By Jimmy Hughes,2014-03-30 23:08
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Study the application of a floor system for cooling;; Study (H) CFC free cooling systems using renewable energy (thermal solar particularly);




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    1. Context

    Air conditioning systems are more and more present in new buildings, which increase the consumption of primary energy in these buildings and also increase the peak power necessary for their working. That is why the use of solar energy to cool is being questioned: it could allow to reduce the energy bill of the building and to limit the peak power in summer when solar energy is the most important.

    According to these two remarks, it appears very useful to design solar air conditioning system. 2. Description of the system

    Floor system has been chosen as the inside unit of the solar air conditioning system. A floor heating system is one of the most appropriate systems for direct use of solar energy for space heating due to the relative low temperature of the fluid. It seems that it would be very interesting to use the same principle for space cooling. This technique is interesting since the temperature of the working fluid (12-20?C) is higher than in conventional systems (7 -12?C). Up to now, floor cooling is used connected with classical systems as heat pumps or ground heat exchangers. Floor systems using solar collectors and floor heating in general is a well-established technology. European Standard proposal on how to design and size floor heating systems exists. Efficiency of the control together with low temperature energy sources have also been tested. Floor cooling is, however, a relative new idea, which only have been used in some projects in Europe. There is no standardised method on how to design these systems. The control is very important to avoid problems with condensation and at the same time to obtain maximum cooling. The ventilation may influence the capacity but also the comfort by floor cooling, but no information is available. In order to use solar energy to cool some premises, an interface between solar collectors and floor cooling system is necessary. That is the function of the absorption heat pump.

    Heating/cooling system with the absorption heat pump

    This AHP should use two chemical components to run: water and lithium bromide (LiBr). Other systems exist which use for instance ammonia and water. But this couple presents two main disadvantages in relation with the previous one: ammonia is not an environmental friendly element, and the level of temperature necessary to make run an AHP with this couple is far higher than the one necessary with the couple water and LiBr.

    Some LiBr AHP already exist: a study of the market allowed to determine the actual supply of the LiBr AHP. Several manufacturers already propose some products:


    SUNTHERM (USA) 30 kW

    SANYO (Japan) 100 kW

    YAZAKY (Japan USA) 336 kW to 1 666 kW

    AROACE (YAZAKY technology) 35 kW to 115 kW

    TRANE (USA) 300 to 500 kW

    This project aims at providing this technology to medium size building where no European manufacturer is already present. To develop this technology in Europe is of strategic importance. To obtain sufficient performances on the AHP, it is necessary to provide to it high temperature water (about 80?C min). It is thus necessary to provide some efficient solar collectors in this range of temperature. Furthermore, it is necessary to obtain these performances with not too expensive collectors. Two types of collectors have been envisaged : evacuated collectors and flat plate collectors.

3. Objectives

    The objectives of this project are to:

    ; Study the application of a floor system for cooling;

    ; Study (H) CFC free cooling systems using renewable energy (thermal solar particularly); ; Study high performance solar thermal collectors coupled with the cooling unit; ; Study the coupling between the cooling unit and the floor system;

    ; Compare technically and economically the floor cooling system with a conventional air system; ; Establish design and application guidelines for the systems.

    Expected technical achievements are the following ones:

    ; Characteristics of flat plate collectors: B > 0.75 - K < 5 W / m? K;

    ; Selective coating environmentally friend with no chromium;

    ; Efficiency of absorption heat pump of 60 % at 90?C;

     Heat exchange coefficient (radiation and convection) between floor surface and room operative ;

    temperature 7 W / m? K;

    ; Quantification of the influence of the method of ventilation (mixed, displacement) on the heat

    exchange coefficient and comfort (cooling capacity);

    ; Proposal for a standard design method for a floor cooling system;

    ; A strategy for optimal control of a floor cooling system.

    4. Work progress

    Up to now the following tasks have been achieved:

    ; Study of the solar collectors. The work achieved with Jacques GIORDANO Industries allowed

    to reach the performances defined in the objectives. It could be possible to work with flat plate

    collectors to reach temperature around 80 ?C in summer.

    ; Study of floor cooling systems. Several tests have been achieved in a climatic cell by using a

    floor system from VELTA. These tests allowed to study the influence of several parameters

    (water temperature, outside temperature, flow…) on the performances of the floor system. It

    also allowed to study the reaction of the control system to several extreme conditions. ; Study of the absorption heat pump. This task is always under achievement. A prototype has

    been made by ZAE BAYERN. This prototype will be tested very soon by COSTIC in order to

    evaluate the performances according to several outside conditions (solar collectors temperature,

    floor temperature, cooling tower temperature). Preliminary tests have been realized. The

    performances obtained are around an efficiency (COP) of 0.7 (power at the evaporator divided

    by power at the generator) and a cooling power around 8 to 9 kW.

    ; Study of the complete systems. The prototype will be connected by COSTIC with solar

    collectors and a cooling floor in order to study its working in “real” conditions. Up to now

    numerical simulations have been realized by Observatory of Athens.

    The work programme will be ended by the end of September 2001.

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