• Energy Research

Abstract In this paper, a general mathematical model for the dynamic simulation of a single-effect LiBr/water absorption chiller is presented. The model is based on mass and energy balances applied to the internal components of the machine, and it accounts for the non-steady behaviour due to thermal and mass storage in the components. The validation of the mathematical model is performed through experimental data collected on a commercial small-capacity water-cooled unit. Due to the peculiar technology adopted in the real chiller, a special effort was made to identify the appropriate values of the main physical parameters. The validation of the model is based on the values of the water temperature at the outlet of the machine, as no measurement inside the machine was possible; anyway, a consistency analysis applied to the internal parameters is also presented. The agreement between experimental and simulated results is very good, both on a daily and on a seasonal basis.

Solar thermal energy storage is used in many applications, from building to concentrating solar power plants and industry. The temperature levels encountered range from ambient temperature to more than 1000 °C, and operating times range from a few hours to several months. This paper reviews different types of solar thermal energy storage (sensible heat, latent heat, and thermochemical storage) for low- (40–120 °C) and medium-to-high-temperature (120–1000 °C) applications.

AbstractThe heat storage by absorption process that is studied in the paper is devoted to building heating. A prototype has been built and tested in static and dynamic operating conditions that are compatible with domestic solar thermal collectors. The charging process has been proved successful. Absorption during the discharging phase is also verified. However, some problems related to the heat exchanger design have not allowed to observe the heat release as expected.

In the past decade, long-term sorption and thermochemical heat storage has generated lot of interest. This paper presents the state of the art in this field of research, materials used in these systems and technological difficulties that researchers are set against. An emphasis is put on recent demonstrative projects including absorption and adsorption for long-term solar energy storage. It emerges that considerable breakthrough have been made. Even though there is no mature long-term sorption or thermochemical energy storage yet, primarily due to the high cost of materials, the suitability of this technology to long-term storage remains its main power of attracting.

International audience

Abstract This study presents a new plate-type falling film absorber design, consisting in a vertical grooved falling film absorber. The grooves are designed to obtain good absorber plate wettability, even at a low solution flow rate, resulting in a laminar solution flow regime. Using experimental and numerical tools, the vapor absorption on a LiBr falling film solution is characterized for different operating conditions. The impact of absorber length, cooling water inlet temperature, absorber water vapor pressure, solution inlet temperature, LiBr mass fraction and flow rate is investigated. Experimentally, a high absorption rate is achieved: as high as 7·10 −3 kg s −1 m −2 . Moreover, a 1D stationary model of water vapor absorption in a laminar vertical falling film is introduced and validated. Numerical investigations allow defining the absorber effectiveness for a wide range of operating conditions.

International audience