Optimal Control Approaches for Analysis of Energy Use Minimization of Hybrid Ground-Coupled Heat Pump Systems

Abstract

In this paper, we present a prediction-based dynamic programming (DP) control approach, a nonlinear model predictive control (NMPC) approach, and a linear optimal control (LOC) approach to analyze the minimization of the total energy use of a hybrid ground-coupled heat pump (hp) system (incorporating a ground-coupled hp, a gas boiler, a passive cooler, and an active chiller) under operational constraints. A large-scale emulator model (based on finite-volume method and the equivalent-diameter approach) is used for the borehole system and for the assessment of different control algorithms. A nonlinear autoregressive exogenous model is identified from the inputoutput data generated by the emulator model to be used in a DP-based controller. Since DP is a global optimal control method, it was used as a reference for performance assessment. Next, a state-space reduced-order control-oriented model with a larger sampling time is obtained from the emulator model using the so-called proper orthogonal decomposition model reduction technique. This model is used in an NMPC algorithm to see how much NMPC is suboptimal with respect to the DP in terms of annual energy use minimization. Finally, a series of LOCs based on constant hp coefficients of performance is tested to see how much the system performance deteriorates. The control algorithms are used for the satisfaction of heating-cooling demands of three types of buildings: 1) heating dominated; 2) cooling dominated; and 3) thermally balanced. The effects of constraining thermal buildup/depletion of ground, variable electricity prices, and marginal violation of thermal comfort on the performance of the different controllers applied are also separately analyzed.

Energy Management Systems and Strategies in Buildings Sector: A Scoping Review

“…Further examples for systems proposed to perform an energy-use related prediction procedure can be reviewed in [120][121][122]. Usually, these reviewed EMS-in-Bs aim to minimize energy-use [120], produce an efficient energy-use in a building [121], and/ or design an efficient energy management method [99].…”

A moment and sum-of-squares extension of dual dynamic programming with application to nonlinear energy storage problems

“…T ∞ denotes the boundary ground temperature, λ the thermal conductivity and mc the thermal inertia of the ground. If ground temperatures are not available for measurement, the model provided in Atam et al (2015) can be used instead. We set T = 12 to obtain monthly value functions, leading to ∆t = 730 hours for (29b).…”

“…For low-dimensional nonlinear systems, it is possible in a very broad range of cases to compute a near-optimal value function by discretizing the state and input spaces and performing the standard Dynamic Programming (DP) recursion (Bertsekas, 1995). This approach has been applied to seasonal borehole storage problems in De Ridder et al (2011) and Atam et al (2015), but it becomes impractical for systems with more than only a few states and inputs due to exponential memory and computation requirements. It is therefore desirable to extend the existing theory of DDP to handle nonlinear systems, in order to take advantage of DDP's relative scalability.…”

Thermofluid Modelling of Large-Scale Orchards for Optimal Design and Control of Active Frost Prevention Systems

“…Some of them can be listed as follows. (i) developing a control-oriented model and using this model to design a nonlinear model predictive control (NMPC) system for frost prevention; (ii) determining the optimal number and distribution of hot air blowers; (iii) development of optimised, rule-based controllers from NMPC-type controllers through machine learning; (iv) consideration of synergistic effects by using hot air blowers and other alternatives, such as water sprayers around the perimeter of the orchard, and mulching or coverage of the fruit trees, which could significantly reduce the required minimum frost prevention energy from the use of hot air blowers; (v) development of different active frost prevention systems, including renewable energy sources and their economic feasibility analyses: for example, photovoltaics systems [25] and ground-coupled heat pumps [26][27][28] to fully or partially heat/warm the hot air to be blown. Funding: The first author would like to thank TÜBİTAK for funding (through the TÜBİTAK 1512 program) his project entitled "Development of tools for solar-energy assisted frost prevention systems in large-scale orchards.…”