Energy and Transport

Transport is one of the big consumers of energy. As we have seen in some of my previous posts, there is a clear tendency to become more energy efficient. Does this also apply to energy used for transport purposes?

Eurostat provides a collection of data on this issue which may give us an answer.  Let us look at the transport energy per unit of GDP. This is certainly a sensible measure since we may consider a link between economic activity on the one hand and transport (of both people and goods) on the other. So whenever the economy is growing (or shrinking) transport is likely to follow suit.

We consider here the case of Germany, France and UK, i.e. the biggest economies of Europe. The figure below shows how energy demand for transport per unit of GDP has developed since 1995. The curves are indexed with 2005 = 100.

Energy demand for transport purposes per unit of GDP.

The message behind this figure seems to be obvious. Over the past 15 years there has been a certain decoupling of economic performance and energy demand for both passenger and goods transport. Thus per unit of GDP less energy is used for transport. We are becoming more energy efficient.

Having a closer look at the figure we may also observe that the downward trend is still unbroken, i.e. there is no flattening tendency. This leads us to the conclusion that there is room for further improvement of energy efficiency in the transport sector.

Do Energy Saving Light Bulbs Really Save Energy?

Some considerations about the usefulness of energy saving light bulbs.

Conventional light bulbs which are now banned in the EU since 1st September 2012 are very inefficient when it comes to turning electrical energy into visible light. More than 90 % of the energy input are emitted in the form of heat. Thus with a less than 10 % efficiency in terms of light production the classical light bulb may indeed look a rather hopeless case and energy saving lamps appear to be the preferable choice.

However, a closer inspection shows that the odds are not at all so bad for the conventional lighting medium. During the cold season, i.e. whenever people feel the need of switching on their heating, the classical light bulb contributes to the heating effort. Thus whenever we count heading degree days the old fashioned light bulb lowers the need to switch on the heating. From a physical point of view during the heating period the energy saving light bulb does not save energy. That is a simple deduction from the law of energy conservation. On the contrary, if we turn to energy saving lamps, the work load of our heating systems gets higher.

On the other hand, it is true that during the warmer period energy saving light bulbs are the better choice because then we really do not need any extra heating. So in order to understand the energy balance of both lighting systems we developed a model which is based on the following assumptions:

Get-up time: 6:00

Leaving home in the morning: 8:00

Returning home in the evening: 17:00

Sleepy time:  24:00

In addition to that we assume an average performance of 200 W(el). Our model is then applied to two European cities, one in the northern (Stockholm) and the other in the southern part (Rome). From this model it follows that the maximum number of lighting hours per day is 9 which is reached during the dark winter months. On the other hand, during the long daylight hours in summer, it may be necessary to switch on the light for no more than 2 hours per day. Electricity consumption for light sources is thus fluctuating between those two extremes. Fig. 1 shows the distribution of lighting hours in both cities.

Fig. 1 Lighting hours in Rome and Stockholm.

How much artificial light we actually need is largely determined by the length of the daylight period which in turn is governed by sunrise and sunset.  The data for those astronomical observables are easily accessible, clearly highlighting the differences between northern and southern locations. Although these differences may be very large during certain periods of the year, their overall impact on our model is far less dramatic than expected. On an annual basis the number of lighting hours in Stockholm is not very much different from the one in Rome, 2160 vs. 2110, respectively, i.e. less than 3 percent difference. These lighting hours correspond to an average electricity consumption of 432 kWh and 423 kWh, respectively.

Lighting and heating

What is, however, different is the number of heating degree days between the two cities. Correspondingly, the number of lighting hours during the heating period is much larger in northern Europe than in the southern part. Our analysis shows that more than 80 % of lighting hours are consumed during the heating period in the case of Stockholm. This, in turn, means that during that period there is no gain from using energy saving light bulbs. The respective number for Rome is 62 %. Thus also in southern Europe a substantial amount of lighting is used when people are likely to put on their heating. The rest of Europe lies, in its vast majority, somewhere between these two extreme values. There are exceptions, but these are statistically insignificant.

