An interactive per-person energy consumption model for Irish citizens - no comprehensive model like it currently exists - throws up some fascinating insights on how we spend our energy and where that energy comes from
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Energy cannot be created or destroyed, we all know that. But despite this simple truth, it is surprisingly difficult to carry out a proper energy audit and find out who uses how much energy for what.

For example, you can easily compute the energy burnt to fuel your car, but it is much more difficult to calculate the energy necessary to build that car in the first place or build the roads on which it runs.

This is further complicated by the fact that much of the energy embedded in the production of the goods we use – cars, clothes, food mixers – is expended in other countries before the goods reach us, making our personal energy usage extremely difficult to quantify. We can all wring our hands about the coal being burnt in China, but how much of that coal is being burnt on our behalf?

This was the question UCD master’s student, Eoin McCormack, under the supervision of lecturers Barry Brophy and David Timoney, set out to answer. He created an interactive per-person energy consumption model for Irish citizens which throws up some fascinating insights on how we spend our energy and where that energy comes from. No comprehensive model like this currently exists.

Surprising findings


The Excel-based model allows you to enter personal details – age, profession, location, residence, mode of transport, holidays and so on – and works out your energy consumption for a given reference year, in this case 2015 as much CSO census data from this year was used. The model then compares your energy use to that of the reference Irish citizen, breaking it down into several subcategories.

For the reference person in the given year, it estimates the total energy consumption to be about 70,000 kWhr, which, from now on, we’ll refer to as 70k for short.

Fig 1: Model interface for entering your personal details.

When you dig into the results, many interesting insights emerge. For example, from the 70k total, the reference person has a residential energy spend of 10.1k. Of this, 3.4k goes on electricity, which equates to 1.5k you will see on the meter, and an additional 1.9k to generate this electricity at an efficiency of 45 per cent. (Note: the generation efficiency of most thermal plants is lower than this figure, but the average electricity generation efficiency is brought up by the inclusion of renewables.)

Compare this to the per-person energy consumed on a flight to North America (average destination city), which results in a fuel energy spend of around 4k. So, your Patrick’s Day long-weekend in Chicago consumes more energy than you would use in electricity in a year.

And to be clear, the electricity energy-spend is not just the electricity registered by your meter, but the total energy required to produce that electricity (in the power station) in the first place.

Food is another significant item. The average person spends 5.6k of energy on what they eat. Many foods may grow on trees but the energy required to farm, transport, refrigerate, process and package them clearly doesn’t.

There is a growing awareness among consumers of the benefits of ‘buying Irish’, but with disproportionally cheap aviation fuel facilitating unnecessary global movement of certain foodstuffs, there are huge energy savings that can be made in this category. The starting point for this change is knowledge and the kind of big picture insights that a model like this offers.

Embedded energy


Another interesting finding relates to the energy embedded in manufactured goods. Each year, the average person purchases clothing with an embedded energy cost of about 5k and consumer goods with an embedded energy cost of 4k.

There are two things to say about figures like this. First, people worry about how much money they spend on clothes – ‘Is this pair of shoes really worth it?’; ‘Do I need a new coat this winter?’ – but they almost certainly don’t worry about how much energy they are spending on these items.

Second, much of the energy embedded in the manufacturing of these goods is added in other countries – China springs to mind – and so doesn’t feature on the Irish energy balance sheet.

Fig 2: The results dashboard from model. Each icon links to a lower-level analysis of that category as shown in Fig 3 below.

This points to how difficult it is to create an all-encompassing national energy consumption model. The problems come when you try to balance energy imports against exports.

This model calculates many of the imports by looking at commercial transactions and converting these to energy by means of energy intensity figures – based on life cycle (LCA) and input-output (IO) analysis – taken from a variety of journals and statistical sources.

However, the exported energy, in goods we ship from the country, is harder to calculate because the same LCA and IO analyses haven’t been carried out for Irish production pathways.

For example, the model looks at per-person energy usage in the workplace. Offices are built, lit, heated and air conditioned, all requiring energy. Energy is also required to get people to and from these offices every day.

But how much of the energy used in the workplace is expended on the workers and how much of it ends up in the products produced? And what about the industries that import stock, add energy, and then export processed goods?

And what if products, or parts of products, cross borders several times during the manufacturing process? There is a danger of double accounting when making these estimates, and although the model makes reasonable, broad assumptions, it is difficult to tie these down.

Fig 3: Breakdown of energy in the food sub-category.

‘We need to look at energy on a global scale’


Creator of the model Eoin McCormack reflects on this. “Doing this work has really shown me the effect that globalism has had on the world. We need to look at energy on a global scale instead of, ‘this is our little box and this is what we use’.

“You’re just brushing the issue under the rug and not taking responsibility for the effects of your own lifestyle and energy consumption. It might seem that industrial nations like China and India are worse than us in terms of energy use, but really they’re just supplying our needs.”

This kind of model is an important first step in the better understanding and wiser use of our declining energy resources.

And the communication component of this work is as important as the model itself, as supervisor Barry Brophy reflects: “The detailed calculation scheme Eoin has put together is very impressive and informative, but it only becomes really useful with the right interface and he has done a great job on that.

“Too often engineers carry out fantastic analysis but give little or no thought to how this can be shared with the wider world. For all the publicity energy and environmental issues get, people are still generally ignorant of how much energy each of us use and for what.

“I teach courses in technical communication and two things I urge students to include in their presentations is visuals and audience interacting. This model has both.

“Visually it is easy to navigate, and being allowed to enter your own details and vary parameters is a great way to get a feel for the numbers. You learn more when you interact with ideas rather than just hearing or reading them.”

In the near future we will have to make hard decisions about energy use, both nationally and internationally. For this, we all need to be aware not just of the financial bottom line but the energy bottom line.

We live in a global energy system, so the ‘divisional accounts’ approach nations have taken in regard to energy is no longer valid.

Author: Barry Brophy, research engineer, UCD School of Mechanical and Materials Engineering

http://www.engineersjournal.ie/wp-content/uploads/2019/01/a-aaaaaen3.jpghttp://www.engineersjournal.ie/wp-content/uploads/2019/01/a-aaaaaen3-300x298.jpgDavid O'RiordanElecelectricity,energy,UCD
Energy cannot be created or destroyed, we all know that. But despite this simple truth, it is surprisingly difficult to carry out a proper energy audit and find out who uses how much energy for what. For example, you can easily compute the energy burnt to fuel your car, but...