling time?
The time from year 1960 to year 2000 = 40 years. The CO2 level in the year 2000: 370ppm = 317ppm x 2(40 years / d) d = 40 x log(2) / log(370/317) = 179 years
7. Compare and contrast the ecosystems of Gambier and of Dune.
(a) How do materials and energy cycle in each ecosystem?
In Gambier, the primary producers are plants such as grass and trees, and soil bacteria. These use solar energy to fix CO2 into biomass, a process that requires splitting the water molecule H2O to release oxygen gas (O2). The producers lose 90% of the energy as heat. Their biomass is consumed by consumers such as groundhogs, but 90% is converted back to CO2 and energy is lost as heat. Secondary consumers such as foxes consume the groundhogs. Decomposers such as bacteria and fungi (microbes) consume all dead body parts eventually. Carbon dioxide can be fixed again by plants and bacteria through photosynthesis.
On Dune, there are few photosynthetic plants and bacteria, because photosynthesis requires water. The young sandworms, "little makers," are called "half-plant-half-animal." They produce spice, possibly through bacterial metabolism of organic matter producing acids and CO2. The mature sandworms consume the little makers; their metabolism releases oxygen gas. Both little makers and mature sandworms produce "spice." The spice is consumed by plankton, which is consumed chain including animals such as mice and eagles. All levels of the system lose heat.
(b) What is lacking or incomplete about the Dune ecosystem?
The ultimate source of energy on Dune is unclear. Materials such as carbon and oxygen can be recycled indefinitely (so long as gases are not lost from the atmosphere) but energy must be lost as heat and replenished from outside the system. Without photosynthesis, it is unclear where the energy comes from. Also, metabolism producing oxygen gas is extremely energy-expensive; there is no known metabolism with a digestive tract that could produce oxygen gas.
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