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Letters to the editor: volume 16, issue 7

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In the August 2021 issue of E&T, readers discuss the future of motor transport, green approaches to domestic heating, and more.

Future vehicle solutions lie outside the box

There’s been plenty of recent debate on the subject of switching from internal combustion engine vehicles to electric vehicles, and it seems that we are all fixated on the concept of swapping one form of energy for another, without stepping back to look at the bigger picture.

Imagine that the motor car didn’t exist, and that someone had come up with the idea that in order to transport a person weighing less than 100kg from one place to another, we should encase them in a metal and plastic cocoon weighing around 2000kg, and carrying either 50kg of highly flammable fuel (petrol) or 100kg of toxic chemicals (batteries).

We would probably think the inventor was deranged and that the idea would never become a reality. And yet here we are, making extensive and destructive use of the motor car, spending extraordinary amounts of money, and using valuable resources, most of which are wasted on simply transporting the vehicle and its fuel.

Surely, as engineers, we can see that whatever the energy source, the whole concept of the motor car is absurdly inefficient and simply unsustainable in the long term.

Isn’t it time we started thinking well outside the box, and began working towards a different, much more sustainable, and much less wasteful means of conducting our business and our lives? If the Covid pandemic has taught us anything, it has to be that society and economies can continue to function with vastly less movement of people around the world. Maybe we owe it to future generations to use this opportunity to create a ‘new normal’ that doesn’t need motor cars and mass movement of people?

Bryan Hay MIET

By email

Water storage needn’t be a problem

Jonathan Barker asks where hot-water storage will go when gas-fired boilers are eliminated (Letters, June 2021). I have recently had installed both a 14kW air-source heat pump system (ASHP) and a roof-mounted solar heat panel. This was to replace an oil-fired hot water and central heating system.

The new hot-water cylinder, containing separate heat-exchanger coils for the ASHP and the solar panel, replaced the old cold-water storage tank in the loft and the hot-water cylinder in an airing cupboard. The cold-water tank probably contained about 700kg of water. The new cylinder, for a sealed system pressurised by the mains water supply, has a capacity of 210 litres and so weighs much less when full.

So far, we have experienced a more than adequate supply of hot water at about 50 degrees C and all of that heat came either from the air or from the sun. We have not yet drawn off enough hot water at any time to exhaust the supply available in the top of the cylinder, and the temperature at the return connection of the hot-water circuit returns to the set level after about 30 minutes of ASHP operation.

The solar panel, measuring approximately 1 square metre, is particularly effective, even in the recent cold and damp June weather, providing at least a supply of warm water to the cylinder and often, in sunlight, more than enough heat to supply the whole domestic demand.

Does anyone want to buy an unwanted oil tank and oil boiler?

Anthony Knight FIET

Midhurst, West Sussex

DIY answer to green heating

When I extended my house ten years ago, I took the opportunity of increasing the size of my vented gravity water-storage tank incorporating two coils: one that can be conventionally heated by a gas boiler and a lower coil fed from a collector panel of evacuated tubes on the roof. Aesthetic and taking much less space than photovoltaic panels.

When a temperature differential occurs between the collector and the ‘bottom’ of the tank, a pump in the loft circulates this ‘loop’ to utilise this ‘free’ water heating to the lower coil. In summer the temperature of the loop far exceeds the melting point of standard solder joints in the 15mm copper pipework, so care must be taken to account for installation methods. A small expansion tank built onto the pump provides protection.

This means that I have virtually free hot water for deep baths all year with only the winter months needing to be partially supported by gas. My gas bill is embarrassingly low and is sometimes questioned. With a well insulated loft and tank, I also still have a snug airing cupboard: an often unappreciated advantage for towels/fabric storage and wine fermenting.

I installed the system myself with a controller that instantly tells me temperatures at top and bottom of the tank and also collector temperature so I know if it ever needs any backup. At a cost of £1500 for materials this has been one of the most economical and ‘green’ solutions I have found, and I would heartily recommend it.

