Grid, Grid Everywhere, But Not An Erg To Drink

Everywhere you read it’s energy grid this, electrical grid that. The grid is getting smart, and clean. The grid can store energy. Two-way communications throughout the grid is commonplace, as are renewable energy sources. Microgrids are improving grid reliability and the overall grid architecture is becoming more and more distributed.

Yet looking out my window, nothing appears any different. Is my grid smarter or communicating or more distributed? Are today’s ergs somehow richer or more glamorous?

Distributed Is the New Black

No. Well, not yet anyway. But change is afoot! In the beginning there was the electrical grid, a truly dizzying feat of real-time engineering. Hit brew on your coffee machine and viola, it turns on. 120 volts at 60 hertz (in the U.S.) delivered to your doorstep from a dam or coal-fired power plant or nuclear power plant hundreds or even thousands of miles away. It’s magic!

Then there was the microgrid. A microgrid is a localized grouping of electricity sources and loads that normally operate connected to and synchronous with the traditional centralized grid, but can disconnect and function autonomously as physical and/or economic conditions dictate.[1] The scale of a microgrid is smaller than a traditional, centralized energy source like a coal-fired power plant. A microgrid might generate 1 to 10 megawatts into a 20 kilovolt distribution system, as opposed to 667 megawatts for an average coal-fired power plant into a 110 kilovolt transmission system on the centralized grid. Of course the service territory for a microgrid is smaller too, so its capacity can be smaller, matching a smaller demand.

Nanogrid Figure 2

And now we have the nanogrid. A nanogrid is an autonomous, self-contained grouping of electricity sources and loads that need not be connected to the traditional centralized grid, or microgrid, yet can be aggregated together and connected to the grid when the economic value of its available energy overcomes the infrastructure cost of the connection. As its name implies, we have moved the decimal on scale to the left a few more places. Nanogrid electrical sources are smaller still, from a few watts up to many hundreds of watts. More fundamentally, nanogrids are autonomous. They need no grid in the traditional sense, nor any of the costly infrastructures required to be grid-connected. They are able to generate their own energy, enough energy to perform their function, plus more in many cases. Examples include personal kinetic chargers like the nPower PEG product that can charge mobile devices, street side trash compactors like the BigBelly that use solar energy to compact garbage, solar-powered transportation fleets like eNOW Energy Solutions that generate and store enough energy to control the environment inside a trailer during transport, and outdoor lighting like Inovus Solar-Enhanced Lighting that captures solar energy during the day and uses it to provide lighting at night. Electric and hybrid vehicles may also qualify as nanogrids to the extent their batteries have available charge.

Connections Are the Key

Energy is becoming more and more distributed, even mobile in some cases, and autonomous. Yet being connected remains fundamental, whether grid-connected, control-connected or both. Being grid-connected allows a nanogrid to operate as just another electricity source on the grid, or redundantly alongside the grid, but the connection requires costly infrastructure. This type of connection is electrical. Control-connected is different. This type of connection involves two-way communications. Electricity sources and loads in a nanogrid communicate, coordinating behavior to insure autonomy. For example, a solar light directs its solar energy to one or more loads while the sun is shining, and may also top off the batteries when low. Then when the moon is shining, its behavior changes to run the loads off the batteries. So a nanogrid doesn’t need to be grid-connect, but it may be, and it is always control-connected.

Nanogrid Figure 3

Together We Stand

A single, autonomous nanogrid has at most a relatively small amount of energy at the ready. However, nanogrids can be aggregated. When the economics are favorable, large numbers of grid-connected and control-connected nanogrids can be summoned to wield large and meaningful amounts of energy. For example, all the electric vehicles within a county that are plugged in and have more than 10 extra kilowatt-hours of stored energy onboard can be selected and then targeted to deliver their energy to the grid during a 15 minute window in the afternoon while the natural gas peaker plant spins up.

Nanogrid Figure 4

A centralized aggregation point with detailed, near real-time information about these nanogrids is required for this example to be realized, but these can be high value uses for the highly distributed energy in nanogrids that warrant the economics of being connected.

Distributed Ergs

Outside your window things may not look any different today, but they will. It’s inevitable. The electrical grid must evolve. Energy generation is moving to the edge – to the county and city and neighborhood and commercial building and residential house – closer to the consumer. Your ergs may not be richer or more glamorous, but they will be less haggard from their travels.

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