Is Wind Energy a Chimera?
Help - I've run the numbers and it doesn't make sense to me
I want to start by saying I am not an expert on energy generation. I’ve recently put in a lot of time learning about the grid (electricity generation and distribution) but that’s nothing compared to the people that make a living at this. So I might be very wrong on the below.
So as I learned that the backup for wind tends to be a single-cycle gas plant while base load gas plants are combined-cycle, I immediately thought that there is a wind uptime, where the combined-cycle gas plant running 24/7 is superior to wind with a backup. At 1% wind 99% gas that single-cycle is inferior.
And the nerd in me (Physics major, programmer) likes how the combined-cycle makes double use of the generated heat. That’s clever and is a beautiful solution. Which got me wondering, how often do the windmills need to be in operation to have a lower footprint…
So here we go…
The Requirement
Build an energy generator that will provide 900 MW of base load power 24/7.
The Contenders
Wind turbines + open-cycle gas backup
Combined-cycle gas plant
Building Costs
For our wind farm, we're looking at about $1,391 per kW. With 900 MW capacity, that's roughly $1.25 billion for the wind turbines. Now, let's add a 900 MW single-cycle gas plant at approximately $713 per kW. That's another $641.7 million. Total: $1.89 billion.
A 900 MW combined-cycle plant comes in at about $950 per kW. Total: $855 million.
So the combined-cycle plant is 1B cheaper.
Construction’s Environmental Cost
Wind turbines have a carbon footprint of about 11g CO2/kWh over their lifetime. For a 900 MW capacity, that's roughly 86,724 tonnes of CO2 for construction and manufacturing.
The gas plants are a push. So Wind generates an additional 87 kilo tonnes of CO2 (one time).
Annual Maintenance Costs
Keeping these power plants running smoothly also comes with a price tag. Wind turbines cost about $42,000 - $48,000 per year per turbine to maintain. Assuming 2 MW turbines, we'd need 450 of them, totaling $20 million annually. The gas plant would add another $7 million per year. So a total of $27 million.
The combined-cycle gas plant is a bit higher than the single-cycle at $11 million.
Lifetime
Wind turbines last about 30 years while gas plants are 30 – 40. Calling this even as who knows what we’ll be using in 30 years. If fusion actually happens then all of this becomes obsolete.
Producing Power
Now here’s where it gets interesting. Let's get down to business and compare these two options in three different scenarios, where the wind turbines are either running at full speed or completely off. We'll assume the wind generators are operational for 30%, 50%, and 60% of the time, with the gas plant filling in the gaps.
Let's assume a gas price of $2.90 per MMBtu (million British thermal units) based on 2025 projections.
Wind + Gas Backup
30% wind operation:
Gas expense: $131.4 million/year
CO2 emissions: 3.7 million tons/year
50% wind operation:
Gas expense: $93.9 million/year
CO2 emissions: 2.7 million tons/year
60% wind operation:
Gas expense: $75.1 million/year
CO2 emissions: 2.1 million tons/year
Combined-Cycle Gas Plant
Gas expense: $140.8 million/year
CO2 emissions: 2.7 million tons/year
So Which is Better?
The Tipping Point
For the wind + gas backup option to produce less CO2 than the combined-cycle plant, the wind turbines need to be operational about 50% of the time. At this point, both alternatives produce roughly the same amount of CO2 emissions annually.
But it’s not just the CO2 emissions.
You can build 2 combined-cycle plants for the cost of one Wind+Gas setup. Or you can build one combined-cycle plant and then use the saved $1B fix up drafty buildings with insulation, etc. That’s gigantic.
There’s a larger environmental hit manufacturing and erecting the wind generators. It’s a rounding error vs. the CO2 hit over 20 – 30 years, but it is extra.
It’s an extra 16M a year in maintenance costs. So 320M over 20 years. Again not major.
Gas expense is cheaper for Wind until it gets down to about 35%, then the gas + maintenance is equal. When the Wind drops below 35% the combined-cycle is cheaper.
