Electricity is always there

We take it for granted that when you plug into an electric socket, there will always be power available. Hopefully by the end of this topic you will have some appreciation for how amazing that is!
State Farm

The electric grid

In the developed world, we get electricity from a complicated grid connecting generators and consumers...

...in which there is NO ENERGY STORAGE.

Question: Since everyone is switching things off and on all the time, is our utility constantly ramping power up and down every second, every millisecond of the day?!?!

Household usage

How much electricity do you use throughout the day? When is your "peak" usage?


Here is the electricity demand from one household (in Britain) on one day. It sure looks "spiky"!

What strikes you as interesting or unexpected about this household?

Hopefully you can identify on this graph things like...

  • When people in the household were asleep.
  • When they got up.
  • When they were most likely away from home.

Luckily, when you put many people's usage together, a lot of the spikiness is evened out. There are still variations throughout the day in demand, but things vary a bit more slowly, and become more predictable. Here is the electricity demand from one utility, supplying many thousands of people, over the course of one day in October:

Utilities

  • typically own and maintain the grid and electric generators.
  • are often regulated monopolies.
  • participate in a regional transmission network that allows them to buy and sell electricity from other utilities.

We can mentally divide up the electricity demand like this:

Base power or baseload power: Even at night, there is demand for electricity. Total demand never drops to zero. There is a minimum amount of electric power consumed around the clock.

To supply this power, generators that can run continuously, and use cheap fuel, are used. These generators are being used *all the time*. They are generating electricity, which utilities sell, so they are generating revenue for the utility *all the time*: They are the biggest money makers for the utility.

On a hot afternoon, when the temperature peaks, lots of folks want to run their air conditioners all at the same time...

Mussi Katz

The power company can burn fuel at a faster rate to try and keep up. But once a generating plant is running at full capacity...

The power company next has to turn on another generating plant to supply the demand for the additional electricity.

Peak/intermediate power: To provide the extra power above the base load, a utility needs a power source that can be switched off or on, or "dispatched" relatively rapidly. This power costs the utility more to generate: They must still lay out the money for generators that can cover the maximum energy demand, but for night, and perhaps large portions of the day, those extra, or peak power generators might be switched off and during those periods the generators are not making any electricity that can be sold.

Dispatch time refers to how fast a generator can be turned off/on to generate electricity. Read this article on Dispatchable sources of electricity and answer these questions:

  1. Rank these kinds of electric generators from quickest to turn on (and off!) to slowest to turn on (and off): Coal, Hydroelectric dams, Natural gas turbines, Nuclear power plants.
  2. What other questions occurred to you as you read that article?

In a pinch!

When all else fails, utilities can fall back on their regional transmission grid to buy power from other utilities. On normal days, there is usually some back and forth.

But this fall back to others on the same grid failed spectacularly in Texas in February 2021! during an extreme cold snap.

Write for 2 minutes:

  • What's one example of a positive impact of the federal government (or government more generally) on your life?
  • What's one example of a negative impact of the federal government (or government more generally) on your life?

It turns out that as you boost the voltage in any electrical circuit, you reduce the current flowing, and this reduces the energy losses due to resistance in the circuit. A typical long-distance transmission line runs at 345,000 volts, but they can go as high as 1,200,000 volts. Above 2,000 kV you have to start worrying about "corona discharges"! But high voltage DC becomes attractive for really long distances. Nathan Pauls, for the GC Record - "Power transmissions being replaced after a century".

Such high voltages can more easily electrocute humans, so household voltages are stepped down to a modest 110 V in this country.

The Grid(s)

The U.S. Energy Information Administration (EIA) used to provide forecasts for about a day in advance of expected electricity demand. More recently they have computerized and automated the process, and now provide this real time map of national grid operating data. Use the real time map to answer these questions...

Look at the U.S. change in demand from prior hour graph.

Look for the three major grids "Grid interconnection areas" : Look for the AC-DC-AC ties at the border of each grid

  • The Eastern interconnection
  • The Western interconnection
  • ERCO or ERCOT (Electric Reliability Council of Texas)

Run the animation (starting at midnight, Eastern Standard Time). Can you make sense of what you see? How is the change different in the western and eastern half of the country? Why?

Look at the "U.S. electricity generation by source graph.

  • Total generation: Roughly what time of day are the two peaks in total generation?
  • Renewables: Roughly what time of day is peak solar energy production? Peak wind energy production?
  • What energy source is most nearly constant?

>Look at the U.S. electricity interchange with neighoring countries.

Which country do we have the most exchange with? And are we more often sending or receiving power from them?

  • The Commerce Clause - The Federal government has authority to regulate intrastate commerce, but supreme court decisions have ruled that its ability to regulate commerce within states is limited.

Texas limited interconnections with the rest of the country so as to avoid Federal regulation of its electrical grid.

Renewable energy sources!

Wind is intermittent and unpredictable.

Total output, in MW, of all the wind farms of the Republic of Ireland

Solar[*] is also intermittent. Of course, solar energy is never on at night. But it is naturally on during parts of the day. That is to say, it is naturally behaving somewhat like a peak power generator, and this is typically the priciest kind of power generation for a utility.

Both Solar[*] and Wind are non-dispatchable energy sources. That is: A utility cannot turn them off or on at will.

    [*] When most people talk about "Solar energy" they mean Solar Photovoltaic panels. You probably noticed that "Solar thermal plants" were listed in that article about dispatchable sources.

    Pause to look up different ways to take advantage of the sun's energy. Do a bit of internet research and come up with a one- or two-sentence description for each of these kinds of systems:

    • Grid tied solar installation.
    • Stand alone (or off-grid) solar installation.
    • CSP solar system.
    • Passive solar heating.
    • Solar hot water system.

