Green house

The warning signs have been coming for some time. Reports have highlighted the need to reduce carbon emissions, with last month’s Stern Report stressing the dire consequences of climate change for the economy.

Industry and commerce have been finding ways of reducing their carbon impact for some time but the message is now getting through to the public as well: minimise your energy use; reduce your carbon emissions; do your bit for the environment. And do it now. If global climate change is being caused by human activity, then this could be our last chance to avoid the worst consequences of the warming of the atmosphere.

If getting the message through is difficult, taking action is even harder. According to the Office for National Statistics, domestic buildings emit almost as much carbon dioxide as any other sector. If emissions from power stations are allocated to the end-users of the electricity they generate, households emitted greenhouse gases equivalent to 41.2 million tonnes of carbon dioxide in 2003, while industry emitted 42.8 million tonnes and transport 43.8 million tonnes.

The total from each household is a tiny proportion of this. People could be forgiven for thinking that their emissions are so small that their contribution will make no difference. But if everyone thought that, emissions would never reduce.

So attention is shifting to technology. How can we build houses that are more energy-efficient? What techniques and devices can help us cut our energy consumption? What sort of technologies could help us live in a more sustainable way without having to sacrifice heating, lighting and household appliances?

The government has also taken notice of the need to reduce household energy use, with housing and planning minister Yvette Cooper calling on developers to match the environmental performance of Scandinavian housing.

The harsher climate in northern Europe means features such as triple-glazing, super-insulation and higher levels of airtightness in housing are standard. The government is reviewing building regulations and instituting a building code for sustainable homes to set stricter minimum standards for these passive, energy-saving technologies.

According to Neil Cutland, associate director of the Building Research Establishment’shousing centre and a specialist in low-carbon buildings, the situation is beginning to improve. ‘We’re heading progressively down the low-carbon route,’ he said. ‘We are behind the regulations in Scandinavia, although all the European countries are different; but there are many individual houses and developments being built to consistently better standards than the building regulations.’

For instance, Nottingham University has joined building company Stoneguard to build a ‘research house’ with features such as a ground cooling/heating system that uses the earth below the house to store energy for heating.

Cladding boosts the insulation properties of the walls, while an integrated conservatory — which the builders call the ‘sun space’ — acts as a solar energy collector. The team expects the house to produce 60 per cent less carbon dioxide than a standard home.

Neil Cutland aims to develop and promote technologies such as this to produce houses that emit little or no carbon dioxide. In the short term, he said, this means copying the Scandinavians, improving insulation to ensure houses are more airtight and heating requirements are minimised.

However, getting to zero carbon will need more than this. ‘To get to that and then to go into energy-contributing houses we have to involve what we’d loosely call gadgets, like photovoltaic cells, wind turbines and micro-CHP (combined heat and power).’

Technology can play a key role in helping keep energy consumption under control. At Imperial College, London, David Fisk heads a series of studies into urban energy systems, looking at the way energy is distributed and used within cities. According to him, the technology is already used in the commercial sector but technology transfer is not easy.

‘Building management systems are a good example,’ he said. ‘These sorts of systems that manage all the ventilation, heating and lighting in a building are well-established. Johnson Controls had them in steelworks in the 1930s, then they went into very large commercial buildings and now you’ll find a small BMS in every commercial building. The next stage for them will be the domestic market. But it’s a question of developing them for that market and that means simplifying them and driving down the cost.’

Experience of technology and simplicity are vital for all volume technologies, Fisk added, because they have to be easy to install and repair.

‘Trying to innovate when you have no cost margin and no experience of the equipment and what can go wrong with it is really hard. If you make a new gadget and sell five of them then two of them go wrong, one’s in Scotland and one’s in Cornwall, you’d use up all your profit in finding out why they’ve gone wrong. If you already know how they work from commercial building experience, the only thing you’re worrying about is whether you can build them cheaply enough.’

Fisk agrees that improving the airtightness of buildings is vital, but points to a problem. ‘Keeping cool can be difficult. Your body has to get rid of 100W of energy; the hottest skin temperature you can get is about 30°C and after that you’re relying on evaporation, which is fine unless it’s humid.’

If houses are made airtight, there is a need for much better-designed ventilation systems to make sure people do not overheat. ‘We haven’t been used to summers so hot that children and old people can’t get rid of their excess heat, but we may have to,’ said Fisk. Even in cold weather, sunlight on windows can heat the air in the house to uncomfortable levels.

This does not mean every house will need air conditioning, said Cutland. ‘The simplest way to address the problem is to add thermal mass to the house. But you’ll need a properly ducted ventilation system, with fans linked to decent controls, probably using humidity sensors.’

When the air starts to get hot and moist, the sensors trigger a fan to draw the air away into a heat exchanger. This recovers the energy from the air and puts it back into, for example, the hot water systems. ‘That would help you to recover 70-80 per cent of the energy. You don’t want to just blast out the heat that you’ve so carefully put in there.’

