State-of-Art of Thermochemical Heat Storage Systems

Abstract

A combined heat and power (CHP) or cogeneration plant simultaneously produces thermal and electrical energy, primarily to meet industry and household demand. As we focus on household's application, we talk about a residential micro-CHP. Micro-CHP plants have a higher energy efficiency than conventional (without coupling thermal and power) thermal power systems, leading to a decreased environmental impact, in other words, reduced greenhouse gas emission (CO 2 , N 2 O, CH 4) and a significant increase of economic profitability (Yusta et al. 2008). They can also decrease fuel consumption by 30 % compared with decoupled production in conventional power plants (Lund et al. 2005). The use of micro-CHP plants has been recognised as crucial by the European Parliament for the achievement of the Kyoto Protocol objectives, and consequently, legislation to encourage the use of cogeneration has been approved. These regulations dictate the parameters that define a plant as a cogeneration power plant (Tina and Passarello 2012). Installation of thermal energy storage systems, particularly thermochemical heat storage systems (THSS) allow heat accumulation, which increases the flexi-bility of heat and electricity production in the power plant (Katulić et al. 2014). In a micro-CHP with regulated steam extraction turbines, at constant load, an increase in thermal energy production reduces the amount of electrical energy production. The main objective of THSS in a micro-CHP system is to support the simultaneous of thermal and electrical energy production. A THSS can store thermal energy during phases when it can be produced in excess for use when it cannot be produced to meet the heat demand or when its production is not a priority. Figure 2.1 shows an example of such system. Using THSS, thermal energy can be accumulated while electricity market prices are low and discharged while prices are high (i.e., when it is more profitable to produce and sell larger quantities of electrical energy) (Katulić et al. 2014) via a © Springer International Publishing Switzerland 2016 A. Fopah Lele, A Thermochemical Heat Storage System for Households, Springer Theses, DOI 10.1007/978-3-319-41228-3_2 15 conversion chain-like electricity → heat → chemical → heat → electricity. Heat storage system also makes it possible to operate production units at more efficient loads. There are three mechanisms of heat accumulation in THSS: (a) increasing the temperature of a working fluid (heat carrier) w…