Carbon is usually typecast as a villain in terms of the environment but researchers at the University of Warwick have devised a novel way to miniaturise a technology that will make carbon a key material in some extremely green heating products for our homes and in air conditioning equipment for our cars.

Professor Bob Critoph, University of Warwick. (Credit: Image courtesy of University of Warwick)

Most domestic heating and automotive air conditioning requires a lot of energy. Domestic space heating and hot water account for 25% of energy consumption in the UK. Across the EU, vehicle air conditioning uses about 5% of the vehicle fuel consumed annually, and within the UK it is responsible for over 2 million tonnes of CO₂ emissions.

To combat global warming, new technologies to reduce these emissions are vital. Researchers at the University of Warwick have been working on practical solutions for many years and are now developing new energy saving technologies.

In houses, the best condensing boilers are about 90% efficient. There are electric heat pumps on the market that use electricity to extract heat from the outside air or the ground to heat homes more efficiently, but the electricity used still incurs large CO₂ emissions at the power station. Researchers have long been aware of a much more energy efficient way to drive heat pumps (or air conditioners) using adsorption technology. This uses heat from a gas flame or engine waste heat to power a closed system containing only active carbon and refrigerant. When the carbon is at room temperature it adsorbs the refrigerant and when heated the refrigerant is driven out. A process which alternately heats and cools the carbon can be used to extract heat from the outside air and put it into radiators or hot water tanks. In the case of air conditioning it extracts the heat from the inside of the car. The major snag has been that adsorption technology to date would need to be roughly 300 litres in volume for a car air conditioner and larger for a heat pump to heat your house. Clearly that is not going to fit into a car and the volume of unit required for domestic heating probably couldn’t fit under your stairs at home either…

However University of Warwick researchers have made a breakthrough in adsorption systems design that dramatically shrinks these devices making them small and light enough for use in both domestic heating and automotive air conditioning. They have devised and filed a patent on a clever new arrangement that distributes thin (typically 0.7mm thick) sheets of metal throughout the active carbon in the heat exchanger. Each of these sheets contains more than a hundred tiny water channels (typically 0.3mm in diameter) designed to make the heat transfer much more efficient. This has enabled the Warwick team to create adsorption based equipment that is up to 20 times smaller than was previously possible.

The researchers expect that their new adsorption technology can create domestic heat pumps that will produce a 30% or more reduction in domestic fuel bills (and CO₂ emissions) compared to even the best condensing boiler. In car air conditioning systems their new system can exploit waste heat from the engine, converting it into useful cooling. Because no (or very little) mechanical power is then taken from the engine it will reduce both fuel consumption and CO₂ emissions by nearly 5%. The research team also anticipate that in new vehicle models the system can be integrated with little or no extra cost.

The University of Warwick engineers have had significant interest in the new technology from a range of companies, and they have already entered a technical partnership with a major global vehicle manufacturer to develop and demonstrate the technology. There has also been considerable interest from the domestic heating and hot water market

This significant commercial interest has led to a new spin-out company, Sorption Energy Ltd, being set up by Warwick Ventures, the university’s technology transfer office, and H2O Venture Partners. Initially the company will use the new patent pending technology to focus on two high value markets: greener heating and hot water systems for houses and air conditioning for cars.

Lead researcher on the new technology, University of Warwick’s Professor Bob Critoph said:

“My team has been working on these developments for several years, supported by grants from EPSRC and the EU totalling over £2.5million. The technology is now ready for commercialisation and we are very excited by the opportunities which are developing. It is particularly pleasing that the technology will significantly help reduce CO₂ emissions.”

Dr David Auty, Chief Executive of Sorption Energy said: “This is exciting stuff. The technology has been proven in the University’s laboratories at the sizes needed for vehicles and domestic systems, and there are several other large markets. The ability to provide products which make significant reductions in both energy consumption and CO₂ emissions at a similar price to existing products will make Sorption Energy very attractive to customers, and is very satisfying for the team.”

“The UK is the global market leader in gas boilers. There are 21 million gas boilers in the UK with 1.7million installed each year, mainly replacements, and around 11 million units sold annually worldwide. For domestic housing the retrofit market is the primary interest: 80% of the housing for 2050 has already been built. This presents both a massive opportunity both for emission reduction and for UK industry.”

Most of the technology needed to shift the world from fossil fuel to clean, renewable energy already exists. Implementing that technology requires overcoming obstacles in planning and politics, but doing so could result in a 30 percent decrease in global power demand, say Stanford civil and environmental engineering Professor Mark Z. Jacobson and University of California-Davis researcher Mark Delucchi.

