FRONT CLASSROOM A FC D E B IG H REMEMBER, Homework due TODAY. NATS 101 : “The World We Create” 01/26

UNIT 1: Energy Sources, Conventional or Alternative?

Energy and Processes Two types of processes Exothermic processes Release Energy (heat, light) as the process takes place. More energy released in forming bonds than invested in breaking bonds. Endothermic processes Require Energy (heat, light ) for the process to take place. More energy invested in breaking bonds than released in forming bonds.

Apply what you learned Two new energizing drinks are offered to you for the same price. Both containers have 355 mL of the beverage: A) Contains C 6 H 10 O 8 B) Contains C 6 H 12 O 6 Energy Reactants Products You have 3-5 minutes Which one would you buy and why? What would be the products after you drink them? Draw an energy diagram for the chemical reaction in your body?

Exothermic C 6 H 12 O 6 (s) + 6 O 2 (g)  6 CO 2 (g) + 6 H 2 O(g) Glucose C 6 H 12 O 6 + O 2 PE CO 2 + H 2 O Reactants Products ENERGY RELEASED Breaking C-H, O=OForming C=O, O-H

Today’s Expected Outcomes:  Explain the concept of efficiency of an energy conversion device;  Calculate the efficiency of an energy conversion device;  Evaluate the best option for an energy conversion device based on availability, cost, efficiency, and environmental impact;

Energy generated in a combustion reaction can be used to do work (moving an object, like a piston in a car engine). Efficiency Not all of the energy produced by your car’s engine goes directly to turning the wheels.

WHERE DOES THE ENERGY GO? You Have 3-5 Minutes What percentage of the total energy generated do you think goes to moving the vehicle? Identify different parts where the energy generated by the combustion engine could go.

Energy Loss The energy from combustion in the engine is lost in different ways. Electric Cars ~ 90% 22 million miles driven 1 million gallons of gas $1.1 billion dollars $825 millions wasted!

Efficiency No machine is 100% efficient. EFFICIENCY is a measure of how much energy goes toward accomplishing the goal of the machine, versus how much energy is initially given. Efficiency = Energy that goes toward the goal Total energy put in X 100%

EFFICIENCY? 40-50% 3-6% Steam Power Plant Human Body 200/500 x 100= 40% Photosynthesis Electric Motor 95% 500 J of input: 200 J used 300 J heat

How Efficient? Arrange these devices in order of increasing efficiency. What are the implications of your results? Input: 150 J Output: Light 30 J Heat 120 J Fluorescent You Have 5 Minutes Input: 160 J Output: Light 8 J Heat 152 J Incandescent Input: 80 J Output: Light 46 J Heat 34 J LED

How Efficient? Efficiency = 8 J/160 J x 100 = 5% Efficiency = 30 J/150 J x 100 = 20% Efficiency = 46 J/80 J x 100 = 57.5%

Decisions, Decisions… Knowledge is useful if we can use it to make good decisions in our lives VS. What would you buy? Electric vs Gas Heater

Decisions, Decisions.. Discuss: What factors would you consider? What information would you need to make a good decision? Costs: Heaters: $ Gas: $19 per million BTU Electricity: $33 per million BTU 2-3 minutes 1. Availability 2. Cost 3. Efficiency 4. Environmental impact

Efficiencies How efficient is each heater? 90% 50% For every 100 J in, we get: I. 100 X 0.9 = 90 J II. 90 x 0.5 = 45 J The global efficiency is: 0.9 x 0.5 = %

Decisions, Decisions.. Study the two tables below: Electric Heating Gas Heating StepEfficiency (%) Coal Production96 Coal Transportation 97 Gen. Electricity33 Transmission Elec.85 StepEfficiency (%) Nat. Gas Production 96 Nat. Gas. Transp.97 How would you calculate the overall efficiency of an electric heater and a gas heater? What would be the value in each case? 0.96 x 0.97 x 0.33 x 0.85  26% 0.96 x 0.97  93%

Decisions, Decisions.. In terms of environmental impact, is there a difference? 2-3 minutes WHAT IS THE BEST DECISION? Based on availability cost efficiency environmental impact

US Electricity Generation