GRID INERTIA : AND WHY IT MATTERS IN A RENEWABLE WORLD

In an electrical grid system the rotational energy contained in generators and motors at power stations acts as a buffer against short term fluctuations in the energy supply

This is called “inertia” https://www.renewableenergyworld.com/2019/10/25/grid-inertia-why-it-matters-in-a-renewable-world/

EDITED VERSION

If demand for power increases the frequency of the grid tends to decrease as inertia gets drawn out of these rotating machines before they can respond with extra power generation from their steam turbine or other source

Having a lot of rotating mass on the grid acts like a shock absorber and slows the rate of frequency change by releasing rotational energy while waiting for the response of the primary power source

The typical mechanism for providing this “inertia” is to use the mass of the heavy rotating equipment such as steam turbines and gas turbines and the rotating generators that they are driving through fixed mechanical connections

System operators are engaged in a constant load balancing act using frequency as their “distress signal”

A power network without sufficient inertia is one that can become unstable and will suffer from issues of power quality and be susceptible to blackouts

If frequency goes out of control, parts of the system may have to shut down

This can also then cause severe strain on the rest of the network

If not dealt with promptly, these cascading outages can lead to major blackouts like that experienced in the Northeast USA in 2003

- 60 million people ended up without electricity

In the summer of 2019 major blackouts in New York City and the U.K. further emphasize the need for greater grid resilience

“When system inertia is decreased, sudden changes in frequency caused by changes in electricity consumption or production are faster and larger,” said Minna Laasonen, senior advisor at Fingrid, the transmission operator in Finland

“This means that it is more difficult to keep the frequency within its normal range of variation”

Renewable energy systems based purely on Solar effectively have no “inertia” because there are no mechanical rotating parts

Even massive wind turbines do not provide mechanical “inertia” because their generators are not directly connected to the grid

Instead, an electrical frequency converter is used between the electrical grid and the mechanical wind turbine and its generator electricity

This prevents the kinetic energy of the wind turbine’s rotating mass from providing “inertia” to the grid in response to frequency change

The newly emerging solution for this reduction in mechanical “inertia” is to compensate for it with electrical “inertia” provided by the storage batteries that are increasingly becoming an essential part of renewable electricity grid systems