Physics

How Does the Power Grid Work?

By: Hannah Pell

Being homebound during winter often means higher electricity bills for those of us north of the Sun Belt. And for many currently working remotely or attending school virtually, there may be added strain on top (although hopefully not to the same extent as the Griswold family’s infamous holiday lights). When so many aspects of our modern lives depend on electricity (which itself requires a massive, interconnected network to function every day), it can be easy to take it for granted.

As I cranked up the heat for the umpteenth time on this blistery, snowy afternoon, I wondered: How is it that I can simultaneously turn on my heater, flip a switch, and charge my electronic devices whenever I need to? How is electricity (almost always) immediately available, whether I want to plug in to the wall or the world wide web? What does it mean when it’s suddenly not available?

To answer these questions, we’ll need to understand the structure of the electric grid — one of the biggest machine’s in the world — and become familiar with those working behind the scenes directing electrical electricity wherever it’s needed in real-time. Additionally, while reliable access to electricity is something that many of us depend on, it’s important to realize that such access is not guaranteed or equitable everywhere.

The structure of the electrical grid

 The process by which electrical energy is produced and is delivered to you is generally divided into three stages: generation, transmission, and distribution.

Image Credit: U.S. Energy Information Administration, adapted from National Energy Education Development Project.

One of the basic facts of physics is that energy cannot be created or destroyed, so energy “generation” is really referring to converting thermal or kinetic energy into electrical energy. This is done at various types of power plants, including fossil fuel, natural gas, nuclear, hydropower, wind, and solar, which each have their own advantages and disadvantages.

Because these plants are often located in rural areas, the electrical energy needs to be transmitted efficiently across long distances. Transmission lines have intrinsic resistance, and longer wires mean larger voltage drops. We know from Ohm’s law (V = IR) that voltage depends on current and resistance. Power can be calculated as the product of current and voltage (P = IV). If we substitute Ohm’s law into this equation, we get P = I2R. Because current (I) is squared, reducing it is a more effective way to minimize power loss. Therefore, if we decrease the current, we’ll then need to increase the voltage for a given amount of power. This is why transformers first boost the voltage of the electricity when it leaves the plant — to minimize potential losses as it travels through the transmission lines.

Once the electrical power nears more populated areas, it’s then again stepped back down by a transformer at a substation to safer levels. Feeder lines connect residential houses to the transmission lines and the pylons which carry them. However, this isn’t the case everywhere — in some regions, power lines are instead buried in a process called “undergrounding.” Underground power lines, though more expensive, have the significant advantage of being less susceptible to weather conditions.

Grid operations


 Have you ever called your local utility to ask if you could flip on a light switch? I’d bet that you probably haven’t. Fortunately, electricity is managed on our behalf so that we don’t have to.

Electricity is directed via the grid by balancing authorities. Balancing authorities are responsible for ensuring that electricity supply meets local demand and that the voltage and frequency of the supplied power are accurate (the U. S. standard frequency is 60 Hz). Electricity cannot be stored, so directing it to where it will be utilized are decisions that independent system operators (ISOs) and regional transmission organizations (RTOs) make in real time. The balancing authorities utilize historical data and weather forecasts to model electricity demand so they can anticipate electricity needs to avoid blackouts or brownouts, which occur when local supply and demand are unbalanced.

Private companies and public utilities participate in power generation and transmission as well. The dynamics of these behind-the-scenes organizations is complex, but what’s important to know is that there are people ensuring that the electricity that is needed is efficiently and reliably provided.

Decarbonization and equitable access to affordable electricity


 However, it’s important to note that having such immediate access to electricity is not the same everywhere. According to the International Energy Agency, there is “no single internationally-accepted and internationally-adopted definition of modern energy access,” but there are efforts to study and quantify this inequity. According to Our World in Data, there were 940 million people (13% of the world’s population) in 2016 who did not have access to electricity. The United Nations has set a goal to “ensure universal access to affordable, reliable and modern energy services” by 2030.

Climate change is also a related issue because electricity production has long-term environmental consequences. Decarbonizing these electricity generation sources (the types of power plants I listed earlier) will be key to reaching net-zero emissions in the coming decades. Therefore, increasing equitable access to affordable electricity will be critical throughout our just transition to clean, renewable energy sources.

So next time you turn on your heat or plug in a device, remember that the electricity you’re using was produced, transmitted, and distributed to you almost instantaneously from a far away rush of water or burning fuel or fission reaction. Electricity is an integral part of our modern lives, and the grid is a tremendous feat of engineering that we rely on each day. As we work to upgrade the grid by making it “smarter”, increase the output of renewable energy sources, and shift to microgrids, how we get our electricity in the future may look very different from the grid we have today.

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