COUSINS Donald MacRae and Ronald MacDonald have eminent credentials. So it is puzzling how their think-tank HiAlba could produce such a weak paper as Hydrogen Scotland: A Route to Export Powerhouse ("The key to bottled health and wind? Bottled sunshine and wind", The Herald, March 26, and Letters, March 28 & 29 and April 2).

I am neither economist nor scientist, but I know how to assess evidence sources and I know my way around numbers. I know to be wary of any document that is undated, as are both the papers on HiAlba’s website. It is a small point but one that often separates the robust from the flimsy.

The evidence sources in Hydrogen Scotland are a mixter-maxter of the robust, the weak and the speculative presented with a very positive spin. The creation of Wave Energy Scotland in 2014, for example, is presented as a forward-looking act, when it was an attempt to salvage something (not least political face) from decades of failure to develop wave energy as a viable energy source. This was thought interesting enough to embolden the text, yet the supporting reference is a report on a project to digitise images of Scottish minerals, not an assessment of their quantity or extraction potential. Solar panels are quoted as losing 10-25 per cent of their generation potential on cloudy days. I wish I had those panels: our experience is of much higher "loss" than that, with days in winter when nothing is generated at all and random days with very low generation even in summer. When "supporting" material of which I know something is dubious, I become wary of the quality of the material about which I lack personal knowledge.

This may be to do the paper a disservice. It is intended, I think, to act as a think-piece – a stimulus to jolt our thinking out of the tramlines. As one who worked with numbers, I perhaps lack the imagination to make such a leap. Yet no matter how high a flight of fancy soars, if the numbers don’t work, it will crash.

The challenge we are presented with in Scotland is changing heating and transport from fossil fuels to lower carbon energy. If ammonia/hydrogen is the storage solution to counter the uncontrollable variation in renewable sources then one might expect Hydrogen Scotland to include some numbers to demonstrate its potential to meet the challenge and the level of renewable capacity needed. It does not. Instead it takes a South Korean plan to replace 26,000 natural gas buses with hydrogen buses and calculates that this would need 8.7GW of generation capacity which, with added capacity for local supply and manufacturing industries, is proposed as 25 Highland locations with 500MW capacity each. To give an idea of scale, this is nearly the size of the Whitelee wind farm (540MW) and a little smaller than the Beatrice offshore wind farm (590MW). In total, it is equivalent to all the wind farms currently in operation in Scotland. Does that help us replace gas with renewables? No. It will “scarcely make a dent in this [British] demand” as the paper itself admits.

Hydrogen Scotland is the first in a series of proposed papers. Let us hope that future papers are based only on robust evidence and hard-nosed about the numbers.

(Dr) Dave Gordon,

60 Bonhard Road, Scone, Perthshire.

I AM astonished that as well-informed a correspondent as Alasdair Galloway (Letters, April 2) should make the mistake of stating that water “changes to its two constituent gases” at 100 degrees centigrade. The chemical bond between hydrogen and oxygen is not broken by temperature: the compound H2O is a solid (ice) at temperatures below zero degrees centigrade, a gas (steam) at temperatures above 100 degrees, and a liquid (water) at temperatures in between.

That, of course, was not the main point of Mr Galloway’s letter, with which I have no disagreement whatever.

Derrick McClure,

4 Rosehill Terrace, Aberdeen.