M. Krause*, C. Lauterbach, J. Kaiser, D. Schmidt

1 Fraunhofer Institute for Building Physics, Gottschalkstr. 28a, 34127 Kassel, Germany
* Corresponding Author, michael. krause@ibp. fraunhofer. de

Abstract

The present paper deals with the potentials of using solar thermal driven systems for air conditioning of office buildings and central server rooms. For this, a system model consisting of a building according to passive house standard, a server room and a solar air conditioning system using absorption chillers was developed for TRNSYS and evaluated regarding its thermal behaviour. Hereby, the energy demand of the building as well as the server room was determined. The investigations showed that for such a building, an active cooling system can increase the comfort in the office rooms significantly, even for mild climates. It has been proven that using solar air conditioning systems in combination with free cooling for server cooling is a promising concept and can lead to significant reductions of primary energy consumptions. However, special measures have to be addressed to increase the solar fraction of the system up to suitable levels.

Keywords: solar air conditioning, buildings, server cooling, simulations

1. Introduction

Within the European Union, the building sector is responsible for more than 40 % of the overal energy consumption. In order to reduce greenhouse gas emissions of 50% by 2050 [1], a distinctive reduction of the energy consumption in the building sector is essential. A promising and already established approach is the passive house concept. Here, a high insulation standard is combined with large south facing transparent areas and ventilation systems with high efficient heat recovery to increase solar gains and reduce the heating demand. However, high solar and internal gains are sometimes even in mild climates responsible for uncomfortable indoor temperatures [2]. As a result, the market for air conditioning systems and thus the energy consumption has been increasing within the last decades [3].

In addition, independent on the location of the building, computer centres and server rooms show a rapidly increasing cooling demand. According to [4], the electricity consumption of server rooms can be responsible for up to 60% of the overall electricity consumption within such buildings, half of which is caused by the cooling and ventilation demand and the resulting use of conventional vapour compression chillers.

Regarding this, the present paper is dealing with the use of alternative cooling technologies for buildings and server rooms. One promising option for this is the integration of thermal driven cooling technologies like absorption or adsorption chillers in combination with solar thermal systems. On overview of existing technologies for solar air conditioning can be found in [5].

Within the present investigations, a model of a passive office building and its server room was implemented in the simulation program TRNSYS. With this, the heating and cooling energy demand was evaluated for the defined reference case as well as for different variations regarding insulation standard, shading strategy, infiltration rate and cooling strategy. In addition, a thermally driven cooling system for the building and the server room was integrated in model. With these

1

models, possibilities to cool passive houses and server rooms with solar thermal cooling systems have been investigated and compared to conventional cooling systems and strategies.