To make clear the extent of those hurdles – and how they could be overcome – they have written an article in Scientific American. In it, they present new research mapping out and evaluating a quantitative plan for powering the entire world on wind, water and solar energy, including an assessment of the materials needed and costs. And it will ultimately be cheaper than sticking with fossil fuel or going nuclear, they say.

The key is turning to wind, water and solar energy to generate electrical power – making a massive commitment to them – and eliminating combustion as a way to generate power for vehicles as well as for normal electricity use.

The problem lies in the use of fossil fuels and biomass combustion, which are notoriously inefficient at producing usable energy. For example, when gasoline is used to power a vehicle, at least 80 percent of the energy produced is wasted as heat.

With vehicles that run on electricity, it’s the opposite. Roughly 80 percent of the energy supplied to the vehicle is converted into motion, with only 20 percent lost as heat. Other combustion devices can similarly be replaced with electricity or with hydrogen produced by electricity.

Jacobson and Delucchi used data from the U.S. Energy Information Administration to project that if the world’s current mix of energy sources is maintained, global energy demand at any given moment in 2030 would be 16.9 terawatts, or 16.9 million megawatts.

They then calculated that if no combustion of fossil fuel or biomass were used to generate energy, and virtually everything was powered by electricity – either for direct use or hydrogen production – the demand would be only 11.5 terawatts. That’s only two-thirds of the energy that would be needed if fossil fuels were still in the mix.

In order to convert to wind, water and solar, the world would have to build wind turbines; solar photovoltaic and concentrated solar arrays; and geothermal, tidal, wave and hydroelectric power sources to generate the electricity, as well as transmission lines to carry it to the users, but the long-run net savings would more than equal the costs, according to Jacobson and Delucchi’s analysis.

“If you make this transition to renewables and electricity, then you eliminate the need for 13,000 new or existing coal plants,” Jacobson said. “Just by changing our infrastructure we have less power demand.”

Jacobson and Delucchi chose to use wind, water and solar energy options based on a quantitative evaluation Jacobson did last year of about a dozen of the different alternative energy options that were getting the most attention in public and political discussions and in the media. He compared their potential for producing energy, how secure an energy source each was, and their impacts on human health and the environment.

He determined that the best overall energy sources were wind, water and solar options. His results were published in Energy and Environmental Science.

The Scientific American article provides a quantification of global solar and wind resources based on new research by Jacobson and Delucchi.

Analyzing only on-land locations with a high potential for producing power, they found that even if wind were the only method used to generate power, the potential for wind energy production is 5 to 15 times greater than what is needed to power the entire world. For solar energy, the comparable calculation found that solar could produce about 30 times the amount needed.

If the world built just enough wind and solar installations to meet the projected demand for the scenario outlined in the article, an area smaller than the borough of Manhattan would be sufficient for the wind turbines themselves. Allowing for the required amount of space between the turbines boosts the needed acreage up to 1 percent of Earth’s land area, but the spaces between could be used for crops or grazing. The various non-rooftop solar power installations would need about a third of 1 percent of the world’s land, so altogether about 1.3 percent of the land surface would suffice.

The study further provides examples of how a combination of renewable energy sources could be used to meet hour-by-hour power demand, addressing the commonly asked question, given the inherent variability of wind speed and sunshine, can these sources consistently produce enough power? The answer is yes.

Expanding the transmission grid would be critical for the shift to the sustainable energy sources that Jacobson and Delucchi propose. New transmission lines would have to be laid to carry power from new wind farms and solar power plants to users, and more transmission lines will be needed to handle the overall increase in the quantity of electric power being generated.

The researchers also determined that the availability of certain materials that are needed for some of the current technologies, such as lithium for lithium-ion batteries, or platinum for fuel cells, are not currently barriers to building a large-scale renewable infrastructure. But efforts will be needed to ensure that such materials are recycled and potential alternative materials are explored.

Finally, they conclude that perhaps the most significant barrier to the implementation of their plan is the competing energy industries that currently dominate political lobbying for available financial resources. But the technologies being promoted by the dominant energy industries are not renewable and even the cleanest of them emit significantly more carbon and air pollution than wind, water and sun resources, say Jacobson and Delucchi.

If the world allows carbon- and air pollution-emitting energy sources to play a substantial role in the future energy mix, Jacobson said, global temperatures and health problems will only continue to increase.