From a physical point of view, energy saving lamps are only useful when it is warm outside, because then there is no need for excessive heat. During winter those lamps do not lead to an overall reduction of energy consumption. Let us look at the situation from the point of view of a classical light bulb. It wastes energy in summer, but not in winter. According to our model, the waste energy produced by a classical lighting system amounts to about 78 kWh (Stockholm) and 145 kWh (Rome), respectively, over the whole year. We may also ask how much heating energy we can save by using normal light bulbs. The figures are 311 kWh (S) and 235 kWh (R), respectively. Thus we may conclude that, physically speaking, the energy balance of classical light bulbs is clearly better than the one of their energy saving competitors. Their contribution to heating in winter outweighs their waste of energy in summer. Of course, the effect is much more pronounced in northern Europe than in the southern countries. But even in the latter ones, the result is undoubtedly in favour of normal light bulbs. Figs. 2 and 3 demonstrate the contribution to heating and the waste energy of conventional light bulbs for the two cities.

Fig. 2 Heating potential vs waste energy of conventional light bulbs in Stockholm.

Fig. 3 Heating potential vs. waste energy of conventional light bulbs in Rome.

It is, of course, conceivable that under certain circumstances energy saving light bulbs live up to their expectations. Our model indicates that this may be the case in tropical areas where heating is hardly ever needed.

In any case, energy-saving lighting systems are not reducing energy consumption at the level of private consumption which we have considered inour model. This is even less so at a more general level, when taking into account the energy effort for producing and disposing of light bulbs. The recycling of energy saving systems is putting an extra burden on their overall energy balance, therby seriously questioning their high expectations.

Energy Efficiency in Austria

In a recent posting we had a closer look at the development of energy efficiency in the UK. Then we found that various sectors of the economy have been performing differently over the years. Some sectors managed to lower their energy hunger drastically, while others were much less successful.

Now we are going to look at the situation in Austria. There, too, has been much talk about the need to save energy. But how much of that has actually materialized into lower consumption or, to put if differently, higher efficiency? The Austrian statistical office, Statistik Austria, provides data on various sectors. We were particularly interested in the following areas: industry, domestic consumption and passenger transport.

Fig. 1 gives an overview of the energy efficiency of those sectors between 1990 and 2010. The figures are indexed with 1990=100, and the individual graphs refer to the following quantities: industry means industrial consumption per unit of output, domestic total refes to consumption per household, and passenger transport stands for energy use per passenger-km.

Fig. 1 Energy efficiency in Austria. For detailed explanations see text.

What do these graphs tell us? The clearest message stems from passenger transport showing a significant decrease since 1990 (83 index points in 2010). That is considerably more than what we have found in the UK. It seems that the Austrian car fleet is more modern than the one in UK.

Domestic consumption also tends to become less, though at a much more moderate pace (94 in 2010). It should be noted that those data have not been corrected for temperature effects which can lead to varying energy demand during the winter months. Industry consumption, too, tends to go down over the years, however, with strong fluctuations. During the economic crisis efficiency seemed to improve a lot (87 in 2008/09). Strangely, during the recovery in 2009 it appears to have become less important and its index rose to 1990 levels (101). After that production efficiency has improved again.

We may also have a closer look at domestic consumption. To that end we split up that sector into heating (including airconditioning) and other uses. The results are shown in Fig. 2.

Fig. 2 Domestic energy use per household. 1990=100.

This figure requires some detailed analysis. First, we note that the graphs for heating and total domestic use are roughly in line with each other. This does not come as a surprise since heating accounts for about 75% of total household energy demand. This dominance tends to cover the huge variations of other consumers of household energy (lighting, kitchen equipment etc.) which do not contribute to the overall trend. On the contrary, other domestic uses reached more than 123 index points in 2003 before a gradual downturn set in. At the end of our observation period we have reached the same levels as in the beginning. That is not what we call a success story.

