U. Jakob1* and S. Saulich1

1 SolarNext AG, Nordstrasse 10, 83253 Rimsting, Germany
* Corresponding Author, ali. iakob@solarenxt. de

Abstract

This paper presents the development and investigation of solar cooling systems based on small-scale sorption heat pumps and chillers, respectively. An ammonia/water absorption chiller with a cooling capacity of 12 kW, the chillii® PSC12, a 17.5 kW water/lithium bromide absorber, the chillii® WFC18 and two water/silica-gel adsorption chillers with cooling capacities of 7.5 and 15 kW, the chillii® STC8 and chillii® STC15, all single effect, are specified as core components of solar cooling systems. Up to now over twenty chillii® Cooling and Solar Cooling Systems respectively are in installed in Germany, Austria, Spain, Italy, Malta, Romania, Syria, Canada, China and Australia. Different kind of applications are realised like for residential buildings, retirement home, office buildings, bank, bakery, greenhouse and institutes. The first experiences and experimental results of the installed solar cooling systems showed that the chillers and the solar cooling system work very well. Keywords: Solar cooling, absorption, adsorption, heat pump, chiller

1. Introduction

Active air-conditioning of buildings is also necessary at European climate conditions, especially in Southern Europe. Therefore the energy consumption for cold and air-conditioning is rising rapidly. Usual electrically driven compressor chillers (split-units) have maximal energy consumptions in peak-load period during the summer. In the last few years even in Europe this regularly leads to overloaded electricity grids. The refrigerants that are currently used in the split-units do not have an ozone depletion potential (ODP) anymore, but they have a considerable global warming potential (GWP), because of leakages of the chiller in the area of 5 to 15 % per year. However, solar cooling systems provide a sustainable active air-conditioning possibility. The sorption heat pumps or chillers use environmentally friendly refrigerants and have only very low electricity demand. Therefore the operating costs of these chillers are very low and the CO2 balance compared to split-units is considerably better. The main advantage of solar cooling is the coincidence of solar irradiation and cooling demand. Particularly the sale figures of split-units with a cooling capacity range up to 5 kW are rising rapidly. In Europe the number of sold units has risen about 53% from

5.3 million in 2004 to predicted 8.1 million in 2007 [1]. The Japan Refrigeration and Air Conditioning Industry Association (JRAIA) has expected a worldwide sales of 74.4 million units in 2007. The market potential for solar cooling systems with small-scale capacity is very large, so that different companies are developing solar cooling systems/kits for the product business [2]. In case active cooling being necessary, the long running times of the chillers are the key for economic efficiency of solar cooling systems. For residential buildings in Central Europe only about 50 to 200 cooling hours occur, whereas in the southern Mediterranean area as well as for some industrial
and office buildings approximately 1,000 full load hours are necessary. An all-season use of renewable energy sources for hot water, space heating and solar cooling is here indispensable.