If you are trying to work out a vision for the energy future
of the United States, it helps to understand the current situation.
What are the major sources of energy? Where does this energy get used?
The best "big picture" drawing I've seen is found on the Lawrence
Livermore web site. This shows how much energy went where in
the United States during the year 2002. Click Here
What is the current
For those who find the drawing confusing, I've
extracted the main points into a couple of tables. (The energy
content of the content of various sources is expressed in "quads"
which is short for "quadrillion BTU". This is a pretty big number
and represents the energy in roughly 8 billion gallons of gasoline.)
energy sources for the US (2002):
||15% imported |
Electricity is a "secondary energy
source". Some other energy source must be burned/consumed to generate
it. However it is important enough to the economy and the average
household that I thought I'd break out the percentages on how its
generated and used.
Major categories of energy use for the
||Only 11.9 useful |
||only 5.3 useful |
|Non Fuel (Feedstock)
||plastics, fertilizer, etc |
Fuels for electricity generation (Percentages):
and lost energy
energy flow diagram also breaks out how much energy is being wasted.
Most energy sources (hydrocarbon fuels, nuclear power) generate heat.
Applications that can use the heat directly (heating your home, running
a blast furnace) tend to be fairly efficient. Most of the energy does
Applications which need to convert heat into
motion (planes, trains and automobiles, as well as most electrical
generators) are not so efficient. Only about 31% of the energy devoted
to electricity generation actually winds up as electricity. Most of
the rest winds up as waste heat. The transportation sector is even
worse: only about 20% of the energy goes to useful work.
This inefficency represents a huge opportunity. All together
the drawing shows 35.2 quads of energy performing useful work and
56.2 quads labelled as "lost energy". A number of pundits have
been saying for years (even decades) that practical improvements in
efficiency represent the biggest "bang for the buck" when trying to
build a "friendlier" energy future.
A big chunk of the energy we import
(meaning petrolem) goes to fuel our cars. Cars require a compact,
portable energy source and a liquid hydrocarbon such as gasoline
fits the bill better than, say, coal or wood. A widely quoted statistic
is that the typical car only converts about 10% of the available energy
in the gasoline to forward motion. A range of factors contribute to
the relative inefficency of car engines:
- the relatively small size
of car engines (at least compared to a ship or power plant) means
heat looses are greater
- the engine must run over a wide range of speed
and power that are not its most efficient setting. 90% of
the time a car engine is running at around 10% of rated capacity.
A car with a 200 HP engine may only use 15 HP cruising at 60
MPH on a level surface. The rest is only needed when accelerating
or climbing a hill.
- the engine consumes fuel at idle when it
is doing no useful work
While the ultimate solution might involve cars
powered by super batteries or fuel cells, there is a huge opportunity
if we can tweak the good old internal combustion engine and utilize
a few percent of the energy that is currently wasted. Ideas along
these lines include:
- use stronger materials to produce lighter weight
- use a new generation of clean diesel engines. Diesel engines operate
30% more efficiently than gasoline engines due to the higher compression
ratio and combustion temperatures.
- hybrid cars that use an both an
electric motor and an internal combustion engine. The electric motor
allows the IC engine to be off when the car is stopped, can recapture
braking energy and can provide some of the power when the IC
engine would be inefficient.
A diesel-electric hybrid that uses bio-diesel
(assuming the bio-diesel is produced in an energy efficient
manner) might be an interesting development. I am all in favor of
the rooftop solar-hydrogen generator that supplies your fuel cell
powered car, but in the meantime there seems to be a lot to be gained
with careful development of existing technologies.
is now (at least in the short term)
In the short to medium term, the energy infrastructure
of the US will look much as it does now. Major changes to something
this massive will take time. For example, the installed generating
capacity of the US was over 800 Gigawatts in 2001. In the same year
the worldwide production in photo-voltaic panels was about 400 Megawatts.
Even assuming an optimistic growth rate in solar cell production,
it will take decades to seriously change the mix.
to the scale of the existing infrastructure, improvements to existing
technologies may have more impact than the sexy new technologies,
at least in the short term. With over 400 GW of coal fired generating
capacity, reducing coal pollution by 1% (either through efficiency
improvements or by better pollution control) has a similar benefit
to a number of years of solar cell production.
Improving what we've got:
Improving what we've got: Cars
A big chunk of our energy is
used by buildings. The homes where we live and the factories and offices
where we work offer many possibilities for reducing energy
without sacrificing functionality. Better insulation, paying attention
to siting, orienting windows for optimum solar gain, air to air heat
exchangers to recover heat lost to ventilation are all things which
are easy to do if considered early enough in the design of a
building and often payback several times over in long term energy
As another example, lighting consumes perhaps 25% of the
electricity we generate (I've seen a pretty wide range of statistics
on this one). A typical household incandescent bulb is 2% efficient. A
good flourescent lamp is 8-10% efficient and uses about a quarter
of the electricity for the same amount of light and the new ones
are much better in terms of color balance and flicker. The new intense
white LEDs are several times as efficient as flourescents and are
predicted to eventually become the lamp of choice when the price falls
far enough. 25% of our electrical generating capacity is the equivalent
of more than 200 one GW power plants. Cutting this in half is a really
big win. Link