Scotland's story of a power sector in transition is being played out in many countries around the world.

The centralised, large, fossil-fuel generation model is being unravelled with every new megawatt of renewable generation.

The role of "baseload" thermal power is being eroded rapidly as renewable technologies are effectively taking the place of conventional fossil fuel power plants. Already in Germany we are seeing periods when fossil fuel power is scarcely required. The impact is most clearly seen in the decision by German utility E.On to radically restructure its business model to cut off its nuclear, oil, coal and gas operations and focus on renewables.

In Scotland, the debate on the energy transition is taking place in microcosm as policymakers and industry grapple with the future of Longannet coal-fired power plant. Today, the Scottish Parliament's Energy Committee will discuss Longannet's future with National Grid and the station's owners, ScottishPower.

This comes ahead of an imminent decision by National Grid that will either signal its likely closure or provide a temporary reprieve. Either way the writing is on the wall; the question is not if Longannet will close, but when?

Despite the political heat and noise generated, Longannet's potential closure comes as no surprise to those who work in the energy industry. As Minister Fergus Ewing pointed out in the Scottish Parliament recently, Longannet was originally built to have a lifespan of 25 years rather than the 42 years during which it has already operated.

The Scottish Government's climate plan assumes it will close by 2020. As it enters its twilight years, EU air pollution regulations, UK carbon pricing and the cost of transmission are combining with its age to further impact on its profitability and force its closure.

For the National Grid, charged with keeping the lights on, the key question is: would the closure of Longannet in 2016 threaten security of supply? Strikingly for a naturally conservative organisation, National Grid made clear in a recent open letter that Scotland will not need either Longannet or Peterhead gas station on a regular basis to meet electricity demand, even when the wind doesn't blow.

However, until new transmission upgrades are completed, including the "Western bootstrap" link that goes live in 2017, National Grid is proceeding with great caution by contracting voltage control support to ensure against a one in 600-year extreme event.

Whichever generator the contract goes to, it marks a watershed moment in the role of fossil-fuelled electricity generation in Scotland. As renewables play a bigger role in our mix, going from strength to strength to become the biggest source of power in Scotland in the first half of 2014, fossil-fuel power stations are reduced to playing a limited background, supporting and transitional role.

In fact, as a recent independent engineering report for WWF showed, Scotland could credibly, securely and cost effectively have almost entirely renewable generation by 2030, without coal, gas or nuclear in Scotland (except for 340MW of CCS at Peterhead), as long as it remains part of the GB grid.

It could even continue to be a net "exporter" of power over the course of the year. In an increasingly interconnected era, there will be days when Scotland uses power from the south but the balance will be firmly in Scotland's favour. Greater emphasis on reducing electricity use, flexible pumped storage, interconnection and smarter energy management would all play an important part in achieving a renewable-powered Scotland, provided that the right policies are in place.

Unquestionably, from where we are at present to the 2030 vision represents a step change in the way we understand and operate our electricity system. But, as today's debate on Longannet demonstrates, the transition is well under way and increasingly aligned with commercial and technological realities. We just need to decide, like King Canute, whether we're going to try and hold back the tide or ride the wave of the renewables revolution.