Let’s face it: energy efficiency is boring when compared to the (relative) excitement of developing new sources of low-carbon electricity or heat. The popular science magazines are full of articles on new forms of solar panel and the latest designs for wind turbines. Improving the insulation of ordinary homes, shifting to LED lighting or increasing the take-up of heat pumps rarely command the attention of editors.

***

In a breathtakingly elegant paper in Energy Policy, Jonathan Cullen and Julian Allwood of Cambridge University try to persuade us just how wrong we all are.[1] The theme of the paper is that carbon emissions are far more responsive to changes in how we use energy than in how we generate it. They say that it will be cheaper, easier and quicker to make efficiency savings than to switch to renewable electricity or heat.[2] The scale of the loss from the raw energy value of a fossil fuel to its eventual productive use is enormous and the authors argue that cutting this gap is a far easier task than replacing the 50,000 fossil fuel power stations with millions of wind turbines and vast solar power plants strung across deserts to meet our emissions reductions estimates. Are they right? This article uses the Cullen/Allwood paper to look at the total potential saving that might reasonably be obtained in the next couple of decades if we make a determined effort to improve energy efficiency.

My very tentative conclusion is that we can look for a 40% reduction in current energy use if we pursue efficiency objectives enthusiastically. (I don’t look at the impact of economic growth in developing countries and the way this might substantially increase total energy demand.) Perhaps surprisingly, the cost of achieving even a 40% energy efficiency gain looks high to me, particularly compared to the cost of decarbonising electricity generation. Wind turbines probably give a better return on investment.

The background data for the Cullen/Allwood paper is not complex or controversial. The world uses about 475 exajoules a year, all but 100 of which are from fossil sources. Their contribution comes from rigorous quantification of how these energy sources are turned into things that we actually desire. First, the primary sources of useful energy are processed – usually burnt – in a variety of machines, such as a diesel engine or an oil burner. The eventual result is motion, steam, useful heat or cool, and the transformation of materials (turning ore into metal, for example). These things then deliver what human beings want – personal transport, a comfortable home, the ability to communicate, clothes and food.

What is an exajoule?
A exajoule is a unit of energy. Therefore it can be converted into, for example, kilowatt hours, which is another way of describing an amount of energy. To be a really useful measure, an exajoule will usually need to be expressed as a number for a particular period of time such ‘exajoules per year’.

475 exajoules, the world’s yearly use of energy from primary sources such as coal and oil, roughly translates into a continuous power use of about 5.5 terawatts. To put this figure into context, this is about 120 times the average electricity demand on the UK power grid. 5.5 terawatts spread over the world’s population is about 2 continuous kilowatts a head, or about 17,000 kilowatt hours a year. For comparison, the UK continuous power usage is about 5 kilowatts a head – two and a half times as much – and therefore approximately 42,000 kilowatt hours a year.

The paper sets up a four-stage chain. Fuels are extracted or, in the case of renewables, collected and then converted in a machine that turns them into heat or other useful energy source. The process occurs in what the authors call a ‘passive system’ such as a vehicle or a hot water system. The final service is something directly desired by the individual consumer or business, such as transport or comfort. There are efficiency losses in this stage in the chain.

The paper estimates the volumes of energy being used by the world’s major energy conversion devices. The top six machines are as follows:

Table 1

These machines are directed towards producing about 233 exajoules of heat a year and about 175 exajoules of motion. The energy for motion will be accompanied by heat. For example, a car’s petrol engine produces far more heat than energy for motion. So, in the case of a diesel engine, the world’s most important energy conversion device, only about 25% of the chemical energy in the fuel gets turned into energy to move the car.

The service provided by the energy can then be described. Table 2 shows the useful things we get from the 475 exajoules each year.

Table 2

Let’s look each output in turn. How much can we expect to be able to save through well-understood energy efficiency options? (Almost all of the figures in the following section are my estimates and are not from the Cullen/Allwood paper.)

Thermal comfort
Few buildings anywhere in the world are particularly well insulated. The typical British home loses around 250 watts per degree Celsius of temperature difference between the outside and the inside of the house. This means an average input of heat of around 200 kilowatt hours a year per square metre of space, compared to best practice (Passivhaus) levels of less than a tenth of this figure. Say, as a simple approximation, that we tried to get UK housing down to a level of 100 kilowatt hours per square metre. This would be expensive and unpopular since it would need most brick-built houses to be clad with insulation materials. If this 50% cut was replicated elsewhere, and also applied to building cooling needs (and there is no reason why not), world energy demand would be cut by approximately 10% (19% times 50%).

