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Letters to the editor: volume 17, issue 12

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In the January 2023 issue of E&T, readers discuss the importance of getting terminology right, the potential of tidal power in the UK, and more.

Distinguish between power and energy

In our vital attempts to reach net zero in electricity production there is an ongoing conceptual battle between power and energy. Talking solely in energy terms conceals many important issues with intermittent renewables. Politicians, through ignorance, use the terms interchangeably although they have clear and distinct meanings even in everyday language: the power of a weightlifter, the energy of a long-distance runner, the power of an elderly dictator, the energy of young children. The technical meaning is no different and I would expect engineers to highlight that they are very different quantities.

E&T’s report that the Hornsea 2 windfarm off the Yorkshire coast is now fully operational (November 2022) says that a single rotation of each turbine blade produces enough energy to power an average UK home for 24 hours. Without carefully quantified and managed storage capacity a single rotation will only power a group of homes during the time the blade is rotating. One rotation will provide energy equivalent to that used by a home in 24 hours but not the actual time-varying power required by that home.

Equivalence is a fantasy with no practical meaning. My lifetime car mileage is equivalent to a return journey to the Moon. This tells us nothing about my space travel capabilities or my day-to-day driving activities.

The battle between the concepts of power and energy must be resolved if we are to have an engineered solution rather than just a popular fairy tale.

Richard Martin MIET

By email

It’s time to exploit tidal power

I am surprised and disappointed that so little consideration has been given to the exploitation of tidal power for the generation of electricity in the UK. We live on an island with accurately predictable tidal activity and full use should be made of this free resource, particularly in areas like the Bristol Channel where there is a very high rise and fall of tide.

If a typical hydroelectric installation also included desalination and electrolysis plants, there would be additional income from selling fresh water to onshore water companies to enable them to cope with the forecast increased periods of drought, and a supply of hydrogen gas would be available to replace natural gas used in conventional power stations, in appropriately converted internal combustion engines and fuel cells.

Surely, the initial cost of building these installations would be covered when all these products are marketed.

Peter Taylor CEng MIET

By email

Hydrogen hopes need a touch of realism

Further to the summary (E&T October 2022) of the National Engineering Policy Centre (NEPC) report calling for swift development of low-carbon hydrogen production capacity in the UK, I am reminded of an interesting caveat raised in a discussion on the subject at a meeting of the European Academies of Science and Engineering (EuroCASE) in Brussels in 2006.

Disregarding blue hydrogen produced by splitting natural gas and grey hydrogen resulting from steam methane reforming, notice should be taken in the production of carbon-free green hydrogen from the electrolysis of water of the requirements for significant quantities of both electrical power and fresh water.

This is well known in principle, but to put the comment in perspective, an extreme example considered was the amount of hydrogen required to power the daily flights from Frankfurt airport. At the time these comprised 252 daily flights of which 50 were Boeing 747 jumbo jets. Each 747 was loaded with 130t of kerosene, which, if powered by hydrogen instead, would have been replaced by 50t of liquid hydrogen. With 9kg of water producing 1kg hydrogen by electrolysis and requiring an energy balance of 1.3kWh of electricity per kWh of hydrogen energy produced, then, allowing for energy losses in liquefaction, transport and transfer of liquid hydrogen, well over 5GW of extra continuous electrical power capacity is needed for the 747s alone. Extending the fuelling and power demand to the remaining daily flights added the unexpected observation that the whole of the freshwater supply of the city of Frankfurt would be required! Such water-use implications had not featured in the energy debate.

The alkaline, solid oxide and proton-exchange membrane electrolysers now developed have much to offer in local situations, but the large-scale availability and deployment of green hydrogen from water electrolysis in industries such as primary steel-making, industrial heating and as a chemical feedstock for industrial processes, even if feasible given the electrical power requirements, would appear to favour UK locations with plentiful fresh water supplies such as Scotland and the North of England – perhaps a relevant observation given the present and recent water use restrictions in some areas of the country.

This has similarities with the development of industries in the industrial revolution over past centuries near to coal fields. As far as aviation is concerned, however, the industry-wide requirements are too large. For the same reasons, this would also be the case for hydrogen as the standby fuel for UK electricity supply with intermittent renewable energy sources.

