Energy storage from submerged buoyant devices

The other day I read an article about how a Canadian utility was using balloons filled with compressed air to store energy.  Air in the balloons is pressurised when there is an abundance of electricity, and this air is released when there’s a shortage.  It’s similar and yet opposite to a pumped hydro system.  You can read about this here.  This got me thinking as you’d need balloons that can inflate and deflate and withstand various levels of pressure.  You’d need pipes that transmit the air to and from the balloons and you’d need pumps and turbines to fill the balloons and then harness the energy in compressed air.

What if the balloons stayed constantly buoyant but what changed was their level under water.  What this would mean was  that you’d need an anchor, a buoyant device, and something which could act as a winch and a dynamo.  Would this be easier?

Buoyancy_device

Clearly you’d need the equivalent of ‘head’ with pumped storage, so the depth of the water would be adequate to give the system a good amount of kinetic energy.  No point setting this up in one meter of water.  You’d also need to ensure that there’s nothing around the surface of the water that it would interact with; if you’re driving a boat with an outboard you wouldn’t want to go around popping people’s balloons.

The material used for the chain or rope would need to be able to withstand moving backwards and forwards, without deteriorating too quickly.

I’m naturally not the first to think about this.  Someone filed a patent in America.  Hopefully they’ve done something about it, because there’s nothing more useless than someone blocking technology development with a patent that they’re just sitting on.  Especially if it’s not rocket science.

Someone has also picked this up at the University of Sharjah, UAE, with a paper published in 2015 and that the efficiency of the system is just under 40% (not great, but also not terrible if it’s relatively cheap and can be scaled).  They say the compressed air system they tested (not under water) had a much higher efficiency of over 84%.

The thinking is that it could be particularly useful with offshore wind installations, as it could be set up right next to the turbines, storing energy when there’s an abundance of wind, and releasing energy when there’s an abundance of demand.

It’s an interesting concept, and I’d be keen to hear if there are any applications of it or if anyone’s seen any more studies on it.

As a last note, there are other buoyant technology that are being looked into, some of which are being researched by the University of Innsbruck.  Their research would make use of the empty space in offshore platform or wind turbine pillars/support structures.  In these applications water would be pumped in and out of the structures.  Interesting all around.

Energy storage really the talk of the RE town at the moment

Following on from my post on electricity storage from yesterday, the Renewable Energy World site included three articles on storage in their mailer this morning.

Sitting at the Tip of the Iceberg: The Huge Potential of Energy Storage (found here), where they estimate that “the U.S. energy storage market will grow to 1.7 gigawatts in 2017 and should hit 2.5 GW by 2020.”  This is largely driven by targets set in California where it has been mandated that “the state’s utilities procure 1.325 GW of storage by 2020.”

In Hawaii’s Solar Conundrum: Can Energy Storage Save the Day? they describe how Hawaii is alsolooking into storage quite actively (article found here), where they have “opened bidding for one of the largest energy storage projects in the country: a 60- to 200-megawatt storage project to help manage solar power within the Oahu island grid by 2017.”

And finally, Energy Storage: A Different View from Germany (found here) talks on how Germany is looking into “three main categories: power to heat, power to gas (specifically hydrogen) and power to power, which can utilize a range of storage technologies, including electrochemical (batteries), mechanical or thermal.”

It’s no surprise that all three of these articles focus on areas where there is a high penetration of solar technologies, and there is likely to be even more interest in solar going forward.  
It’s good news for South Africa that R&D in the States and in Germany is a priority at the moment.  Innovations and breakthroughs in this field can have massive implications for a country with solar irradiance like ours, where baseload is considered to be so important.

A quick intro to electricity storage technologies by Arup

With renewables becoming more prominent in many countries’ energy pictures, the issue of intermittency is become more and more relevant. As Steve Saunders from Arup points out in his Thoughts article “*Storing electricity evens out the intermittency in supply that comes with technologies such as wind or solar. Without it, a grid is limited to around 18% renewables – a point Germany has already reached and the UK is close to*.”

I found this guide, put together by Arup, quite interesting and handy. It
summarises the key characteristics of some storage technologies, and the
full doc can be downloaded here

The following technologies are explained at a very high level, with info on

the advantages, disadvantages and possible applications. A nice intro into
energy storage.

– Sodium Sulphur (NaS) Batteries
– Flow Batteries
– Lead Acid Batteries
– Lithium ion (Li-ion) Batteries
– Sodium Nickel Chloride Batteries
– Liquid Air Energy Storage
– Compressed Air Energy Storage
– Pumped Hydro Energy Storage
– Pumped Heat Electricity Storage
– Flywheels
– Hydrogen
– Superconducting Magnet Energy Storage
– Super Capacitors

Velkess flywheel technology promises cleaner, more efficient energy storage

Found in Gizmag.  Sorry for copying pretty much the whole article – had me very interested.

Of the technologies currently in play, batteries are still expensive and limited in capacity, compressed air energy storage requires very specific spatial geological formations, thermal storage – often used in concentrated solar power (CSP) facilities – is also expensive and difficult to scale, and pumped storage hydroelectricity, while relatively inexpensive and efficient (70–85 percent), also requires specific geographical locations.

Perhaps the most straightforward storage method of them all, energy storage flywheels have been in use for over a century. A flywheel is usually a heavy shaft-mounted rotating disc that absorbs and stores twisting or spinning motion and then releases it as rotational kinetic energy.

Armed with the pioneering research of John Vance, a retired professor at Texas A&M University (TAMU), Gray has developed a novel approach to flywheel design with a patent pending flywheel system called Velkess – short for VEry Large Kinetic Energy Storage System. According to Gray, Velkess is a radical improvement on existing flywheel technologies and is dramatically less expensive than even the most economical energy storage technologies available today.

The existing prototype flywheel floats on a high efficiency magnetic bearing assembly, can make or absorb 2 kW of power, and can store 0.5 kWh of energy. Gray needs to scale that storage capacity up 30 times to 15 kWh. That requires replacing the 25 lb flywheel rotor seen in the video with a 750 lb version.

“Our challenge is with the magnetic assembly,” says Gray. “The magnets to float 25 lbs are easy to get on the internet and easy to work with by hand. Magnets strong enough to float 750 lbs, are a different story. They need to be custom made and are too powerful to safely work by hand.”