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Construction and field test activities of an innovative single-room solar driven air-conditioning system

Final Activity Report Summary - ISSA (Construction and field test activities of an innovative single-room solar driven air-conditioning system)

Over the course of its first year, the first phase of the project was completed and the second was initiated. The work was carried out according to the times/calendar and the modalities indicated in the original proposal. The final version of the system plan was made available only after thorough analysis, as well as definitions for control and monitor systems. The actual study of the plant began after the prerequisite individualisation of the venues (where the machines will be installed) and the offices (to be air-conditioned).

Numerous plant configurations were taken into consideration and analysed with the aim of determining a solution that would guarantee the maximum performance, but at the same time limited costs and simple installation. The principal circuit elements used interchangeably were:
- Solar collectors ( flat plates, vacuum tubes);
- Thermally driven chiller ( absorption, adsorption technologies) with or without evaporating tower;
- Cold distribution terminals ( fan coils, radiative floor).

In coherence with the project's objectives, the possibilities for a direct connection between the source of heat (solar collectors) and the heat pump was investigated. The analysis of the shadows and the calculation of the thermal load of the building (with the aid of dynamic simulation software TRNSYS) provided the base for the following phase of project definition and design of the plant.

The principal technical of the final version of the plant data is listed as follows:
- Total area of the solar collector array 19.8 square meters using vacuum tubes collectors;
- 4.5 kW absorption chiller with LiBr-H2O working couple;
- Possibility to use two hot water storages (1.500 litres and 100 litres for split configuration);

During the same phase of the project a monitor system was studied to apply to the plant. The choice of equipment was made with particular care, as was the study of how to position the transducers. The aim was two-fold: to allow the reading of the principal operational parameters in each part of the plant, and to guarantee a correct evaluation of the energetic performance. A data logger with 340-channels multiplexers will be used to acquire data using four flow maters and 13 temperature sensors. The next step was to define a control system able to guarantee a better performance of the plant. The operation of the solar circuit is controlled by a specific controller provided by the company which constructs the solar panels.

The actual working of the distribution circuit are managed by another control unit purposely constructed which is linked both to the ambient thermostats and the internal control of the absorption chiller.

At the conclusion of the first phase, the second began in the 7th month with the first steps towards installation in the building already decided. This included the write up of the detailed equipment list relative to the plant and acquisition of a few parts of equipment, in particular the solar collectors and the chiller.

In the second project phase, experimental activities on the different configurations of the system have been carried out. The tests proved the suitability of such concept for small residential applications.