Chapter 1: How Electricity Transfers Through Systems

How can we design more reliable systems to meet our communities’ energy needs?

Learning Objectives

Describe the human impact of large-scale power grid failures.
Define and differentiate voltage, current, and resistance in an electrical circuit.
Apply Ohm's Law (V=IR) and the power equation (P=IV) to solve for unknown values in a simple circuit.
Model the electrical grid as a system composed of generation, transmission, and distribution components.

Prerequisites:

We begin with a crisis—a story that starts with a flicker, a hum, and then a sudden, profound silence. In February 2021, a massive winter storm plunged millions of people in Texas into darkness and cold for days. This was not just an inconvenience; it was a catastrophic failure of a system we depend on for nearly every aspect of modern life. To understand how a grid designed for reliability could fail so completely, and more importantly, how we can build better, more just systems for the future, we must travel from the human scale of a cold home, to the vast scale of a regional power grid, and down to the invisible world of the electrons that power it all.

1.1 Phenomenon: A System in Crisis

Our anchoring phenomenon is the widespread power outage in Texas during the February 2021 cold snap. Extreme weather caused demand for electricity to surge while simultaneously freezing the equipment needed for power generation and fuel delivery. To prevent a total collapse of the entire grid, operators were forced to begin controlled blackouts, intentionally cutting power to millions of customers. This event provides a powerful, real-world puzzle at the intersection of extreme weather, engineering design, and public policy. Our first step is to understand the human impact of this system failure.

Think of a time you experienced a power outage. What were the immediate consequences?
Why is a massive, multi-day blackout more serious than a brief local outage? Which other critical systems are affected?

Hexagon Lab: Hexagon Lab 1.1: Analyzing Blackout Data
To begin our investigation, we will start with the human stories. Open your lab document and complete the analysis of the blackout data to understand the context and impact of the crisis.

1.2 The Rules of the Game: Energy and Circuits

To analyze what went wrong with the grid, we first need to understand the fundamental rules that govern the flow of electricity. We can describe the behavior of electricity in a circuit using three key quantities:

Voltage (V): Often compared to pressure, voltage is the electrical potential difference that ‘pushes’ charged electrons through a circuit. It’s measured in Volts (V).
Current (I): This is the rate at which electric charge flows past a point in a circuit. It’s like the flow rate of water in a pipe and is measured in Amperes (A).
Resistance (R): This is a measure of how much a material opposes the flow of current. A thin wire has more resistance than a thick one. It’s measured in Ohms (Ω).

These three quantities are related by a fundamental rule called Ohm’s Law: $V = IR$. The rate at which electrical energy is transferred is called Power (P), measured in Watts (W). The key equations for power are: $P = IV$ and $P = I^2R$.

Using the analogy of water flowing through pipes, explain the difference between voltage and current.
A simple device uses a 9-V battery and has a resistance of 3 Ω. What is the current flowing through it?
What is the power consumed by the device?

1.3 Thinking Lens: Systems and System Models

An individual circuit is simple, but the electrical grid is a massive, complex system. We can use the Systems and System Models thinking lens to understand it. A grid has three main parts: generation (power plants), transmission (high-voltage lines that carry power over long distances), and distribution (local lines that bring power to homes and businesses). A failure in one part—like a frozen natural gas well (generation)—can cascade through the system, causing transmission lines to fail and leading to blackouts for consumers. By modeling the grid as an interconnected system, we can begin to understand how it can fail and, eventually, how to make it more reliable.

Chapter 1: Review and Practice

Vocabulary Consolidation

Term	Operational Meaning in This Context
Circuit	A complete and closed path for electrical current to flow.
Voltage	The electrical ‘push’ or potential difference that drives current.
Current	The rate of flow of electric charge.
Resistance	The opposition to the flow of current in a circuit.
Power	The rate at which electrical energy is transferred.
Energy Grid	The interconnected network for delivering electricity from producers to consumers.

Research Brief: Research Brief (Forecast)
With the initial context and foundational physics in mind, formalize your initial hypothesis. Open your Research Brief for Unit 1 and complete the 'Forecast' section, defining the problem in your own words and proposing a cause for the grid failure.

Problem Set: Problem Set 1: Circuits & Power
To master the rules of the game, complete the exercises in Problem Set 1. You will practice using Ohm’s Law and the power equations to analyze simple circuits.

How did thinking about the power grid as a ‘system’ change your initial ideas about the cause of the Texas blackout?

Now that we have explored the human impact of a grid failure and learned the fundamental physics of circuits, we are ready to dive deeper. In the next chapter, we will analyze the specific trade-offs engineers face and begin designing solutions to build a more reliable and equitable grid.