Could coal and gas power actually allow for greater use of renewable energy, with lower overall emissions? The idea may seem paradoxical, but that’s the conclusion of a UN working group set up to examine ways of making fossil fuels cleaner.
The “Group of Experts on Cleaner Electricity Production from Fossil Fuels, which operates under the UN’s Economic Commission for Europe secretariat, recently published a report outlining four renewable-fossil fuel technology combinations that would result in substantially more renewable energy being deployed overall. In each case the idea is to combine the big benefits of fossil fuel power – reliability and scale – with the low-emissions advantages of renewables.
The four main options are outlined below:
1. A concentrated solar power/coal power hybrid
Concentrated solar power (CSP) plants have been pioneered by Spain and the US. They use a giant array of mirrors to reflect highly concentrated solar rays at a central tower containing a boiler. Steam from the superheated water then drives a turbine to produce electricity.
The report says that a CSP plant could feed extra heat into the boiler of a coal-fired power station, essentially allowing the coal plant to produce the same amount of power by burning less coal. This means a cut in overall emissions.
2. Coal gasification plants with carbon capture and storage powered by wind
Coal gasification plants convert solid coal into synthetic natural gas, allowing the coal to be burnt at half the emissions of conventional coal power stations. These kinds of plants are ideal for carbon capture and storage (CCS), as it’s much easier to capture CO2 during the gasification stage than the burning stage
CCS can deliver emission reductions of up to 90 percent. However to work, CCS technology requires extra energy – over above the energy that the power station is already producing. This means it has to either generate less power for the same amount of coal – which ruins the economics – or get the extra energy from somewhere else.
According to the report, wind turbines could provide this additional power at no extra cos (since wind is free once the turbines are built) and with zero emissions.
3. Solar-aided carbon capture and storage
Concentrated solar power like wind, could also be used to offset the “energy penalty” incurred by using CCS with coal. A large solar array would collect heat energy which would then power the “stripper” used to chemically strip out the CO2 from coal once it has been burnt.
The deserts of North Africa could be a prime candidate for these systems in future.
4. Using wind and solar to produce hydrogen for coal gasification plants
The biggest disadvantage of wind and solar power is that they cannot produce “dispatchable” electricity, i.e. electricity that is on demand ready for use whenever needed. What they can do however is produce hydrogen, by running an electrical current through water.
According to the report, hydrogen from wind or solar could then be fed into a coal gasification plant. By reducing the amount of coal needed to produce synthetic gas, this would reduce the emissions from such a plant by an estimated 57 percent.
This UN report comes in the wake of America’s announcement that it wants to help lead a “global alliance of countries willing to make fossil fuels cleaner rather than abandoning them,” in the words of US Energy Secretary Rick Perry. The US believes it is immoral to ask developing countries, where millions on people live without energy access to give up on fossil fuels.
All four of the options outlined in the report are being intensively researched in the US, which has funded pilot projects aimed at demonstrating each of the concepts. These technologies could well form the basis of future knowledge-transfers between the members of the cleaner fossil fuels alliance.
There is still a real need for fossil fuel-powered development in the world. By deploying the latest technology, we can secure the benefits of that development and still deliver on climate commitments, making full use of the world’s wind and solar resources.