Studying the Thermal Performance of Beehome Hives
The Beehome is a radical, technology-driven take on classic beekeeping. It can care for beehives, from monitoring through feeding, strengthening, and even treating disease. In addition to the actions taken by the robotic unit to tend the hives, the Beehome is also a new form of habitat for the bees. When designing and implementing the Beehome, we do our best to ensure that our latest solution improves bee conditions in all aspects. A crucial aspect we discuss in the following text is the thermal properties of the hive.
Bees are capable of significant thermo-regulation. They can regulate both temperature and humidity levels in the hive. In the summer, they cool the hive by venting air in specific routes and evaporating water to cool it. In the winter, they seal cracks and actively heat the hive by vibrating their flight muscles to create heat. It’s this remarkable ability of the bees that makes it difficult to test the thermal properties of a newly planned hive. Bees inside the hive will alter the temperature to fit their own needs.
So, atrue assessment of the Beehome hive’s thermal performance should be done in the lab without bees as they will compensate for worse performance by increasing the regulation efforts. There are three main strategies to assess the thermal performance:
Physical calculation — this is the simplest method. Using the thermal properties of the hive materials and geometry, we can calculate how much energy is needed to keep the hive at a given temperature. We can repeat this estimation for various temperature gaps to estimate the hive performance. For example, we can assume that the hive is a box with walls of specific thickness, heat conduction, and inner and outer temperatures. We can derive the energy flow from the hive to the ambient for these specific conditions. This calculation will not truly represent a real-life result because:
- The temperature is not homogeneous within the hive. It can be up to 35˚ near the central brood area but be as low as 10˚ near the edges. Therefore, the heat loss along the hive walls is not constant and should be calculated more accurately.
- Temperature differences between various regions of the hive will cause convective heat flow in the hive, which will increase heat loss in general.
- Cracks and openings in the hive will strongly affect the thermal performance. Moreover, wind will influence these effects in a non-linear manner.
Computer simulation — to address the limitations of physical calculations, we can use a computer model of the new hive to estimate the temperature distribution and airflow, thus improving our thermal predictions’ accuracy. A good simulation will allow us to check for weak thermal spots and study the effect of changes in the geometry and materials of the hive. However, even a well-designed simulation can be prohibitively inaccurate. Since we are dealing with living creatures and must be sure that our hive design is good, we need an even better approach.
Experiment — directly measure the system’s thermal performance in the conditions we are interested in. This gives the most accurate results, with the slightest possibility of significant error, but it is much harder to perform in terms of time and labor. Moreover, the experiment will have to be repeated for each variation we want to study, whether it is another material or a different geometry.
Combination — Combining simulation and validation experiments would probably be the best approach. The simulation allows a broad inspection of the effect of materials and geometry, while specific validation experiments test the consistency between the simulations and real-life results.
Building an Experimental System to Test the Thermal Performance of Our Hives
Our approach is to place several hives of each type in the field (for example, Beehome hives and classic wooden hives) and actively heat them to a constant temperature (35˚ in the center of the hive, mimicking a real beehive) for 24 hours and measure the amount of energy (KWh) required to keep each hive at the designated temperature. A higher energy expenditure will mean lower thermal performance.
To do this test, we designed the following test rig:
Heat controller — we use an STC-1000 type controller. After having some issues with the cheapest brandless type, we started to buy the branded versions, for example, those sold by Inkbird or Elitech.
Power meter — We use a simple, off-the-shelf meter. This is not a data logger but a counter. We reset it at the beginning of the experiment, and it counts the number of KWhs used during the experiment.
Heat source — We use DC current-operated silicone heating pads. We use 220v AC to 12v DCtransformers and control the transformer with the temperature controller. The transformer is connected to the grid via the power meter. Any energy used by the transformer is counted in the power meter.
We have built six units of the above measurement rigs. These allow us to run an experiment for two hive types (for example, a Beehome hive and a classic hive) with three repetitions for each hive. The repetitions are necessary as sometimes the measurements are noisy, and repetitions can also tell us if one of the hives is anomalous, and we need to repeat the experiment.
Summary andTips
It took us some time to refine the system, but now it works well, and we have developed a quick flow of experimental iterations. It allows us to compare our Beehome hives to classic hives in cold weather, hot weather with strong sun radiation, etc. We can learn how ventilation shafts affect thermal behavior and how various insulation materials affect thermal performance, and ultimately, it allows us to make sure that the living conditions of bees in the Beehome hives are improved compared to classic hives.
