Exercises: Renewable and non-renewable energy sources

Classify these energy sources as renewable or non-renewable:

1. a) Solar energy.
2. b) Coal.
3. c) Wind energy.
4. d) Natural gas.

Why do we say that solar energy is renewable? Explain in your own words, thinking about whether the Sun gets "used up" when we use it.

Complete the sentence with the missing words: "Non-renewable sources are those that get $\dots$ when used, because nature takes $\dots$ of years to form them again. Two examples are $\dots$ and $\dots$."

Which energy source does each of these facilities use?

1. a) Giant wind turbines at the top of a hill.
2. b) Dark panels on the roof of a house.
3. c) A dam releasing water through its spillway gates.
4. d) A power plant burning natural gas to heat steam.

State whether each statement is true or false and correct the false ones:

1. a) "Oil is a renewable source."
2. b) "Firewood and pruning waste are biomass, a renewable source."
3. c) "If we install many wind turbines, the wind will run out."

In some towns there are hot thermal waters that spring from the ground, heated by the Earth's interior.

1. a) What is the name of the energy source that uses this heat?
2. b) Is it renewable or non-renewable? Justify your answer.

In a nuclear power plant, uranium is used as a "fuel".

1. a) Is nuclear energy renewable or non-renewable? Think about whether uranium gets depleted.
2. b) Name the most well-known problem with this energy source, related to what is left behind after using it.

At Leo's house, they cook with a butane gas cylinder and in winter they heat the house with a fireplace.

1. a) Which energy source does the stove use and which does the fireplace use?
2. b) Which of the two is renewable? Why?

The school has installed solar panels on the roof of the gym.

1. a) Give two advantages of producing its own electricity in this way.
2. b) Give one disadvantage of solar energy and explain how it can be solved or mitigated.

An entire neighborhood is heated using geothermal heat from the subsoil.

1. a) Why is it considered a renewable source?
2. b) What advantage does it have over heating by burning gas?
3. c) Could such an installation be placed anywhere? Explain your answer.

A biomass boiler burns $4\ \text{kg}$ of pellets a day, and each kilogram provides $5\ \text{kWh}$ of heat.

1. a) How many $\text{kWh}$ of heat does the boiler supply each day?
2. b) How many $\text{kWh}$ does it supply in a month of $30$ days?

Coal and natural gas are fossil fuels.

1. a) What common problem do they cause for the planet's climate? Name the gas they emit when burned.
2. b) If this problem is so serious, why do you think many countries continue to use them? Give at least one reason.

A hydroelectric dam produces electricity by releasing dammed water, as shown in the diagram in the figure.

1. a) Write down one advantage of this energy source.
2. b) Write down one disadvantage for the river environment and the valley.
3. c) Is it renewable? Justify your answer.

The label of an electric car says "zero emissions".

1. a) Explain why this only comes close to being true if the electricity used to charge it comes from renewable sources.
2. b) If the electricity is produced in a power plant that burns coal, where are the gases emitted then? Has the problem disappeared or has it merely shifted location?

On a dairy farm, slurry is used to produce biogas, which is then used for cooking.

1. a) Why is biogas considered a renewable source?
2. b) Besides providing energy, what other advantage does using slurry have?
3. c) Could this source supply a large city on its own? Explain your answer.

A city council must choose between installing a wind farm in the mountains or a small natural gas power plant next to the industrial park.

1. a) Write down two arguments in favor of the wind farm.
2. b) Write down two arguments in favor of the natural gas power plant.
3. c) Choose one of the two options and defend it with your own arguments, addressing one of its disadvantages.

A classmate claims: "Since the Sun and the wind are free and will not run out, saving energy will no longer be necessary once everything is renewable."

1. a) Explain why renewable energy is not truly "free": think about the infrastructure, materials, and land required.
2. b) Give one reason why saving energy will still be necessary even if all energy is renewable.
3. c) Rewrite your classmate's statement so that it is correct.

A town consumes $1000\ \text{kWh}$ of electricity per day and $40\ \%$ comes from renewable sources. The graph summarizes the town's energy consumption and its renewable share.

1. a) How many renewable $\text{kWh}$ does it consume per day?
2. b) The following year, the number of solar panels doubles and the renewable kilowatt-hours rise to $800$. If consumption remains at $1000\ \text{kWh}$, what percentage of renewable energy does the town reach?
3. c) Imagine that, with so much clean energy, people waste electricity and daily consumption increases to $1600\ \text{kWh}$ per day. What percentage is renewable then? What conclusion do you draw about installing renewables and saving energy?

There are strongly opposing opinions regarding nuclear energy.

1. a) Write down two arguments of those in favor: think about how much energy it provides, whether it emits carbon dioxide during operation, and whether it depends on the weather.
2. b) Write down two arguments of those against: think about waste and accidents.
3. c) Give your reasoned opinion: should a country invest in nuclear energy while installing more renewables?

Manufacturing a cell phone consumes a lot of energy: mining, manufacturing, and transport use as much energy as years of using the device.

1. a) Explain why changing cell phones every year uses a lot of energy, even if the new phone spends most of the day switched off.
2. b) Propose two responsible consumption decisions that reduce this energy expenditure.
3. c) Link this saving to the use of non-renewable sources.

Someone claims: "It is very sunny in Spain, so all electricity should be solar by now."

1. a) Give two reasons why this is not as easy as it seems.
2. b) Propose a combination of renewable sources that can also provide electricity at night, and justify your answer.
3. c) Explain what role batteries or pumped-storage hydroelectric dams can play in that system.

A city bus with $40$ passengers consumes the same energy on a trip as $10$ cars traveling the same route with only one person in each, as shown in the figure.

1. a) How many times less energy per person does the bus consume compared to the car?
2. b) Explain why using public transportation helps to use fewer non-renewable sources.
3. c) Propose two other ways to reduce the energy spent on transportation.

Unit challenge. Energy audit of a cup of herbal tea.

1. Phase 1: Home measurement. Heat $200\text{ ml}$ of water in a saucepan or microwave. Using a kitchen thermometer (uncertainty of $\pm 0.5\text{ }^\circ\text{C}$), measure the temperature every $30\text{ s}$ for $2\text{ min}$. Create a data table ($t$, $T$) and plot the graph of $T$ versus $t$. Explain what energy transformations took place and where useful energy losses occurred.

2. Phase 2: Source tracing. Access the website of the U.S. Energy Information Administration (EIA) ("Hourly Electric Grid Monitor" section) at the time you carried out the experiment. Record the percentage of electricity generation coming from renewable sources (wind, solar, hydroelectric) and non-renewable sources (natural gas, coal, nuclear).

3. Phase 3: Short report. Write a one-page proposal relating the energy used in your kitchen to the environmental impact of the consulted electricity mix, proposing two feasible energy-saving measures for your home.

Evaluation criteria:

• Rigor in data collection, uncertainty calculation, and graphical representation ($T$ vs. $t$).

• Correct identification of energy forms, transformations, and degradation.

• Critical analysis of actual EIA data (renewables vs. non-renewables) and feasibility of the proposals.