While these systems keep conditions comfortable and heating bills low, others can help manage the power load. ‘We have difficulty with power management at the moment,’ Fisk said. ‘But we now have the technology for much more sophisticated local control of electricity supply and therefore improving the economics of everything we connect to the grid.’ This means developing appliances that switch off automatically when electricity demand rises, ensuring power stations do not need to meet large variations in power supply.

Fisk explained that this could involve modulating the AC frequency of the electricity supply to send signals to control systems integrated into fridges and freezers. When a surge in electricity demand is predicted — or a drop in anticipated supply, as might happen in an area with a proportion of supply from wind turbines when the wind drops — the appliances would reduce their temperature to their lowest operational setting before the event then switch themselves off until the crisis point had passed. ‘The reason this is suddenly possible is that it’s the sort of communications technology you can get down the wire,’ Fisk said. ‘It means two things: you can manage the loads more easily and you can get microgeneration, such as roof-mounted wind turbines, on to the system.’

New technologies also promise to reduce consumption elsewhere. Lighting, for example, is one of the largest consumers of electricity in the domestic sector. Shifts are already taking place from incandescent lightbulbs to energy-saving bulbs, which are based on fluorescent technologies. The next switch will be to solid-state lighting, based on LEDs.

Commercially available LEDs are now about as efficient as fluorescent lights, said Eric Meulenkamp, head of research into photonic materials and devices at Philips. ‘Incandescent lights produce about 15 lumen per watt, while fluorescents are of the order of 70 lm/W,’ he said. ‘Low-power LEDs in the lab are producing the order of 130-140lm/W — twice as efficient as fluorescents — but those aren’t yet suitable for lighting applications: we’re hoping to get that sort of performance from a high-power LED in two or three years.’ Unlike conventional light sources, LEDs do not burn out so would not need replacing.

Transferring these types of LED to a domestic environment will change the design philosophy of lighting.

Meulenkamp said there are two big differences between LED lighting and conventional lights: LEDs are point sources, sending light out in only one direction, rather than in all directions such as light bulbs or fluorescent tubes. They are also monochromatic, rather than producing white light. ‘There are a lot of technical challenges to turn these single-colour point sources into a diffuse white lamp,’ he said.

White light can be produced by colour mixing, Meulenkamp said, with the output of red, green and blue LEDs being combined to produce light, or using a phosphor. These are semi-transparent screens coated with a substance that absorbs a portion of light from a blue LED and fluoresces, giving out yellow light. ‘You make it in such a way that part of the blue still comes through. The rest is turned yellow and the combination of these gives you white light.’

In both cases, the balance of the colours of the lights can be changed by altering the voltage through the LEDs. This would make it easy to adjust the colour and quality of the light.

LEDs are extremely small and easy to integrate into walls, ceilings, or even, David Fisk said, into windows. ‘You can coat both sides of the glass with very thin copper that you can see through, then embed LEDs in the glass,’ he said. ‘The copper carries the current and when you switch it on, it looks like starlight.’

Despite these innovations, however, people will still need to be more energy-savvy. Jonathan Stearn of UK advisory group Energywatch, said they are missing one vital factor — information.

Echoing David Fisk’s car analogy, Stearn said that for householders, trying to reduce energy use is like trying to keep a car within the speed limit when you cannot see the speedometer. ‘You have very, very little idea of how much energy you’re using.’

Because of this, Energywatch is advocating ‘smart meters’, to give consumers more information on their energy use. ‘These will have a screen which gives consumers up-to-the-minute information on the energy they’re using, when they’re using it, displayed in terms of how much it’s costing them, rather than in abstract units like kilowatt hours, which are hard to interpret.’

The meters will also send information directly to the electricity supplier via an Ethernet-like link, allowing them to bill customers accurately rather than sending them estimated bills.

Giving people information helps them to understand their energy use, Stearn said. ‘It visibly shows you where you’re burning energy, so it shows them the effect of all the things we tell people they should do, like making sure lights are switched off and the TV isn’t on standby. They’ll be able to see how much energy that uses and how much it costs them.’

A large-scale study of the effect of smart metering was recently completed by Canadian energy supplier Hydro One, following how 400 households reacted to the extra information over a 2.5-year period.

On average, the report found, consumption dropped by 6.5 per cent. ‘All indications are from this and other studies that there is a direct link between information and behavioural change,’ Stearn said. ‘As soon as you give people the means to understand their situation and do something about it, they start to take action.’

Even the more mundane aspects of energy saving are seeing innovations. Double-glazed windows, a mainstay of environmental building technologies for decades, are about to enter a new generation.

A team led by Bernhard Durschang of the Fraunhofer Institute for Silicate Research has developed a method of evacuating the space between the glass panes, which halves the thermal conductivity of the window compared with conventional double glazing. The windows need toughened glass and spacers to prevent them from collapsing. They are unlikely to be cheap enough for domestic use for some time but should enter the housing market within the next 10 years.

Neil Cutland said the urgency imparted by environmental studies and the government’s insistence on prompt action is driving the market fast. ‘The deep greens — the people who really are motivated by saving energy rather than cutting their electricity bills — are going to take these technologies up first,’ he said. ‘But we hope it’s going to become mainstream in the near future.’

With a little help, we could all be deep green.