Active Thermal Cooling Technologies - Low Energy Cooling for Sustainable Buildings - page 152

120

Dehumidification efficiency

100

80

Heat exchanger efficiency

60

40

20

0

0 0.2 0.4 0.6 0.8 1

Efficiency

Figure 5.43 Auxiliary energy demand for varying heat recovery efficiencies (at constant dehumidifica-
tion and humidifier efficiency both of 80%) and for varying sorption wheel dehumidification efficiencies
(at constant heat recovery efficiency of 62% and humidification efficiency of 80%)

5.2.6 Cost Analysis

The costs for desiccant cooling units are often full system costs, as the desiccant unit
already includes parts of the conventional distribution system such as fans, fresh air
channels, exhaust air channels, filters, etc. Furthermore, the machine itself contains
humidifiers and heat exchangers, which are also available when a conventional air
handling unit is installed.
As an example the total capital, consumption and operation-related costs were anal-
ysed for the Althengstett demonstration system with a volume flow of 18 000m 3 h − 1 .
The investment costs are dominated by the desiccant unit itself and its system
integration, which together comprise 72% of the total investment costs. The solar
air collector field including tubing and mounting contributes only 14% of the total
investment costs at 300 euros per square metre of collector area (see Figure 5.44).
The total investment costs are D 12.4 per m 3 h − 1 . For another well-analysed system of
the IHK in Freiburg, Germany, with a smaller volume flow of 10 000m 3 h − 1 the costs
were higher at D 16.6 per m 3 h − 1 . Also in this system, the DEC unit together with the
air channels, mounting and control comprised about two-thirds of the total investment
costs (46% for the unit itself, 17% for the mounting and channels and 6% for control).
The solar air collector field was responsible for 10% of the total costs (Hindenburg,
2002). A third system with 105m 2 of solar air collectors connected in series to a
ventilated photovoltaic fa¸ade and shed roof was constructed in Mataro, Spain, with
a total volume flow of 12 000m 3 h − 1 . As a part of a European Union demonstration
project, the unit was constructed in Germany and then mounted and connected to the
existing building management system by the Spanish project partners. Here the DCS
unit comprised 33% of the total costs of D 179 300, and a high amount of 23%was used