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Unlike wind and solar (inverter-based) generation that must be changed into matching voltage and frequency (oscillations of electrons in AC electricity) as conventional generation, the coal-fired plants require large number of employees to keep plant operational, including welders, bulldozer operators, trainloads of coal etc.
Offsetting job losses as more renewables and DERs come on-line is the need for grid reliability ... specifically to keep voltage "within ±10% of nominal at all points across the grid." Keep in mind the grid is cris-crossed over millions of square miles, with millions of poles and transformers and customers ... comprising a system that might not be fully mapped at the local distribution level in 2021. Read

Utility-size generation from renewables like wind and solar has a large footprint (as does coal, oil and gas) that hinges on large-scale land acquisition usually located far from end users ... which requires further land access (permits) to build transmission lines to urban centers over objections by landowners etc. Read.  The less reliable renewables come with a "reduction in fault currents and short circuit strength" ... meaning that "voltage support might be a vital ancillary service to prevent voltage instability and ensure good power transfer." Renewables require gas-fired (and coal-fired) generators that sit idle but have fast ramp-up (startup) and turndown as needed (viewed as uneconomical or impractical?) .... but also require retrofitting the grid with capacitor banks, voltage regulators, tap changers, advanced inverters... and innovations such as massive installation of 'voltage smoothing batteries' (that can hold charge for limited time etc), compressed air storage, solid state transformers etc read  read2 read3 read4 read5 Resource: Electrification magazine

Utilities are challenged by aging networks ... challenged because grid updates are expensive, labor-intensive and often dangerous ... challenged by economic growth ... challenged by changing resource mix from solar and wind ... challenged by change from 'fuel-intensive emphasis into a “material-intensive” system' Read .... but also challenged by electric vehicles that will try to replace the entire gasoline resource with electric resource, etc. Read Read Read Read.pdf Utilities are also challenged by the perception in some countries that gas pipelines, LNG (liquified nat gas) and related infrastructure are a menace at same time natural gas (and gas of all types) is a primary source of energy for baseline power generation across the globe, see image and back-up generation for intermittent renewables Chart Chart Chart Chart ... and gas is predicted to be a primary source of energy for electric generation over next 20 years despite expectation that 'renewable generation will double by mid-century.' Image Image Chart  Image  Source Resource:  Dallas Federal Reserve Research

In my opinion, the promise of 'lower costs' and 'money-saving' from renewables (low-cost variable renewable energy or VRE) might not happen in the long run, and ultimately less-reliable renewables will be an expensive way to generate electricity if the purpose is to supply power to everyone. Read   Image  Read  Why? If too many renewables are supplying power at same time, there will be a glut of power ... and prices will fall below profitability. This will force utilities to install costly batteries ... while demand for batteries is spiking across globe ... skewing the cost of renewable generation. Without batteries, the renewables cannot withhold dispatch of power until after dark, or when wind dies down, when power is scarce and prices increase. The uncertainty in generation will be hard to regulate, at a time when regulation is often seen as dis-incentive, leading to fragmented (PPAs etc) and unpredictable grid, eventually causing shortage of affordable power.   Video   PowerOutage.us

2015: "Combined cycle turbine plants (50-60% efficient) contribute to base-load power needs, while single cycle turbines (30-40% efficiency) are used for meeting peak-load," or used for smaller operations, including portable generation. For example, "utilities often place a single-cycle gas turbine in the 5 to 40 MW size range at substations to provide incremental capacity and grid support."  Source
A single-cycle turbine is typically necessary to compliment intermittent generation from renewables, affecting overall efficiency and CO2 production attributed to renewables. "Efficiency of a turbine at part load can be substantially below the 30-40% efficiency at full-power," while continual stops and starts degrade a turbine more rapidly ... causing more non-recoverable losses and higher maintenance to repair recoverable losses. Gas turbine failure modes .pdf     Read advancements in turbomachinery

Pie chart image from OECD
In 2021, renewables (Hydro, wind, solar) generate about 29% of world production, while Fossil Energy (FE) generates 53%, and atomic contributes 17%. Image Image Image

-Power lines and towers are designed to withstand load factors such as heat, ice and high wind.

Suspension clamp U bolt type
Preformed armor grip suspension clamp

The grid is a balance of cost and function. The high cost of building and updating transmission lines might cause undersizing. The resulting shortages might be mitigated by local generation from solar panels, batteries etc (microgrids). But a fragmented grid means some people would not have power, or only receive power a few hours per day as experienced in some countries.

Let's suppose, if all homes in a neighborhood install solar panels. In Hawaii, it was determined that just 50% of homes feeding PV-generated power back to the grid on a good day posed problems that required updating distribution lines and substation transformers. IF a neighborhood has underground distribution lines, then updating might be more expensive than above-ground distribution. In any case, the cost of distribution improvements should be included when calculating the value of rooftop solar. Microgrid experiments in Austrailia are installing pole-mounted batteries that are charged during day and help supply power to 3000 homes at night.

3-phase 7200 volt distribution lines arrive at building service

Fig-A is called 'concentric round' since each strand is identical, each is round, and cable is round. Diameter 0.795." or .455 square inches.
This wire was laying on the ground as part of the installation of new Distribution lines along the freeway.

Note: "each layer in a conductor is wound in the opposite direction"

''Air space between strands can be reduced by compacting the aluminum conductor into trapezoidal shape for a more compact wire size."
Wire in Fig-B was laying on the ground as part of the installation of new Subtransmission lines along a local highway.

Color difference added for clarity