Optimised Sizing and Control of Non-Invasive Retrofit Options for More Sustainable Heat and Power Supply to Multi-Storey Apartment Buildings

Considering the ambitious climate goals defined by the European Union, the significant share of energy demand represented by buildings, the slow process of their renovation due to challenges such as a need for majority consent from residents and limited available space in dense urban areas, this study aims to foster retrofitting of energy supply systems of multi-storey apartment buildings, improving their sustainability. This entails making the transition to sustainable energy systems more socially acceptable and practical in urban contexts by proposition and demonstration of the potential of a power and heat supply system retrofit that minimises disruptions felt by residents. It integrates rooftop renewable power sources, heat storage with an electric heater, heat pumps, and existing connections to public utility networks. Furthermore, simulation results of both single- and multi-objective optimisation (performed by the genetic algorithm) for equipment selection, as well as conventional and smart control (implemented as a gradient-based optimisation) for daily scheduling, are compared, defining the main scientific contribution of the study. It is found possible to achieve a net present value of up to almost twice the annual energy expenses of the unrenovated building or self-sufficiency rate of up to 41.6% while using conventional control. These benefits can reach 2.6 times or 49.8% if the smart control is applied, demonstrating both the profitability and improved self-sufficiency achievable with the proposed approach in Latvian conditions.