Spark a Conversation with Our Fun Energy Facts Series – Part 5

By Vernon Trollinger, July 22, 2016, Events & Fun

Energy – whether electrical, thermal, or mechanical – can do fantastic things, and sometimes science uncovers phenomena no one even dreamed was possible. Because it’s fun to shock and astound friends and relations with incredible facts, we’re going to investigate some of this unbelievable and really cool information. Our Fun Energy Facts series will be at times hot, cold, weighty, electrifying, and morbid, but we know you’ll get enough of a charge out of it to spark an energetic conversation.

Understanding Energy Storage – Get A Charge of This Old Tech!

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When you hear the word “battery,” you probably think of a Double-A or D-cell battery — something familiar with positive and negative ends that holds an electrical charge. But at its most basic definition, a battery stores energy to be used for work, which could mean turning a motor, lifting a lever, spinning up a generator, and more. Humans have been very adept at using and storing energy for centuries, and because they’re essentially mechanical, many of these old designs have been re-engineered to store electricity.

The thing about all energy storage is that you have to put energy into the storage system so you can use it later. After all, that’s why it’s called storage. The problem is that because of the conservation of energy, little inefficiencies in how the system works eat up more energy you use to charge the system than the amount of energy you get out. The trick, however, lies in figuring out how best to use that stored electricity-potential and using it at the least cost.

So, let’s look into three classic energy storage methods and how they’re being updated in the 21st century.

Pumped Hydroelectric Storage

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Most folks associate hydroelectric power with massive dams holding back lakes and controlling the flow of mighty rivers. But what if you don’t need an hydroelectric dam. What if you just need a few megawatts of extra power during the day to meet high demand surge?

Pumped hydroelectric storage makes electricity by letting water drain from an up hill reservoir, flow through turbines that generate electricity, and then collects in a lower reservoir. During the night, when electricity prices are lowest, the water is pumped from the lower reservoir to the upper reservoir — sometimes using the same turbine-generator assemblies that work as pumps when run in reverse.

Sound bleeding edge new? Not at all. The first pumped storage installation in the US was the Rocky River plant. Built in 1929 near New Milford, CT, it pumped water from the Housatonic River to the storage reservoir 230 feet above. In the US, there are 40 pumped storage plants producing more than 22 gigawatts (GW) of storage capacity.

And yes— they use more energy pumping water back up to the top. In 2011, pumped storage produced 23,000 gWh of electricity while eating up 29,000 gWh in pumping to reload its reservoirs. However, by generating power when prices are high and then using electricity to re-load the reservoirs when prices are low, pumped storage can be profitable.

Rail Energy Storage

Spark a Conversation with Fun Energy Facts Series - Part 5 | Bounce Energy Blog

Gravity railroads were a (sometimes dangerous) fixture in the Gilded Age of the late 19th century. Steam engines would pull cars to the top of a hill or mountain and then let the train roll back to the bottom on its own, guided by highly skilled brakemen.

Now, the thing about Direct Current (DC) electric motors is that, when you mechanically turn them, they produce electricity. And when you put electric motors on a locomotive pulling a train loaded with hundreds of tons of rock and let it roll downhill, those motors will produce a lot of electricity. Enough, in fact, that you could put all that energy back on the grid.

That’s the plan of Advanced Rail Energy Storage (ARES). The Nevada Bureau of Land Management has approved ARES to begin building its own energy-storage gravity railroad. Very similar to pumped hydroelectric storage and its breezy cousin Compressed Air Energy Storage (CAES), an automated electric locomotive will push a heavy rock-loaded train up a hill using excess off-peak energy. During peak usage, the brakes are released and the train rolls down hill — but it uses their electric motors as generators.

Efficiencies are estimated at about 80%, but rail energy storage is far more cheaper and scalable compare to pumped hydro. ARES estimates it can scale projects from 50 MW to 1 GW. There’s also the increased potential of locating such systems nearer to urban centers, especially in hilly regions with lots of abandoned rail line.

Flywheels

Spark a Conversation with Fun Energy Facts Series - Part 5 | Bounce Energy Blog

If you’ve ever seen industrial machinery from the Industrial Revolution, one of the big fixtures was the flywheel. An example is the big one weighing several tons on display at at the Tredegar Ironworks National Park in Richmond, VA. It measures 12 feet across and was used to help run the rolling mill.

Flywheels are heavy metal wheels that store energy by converting it into rotational energy. Once they are in motion, they will stay in motion, and they keep all that stored energy. James Watt first incorporated the use of a flywheel into his first steam engines in order to maintain momentum between piston strokes. As time went on, larger and larger flywheels were built, with their main purpose of maintaining rotational momentum and equalize the rotational speed.

Flywheels are traditionally made of bronze or steel set to spin using conventional bearings. Speed was limited to a few thousand rotations per minute (RPM’s). Any faster could spell disaster because, unless the flywheels were manufactured with exact precision, their spin would be unbalanced with calamitous results. It was a common occurrence for large-scale flywheels to fly apart or explode if driven too fast. In 1905, a 25 foot wide flywheel at Tredegar exploded, killing a man, injuring two others, and demolishing the 100-foot-long building that housed it.

Modern flywheels are engineered to perform with 90% efficiency — meaning only 10% of the energy is lost due to spinning them up to speed. They are made of carbon fiber, housed in vacuums to reduce air-drag, and use magnetic bearings. Low friction with fast/free rotation (16,000+ RPM’s) and fitted with electromagnets, they can be used as backup power systems to generate electricity when the power to the motor that spins them is cut. In terms of grid-scale generation, flywheels are a perfect component for intermittent power sources such as wind and solar because spinning flywheels can help smooth out voltage spikes and stabilize frequencies to keep the electricity properly conditioned for used on the grid.

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