Existing Energy Sources

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.

 

 

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.)

Major energy sources for the US (2002):

 

 

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 US (2002):

 

 

Fuels for electricity generation (Percentages):

 

 

Electricity Consumption(Percentages):

 

 

The 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 something useful.

 

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:

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:

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.

 

 

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.

 

Simply due 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.

 

 

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 saving.

 

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