The Smarts Behind the Smart Grid

The Smart Grid is a pretty abstract thing. I thought I would write a few posts explaining some of the ways it plays a critical role in enabling a more efficient, more reliable and more flexible power system.

We Say "Jump!", they say "How High?"

Today's power plants generate electricity on demand. But how do they know they need more or less?

Partly, they predict based on weather, time of day, historical data, trends, and knowledge of the states of other power plants. Like a weather forecast, it's not very accurate, and subject to change. Unlike a weather forecast there can be dramatic, unexpected changes, such as an outage at another plant, or a storm, or steamy weather. In short, prediction is a good guess at best.

But the more specific way a power plant knows it needs to deliver more or less power is by measuring the delivered voltage. The plant produces enough voltage to ensure that all customers get at least 114 Volts. If everyone turns on the lights at the same time, voltage will drop, so they'll throw on a few shovels of coal and generate more.

This system works almost all of the time. It's about as smart as a chicken.

Ready For The Unexpected

One of the costs associated with the inability to predict demand accurately is that the utilities always have to be ready to produce more power. Once a plant is up and running, they can juice things up pretty quickly -- 5 or 10 minutes can bring on more power, but it's idling, or "spinning" until then. Consider:

  • A power plant that is up and running, but producing nothing, is running at 0% efficiency
  • A given plant has an optimal production level; producing more ... or less is inefficient
  • All plants have a maximum output, at some level of demand, you need another plant to come online
  • It takes a long time to "turn on" a plant from being off, so some plants are left to idle, not producing any power, but using fuel
  • The most efficient and reliable plants are used first; as demand increases, older, less efficient plants are brought online
  • We have relatively little spare capacity since our demand for power has been growing faster than we are building new plants

There's a lot of inefficiency in this process, of which some is due to our inability to accurately predict or even know actual demand, predict and even communicate failures, and generally know what's going on. The Smart Grid helps reduce or eliminate many of these inefficiencies.

114 Volts, Plus or Minus

As I noted, the power plant generates enough voltage to ensure that all customers get 114 Volts. They have no way of knowing that customers are actually getting that exact voltage, other than through various models (fancy spreadsheets) based on the various factors they can measure. Their last chance to control overall voltage is at the closest sub-station to the customer. But voltage drops as it travels further. So the customer close to the substation gets more voltage, and the one at the end of the line gets just enough.

The problem is that most appliances are optimized for a certain specific voltage. They'll work if they get more (which is the usual case), but tend to throw off the excess as heat. You pay for that electricity -- it's just a really lousy way to heat your house (especially if the device you're running is an air-conditioner).

How The Smart Grid Helps

The Smart Grid helps by changing a one-way communication system into a two-way system. Unlike regular meters, that merely keep track of the amount of electricity used, Smart Meters communicate back. The Smart Grid is able to use this feedback to provide instantaneous information about demand. This information can be used to be smart about how to use the available power -- rather than just increasing overall voltage (using more fuel), the Smart Grid lets voltage get routed to exactly where it's needed when it's needed. Smart Meters can even play a part in this, actually being mini-sub-stations that route excess voltage down along the line.

So with a huge amount more information, the right amount of power can be generated, then the right voltage can be routed. Fewer plants need to be idling, and more plants can run at closer to their peak efficiency.

These are just a couple of ways that the Smart Grid plays a critical role in our power generation future.