An extended version of the SolarCoolingLight calculation tool was created at Fraunhofer ISE, Freiburg. While the identical structure of the combined input file containing meteorological and load data is used, the tool allows more distinction between different cooling technologies and system designs. The desired system configuration may be selected from 11 pre-defined configurations, covering solar assisted air-conditioning systems either with a desiccant cooling system or with a thermally driven chiller and with different types of a backup system. As a further advantage, a reference system may be selected and automatically, a comparison of investment cost, annual cost and other key figures between the solar assisted system and the reference system is generated by running the program. Figure 4 shows two configurations, selected from the program: a desiccant cooling system and a reference system, consisting of an air handling unit with a compression chiller as cold backup.

Although for each hour of the year a complete energy balance including auxiliary energy consumption (e. g., pumps, fans) is carried out in order to determine the annual performance figures, the tool is developed for pre-design studies, as no modifications in the system control can be applied and for the chillers and desiccant cooling systems global performance values can be specified only without considering part-load behaviour.

Nevertheless, the tool is useful for comparative studies, like the study on the energy — economic performance of solar assisted air-conditioning in the SACE-project. Within this study, an energetic and economic assessment of different solar cooling technologies for European sites and for different types of application was performed.

For each investigated system configuration, a reference system was defined and the energetic performance and costs relative to the reference system were compared. Figure 5 shows a result, extracted from this study. For a desiccant system configuration and a reference system as shown in Figure 4, the annual cost (annual payments for investment,

operation and maintenance) are drawn versus the investment cost (first cost) of the plant. Both, annual cost and investment cost are given as a percentage of the corresponding cost of the reference system. The calculation was repeated for the same application (a lecture room), but located at three different sites: Freiburg (Germany), Madrid (Spain) and Palermo (Italy).

FREIBURG_FPC_DEC MADRID_FPC_DEC —A— PALERMO SAC DEC

— 100% annual cost

( = break-even condition)

Figure 5: Simulation results from the SACE economic study/3/: Annual cost versus investment cost of a desiccant cooling system at three European locations (Palermo, Madrid and Freiburg). The costs are given in percent of the costs of the reference system (see Figure 4). The actual first cost correspond to the right hand end-positions of each line; the required first cost to obtain competitiveness in the annual cost compared to the reference system (100% annual cost, relative to reference) are marked by the vertical dashed lines for each site. In the systems at Freiburg and Madrid, a common flat plate water collector (FPC) is assumed, while at Palermo site a solar air collector (SAC) is applied.

The figure reveals the following information, explained for the system located at Freiburg: the investment cost under current market prices are expected to be approx. 140% of the investment cost of the reference system, referring to 115% of the reference systems annual cost. If these annual cost are not allowed to exceed the annual cost of the reference system
(100%), the relative first cost of the solar assisted cooling system should not rise above approx. 113%. The difference in first cost between this value and the initial value of 140% has to be overcome by funding measures and by a reduction of component and installation cost, but is also subject to modifications in the running cost of the system (e. g. an increase in electricity cost), to make the system economically competitive to conventional system solutions. A further decrease in investment cost down to identical investment cost of the reference system (first cost of 100%) finally would lead to annual cost of only 91% compared to the reference system annual cost and hence, economic benefits could be expected beside primary energy savings.

The EasySolarCooling software has been designed for internal use only and is employed within pre-feasibility studies on solar assisted air conditioning. It will be continuously developed according to needs in project work.