Folsom Powerhouse State Historic Park facts for kids
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Folsom Powerhouse
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Folsom Powerhouse on the American River in July 2015
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 Location in California
Location in the United States
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| Location | Folsom, California |
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| Built | 1895 |
| Architect | H.T. Knight; Sacramento Electric Power & Light Co |
| NRHP reference No. | 73000426 |
Quick facts for kids Significant dates |
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| Added to NRHP | October 2, 1973 |
| Designated NHL | May 29, 1981 |
Folsom Powerhouse State Historic Park is a special place that keeps alive an old power station from 1895. This station was one of the very first in the United States to make electricity using water power and a new type of electricity called alternating current (AC).
Before the Folsom Powerhouse, most electricity came from direct current (DC) generators. These generators were powered by steam engines and could only send electricity a short distance. It was hard to send water-powered electricity far away because DC power lost too much energy over long lines.
But then, AC power was invented! With AC, special devices called transformers could change the electricity to a very high voltage. This high voltage could travel long distances without losing much power. Near where people needed the electricity, other transformers would change it back to a safer, lower voltage. DC power cannot use transformers to change its voltage.
The Folsom Powerhouse used the rushing water of the American River to spin its turbines. These turbines were connected to new AC generators. It made three-phase, 60-cycle AC electricity, just like we use today! Transformers then boosted this power from 800 volts to 11,000 volts. This high-voltage power traveled 22 miles (35 km) to Sacramento. This was one of the longest electricity lines in the United States at that time.
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How the Folsom Powerhouse Changed Things
In Sacramento, the 11,000-volt AC power was changed back to a lower voltage for homes and businesses. The Folsom Powerhouse showed everyone that water power could be a great source of cheap electricity. Even if the power plant was far from the users, it could still send power efficiently. The Folsom Powerhouse is about 23 miles (37 km) from Sacramento, in the city of Folsom.
History of the Powerhouse
The Folsom Powerhouse worked non-stop for 57 years, until 1952. It closed when the original Folsom Dam was taken down to build a much bigger one. Pacific Gas and Electric, who owned the plant, gave it and most of its equipment to the State of California.
The State of California made the site a California Historical Landmark in 1956. In 1981, it became a U.S. National Historic Landmark. The powerhouse building, made of brick and granite, still looks much like it did in 1895. Inside, you can see the huge generators and the control switchboard. They look as impressive as they did over a hundred years ago! You can learn how the powerhouse worked through old photos, displays, and tours. Some of the original water turbines and generators are still there.
Before AC generators and transformers, power stations had to be very close to where electricity was used. This was because low-voltage DC power lost too much energy over long distances. So, early power plants were small and built right in neighborhoods. For example, the Pearl Street Station in New York City started in 1882. It served only 85 customers within about 2 miles (3 km) of the station.
But AC power changed everything! With transformers, power plants could be hundreds of miles away from users. The high voltage could then be lowered for use. The AC generators and water turbines at Folsom were so big they couldn't travel by train. They had to be shipped 19,000 miles (30,578 km) around Cape Horn by ship!
On July 13, 1895, the Folsom Powerhouse sent its first electricity to Sacramento. It was one of the first places in the U.S. to send water-powered electricity over a long distance. The Folsom plant even started sending AC power before the famous Niagara Falls power plant did in 1897.
How the Powerhouse Generated Electricity
Water Supply
The Folsom Powerhouse got its water from a special dam built across the American River in the 1890s. This dam was 650 feet (198 m) long and 89 feet (27 m) tall. It sent a huge stream of water into a 2.5-mile (4 km) long canal called the East Canal. This canal was 50 feet (15 m) wide and 8 feet (2 m) deep. It carried about 85,000 cubic feet (2,407 cubic meters) of water every minute!
The canal ran next to the river but sloped less steeply. This made the water in the canal about 85 feet (26 m) higher than the river. This height difference, called "hydraulic head," gave the water the power it needed. The dam and canal were finished in 1893. Prison workers from the nearby Folsom State Prison helped build them.
The water from the canal flowed into a "forebay," a pool where dirt and debris were removed. Then, the clean water went into four large pipes called penstocks, each 8 feet (2.4 m) wide. There were also two smaller penstocks. Each penstock had a gate that could be closed to stop the water flow for maintenance. The rushing water in these penstocks powered the large turbines connected to the AC generators.
Turbines
The four large water turbines were made by S. Morgan Smith Works. These were some of the biggest turbines built at that time. The rushing water from the American River spun these four large turbines. They, in turn, powered the four AC generators. Two smaller turbines powered the DC generators.
Governors
The four large turbines were directly connected to the AC generators. Their speed was controlled by adjusting the water flow. A device called a centrifugal governor kept the turbines spinning at a steady 300 rotations per minute (rpm). This steady speed was needed to make a constant 60-cycle current.
Alternators
The four AC generators, also called alternators, were very powerful machines. They were invented by Elihu Thomson and weighed almost 30 tons each! These huge generators were 8.5 feet (2.6 m) tall. They were made by the newly formed General Electric company.
To power the magnets inside the AC generators, a small DC generator was used. There was also a backup DC generator ready to take over if needed. All four AC generators were connected together. This helped keep the electricity frequency steady, especially when more power was needed.
Switch Panel
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Folsom Powerhouse Frequency Indicator
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Folsom Synchroscope
To help customers use electric clocks that needed a steady frequency, a "Frequency Indicator" was added to the control panel. A "Synchroscope" was also added. This helped connect the alternators together and to the main power grid.
Transmission Lines
The AC power made at Folsom (about 4,020 horse power or 3 MW) was changed to 11,000 volts by twelve new transformers. These transformers were invented by William Stanley, Jr.. The power then traveled to Sacramento on twelve bare copper wires. These wires were held up by ceramic insulators on tall cedar poles, about 40 feet (12 m) high.
Having multiple wires allowed for four separate three-phase lines. This meant repairs or maintenance could happen without shutting down the whole system. The poles were placed about 105 feet (32 m) apart. Telephone lines were also run below the power lines.
Once in Sacramento, the high-voltage power was sent close to where it was needed. Then, transformers changed it down to a lower, usable voltage. This is how electricity is still sent and used today! In 1895, electric streetcars were a major user of electricity. DC motors, used in streetcars, could only work a few miles from DC generators. But a "rotary converter" could change AC power into DC power for these streetcars.
Factories also used a lot of power. The AC induction motor, invented in 1888, allowed factories to use AC power directly. This meant they could replace their old steam power plants. AC electricity, with its easy voltage changes using transformers, made it possible to build the huge electrical grids we use every day.
On September 9, 1895, Sacramento celebrated the new power from the powerhouse with a "Grand Electric Carnival." Thousands of light bulbs decorated the state capital building to celebrate California's 45th birthday.
Lower Powerhouse
A second powerhouse was built next to the original one in 1897. It held another 750-kilowatt AC generator. This was to meet the growing demand for electricity in Sacramento. This new generator was connected to its turbine by a 20-foot (6 m) rope belt system.
As more people and businesses started using electricity, the Folsom Powerhouse couldn't keep up. By the early 1900s, bigger hydroelectric plants were built along other rivers in Northern California. The California Gas and Electric Company bought the Folsom Powerhouse by 1902. When this company became the Pacific Gas and Electric Company in 1906, they updated the powerhouse.
See also
- Old Folsom Powerhouse Station A
- National Register of Historic Places
- List of Historic Civil Engineering Landmarks
- List of Historic Mechanical Engineering Landmarks
- List of California state parks
- Revolving armature alternator
Images for kids
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Folsom Powerhouse Frequency Indicator
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Folsom Synchroscope
