Today, we will continue with the theme of energy transition! We will focus on the electrical gird, a crucial piece of the puzzle in decarbonizing the energy sector.
This deep dive series about the grid has two parts:
Part1: How do we get electricity from the power socket? (how does the grid work?)
Part 2: What challenges and solutions are there in decarbonizing the grid?
Before we start learning how the grid works, we have two exciting announcements to make!
Pauliina is looking for a technical co-founder
Greetings from Pauliina:
Hey everyone! After running this newsletter and my climate tech consultancy since last May, I’m ready to take the next step:
I’m looking for a technical co-founder to build a science-based climate startup!
🌍Goal To build a science-based startup that: 1. can reduce or remove a minimum of 0.5Gt CO2e annually 2. is (preferably) based on a chemistry/biotechnology-enabled hardware solution
🧪🚀Whom I am looking for? An awesome technical co-founder who: -has ideated/developed a science-based climate solution (researchers, scientists, inventors!) -wants to partner up with a commercial co-founder (me!) to scale their solution -has a background in chemistry/biotech/electrical or mechanical engineering -is passionate about solving the climate crisis
The Survivaltech.club newsletter will continue normally for the time being. Together with Matteo, we already have a lineup of exciting deep dives and interviews to share with you in the upcoming months!✨
We are holding the second community meetup today! 🌍
At the meetup, you will have the chance to meet like-minded people who care about the planet and love Climate Tech. Don’t miss this opportunity!
Register for the Community Meetup at the link below!
Now, it’s time to start learning about electricity and the grid. I hope you will enjoy the article. Let’s go! ⚡
The Electrical Grid: Part 1
What is electricity?
Electricity is a physical phenomenon associated with the presence or motion of an electric charge. On the other hand, an electric current is the flow of electric charge through a surface or volume.
We use electrical current to power our phones, computers, EVs, lighting, heating, cooling, refrigeration, machinery, and public transportation systems.
There are two types of electrical current:
Alternating current (AC)
Direct current (DC)
In AC systems, the movement of electric charges periodically changes direction. The electricity that flows in the grid is usually in the form of AC.
In a DC system, the movement of electric charge happens in a single direction. DC is used to charge batteries, and hence it powers virtually every device that we own. Therefore, all the everyday devices contain AC-DC converters that take the grid’s alternating current and transform it to direct current to charge their batteries.
This video gives a great overview of electrical current:
After this brief introduction to electricity, let’s have a look at how the grid works!
The overview of the grid
In many countries, we take for granted that we can recharge our laptop at any time and constantly power our fridge. That’s thanks to the electric grid.
However, how many of us know how the grid works? Next, we will have an overview of the grid and understand how its main building blocks work.
The grid can be divided into four main parts, as shown in the figure below:
1. Generation: The electricity journey starts at the generating station, whereelectricity is produced. A generating stationis, for example, a wind power plant, a nuclear reactor, a coal power station (sigh!), etc.
2. Transmission: The second part is about transmitting the electricity from the generating station closer to the consumers. Transmitting electricity is done in the transmission network. When the electricity exits the generating station, it gets converted to a (typically) higher voltage level to be transmitted to consumers. This conversion is done within an electrical substation by a step-up transformer.
Electricity is transferred at high voltages to minimize the energy loss in long-distance transmission lines. Before reaching consumers, the produced electricity may need to travel hundreds of kilometers through the transmission lines.
3. Distribution: Once close to consumers, the electricity voltage level is reduced again in an electrical substation through a step-down transformer. At this stage, the electricity is ready to power industrial consumers. Then, the voltage level is further lowered with a step-down transformer to serve residential consumers.
4. Consumption: Yay! The electricity has arrived and is ready to power our lives at home and work!
This overview of the grid is simplified to give you a basic understanding of the system. Now, let’s dive deeper into the main building blocks of the grid and their roles.
Components of the grid
Generating stations are responsible for producing electricity.
There are multiple energy sources for producing electricity. The most common ones in order are:
It is worth noting that an increasing amount of electricity users also generate energy with, for example, solar panels on their roofs. This adds complexity to managing the grid as not all the electricity is generated centrally at large power stations. Check out this video about Distributed Energy Resources (DER) to learn more.
