5. Energy Services and Efficiency Improvement

Energy Services

Except in the form of food, no one needs or wants energy as such. That is to say, no one wants to eat coal or uranium, drink oil, breathe natural gas or be directly connected to an electricity supply. What people want is energy services – those services which energy uniquely can provide. Principally, these are: heat, for warming rooms, for washing and for processing materials; lighting, both interior and exterior; motive power, for a myriad of uses from pumping fluids to lifting elevators to driving vehicles; and power for electronic communications and computing.

When Thomas Edison set up the world’s first electric power station in New York in 1882, it was not electricity he sold, but light. He provided the electricity and light bulbs, and charged his customers for the service of illumination. This meant he had a strong incentive to generate and distribute electricity as efficiently as possible, and to install light bulbs that were as efficient and long-lasting as possible.

Figure 1.39 Dynamo Room of Edison's Electric Lighting Station, Pearl Street, New York, 1882

Unfortunately, the early Edison approach did not survive, and the regulatory regime under which most utilities operate today simply rewards them for selling as much energy as possible, irrespective of the efficiency with which it is used or the longevity of the appliances using it. In a few countries, however, governments have changed the way energy utilities are regulated by setting up mechanisms to reward them for providing energy services rather than mere energy. In this case, customers benefit by having lower overall costs, the utility makes as much profit as before, and the environment benefits through reduced energy wastage and the emission of fewer pollutants.

Linking Supply and Demand

But apart from these relatively few enlightened examples, the efficiency with which humanity currently uses its energy sources is generally extremely low. At present, only about one-third of the energy content of the fuel the world uses emerges as ‘useful’ energy, at the end of the long supply chains we have established to connect our coal and uranium mines, our oil and gas wells, with our energy-related needs for warmth, light, motion, communication, etc.

Figure 1.40 An example of one of the energy ‘chains’ linking primary energy with delivered energy and useful energy, via various energy transformations
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The remaining two-thirds usually disappears into the environment in the form of ‘waste’ heat. One of the reasons for our continuing inefficiency in energy use is that energy has been steadily reducing in price, in real terms, over the past 100 years.

Figure 1.41 Average household rates for US electricity, 1900–2000, expressed in real terms, i.e. taking into account the effects of inflation (source: Smil, 2000)
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Energy’s decreasing cost means that our society has only a relatively-weak financial incentive to use it more wisely.

The chains that link energy supplies with users’ demands are lengthy and complex, as Figure 1.40 illustrates. Each link in the chain involves converting energy from one form or another, for example in the burning of coal to generate electricity; or distributing energy via some kind of transmission link or network, such as a national electricity grid or gas pipeline infrastructure.

Energy efficiency improvements

Supply-Side Measures

On the supply side of our energy systems, there is a very large potential for improving the efficiency of electricity generation by introducing new technologies that are more efficient than older power plant. The efficiency of a power plant is the percentage of the energy content of the fuel input that is converted into electricity output over a given time period. Since the early days of electricity production, power plant efficiency has been improving steadily. The most advanced form of fossil-fuelled power plant now available is the Combined Cycle Gas Turbine (CCGT).

CCGTs are more than 50% efficient, compared with the older steam turbine power plant that is still in widespread use, where the efficiency is only about 30%, and thus two-thirds of the energy content of the input fuel is wasted in the form of heat, usually dumped to the atmosphere via cooling towers.

Figure 1.42 Diagram comparing the operation of a simple gas turbine power plant (a) with that of a combined cycle gas turbine plant (b). In the latter, the hot exhaust gases from the gas turbine are used to raise steam to power a steam turbine. The steam turbine and gas turbine are coupled to a generator to produce electricity. In a conventional, steam turbine-only power plant, the heat required to produce the steam comes from a boiler
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CCGTs are more ‘climate friendly’ than older, coal-fired steam turbine plant, not only because they are more efficient but also because they burn natural gas, which on combustion emits about 40% less CO₂ than coal per unit of energy generated. Overall, taking into account both the higher efficiency and natural gas’s lower CO₂ emissions, when compared with traditional coal-fired plant CCGT-based power plants release about half as much CO₂ per unit of electricity produced. Most of the reductions that occurred in Britain’s CO₂ emissions during the 1990s were due to the so-called ‘dash for gas’ as a substitute for coal in power generation.