Comparing efficiency figures between different countries is both interesting and enlightening. Nevertheless we should be cautious in interpreting the figures even if they are presented in an indexed form. If country A does very much better than country B it does not necessarily mean that at the end of the day A is more energy efficient than B. That would only be true if both countries started from the same or at least similar levels of absolute efficiency. However, if B was already more efficient than A in the beginning in absolute terms, then, clearly, B needs to make much more effort than A in order to come down by the same number of index points.

Now what do we mean by efficiency in absolute terms? It is not sufficient to consider energy consumption per output only, but one has to make sure to be talking about the same amount of output for each country. Thus, if we have GWh/EUR for one country and GWh/GBP for the other we have to make sure that the two currencies are put into relation. We first have to put both countries on the same footing and then are we in a position to analyse their relative performance. In that way, comparing energy efficiency between different countries can be put on a solid basis.


Efficiency vs. Effectiveness – towards sustainable cities

An important concept in this discussion is exergy, or the quality of energy. This follows from the ‘laws of thermodynamics’. The first law states that energy can never be lost, that it will remain. The second law introduces the notion of quality: although energy cannot be lost it loses quality and entropy is created when used (google for exergy and ‘laws of thermodynamics’ to learn more).

Using resources – energy, water, materials, etc. – in an efficient way means using these resources while trying to limit waste, trying to do things in the right manner. The concept of ‘Trias Energetica’ will be used to explain and some examples will be given. Trias Energetica was developed by Lysen and Duijvestein (1997). It consists of three, consecutive steps:

  1. Limit energy demand and energy use;
  2. Use renewable energy sources;
  3. Use fossil fuels as efficiently and cleanly as possible to fulfill remaining demand.

The first step is the most important, because each amount of energy that is saved does not have to be produced. An example of this first step is to insulate dwellings properly so less energy is needed to heat the dwellings. Remaining demand should be fulfilled by applying renewable energy sources, like solar or wind. The third step talks about the efficient use of fossil fuels. For example, the introduction of fuel-efficient cars or even hybrid cars. These cars still need fossil resources, but they use these resources more efficiently, see graph 1.

Graph 1: Fuel-efficiency of some car types, gasoline use

It is important when looking at efficiency and energy-saving measures that they do not result in a rebound effect. So, e.g., changing non-efficient light bulbs with efficient ones (LED, fluorescent light bulbs) is a good measure. The pitfall though is that people leave the lights on, because they know it is more efficient, so they think that it does not matter. This results in the end in more energy use anyway.

For a true sustainable system, the Trias Energetica should be adapted. Measures to save energy may not result in loss of comfort or health problems. A system can only be sustainable if it uses renewable resources. The rate in which we use fossil fuels, is not renewable. The resources of oil, coal and gas are not regrowing. Another point to consider: is it nowadays cheaper to invest in more insulation or to invest in renewable energy production systems? The importance of re-use, re-cycle and manufacturing, keeping the end of products in mind, is also growing. Therefore, a new concept has been developed ‘the New Stepped Strategy’ (Dobbelsteen and Tillie, 2009). In this strategy, the last step is replaced:

1.   Reduce consumption without loss of comfort and health;

2a.  Exchange and re-use waste energy systems;

2b.  Use renewable energy sources and ensure waste is re-used as food.

Applying those steps to a city or region towards sustainability can be seen as a sign of effectiveness. This means trying to use resources in the right way, trying to reach the result, to do the right things. Think with the result or purpose in mind and do not start from the means. For example, do you need your laundry cleaned or do we need the best, most energy-efficient laundry machine to clean our clothes? The question is ‘what is the most resource effective way to clean our clothes’ (we can come back to that another time)?

Reduce consumption still is the most important step. The New Stepped Strategy introduces also the importance of different scales, from dwelling level to neighborhood to city level. Before a decision is made, it has to be studied what is the most effective step to take at which level. Some things can be arranged very effectively at dwelling scale, like insulation, but others will be more effective at a larger scale, like cascading remaining qualities. An example is the remaining heat of a power plant or industry. Nowadays, it will be the remains after fossil fuel burning, but in the future it may well be the remains of renewable fuel burning or use. The idea is that the remaining heat of this industry is not a waste product, but can still be useful for another purpose. For example as processing heat for an industrial facility that needs only heat of lower temperatures. After use in this industry, it still has some heat quality remaining that can be used in, e.g. green houses. A last step can be heating of houses that needs only  a low energy (in the form of heat) quality, see graph 2.