    Also: One of the kinds of systems above is the same as a "Solar thermal plant" that can store energy in the form of heat, so that *is* dispatchable: That is, it can be turned off and on. Which one is it?

The systems in the list above with the lowest up front costs are grid-tied solar installations--in Northern Indiana these are the most common solar panels you've seen on roofs around Goshen--and solar hot water systems. So, these are the most common systems that home owners buy and install.

In addition to the kinds of systems listed above, we can also think of biomass as a way of harvesting solar energy:

  • You can grow corn (with sunlight!) and make a fuel--ethanol--out of the corn, which can be burned in automobiles.

    The problem with this, in our country, is that you are using not only sunlight, but also lots of fertilizer--made with fossil fuels--to grow the corn. Brazil is closer to the equator with more sunlight, and they have grown sugarcane and converted it to ethanol with fewer fossil fuel inputs than corn.

  • You can grow plants to be burned, to heat water->steam, to generate electricity.
  • You can (someday economically?) grow algae which make biodiesel compounds. (That idea is still be researched and developed. See GC's AlgaeTown project).

Strategies to level the load

The strategies that utilities can use to supply electricity reliably can roughly be divided into:

  • Managing supply - dispatchable power and energy storage.
  • Managing demand - things like offering incentives for consumers to use energy at off peak times.

Managing supply

Above, we looked at traditional (and not-so-tradition solar thermal) ways of turning off and on different kinds of generators to accommodate changing loads. Most of these are currently fossil-fueled generators, including coal, diesel, gas turbine plants (but not nuclear or solar thermal).

One *more* kind of generator that can be turned off and on as needed is more common [**] in Europe than in here: Germans incinerate 37% of their waste, generating electricity and heat (see "district heating"). A waste-to-energy incinerator in Hesse, Norbert Nagel / Wikimedia commons, via e360

Energy storage on the grid

If we could store all the energy that renewables generate in a battery, then we could dispatch energy from the battery when the load increases. There are a variety of ways to do this:

  • Pumped storage - This is the cheapest solution, and one that has already been demonstrated to work: The idea is to pump water uphill when energy is cheap, or when renewable energy is generating generously, and then allow the water to run back downhill through a turbine (just like hydroelectricity) when electricity is needed. Below is a picture of the Dinorwig pumped storage facility in Wales (Britain)

    About 70-80% of the energy input can be recovered.

    The main reason why this hasn't been more widely deployed is that you need both water for pumping, and a lake or basin as far above the surrounding countryside as possible. There is one such pumped storage facility in Ludington, Michigan Also the image source.

  • Hydroelectric dam "storage" This a variation on pumped storage and is also *already working*:

    On one particularly windy day, Denmark was producing 40% more electricity than national electric demand from its prolific windfarms.

    Nearby Norway has a lot of hydroelectric dams. The two countries grids are interconnected: When Denmark has a lot of wind it sells to Norway, which turns off its hydroelectric dams. When the wind stops blowing in Denmark, it buys hydroelectricity from Norway.

  • Electric battery storage This is the easiest technology to understand. It's still rather expensive, but prices are dropping. It's starting to be used in places like Hawaii. Why Hawaii? It has the most expensive electricity in the U.S.--33 cents/kWh vs 13 cents/kWh in Indiana--because all of their fossil fuels must be imported from far across the ocean.

    Instead, they are starting to buy expensive batteries along with cheap solar panels, which comes out cheaper than paying the high costs of importing fuels across the ocean.
    3blmedia

  • There are other storage options [with fun cartoons!] to be considered.

Demand management

The other way that utilities can try to balance the load is by trying to convince consumers to change when / how much electricity they use.

  • At right: NIPSCO will pay you $50 for your working fridge, no questions asked. When you buy a new refrigerator, it has to meet federal "Energy Star" standards. New refrigerators are more efficient than 10- or 20- year old refrigerators.

    Many utilities offer such programs, in which they pay their customers to be more energy efficient, and use less electricity!

    How in the world does this make sense economically, when a utility earns money by selling electricity?!?!

    The way it works: state regulatory boards will sometimes allow utilities that can prove that they have invested in effective energy savings programs to charge higher rates.

    If the regulations are designed well, utilities find that investing in energy savings programs is cheaper than investing in new generation capacity, and has a better ROI (Return on Investment).

    It's true that their customers are now paying more per kWh of electricity. But if they took part in the efficiency programs, customers' appliances or homes are more efficient, and so they still pay less money to the utility each month.

  • A utility might try to shift demand to a time when energy demand and their generation costs are lower (like weekends, see right) by offering financial incentives.

    Many Texans can get free electricity at night.

    This might be a good deal for you if you can shift your electric use to nighttime, if you can set your dishwasher to run at night, or you have an electric car to charge while you're sleeping!

    Why free in Texas and not in Indiana? Texas has more wind energy capacity than any other state. Often the wind is blowing at night, when people aren't using all the energy that's available.
Investigate your utility's energy savings plans: Look up the website of NIPSCO (Goshen's utility) or the electric utility where you're living. What kind of energy savings (or energy rebates, or energy efficiency) programs do they offer? Pick a program where the customer will actually receive some sort of financial reward. Describe how it works and paste in a URL.

Government policies to encourage greater use of renewable energy


Net metering allows businesses / homes with solar panels to connect to the grid and sell power. (The homeowner no longer needs to buy batteries!)


Renewable portfolio standards refer to state laws that mandate that a certain percentage of electricity generated must come from renewable sources. (Market for 'certs').

Wind variable, Not under the control of grid operators. With enough turbines / steady winds can have greater up times.

Solar variability, matches peak loads, systems with storage or without.

Image credits

Alternative energy news, M-power (UK), U.S. EIA, Denis Egan c.jannou Wind power of Ireland