Preparing the Grid for Renewable Energy: Electric Warehouses

Updated: Apr 20

Last post, we discussed the importance of levelized voltage control as renewable energy sources become more common. This is because renewable energy is dependent on factors that are out of our control (like shade or non-windy days). Our recommended (and non-invasive) solution to help deliver consistent power quality are voltage control modules. However, this is not the only change that the grid needs, and even more new technologies must be developed and implemented for the grid to be ready to fully adopt renewable energy.

Electric warehouses are another new technology that will enhance, or even replace, traditional substations for delivering consistent power. In addition to the components normally found in a substation, new electric warehouses will include energy storage modules to store backup power. These large-scale units will release energy when power supplied by renewable energy sources drops, such as on a rainy day.

In this post, we’ll take a deeper look at how electric warehouses will work and why they’re a necessary update to the grid. This post gets a bit technical, so feel free to contact us if you have any questions.

What is an Electric Warehouse?

An electric warehouse is an emerging concept that includes a collection of components usually found in a substation (incoming lines, transformers, circuit breakers, outgoing lines, etc.), along with some new technologies. To become a warehouse, energy storage modules will be added to substations to provide back-up power when not enough power is available. Additionally, voltage control modules will also be incorporated into electric warehouses.

Electric warehouses will allow us to integrate renewable (and variable) energy from three key sources: distributed energy resources (DERs), such as rooftop photovoltaic (PV) systems or wind turbines; remote power supplies from central generating stations, such as hydroelectric dams or nuclear power plants; and energy stored at the warehouse.

Electric warehouses will provide much more flexibility than traditional substations because of the variety of energy sources that can provide customers with power.

Electric Warehouse Designs

While substations are designed to transfer power, electric warehouses are designed to provide uninterrupted power. Therefore, electric warehouses will be rated in mega-watt hour (MWH) capacity rather than transformer mega-volt-amperes (MVA).

Electric warehouses will be transmission class (100 KV and higher) and distribution class (less than 100 KV). Figure 1 illustrates two prototype electric warehouses. Mountain Electric Warehouse is a transmission class warehouse. Valley Electric Warehouse is a distribution class warehouse; we will focus on Valley Electric Warehouse throughout this post.

This distribution class electric warehouse is assembled with two 50 MVA transformers and two 1200 MWH energy storage modules, providing 2000 MWH of power. As you can see in figure 1, power flows into Valley Electric Warehouse via the 138 KV Powerway. Some of this power is stored in energy storage modules 1 and 2. Power flows into and out of the storage modules at different times. Figures 2 and 3 illustrate when power would flow into the energy storage modules to charge them, and when power would flow out of the storage modules to be used by consumers.

Electric Warehouses Regulate Energy Supply

Figure 2 shows an electric warehouse’s typical peak load on a summer day. Total load is represented by the orange line. The green line shows DERs, in this case rooftop PV. These rooftop solar panels actively provide power between the hours of 5:00 a.m. and 9:00 p.m., the approximate times of sunrise and sunset. After dark, energy is released from energy storage modules, as represented by the yellow line.

The blue line shows power that is provided from remote energy suppliers by way of the transformer. As you can see, remote energy always supplies some of the power at electric warehouses. During the day, remote energy is recharging the energy storage modules, represented by the black line. At night, remote energy supplements the energy being discharged from energy storage modules.

Figure 3 shows the same data as that in figure 2, but with one key difference. Around 11:00 a.m., an underfrequency event occurred, meaning that power system frequency dropped from 60.00 hertz to 59.95 hertz. This may have been because winds became calm and power produced at windfarms decreased.

Between 12:00 p.m., when the power system frequency dropped, and 2:00 p.m., when the issue was resolved, energy was provided by a different source: energy storage modules. The modules are equipped with DIP (differential, integrated, predictive) controllers, which detect the lack of energy from the power grid and signal for the modules to go into support mode. DIP controllers will signal for modules to enter support mode whenever power system frequency decreases to 59.95 hertz or below. Once in support mode, energy storage modules discharge energy so that consistent power can be delivered to consumers.

At 2:00 p.m., when the issue with the power grid was resolved, DIP controllers signaled that energy storage modules should return to charge mode.

The Advantage of Electric Warehouses

Because electric warehouses will be designed to provide uninterrupted power, energy storage modules can be created with specific power level storage capacities in mind. In an emergency in which power from the grid is unavailable, an electric warehouse could supply energy to consumers for set amounts of time using the power stored in its energy storage modules.

For example, if the grid fails during peak summer loads, energy storage modules could provide uninterrupted power to consumers for two days. During peak winter loads, power could be supplied for three days; during spring and fall, power could be supplied for five days.

Electric warehouses will allow much more flexibility during all operating conditions. For example, if a major rainstorm blocks the sun for a day or two, operators can decide to stop loading energy into energy storage modules to reduce the demand on the power grid.

Electric Warehouses are the Future of Substations

The need for electric warehouses already exists, as does the ability to make them a reality. When substations are converted to electric warehouses with energy storage modules, smaller transformers can be purchased and installed, and fewer transformers will be needed. The capacity of each transformer will also be reduced. Not only will electric warehouses allow us to easily integrate renewable energy, they will also increase the flexibility and operability of the entire electric power grid.

Electric warehouses will be a game changer for the electric power industry. If you’d like to learn more about electric warehouses, or consider implementing one into your substation, contact us. We’d love to discuss the opportunities and advantages at greater lengths with interested parties.

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