The Future of Wind Turbines? No Blades?...

[mistermack]

If it requires a combination of hot sun, and cold water, you would think that a ship would be the ideal thing to make use of it. Use all that torque to turn the propeller.

[Seth]

If it requires a combination of hot sun, and cold water, you would think that a ship would be the ideal thing to make use of it. Use all that torque to turn the propeller.

Probably could use it to turn a small prop, but it's not intended as a mobile source. Cooling water can be recirculated through an underground heat transfer loop using the earth as a heat=sink.

[mistermack]

If it requires a combination of hot sun, and cold water, you would think that a ship would be the ideal thing to make use of it. Use all that torque to turn the propeller.

Probably could use it to turn a small prop, but it's not intended as a mobile source. Cooling water can be recirculated through an underground heat transfer loop using the earth as a heat=sink.

That could be done, but I doubt if it would be very effective. You need a lot of pipework to get heat flowing in any quantity, which costs quite a lot of money.
They do something similar in ground reservoir heat pumps. It's quite a lot of pipework, just for a house. To do it for a high-power electrical generator would take miles and miles of pipework.

[Seth]

If it requires a combination of hot sun, and cold water, you would think that a ship would be the ideal thing to make use of it. Use all that torque to turn the propeller.

Probably could use it to turn a small prop, but it's not intended as a mobile source. Cooling water can be recirculated through an underground heat transfer loop using the earth as a heat=sink.

That could be done, but I doubt if it would be very effective. You need a lot of pipework to get heat flowing in any quantity, which costs quite a lot of money.
They do something similar in ground reservoir heat pumps. It's quite a lot of pipework, just for a house. To do it for a high-power electrical generator would take miles and miles of pipework.

I don't think so, not for a small installation. The temperature differential necessary to boil the fluid is really quite small, which is the point of using a low-boiling point fluid, as I understood it.

[mistermack]

I don't think so, not for a small installation. The temperature differential necessary to boil the fluid is really quite small, which is the point of using a low-boiling point fluid, as I understood it.

In that case, you won't get much work out of it. The available work is directly proportional to the amount of heat that flows.
That's why power stations use lots of hot steam and cold water.

[Seth]

I don't think so, not for a small installation. The temperature differential necessary to boil the fluid is really quite small, which is the point of using a low-boiling point fluid, as I understood it.

In that case, you won't get much work out of it. The available work is directly proportional to the amount of heat that flows.
That's why power stations use lots of hot steam and cold water.

Power stations use live steam because that's what turns the turbine wheel on the generator, which requires high pressure (velocity) to make up for small mass, whereas this system uses mass, lever arm (mechanical advantage) and gravity. The heat input and cooling only need to be enough to transfer the fluid as vapor from the bottom of the wheel to the top and condense it there. So long as the heat drives the vapor across the hub to the top side quickly enough to keep up with the wheel (the wheel does have to be governed so it doesn't "overspeed" itself) it would seem to be sufficient.

[JimC]

It may well work reasonably well, but mm's point was about the amount of useful work you can extract from a system based on a temperature differential; essentially, the amount of useful energy you can extract is proportional to the temperature difference available in your system. There are some circumstances, such as solar pond and ocean thermal technology, where you accept a lower value because of the simplicity of the design.

[Seth]

It may well work reasonably well, but mm's point was about the amount of useful work you can extract from a system based on a temperature differential; essentially, the amount of useful energy you can extract is proportional to the temperature difference available in your system. There are some circumstances, such as solar pond and ocean thermal technology, where you accept a lower value because of the simplicity of the design.

Ah, thanks for clearing that up. The beauty of this design seems to be that it can, quite literally, be built by almost anyone who can follow directions and put a kit together that would provide electrical energy (albeit not huge amounts) in places where power networks don't exist. Because it's "low tech", moves slowly and can be built from relatively primitive materials without needing a lot of advanced technology and the ability to operate even when the wind doesn't blow, would seem to make it a viable alternative for power in remote areas.

[mistermack]

It may well work reasonably well, but mm's point was about the amount of useful work you can extract from a system based on a temperature differential; essentially, the amount of useful energy you can extract is proportional to the temperature difference available in your system. There are some circumstances, such as solar pond and ocean thermal technology, where you accept a lower value because of the simplicity of the design.

That's right, but not the whole story.
Temperature differential is only part of it. You need a large supply of heat, or the temperature rapidly drops as heat flows. And you need a sink that can take away that heat, without warming and stopping the flow. Basically, it's quantity of heat moved, which decides the amount of work can be derived from the system.

It's a bit like hydro generation. The temperature difference is equivalent the pressure difference, or head of the system. In hydro, you could have a thousand foot head, but if the available water flow is tiny, you won't get much work out of it. You just quickly exhaust the supply. Or if the outflow isn't quick enough, the flow will back up, and you lose your head pressure that way.

It's the same with heat. You can have a high temp difference, but if the available heat source is not a lot, you quickly exhaust it, and the flow of heat will dry up.

It would be the same with a ground based heat sink. If you haven't got miles of piping, the ground would get hot, and the flow of heat away would slow, as you lose your temperature difference.
With a river, the flow can take the heat away. Or with big cooling ponds, evaporation and radiation cools it. Or you can use cooling towers, and release the heat to the air.
But the ground would only be suitable for very low-power installations, you couldn't get a fast enough cooling for anything significant.
I suppose you could rig up some kind of cooling tower, but it would need pumps etc and probably use most of the power.