Warm Up #1 • What are some various forms of energy (what do we use to power stuff)? • Of the ones you listed in #1, which ones are better? Why are they better? • What is horsepower? Warm Up #2 • Where have you seen the word “watts” being used before? What do you think it means? • How can you tell a car, like a Acura NSX, is powerful? (i.e. what quality about the car makes it powerful?) • How many meters are in a kilometer? What about a megameter (yes, that’s a real thing)? Geosphere Energy: Renewable and NonRenewable Energy Math Part I Laws of Energy (Thermodynamics) • Law 1: Energy cannot be created or destroyed – You can’t make something out of nothing • Law 2: When energy is converted from one form to another, some of that energy is lost – Moving up food chain, some energy lost as HEAT Other Forms of Energy: Part 1 • Horsepower (HP) - measures the power generated by horses (original definition) – Ex. 1 horsepower = power of 1 horse Conversion: • 1 HP = 746 watts – Random, I know. Sorry about it. • Ferrari vs. Prius Other Forms of Energy: Part 2 • British Thermal Units (Btu) – Amount of energy needed to raise 1 lb. of water by 1oF – Think of it like a calorie (food) Random Conversions: • 1 watt = 3.4 Btu • 1 HP = 2,540 Btu Measuring Energy: Watts • Watt – standard unit of measurement for energy • Two forms you will see: • Kilowatts (1 kW = 1000 watts) – 1x103 watts • Megawatts (1 MW = 1,000,000 watts) – 1x106 watts Kilowatt Hours & Your Electric Bill • Your electric bill – measures amount of power used over a period of time • You will see: Kilowatt Hours (kWh) – amount of watts generated in 1 hour – Kilowatts x hours = kWh For these conversions: • Know what you are starting with • Know what they are asking for • Convert accordingly Warm Up #6 A resident of Beverly Hills, a community of 10,000 homes, uses on average about 5,000 kilowatt hours of electricity per year. The cost of electricity in this community is $0.20 per kWh. • How much electricity would a resident use in a 20 year period? • How many kWh of electricity does all of Beverly Hills use in one year? • What would their electric bill be as a community for twenty years? Warm Up #7 The Cobb family’s current electric hot-water heater requires 0.20kWh/gallon of energy, costing $0.10/kWh. Each person in the family of four showers once a day, 10 min. each. Each shower is approx. 5.0 gallons per min. Calculate: • Total amount of water the family uses per year taking showers. • The annual cost of electricity for family showers, assuming 2.5 gallons per min. of water is used from the water heater. • The family wants to replace their hot-water heater with a new, $1,000 more efficient model. It requires only 0.10 kWh/gallon of energy. How many days would it take to recover the initial costs? • Describe two practical measures the family could take to reduce overall water use. • Describe two practical measures that the Cobb family can lower their overall energy consumption (other than hot water). Practice Problem West Fremont is a community of 3,000 homes. A small coal-burning plant supplies the electricity of the town, with a capacity of 12 megawatts (MW). The average household consumes 8,000 kWh of electrical energy every year, at a cost of $0.10 per kWh. The town leaders suggest switching to wind power. They want to install 10 wind turbines, each with a 1.2 MW capacity, and each costing $3 million. Their lifespan is 25 years. Practice Problem Questions (a) Assuming the power plant is operating at full capacity for 8,000 hours/yr. How many kWh of electricity can be produced by the plant each year? (b) At the current rate of energy per household, how many kWh of electrical energy does the community consume in 1 year? (c) Compare your answers of (a) and (b) and explain why you would not expect their answers to match. (d) Assuming the energy needs do not change during the 25-year lifespan of the wind turbines, what would the cost of electricity be over 25 years (in $/kWh)? (e) Identify and explain TWO environmental benefits of switching to wind power, and TWO environmental costs for switching to wind power from coal. Warm Up # 3 A wind turbine in Palm Springs, a community with 800 turbines, uses on average about 10,000 kilowatt hours of electricity per year. The cost of electricity in this community is $0.20 per kWh. • Calculate the amount of energy generated from 1 turbine in 15 years. • Calculate the amount of energy generated by all of the wind turbines in 1 day • For this day, how much would it cost the people of Palm Springs Practice Problem For a certain dairy farm with 500 cows, the cost of installing a digester is approximately $400,000. Assume that the farm uses 800,000 kilowatt-hours (kWh) of electricity each year at a cost of $0.10 per kWh. The waste from a single cow can produce 3.0 kWh of electricity each day. (c) Assuming that the cost of electricity remains constant and the farmer starts using the manure from the cows in an anaerobic digester to produce electricity on the farm, calculate: • (i) The number of kWh of electricity that can be produced in one year • (ii) The amount of money the farmer can save in one year, NOT counting the installation cost of the digester. (You may round your answer to the nearest $1,000.) • (iii) The amount of time, in years, that it will take to recover the cost of installing an anaerobic digester on the farm. (You may round your answer to the nearest whole number of years.) (d) Calculate the minimum number of cows the farm would need to produce 800,000 kWh of electricity per year. Warm Up #4 You live in a community of 3,000 homes that rely on coal as a source of fuel. The average home uses 8,000 kwh of energy per year at the cost of $.10/kwh. Instead, town members want to switch to wind power; installing 10 wind turbines ($3 million each) which will last 25 years. • List two pros and two cons for switching to wind power. • How much energy does your entire community use per year? • If the energy needs stay the same over the 25 year lifetime of the wind turbines, what would be the cost for the community for wind power (in $/kwh)? How does it compare to the cost of coal?