Cases 2A and 2B deal with photovoltaic panels, table 4 shows field production on the whole year. PV field feeds grid network, so electricity generation can be done when vapour compression chiller is not operating. Conservative shading assumptions is taken for all other results. For case 2A, PV field produces more than the whole vapour compression chiller electricity consumption, thus the auxiliaries consumption will be decreased respectively by 2.04, 3.68 and 6.31 kWh/(m2 year) for Paris, Stockholm and Lisbon.

2.3. More results about case 3.

Simulations run for case 3 have been optimised to minimise boiler gas consumption. For each location it results a panel slope, a storage tank volume. A summary of results dedicated to case 3 is presented in table 5. Figures given are only about heating and cooling production consumption.

Some details should be given on this table: solar energy is the heat collected by the solar field and feeding storage tank; solar fraction is computed following equation 1. Table 6 proposes primary energy savings by net collector area for case 3A. It can be put in relation with table 4 given for case 2 (table 4 values must be multiplied by 2.5 to have primary energy).

Solar energy

Solar fraction =

(Heating load + Chiller hot water consumption)

3. Conclusion

In this work, design and energy performance of different kinds of air conditioning system were analysed. A complete building simulation model was developed with parameters found in IEA ECBCS Annex 48 research project. Heating and cooling emission and distribution systems were also defined as well as heat/cold production devices. This simulation has been run in three different locations. The comparison between three cases gives the potential energy savings of two solar technologies in relation to classical air-conditioning. A first analysis of auxiliaries showed that they have a huge weight in the primary energy balance. For case 1, it varies from 60% in Stockholm to 80% in Lisbon. Therefore it shows an important energy savings potential. When using classical vapour compression chiller and no solar energy, cooling cost less primary energy than heating due to COP higher than 2.5 (converting net energy to primary energy for Belgium). If solar energy conversion technology is implemented, a key point is available area for installing panels. In each case (A or B), primary energy savings are higher using PV panels instead of thermally driven chiller (assisted by solar thermal panels). It is another important result of this study. PV panels are directly connected to grid, then solar energy is use even if the building has low needs (e. g. during the weekend). For case 3.B (12 floors), solar fraction is very low, operating this system consumes more energy than classical air-conditioning. A better control can reduce this trend but a much higher solar fraction is required to save primary energy.

Systems costs have not been approached in this study. If this analysis is performed, the comparison should be done between solar and classical air-conditioning. An important point for PV is that, nowadays, electrical energy can be sold by the producer at a very interesting price. Moreover in some countries, such Belgium, kWh photovoltaic are paid directly at the production, so money can be saved even if electricity is not used in the building. Solar thermal energy has no such high financial incentive.

References

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Thesis, Royal Institute of Technology, KTH, Sweden

[2] TRNSYS simulation studio, Version 16.00.0038 Licensed to Universite of Liege

[3] Stabat P. (2007). IEA48 — Description of Type 1c air-conditioned office buildings for simulation test,.IEA — ECBCS Annex 48 working document

[4] ALESSANDRINI J. M. et al. (2006) Impact de la gestion de l’eclairage et des protections solaires sur la consommation d’energie de batiments de bureaux climatises, Climamed, Lyon, France, 2006

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[6] Water Fired Chiller/Chiller-Heater WFC-S Series: 10, 20 and 30 RT Cooling, http://www. yazakienergy. com/waterfiredperformance. htm

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