A provision of flexible decarbonized power plant fleet
requires assessment of all aspects of their dynamic operational conditions. As example, figure below schematically presents the measures to be undertaken in a coal-fired power plant in order to increase the share of intermittent solar and wind power generation in an electric power system.Interplay among intermittent power generation by solar and wind plants, decarbonised thermal power plant and electricity consumption load.
The measures for decrease of CO2 emission involve retrofitting and new design solutions of boiler furnaces to provide combustion of natural gas and biomass, co-firing of coal with biomass and natural gas as well as with hydrogen. Further, the application of technologies for CO2 capture and storage (CCS) is ultimate. When deploying the CO2 capture technologies, the type of fired coal, from lignite to mixtures of lignite and other brown coal types of higher calorific values will be taken into account with the plant power capacity.
The increase of plant flexibility by new technical solutions based on advanced balance-of-plant designs will be realized by
- formulation of improved operational procedures for increase of primary control reserve by already existing plant components and by
- development of new technical solutions for utilization of waste heat of flue gas for heating up of feedwater / condensate.
The operational procedures will be based on variation of feedwater flow rate through high pressure regenerative heaters which affects steam flow rate from turbine extractions and lead to desired change of turbine power.Implementation of additional economizers in flue gas channel will increase plant efficiency, while their connection to relevant plant components will provide increase of its control reserve
The increase of plant flexibility by use of thermal energy storage will focus on new retrofits with application of devices for thermal energy storage (TES) which provide capacity for primary and secondary control of electric power systems. TES devices are, namely, charged in periods of excess electricity production or lower electricity consumption and discharged in periods of peak electricity consumption or shortages in electricity generation due to lower production in solar and wind units or due to malfunction or shut downs of other power units. Technical solutions for energy storage in hot water tanks, molten salt tanks, phase change materials as well as in solid materials will be considered. Special attention will be paid on new technical solutions for implementation of the steam accumulator into thermal power plant. According to this design, accumulated steam substitutes the steam turbine extractions towards feedwater and condensate heaters, which results in increase of the steam flow rate through turbine stages and increase of power generation.