Electricity 101

Understanding electricity in the context of the grid

For this example we look at a single damn powering a small city. A microgrid with one energy source. The actual interconnected grid is fundamentally the same.

The Electron Dance

The key concept here - electricity is not a commodity, it is a service¹. It's not like gas which is piped to you as needed. It is more like heat from your furnace - created & delivered to you at the time you need it.

At a microscopic level, the flow of electricity is actually the movement of electrons through a conductor. When you plug in a device, you're providing a path for these electrons to flow, converting their kinetic energy into other forms of energy (light, heat, motion, etc.).²

It's important to note that the electrons themselves don't travel at the speed of light from the power plant to your home. Instead, they create an electromagnetic field that propagates through the wire at near light speed, causing electrons already in the wire to begin moving almost instantaneously when a circuit is completed.³

You can think of this as being similar to a garden hose full of water. When you open the faucet one end of the hose is connected to, water instantly comes out the other end. But it's not the water that just entered the hose.

The Birth of Electricity

At a hydroelectric plant, the potential energy of water is converted into electrical energy. As water flows through a penstock (a large pipe), it spins turbine blades connected to a generator. Inside the generator, magnets rotate past copper coils, inducing an electric current through a process called electromagnetic induction.⁴

This generates an electromagnetic field that runs through the wire. This electromagnetic field is potential energy that can be harnessed for various purposes.

Think of it like this:

1. The water's potential energy is converted into mechanical energy (spinning turbines).

2. Which is then converted into electrical energy (the electromagnetic wave).

3. That electromagnetic wave is energy, that when connected to a device, converts that wave into kinetic energy: physical motion (a motor), heat (space heater), or after conversion to DC (direct current), electronics.

Alternating Current

Almost all of the grid is AC (alternating current) at 60Hz⁵. For those that remember their math, it's a sine wave with 60 cycles/second. The voltage and amperage runs the gamut from 345+ kV to 120/240V delivered to your home.

An interesting side note, if we had the AC/DC convertors of today back when the grid was first built, it arguably (probably?) would have been all DC (direct current). But, reworking everything now with not just the entire installed grid, but all of our devices we plug in - not changing. There are however now several HVDC⁶ transmission lines and that will likely increase.

The Transmission Highway

Once generated, electricity needs to travel long distances to reach consumers. This is where transmission lines come into play. The voltage of the electricity is significantly increased using transformers, often to hundreds of thousands of volts. This high voltage allows for more efficient long-distance transmission by reducing energy losses.

Distribution: Bringing Power to the People

As electricity approaches populated areas, it enters substations where the voltage is lowered. From here, it flows through distribution lines—the familiar power lines you see along streets. Before reaching homes and businesses, the voltage is further reduced by smaller transformers, often seen mounted on utility poles or in green boxes on the ground.

The Delicate Balance of Supply and Demand

One of the most crucial aspects of the power grid is that electricity must be used at the same moment it's generated. Unlike water or gas, electricity cannot be easily stored in large quantities.⁷

This necessitates a constant balancing act between generation and consumption. If generation exceeds demand, the excess energy can cause the grid frequency to increase above its stable operating point (60Hz). Conversely, if demand outpaces supply, the frequency drops.

Both scenarios can lead to significant problems:

1. Overgeneration: Excess electricity can cause equipment to overheat and potentially fail. In severe cases, it can lead to widespread blackouts as systems automatically shut down to protect themselves.

2. Undergeneration: When demand exceeds supply, the grid frequency drops. If not addressed this will cause brownouts. To address it, there will be roving blackouts.

Maintaining the Balance

To keep the grid stable, operators use sophisticated systems to predict demand and adjust generation accordingly. They may bring additional generators online during peak hours or use demand response programs to reduce consumption when supply is tight.

In the case of our hydroelectric plant, operators can adjust the amount of water flowing through the turbines to increase or decrease electricity generation as needed. This flexibility is one of the advantages of hydroelectric power in grid management.

And yes there are batteries and other storage systems⁸ to take excess power. But those tend to be charged up overnight (non solar) or directly charged mid-day (solar) and generally have their charging and discharging times pre-scheduled.

If You Remember One Thing

The key issue that makes delivering electricity so difficult is that it's a service where the generation and demand must be kept balanced within tight constraints. And the demand is constantly shifting requiring the generation to shift to match - in real time.

looking down on a city from a hill - all buildings are brightly lit up - minimal traffic

1. In law there is contention as to if it’s a product or service. But everyone in the industry, that I’ve read, calls it a service.

2. How electricity is made

3. Introduction to Demand Generation & Response

4. How hydropower works

5. In the U.S. the grid is 60Hz. In Europe and some other areas it is 50Hz.

6. High Voltage Direct Current. HVDC & HVAC transmission lines are those giant pylons carrying lines high off the ground.

7. The Role of a Balancing Authority

8. We’ve had pumped hydro storage for decades.