Instant Expert: Energy and Fuels New Scientist

Access to cheap energy is a lynchpin of modern industry and civilisation. Energy, mostly from fossil fuels, allows us to heat homes, and power factories and transportation systems. Worldwide every day, we devour the energy equivalent of about 200 million barrels of oil, but much of this energy comes from coal, gas and nuclear fuel too.
Starting with coal, and then oil and gas in the 1800s, we have plundered our fossil fuel riches to drive development. But now, an energy crisis looms. New oil sources are dwindling, and smothering greenhouse gases threaten the Earth - yet energy demands will rise by 50% to 60% by 2030. We need to rapidly develop sustainable solutions - from hydrogen cells to wind turbines - to fuel our future.
Most of the energy on Earth comes from the Sun. In fact enough energy from the Sun hits the planet's surface each minute to cover our needs for an entire year, we just need to find an efficient way to harness it. So far the energy in oil has been cheaper and easier to get at. But as supplies dwindle, this will change, and we will need to cure our addiction to oil.
Thirst for oil
Burning wood satisfied most energy needs until the steam-driven industrial revolution, when energy-dense coal became the fuel of choice. Coal is still used, mostly in power stations, to cover one-quarter of our energy needs, but its use has been declining since we started pumping up oil. Coal is the least efficient, unhealthiest and most environmentally damaging fossil fuel, but could make a comeback, as supplies are still plentiful: its reserves are five times larger than oil's.
Today petroleum (derived from oil) provides around 40% of the world's energy needs, mostly fuelling automobiles. The US guzzles up a quarter of all oil, and generates a similar proportion of greenhouse gas emissions. The first wells were drilled 2400 years ago, but the modern oil industry was born in the 1850s.
The majority of oil comes from the Middle East, which
has half of known reserves. But other significant sources include Russia, North America, Norway, Venezuela and the North Sea. Alaska's Arctic National Wildlife Refuge could be a major new US source, to reduce reliance on foreign imports, but drilling there is currently prohibited.
Most experts predict we will exhaust easily accessible reserves within 50 years, though opinions and estimates vary. We could fast reach an energy crisis in the next few decades; when demand outstrips supply. As conventional reserves become more difficult to access, others such as oil shales and tar sands may be used instead. Petrol could also be extracted from coal.
Since we started using fossil fuels, we have released 400 billion tonnes of carbon, and burning the entire reserves could eventually raise world temperatures by 13°C. Among other horrors, this would result in the destruction of all rainforests and the melting of all Arctic ice. London would be as hot as Cairo, but would also be engulfed by seawater. (See our Special Report on Climate Change for more.)
Gas, naturally
Natural gas reserves could plug some of the gap from oil, but reserves of that - some of which are in Russia, the Middle East and the Wadden Sea - will not last into the 22nd century either. We currently use it for around one-third of world electricity generation.
Natural gas, which is mostly methane, is the cleanest fossil fuel by weight, emitting just 40% the greenhouse gases of coal and 25% of oil. As a less-polluting alternative to petrol, its use is increasing in automobiles - either as compressed natural gas or for powering hydrogen fuel cells. When reserves do run low, we may be able to access vast frozen methane hydrate reserves beneath the seabed.
In the next few decades, one way for the UK and others to meet greenhouse gas reduction commitments, could be increased nuclear power generation. Currently, about 440 reactors in 32 countries generate 16% of world electricity. (See our Special Report on The Nuclear Age for more.)
Despite a slow decline of support for nuclear power in the west following the Chernobyl disaster in 1986, many countries, such as the US, Japan and India are now embracing the technology again. But using nuclear power to mitigate environmental damage is a double-edged sword, because disposing of nuclear waste is itself an intractable problem. Expense, safety in usual operation and terrorism are major concerns too, not to mention the fact that building new facilities can take decades.
Sustainable alternatives
Less-polluting renewable energy sources offer a more practical long-term energy solution. They may benefit the world's poor too. "Renewable" refers to the fact these resources are not used faster than they can be replaced.
The Chinese and Romans used watermills over 2000 years ago. But the first hydroelectric dam was built in England in 1870. Hydroelectric power is now the most common form of renewable energy, supplying around 20% of world electricity.
China's Three Gorges Dam, which has just been completed, is the largest ever. At five times the size of the US's Hoover Dam, its 26 turbines will generate the equivalent energy of 18 coal-fired power stations. It will satisfy 3% of China's entire electricity demand. Surprisingly, some argue that hydroelectric dams significantly contribute greenhouse gases.