Bob Newton TMIET


Heat pump arithmetic

The high cost of air/water heat pumps is clearly of great significance. However, is the government plan to replace all domestic gas boilers with heat pumps sound? A typical ‘medium’ household with gas heating consumes 12,000kWh of gas annually. When this is burned in a condensing boiler, operating at 95 per cent efficiency, 11,400kWh of heat is produced. An air/water heat pump operating at a typical cool weather COP of 1.8 will consume 6335kWh of electricity to produce the same heat output of 11,400kWh.

Most of the electricity use will occur during the morning and early evening periods of peak demand. For the foreseeable future these peaks will be satisfied by gas turbine generators. Typical gas turbines used for peak lopping have efficiencies of about 35 per cent. 6335kWh of heat-pump input power will require 18,100kWh of gas turbine generation. This means that 12,000kWh of domestic gas will be replaced by 18,000kWh of gas-generated electricity.

This is a net overall increase of 6,000kWh of gas with the consequent increase of greenhouse CO2.

This arithmetic is fairly simple and doesn’t account for every nuance of household habits. However, it shows that multiple air/water heat pumps will almost certainly cause the release of more CO2 than the condensing boilers they are expected to replace.



Letters page cartoon

Image credit: E&T

Advantage of sticking with liquid fuels

It seems to me that there are three elephants in the room concerning the move to electric road transport: operational range, time taken to refuel, and generating infrastructure. I have yet to see any sensible writings on these topics, meaning that we are living in hope.

The move to electric road transport is a classic error made by well-meaning politicians who prescribed the solution rather than the outcome. The whole world is geared up around liquid fuels, and whilst the whole world is also electrified, there are several inherent advantages of liquid fuels over electricity, mostly to do with existing infrastructure.

There is no storage capability in manufacturing electricity. Consequently its production must be dimensioned to meet peak demand – and large-scale fast charging means big peak demand.

By contrast, liquid fuels are stored by the manufacturer at source and in the distribution network, so a substantial peak-to-average demand ratio can be accommodated and the manufacturing dimensioned appropriately.

Liquid fuels have a bad press because they are instantly associated with oil, and to regain control of the climate, we must stop plundering the planet for oil. However, we are quite happy plundering the planet for lithium – it’s new, it’s shiny and it’s the future!

There would be much sense in devoting some R&D into ecologically acceptable liquid fuels.

Roger Wilkins FIET

By email

EV ownership must be simpler

There are a couple of key areas around electric cars which, as an owner of a Kia e-Niro for the past year, I can state with confidence need to be addressed.

The first is the engineering competence of the firms that have sprung up to provide home chargers. I won’t name the firm responsible for providing mine; suffice to say it took six months from the first visit to get a fully working system. Some of this time was due to a problem with our electricity supply but the majority was due to a lack of defined processes and the inexperience of the installers.

I suspect that because of the significant increase in demand for these systems, the suppliers are growing too quickly and the installers are not being properly trained. As we all know, in the long term this is not a good approach as it leads to repeat visits and significant customer dissatisfaction.

The second is the engineering competence of manufacturers. For the first eight months, I could not have been more delighted with my new car. Then, the projected miles for a full charge started to drop from a regular 250+ to 150. I gave the car to the local dealership on 12 April and got it back ten weeks later. There was a fault with a battery module. Kia had no spares in the UK or EU so had to get one manufactured and delivered from South Korea. This is not competent supply chain management.

In the 40 years since I started driving, I have owned numerous vehicles of varying quality. Six months ago, I was comparing my e-Niro favourably to the best. As a result of this one issue, in the first year of ownership, my e-Niro has now been off the road for longer than the total combined garage time of all the other cars I have ever owned.

Had I known in advance how difficult it would be to get to the point where I had a reliable car and home-charging source, I wouldn’t have gone down this route. At the same time as I was trying to sort out the car and the charging I was renovating a house. The renovation was a lot less stressful.

For electric vehicles to become truly accessible and attractive for all, the whole process of owning them needs to be easy, or at least comparable with other options. At present, it isn’t.

Andy Leslie CEng MIET

By email

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