Exercises: Energy systems and markets

Classify these energy sources as renewable or non-renewable, briefly justifying each case: (a) solar, (b) coal, (c) wind, (d) natural gas, (e) hydroelectric, and (f) nuclear.

List the common energy supplies that reach a home (electricity, natural gas, etc.) and explain which meter measures the consumption of each and in which unit it is billed.

Explain with a household example the difference between power (measured in $\text{kW}$) and energy (measured in $\text{kW} \times \text{h}$): use the example of a $2000\ \text{W}$ oven turned on for half an hour to illustrate both quantities.

Explain the difference between primary energy (the source as obtained: sun, gas, uranium) and final energy (the energy you use: electricity at the outlet, gasoline at the pump), with an example of converting one into the other.

The smart electricity meter measures and communicates consumption. Explain what it measures exactly, how often it sends data to the utility company, and one advantage it has over the traditional meter.

Service capacity (the amperage rating of your home's electrical service) is the maximum power you can use at the same time at home. Explain what happens if you plug in appliances that exceed it (the circuit breaker trips and power is cut) and how the situation is resolved.

Name three renewable energy sources and write which natural phenomenon each one uses (solar radiation, wind, dammed or flowing water).

The electric bill charges for $\text{kW} \times \text{h}$. Explain what $1\ \text{kW} \times \text{h}$ represents using an example (a $1000\ \text{W}$ appliance running for one hour) and why it is a unit of energy and not of power.

The figure shows the chain that carries electricity from where it is generated to a house, but one of the stages is covered with a question mark, as shown in the figure.

Indicate which stage is missing from the chain, explain what happens during it, and explain why that stage is carried out at very high voltages instead of directly at $220\ \text{V}$.

An electricity bill usually includes a fixed charge (for the agreed power capacity, even if not used) and an energy usage charge (for the $\text{kW} \times \text{h}$ consumed). Explain what each term pays for and analyze what would happen to the bill of a home that contracts a high power capacity but uses very little energy.

A country's 'energy mix' is the breakdown of sources used to generate its electricity. Analyze why this distribution matters so much in three areas: dependence on other countries, price stability, and greenhouse gas emissions, giving an example of a source in each argument.

A house has a contracted power capacity of $4.4\ \text{kW}$. Calculate whether the oven ($2\ \text{kW}$), washing machine ($2\ \text{kW}$), and electric cooktop ($1\ \text{kW}$) can operate at the same time by adding their power ratings, and explain two practical choices that would prevent exceeding the limit without changing rate plan.

Time-of-use rates divide the day into periods with different prices. Explain how this works, which household appliances should be scheduled during off-peak hours (electric water heater, washing machine, dishwasher), and why these appliances can wait while others cannot.

Between the power plant and your home there are several transformers. Explain what a transformer does, why voltage is stepped up for transmission and stepped down for consumption (in relation to line losses), and where you have seen transformers in your town or city (substations, pad-mounted transformers, utility poles).

Solar energy is cheap but intermittent; natural gas is expensive but available on demand. Explain what renewable intermittency is and three ways to manage it in the electrical system (pumped-storage reservoirs, batteries, interstate transmission lines).

A bill has a fixed monthly charge of $\$10$ and a usage of $250\ \text{kW} \times \text{h}$ at $0{,}\$18$ per $\text{kW} \times \text{h}$. (a) Calculate the total amount excluding tax. (b) Calculate what percentage of the total corresponds to usage and what percentage to the fixed charge. (c) Reason who is affected more by a high fixed charge: someone who uses a lot or someone who uses very little.