A fraction of a second ago, water, gas, wind, or other energy from hundreds or thousands of miles distant powered your lights, air conditioning, television, refrigerator, and practically everything electric around you.
Los Angeles light switches can spin Washington turbines. Electric networks, which span continents, have no slack. Water systems have some spare supply in a storage reservoir at the treatment plant and some additional supply in the pipelines linking the treatment plant to your home—supply just has to roughly match demand—but electricity does not. Anything hooked into the grid uses power from the grid. Let’s see how Glenwood Springs’ public library turns on its lights. The large demand unpredictability from minute-to-minute and month-to-month makes turning natural fuels or phenomena into electric power problematic.
Trends exist. The yearly peaks correspond to climate—January is the winter high-water mark as many houses and businesses switch on their electric heaters, while July is the summer high-water mark as the country fights the heat with air conditioning. Yet, the gap between the peak and lowest demand months is just a third. Daily variation dominates.
All US areas see a two-peak daily demand pattern in January, when people get up and turn on lights and appliances around 7:00 AM. After work, demand rises again. In July, energy usage peaks in the late afternoon or early evening, depending on the location. In the warmer Southwest, use peaks about 4:00 pm, when air conditioners work hardest.
The temperate northwest, including Colorado and that Glenwood Springs public library, has fewer air-conditioned buildings, so demand peaks around 6:00 pm due to post-work appliance, light, and TV use. Holidays and special events complicate these trends—for example, on Superbowl Sunday in the US, demand drops for a few hours when people turn off the lights, stop cooking, and assemble at others’ houses to watch the game. So, utilities must consider hour, day, season, location, and more when estimating demand. Utilities must immediately meet demand. They stack energy sources for this. Nuclear power is usually the bottom. Nuclear power reactors require a day to shut down and restart, making demand-based operation impossible. Due of their high cost, letting these stations sit inactive would be wasteful. Except for regular maintenance, they’ll run practically constantly during their service lifetimes.
They deliver the most reliable electricity 24/7. Colorado runs six coal power stations but no nuclear power facilities. Most coal plants, like nuclear, require time to heat up, so utilities operate them continually. Coal and nuclear power the base-load. Their continual manufacturing matches the day’s lowest demand. In hot summer afternoons, utilities require quicker production techniques to power all those AC units. Gas-fired plants do most of this. 13 of Colorado’s 25 stations use simple cycle combustion turbines.
The fuel spins a turbine, which turns a generator, which generates energy. Simple cycle stations are utilized for fast applications since more modern natural gas power plants recover hot exhaust to generate energy, but starting takes longer. Most attain maximum power in 15 minutes, making them useful for brief demand peaks. Traditional electricity generators include nuclear, coal, and natural gas.
But, renewable energy sources have reshaped this base-load and peaker plant arrangement. Because wind and solar generating facilities may provide power for free once the panels or turbines are erected. For natural gas-fired plants, gas is one of their main expenses. This adds an uncontrollable bottom layer to the energy mix. One bright, windy day might mean a state has too much power when added to its base-load sources, while one dark, windless day could mean peaker plants have to work hard. Solar and onshore wind power are currently among of the cheapest sources of energy, but since they rely on natural occurrences, they can’t match supply to demand as the nuclear, coal, and natural gas trinity can. Hence, grids are being redesigned to avoid minute-to-minute supply-demand matching. Of course, storage is needed, but electrical storage is difficult. The average American home uses 30 kilowatt-hours of power daily.
Lithium-ion batteries cost $130 per kilowatt-hour, so one day’s storage for one family would cost $3,900 in batteries—not including the infrastructure needed to install them. The average American family spends less than half that in power costs, making grid-wide installation uneconomical. Colorado has four small battery-electric storage systems. The biggest powers Fort Carson, an army facility near Colorado Springs. They charge the 8.5 megawatt battery at night when electricity demand and rates are low, then use it during the day when the base uses the most electricity. After 13 years, the technology should save the army half a million dollars in power expenditures. This strategy makes economic sense for huge complexes that can invest in infrastructure that won’t pay off for more than a decade, but it’s not realistic grid-wide.
Even if battery manufacture may reduce global power demand, the savings are too far in the future for most to consider such storage worthwhile. In the future decades, more individuals will buy huge EV battery packs for very different reasons. Most predictions predict that a third of US automobile sales will be electric by 2030, providing a natural storage solution for the grid. The Rivian R1135 T’s kilowatt-hour battery pack could power the average American household for four and a half days.
