Flywheel energy storage

Beacon Powerhas updated the old idea of short-term energy storage via flywheels:-

 

Flywheel energy storage works by accelerating a cylindrical assembly called a rotor (flywheel) to a very high speed and maintaining the energy in the system as rotational energy. The energy is converted back by slowing down the flywheel. The flywheel system itself is a kinetic, or mechanical battery, spinning at very high speeds to store energy that is instantly available when needed.

 

The primary use at the moment appears to be frequency regulation for electricity generation, a well-known problem with wind and solar, especially solar. As Beacon Power says:-

 

To ensure a functional and reliable grid, the Independent System Operators (ISOs) that operate the various regional grids must maintain their electric frequency very close to 60 hertz (Hz), or cycles per second (50 Hz in Europe and elsewhere). When the supply of electricity exactly matches the demand (or "load"), grid frequency is held at a stable level. Grid operators, therefore, seek to continuously balance electricity supply with load to maintain the proper frequency. They do this by directing about one percent of total generation capacity to increase or decrease its power output in response to frequency deviations.

 

Not all generators can operate reliably in such a variable way. Changing power output causes greater wear and tear on equipment, and fossil generators that perform frequency regulation incur higher operating costs due to increased fuel consumption and maintenance costs. They also suffer a significant loss in "heat rate" efficiency and produce greater quantities of CO2 and other unwanted emissions when throttling up and down to perform frequency regulation services (my emphasis).

 

Flywheel storage technology must add substantial frequency regulation costs to wind and solar. In the case of wind in the UK, these are costs which its proponents have so far succeeded in spreading around elsewhere.

 

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Energy efficiency: method vs. objective

Alzetta's petrol-driven mechanical horse (Pic: http://cyberneticzoo.com/?p=2595)

Is our thinking radical enough? Imagine if all we had done in the twentieth century was to replace living horses with mechanical ones to pull carts and waggons.

Similarly, making internal combustion engines more efficient and cleaner is good, but this still focuses on cars as a method rather than re-examines what they're for. ATOC reckons rail is better:

"... on average, passenger rail currently emits approximately half the carbon dioxide per passenger kilometre of cars and around a quarter that of domestic air... This analysis is based on average figures. Quite clearly, in any specific example, the occupancy of the vehicle is key. A fully-loaded car will perform well on a CO2 per passenger km basis compared to the most efficient train with very few people in it. Similarly the averages quoted here cover a range of traffic conditions and may well differ from those of individual operators running specific services. Nonetheless these average figures clarify the starting position. Further work is needed to consider the effect of practical policy options open to us to reduce emissions from transport."

Shame about Beeching, then; and about the way that rail travel has become so expensive on certain routes. Privatisation may have helped certain entrepreneurs and (indirectly) some politicians, but there was nothing much wrong with the old transport system in Birmingham in 1975, and the lower level of car ownership then. Now, some of my young colleagues prefer to run a car instead of building a pension and saving up to buy a house - this DM article says that lower earners can be paying 27% of their disposable income in this way.

On the other hand, there is a welcome new realism about "green transport" in the air. This week there will be an EU vote in Strasbourg on revising targets for the contribution of biofuels to energy production, as London MEP Mary Honeyball explains. This is, it seems in response to growing awareness of the impact of corn ethanol production on food prices; plus the relative expensiveness of alternative fuels. The EC Commissioner for Energy Günther Oettinger also admits that electric vehicles will contribute less to the solution than previously expected (see this video at 1:20 in).

Rather than design better mechanical horses, it would help more if we and our stuff were in the right places to start with. To quote Douglas Adams, one of the finest philosophers of the twentieth century:

"Bypasses are devices that allow some people to dash from point A to point B very fast while other people dash from point B to point A very fast. People living at point C, being a point directly in between, are often given to wonder what's so great about point A that so many people from point B are so keen to get there, and what's so great about point B that so many people from point A are so keen to get there. They often wish that people would just once and for all work out where the hell they wanted to be."

Many of our current solutions are a sort of Marie Antoinette washed-sheep playing with a fantasy version of reality; alternative technologies can be cute and clean without really being green.

All original material is copyright of its author. Fair use permitted. Contact via comment. Unless indicated otherwise, all internet links accessed at time of writing.

Nothing here should be taken as personal advice, financial or otherwise. No liability is accepted for third-party content, whether incorporated in or linked to this blog; or for unintentional error and inaccuracy. The blog author may have, or intend to change, a personal position in any stock or other kind of investment mentioned.

Salt power

Where river meets sea we have an opportunity to extract not just tidal energy, but energy derived from the difference between salt water and fresh. Maybe if energy policies were rational we wouldn’t have such opportunities, but we are where we are.

Pressure Retarded Osmosis

With pressure retarded osmosis, or PRO, the idea is to take advantage of the osmotic pressure created when river water and sea water are separated by a semi-permeable membrane.

Under these conditions, water molecules from the river pass through the membrane into the sea water, creating a pressure on the sea water side of the membrane which may be used to drive turbines and generate electricity.

A pilot plant in Norway has been generating a few kilowatts since 2009. As with so many sustainable energy technologies, the problem is one of energy density. There simply isn’t much energy to be extracted from each square metre of membrane.

Huge areas of membrane, in the order of square kilometres may be required to scale up the technology, but these membranes are also prone to fouling, so the technical issues are formidable.

Reverse Electrodialysis

A less developed but simpler and perhaps more interesting way to extract energy from seawater and river water is Reverse Electrodialysis or RED.

In the RED approach, the osmotic energy of mixing fresh and salt water is captured by directing the solution through an alternating series of positively and negatively charged exchange membranes. The resulting chemical potential difference creates a voltage over each membrane and leads to the production of direct electric energy.

As with PRO, there are many technical hurdles and much research to be done, but a Dutch company called REDstack B V began work on a pilot plant in July. Both technologies are clean, highly modular and relatively well understood.

Could the Severn estuary be used to generate both tidal power and power from a technology such as PRO or RED?

We certainly have the ingenuity - pity about the politics.

All original material is copyright of its author. Fair use permitted. Contact via comment. Nothing here should be taken as personal advice, financial or otherwise. No liability is accepted for third-party content, whether incorporated in or linked to this blog; or for unintentional error and inaccuracy. The blog author may have, or intend to change, a personal position in any stock or other kind of investment mentioned.