Other major energy-use savings could be generated by large-scale switching to heat pumps for home and business heating. We could, in theory, push the energy needed for thermal comfort down very dramatically, but the changes to buildings and their heating systems would have to be enormous. So I have used an estimate of a 50 exajoules energy efficiency saving.

Potential saving from better efficiency: 50 exajoules?

Sustenance
The average person needs about 2 kilowatt hours in food energy a day. (When talking about food, this 2 kilowatts is usually expressed as approximately 2,000-2,500 kilocalories.) The energy efficiency of food varies dramatically by type of product. Red meat might be 10% efficient (i.e. ten units of external energy are needed to produce one unit of food energy) whereas a grain such as oats, which is not generally heavily fertilised, might be as high as 500% (one unit of fossil fuel energy produces five units of food energy – most of the food energy comes from photosynthesis). About a quarter of the calories in the US diet come from meat and dairy products and a similar fraction in most of northern Europe.[3] If this figure fell to about one eighth, or if we switched from the least energy efficient meat (beef) to the best (chicken), the savings could be 40% of total energy consumption. Of course, a wholly vegan diet would increase these numbers hugely, but I haven’t assumed this.

Potential saving from better efficiency: 40 exajoules?

Structure
The key improvements here are weight reduction in the structural materials and a move to ‘closed loop’ recycling. For example, creating metals from ore is generally an extremely energy-expensive process. Think of making aluminium from bauxite, for example. Once we have created a metal from ore, there is usually no good reason ever to dispose of it. But dispose of it we do. 50% of aluminium cans go into landfill in the UK. Even valuable metals such as silver, widely used in very small quantities in electronic devices, disappear as your mobile phone is tossed into the waste.

Almost everything can be reused several times and sometimes indefinitely; but almost nothing is. And as the world becomes virtual, physical structures (such as paper) can be replaced by digits or by transient appearance on a screen.

The Cullen/Allwood paper also mentions the importance of such things as the streamlining of cars, another way in which structural changes can reduce the total need for energy.

Potential saving from better efficiency (this is even more of a guess than other estimates): 30 exajoules?

Freight transport
Freight transport is likely to remain as a major customer for fossil fuel suppliers for many decades. The diesel engine is only 25% or so efficient at turning the chemical energy into energy for motion, but only a huge rise in the price of oil is likely to prompt a switch to electric vehicles or electrically propelled railway trains. Diesel itself may be replaced by biologically derived oils, made from oil seeds or even algae. Whether these bio-oils can be described as more energy efficient in the language of the Cullen/Allwood paper is not clear. These forms of diesel are replacing fossil fuels with photosynthesis processes but the underlying efficiency of the engine remains the same.

In the medium term, it may be possible to switch diesel transportation to vehicles powered by hydrogen fuel cells. This would save energy since a fuel cell may offer twice the conversion efficiency of a diesel engine. Only half the energy is needed for the same amount of transportation

Potential saving from better efficiency: 10 exajoules?

Passenger transport
Passenger cars may switch to electricity and to hybrid electricity/fossil fuel. Both routes offer very substantial savings. Electric cars have approximately 80% conversion efficiencies (chemical energy to energy usable for motion) compared to 20% or so for petrol vehicles. This latter figure is rising quite fast as a result of innovations in materials, drive trains, aerodynamics, and other parts of the car. So a move to a car fleet that is battery equipped, possibly combined with a hydrogen fuel cell, may offer very substantial energy efficiency savings. Greater use of electricity for long-distance transport by rail and employment of fuel cells for urban buses will also help. But nothing in sight will reduce aviation’s energy use per passenger kilometre by as much as the use of electricity for cars.

Potential saving from better efficiency: 30 exajoules?

Hygiene
The appliances of motors can be made more efficient but the heating of the water is now the dominant use of energy in ‘wet’ domestic appliances. And, unfortunately, the energy used to heat a litre of water through ten degrees is always going to be the same. It’s certainly true that washing machines, for example, can be programmed to run at lower temperatures and use less water, but the remaining savings above and beyond what is already achieved are probably not enormous.

The amount of hot water for bathing may be possible to reduce by the use of water-saving showers, but the savings are probably not substantial.

Potential saving from better efficiency: 15 exajoules?

Communication
It’s not clear to me that large reductions in energy use are possible. As countries develop, they are also likely to devote a large fraction of their incremental national income to this category so total energy demand may rise, though this is not relevant to our estimate.