Figure 1.43 This combined-cycle gas turbine power station at Deeside in the UK was commissioned in 1994 and has an output of 500 MW

Figure 1.44 This coal fired power station at Didcot, Oxfordshire, UK, was commissioned in 1972 and has a capacity of 2000 MW. Two-thirds of the energy content of the fuel burned in such power stations is dissipated by the cooling towers to the atmosphere in the form of steam

In some countries, the ‘waste’ heat from power stations is widely used in district heating schemes to heat buildings. In 2000, some 72% of Denmark’s electricity was produced in such ‘Combined Heat and Power’ systems.

After fuels have been converted to electricity, whether in CCGTs or steam turbine only plant, further losses occur in the wires of the transmission and distribution systems that convey the electricity to customers. In the UK, these amount to around 8%. Overall, this means that even when a modern, high-efficiency CCGT is the electricity generator, less than half the energy in its input fuel emerges as electricity at the customers’ sockets. In the case of older power stations the figure is around one-quarter.

Clearly, there is room for further improvements in the supply-side efficiency of our electricity systems, by further increasing the efficiency of generating plant and by ensuring the whatever ‘waste’ heat remains is piped to where it can be used.

Coal, oil and gas, when they are used directly rather than for electricity generation, are also subjected to processing, refining and cleaning before being distributed to customers. Some energy is also lost in their distribution, for example in the fuel used by road tankers or the electricity used to pump gas or oil through pipelines. However, these losses are much lower, typically less than 10% overall. This means that over 90% of the energy content of coal, oil and gas, if used directly, is available to customers at the end of the processing and distribution chain. The scope for further supply-side efficiency improvements is obviously much more limited here than in the case of electricity.

Demand-Side Efficiency improvements

Let us now look briefly at what can done to improve the efficiency of energy use at the demand side – that is, in our buildings, industries and vehicles.

Improving the sustainability of energy use by applying demand-side measures involves two distinct approaches, one technological, the other social.

The technological approach involves installing improved energy conversion (or distribution) technologies that require less input energy to achieve a given level of useful energy output or energy service.

The social approach involves re-arranging our lifestyles, individually and collectively, in minor or perhaps major ways, in order to ensure that the energy required to perform a given service is reduced in comparison with other ways of supplying that service.

For example, you may live in a densely populated town with shops, offices, schools and other amenities scattered evenly around. You may be able to do your shopping, go to work, and take the children to school without using a car, simply by walking relatively short distances. Or you may find it convenient to catch a bus, as bus services are usually more frequent and efficient in higher-density settlements.

On the other hand, you may live in a town with a similar population, but one that has been designed (as have many new towns) to have a low population density (i.e. fewer residents per hectare of land), with shops and offices concentrated in the town centre. In this case, you may well use a car for many of your local journeys, consuming fossil fuels and generating emissions of greenhouse gases and other pollutants. In both towns, the residents receive exactly the same levels of service: shopping, working, schooling etc. But in the high-density town the residents can use energy services more sustainably than in the low-density town – all other things being equal.

Figure 1.45 UK delivered energy, 1970 and 2000, by Sector. Between 1970 and 2000, overall delivered energy use rose by just under 10%. Transport energy use rose by 79%, while energy use in the domestic and services sectors rose by 16% and 8% respectively. Industrial consumption, by contrast, fell by 47% over the 30 year period
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In Government energy statistics, energy demand is usually broken down into four main sectors:

The Domestic Sector

This obviously consists of individual households, within which the main categories of energy use are for space heating, water heating, cooking, lighting and other electrical appliances.

The Commercial and Institutional Sector

(often termed the Services Sector). This consists of offices, shops, schools, hospitals, banks etc. The energy requirements of this sector are very similar to those of the domestic sector: space heating, water heating, cooking, lights and appliances. Air conditioning, however, is more prevalent in this sector than in the domestic sector – at least in countries with temperate climates, like the UK. In this sector, as in the Domestic sector, most of consumption is within buildings.

