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Comment by idoubtit | Hacker News Reader

> In the US, it's cheaper to build and operate wind farms than buy fossil fuels.

This is currently HN's title, and the article's subtitle. But the article makes no statement to prove this assertion.

It does not even make sense to me. I guess the author meant that for firms that have high energy needs. But it is stupid to imply that the electricity provided by fossil fuel can always be replaced by wind turbines. If the need is for regular bursts, high volumes on short periods, wind won't be of much use.

Moreover, the article is a digest of a report that is less emphatic. The US Department of Energy expects a slow-down of wind capacity after 2020, once the tax credit will end. For a project that would start now, there would be no tax credit, so it would be hard to reach a competitive price.

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You’re close to the situation at hand. Wind does not match the demand curve, but it’s vastly cheaper than natural gas.

This means wasting a significant percentage of wind generation is still a net savings. Currently curtailment aka excessive wind production is relatively low percentage of generation, but based on current prices it’s cheaper to build more wind just to offset more natural gas use.

You end up needing to pay for the generators either way. So, currently the breakpoint ends up being when 1/2 of all wind power is wasted resulting in 2 x 10$/MWh your at breakeven with fuel costing $20/MW-hr.

However, current natural gas prices are market driven. Reduced demand will lower prices, but that’s still a net win for power companies. In the coming years as new wind power comes online the economic situation will change, but for now massive investments look like a very good deal.

For individual residential generation solar seems cheaper than wind. Is there a cutover between solar and wind?

Yes, wind gets cheaper as you scale up the turbine. The transition is something like 1 MW turbines, but this is very location specific for both wind and solar.

Wind doesn't make a lot of sense when sized to serve a house, or even a neighborhood. It becomes economical hundreds of feet in the air with turbine blades the size of a city block.

vastly cheaper than natural gas?

Natural gas has negative pricing right now due to being stranded in production!

I am currently seeing: 2.20 USD/MMBtu for Aug 16 2019 which is greater than zero. http://www.infomine.com/investment/metal-prices/natural-gas/...

The article translated whatever the price was when they wrote it into 20$/MWh. I assume it’s still reasonably accurate as it was published yesterday and the price has been fairly consistent recently.

Good to use data. What I am referring to are the pre-wellhead prices which can't even be measured because the gas producers will not pay to put it on the pipeline. Ergo the negative pricing.

"negative pricing" sounds like they'll pay me to use it, if only I would just use it. I can see that's not your intent, but I suspect that's the first reading of many.

They literally would pay you to use it, if you would go to the trouble of taking it off their hands. There are legal restrictions on those gas flares now, so they can't just burn all of it like they used to.

Where is this true? https://www.eia.gov/energyexplained/index.php?page=natural_g...

Just because there stranded natural gas exists doesn't mean the market prices are below zero.

> But the article makes no statement to prove this assertion. It does not even make sense to me. I guess the author meant that for firms that have high energy needs...

They do make a statement, I think you might have missed this paragraph:

> That puts wind in an incredibly competitive position. The report uses an estimate of future natural gas prices that show an extremely gradual rise of about $10/MW-hr out to 2050. But natural gas—on its own, without considering the cost of a plant to burn it for electricity—is already over $20/MW-hr. That means wind sited in the center of the US is already cheaper than fueling a natural gas plant, and wind sited elsewhere is roughly equal.

The implication of this claim is that in operation it’d be cheaper to build both a gas plant and a wind farm, to reduce the amount of gas that you burn, rather than just building a gas plant. If that’s correct your discussion of intermittency wouldn’t be relevant.

But the article also states:

> Wind is even cheaper at the moment because of a tax credit given to renewable energy generation. But that credit is in the process of fading out, leading to long term uncertainty in a power market where demand is generally stable or dropping.

Or from the government report itself:

> The magnitude of growth beyond the current PTC cycle remains uncertain, however, given declining tax support, expectations for low natural gas prices, and modest electricity demand growth.

So what is it? Is wind power cheaper or was that a tax subsidy effect?

It’s subsidized even as it’s still cheaper without the current subsidy. The uncertainty in natural gas prices means that this exact situation is unlikely to hold up over time. Reduced demand for natural gas resulting in lower prices, up to a point.

Good example of this is just last week when texas almost had an energy shortage and power skyrocketed to $9/kwh for a few hours. It was due to being super hot and not windy. Texas shut down many coal plants and replaced with wind.

> ..If the need is for regular bursts, high volumes on short periods, wind won't be of much use.

Just on this point, the article talks about curtailment:

At times, strong winds can cause wind farms to produce an excess of power relative to demand, causing a farm's output to be reduced. This process, called curtailment, remained a small factor, with only two percent of the potential generation lost this way. Put differently, if the curtailed electricity had been used, it would have only raised the average capacity factor by 0.7 percentage points.

It sounds like 'short bursts' is really not a problem.

I'm pretty sure curtailment is the exact reverse of what the comment you're replying to is talking about - it happens when there's an excess burst of wind power compared to demand, whereas the question is about wind power filling bursts of demand. Since there's almost no curtailment it seems pretty clear that wind power doesn't currently play a role in filling those; there's just not the excess capacity for it. Of course, curtailment is only low right now because most of the generation is from fossil fuel plants which are shut down in preference to wind. Once that changes curtailment will go up and capacity factor will go down.

You are right, I totally missed that.

However now, in that case actually no renewable source of energy - wind, solar, geo thermal.. (other than perhaps hydro) can fulfill the need of sudden burst of energy - wind is like any other.

A no-nonsense title like "building and operating wind farms is cheaper than building and operating natural gas plants" wouldn't have been clickbait-ish enough.

That’s not the claim they’re making, they’re saying wind is cheaper than just buying the fuel for a pre-existing natural gas plant.

I don't understand how you can compare the cost of a wind farm to fossil fuel. The former provides megawatts, and the latter provides megawatt-hours.

You would have to incorporate assumptions on lifespan, maintenance and/or amortization.

Yes, that’s what they do, it’s called a levelized cost. These costs usually come with a sensitivity analysis of the impact of the different assumptions.

Wind or solar is actually often commissioned using a power purchase agreement for a certain price per kWh, guaranteed over a certain period.

Unless the wind turbines are trapped in some sort of time freezing status field, I would generally assume that they both can be measured in megawatt-hours. Or you can multiply out by 3.6 to get to gigajoules if you want more sensible units to play with.

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