Homework 7, due Wed Nov 18, 2009
			ENVR 30: Fall 2009 

1. Search for news reports or online for several examples of new ideas for
alternative energy.  Write up a paragraph describing the idea or ideas.
Then think carefully about the idea or ideas and analyze it as well as you
can.  Come to some conclusion about the idea.  For example you might conclude
that it is a great idea that should be tried on a large scale, that it is
a possible idea that should be tried on a small scale, that it is an idea
that is unlikely to make much difference, or that it is a stupid idea
that should be dumped immediately.  You might also conclude that
from the information you found you cannot decide.  Be especially careful and
critical of any claims made by groups or individuals that stand to gain 
financially if the idea is adopted or developed.
[Hint, here are some examples:  using generators attached to bike pedals,
Burning trash to make electricity, putting solar panels on cars, 
making jet fuel out of
biofuel, dirt powered bacteria batteries, waste water into ethanol, etc., etc.,
etc.]

2. Suppose there is windmill farm where all the windmills have 6 foot long blades.
Which configuration would give more electricity?
a. One windmill with wind blowing 25 mph
b. Two windmills with wind blowing 20 mph
c. 10 windmills with wind blowing 10 mph
d. 50 windmills with wind blowing 5 mph?
e. All of the above give approximately the same energy.

3. Name some of the advantages and disadvantages of wind power

4. Describe the advantages and disadvantages of corn ethanol.  
Is there a difference for sugar cane ethanol?

5. Which converts more of the sun's energy to useful energy:  Photosynthesis,
silicon photovoltaics, or flat plate solar heating panels.  Why don't we only use
the most efficient of these?

6. When fossil fuel or biofuel is burned to make energy it is called a heat
engine.  Which of the following are true about the fraction of the 
chemical energy in the fuel that can be converted to electricity or 
mechanical energy?
a. Carnot limits the efficiency;  it cannot be 100% converted
b. The efficiency is higher if the fuel is burned at a higher temperature
c. the efficiency is lower if the engine exhaust is at a higher temperature
d. The formula for the maximum efficiency is eff = (T_hot - T_cool)/T_hot,
where T_hot is the temperature of the burning and T_cool is the tempertaure of the
exhaust
e. Typical efficiencies for cars burning gas are around 15% because of Carnot
f. 100% efficiency is possible if the engine exhaust came out at absolute 0 
degrees Kelvin.
g. Electrical power plants have higher efficiencies than cars because they
burn the fuel at higher temperature.
h. Hydroelectric plants cannot be 100% efficient due to Carnot

7. Nuclear power is also a form of solar energy
a. True
b. False