Some recent back-and-forth's seemed to hint at the idea that we might want to discuss power generation in a bit more depth given the push for electrification and confusion surrounding some of the terminology. I'll preface this with the fact that I'm personally very pro-nuclear and pro-hydro but they each have their own merits and detractors just like any other source.
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In terms of actual thermal plant operation,
@Shannow has likely forgotten more about this topic than I know, but I don't think we need to get that deep.
First off, before getting into the sources themselves we should clarify some language that is regularly used and that quite often, the media uses incorrectly, swapping MW for MWh and similar.
Nameplate Capacity: Often abbreviated to just "capacity". This is the installed capacity for a specific source, typically in MW. It can apply to a single unit or as a whole, so a wind turbine can be 3MW or wind capacity can be 5,000MW speaking as to all units as a collective on a given grid, farm...etc.
Output: This is the amount of power a facility or generation unit produces, expressed typically in kWh, MWh, GWh, TWh. So, for example, a 1,000MW Nuclear reactor could theoretically produce: 1000x24x365=8,760,000MWh; 8,760GWh; 8.76TWh a year.
Capacity Factor: This is the amount of output, relative to Nameplate Capacity, that a facility or unit actually produces. So, that 1,000MW unit above, US nuclear units have an average CF of 93%, so in terms of Capacity that means 930MW, or in terms of Output 8.15TWh a year.
Each source we are going to discuss has wildly different capacity factors, which in turn means that their Installed Capacity (Nameplate) will not align with their relative contribution. This creates a lot of confusion particularly when we bring in things like Anticipated Capacity, which is essentially just a snapshot of CF for a specific period rather than the whole year.
Getting into the sources themselves now:
1. Nuclear
Pros:
- Very high Capacity Factor (highest of any source)
- Very predictable output
- Excellent baseload generator
- Small footprint
- Very cheap fuel
- Very low fuel consumption (refuelling period is typically every 18-24 months for a US PWR/BWR)
- Very high fuel security (fuel is stored on-site, so not vulnerable to supply disruption issues)
- Hardened and secured facilities are typically less vulnerable to weather related issues
Cons:
- Extremely high CAPEX (expensive to build)
- Relatively high OPEX (nukes have a considerable amount of staff)
- Poor load following capability (nukes can load follow, see: France, but economics are impacted, and fuel cycling becomes more frequent, lowest OPEX is baseload)
- Large unit size means that a single unit trip results in considerable capacity disappearing
- Long-term management of waste/used fuel, despite small footprint, will be required post-decommissioning
2. Hydro
Pros:
- High capacity factor (usually 60-80%)
- Very predictable output
- Excellent baseload generator
- Excellent load-following generator
- Excellent peaking generator
- Zero cost fuel
- Extremely low OPEX
- High fuel security (draughts that impact hydro output are reasonably rare)
- Hardened and secured facilities (dam operation centres are often inside the dam or in robust buildings nearby. The units themselves are contained.)
