Techno-economic design of zero-energy detached house’s energy system with water electrolysis-based hydrogen waste heat under Nordic climate conditions

This paper investigates the cost-optimal dimensioning of energy systems for a detached house in cold climates, focusing on the economic potential of integrating waste heat from water electrolysis-based hydrogen production into district heating (DH) networks. It evaluates 25-year lifecycle costs (LCCs) for various energy system configurations, including DH systems with commercial and zero-emission DH prices, a ground source heat pump (GSHP) with an electric backup heater and photovoltaic (PV) panels, and a GSHP system integrated with DH and PV panels under different DH pricing models. Results show that a zero-emission DH price reduces LCC by 7.5% compared to a commercial DH price when DH is the primary heating system. However, the use of DH as the only heat source generally exhibits much higher LCCs compared to GSHP systems paired with various backup heaters. The inclusion of maximum allowed PV capacity contributes to cost optimization in all scenarios. Under the circumstance of DH as backup heating, the power fee dominates the cost structure of DH systems, accounting for over 95% of costs, which minimizes the impact of DH energy tariffs on LCCs. Additionally, the energy coverage from backup heating, namely DH and electric heater, is less than 1% and 3% respectively, suggesting a very low need for backup heating due to the low temperature levels in heat distribution and using large storage tank. Among backup heating options, electric heating emerges as the most cost-effective, offering approximately 20% LCC savings compared to solutions relying on DH systems.