The main technological measures that can be taken to conserve energy and use it more efficiently within buildings include:

• improved levels of insulation in walls, roofs and floors, to reduce heat losses through these elements;

• energy-efficient windows, designed to allow less heat to escape whilst still admitting large amounts of sunlight;

• draught-proofing and heat recovery systems to reduce hear lost through ventilation whilst retaining sufficient fresh air within the building;

• more efficient boilers that require a smaller fuel input to achieve a given level of space or water heating, together with improved insulation of pipes to reduce heat losses;

• energy-efficient lights that require much smaller amounts of power to provide a given level of illumination;

• energy-efficient appliances, such as refrigerators, cookers, washing machines, dishwashers, TV sets and hi-fi equipment in the domestic sector; or more efficient computers, copiers and other business equipment in the commercial and institutional sector. These consume less energy whilst delivering the same level of service as their inefficient predecessors;

• improved control systems, to ensure that energy-consuming equipment is not switched on when not needed, and that power output levels match the requirements of users.

Figures 1.46 Energy-efficient appliances: fluorescent light-bulb and energy-efficient refrigerator

Figure 1.47 This supermarket in London is designed to use half the electricity of a conventional new food store

Figure 1.48 This building at the University of East Anglia consumes less than half the energy of an air-conditioned building of comparable size and function

The Industrial Sector

This sector mainly covers manufacturing industry, service industries being categorized under ‘Services’. Much of industrial energy use also occurs within buildings, and consists of requirements for space heating, water heating, cooking, lights and appliances, as in the Domestic and Commercial & Institutional Sectors. But in addition, many industries, such as the steel industry, use substantial quantities of high temperature heat and large amounts of electricity to power various specialized processes. These demands in many cases exceed those of the buildings where the activities are housed and of the people within them.

So apart from improving the energy efficiency of the buildings and appliances in the industrial sector, where the approaches are similar to those in the domestic and services sectors, there are other measures that apply specifically to industry. In particular, these include ‘cascading’ of energy uses, where ‘waste’ heat from a high-temperature process is used to provide energy for lower temperature processes; and the use of high-efficiency electric motors, pumps, fans and drive systems, with accurate matching of motors to the tasks they are required to perform, and accurate sizing of pipes and their associated pumps.

Dematerialization

The measures that can be adopted by industry also include reductions in the material content of products, for example in car bodies or drinks cans, where thinner metals can be used without any reduction in the required strength; or the substitution of less energy-intensive materials, as in the use of plastics instead of steel for car bumpers.

These measures are one form of what has been termed ‘dematerialization’ – a reduction in the material-intensity (and hence the energy-intensity) of production.

Another form of dematerialization involves changes that are more social than technological. It occurs when the structure of a country’s entire economy shifts towards less energy- and materials-intensive activities. For example, in the UK the steel industry today accounts for a much smaller share of the country’s domestic product (GDP) than it did 20 years ago. By contrast, the UK services sector now constitutes a much bigger fraction of GDP than two decades ago. Since the service sector usually requires less energy than the steel industry for every pound’s worth of production, Britain’s overall energy demands have been less than they would otherwise have been. However, if the steel that was formerly manufactured in Britain is now manufactured abroad but still imported to the UK in similar quantities, all that has happened is that the energy input, with its associated CO₂ emissions and their implications for global warming, has been transferred to another country.

The Transport Sector

Motor vehicles (cars, vans, buses, trucks, motor cycles) dominate the transport sector in developed countries. But this sector also encompasses many other modes of transport, including rail, air and shipping, and non-motorized transport forms such as cycling and walking.

As can be seen from Figure 1.49, the various forms of transport vary enormously in their energy requirements per passenger-kilometre travelled. Cycling and walking, of course, require no fuel input apart from food.

In most developed countries there has been an enormous increase in transportation, measured in passenger-kilometres travelled annually, over the past few decades (Figure 1.50). Most of this has involved motorized transport, mainly fuelled by oil, and so energy use has also increased greatly, as have the associated CO₂ emissions.

Figure 1.49 Energy efficiency of different modes of transport in the UK (source: Hughes, 1993)
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Figure 1.50 Annual passenger-kilometres travelled in the UK, 1952–2000, by transport mode. Note: air travel data refers to internal flights only (source: DTLR, 2001)
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Transport Energy Demand Reduction: Social Measures

Clearly, one social way of reducing the energy required by the transport sector is to shift a proportion of people’s journeys away from the energy-intensive modes and towards the more energy-frugal modes. This process is sometimes termed ‘modal shift’.

