For the development of standardized solar cooling systems it is indispensable to use a system controller for the complete system. The previous solar cooling demonstration and pilot projects are using several single controllers e. g. for the solar thermal system, for the chiller, for the recooler and for the cold or heat distribution, which are together cost intensive and are not always operating optimal together. The alternative was until now an expensive SPS controller which had to be programmed for each single case. Because of that the SolarNext has decided in the year 2007 to develop an own system controller for the whole system (Fig. 2.), which has an influence from the automotive sector and is cheap and system oriented.

The functional range of the chillii® System Controller (Fig. 3.) contains the control of different heat sources (e. g. solar heat, CHP waste heat, district heat, etc.), the back-up system (e. g. controllable oil/gas boiler or not controllable wood boiler or exhaust gas heat recovery), the storage management (heat and cold storage), the hot water, the chiller (e. g. chillii® STC8, PSC12, STC15, WFC18, EAW SE15, Yazaki WFC-SC10, etc.) and the re-cooling (e. g. wet, dry, and hybrid cooler) as well as heating and cooling circuits. The chillii® System Controller is the first system controller for thermal cooling and heating systems that controls many large hydraulic variables with one device. So the highest system efficiency is reached with the needed energy generation with priority in regenerative energy sources, optimized running of chillers as well as the re-cooling with speed control of the pumps and the re-cooling ventilator.

2.

Solar Cooling Systems

During the last few years a few companies in the solar business have positioned on the market as system providers for solar cooling. In the small scale capacity range up to 30kW there is for example the company SolarNext with its chillii® Solar Cooling Kits and Systems respectively based on the chillii® STC8, chillii® PSC12, chillii® STC 15, chillii® WFC18 and absorption chillers from the company EAW and Yazaki. Further companies like e. g. Enus, Phonix, Schuco and Solution also offer solar cooling systems with the different chillers. The solar cooling systems basically contain solar thermal collectors with attachment, hot water storage, pump-sets, a chiller, a re-cooler, partly cold water storage and a control unit. Fig. 4. shows as an example the chillii® Cooling Kit 18, which can be supplemented by a solar package, a cold storage package, a cold distribution package, etc. The cooling kits are developed for the European market, whereas other re-coolers can be offered according to the country (e. g. in Spain a dry re-cooler).

Fig. 4. chillii® Cooling Kit 18 (source: SolarNext).

The average value of the specific collector surface of all until the year 2006 installed solar cooling systems in Europe is about 3 m2/kW. A value from 3.5 to 4.5 m2/kW can be considered as a reference value for thermal driven absorption and adsorption chillers. But these values are only rough reference values and can never replace the detailed design and simulation of a system. The specific total costs of installed solar cooling systems in Europe are so far between 5,000 and 8,000 EUR/kW. For 2008 system prices of 4,500 EUR/kW are reached, in the future 3,000 EUR/kW are expected.