Potential saving from better efficiency: 10 exajoules?

Illumination
In most countries of the world illumination comes by the burning of fats and oils. Only in rich countries does a reasonable fraction of fossil fuel energy get employed in providing lighting. In these places, the switch away from incandescent bulbs to more advanced light sources is moving rapidly. A compact fluorescent in the home will typically be four times as energy efficient as the older technology (in terms of lumens per watt of electric power). LED bulbs, just now beginning to come into use, may introduce another four-fold improvement in efficiency. LEDs are also useful in many non-domestic applications such as street lighting, car headlights, and traffic lights.

The scope for a large percentage change in energy use is high, but the absolute amount of the saving in energy is not as large as, say, thermal comfort.

Potential saving from better efficiency: 10 exajoules?

Summing up the estimates
My highly tentative estimates suggest an approximate attainable saving of about 205 exajoules out of the annual global figure of 475. This is a saving of around 40% of current energy use. Let’s call the reduction 2.5 terawatts of continuous power

How much would it cost to achieve the same reduction in fossil fuel use by decarbonising our electricity use? The same net effect as saving 205 exajoules by energy efficiency would be provided by building about 2,000 nuclear power stations or about 2.5 million commercial-scale wind turbines. The cost of 2,000 nuclear power stations might be about £10,000bn ($16,000bn) or about £10,000 per person if divided among the richest one billion people on the planet. Wind might be about the same or even slightly cheaper if we could put most of the turbines onshore or in shallow and calm waters.

£10,000 per person is a large sum, even spread over 10 years. But it is probably less than the cost of achieving the energy efficiency gains mooted in this article. Take housing insulation, for example. Simple savings from wall insulation might only cost £1,000 or so, but generally wouldn’t achieve the 50% cuts in energy use I suggested might be possible in the section above. Really deep cuts in the energy that we use to keep ourselves warm might cost an order of magnitude more. So I want to suggest that even though some energy efficiency savings are cheap – and may even have a quick financial payback at current energy prices – the argument that ‘efficiency’ is always the cheapest way to reduce emissions is not obviously true. Beyond the easy savings from getting rid of gross inefficiency, investment in low-carbon energy sources may be a cheaper way forward.


Footnotes
[1] Jonathan Cullen and Julian Allwood, ‘The efficient use of energy: Tracing the global flow of energy from fuel to service’, Energy Policy, 38.1, pp. 75-81.
[2] Two newspapers for which I occasionally write have now banned the phrase ‘low-hanging fruit’. So I don’t use it in the text even though any article on energy efficiency normally has to use it in the first two paragraphs.
[3] Most of the figures in this paragraph are from Gidon Eshel and Pamela Martin, ‘Diet, Energy and Global Warming’, Earth Interactions, 10 (March 2006), pp. 1-17.

The Committee on Climate Change says the most important prospective source of cuts in greenhouse gases lay in the ‘decarbonisation’ of electricity generation. Photograph: Graham Turner/Guardian.

The budget confirmed the acceptance of the Committee on Climate Change‘s recommendation for carbon emissions in 2020. The UK will have to reduce its CO2 output by about 110m tonnes by 2020, equivalent to a 21% reduction on actual emissions in 2005 (and 34% on the 1990 figure). The proposed rate of emissions reduction is far faster than the UK has achieved thus far and the chancellor’s budget shows the government has started to recognise the scale of the challenge.

***

The committee told the government in December last year that the most important prospective source of cuts in greenhouse gases lay in the ‘decarbonisation’ of electricity generation. This can happen by increasing the percentage of renewable electricity, by capturing carbon at power stations and from switching to low-carbon fuels such as nuclear and gas.

The budget had incentives to encourage all of these changes. Most importantly, it improved the prospects for offshore wind. The budget recognised that the decline in bank credit, the falling price of carbon permits, and the sharp drop in the price of fossil fuels have made offshore projects increasingly difficult to fund. The worrying prospect that the 400-turbine London Array might be abandoned in the next few weeks forced the chancellor to increase unexpectedly the subsidy for electricity generated offshore.

He claims it is new government support. This isn’t quite right: we will all be paying through higher electricity bills. The new subsidy encourages the developers of this vital scheme to place their turbine orders in the next twelve months. My guess is that the government may not quite have done enough and that further fiscal bribery will be needed to get this vital project completed. This scheme, the largest offshore wind farm in the world, cannot be allowed to fail if the UK is to achieve the necessary ten-fold increase in renewables generation by 2020.

