Power plants A

Up to 25% of a conventional power plant (synchronous ac rotating machine) generation can be used to operate plant .... to power the electromagnet, to run the pumps needed to circulate water used for cooling, etc. Resource: What is 3-phase electricity  Power-Plants.pdf 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
The grid must hold voltage steady. Power (wattage) is equal to volts x amps. Voltage is the force that pushes amperage or current of electrons across the wire. Even though power plants are interconnected, each power plant can only energize a certain distance or area. If several power plants go offline, or demand exceeds supply, then power must be shut off (load shed) to some customers so voltage levels can be maintained for remaining customers. If voltage drops below nominal, then your 115 volt refrigerator and 240 volt AC cannot run without damaging the motor. Why? Two reasons. 1) Lower volts reduces the magnetic field needed to spin rotor. Motor slows down and overheats. 2) Volts and amps are inversely proportional. If volts drop, then loads will draw more amps to meet the amount of watts (power) shown on product label. Wires are rated by amperage, and are generally not oversized (larger wire carries more amperage but costs more). Exceeding the amp rating means too many electrons are moving through the matrix (atomic structure) of the conductor (wire), causing more resistance from wire which causes heat which overheats design parameters of wires, motors etc... affecting substation relays that will trip off ... and can affect power plant generators that will automatically shut down to avoid damage.

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

The future will need .... new skills from labor ... innovation using electronics that are more vulnerable to lightning, solar storms and cyber attack ... changing standards to meet reliability goals ... protecting appliances with voltage monitors that shut off appliance if voltage drops ... implementing technologies ... all indicating that considerable costs will be passed onto customers ... and arguably 25% of the energy will be used to manufacture, retrofit and maintain changes.
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
Strong regulation, mandated demand response for homes and business, and real-time data, microgrids etc (distributed energy systems) might solve issue if available everywhere, but would be a steep incline from today and add considerable costs to gain participation by power producers and users. The capital expenditure and political compromise are unlikely without agreement that some will not get power. Read   Read

It should be noted that the promise of 'high-paying jobs in renewables' is not consistent with 'lower cost electricity.' Either you have good paying long-term jobs supported by rate-payers, or you have cheap electricity. These two things are opposites. In any case, there are few jobs once renewables are installed, and transmission lines built. Getting your picture taken wearing a white hard hat in front of a windmill does not equal a 'good job.'


Thermal generation from coal, atomic power ... oil, NG, LNG, LPG, hydrogen, gasified coal, ethanol, syngas, biodeiesel, alcohol, kerosene, steel mill gasses, etc image ... plus hydroelectric installations ... accelerate a turbine ... and the turbine rotates the generator to produce electricity.

"Total efficiency is defined as the sum of the net electricity generated divided by total fuel input to the system." This means the 60% thermal efficiency of a gas turbine is not same as the total efficiency. Total efficiency is unique to each turbine design, installation, fuel, etc. Total efficiency would be lower than thermal efficiency.
For example water heaters: A condensing gas water heater has 96% thermal efficiency, but overall efficiency of 82% because of various losses. Read

Typically, anything that obstructs or slows hot exhaust gasses from turbine or gas appliance etc, will cause the gas to burn slower and with less efficiency ... or extinguish the flame. The combined gas and steam (combined cycle) technology has solved problem and is being used to replace single-cycle gas generation around the globe where applicable.

Gas turbines can be massive or smaller units made for innovative fuels such as methane from a coal mine, gasified coal, biomass etc.
ANSI B133.6 Ratings and Performance defines base load as operation at 8,000 hours per year with 800 hours per start. It also defines peak load as operation at 1250 hours per year with five hours per start.

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
2018: "The IEA projects that total electricity demand will rise by nearly 60 percent through 2040, with total 8700 GW of power expected to be added in next 25 years." Source GE.