Kratky Trombe Wall study
Description
In this study we retrofitted an existing Trombe wall to be able to contain living Kratky based plants. The main goal was to extend the usability of the space as it was in use as a heat-capturing device for the adjacent building only during the colder half of the year, staying closed and unused all the remaining time. Also, the additional water mass contained in the plants' roots and the shading provided by the living plants probably will affect the space's thermal balance affecting the final Trombe wall's performance, which are also an interesting factor to explore. In its normal configuration, the space in question gets quite overheated, so seeing how the plants will react and develop inside a hot TW is another question worth exploring. Mainly, we have used detailed (in 10-minute normalized intervals) thermal observational data made more than a year before the experiment in and around the TW space, as well as weather data collected at the location, which were supplemented by more readings, in particular, of surface and water temperatures collected at different height levels within the TW space, collected during the Experiment year (July 2022 to June 2023). The year before (July 2021 to June 2022, named Baseline year) was used to contrast both datasets against each others. In addition, after finishing the experiment, during 4 months (July to October 2023, named Post-experiment year) also, bottles with water and no plants were placed in the TW space to outline differences between plants and inert water mass effect on the location. Some additional readings were made, such as CO2 levels, water mass amounts within the space, plants weight and death rates were tracked and recorded as well. While we cannot compare very fairly the previous Trombe wall to a green Trombe wall space as we had so somewhat alter its configuration to be able to contain plants inside (installed a powerful exhaust and surface ventilation system, added shelves and plants shading the space, introduced some appliances, glass and water increasing thermal mass about 151%, kept the door open most of the year to insure adequate plant aeration, etc.), we can observe a notable difference in the thermal conditions, mainly, an important cooling, humidifying and stabilizing effect on TW cavity air throughout the year, making it much less overheated and volatile compared to the BY. The detailed thermal observations are available at the hourly and daily charts files, with added sensor locations and experiment timeline. The monthly and yearly summary charts were made from monthly samples of those files using Origin software. Attached drawings describe in detail the geometry and construction of the study location. Diagrams and figures outline the basic concepts in use, and photos show the study locations.
Files
Steps to reproduce
The study is quite observational at this point, so not many alterations are needed to arrive at the same conclusions. The thermal data, schedules and TW contents data was statistically analyzed using Origin software, which was also used to create the figures here presented. The study is very dependent on the local conditions, so it is not clear how well it could perform in other locations with a different climate or geometry. However, probably it can be done adjusting the plant varieties grown or modifying the amounts of water mass contained within TW. In general, the plants have adjusted to the space quite well and kept the water mass clear from algal blooms, better than control bottles open to the atmosphere, which is promising. We have used prevegetated plants, around 1-2 months old basil plants, which were grown from seed in a growing pod under artificial light, but got gradually exposed to the elements to make them more resilient and able to survive under the intense solar radiation and outside heat at the location before going into the TW cavity. Bug nets were used both before and after placing plants in the TW space, so there were no bug problems at the study location. The glass jars used in the study were coated in two layers of black paint and performed well, but might be improved with bigger water volumes available. The ventilation inside the TW is also an important factor, we need to have cross-ventilated space which will allow for at least 60 renovations/hour. on sunny days we routinely had even more airflow through the TW, to keep the space less prone to collecting humidity and dust. Intense surface ventilation was also in place, moving the air around the plants constantly. The space was inspected and water was added to the plants 2-3 times a week, this schedule was enough to keep the plants alive, but might be improved upon with a more automated self-regulating watering system. The bottles were cleaned and flushed from old nutrients every 2-3 months, which might be improved upon as well. The plants' bodies were quite close to the glazing due to our space constraints, which worked out OK, but it would be better if the surface fans were placed between the glazing and the plants. Our main challenges were cold spells in January-February, where it might have been beneficial to have curtains of insulation layers covering the glazing at night and humid spells in May-June, where better ventilation or flushing of the bottles could mitigate root fungal problems. Another critical moment was around October-November, where we receive direct sunlight overheating the space excessively. Here, a less tall, shafty and more spacious TW space might have performed better, but even so, probably we could improve the results by using a shade net over the glazing keeping, the space at more moderate temperatures at daytime.