Graph 2: Example of a heat cascade in an urban system

So, in order to reach sustainable cities, it is important to reduce energy consumption and to apply the local available renewable and residual resources in an effective way. The urban metabolism has to evolve to a circular metabolism in which any waste product is seen as a remaining quality that can be used by another function within the city. This will decrease dependency on foreign resources. It will increase the search for local potentials and characteristics. Cities are multi-functional entities. The different functions should and need to be connected and in close proximity to effectively use the local potentials towards sustainable cities.

Wouter Leduc


Dobbelsteen, A., van den, Tillie, N., 2009. Towards CO2-neutral Urban Planning: Presenting the Rotterdam Energy Approach and Planning (REAP). Journal of Green Building, 4.

Duijvestein, C.A.J., 1997. Drie Stappen Strategie. In editors D.W., Dicke, E.M., Haas, Praktijkhandboek Duurzaam Bouwen. WEKA, Amsterdam, pp. (20) 1-10.

Energy Efficiency – A Sectorial Approach

Becoming more energy-efficient is one of the major challenges of our time. Modern societies are highly energy-dependent and thus all efforts to save this valuable resource are more than welcome. For many years, or rather decades, the responsible people, politicians and experts, have urged the importance of using less energy.

We may ask ourselves what has been achieved so far. We may equally ponder about future developments. How much more can we save?

In this posting we investigate the achievements of getting more energy-efficient in the UK from a sectorial point of view. The country can serve as a typical example of a European state trying to do both, using less energy for the same economic outcome and reinforcing its potential of renewable energies. The raw data for our analysis have been taken from UK National Statistics.

We consider the following sectors: Industry, domestic, services, passenger transport and freight transport. The energy consumption of the various sectors is measured as follows: industry (Mtoe/unit of output), domestic (Mtoe/household), services (Mtoe/unit of value added), passenger transport (Mtoe/person-km), freight transport (Mtoe/tonne-km). The transport sectors cover road transport only. In order to see how well each sector is doing compared to the others, we have indexed the quantities as 1980=100.  The results is given in the figure below.

Energy efficiency in the UK for various sectors.

This picture reveals immediately who the good and the bad guys are. Let´s start with the good ones. Both industry and services managed to reduced their energy use per unit of output considerably. In fact, in 2010 British industry was able to produce more than twice as many goods per unit of energy as in 1980. Within 30 years the index went down to less than 48. The services sector was even more successful. During the same period its specific consumption plummeted to an index value of 43 only.

The situation looks quite a bit different for the other sectors with passenger transport being the most successful among those. Since 1980 the use of energy per passenger-km has decreased by almost 20 % (index 81.9). Unfortunately, freight transport cannot compete with that value. Instead its energy consumption per tonne-km went up by almost 12 % during the reference period. This finding is both, surprising and disappointing at the same time. Surprising, because car producers make us believe that modern vehicles need less gasoline than older ones. Disappointing, because freight transport is the only sector showing a clear increase in its energy hunger.

When looking at the figures for household consumption we may equally feel disappointed. There is a slight tendency to use less energy per household, with the index being at 93 in 2010. This is a rather weak performance when compared to the other sectors with the notable exception of freight transport. Countless public campagnes have been run with the clear goal of getting more energy efficient. It is hard to imagine that millions of households have not got the message. However, the results are meagre. Why is that so? Is there too little incentive for households to save energy?

Household Energy Use – The Case of Switzerland

Modern societies need a considerable amount of energy, which is almost entirely used the three sectors industry (including services), mobility and household, at roughly equal parts. Thus, the energy consumed at home forms a substantial part of the entire final energy use.

