What is the difference between capacity use factor (CUF) of solar power plant and plant load factor (PLF) of coal based power plant? Can we compare both since they seem analogous?
Electrical – CUF v/s PLF of power plants
power supplypower-generationsolar energy
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There are a few issues at play here.
First is the concept of a synchronized electrical grid, using the "infinite grid" approximation, in most cases a reduction in load on an electrical system will be imperceptibly distributed across all the generators in the grid. The load that a specific power plant sees is a managed load (managed in the context of the entire grid) and the system may respond to a large decrease in a number of ways outisde of the realm of a single generating station. If half of the entire load on the national grid drops out suddenly then you have bigger issues to deal with than a single coal generating plant going offline.
A generator will have a speed governor and a droop rating for the given prime mover (ratio of speed at full load vs no load) . A decrease in generator load will in general increase the rotational speed of generator from steady state, the speed governor will command the power plant to produce less torque (less heat or less steam into turbine) and decrease the rotational speed. In a synchronized grid setting this process is "clamped" - meaning that if the generator represents a small fraction of the grid power it will be unable to increase its frequency to the new steady state and will go out of sync with the grid if this doesn't happen reasonably quickly (or if it is a large fraction of power generated, take the whole grid out of sync)
What this means is if the load on your generator is suddenly decreased (say local sector load dump) it must compensate by decreasing prime mover torque output or dump power into a quick turn-on load to avoid risk losing synchronization with the grid
That being said power =/= energy. If your governor and prime mover have quick response (say seconds) in reducing generator output then 1s at 50MW is 50MJ, or approximately 13 W-hrs of energy. This is not a huge amount of energy in a power plant context and can easily be dissipated as heat through dump loads. If you need to divert 50MW for hours, this is a large amount of energy that will be better served using energy storage. You will need to determine the dynamic properties of the coal plant and prime mover to determine the best course of action.
E.G. if the turbine has a steam reservoir then the heat output of the coal is buffered and you are more likely to have quick control over prime mover output independent of the heat produced by the coal fire. Given enough physical energy storage (as heat in the reservoir) to ride out the load dump or buffer the turn down delay then excess power loads of some sort will be enough depending on the expected response. If the requirement is that "coal burner operates at louvres=100% for 100% of the time" Then yes, you need more energy storage, the most efficient being upstream of the generator (heat diversion) because conversion to mechanical force, then EMF, then any electrical storage then back to mechanical and EMF will be much less efficient overall, but I'm sure that this has been solved worldwide with much less handwaving and more hard economic numbers so you will have to read the literature.
I don't have experience with the specific models you are referencing but I do have experience with phase locking AC power sources. The bicycle analogy above is exactly how mechanical generators work and with solid state power inverters to the point of the inverter "pushing" on the grid however you don't want the grid to ever "push" on your inverter. The inverter watches the 60hz sine wave from the grid connection to trigger the driver to keep the output in phase with grid power. This is going to be a high impedance detection circuit so any source should do the job such as your pure wave inverter off a car battery. The listed tolerance on the sine wave is well outside the normal tolerance for mains. How precise is the frequency of the AC electricity network?
While connected to the grid it is critical the inverter is synced to the grid frequency and phase as tight as possible to prevent the inverter from seeing the grid as a load. If the grid were to have just gone down and your system started automatically the phase could be 90deg out of sync when the grid power is restored which would be worse than shorting the output of your inverter. This is why they inverter relies on an external clock source and shuts down if one is not present. Disconnected from the grid you have a self contained power system and the phase and frequency relationship to the grid is meaningless but the frequency does need to be close to 60hz for any devices you maybe running on that power.
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Best Answer
Plant load factor and capacity (use) factor are two names for the same thing: the ratio of mean power to rated nameplate capacity.
Capacity factors between very similar or identical technologies that are serving a similar role on the grid, can be comparable: e.g coal and gas CCGT plants both working as baseload, or both working as mid-merit, or both working as peakers.
However, capacity factors between very different technologies, or by plants serving very different roles, are not comparable. So no, coal and PV capacity factors are not comparable.
Wind capacity factors in the short term are mostly driven by weather, but over the long term are mostly driven by the farm design, as I explained elsewhere in more detail, previously.
In theory, all other relevant things being equal, a higher capacity factor is better than a lower one. However, all other relevant things are almost never equal, and it's rarely as simple as higher being better. Indeed, there are some fairly common circumstances where higher can be worse. If a wind farm was achieving 80% over the medium to long term, that almost certainly means that the windfarm designer has made a very expensive mistake - they should have designed for 20-60%, depending on the particular local weather and economics.