In this discussion, I’ll delve into the intricate and slightly imprecise concept of synchronizing air conditioning systems with surplus solar energy.
Particularly during prolonged periods of solar generation and potentially lower energy costs, utilizing HVAC systems (specifically air conditioning during summer) to consume excess solar power can be an efficient method to utilize inexpensive energy. This approach not only maintains a comfortable indoor environment, especially beneficial for those working from home and pet owners, but also circumvents the need for intense air conditioning usage during peak pricing hours in the afternoon/ evening.
A notable project employs the DRED interface found in many air conditioning systems to regulate power consumption through a setup of four relays. More details can be found here:
Controlling Air conditioner using Demand Enabled Response Device per AS/NZS 4755
My strategy involved adjusting the air conditioning setpoint in relation to the surplus solar energy available. If the power draw is excessive, I increase the setpoint, leading the air conditioner to consume less power. Conversely, if there is an abundance of excess solar energy, I lower the setpoint, increasing power consumption by the air conditioner.
The setpoint automation is calculated using the formula:
SetPoint = ExternalTemp - (CoolingFactor / ExcessSolarPower)
Initially, I experimented with including InternalTemp as a variable, but it appeared to have a negligible effect on long-term power usage.
The CoolingFactor, expressed in watts per degree Celsius (W/°C), varies for each household based on factors such as air conditioning capacity, insulation quality, and thermal mass. In my case, a CoolingFactor of 1500 W/°C has proven effective. I’ve configured the CoolingFactor as an ‘input_number’ helper in my system.
A template is used to calculate the helper to the actual excess solar power available for HVAC usage.
Furthermore, I’ve implemented an automation that adjusts the air conditioner’s setpoint in response to changes in excess solar power. This automation also considers the state of charge of the battery, ensuring the battery is prioritized for charging. Once the battery is fully charged in the afternoon, the air conditioner then receives the majority of the power, effectively reducing indoor temperatures.
I’m eager to learn about others’ experiences and methods in managing air conditioning with Home Assistant in similar scenarios.