Pumped Hydroelectricity- The Original Form of Energy Storage
It was a beautiful Sunday.
I was sitting at the lake, enjoying a book and a pretty view. I was supposed to be the girl fascinated by power plants and yet we were sitting on one and I preferred to hop in it, and splash around in the lake, rather than go see the behind-the-scenes look of how it works. I am only human.
I finally agreed to let my uncle take me to see the hydroelectricity plant.
When I got there I was so glad I had taken the short drive to the lower ground to see the infrastructure- the power plant, pipe, and transmission station.
The body of water, or the energy source in this case, Candlewood Lake, is a manmade lake where people boat and fish. The lake sits on higher ground than the generation station and therefore has embodied energy, which is released when a dam or valve is opened and the water flows through the pipe into the power plant. The momentum of the lake water flowing down over the hill (ie gravity) spins a turbines and creates electricity. It is this ability to keep the water in place, and release it downward when desired, that makes it a form of energy storage. In fact, it is the first hydroelectric pumped storage project in the United States, older than the Hoover Dam, which does not include a pumped storage component, but is instead considered conventional hydroelectricity. Candlewood Lake & Rocky River Power Plant were created in 1926 as a public works project.
Creating the lake and the hydropower project required the relocation of thirty five families and six cemeteries. Workers were paid $1 per body to relocate the cemeteries (remember it was 1926!). Today Candlewood Lake is a popular vacation spot and recreation area for northeasterners and local residents. People swim, waterski, boat and fish in the lake. It is now the largest lake in Connecticut, with a surface area of 5,500 acres, and 60 miles of shoreline.
For me, it’s easier to conceptualize pumped hydroelectricity when I see it. I saw that the generation station was on land below the lake but above the river. I got out of the car, looked through the window into the generation station to see a couple large blue machines, which were essentially indiscernible, but looked like they could be the generators. I then crossed the street to get an up-close look at the pipe that brought the water up and down, a key part of the hydroelectric process. I put my iPhone on it and snapped a photo to show how large it was.
I climbed on it, straddled it, and walked all around it. I took some pictures from all angles, and tried to capture the lake on the other side.
We then headed to a point where we could see the river, which sat below the power station.
After used by the power plant, water is discharged into the Housatonic River below the plant at a rate of 15,500 gallons per second, or equivalent to filling 300 bathtubs per second.
When the grid is not strained, and electricity is cheap (typically at night), the hydroelectric power plant uses electricity to pump water back up from the Housatonic River through the large pipe, and into the manmade Candlewood Lake on the other side. Water is pumped at a rate up to 3,700 gallons per second.
Pumped hydroelectric storage is a relatively inexpensive and a well established means of energy storage. On a large scale and in certain places it can be devastating to the landscape, and to communities that are displaced by the creation of the lake or live downstream of a dam.
Pumped hydroelectricity is a form of energy storage that does not require batteries, or any kind of high tech storage equipment that we think of today. The draw of the plant pulling electricity to pump water back up to the lake is a way of creating demand for power and helping to even out the grid, just like a battery would demand or draw power when there was excess generation capacity. Often times at night power plants aren't working to their full capacity, for example, because people are sleeping and not demanding power. On the whole, there is a large stock of power plants, and many are not used at night. By drawing electricity and using it to move water upward, the hydroelectric system is providing capacity to create electricity later when needed. When electricity is needed and the power grid is strained, operators can utilize the lake as another power source, and release the water- letting it flow back through the generation station, creating electricity, and discharging the water back into the lake until it is pumped up again. And thus is the flow of pumped storage hydroelectricity. Bet you didn't think of that on your annual lake trip! Next time you're sitting a beautiful lake, ask the question-is this manmade? Is it powering my home? Was a town once here? You may be surprised by what you find.
Plant: Rocky River Generation Station & Pumped Storage
Power Source: Candlewood Lake
Power Type: Hydroelectric Pumped Storage
Rated Capacity: 30 MW
Pipe length: 225 feet
Lake capacity: 46 billion gallons of water, or about 1 billion bath tubs worth.
Pipe materials: Steel & wood
Book, Candlewood Lake (Images of America). Buy it here. Proceeds support Electric America.