Can we really do without coal? - part II

This is the second part of a two-part series. Part one, on how the divestment movement needs to change, is available here.

Coal power plants in China and other developing economies are creating killer smogs, which are poisoning the population as well as spewing billions of tonnes of greenhouse-causing carbon dioxide into the atmosphere.

In future, coal must be made to burn more cleanly (to cut air pollution) and more efficiently (to reduce the amount of greenhouse gas emitted for every kilowatt-hour of electricity generated).

In both cases, the challenge is to bring the whole fleet of coal-fired power stations up to the standards of the best.

Even in the United States, more than half of coal-fired power plants are over 40 years old. China and India, too, have lots of very old facilities. Most of these old plants are too small to reach maximum efficiency and employ outdated technology. (“Focus on clean coal” Nov 2006)

The average power plant in the United States or China achieves a thermal efficiency of just 33 per cent. For every three units of energy contained in the fuel burned in the plant only one unit of usable electrical energy is delivered to the grid. In India, the percentage is even lower.

But modern plants built on a scale of 500 or even 1000 megawatts, with ultra-supercritical boilers, can achieve thermal efficiencies of 40 per cent or more, burning less coal to produce the same amount of power.

Even higher efficiencies are possible if instead of burning the coal directly it is gasified and the gas is then used in a combined cycle system (first driving a gas turbine and then a steam turbine). Integrated gasification and combined cycle plants are tricky to build and operate but could achieve thermal efficiencies of 45 per cent.

China, India and even the United States are now building power plants that are larger, far more efficient and with better pollution-control technology. Modern coal-fired power plants can make a contribution towards slowing climate change, in combination with more use of natural gas, renewables such as wind and solar, nuclear power, and energy efficiency measures on the demand side.

The question is how to shut down the fleet of old power plants that fall far below these standards. “To reduce emissions, replacement of the oldest plant should be a high priority, but it is rarely economic, and electricity demand growth dictates that these plants often remain open,” the International Energy Agency explained in 2006.

In the United States, the Obama administration is now attempting to force these old power plants to shut or undertake expensive upgrades by introducing strict rules on pollution and carbon emissions.

China, India and other developing countries will eventually have to overhaul their own older coal-fired plants if they are to enjoy clean air and contribute to global efforts to limit climate change.

The realities of the energy system mean there has to be a future for coal.

Even in the United States, with its shale gas boom, coal is still expected to account for 30 per cent of power generation by 2025, down from 37 per cent currently. In Asia, coal's share is currently much higher and cannot conceivably be replaced by gas.

To limit the impact, however, coal will have to be burned in power plants very different from most of those in existence today.

Rather than trying to shut down the coal industry, campaigners would be more effective if they focused on trying to modernise the electricity sector to use newer, larger, cleaner and more efficient power plants.

Originally published by Reuters. Reproduced with permission.