# Multi-Objective Optimization of Hybrid Renewable Tri-Generation System Performance for Buildings
###### Abstract  
Hybrid renewable energy systems are subject to extensive research around the world and different designs have found their way to the market and have been commercialized. These systems usually employ multiple components, both renewable and conventional, combined in a way to increase the system's overall efficiency and resilience and to lower GHG emissions. In this paper, a hybrid renewable energy system was designed for residential use and its annual energy performance was investigated and optimized. The multi-module hybrid system consists of a Ground-Air Heat exchanger (GAHX), Photovoltaic Thermal (PVT) panels and Air to Water Heat Pump (AWHP). The developed system's annual performance was simulated in the TRANienst SYStem (TRNSYS) environment and optimized using the General Algebraic Modelling System (GAMS) platform. Multi-objective non-linear optimization algorithms were developed and applied to define optimal system design and performance parameters while reducing cost and GHG emissions. The results revealed that the designed system was able to satisfy building thermal heating/cooling loads throughout the year. The ground source heat exchanger contributed 21.3% and 26.3% of the energy during heating and cooling seasons, respectively. The initial design was optimized in terms of key performance parameters and module sizes. The annual simulation analysis showed that the system was able to self-generate and meet nearly 29.4% of the total HVAC electricity needs, with the rest being supplied by the grid. The annual system module performance efficiencies were 13.4% for the PVT electric and 5.5% for the PVT thermal, with an AWHP COP of 4.0.  
hybrid energy system; heat pump; ground heat exchanger; photovoltaic thermal; TRNSYS; simulations +
Footnote †: journal: _Sciences_  
Recently, a handful of renewable technologies, such as wind turbines, solar photovoltaics, solar thermal, etc., are being developed and commercialized. One technology, photovoltaic thermal (PVT), is gaining rapid market share due to its dual function (power and heat generation), which results in a higher solar conversion rate and efficiency. However, the availability of PVT collectors and systems is still limited due to the high cost and product reliability [27; 28], but a higher penetration rate is envisioned shortly, and significant improvements are still required in terms of energy conversion and effectiveness, thermal absorber design, materials and coating selections, cost minimization, overall system optimization, and control [27; 28]. [PERSON] et al. [29] studied Heat Exchange Rate Analysis of a Low-depth Modular Ground Heat Exchanger through a Real-scale Experiment, while [PERSON] et al. [30] conducted a sensitivity study of the air baffle of a PVT model. While micro-cogeneration is recognized as one of the most promising decentralized technologies, there is renewed interest in conventional options, such as ground source heat pumps (GSHPs), as an efficient and environmentally friendly way for heating and cooling buildings [31; 32; 33; 34]. The number of installed GSHPs is on a rise [34] due to technological advances and integration with other conventional and renewable energy technologies. Most GSHPs feature ground-coupled heat pump systems with vertical boreholes that are considered the most valuable option [33; 34]. GSHP system performance is the subject of continuous research in terms of physical parameters (e.g., heat reservoir temperature and geological characteristics of the site), operational characteristics (e.g., the time distribution of the cooling/heating demand), as well as construction and qualitative characteristics of the system [33; 34]. The International Energy Agency's Energy, Buildings and Communities (IEA/EBC) has undertaken an in-depth analysis of microgeneration and other associated energy technologies in buildings [35].