In this posting we study the situation in Switzerland which is one of the most competitive and industrialized countries of Europe, though not being a member of the EU. All raw data for the subsequent investigation stem from Swiss Statistics which provides excellent information on all areas of consumption. In particular, we will focus on the period 2000-2010. The above-mentioned sectors had the following shares in the total final energy consumption in 2010: industry and services 35 %, mobility 34 % and household 30 %.

Total household energy use went up by 14.1% during the first decade of this century. However, this obvious increase does not take into account that the number of people living in Switzerland has also risen during that period. Thus, the relevant figure to look at is the consumption per capita, and here the situation looks quite different as can be seen in Fig. 1.

The trend line makes clear that the specific energy use per person has gone down over the years. The steep increase since 2007 is well in line with the number of heating degree days (HDD) following a similar pattern as can be seen in Fig. 2. Apparently, it has become colder between 2007 and 2010.

Fig. 2 Heating degree days (HDD) and heating effort in Swiss households.

The similarity between the red curves in Figs. 1 and 2 is not accidental, as more than 72 % of total household energy are used for heating purposes (in 2010). Thus, changes in the number of heating degree days should be reflected in the heating effort. Warm water makes up for another 12 % of household use while the remaining 16 % are shared among various sectors such as lighting, cooking, washing, drying, etc.

A closer look at the figures for warm water reveals that consumption has remained relatively stable (Fig. 3).  Taking into account the growing number of households (+ 11 %) during the period in question naturally leads to the conclusion that each household uses less and less warm water.

Fig. 3 Total energy used for warm water and consumption per household (/HH).

Fig. 4 shows the contribution of other sources of household energy use. Their aggregated consumption volume is relatively moderate as stated above. Nevertheless, as a whole they are not to be neglected although their individual shares are not as important as the ones for heating and warm water.

Fig. 4 Household energy use (except heating and warm water).

Whereas lighting, cooking and refrigerating (including freezing) have remained virtually unchanged over the years, washing (including drying) and miscellaneous have increased dramatically by 52 % and 32 %, respectively. This is well in line with a growing population as more people require more clothing to be washed. So there are some areas of energy consumption being more sensitive to the number of persons involved while others like lighting tend to be rather independent of population figures.

Thus, as stated in my previous posting, growing energy consumption figures (in absolute terms) should not be obscured by ignoring the simultaneous changes in the number of consumers. On an individual basis, we gradually tend to use less energy. This is the good news. But, of course, the crucial question is how much further we can get in becoming more energy efficient. Or, to put it differently, is there a limit and, if yes, where is it?

Energy Efficiency – How Europe Can Achieve Its 2020 Targets

Becoming more energy efficient is perhaps the most straightforward and least expensive way of tackling the energy problem. Recently, the EU has addressed this issue within the framework of the so-called Europe 2020 targets which aim at reducing gross energy consumption by 20 %, producing at least 20 % of all energy from renewable sources and reducing greenhouse gas emissions by 20 % (with respect to 1990 levels). All that is supposed to be attained by 2020 at the latest.

Leaving aside the two latter issues, we will focus in this posting on the question of energy efficiency. Lowering energy consumption by 20% (when compared to projected levels) means in particular that by 2020 Europe will use some 1474 Mtoe (mega-tonnes of oil equivalent) of primary energy.

Fig. 1 shows the development of EU gross inland consumption from 1990 onwards with EU-27 representing the entire union whereas EU-15 refers to the “old” Member States, i.e. excluding those countries which joined the union in 2004 or later.  One striking observation is that during the past two decades consumption figures have always been substantially higher than the 2020 target line. Thus we are facing a real challenge.

Fig.1 EU gross inland consumption of energy. Source: Eurostat.

But looking at absolute consumption levels only does not reveal the whole story since, at the same time, we are also expecting economic growth. And a growing economy means higher energy consumption, at least to some extent. Putting consumption and economic performance together yields another interesting observable, namely the so-called energy intensity which is shown in Fig. 2. This parameter indicates how much energy is needed in order to produce one unit of economic output. Energy intensity is thus measured in kgoe/kEUR (kg of oil equivalent per 1000 EUR). Apparently, this indicator has fallen drastically since 1991.  In 2010 it was at 168 kgoe/kEUR for EU-27.