EVs may technically return power to the grid. Therefore, EVs might charge at night or when renewables are doing well, then provide part of that power back to the grid during the day while parked and plugged in. Utility companies would pay car owners a little fee. This vehicle-to-grid idea might help move to a greener grid, but its real-world, wide-scale economics have yet to be validated, especially given battery deterioration. Fort Carson’s 8.5-megawatt battery energy storage system is Colorado’s biggest.
This huge battery can power over 10,000 houses in the state. One of the finest sources of power is water, which humanity exploited early on. Hydroelectric power is a win-win. Damming rivers can hurt the environment, yet hydro is green like wind and solar since its carbon footprint is near-zero. It’s also dependable. Hydroelectric dams may respond to demand like natural gas, single-cycle peaker plants by starting and stopping power production in minutes, even though a minimum flow is usually maintained.
Hydroelectric dams turn potential energy into electric energy, even if there is only so much water upstream—especially in Colorado, which is under a 20-year drought. Reverse that procedure. Cabin Creek Generating Station does that.
When power is cheap—usually at night or when wind and solar are at their peak—the plant pumps water to its upper, higher-elevation reservoir. When power is pricey and in demand, like late afternoon, it will discharge that water via its turbines into its lower reservoir. Price arbitrage is smoothing wind and solar power output peaks and troughs. Electricity is useless to that Glenwood Springs, Colorado library until it arrives, regardless of supply and demand. People think power plants are outside every town and city. Early grids worked that way, but not anymore. 42% of Colorado’s power comes from coal, despite sharp decreases in the preceding decade.
Almost half of the state’s electricity comes from six coal power units. Hence, long-distance electricity transport is crucial. Long-distance transmission is difficult because power is lost as heat during transmission. Centralized power generation costs cheaper due to economies of scale. Hence, transmission involves balancing these impacts to reach equilibrium. All electric grid-connected buildings use alternating current electricity. Since transformers can easily convert AC power between higher and lower voltages, Tesla, Westinghouse, and Edison chose this standard over direct current. High voltage reduces transmission losses, making this critical.
Transmission power loss is quartered by doubling voltage. That simple voltage shift improves power delivery. Colorado’s Craig Generating Station is second biggest. Two of the state’s highest-voltage transmission lines go south to Rifle from it. As these lines operate at 345 kilovolts, around 3.2% of the power is lost along the 75 miles or 120 kilometers from Craig to Rifle. Some heavily populated places, which need greater electric transmission capacity, have even higher voltage lines, up to 765 kilovolts—the US’s highest transmission standard. One connects Quebec to New York State, and another connects Illinois to Virginia.
These high-voltage lines can transport six times as much electricity as the 345 kilovolt cable between Craig and Rifle and lose only 0.6% every 100 miles or 160 kilometers. If the infrastructure existed, a 765 kilovolt line could transfer power from New York to LA and 87% of it would still be there at the other end. Hence, high-voltage wires are becoming increasingly frequent. Direct current transmission is even more efficient than high-voltage alternating current transmission. Direct current is more costly to convert between voltages than AC, therefore it must be converted to AC electricity for usage in today’s grid. DC lines lose 0.45% every 100 miles, compared to 0.6% for the highest voltage AC lines. Hence, switching power to DC at its origin and back to AC at its destination can be economically advantageous when transmitting large amounts of electricity across long distances. The Pacific DC Intertie, between northern Oregon and Los Angeles, California, is one of the most notable American applications.
Hydroelectric dams in the temperate northwest provide a lot of inexpensive electricity in summer despite low power demand. The Pacific DC Intertie transmits electricity south to run Los Angeles’ air conditioners in summer. In winter, Los Angeles sends its extra electricity north to power electric heating in the Pacific Northwest since the temperature is mild. This shows why a greener, more efficient grid requires long-distance power transmission infrastructure to balance seasonal tendencies and transfer power from where it can be generated to where it cannot. Nonetheless, the Craig Power Station’s 345 kilovolt cable penetrates this more populous area along Interstate 70 in Colorado. Many surrounding villages require energy, but providing 345 kilovolts to them would be inefficient.
Because voltage increases building expense. A 345 kilovolt substation could cost $10.7 million, while a 230 one $7.6 million. A 230 kilovolt line costs $2.8 million per mile, whereas a 345 kV line costs $4.5 million. Although though transmission losses will be higher, many substations near Rifle convert the power to 230 kilovolts, and then smaller, cheaper lines convey the flow west, south, and east to its ultimate users. Another substation lowers this line to 69 kilovolts 30 miles or 50 kilometers east, and then a smaller line loops back into Glenwood Springs. The electricity is then stepped down again to 12.47 kilovolts before a final transformer transforms it to 120, 240, or 480 volts—the voltages utilized by most American buildings, including Glenwood Springs’ public library.