This could be achieved without reducing the total number of journeys, or the overall distance travelled, so that the amenity or service enjoyed by the traveller would remain the same. If, for example, a greater proportion of long-distance journeys within Europe were made by inter-city train rather than by air, the overall energy demand involved could be reduced substantially. Or if urban commuters made more journeys to work by rail or bus instead of using their cars, the effects would be similar. And if householders walked to their local shops instead of taking their cars, no fossil fuels at all would be used for those journeys. Of course, if people are to undertake transport modal shifts of these kinds, they will need to be encouraged by fast, comfortable, efficient services – or penalized into switching by such measures as congestion charging, which is being implemented in central London and other major cities.

Transport Energy Demand Reduction: Technological Measures

In addition to such social measures, there are numerous technological options for improving the energy-efficiency of transport energy use. Improving vehicle fuel economy is one obvious measure, and the average fuel economy (in miles per gallon, or litres per 100 km) of vehicles has indeed improved very substantially in most developed countries over the past few decades. However, this improvement has been largely offset (in the UK at least) by an increase in the total number of vehicle-miles travelled, and by increases in the average speeds of vehicles, both of which result in increased fuel consumption.

Nevertheless, manufacturers continue to introduce new models with steadily improving fuel economy, partially spurred by legislation requiring them to do so. New approaches include ‘hybrid’ petrol-electric cars such as the Toyota Prius (Figure 1.51).

Figure 1.51 The Toyota Prius, a ‘hybrid’ petrol-electric car

In addition to such incremental improvements, there are also more radical possibilities, such as the ‘hypercar’, proposed by engineers at the Rocky Mountain Institute in the USA (Figure 1.52).

Figure 1.52 The ‘Hypercar’, designed by engineers at the Rocky Mountain Institute, Colorado, USA, would be streamlined and made of strong but ultra-light, composite materials

This approach involves the use of strong but ultra-lightweight composite materials such as carbon fibre or Kevlar, combined with a highly streamlined body shell. The drive system is would either be of the ‘hybrid’ type, consisting of a small gasoline-fuelled engine augmented by electric motors and a small battery store; or a more advanced system employing a fuel cell powered by hydrogen. Fuel cells are rather like conventional batteries, except that they are continuously re-charged by supplying fuel – usually hydrogen gas – that reacts electrolytically with oxygen from the atmosphere to produce an electric current. In the hypercar, the fuel cell would generate electricity for electric motors that provide power to the wheels. The hydrogen fuel would either be stored in tanks in its pure form, or generated on-board by ‘re-forming’ fossil fuels. The oxygen would come from the surrounding atmosphere. Hypercars, their proponents claim, could achieve between three and five time the fuel economy of current models, with emissions levels approaching zero in the case of the hydrogen-fuel cell version.

Hypercars may still be some way off, but major manufacturers such as Daimler-Chrysler and Ford have recognized the need to make dramatic reductions in vehicle CO₂ emissions in the long term, and are investing many hundreds of millions of dollars in the production of fuel-celled vehicles (Figure 1.53).

Figure 1.53 This Mercedes A-Class car is powered by a fuel cell running on hydrogen. The manufacturers, Daimler-Chrysler, and other car-makers such as Ford and General Motors, have announced plans to introduce similar cars on the market around 2004

The Rebound Effect

When individuals or organizations implement energy efficiency improvements, they usually save money as well as saving energy. However, if the money saved is then spent on higher standards of service, or additional energy-consuming activities that would not have otherwise been undertaken, then some or all of the energy savings may be eliminated. This tendency is sometimes known as the ‘rebound effect’. For example, if householders install improved insulation or a more efficient heating boiler, they should in principle reduce their heating bills. However, if they instead maintain their homes at a higher temperature than before, or heat them for longer periods, the savings may be wholly or partly negated. Alternatively, they may decide to spend the money saved through lower heating bills by taking a holiday involving air travel. Since air travel is quite energy-intensive (see Figure 1.49) once again the energy savings will be offset by increased consumption, albeit of a different kind.

In devising national policies to encourage energy efficiency improvement, Governments need to take the rebound effect into consideration. In some cases, it may mean that the energy savings actually achieved when energy efficiency measures are implemented are less than expected. Another policy implication is that citizens should be given incentives to spend any savings they make through implementing energy efficiency measures in ways that are energy-frugal rather than energy-intensive.

Next: 6. Energy in a Sustainable Future