Pairing solar power to sustainable energy storage solutions within a residential building: A case study

This research paper presents the case study results on generating electricity based on solar resources for an existing residential building with conventional electric energy demand located in Cluj-Napoca, Romania. The solar energy system proposed for analysis has provided the back-up energy through two types of state-of-the-art energy storage technologies: (a) Tesla batteries and (b) hydrogen vector energy, obtained electrolytically on-site. Starting from the main imposed condition that all the building's electric energy demand be provided by the solar resource, sustainable technical solutions for renewable energy storage are of crucial importance for the successful implementation of power systems based on clean solar energy. New solar energy storage technologies are imperative for the superior harnessing of solar resources at the production site, whether it is short-term energy storage such as Tesla batteries or long-term energy storage such as hydrogen energy vector. The main objective of this work is to assess the feasibility of the proposed grid-independent energy system, which is pairing solar power to sustainable energy storage technologies within an existing residential building with conventional electric energy demand. This study aims to evaluate the optimal sizing of the solar units implemented in the design along with the optimal back-up energy storage capacities to fulfil the building's daily electricity demand in an uninterrupted mode. This article investigates the possibility of supplying 100% solar power to the existing residential building with conventional electric energy demand under constraints and limitations conditions due to the stochastic nature of building electricity consumption, volatile and intermittent nature of solar resources, local meteorological conditions specific to the building's placement and space limitations for the positioning of the photovoltaic panels. The average daily load that has been calculated for the building has a value of 6.50 kWh. To reach the proposed target of integral solar power supply, photovoltaic panels with an installed power of 7.84 kWp paired with a Tesla batteries bank with a storage capacity of 7.4 kWh are needed, and in the case of storing solar energy in the form of electrolytic hydrogen it is necessary to pair the photovoltaic panels with an installed power of 15.12 kWp, 3 kW electrolyser, 2 kW fuel cell and H-2 tank of 7 kg. The annual energy demand of 2369 kWh is achieved of 43.27% directly from photovoltaic panels and 56.73% through the back-up energy in case of pairing the batteries as an energy storage medium, and in case of pairing hydrogen as an energy vector, 41.53% is powered directly by photovoltaic panels and 58.46% comes from the energy reserve stored through hydrogen technologies. The environmental analysis highlights an average decrease of up to 85% in carbon dioxide emissions generated by the implementation of clean energy systems analysed compared to the grid electricity. Also, the results of this study show that the investment costs in photovoltaic panels and storage systems are still high, limiting their use in residential buildings, but we are witnessing technological developments to improve the performance and durability of these electricity storage solutions at low costs, which will allow them to be marketed on a large scale, particularly widespread for residential applications.