In 2003, the first commercial power station to harness tidal currents in the open sea opened in Norway. It is designed like windmill, but others take the form of turbines, oscillating hydroplanes, flexible eel-like generators, or are made of floating pontoons that rise up and down with the waves and tide.
As prices fall, wind power has become the fastest growing type of electricity generation - quadrupling worldwide between 1999 and 2005. Modern wind farms consist of turbines that generate electricity. Though it will be more expensive, there is more than enough wind to provide the world's entire energy needs.
Wind farms come in onshore and offshore forms. They can often end up at spots of natural beauty, and are often unpopular with residents. And turbines are not totally benign - they can interfere with radar and leave a significant ecological footprint; altering climate, sending wildlife diving for cover and killing sea birds. Migrating birds may have more luck avoiding them.
Scotland is building Europe's largest wind farm, which will power 200,000 homes. The UK's goal is to generate one-fifth of power from renewable sources, mainly wind, by 2020. But this may cause problems, because wind is unreliable.
Future buildings with integrated turbines could generate 20% of their own power. Other visions see wind-power revived for shipping, floating wind farms, or 28-kilometre-wide flying behemoths powered by high speed winds in the upper atmosphere. There are also plans to construct a 1-kilometre-tall tower that would harness wind energy from heated air in the Australian outback.
Catching some rays
Using solar power to generate electricity has been considered since Victorian times and clever building designs that use it to regulate temperature have been around for millennia. Today solar power is used in several ways. In thermal solar power, sunlight directly heats water in rooftop panels for household supplies, while sunlight can also be converted to electricity using photovoltaic cells, which use semiconductors to turn photons into electricity.
Both types of power are intermittent sources, as they can only work in good light. Photovoltaic cells have been too expensive for widespread use, but are already popular for supplying electricity to remote locations and filling gaps in ramshackle electricity grids. Solar panels often power spacecraft too, and solar cars and aeroplanes.
New cheaper versionsof photovoltaic cells could mean more energy is generated from solar than nuclear power by 2020.
In the future we may generate solar power using flexible coverings that "clothe" both buildings and people. There is even a scheme for an orbiting solar power station.
Running on empty
When oil runs out what will we fuel our cars with? This question, plus the fact the exhaust fumes are one of the greatest contributors to greenhouse gas emissions, means the race is on to find a new solution to getting around.
Biofuels have been around since the internal combustion engine. Ethanol is added to petrol in the US, and millions of cars in Brazil are run on it too. Vegetable oils are already used in Europe to produce biodiesel. Soya oil could be used for aviation too. Biofuels such as fast-growing elephant grass or saplings could be used to provide heat and electricity. Even sewage is being considered as a biofuel.
Hydrogen fuel cells have enormous potential if technical problems can be solved. Essentially a kind of battery that can be continuously refilled, fuel cells chemically react hydrogen with oxygen - producing just electricity and water.
This is a far more efficient process than burning fuel, as much less energy is wasted as heat. See how it works here. But it's not just useful in cars: hydrogen could also be used in power stations and electronic and portable gadgets too. Miniature fuel cells may one day oust batteries.
The problem is that catalysts and membranes have been expensive until recently. Other problems include making tanks of pressurised flammable hydrogen safe enough for cars and creating an entire fuelling station infrastructure. Combining traditional engines with fuel cells could be step in the right direction. A new $10 million prize has been offered to help solve these problems.
Fuel cells can also use natural gas, methanol or coal - but these produce carbon dioxide. Hydrogen is not yet a completely clean either, as electricity - currently derived from fossil fuels - is needed to"crack" water to produce the hydrogen. Some cities, such as Reykjavik, already use hydrogen to power buses. But Iceland gets some electricity and over 80% of its heating and hot water from geothermal energy sources, and can produce the hydrogen emission-free. Other countries need to find ways to produce the hydrogen sustainably.
Driving efficiency
Some argue that the "hydrogen economy" is a distraction from meeting future energy needs and slowing climate change, and that we need to focus on more immediate solutions. Making social change might be more difficult than solving technical problems.
Solutions that could be put in place right now include filtering carbon dioxide out of emissions and burying it in oil seams or under the sea. The US is among 6 nations that have turned their back on the Kyoto protocol to curb climate change and are focusing instead on "clean energy" from fossil fuels.
Increasing efficiency in energy production could also yield massive savings, as it did during the oil crises of the 1970s. Methods vary from reducing the friction of trains to lowering speed limits for cars.
Producing combined heat and power with small generators at home, makes use of a lot of the energy wasted in power stations, and might one day feed energy back to the grid. Wind and solar power could also be rigged up on a rooftop near you in the future - even the Queen of England is now generating her own power from the River Thames.
John Pickrell, 26 May 2006
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