1. Milk production at a diary farm was low so the farmer wrote to the local university asking for help from academia. A multidisciplinary team of professors was assembled and two weeks of intensive on-site investigation took place. The scholars then returned to the university, notebooks crammed with data, where the task of writing the report began. Shortly thereafter the farmer received the write-up, and opened it to read on the first line: “Consider a spherical cow …”

2. What is ‘the ability to do work’? To DO anything, energy is required. BUT, the point to grasp is Energy isn’t so easy to define. Other definitions: - Measure of ability - Capacity to produce heat - E=mc 2 Energy

3. Definitions  Work  Force acting over a distance.  A measure of accomplishment.  Doing.  Power  Rate of energy use – energy/time  units: Watts (W), horsepower (hp)  Efficiency  (what you get out)/(what you put in)  Potential energy – stored energy.  Kinetic energy – energy associated with motion.  There are an incredible number of overlapping classifications of energy. Units of energy: Joule (J), btu, Calorie

4. More definitions  Thermal energy - kinetic energy of molecules  We think of this as heat.  Radiation (electromagnetic energy)  This includes X-Rays, light, radio waves, cell phone communications, microwaves, and more  This stuff is very cool.  Electrical energy – kinetic energy of charges  Mechanical energy – energy associated with moving parts  Chemical potential energy – energy stored in molecular bonds  Nuclear energy – energy stored in the nucleus of atoms

5. Energy ‘Laws’  Conservation  Energy can be created or destroyed, it can change forms but it always exists.  1 st Law of Thermodynamics E earth E in E out E in + E earth – E out = constant ThermalMechanical+ Thermal Mechanical Thermal  Conversion of thermal energy to mechanical energy  Can’t be 100% efficient  2 nd Law of Thermodynamics

6. Mechanical vs. Muscular Energy  The incredible increase in economic and technological advances of the ‘modern’ world were brought about by humankind’s switch from muscular to mechanical energy.  How do they compare?  Let’s look at an example that may give us all a better grasp of energy.  Example – my daily commute  Niwot to CU

7. Muscular Energy (in honor of bike week)  If I bike, I am using muscular energy.  How much?  260 kJ  Where does the muscular energy come from?  Food (potential energy of food molecules)  Our bodies convert food energy to muscular energy with ~20% efficiency.  SO, I need to input 1300kJ to get to work on muscular energy.

8. Mechanical Energy  If I drive to work, I am using mechanical energy.  How much?  Let’s skip this step and directly calculate the amount of energy in the amount of gasoline that I consume.  I use ~1 L to get to work.  So, I use 48,000 kJ of energy to drive to work.  I use 37x more energy driving than biking.  BUT, when driving, I get there faster (3x) and I can carry more stuff.

9. Another example: How does my toaster do work?  Coal is mined in Wyoming and shipped via rail to Cherokee Station in Denver.  The chemical potential energy in coal is converted to thermal energy and other less energetic molecules. (We call this process combustion.)  The thermal energy is converted to mechanical energy in a steam turbine.  The mechanical energy is converted into electrical energy in a generator.  The electrical energy, which is easy to move, is sent to my house on wires.  The electrical energy reaches my toaster through it’s cord and is converted into thermal energy via a big resistor.  The thermal energy warms my toast.

10. Last points  Net energy use:  I have also heard this concept called ‘lifecycle energy’.  There is ‘other’ energy involved with me driving or biking to work.  Energy required to build my bike.  Energy required to build the paths that I bike on.  Energy required grow and process the food that I need as fuel.  Energy required to process and get water to me so I can ride my bike.  All the energy required needs to be included when developing comparisons.  In any energy conversion process, what happens to the energy that is converted to the useful form?  Combustion  What happens to molecules with lower internal energy?  What happens to the thermal energy not converted to mechanical energy?  Metabolism of food