Green power: pressurising air underwater

I'm all for green power but the problem is with fluctuating supply, as with wind or solar. Supply rarely marches demand, so being able to cheaply and simply store power is vital. Batteries has been the usual approach when studying the problem, though pumping water uphill when there is little demand (and running it out through turbines) has its fans as well. The UK has been using this concept for decades.

Seamus Garvey, Professor of Dynamics at the University of Nottingham, has come up with a solution to the problem: when wind power isn't needed, it's stored in canvas bags under pressure in the sea.

I came across the idea in the article "Bottling the wind" by Abigail Beall in the 1 November New Scientist issue. She explains that the mechanical engineer was driving on a motorway when he thought of the idea of storing unwanted power underwater. When the power was needed, it would become available again, as simply venting it would drive a generator.

He tried to prove it was a bad idea and then realised it was a very good idea. If you want to store compressed air you need a lot of pressure, and there is no lack of that deep in the sea. Garvey was quoted as saying "It's important to take advantage of the stuff around you".

What about the patents ? As long ago as 2007 a World patent application in his name was published, with the University of Nottingham as the applicant, titled Power generation. Here are two patent drawings from the (American) patent specification.

The corresponding European patent application is still, all these years on, undergoing examination and has not therefore been granted protection. The European Register entry EP1971773 lists the various actions and by clicking on All Documents, at top left of that page, the correspondence with the European Patent Office can be read. Maybe the 10 patent documents cited against the World application were causing a problem. Meanwhile, in 2011 US8030793 was published.

At the time of writing, 16 patents since 2007 have had the Garvey specification cited against them, and are listed here. Clearly, there is interest in the topic.

There are a lot of videos about the concept or Garvey available. Garvey is now working on a commercial system with Canadian wind power company Hydro-Star Energy, LLC.

Solar energy for power, heat and water: Airlight's Sunflower

The Sunflower is a versatile solar energy "harvester" by Swiss company Airlight Energy. It provides power, heat and water, and can be transported in a shipping container.

I love ingenious solutions to environmental problems, and this is one of the most interesting ones I've seen in years. I came across it in a New Scientist article by Paul Marks published in the 4 October 2014 issue, and available online as Sunflower solar harvester provides power and water. Below is what it looks like.

As it fits inside a single container, transport is relatively easy to any location. The dish is ten metres high and tracks the sun. Besides clean water and electricity, it can even provide refrigeration if a heat pump is used.

The article explains that the technology for the water-cooled solar panel was developed by Bruno Michels and colleagues at IBM, and Airlight have licensed the patents. I have noticed several possibly relevant World applications by Michels at the Swiss base of IBM, listed here.

Photovoltaic module cooling devices is obviously relevant, and is illustrated below.

The article explains that each panel holds 25 photovoltaic chips cooled by water flowing in microchannels. The cooling effect means that the panels operate at their optimal temperature, so a quarter of the panels are used to produce the same power as conventional panels.

The heated water can then drive a low-temperature desalinator in coastal areas, going through three cycles, producing 2500 litres of fresh water daily. Away from the coast a water purifier can be fitted. A relevant IBM patent document, Desalination system and method for desalination, is illustrated below.

The dish itself consists of numerous 1-metre mirrors, which direct the sunlight onto six panels which produce the panel. Normally the mirrors would be heavy, polished glass, but instead they are made of metallised foil, like chocolate bar wrappers.

Tests on an 18-mirror prototype showed a 30% efficency rate and a 50% heat efficiency rate. A 36-mirror version should be able to provide 12 KW of electricity and 20 KW of heat from 10 hours of sunlight.

I have found 18 World patent documents by Airlight which are on solar energy.

Tests are to be carried out in seven sites, probably in Morocco and India, with sales beginning in 2017. As might be expected, the entire design is meant to be low maintenance.