xolar

The term itself isn’t all that strange – my handle is ‘xamble’ and the topic is ‘solar’ : combine them and you get xolar.

Some background:

The bulk of our energy needs is served by non-renewable sources that are the end result of processes that take geologic-scale time to turn solar energy into materials we can burn. Petroleum-based fuels, natural gas and coal. Some of these are cleaner than others but the energy release mechanism involved is burning and that comes with byproducts we would rather do without.

During the last 40 years there’s been a drive to create alternate sources of energy that are cheaper, cleaner and more efficient than the ones we currently have. Nuclear energy was sold using the extreme efficiency idea: I remember the ‘1 pound of Uranium equals hundreds of boxcars of coal’ example from my childhood. In fact the USA’s ‘Atoms for Peace‘ program was born the same year as myself, 1953. Since the energy crunch of the mid 1970s there have been sporadic pushes to replace petroleum – sometimes with more effort than other times.

It would appear that in order to make real progress it takes a lot of money.  And when lots of money is involved the forces that it attracts have different agendas and goals from the rest of us. Hence the slow progress and even slower deployment of alternative approaches.

Among the approaches are those related to using solar radiation directly or indirectly to generate usable forms of heat and electricity.

  • Solar heating systems use the Sun’s heat radiation to heat something that in turn release the heat in a controlled fashion in ways and locations we need.
  • Photovoltaics turn solar photons into electricity.
  • Other ways use the solar energy to do work to drive other mechanisms that generate electricity. This usually involves heating something that in turn does some work to drive a generator of some sort that in turn generates electricity. The most public and visible of these schemes is the wind turbine.

My crack-pot idea starts with an idea that relates to the wind turbines like a distant cousin.

Wind Turbine

Wind Turbine

A wind turbine uses wind energy to turn very large propeller-like blades which are connected to a generator that generates the electricity. They are huge constructions that are quite expensive and because of that they are well planned and sited only in locations that will virtually guarantee continuous wind. If the wind doesn’t blow they don’t work – so they aren’t suitable for locations without a river of air flowing overhead. This virtually ensures they will be planted in large numbers in places where the wind is so they can feed the electrical grid. Large numbers of large machines with expensive transmission lines means a lot of money involved. There’s only so much investment money available and big projects tend to soak up large amounts of it leaving not so much left over for other projects. Projects with less return or more blue-skyness with be ignored and starve for development funding. Because of this the number of serious contenders to the wind turbine industry is very small. But they do exist …

Solar Tower technology takes a different approach: at top of the tower is a thermal-based generator that is heated by acres of robotic mirrors called heliostats. They reflect the sunshine onto the tower top like a magnifying glass focusing it into a spot. The heat at that spot is used to drive the generator and that makes the electricity. A large, expensive system.

Solar Updraft Tower technology has gotten less development but is a hundred year old idea that, in my humble opinion, has more advantages that give it more potential than solar turbine. It works when there is no wind which means it doesn’t have to be located where it can stick its head up into a river of wind. And with recent advances in converting waste heat and mechanical energy into electricity I believe it will become more efficient and desirable.

solar_updraft_tower1a

Links:

Alternative Energy News

So enough of this background – just what is my crackpot xolar idea?

I would like to modify the Solar Updraft Tower (SUT) idea mentioned above. From the animation above you should have a basic understanding on how a conventional SUT actually works.

Idea #1:

What if the Chimney were made of a flexible material instead of bricks or steel?
It only needs to funnel reasonably warm air from ground level to an altitude and if it could flex with the wind then it would not need a large amount of the mass other chimneys need to maintain their stiffness in the face of wind.

What if the chimney was able to be extended or retracted to find the optimum height? A flexible, collapsible tubular funnel.

How would such a construction become extended?

The top end of the tube could be pushed upwards by some mechanism . . . or it could be pulled up by some mechanism.

A Kite and a Balloon both rise through the air exerting an upward force on any tether attached to them.

Let’s imagine for a moment that our expandable funnel is 5 meters wide at its base and 3 meters wide at its upper mouth. And that its length can vary from 3 meters to 50 meters. It sits within a 3 meter high base housing on a 2 meter high hollow base frame.

Now imagine a 10 meter wide hot air balloon is sitting on the top of this base. Where the passenger basket would go we attach the top of the funnel. Within the base we have a hot air blower that feeds into the balloon (through feed tube into the funnel bottom) to do initial inflation. The inflated balloon rises and in turn drags the funnel top end upwards with it. At some point the force of the air flowing up the tube and into the balloon will be enough to hold the balloon aloft and the funnel tube extended. And at that point the hot air blower system could be turned off because the system would be self sustaining.

Just like with a normal hot air balloon the area between the funnel exit and the balloon bottom would be a gap through which the air flow would escape. If the size of this could be changed in a controlled fashion then the exit flow rate could be moderated. By moderating this flow rate we might be able to keep the balloon inflated and the system operating.

In the real world hot air balloons have a requirement to replace their envelopes every couple of hundred hours. This would make the above idea unworkably expensive as the total cost over time would likely exceed the initial one-time cost of a fixed tower. Likely this idea would need new materials or techniques to be considered possible.

Idea #2

Go back to the original SUT concept. What generates power? Turning fans driving generators.

There would be a minimum breeze speed to get the mass of the fan to turn. Some amount of the energy going into the system would be lost due to friction within the system.

What if the fans could be replaced with an alternative way to harvest kinetic energy from the wind in the form of electricity?

The field of kinetic energy harvesting is growing. Alternatives to windmills have appeared that utilize slender cones mounted on poles. As the wind pushed on the cones they cause the structure to tilt and there is a system within the mounting that turns that mechanical deformation into electricity (Ke2E).

This type of mechanical deformation to electrical signal has been a staple of piezo electric technology from its beginnings though it’s really only recently that this idea has been looked at for power generation as well as small signal processing. There is growing research into alternative materials such as man made polymers which could work in similar ways.

I’m thinking that at some point it may be possible to print sheets of plastic that has thousands of small structural features that all perform this Ke2E job. Think of a ma made leaf or frond. With circuit fabrication techniques these could be created with ‘wiring’ built in. So our man made ‘leaf’ could connect with a few others into a ‘twig’. The ‘twig’ connects to a ‘branch’ along with other twigs. The branch connects to the ‘trunk’ of the system and that provides mechanical support and electrical connection.

So imagine a man made inside-out tree with hundreds of branches each with dozes of twigs each with a handful of leaves with each leaf having hundreds (or thousands) of small Ke2E generators.

A system like this might sound much more complicated than the few fans at the base of a tower except this new system might be capable of being scalable down to smaller chimney systems that could work at slower flow rates. Possibly single home sized systems could become feasible with economies of large volume production techniques.

On a home site the chimney need not be free standing or even a ‘chimney’ at all. It just needs to provide an air flow over the mechanically sensitive part of the man made ‘tree’. Like you might get if the roof decking were actually a large hollow flat box just thick enough to house the system an provide an inlet at the bottom and an outlet at the top. Convection would provide the air flow. At least one study of solar PV panel installations laid on roofs has shown that when they are lifted off the roof on stanchion supports the draft that takes place between the panel and the roof actually helps cool the house.

It might be a crackpot idea but it might also be a workable one. I do not possess the knowledge or have access to the technology to make this happen but You might.

If you’ve read this far then I hope you’ve enjoyed it and even if you don’t believe or agree with me I hope you’ve had a laugh.

 

 

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