The report from the 42 professional engineering organisations, including the IET, urges swift UK action in the use of hydrogen energy, “to avoid falling behind international competitors”. Hydrogen has often been seen by many as a possible free pass to the future in the debate on UK energy supply, certainly since the Kyoto Protocol was adopted in 1997. Political and environmental policies leading to a net-zero energy system will be constrained by the laws of physics and availability of resources, however, even if economic constraints are adjustable.

Michael Laughton FIET

By email

January 2023 Issue Letters Cartoon

Image credit: E&T

Inroads into fossil rules are unlikely

The story in November’s E&T reporting the use of renewables to meet the global rise in electricity demand conveniently ignores the fact that the global economy is largely dependent on fossil fuel.

If we consider the UK, with a net-zero commitment by 2050, this would be an economic disaster. Currently on a good day 40 per cent of our electricity is generated by renewables. The average figure is 15 per cent. Since electricity represents only 20 per cent of our total energy demand, the amount of energy provided by renewables is a mere 3 per cent. Oil and gas account for approximately 70 per cent.

The story includes a a comment by an energy analyst that “wind and solar are homegrown and cheap and are cutting the cost of bills and emissions fast”. The comparison with oil and gas is interesting – renewables cost us billions in subsidies whereas oil and gas contribute billions in tax revenue. At the present rate of progress, the generation of electricity solely by renewables could take as long as 100 years, and require substantial subsidies.

Another victim of the net-zero insanity is the phasing out of gas central heating boilers. The modern condensing combi boiler is around 95 per cent efficient and is the most common form of domestic heating. Replacing this with some form of electric heating would involve the following dilemma. Gas/electric conversion is around 40 per cent efficient. Oil/electric conversion (commonly used for wind power back-up) around 30 per cent efficient. Given the difficulties faced by renewables in the generation of electricity, it is unlikely they will make significant inroads into the oil and gas sector of our economy.

Let's get fracking!

Philip Cheetham MIET

By email

The slide-rule approach to safety

I agree with John Wheeler’s questions (Letters, November 2022) about how electric-vehicle designers approach charging strategy and reliability, and would like to extend the discussion to strategy and safety.

In 2021 there were twice as many accidents per mile driven by autonomous vehicles as there were by human-driven vehicles. Research into systems automation has conventionally put technology at the system’s centre. Here, the systems attempted to do everything and mostly failed. This techno-centric approach now appears to be adopted by autonomous driving car designers and is failing, again.

There are many cases where automated systems and humans work together extremely well. Currently, autonomous vehicles aim to travel at around 60 miles an hour. Systems automation and humans have melded and merged perfectly but not when going 1 mile a minute, but when travelling at over 20 miles a minute. In addition, the vehicles we have learnt this technology from do not reach 100 miles an hour, they reach in excess of 1,700 miles an hour. What are these vehicles? Vehicles run and operated by most air forces – jet aircraft.

The cognitive load on pilots is enormous. Continually working in four dimensions is stressful and life-threatening. Automation to assist pilots is therefore key and has been so for many years. We should be at a similar stage with cars. We should be looking for technology that assists and supports the driver in making their cognitive load lighter, but definitely not zero.

Work out the square root of 25 using a calculator and you almost always get the incomplete and wrong answer 5. Using a slide-rule, a human being (with a bit of thought) almost always gets the right answer +5 or -5. For today’s vehicles we should stop developing Solution Generators and start developing Decision Support Systems – systems that relieve the cognitive load on the driver and provide them with information enabling them to take decisive action instantly when they deem it necessary.

The term autonomous has at least two meanings; they are subtly different. The first definition states “Having the freedom to govern itself”, the second comes from Kantian philosophy and states “Acting in accordance with one’s moral duty rather than one’s desires”. When a level-5 autonomous EV gets confused by, for example, a person pushing a bicycle across the road and not alongside it, the system ‘desires’ one course of action. However the ‘moral duty’ must also be considered and an alternative action taken.

The strategic intent is clear: we should design and develop EV decision-support systems along the lines of slide-rules rather than calculators.

Andrew WS Ainger CEng FIET


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