THE public are generally aware that the key sources of renewable energy including wind and solar are variable and intermittent which results in their needing back-up when supply cannot meet demand or indeed when renewables output frequently collapses and such back-up includes the running of quick-responding gas turbine generation and hydro power including pumped storage.

Superficially this seems simple. However, there is considerable background serious and complex power systems science behind ensuring security of supply.

As we close down major coal, nuclear and older gas-powered generating stations and replace them with wind and solar we have progressively less rotational inertia, which is stored energy, within the Grid to support our electrical frequency during system disturbances and Scotland, in particular, will be acutely challenged when Torness closes in a few years followed later by the Peterhead gas turbine station, which is seriously elderly and cannot run indefinitely. Loss of system inertia results in frequency changing much more quickly when faults occur, increasing the risk of supplies being tripped, including domestic to prevent danger at home.

A second major challenge is to generate sufficient reactive power (wattless Megavars) around the country to support voltage as it does not travel well and is not source produced by renewables. Also without reactive power we cannot create magnetic fields which transform electrical energy into mechanical energy and run equipment.

Hydro annual output in 2021/22 in Scotland was 10.7% of demand but in 22/23 was down to 8.7%. This will be partly due to Scotland's total generation output having grown via start-up of new renewables with no new hydro capacity being available but, I suspect, the measured hydro active power output of 10.7% likely also reduced over the year because quick-responding hydro stations like Foyers were periodically being run to only output reactive Megavars and not active Megawatts in order to keep the north of Scotland voltage afloat. Insufficient reactive power will cause the grid voltage to collapse in a very few seconds.

Rarely aired is the dirty secret regarding the variable amounts of methane produced by hydro, including pumped storage, from organics in the reservoir water when they are generating as it bubbles out of solution. Methane, of course is around 85 times more potent as a greenhouse gas than CO2 over 20 years. The UK, whilst more temperate than warmer countries, is now not regarded as immune from this problem now being seriously studied across the globe.

So electrical power systems are immensely more complex than simply installing Megawatts of renewables generation to match Megawatts of load demand and the UK is having to introduce huge and expensive catch-up changes to protect the grid system as a result of our un-coordinated rush to renewables, all of whose huge costs are over and above the oft-quoted Contracts for Difference strike prices for renewables generation and will be largely if not totally met via our bills.

DB Watson, Cumbernauld.

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The disabled bay villains

AS an old retired “git” with lots of time on my hands, one of my greatest pleasures is to sound off regarding those people (of whom there are many) who irritate or annoy me (such as people who smoke within a 10-mile radius of wherever I happen to be at any given moment).

On this particular occasion, I write with regard to a practice which absolutely sickens me. This is the practice by non-disabled individuals of parking in disabled spaces. The practice sickens me because it demonstrates vividly the contempt which these people have for those who have a disability. The people who engage in this practice are ignorant, arrogant, selfish and lazy. They are beyond contempt and devoid of any shred of decency or integrity. Don’t waste your breath appealing to their consciences; they have none.

My views on crime and punishment, as my friends would testify, are slightly to the right of Vlad the Impaler. With that in mind, what I’d like to see done with such people is not fit for publication in a family newspaper. I would settle for the vehicles being seized, impounded and either sold for charity or destroyed. My concern for the sensitivities of your readers prevents me from voicing my views on how the individuals themselves should be dealt with.

The root of the problem, of course, is the fact that virtually all disabled spaces (outside supermarkets and the like) are purely advisory. As matters stand, those responsible for the management of these spaces might as well erect a sign indicating “Reserved for the use of non-disabled drivers. Those drivers with a disability kindly park somewhere else”. The Government needs to introduce legislation making it a criminal offence for any non-disabled person to park in such a place. The sanctions against these individuals would require, obviously, to be draconian.

If non-disabled people knew, with certainty, that they would, on every occasion, be caught, prosecuted, convicted and jailed, maybe, just maybe, they would think twice about indulging in this practice.

And, yes, I am classed as having a medical disability.

Alastair MacGregor, Hamilton.

Pronounced difficulties

ON the question of distorted English pronunciation (Letters, March 29 & April 2), I had reason to contact Sky recently and had to run the gauntlet of a series of automated security questions. One of these was to verify my postcode which includes the letter A. I could not make the bot understand, even after several attempts. I was asked repeatedly if Y was correct. Eventually I sounded the A as Aye. This was successful.

This is not just a moan about accents for the sake of it; this is about the ridiculous evolving of the English language into something unintelligible, to the point where we can be denied a service if we do not kowtow to the affectations of pronunciation now reaching epidemic proportions.

John O'Kane, Glasgow.

The Herald: Disabled parking bays are often abusedDisabled parking bays are often abused (Image: PA)

Sum difference

JOHN Birkett's experiences of 1950s CA training (Letters, April 2) demanded a higher level of intelligence than did mine.

In distinguishing between the debit and credit sides of the cash book, all that I had to remember was that the debit side was the side nearer the window.

David Miller, Milngavie.