DAVE Gordon (Letters, April 4) questions the veracity of our proposals regarding the evidence presented in what he refers to as our "weak paper", Hydrogen Scotland, one of two papers released at the launch of our new think tank HIAlba-IDEA and available on our web site HIAlba.org. Our other paper, Maximizing Scotland’s Well Being by Bravely Innovating, is a detailed overview of a series of 10 papers that we hope to produce going forward, one of which is the Hydrogen Scotland paper.

Central to our proposals are the potentially game-changing technology for producing ammonia from renewable energy and extracting hydrogen from ammonia and the use of offshore wind power to achieve this. Although Mr. Gordon claims to "know how to assess evidence sources and knows his way around numbers", we note that much of the focus in his letter is on renewable energy sources that we do not regard as game-changing for Scotland, such as solar power and wave power. With regard to his point about solar power, we note that Mr Gordon does not give a source for his alternative claim other than his own experience.

It is important to note that our Hydrogen Scotland has as its first line "Preliminary report" and is published at this stage to provide readers with a better grasp of recent technological breakthroughs in the production of ammonia as discussed in our Outline paper. There will need to be a considerable amount of work done on that paper going forward to turn it into a Scottish version of the renewable hydrogen roadmap, produced in Australia, which will be necessary to take the application of the renewable hydrogen technology forward.

Our proposal of 25 Highland locations with 500MW capacity each are not intended to provide renewable energy for the whole of the Scottish economy. Rather they are examples of how the Highland economy could potentially be transformed with the use of renewable hydrogen, obviating the need for constraint payments, and how our proposals could work on a larger scale.

Indeed, our ambitions for renewable hydrogen are far greater than supplying the energy of Scotland alone, as our Greenprint notes. In this regard it is gratifying to note that a recent study reported in the media suggests that one half of the North Sea could potentially supply four times the energy needs of all of Europe. The current Hornsea One project with its 1.2GW capacity and ability to power one million homes is surely a leading indicator of the potential of what we are proposing and a realistic starting point.

Prof Ronald MacDonald and Dr Donald MacRae,

HIAlba-IDEA,

Viewfield Road, Portree, Isle of Skye.

DR Hamish Maclaren (Letters, April 1) berates my linguistic use of the word “generates” in reference to the manufacture of hydrogen, but then proceeds to write of the “capture” of energy by renewable devices. All these cases are of course, conversion of one form of energy into another. Would he wish to refer to the electricity in his home not as being “generated” by some device, but as “converted wind, solar heat or nuclear energy”, into electricity? I think readers will have little difficulty with the simple “generated”.

With reference to the occurrence of hydrogen, it certainly does not occur naturally in its simple molecular form, as a gas.

I stand by my original statement “more energy must be generated by other means, than can be recovered in its use”. Using electrolysis of water to manufacture gaseous hydrogen, about 80 per cent of the theoretical yield is obtained. If used in a fuel cell to obtain electrical energy, losses in inefficiency also occur. All other processes have inefficiencies. Methane does occur naturally, a rich source of heat energy.

I adhere to my view that hydrogen is too expensive to use as a substitute fuel, in domestic central heating systems. In the transport sector I would also doubt that it will be cheap enough in the foreseeable future to compete with hydrocarbons, particularly if taxed at the same level.

With regard to an alternative, this raises the question of the absolute influence of CO2 on our climate and more specifically on the impact of human activity on its atmospheric level. CO2 is not the main greenhouse gas, being way behind water vapour. It should be noted that CO2 is fundamental to life on Earth

I would thus be quite happy with 80 per cent of electricity from nuclear sources, the residue by Combined Cycle Gas Turbines (CCGT) using methane, and a move to the use of lighter hydrocarbons for transport purposes. But it would all be a slow and expensive process.

I do not see renewables alone as the future, most are much too chaotic, just like the weather they rely upon, and their integration into the Grid involves very considerable expense, and subsidies seem to be essential.

Richard Phillips,

Four Winds, Wickham Heath, Newbury, Berkshire.