Forschungs- & Entwicklungsinformationsdienst der Gemeinschaft - CORDIS

Final Activity Report Summary - SOLAC (Investigations of the absorber component of a solar desiccant air conditioning system)

The research project is dealing with system simulations of a solar desiccant air conditioning system with the simulation tool TRNSYS. A complete heating and cooling system was modelled. The energy savings potential of solar thermal driven air-conditioning systems for the application in single family houses was investigated, focussed on open cycle desiccative and evaporative systems. Three different locations were taken into account for the simulation study, i.e. locations in Central Europe (Zurich), Australia (Adelaide), and Canada (Ottawa). Reference conditions were defined for these three locations.

In a first step, climatisation load profiles were examined for a reference building at the particular locations under different constraints, like the ventilation rate, set temperature, and relative humidity. These constrains were derived from user profiles, e.g. high comfort demands or energy saving mode. It was found that the ventilation rate has a high impact on the dehumidification load but only a small impact on the sensitive cooling load for the building type examined.

In a second step, an estimation method based on hourly averaged time series for the climatisation load and for the solar radiation was used to calculate the fractional energy savings of the investigated system compared to a conventional air-conditioning system. It was found that a very high solar fraction of up to 100 % can be achieved with a collector area of 14 m2 and an 860 l storage volume - this corresponds to a typical installation for combi systems in single family houses.

Finally, more detailed simulations were carried out based on models for the solar thermal system, the building and the air-conditioning system, to dimension the components and reveal suitable system configurations. The model of the desiccant air-conditioner developed was connected to a simulation model for a typical solar thermal combi system for domestic hot water preparation and space heating. Parameter studies were undertaken, varying e.g. the collector area and the storage size. The system simulation results were evaluated concerning fractional energy savings, comfort demands and operating hours of the solar driven air-conditioning system.

Fractional energy savings in the range of 18 to 32 % were revealed for the location Zurich, of 25 to 42 % for Ottawa, and of 59 to 69 % for Adelaide. Moreover, it turned out that for all three locations the cooling system is operating without dehumidification most of the time. Instead, only an evaporative cooling device is used, if humidification is not necessary. Due to these results, additional simulations without humidity control were carried out, with an air-conditioning system consisting solely of an indirect evaporative cooler. It turned out that in Zurich and Adelaide the employment of such a system leads to room air conditions that suit the comfort demands in 90 % and 96 % of the total operation time, respectively.

It can be concluded that in the single family house sector, the investigated systems operating in the desiccant mode have a high energy saving potential solely for very humid climates, to be found for example at the Canadian location taken into account for the simulations. In contrast, for central European locations, the study revealed that an air-conditioning system consisting of an indirect evaporative cooler only, is sufficient in order to meet comfort demands as given in technical regulations. No additional dehumidification device is needed for relatively dry climatic conditions.

Reported by

Kurt-Wolters-Strasse 3
34125 KASSEL
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