Our World in Data shows the global electricity production by the energy generating sources as follows:
Sadly, we notice that approximately two-thirds (63.3%) of the electricity generation is powered by fossil fuels, with coal and gas making up for the largest chunk. Low carbon solutions account for 36.7% of electricity production led by hydropower and nuclear. On the other hand, wind and solar are still limited in electricity generation and make up less than 10% globally.
The generation of electricity from fossil fuels causes huge amounts of greenhouse gases. Breakthrough Energy estimates the CO2 emissions caused by electricity to be as high as 27%, making it the second most polluting sector on earth.
Transmission lines enable electrical energy to move from a generating station to an electrical substation closer to consumers. Together these transmission lines form a transmission network.
A transmission network is responsible for moving electricity over long distances. During transmission the electricity has a voltage of 110kV and above to avoid energy loss. So once the electricity leaves the generating station, the voltage is increased with a step-up transformer.
The voltage level may vary within the transmission network. If we take Switzerland as an example, we notice that the overall transmission network features three different voltage levels: 380 kV, 220 kV, and 150 kV (see figure below).
Wait, why does transmitting electricity at high voltage minimize energy loss?
You might remember the following formula from your school books: power equals the voltage times the current.
If a power station sends out electricity at a voltage (V) and a current (I) flows in the transmission lines, then the power equals voltage times the current.
Transmission lines, however, have resistance. Hence, a power loss happens according to the following formula:
To avoid power loss, we should lower both the current and the resistance of the transmission lies.
We can transmit the same amount of electrical power using a lower current by increasing the voltage (see formula 1). This is exactly why the voltage is increased with a step-up transformer before transmission.
Low resistance is also important to minimize energy loss. Resistance of the lines depends on the material of the cable, the amount of current flowing, and the length of the transmission line.
Wikipedia gives us a ballpark for the resistance-related losses. If we want to carry 1000 MW of power for 160 kilometers at a voltage level of 756 kV, we can expect energy losses below 1.1%. On the other hand, if we would do the same at a voltage level of 345 kV, the losses would total 4.2%.
Once the electricity is near the end consumer, the voltage is decreased with a step-down transformer.
The distribution network is divided into two parts based on the voltage.
1. Primary distribution
Primary distribution serves large industrial consumers, such as factories. The voltage in primary distribution ranges from 4kV to 35kV. The primary distribution also feeds electricity to small substations that further lower the voltage for the secondary distribution.
2. Secondary distribution
Secondary distribution supplies residential consumers (like you and me! 😀). The voltage level varies between countries; however, in Europe, consumers are provided electricity at 50Hz and 230 V.
It is important to distinguish the transmission network from the distribution network. The transmission network deals with high-voltage electricity and moves electrical energy over long distances. On the other hand, the distribution network is responsible for dispatching power from electrical substations to the consumers.
Substations transform the voltage level of the electricity and/or perform other functions.
We can distinguish between several types of substations. The four main ones are the following:
Step-up substations: These stations are linked to generating stations. The electricity is generated in lower voltages, which needs to be stepped up to feed the electrical energy in the transmission lines (to avoid energy losses!).
Step-down substations: These stations lie between the transmission and distribution network. They are responsible for lowering the electricity’s voltage for consumers.
Both step-up and step-down substations are based on transformers. A transformer increases or decreases the electricity’s voltage. This video gives a clear overview of how transformers work.
Converter substations: Converter substations modify the frequency of the electrical current and convert AC to DC and the other way around. For example, a converter substation is important for photovoltaic plants. A solar panel generates DC electricity, which needs to be converted to AC before feeding into the grid.
Switching substations: A switching substation is mainly used in case of failures for switching backup lines.
Electrical Grid Control
The electricity’s production and consumption must be in balance for the grid to work. This is because there is still very little energy storage available.
To achieve a balance between electricity production and consumption, the grid must be constantly monitored. This is done in grid control rooms with the help of software.
If electricity consumption increases or a power plant fails, grid control allows generating stations to feed more energy into the grid. In case of a lack of energy, algorithms in the grid control rooms decide which generating stations are best suited to feed more electricity. These algorithms select the best offers based on a certain generating station’s price. On the other hand, if consumption drops, the control room feeds less energy into the grid.