Pipelines, energy and natural resources

[suffolkowner]

i took it to be capacity efficiency

 

[ytz]

65% efficiency is impossible.

The Betz limit is around 60% for turbine energy capture of wind going past it. After you calculate in other efficiency losses (turbine conversion to electricity, resistances both mechanical and electrical) the best efficiency you're every going to get is 80% of that 60%, (so 50%).

That's not a bad conversion rate.

You're right on Betz law. Gawd. I haven't read my textbook in a decade. Correct.

Either way it most certainly wasn't 25-30% of rated capacity for offshore though. Quick Google says UK is currently at 44% offshore. I think you get closer to the 50-60% of rated capacity with size.

 

[suffolkowner]

My mistake. I haven't read my textbook in a decade. Correct. But it most certainly wasn't 25-30% for offshore though. Quick Google says UK is currently at 44% offshore. I think you get closer to the 50-60% range with size.

50 of 60 is 30 though

 

[Underway]

50 of 60 is 30 though

Yes, but 80% of of 60% is 48% (~50%).

We are hyper simplifying things though and really just confounding the maximum energy you can pull from the wind with the turbines output.

Rated capacity on a wind turbine is calculated by the turbines engineered capacity. Turbines when installed are designed to maximize the available wind energy and run at their highest capacity as much as possible. This means they have gearing in them to stop them from "running away" if the wind is higher.

Then you figure out how many hours a turbine is actually producing at its rated capacity (maximum). You divide those by each other x 365 days and you get.... the actual capacity. 44% means that the wind blew to only 44% of the turbines maximum capacity (full out turbine every day all day).

The Betz law only really applies during design, so that you can properly size/engineer the turbine to match the wind where you're going to locate the wind turbine. You're trying to get to the point in the cost curve where you minimize the turbine cost and maximize the power produced. 44% might be the sweet spot where any larger the turbine gets to expensive and any smaller you're leaving power (aka money) on the table.

 

[ytz]

Betz's Law tells you how much of the wind can be converted into mechanical energy. It's essentially drives the density limit of turbine placement. That's become a less relevant concern with offshore wind where there tends to be a lot more room.

Mostly though in conventional discourse, nobody is talking about the theoretical physical limit of a turbine. They are generally concerned with how much of the rated capacity is actually being delivered. And if you look up the UK that's something like 44% for offshore. And getting higher as turbines size up. And now new designs like the multi turbine mounts.

Going back a bit to the original point here. It's to use maximum local advantage. Wasting a wind resource is no different than passing up on oil reserves.

 

[ytz]

One of the big reasons I took an interest in studying cleantech is to understand the geopolitics and energy security implications of stories like this:

Pakistan has had a long history of IMF bailouts tied to energy prices going up. The Chinese exports of solar PVs could break that cycle. It also means reduced influence of the West over Pakistan. In yet another way.

 

[Kirkhill]

Virginia class S9G 210 MWt

33% electrical efficiency comparable to Darlington

70 MWe
140 MWt

If I only want electricity from wind then I need 14 offshore 10 MW turbines operating at 50% efficiency, a bunch of concrete blocks and steel pylons and a couple of boats, a helicopter and a team of daredevils. On shore I can get away without the boats but now I need 42 5 MW turbines operating at 33% efficiency. I also need miles of wire, lots of pylons to support it and a battery farm resulting in a very large hole in the ground for the lithium.

If I want heat as well then we can multiply those numbers by three. 42 offshore turbines and 126 onshore. And a lot of land access rights.

Or we can do the SMR thing.

 

[ytz]

f I only want electricity from wind then I need 14 offshore 10 MW turbines operating at 50% efficiency, a bunch of concrete blocks and steel pylons and a couple of boats, a helicopter and a team of daredevils. On shore I can get away without the boats but now I need 42 5 MW turbines operating at 33% efficiency. I also need miles of wire, lots of pylons to support it and a battery farm resulting in a very large hole in the ground for the lithium.

If I want heat as well then we can multiply those numbers by three. 42 offshore turbines and 126 onshore. And a lot of land access rights.

Or we can do the SMR thing.

Capex is not the only problem. Do the same comparison again with opex. What's the marginal cost per Watt? Heck, what's the cost per watt on the capex?

Sure. If you're in SK and can't get offshore wind easily, nuclear makes sense (I am not even sure SMRs are competitive with conventional reactors yet). But if you're in the Maritimes, why would you pay nuclear money when lots of offshore wind and a few gas peakers would give you the lowest cost power? No one size fits all. That's a hard concept for a lot of people to grasp.