Determining the Future Business Case for Small-Scale Hydrogen Storage of Renewable Energy for Autonomous Residential Applications

Abstract

With the increasing implementation of decentralized renewable energy systems in the built environment, maintaining the energy balance is becoming a major challenge. The application of localized storage systems may add to an improved balance. The use of residential batteries for short-term storage is well known. However, for long-term storage and seasonal storage, hydrogen is considered more suitable. In this project, a model was created for an energy-autonomous home with energy storage in hydrogen. The residential energy system consists of photovoltaic panels, wind turbines, an electrolyzer, compressor, hydrogen storage tank, a fuel cell system, and batteries. The electrical and heat demand were based on generalized national data for a semi-detached five-person home, though heat demand was converted to a simulated demand for electrical heating by a heat pump. To determine the technical and commercial data for the components of the system, internationally available data and targets were used. The program Homer Pro was used to determine the business case as well as to scale the components according to the demand and local climate. Six different cases were investigated: with and without heating, and with and without a battery of fuel-cell electric car. Energy demand in 2030 was either constant or, due to higher efficiency, 90% of today’s demand. In order to determine feasibility, future energy grid prices were determined for four different scenarios: constant, increasing, decreasing (2%/yr), and with the implementation of a carbon tax. It was determined that the small-scale system cannot compete with energy from the grid in the current situation. By 2030, the average annual cost of the system will remain higher than energy from the grid for each of the scenarios, despite a sharp decrease in cost compared to the current situation. Even for the most favorable net energy comparison scenario, where the energy cost rises by two percent per year and a CO₂ tax is applied to the grid electricity cost, the system remains 1.43–2.06 times more expensive. While the lowest total cost is found for the case without heating and without a car, feasibility is highest for the case without heating and with the hydrogen vehicle. Without subsidies or other cost measures, the small-scale hydrogen system does not appear to be financially competitive with commercial energy costs by 2030. The cost analysis for components shows that the relatively high cost of the system is largely due to the small scale of the system, and therefore a larger scale may be more appropriate.