The criteria was set out in Singapore that the energy that was used in gardens by the bays was not more than that of a conventional Singapore office block.
We had to get precise humidity conditions and temperature variation differences. The entropy [Humidity] in the air [of singapore] is very high. From the outset the concern was a way of reducing the humidity in the air and the solution was to use liquid desiccant to dry the air. If we just cooled down the hot air at high humidity it would be very difficult to handle. So this is why we pass the air through the liquid desiccant [lithium chloride], a drying system. Our issue is what do you do with this liquid again. When you have these pads with liquid desiccant running down them, the volume of air on these pads increase so you have a weaker solution of desiccant at the bottom which is ‘ Runny’ rather than concentrated desiccant. A solution to concentrate the desiccant once more is to boil it. Our initial design was to use solar energy so you would have a concentrated desiccant store and a weak desiccant store. So when Singapore is sunny the solar panels would heat up the weak desiccant and the steam would leave via the super trees.
Solar energy in Singapore you get a long period of when its cloud , particularly when the smog from Indonesia obscures the sun for weeks at a time. When we worked out how much desiccant that we needed to filter the air, there was not enough constant solar energy to be had in order to re concentrate it. We also found out that when the sun eventually comes out you get a sudden surge in energy which could potentially boil the desiccant. The Solution to this was to make most of the 2 year pruning of Singapore and also wooden packing waste from the harbour nearby. With this waste it could be use a constant fuel to concentrate the desiccant and drive the chillers (11 articulated lorries worth of pruning wood). The boiler used for this project cost millions of dollars.
The Eden project was always cost conscious, that is why all their air handling units sit outside. It is not a sophisticated design in terms of environmentally engineered. Blow in air and see what happens. The difference in terms of plants rooms and services is that we very strategic when it came to the placement and concealment of the units, whereas on our visit to Eden it was evident that they placed the units wherever it fell. We had a big injection of money from the government which allowed us to concentrate on the best solutions such as these .
Singapore regulations do allow you to have glass roofs. we had to have waivers for the project to be allowed to build it. We had to use our carbon energy from the waste system argument in order to obtain these waivers
our studies showed that there was only the need for the solar shading 8% of the annual hours of the year but in reality they are deployed very rarely due to the fact the glass is not cleaned as often as we had hoped.
the competition design was a structure with big set of fins with the glass hanging off. We imagined that the fins would offer the shading. In fact the shading would be too much. So we looked at hollowing out the structure with a truss arrangement with an open mesh, but that obscured to much light. So then we finally looked at a grid shell structure which is quit week by lateral forces. So the primary arches are used to prop up the grid shell so it doesn’t fall over. It becomes a very skinny structure so that we you are inside there is not a lot of structure in the way of the glass.
Both Biomes are self shaded on the north side due to their form. It is down to where the sun sits in the sky. The specially selected glass that was used actually deflects light at certain angles. Also typically sun at a high angle of incident of glass a lot of the light is reflected including radiation.
When looking at the operative temperature of the building we were concerned of 80% for the plants 20% for the people. 1100 watts of sunlight in Singapore. Inside you have around 330 watts of sunshine. If you are standing still in sunlight you feel uncomfortable. The programme of the building makes you move through the space and so evaporative evaporation happens and keeps you cool. So there are no complaints in the building.
Our studies have shown that the plants in both of the biomes do not mind being a bit cooler. We had to move some diffusers away from some of the plants as they sometimes mistake it for winter and go into hibernation, but they have managed to keep both of the biomes flourishing and operative at 22C which is less that we want but it is much more comforting for the visitors. Obviously this additional cooling would be a problem if you had to pay for the electricity but when it comes from the waste that was going to be incinerated away, they don’t really mind.
We did quite a bit of research on ETFE. The main thing that we looked at was the ability to coat ETFE with a selective coating. We wanted to let in as much light in but restrict the amount of heat. The manufacturers of ETFE said they could coat the ETFE, but we were concerned that the coating could be scratch of with the movement of the wind etc. With the glass having the selective coating on the inside of the panes it was safer. Another reason was that aesthetically it didn’t look right with the form . And thirdly Singapore is known for heavy rain and the noise inside would be very worrying. With glass its quite exciting but with ETFE it would be very loud. The final reason is the client wanted the project to feel like permanent piece of architecture and believed ETFE doesn’t look permanent.
The Alpine house was designed to be natural ventilated however this building was not designed to be naturally ventilated. It is not stack ventilation as such. The height helps with the stratification of the air but the height overall comes through the height which is needed for the parabolic arches for the area and also is taken from the aesthetic design of Wilkinson Eyre.
From the very start I wanted the building to use displacement ventilation. We were very Keen not to have ducts running up height. When we first ran the CFD models we found that the temperature we were getting high up at mountain level was uncomfortable. This was when we putting air in at lower and middle level.
One issue we had with ventilation was to get air to the flower garden which sits in the cool flower conservatories. There is limited amount of air cooling, just around the perimeters. So they added more diffusers so it keeps it cool. We also suggesting they should buy fans on wheels to blow at trees during the night time. trees are stressed in nature during the wind and spread roots to compensate. we had issues with kew where trees just fell over because they didnt have many strong roots.