Energy management systems (EMS) enable homeowners to actively track energy flows in their household. The EMS uses respective softwares to clearly display the generation and consumption of individual energy appliances and determines energy optimization potential based on this. The prerequisite for all of this is that the energy flows are measured as accurately as possible.
More precise and frequent recordings of individual energy flows result in better energy optimization. Better energy optimization in turn enables a higher degree of self-sufficiency as well as cost savings due to less energy being drawn from the grid. In this blog, we explain why measuring energy flows is a highly complex matter and how Kiwigrid meets the associated challenges.
How energy flows are measured in the household
In the home, the generated or purchased energy typically comes from one of the following three sources: from the PV system on the roof, from the grid or from a battery. This electricity is then, for example, converted into light, heat or kinetic energy to power various appliances in the household. In theory, this results in the following simple calculation for the energy flows: the sum of the energy that is generated or purchased is equal to the sum of the energy used by the various energy consumers in the household. However, for this calculation to work and for the consumed electricity to correspond with the sum of the electricity used by all individual appliances, all energy flows must be measured and offset against each other at the same time. Our Energy Manager performs this task in Kiwigrid by collecting the relevant data from the energy devices and sending it to the KiwiOS platform.
The challenging task of an energy manager can be illustrated using the example of a ball pool with several children playing in it at the same time. Imagine the following scenario: You are standing in front of a ball pool in which several children are playing. Now you need to find out how many balls are currently in the pool (available energy), how many balls are thrown out by the children (energy consumers) and how many balls are thrown back in by the parents (energy producers). You will quickly realize that this is quite a lot to track at once. To really measure exactly, you would have to observe all the children and parents very closely at the same time.
Challenges in the measurement of energy flows
The challenges that a EMS faces when measuring energy flows go even further than the simultaneity just described. While energy consumption can be recorded very precisely and with high resolution using a power supply meter, it is more difficult to measure self-generated electricity accurately. Many PV system inverters and battery systems have their own meters with different measurement methods.
Some devices also only provide a measured value at longer intervals (e.g. every 5 minutes), making it impossible to measure different devices at exactly the same time. Smaller consumers such as lights or laptops often have no meters connected at all – their consumption can therefore only be estimated and cannot be determined precisely. In addition, some appliances generate waste heat, which releases unused energy into the environment, which also cannot be measured accurately.
Kiwigrid's solution: Resampling
The ball pool example and the specific challenges listed illustrate how complex it is to accurately measure energy flows in the household. And yet an energy management system must meet these challenges. Kiwigrid has found a solution with its new KiwiOS X platform: resampling.
A high sampling rate is used to calculate a virtual power curve for all individual energy appliances in the household. The virtually generated power curves for consumption and generation are then compared with the actual measured values and adjusted accordingly. The fact that the power curves exist virtually means that energy flows can be determined at any point in time with minor deviations. This enables the simultaneous recording of the energy flows of all appliances in the household.
The virtual power curves also allow the implementation of a variable sampling rate - this means that energy managers can access the determined generation and consumption values at very short intervals and optimize the energy flows. Depending on requirements, sampling rates of between 15 seconds and 5 minutes can be selected for transmission to the cloud and ultimately to the energy devices. This way, Kiwigrid enables near-real-time monitoring of energy flows and cost-saving data backup.
The algorithm has already been successfully tested in recent weeks and will be made available to all customers as part of the next KiwiOS X updates.
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