We need to upgrade our grid!

The grid needs to be more reliable!

We need a smart grid!

As we decarbonize our energy mix, the demands of the grid are growing.  Understanding even the basics of the grid makes it easier to understand the discussions taking place about the grid and the impact it has on our everyday lives.

Overall, the grid is what delivers electricity from the source that generates it to the devices that consume it.  The grid is made up of various components.  Within the figure gallery at the end of this blog post, Figure 1 shows a simplistic view of the conventional grid.

At one end, it starts with an electricity generating source.  This can be from coal, natural gas, nuclear, solar, or wind.  The electricity generating source connects to transmission lines that transport the electricity to where it will be consumed.  However, before it gets there, it is brought to what are called substations.  The electricity is then carried by distribution lines to homes and businesses.  So within the grid between the electricity source and the consumer, there are transmission lines and distribution lines - two distinctly different sets of wires carrying electricity.

I need to get a little wonky now.  Not to worry.  It is not that bad.

The wonkiness begins with describing the technical term of voltage as it is a key characteristic of the grid.  Voltage is a form of potential energy.  (See “What is energy?” to learn about potential energy.)  Like water pressure flowing in a pipe, voltage is the pressure associated with the movement of electrons making up the electricity.  Voltage is measured in units called volts and abbreviated with the letter "V".  To provide a sense of magnitude, US homes are typically wired for 120 volts. 

Transmission lines carry 44,000 volts (which is 44 kilovolts or KV) to 735,000 volts (735 kV).  When connected to substations, the voltage is reduced  through a combination of devices called transformers that lower the voltage for the distribution lines to finally deliver 120 volts. 

That's the end of the wonkiness.  See, it wasn't that bad.

You probably have seen the components making up the grid but never gave it much thought.  Transmission lines are those tall towers whose wires run long distances. (Figure 2)  Large substations house transformers and are connected to transmission lines.  (Figure 3)  Small substations contain transformers and are connected to distribution lines. (Figure 4)  You also see distribution transformers on poles (Figure 5) and in places where electrical lines are underground, you see transformers on pads as they deliver electricity to end consumers.  (Figure 6)

The additions of solar and wind farms are requiring  changes to the grid - not only from a physical perspective but also from a business model perspective.

The business model impact involves the management of the transmission lines.  In the North America, there are three electric grids - the Eastern Interconnect, the Western Interconnect, and the Texas Interconnect.  (Figure 7)  These three separate grids actually come together to create the full North American grid.  While all three of these grids are connected to various degrees, they are operated independently.

The connections between the grids is significant in a number of ways.  For example, should there be electricity shortages in one interconnect region, the others can assist in picking up the slack - to a degree as it depends on how big the connections are.  

Relative to solar and wind farms, utility-size farms are going to be located where the sun shines the brightest and the wind blows the hardest.  Those locations are typically not in the same location as current generators.  In order to bring the electricity in from the utility-size farms, new transmission lines need to be built  along with greater connections among the three grids.  And with greater connections between the three grids, the management of the interconnections needs to be enhanced.

From a physical perspective, solar and wind generated electricity can connect directly to the distribution grid as opposed to the transmission grid.  This is true for smaller solar and wind installations.  Connecting to the distribution grid introduces a number of issues.  Two major issues are (1) how those connecting to the distribution grid pay for their share of maintaining the distribution grid and (2) how much those connecting should get paid for electricity they are putting onto the distribution grid.  (See "Rooftop solar and net metering - unfortunately, not so simple". )

From all of this, our depiction of the grid goes from what was shown in Figure 1 to Figure 8.  Note the addition of solar and wind connected directly to the distribution lines.

The electric grid brings electricity from its sources to those who consume it.  As we decarbonize our energy mix, the demands of the grid are growing.  We need more transmission lines. We need greater interconnectivity between the three grids.  We need enhanced business processes in managing the greater interconnectivity.  We need fair and equitable regulations in dealing with connecting electricity sources to the distribution grid.  Understanding the basics of the grid makes it easier to understand the discussions about these issues as it impacts our day-to-day living.