Dynamic energy management needs in low-energy buildings imposed by stochastic solar resources

This paper introduces various electrical and thermal energy generation, consumption, and storage components in solar powered low-energy buildings. Dynamic management of such energy components is essential given the stochastic solar resources. Emphasis is put on power electronic HVAC (heating, ventilation, and air-conditioning) drives, which can act as an effective electric swing bus to mitigate solar power variability. In doing so, grid power flows become substantially more constant, reducing the need for fast grid resources or dedicated energy storage such as batteries. The concept is equivalent to using building thermal energy as virtual dynamic storage in support of power grid operation. The paper defines a bandwidth over which such HVAC drives can operate. A practical band-pass filter is realized that provides 1) lower frequency bounds such that the building maintains consistent room temperature via the HVAC system as demonstrated by a thermal modeling study, and 2) upper frequency bounds that ensure commanded HVAC fan speeds do not update arbitrarily fast. The latter primarily avoids acoustic discomfort to users. The combination is illustrated by experimental results based on various update rates of a variable frequency fan drive over a sample of actual stochastic solar data. Building electrical and thermal energy systems modeling by MATLAB is addressed throughout the paper, including solar and HVAC systems as well as batteries and water tanks.