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The decarbonization of the electrical energy sector is in progress for contrasting the climate changes, with a relevant increase of the Renewable Energy Sources (RES) power plants, mostly in Dispersed Generation (DG). The adequacy and the security of power systems, with a huge penetration of RES in DG is possible with a suitable integration of energy storage. In fact, energy storages can provide many different services for long-term adequacy and real time security. In this framework the present paper deals with a Thermal Energy Storage (TES) proposed for power system services. The technology presented is made up of modules containing a bed of fluidizable solid particles, which can store thermal energy from waste heat, process heat and/or from electricity. Stored thermal energy can be released, e.g. as superheated steam, for thermal uses or converted into electricity, by means of steam turbines. Some possible applications are then reported explaining advantages and limits.

Climate change problems cannot be addressed without a transformation of the energy production sector, since it is responsible for a significant share of total greenhouse gas emissions. For this reason, governments are promoting the use of Renewable Energy Sources (RES), especially wind and solar. In order to increase the penetration of RES, whose energy production cannot be controlled to follow the demand, more and more energy storage systems are needed, for ensuring adequacy and security to electrical power systems. This paper is focused on an innovative thermal energy storage technology based on fluidized solid particles, capable of receiving energy as electricity and storing it as heat for later use, e.g. produce steam for industrial applications. In such a system, electric energy is converted to heat by means of resistors, that can be supplied with AC and/or DC sources. In the paper, different use-case scenarios are presented, involving the grid and/or a photovoltaic plant as electric power sources. Then some possible configurations for power converters are described and compared, to find the most appropriate solution for each use-case scenario.

The decarbonization of the electrical energy sector is in progress for contrasting the climate changes, with a relevant increase of the Renewable Energy Sources (RES) power plants, mostly in Dispersed Generation (DG). The adequacy and the security of power systems, with a huge penetration of RES in DG is possible with a suitable integration of energy storage. In fact, energy storages are able to provide many different services for long-term adequacy and real time security. In this framework the present paper deals with a Thermal Energy Storage (TES) proposed for power system services. The technology presented is made up of modules containing a bed of fluidizable solid particles, which can store thermal energy from waste heat, process heat and/or from electricity. Stored thermal energy can be released, e.g. as superheated steam, for thermal uses or converted into electricity, by means of steam turbines. Some possible applications are then reported explaining advantages and limits.

The article describes the operational experience of the first industrial application of the Magaldi Ash Recycling (MAR®) system. That installation was commissioned in 2007 at a 2 × 320 MW pulverized coal-fired (PCF) power plant in Italy. The MAR® system is a recycling process that transforms bottom ash into fly ash by returning the “dry” bottom ash to the boiler combustion chamber. The dry bottom ash is removed from beneath the boiler using the MAC® Magaldi Ash Cooler. This technology, with more than 200 installations worldwide on boilers generating more than 70,000 MW, extracts and cools down the bottom ash by means of a small amount of ambient air. Then, the MAR® system conveys the ash back to the coal feeders where it is mixed with coal, milled and reintroduced into the furnace. The effects of the bottom ash reinjection, including the results of a 2-year site investigation, will be discussed in the present paper. The benefits of the MAR® system for PCF power plants are remarkable and can be summarized by the following achievements: 1. Conversion of all bottom ash into saleable fly ash. 2. Complete elimination of costs associated with bottom ash disposal or dedicated slurry system to a bottom ash pond. 3. LOI content reduction in fly ash due to the dilution effect of dry bottom ash (∼8% reduction on average). 4. Fly ash in compliance with international standards: EN 197-1 (cement) and EN 450-1 (concrete) in the EU. 5. Environment respect: mixing fly ash with cement, CO2 emissions decrease. Around 0.9 tons of CO2 are generated from the production of a ton of Portland cement.

Concentrating Solar Power (CSP) systems stem out as a promising technology that has the advantage of an easy integration with thermal energy storage. The current benchmark in the CSP technology is represented by the solar tower receiver with molten salts working as heat transfer fluid. The main drawback of this system is the relatively low working temperature of the molten salts (about 565 °C), which affects the efficiency of the subsequent Rankine cycle for energy production. The use of dense suspensions of solid particles as solar receivers in CSP systems is gaining ever increasing interest, as the dense suspension can simultaneously act as receiver, heat transfer fluid and heat storage medium. Dense suspensions can work at higher temperature with respect to molten salts, even between 1000–1500 °C, without any safety, corrosion, or disposal problem. In this work, different granular materials were investigated to scrutinize their potential use as dense suspensions in directly irradiated Fluidized Bed (FB) reactors. Experimental tests were performed in a directly irradiated FB reactor exposed to a 12 kWel beam-down simulated solar furnace. The dynamics of the directly irradiated FB reactor was analyzed with specific reference to temperature distribution at the surface and in the bulk of the bed as a function of the inlet gas velocity. Material performances were compared by considering the energy required to sustain the fluidization conditions and solar absorption capacity of the granular material.