Claudia Fleischmann

Unfolding the Project of a Green Node in an Industrial Landscape

Urban Context

The findings of the research surrounding the ma- terial of glass conclude in the establishment of a particular project that is connected to the se- condary production line of glass in Switzerland. The idea to make the heat somehow visible, while still connecting it to the agricultural lands- cape of Switzerland resolved in the setting of a greenhouse complex, that offer the availability of different vegetables and fruits, as well as offer services to the neighbourhood and urban context. The project is embedded in a tringle of three Swiss cities, Gossau, St. Gallen and Herisau. In an immediate context the project connects to an industrial zone and is directly linked to the Glas Trösch facility. As mentioned, in concept, the greenhouse complex is operating on a district heating system, that is connected to the heat ex- hausted by the ovens.

The site sits not only in the industrial landscape, it also connects into a leisure network of national bike routes (in red) and national hiking paths (in yellow). The greenhouse project is easily accessible by public and private transport.

Formal Considerations

In intensive greenhouse cultivation the form of Venlo Greenhouses has become the standard, due to their high light transmission rate. Light is the most important production factor for the growth of plants, as 1% more transmitted light equals to 1% more production mass. The Venlo construction allows tall building height, which is important for a stable climate in the green- houses which ensure the health of the cultures. The heights of the different building parts differ in terms of their function.

Spatial allocation and organisation

The building is organised on a grid, whereas the heating central provides the spine for the buil- ding. Along an axis, the heating pipes build up the framework. In relation to the heating system and the growing distance from the heating cen- tral, the spaces are organised depending on their heating demands.

Estimated heating Volume

Based on statements from the two visits, I as- sume the heat excess to the glass processing is double than they need to heat the indoor spaces to a comfortable temperature, which is between 20-24C°. The total volume to be heated I esti- mate around 360’000 m3, which are large vo- lumes, one of them resembling a glass house architecture. The excess heat can then be easily used to heat the greenhouses on the opposite street, which a smaller footprint.

A similar principle has already been proven in Wittenberg, Germany, where a fertilizer factory heat 7 ha of greenhouses with its excess heat, or in Belgium, where the META Project is heated by the heat of waste incinerator plant.

To further base the size of the greenhouses placed opposite of the glass processing factory, it is worth looking into the primary production line of flat glass. To enable the glass to cool down evenly and slowly to ensure the optimal struc- ture, the line after the tin bath must be additio- nally heated, up to 680 °C. This resembles the temperature that is needed in the processing fa- cility for the creation of tempered security glass.

Since I can do only an estimation on how much security glass is produced in a day, I stayed quite conservative with the numbers.
In the table for the float glass line, there is a heat loss about 1200 MJ per ton of glass. One standar- dized sheet of glass (321cm x 600cm) weights at a thickness of 4mm equals a weight of 190 kg – I assume there are easily 5 of such glass pa- nels converted into the final tempered sheets, due the largeness of the factory. Assuming the heat loss would be slightly less in the factories, as the ovens are not quite as hot and reach between 600 -650°C. We equal that in a heat loss of 36 GJ that is resemblant about which is equal to 20 ha of heating power. The size of the of zone next to the plant equals in around 1 ha, which proves that there is more than enough heating to be used for the greenhouses, even so to host plants from warmer climates.

Considering all this, it is still leaving open a cer- tain amount of heat that remains unused. Large distribution centres of retailers like Coop and Migros are in close vicinity and could profit from the heating as well, maybe even setting up their own greenhouses to produce more locally sourced fruits and vegetables. This would elimi- nate other costs of transportation and logistics. As already mentioned, the factory of Glas Trösch is surrounded by vast fields of agricultural land. The establishment of private relationships to the local farmers and providing them a framework with the case study, the area of planting could be extended to additional fields, resulting in bene- fits for the population of Switzerland as well as the farmer who owns the land.

Alternative Scenario for the Recycling Cycle

The second focus of the project is aiming to change common practices, questioning the need for absolute perfection in glass. In the second half of the 19th century, it was common practice to divide the glass into different classes, defined by the quality of the transparency. Usually, the lowest class, called ‘Gartenblankglas’ was used for building greenhouses. Such practice could be adopted again easily, as well as optimizing cutting practices in the factories. (Here cutting graphics)

By urging the manufacturers to reuse the smal- ler scale cutoffs and minimizing the cut offs by optimization of space on the standardized sheets, less material will need to be brought back to the melting factory, downcycled or even end up on a landfill.

In the context of Switzerland, it makes sense to look at this in the scope of larger logistic cycles, as most of the material would stay in the country and be used locally.

The project is picking the aspect of the imperfec- tions of glass and smaller scale piece up in two ways.

1. On the North Façade of the building, the smaller cut-off pieces are creating a curtain like cloth, hanging from the structure of the green- house. This creates a kaleidoscopic effect on the visitor halls and breaks up the rigidness of the flat glass panes into a fabric like structure.

2. The technique of the hanging cloth is ap- plied on the smaller scale, modular interventions and can be adapted to current situations. Small scale decorative windows, or lower-class glass sheets for the use of greenhouses.

The smaller glass panels provoking a more textile like manner is a reference to traditional greenhouse and palm houses, such as Paxton’s or Loudon’s Greenhouses in Great Britain. The glass becomes here a skin, an ornament, rather as something that is not perceived at all.

Unveiling Transparencies: Making the Heat Visible in the City

The city of Zurich is already developing multiple new strategies on working with excess heat on the larger scale – Heat from the waste incinerator plant in Oerlikon, the wastewater treatment plant in Altstetten or heat out of the groundwater and the lake of Zurich is already being offered in cer- tain districts of the city as a heating alternative. The energy strategies of the city are always open to discuss alternative sources for smaller, local heating networks. One waste heat source that is growing ever more in numbers, is the warm air of server rooms. This can be considered as well on different scales: an architectural office operating their own server, which needs to be additional- ly cooled, often through ventilators, which only move the heat to another space.

Internal server stations of larger companies oc- cupying whole floors, emitting the heat to the out- side space as well. And lastly, the development of several cloud server stations in and around Zurich lead to the discussion on how to use the excess heat emitted by the super computers. The companies are often in dialogue with local au- thorities to search for solutions that also benefits the local communities. In the city itself, the data center of Swisscom at Herdernstrasse (image of Herdernstrasse) is embedded into a district hea- ting system and provides heating for homes in the district of Altstetten. The ‘Energiezentrale’ visible when traveling by train to Zurich, acts as the central node in this scheme. Today, the heat pumps convert 14 Mio. Kwh/a of waste heat from the data centers and the wastewater treat- ment plant into useable residual heat. With these number, we can assume this covers at least the heating demand of 1000 households