Cons:
- High CAPEX (expensive to build)
- Geography dependant (cannot be built everywhere)
- Extremely large footprint (reservoir setups)
- Large environmental impact for reservoir setups (run of river is better, but has no reserve capacity)
- Vulnerable to long-term supply shortage, IE, rare draughts that reduce water availability
- Cannot run at 100% constantly due to water flows/reservoir capacity
- Permanent landscape/nature/water disruption even after facility is EOL
3. Coal
Pros:
- High capacity factor (usually next after nuclear)
- Excellent baseload generator
- Decent load-following generator
- Low OPEX
- Low CAPEX
- Good fuel security (coal is stored onsite)
- Relatively self-contained facilities are typically very low in terms vulnerability to extreme weather-related issues
Cons:
- Poor peaking generator (slow ramp)
- Relatively high footprint if significant coal is kept onsite or plant is adjacent to mine
- Very high emissions footprint (highest of any source)
- Extended supply disruptions could impact generation (if coal is shipped or brought in by rail)
4. Gas
Pros:
- High capacity factor (particularly with steam thermal plants and baseload CCGT's)
- Excellent baseload generator
- Excellent load-following generator (GT/CCGT)
- Excellent peaking generator (GT/CCGT)
- Small footprint
- Low OPEX
- Low CAPEX
- Relatively self-contained facilities can be setup to be of low vulnerability to weather events
Cons:
- High emissions footprint (lower than coal, but that's not setting the bar very high)
- JIT delivery of fuel means extremely vulnerable to supply disruptions
5. Wind
Pros:
- Extremely low OPEX
- Extremely low CAPEX
- Small footprint (per unit)
- Low lifecycle emissions (similar to nuclear)
Cons:
- Tends to produce out of phase with demand
- Variability means it must be backed 1:1 relative to nameplate, typically with gas
- Susceptible to extreme weather (extreme heat w/no wind, extreme wind: turbines shut down, extreme cold w/no wind...etc)
- Medium-low capacity factor (~30-40% depending on location)
- Susceptible to seasonal variance not reflected in overall CF (summer CF can be quite low depending on geography, in the order of 12-15%)
- Short lifespan (~20 years)
- Diffuse (multiple generators must be installed over a large area to prevent shadowing and achieve significant installed capacity)
- Significant transmission requirements due to the above
6. Solar
Pros:
- Relatively low CAPEX
- Extremely low OPEX
- Reasonably low lifecycle emissions (about double that of hydro)
- Output tends to align with a large portion of daytime peaking requirements during the summer months
- Can be roof-mounted
Cons:
- Low density
- Large footprint (commercial, 10MW nameplate can take up almost 200 acres)
- Extremely low capacity factor (12-24% depending on latitude)
- Even lower winter capacity factor
- Short lifespan (~20-25 years)
- Susceptible to extreme weather (hail damage for example)
- Variability in output means it must be backed with either storage to cover the morning/evening ramps or 1:1 capacity in the form of gas
I'm sure there are some I've forgotten.
So, let's say we want to replace 5,000MW of baseload coal with wind.
- We would not install 5,000MW of wind, because on average, at say 33% CF, that 5,000MW of wind would produce 1,650MW.
- We'd install significantly more nameplate wind capacity than the coal capacity we want to replace to give us our average of ~5,000MW, on the order of about 15,000MW, which would provide similar annual output to the coal plant.
- We'd firm it with fast-ramp GT gas capacity of ~5,000MW nameplate that would fill for when it isn't windy. We'd also be able to export wind when output was higher than planned capacity, or curtail it if nobody needs it, at low cost.
The above is how you get into a situation where in terms of installed capacity, wind is one of the largest generators, but in terms of actual sources of electricity, may be quite a ways down the list. I'll use Ontario as an example, from this page:
ieso.ca
You can see that wind, at 12% of installed capacity accounts for 8% of power generated (most wind is exported, not reflected in these diagrams) yet nuclear at only 34% of installed capacity produced 60%, and that's despite being down two units for refurbishment last year. Nuclear output in Ontario can approach 100TWh with all units online.
View attachment 46026View attachment 46027
Gas capacity, which is primarily used for load following above the capability of hydro and peaking is the least utilized.
So in a very gas/wind heavy grid, gas being displaced by wind will result in a similar situation where the wind share of total output is lower than installed capacity might suggest but gas nameplate is higher than its output might suggest, because of that displacement.
Nukes are typically, as the Ontario data shows, on the other end of the spectrum, run typically in 100% baseload and satisfying a larger share of the annual demand than one might think.
Please discuss! (nicely!) and if you have questions on any of the above, I'll try and answer to the best of my ability. These are generalized so there are of course certain statements that exceptions may apply to. I've also not included more niche generators or ones that are going out of popularity like oil, geothermal...etc for the sake of keeping this brief, nor have I included massive pumped storage projects, as they mostly fall under the hydro category, but in a more limited capacity.