The second major measure from Darling was an unexpectedly large increase in the money going into carbon capture and storage. Energy experts have warned that the UK would not be ready to install capture technology on power stations until after the crucial 2020 date, meaning that the government’s carbon budget would be likely to be breached. So £90m is offered for ‘preparatory studies’ by the electricity generators to try to encourage more rapid progress.

There was also a remarkably vague promise to fund a further three working demonstrations of carbon capture in addition to the single contract that is likely to be awarded to the new Kingsnorth power station. We urgently need more detail on this policy change.

There were some crumbs offered to the micro-renewables industry to stop it collapsing entirely in the next twelve months. £45m is not going to go far, perhaps putting solar panels on 5,000 homes compared with the millions around the rest of Europe.

By contrast, energy efficiency measures were emphasised by the chancellor. He promised £400m for research and development, although it is unclear how much of this money is additional to existing allocations. We are definitely seeing progress in government commitments to financing fundamental work in energy efficiency and power generation. But, for comparison, the UK spends about £2.5bn a year on basic defence research and development, over six times as much as the new figure for energy.

The Committee on Climate Change’s other priorities for meeting the carbon budget included an emphasis on low-carbon vehicles and the chancellor has already announced some remarkably detail-lacking plans for subsidising electric cars. In the budget he also committed to spending £20m installing a network of battery-charging points in a couple of UK cities. This is a good start, but he would have been better changing the harsh tax treatment of electric delivery vans. This is the single measure that would do most to get silent, non-polluting vehicles on our urban streets.

He also made some perverse changes to car tax. The owners of existing cars that were among the most efficient when they bought them will now pay higher rates of duty. Owners who thought they were being virtuous are now going to be penalised. The Treasury’s not-so-subtle reasoning must be that the car tax revenues, which are tied to the carbon emissions of the vehicle – providing about 6% of all government receipts last time I looked – will start declining sharply as more and more people buy ultra-efficient cars.

As for the extraordinary car scrappage scheme, the less said the better. It would have been far more effective to pay people to tear up their driving licences and promise to use public transport.

Two further measures were also the opposite colour to green: the excise duty on lorries was held down to placate the road transport industry. And a number of incentives encouraged more drilling for oil and the extraction of the last barrels from existing fields.

Nowhere was the inconsistency between these proposals and overall emissions reduction noted by the chancellor.



This article was originally published in the Guardian on Wednesday 22 April 2009.

Image source: Smith Electric Vehicles.

Gordon Brown says he wants two or three cities to trial electric vehicles before the end of next year. After many false dawns, are we finally about to see the era of the battery car?

***

If so, it’s about time – electric vehicles promise real reductions in carbon emissions, inner-city pollution and urban noise levels. About a quarter of the UK’s CO2 comes from vehicles. Even if a battery in an electric car is charged using electricity from the grid, there are major savings in emissions. An electric vehicle has only a handful of moving parts, compared to many hundreds in an ordinary car. So reliability is high, maintenance costs are tiny and vehicle life may be almost indefinite.

Electric vehicles have been around for more than a century. Why should the world suddenly start to get interested? The most important reason is that battery prices are finally coming down. According to Valence Technology, the world leader in the latest generation of lithium phosphate batteries, we can expect battery packs with a range of 120 miles to cost less than £6,000 within a few years. Although this will add substantially to the price of cars, the owner will pay only about £2.50 to ‘fill up’ her vehicle, less than a fifth of the petrol equivalent. For people with daily commutes, electric cars will make good financial sense over the life of the vehicle – provided we can get banks to start making auto loans again.

The perception that electric cars are slow and ugly is also changing. The beautiful UK-designed Tesla has an acceleration that matches the fastest petrol cars. Other countries have already begun to jump on the battery-powered bandwagon. Portugal is establishing a network of street recharging points. Ireland wants a tenth of its vehicles to run on electricity by 2020. The major car manufacturers, led by Renault, are powering into battery vehicles as fast as they can. The UK is not alone in seeing that the future of the automobile is almost certainly electric.

So what do we need to do to get rapid development of the industry? We need funds to construct many thousands of charging points in the street and investment in the companies and universities working on improving battery technologies (Imperial College researchers are world leaders). Most importantly, we need support for the businesses already building battery cars and vans. Smith Electric Vehicles in Newcastle is the biggest manufacturer of electric vans and light trucks in the world and an optimist could see this company become one of our most important exporters within two decades.

This article was originally published in the Guardian on Wednesday 8 April 2009.