Measuring our carbon footprints
"I have become increasingly concerned about global warming. But I find that living in a way that protects the environment and minimises the CO2 footprint is fraught with difficulties.
For example, I have installed solar cells which generate electricity. I am not sure that the energy used to produce the cells, the use of possibly rare materials in their manufacture, their limited life, and the problem of disposal when their life is over makes these ‘good’ for our environment.
Similarly for electric cars, wind turbines and other devices.
By recycling materials, do we actually save energy, use fewer resources and reduce CO2 emissions? Is there such a thing as a zero carbon footprint?
To assist in living more responsibly, it would be helpful to know the CO2 footprint of products we purchase in terms of CO2/year, including manufacture, transport, the expected life of the product, the cost to the environment of disposal and the use of rare materials. The effect of travel and transport could be in CO2/mile/person and energy as CO2/kWh and include the construction of the generating plant, maintenance, life and final disposal.
With this information we would have a better understanding of the benefits of the so-called environmentally friendly technologies, and comparisons could be made between different transport systems or types of energy."
John Haigh, Hexham, Northumberland
Down-to-Earth origin of the microwave
"You asked whether space exploration was still a worthy endeavour (Your Voice, Professional Engineering No 7, 2018).
J R S Uttley replied that the benefits of advanced engineering often migrate to everyday life. “So it is with space exploration, a simple example of which is the microwave oven.” While I agree wholeheartedly with his opinion, I cannot agree with his facts.
In summer 1957 I was involved in the R&D department of Proctor Electric in Philadelphia in the tear-down and assessment of a competitor’s fridge-size microwave oven, designed and built in the preceding 18 months. Sputnik 1 was launched later, in about September 1957.
I am unable to recall a function in the earliest satellites that relied critically on microwaves, although later satellites exploited them. Useful high-power microwaves resulted from the development of the magnetron by radar engineers in the 1940s, in Birmingham and MIT, well before space travel."
Justin Warwick, Buckhurst Hill, Essex
High cost hydrogen?
"Are hydrogen trains really such a great idea (“Fuelling the future,” Professional Engineering No 7, 2018)?
If the hydrogen fuel is made by electrolysis, the electricity has been diverted from reducing gas or coal-fired generation, or perhaps from heat pumps, which cut CO2 emissions from gas or oil-fired heating. Hence electrolytic hydrogen has effective CO2 emissions similar to those of natural gas.
So we may as well use natural gas to drive the trains, since the end-to-end efficiency of a hybrid natural gas driven internal combustion-electric drive would be similar to that of electrolysis to hydrogen and fuel-cell conversion of hydrogen to power. This also avoids additional costs for storage of hydrogen, which has one-third the volumetric energy density of natural gas. If hydrogen is made from natural gas without carbon capture, the same argument applies.
A lower-cost solution with no local emissions may be available; fuel cells are still quite costly, so it would make sense to build them into a hybrid drive, with batteries supplying much of the peak power, and recycling energy from regenerative braking.
How do the costs of a hydrogen train, and associated infrastructure, compare with a battery plus partial electrification solution, installing overhead power to drive the train and recharge the batteries on sections of track where power demand is high, such as leaving stations and uphill? The train would then be battery driven over expensive to electrify parts of the route such as tunnels and low bridges and on downhill or flat sections.
I suspect that either non-hydrogen approach will be more cost effective, with lower net energy use and overall CO2 emissions."
Richard Jefferys, Berkhamsted, Hertfordshire
Just pay engineers more
"The letter entitled “Money talks when it comes to recruiting” reflects the main reason for the shortage of suitable applicants for engineering positions that so many employers complain about (Professional Engineering No 6, 2018).
Why is it taking so long for them to realise the obvious? Increases in real average incomes have fallen badly behind rising costs, in particular housing, in the last 10 years since the financial crash. Industry leaders should take note and look to Germany for a comparison of engineers’ salaries in relation to costs, also to those of other professions, rather than just trying to talk up all the secondary attractions.
I also graduated about 50 years ago and ever since have been seeing articles about how British engineers are not rewarded properly. The shortage of qualified engineers has given rise to the often-reported need for recruiting from overseas.
Many years ago I saw a salary survey by the IMechE comparing several professions and seem to remember it showed engineering at about 10th out of the 12 listed. I wonder where it sits now in the table? Perhaps it might be a good time to do another comparison survey.
Also there appear to be big differences between engineering disciplines. The research reported on page 61 of Professional Engineering No 7, 2018 shows mechanical engineering well down the list."
Jonathan Eadon-Smith, Beaconsfield, Bucks
Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.