Human Energy Needs

Energy needs (kcal/person/day) have mirrored societal evolution

• Primitive – 2000• Hunter-gatherer –

5000• Early agriculture –

12,000• Later agriculture –

20,000

• Early industrial – 60,000

• Modern industrial – 125,000

• Current U.S. – 250,000

1850s Fuel Usage

Wood Coal OilNat. Gas. Other

• Primarily Wood Used

1900s Fuel Usage

WoodCoalOilNat.GasOther

• Wood and Coal Use about equal

• Easy transition to make because both are solid fuel

• Oil = liquid need to change furnace technology

1950s Fuel Usage

WoodCoalOilnat. gasother

• Big switch to fossil fuels is complete

• More use of liquid and gaseous fuels

• Very little use of renewable fuels or nuclear

1990s Fuel Usage

WoodCoalOilNat. Gas.Other

• Oil is now the dominant fuel type followed by natural gas and coal.

• More use of alternative fuels and nuclear

• Wood primarily used in third world nations

Amount of Fossil Fuels being Used

• The U.S. tops the charts in terms of total usage and in terms of per capita use

• And this amount is astronomical……..

U.S. Energy Use

• In 1991, the U.S. consumed 81.5 quads

• Estimated use for 2000 was 96.2 – 100 quads

• How much is a quad?– 1 quad = 1,000,000,000,000,000 BTUs– 1 BTU = energy required to warm 1 lb water 1

oF

How much is a Quad?

472,000 Barrels of Oil/Day for 365 Days or 172,280,000 Barrels of Oil

75 Supertankers500,000 Railroad Cars of Coal

Annual Production of 20 Three Mile Island Nuclear Plants

What is this energy being used for?

liquidfuelelectric

heat <100heat 100-600heat >600

• Liquid Fuel is for vehicle use

• Heating less than 100 oC is space-heating

• Other heating is for industrial purposes

• Electricity generation is only 8%

35%

34%

Need to match energy quality with quality of task

• Amory Lovins – physicist, states that high quality energy is currently being wasted doing low quality tasks.

• What do we mean by high quality and low quality?

So, when was the last time you used your natural gas powered

stereo?

High Quality Energy

• High quality energy is energy like electricity. Electrons running through wires at the speed of light constitute very high quality energy.

Low Quality Energy• Energy with lots of waste heat is low

quality energy.

• Energy that is widely dispersed and not “focused” is also low quality

• Examples include burning fossil fuels (lots of waste heat) and solar (widely dispersed)

Task “Quality”

• High quality tasks are those that require high quality energy – electricity is needed to run “electronics”

• Low quality task can be accomplished with less focused energy – space heating. Remember how much energy is devoted to the task of space heating (35%!)

So, what should we do?

• Conversion of space heating tasks to solar energy is a good match of energy and task quality.

• On average sun puts 1 cal/cm2/minute on all earth surfaces. This is plenty to heat spaces under that cm2.

Energy Conservation

• We’ll discuss this as we go through all the energy “types” but let’s list some ways here……..

Design appliances and machines with energy conservation in mind

compressor

compressor

Refrigerators: Yesterday & TodayWhich was really more efficient?

Resource Conservation = Energy Conservation

• Energy needed to extract resource

• Energy needed to change resource into usable product, e.g. water

• Energy needed to dispose of waste resource following use, e.g solid waste