| Each chamber is equipped with separate climate control and ventilation systems, which control the level of light, temperature and humidity inside the growth chambers. The control systems are also capable of simulating the diurnal and annual cycle of all main plant growth parameters in a near-natural manner. This means that short duration peak values can be included in experiments and the effects of long-term transients can be studied.
Lamp arrangement. Large picture
Artificial and natural light
The glass roofs of the chambers allow for the mixing of sunlight supplied with artificial light fixtures mounted on mobile light racks. The light racks are equipped with 40, high pressure mercury lamps producing a photosynthetic photon flux density at canopy height of up to 1000 µmol m-2 sec-1. This is enough to create "daylight" even at night, and allow experiments with extended or shortened day/night periods or changed annual cycles to be conducted.
Temperature control
Basic temperature control is supplied from cooling and heating radiators in the ventilation system for each chamber. The temperature in each chamber can be controlled between -5 0C and 40 0C and can be programmed to simulate diurnal or faster cycles. Chamber temperature can be changed from -5 0C to 40 0C in 30 minutes.
Additional heat is produced when the lamps are on, and the space surrounding the lights is prevented from overheating by cool air. When the lamps are off in winter the lighting space is protected from frost damage by heating radiators in the central ventilation system. Cooling is provided by a central cooling compressor and a circulating brine. The compressor is a computer controlled screw compressor with an energy saving floating temperature setting that depends on the low temperature setting of the chambers.
Ventilation and climatic conditioning systems. Large picture
Humidity control
Air humidity is controlled for each chamber by interchange between the cooling and heating radiators in the ventilation system. Additional humidity can be supplied from a water vapor generating system in each chamber.
Experimental Conditions in RERAF
Overview over the range in standard climatic conditions in RERAF.
| |
"Danish" climate |
"World" climate |
"Subarctic" climate |
| Temperature |
6 - 27 ° C |
6 - 40 ° C |
-5 - 6 ° C |
| Relative humidity |
20 - 90 % |
20 - 90 % |
50 - 90 % |
| Photon flux density |
1000 µmol m-2 s-1 |
1000 µmol m-2 s-1 |
1000 µmol m-2 s-1 |
| Soil temperature |
0 - 15 ° C |
10 - 25 ° C |
-5 - 6 ° C |
| Wind speed (standard) |
0.3 m s-1 |
0.3 m s-1 |
0.3 m s-1 |
RERAF growth chambers. One chamber with closed shutters and one without artificial light. Large picture
Shutters and curtains
A special computer controlled shutter and curtain arrangement makes it possible to combine sunlight and artificial light. The shutter system also makes it possible to simulate the diurnal light cycle: night - sunrise - daylight - and sunset, in a near natural, smooth change without "steps". Furthermore the curtain system makes it possible to reduce the light level in the chambers to complete darkness even during daytime. The shift from full light intensity to complete darkness can be made within 2 minutes.
Air locks and pressure zones
Air locks are available at two different levels; in the central building in front of the chamber wings, and, if demanded, in front of each individual chamber unit. RERAF is generally operated in vacuum mode, but can be changed to pressure mode in specific chambers. Different pressure zones can be established depending on experimental needs. RERAF is gas tight which allows for experiments with transgenic organisms and for exposure of plants and model ecosystems to gaseous air pollutants.
Air quality
Several filter systems have been installed in order to protect the outside environment or the experiments in RERAF. The air is normally re-circulated within each chamber unit, but between 0 and 5% of chamber air can be substituted with fresh, filtered air from outside. The air intake and outlet for both the building and for the individual chambers can be filtered with charcoal, bacterial, fungal, or pollen grade filters. Special mixtures of gases such as carbon dioxide, ozone, nitrogen oxides etc. can be supplied separately or in combination to each chamber.
Control and security computer systems
In RERAF, each growth chamber is equipped with a separate computer, and separate equipment for controlling the climate within the chamber. Information on details of the set-up and other environmental conditions for each chamber in an experiment can be downloaded from the participating scientist’s own computer. The chamber control computer can accommodate preset climatic conditions for up to one year. Scientists can connect with the control computer at any time and monitor their experiments.
Each chamber is equipped with an independent environmental monitoring system, where separate sensors are connected to PLCs. Information from the PLCs are then fed into a central computer. If conditions in a chamber exceed pre-set limits for an experiment, warning lights are turned on and an alarm procedure is initiated.
A video link is established to all chambers making it possible for the scientist to look into the chambers from their own office computer.
Certifications
RERAF chambers are certified for experiments with transgenic organisms and for experiments with radioisotopes. Thus, both stable and radioactive isotope techniques can be included in experiments whenever feasible. |