Fig. 2 EU energy intensity. Source: Eurostat.

One apparent feature of this figure is that the gap in the intensity levels between EU-27 and EU-15 is getting smaller over the years, thus indicating that the countries which joined the EU in 2004 or later are outperforming the older Member States (EU-15) when it comes to becoming more energy efficient. Nevertheless, the energy intensity of the younger EU members is still considerably above average.

Reducing absolute energy consumption means that intensity figures will drop accordingly. But by how much? In order to obtain an answer to this question, we analysed two scenarios, one with a stagnant economy, i.e. no (real) GDP growth up till 2020, and another one with an average GDP increase of 2 % annually.

Taking the zero-increase economy as a reference we find that energy intensity must drop from its 2010 level to some 141 kgoe/kEUR in 2020. This is not too far from the current EU-15 level (151 kgoe/kEUR). However, at EU-27 level this means that the intensity has to go down by some -1.75 % on average per year.

Going over to a more dynamic scenario with an average economic growth rate of 2 % we find the respective energy intensity in 2020 at 115.5 kgoe/kEUR. Obviously, the effort is much stronger in this case, requiring an annual decrease of almost -3.7 %.

To put things into perspective we may mention that the average intensity gain during the period 1991-2010 was 1.94 % per year. Thus, the prospect of performing equally well in a no-growth economy does indeed look quite promising. However, once the economy is supposed to grow even at a moderate pace, our effort may easily double.  In that case, more drastic measures are required in order to attain the ambitious goal.

Energy Efficiency – Potential Household Savings in Sweden

In a recent report we analysed the savings potential of the Swedish housing sector. Sweden has committed herself to save some 12.8 Mtoe of primary energy up to 2020. Taking into account that the country used some 51.4 Mtoe in 2010, and with a consumption goal in 2020 of about 41 Mtoe, this means that savings of some 20 % within the remaining decade are at stake.

One of the biggest savings potentials is supposed to be hidden in the building stock. Household energy use accounts for 23 % of the total final energy consumption in Sweden and the largest part of it is eaten up by heating purposes. In the following we look into the consumption figures for heating and warm water in Swedish households. The raw data for our investigation have been taken from Eurostat, Statistics Sweden and the Swedish Energy Agency.

The average energy consumption in kWh/sqm according to year of construction is distributed as follows:

Fig. 1 Average annual energy consumption for heating and warm water in Sweden.

The latest construction types use significantly less energy per sqm than the older ones. This is in line with our expectations. For single dwellings average consumption has dropped by some 40 % from 153 kWh/sqm to 91 kWh/sqm. For multi-dwellings the decrease was not as dramatic. Nevertheless, average consumption went down from its maximum value of 170 kWh/sqm to 125 kWh/sqm (26 %).

The consumption figures per category are displayed in Fig. 2.

Fig. 2 Energy consumption for heating and warm water by year of construction.

Taking the latest construction technology as a reference, we may calculate how much energy could be saved if the entire building stock was refurbished according to that standard. The results are shown in Fig. 3.

Fig. 3 Calculated savings potential by year of construction.

As regards the single housing sector refurbishing the oldest part of it would account for 50 % of the total savings potential of that sector. Obviously, the younger part of the building stock would only contribute very little (2 %) to the entire potential.  In total, we could expect to save some 9.9 TWh for single dwellings and 5.5 TWh for multi-dwellings. Thus the entire savings potential from the housing sector would amount to 15.4 TWh which corresponds to 24 % of all energy used for heating and warm water.

This is an impressive number although in terms of Mtoe its equivalent is a mere 1.3 Mtoe. Thus we may conclude that renovating the Swedish housing stock would provide savings of about 10 % of the entire reduction goal set by the Swedish government (12.8 Mtoe). Having said that we have to admit that the biggest part of the task is still to be done.