This comparison will change significantly year by year as gas prices change a lot.
That extra construction cost is gigantic. I’m comfortable saying you don’t want wind if it’s only in use 51% of the time. The EPA says it’s worth $51.00 to remove a ton of CO2. If we take that additional billion dollars in construction cost, divide it by 20 years (ignoring interest on money spent now vs. yearly) to get $50M/year, then at $50.00/ton (make the math easier) the Wind generators need to save 1 million tons of CO2 over the combined-cycle gas plant. That requires the wind generators be working at full capacity 70% of the time.
It's valid to make an argument that removing CO2 is so important that it shouldn’t be priced at $50.00/ton. But the alternative of using that money to weatherize buildings, replace old cars, etc. there is a number over 50% that makes sense even if the sole focus is less CO2.
I think 60% is a good starting point. So we now have a number. If the wind generators are running at the equivalent of full capacity 60% of the time or more – it’s a win. At 70% or more it’s an unequivocal win.
Wind Generator Capacity Factor
The percentage of time that wind generators produce electricity can be understood through the concept of capacity factor. This factor represents the actual output of a wind turbine as a percentage of its maximum possible output over a specific period, typically a year.
Key Insights on Wind Generator Output
Capacity Factor Range: The capacity factor for wind turbines generally varies between 15% and 35% under typical conditions. Some modern turbines, especially those in optimal locations, can achieve capacity factors closer to 40% or even higher.
Operational Availability: Wind turbines can be operational (available to generate electricity) about 90% of the time. However, this does not mean they are generating electricity at full capacity during that time. The actual generation depends on wind conditions.
Average Performance: According to various reports, the average capacity factor for U.S. wind projects has been around 35%, with some newer models achieving up to 60% in ideal conditions. This means that while turbines may be available for 90% of the time, their actual generation will typically reflect these lower capacity factors due to variable wind speeds.
To summarize, while wind turbines can be operational for a significant portion of time, their actual electricity production varies widely based on wind conditions and turbine technology. The effective generation percentage typically falls within the range of 15% to 35%, with potential increases in optimal environments.
Does Wind Make Sense?
The first question is, did I get something wrong above? I’m not an expert on this. Reading books and articles, Google searches and queries to Perplexity & Gemini is information, not knowledge. And I’ve searched on this specific subject and found nothing like what I’ve laid out above.
Q: Does wind generation with gas backup produce less co2 than just a combined-cycle gas plant?
Gemini: If the wind turbines operate a majority of the time (e.g., over 60%), the wind-gas combo likely produces less CO2 than the combined cycle plant.
Perplexity: Wind generation with gas backup produces less CO2 than a CCGT when wind turbines are operational more than about 50% of the time.
Key to the difference is gas peaker plants need to be an open-cycle turbine because combined-cycle turbines take longer to spin up and their advantage is once they’re running fully hot. Is there something I missed in this?
And this is a constrained system. If the backup for Wind was batteries, or there are customers who are accepting of intermittent power, then there’s no need to fire up the backup turbine.
But as I understand Wind being used today – I don’t think it makes sense. Am I wrong?
Or is Wind generated energy a hallow bunny?
References
Average U.S. construction cost for onshore wind generation decreased by 27% since 2013
How Green Is Wind Power, Really? A New Report Tallies Up The Carbon Cost Of Renewables
Natural Gas Power Plant Costs for Operation & Maintenance- US
EWEA - FAQ (click through to new site)
Nice work. When you add grid requirements to support wind the numbers will skew even further in favor of CCGT. Scotland being a topical example at the moment. They can't utilize all the wind because it is too far from the demand and the network capacity is insufficient to transport it. Building out the network is another source of emissions and adds complexity.
Very good work here. Attaboy.
I’d suggest two more points:
you assume the turbines will not experience a “blade liberation event.” For more on that, see my substack on what happened this summer in Nantucket.
Second, wind projects are facing fierce opposition from landowners and elected officials all over the world. The economics and o&m issues are key. But land-use conflicts are constraining wind expansion.
Again, good work.