Active Thermal Cooling Technologies - Low Energy Cooling for Sustainable Buildings - page 142

The total electrical power consumption for the fans and wheel motors is 17.2 kW.
A conventional air-conditioning system without an exhaust air humidifier, sorption
wheel and air collector field would have about 4 kW less electrical power demand. For
1167 operating hours in cooling mode the additional electrical energy consumption for
the desiccant unit is 4668 kWh producing a total of 34 710 kWh. If the total electrical
energy consumption is considered, about 20 000 kWh of electrical energy is needed.
This is a consequence of an air-based cooling distribution system. The situation can
only be improved if variable volume flows are possible at partial load conditions.
However, as the pollutant levels are very high in the plastics factory, the air volume
flows had to be kept high to maintain a reasonable air quality. In addition to the 1167 h
in active cooling mode, 2473 h of operating time was in free cooling or free ventilation
mode, also requiring electrical energy for the fan operation.

Air Collector and System Performance

The low heating energy contribution of the solar thermal air collector of about
70 kWhm − 2 a − 1 was analysed in more detail for the month of July, where data avail-
ability was highest at 83% and there were no more problems with operation the
humidifier. From a total of 421 operating hours, 83 hours needed full regeneration
mode, but 90 hours pure evaporative cooling was sufficient. The dominant operating
mode even in July was free cooling with 178 operating hours (see Figure 5.31).

178

200

150

90

83

100

40

50

11 10

0

0

[1] [2] [3] [4] [5] [6] [7]

Index

[7] NOT DEFINED [6] COOLING BY REGENERATION

[5] COOLING BY HUMIDIFIERS [4] FREE VENTILATION

[3] HEAT RECOVERY EXHAUST AIR [2] HEAT RECOVERY REG. AIR

[1] AIR HEATING SYSTEM

[7]

[6]

[5]

[4]

[3]

[2]

[1]

[]

01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

31

Day of month in July

Figure 5.31 Operating hours of different desiccant cooling modes for all days in July