Chinese coal miners in an illustration of the
Tiangong Kaiwu encyclopedia, published in 1637
Flexible clean coal complements intermittent renewables
Coal-fired power plants will not only become more efficient, they will also become more flexible, providing essential grid services and backup capacities for the ambitious EU renewable energy targets. Thus, "clean coal" must also be "smart coal".
Already today, the growth in intermittent electricity from wind and solar challenges the design of both electricity markets and system operations. Increasingly, fossil-fuelled power plants are losing their traditional baseload operating hours and moving into a new role of "auxiliary" power provider, with renewables having priority dispatch. This new policy, favoured by the EU and actively promoted by many of its Member States, demands that coal-fired power plants operate with unprecedented flexibility. In fact, modern coal plants are much more flexible than old gas-fired CCGT plants (10 MW/min) and almost match new gas-fired plants (38 MW/min).
Flexibility is often assumed to come from natural gas-fired power stations. In many politically inspired scenarios with rapidly growing renewables, gas-fired power is also favoured because of its lower investment costs and lower specific CO2 emissions. However, it would be a fatal mistake to underestimate both coal’s present-day contribution to grid stability and its potential to provide very high flexibility and backup capacity in the future. Even today, coal plants run at partial load, providing reserve capacity and a number of system services, competing with gas plants in the respective markets. Modern coal plants can change from full load capacity to 50 % in less than a quarter of an hour and, unlike gas-fired plants, with little efficiency penalty. Thus, a 1,000 MW plant can provide a 30 - 40 MW load change each minute, and the flexibility of coal plants continues to be improved.
Also, given the global rush for raw materials and energy commodities, modern coal power plants will be a valuable insurance in a diversified portfolio approach which carefully and consistently responds to the dynamics of markets and prices. Europe, with more and more intermittent renewables and more dependence on oil and gas imports, would be wise to base the security of its electricity system on a diversity of fuels and technologies.