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Canadian scientists have proposed combining rooftop photovoltaic power generation with an alkaline electrolyzer and fuel cell to generate hydrogen in buildings. The new system is intended to enable seasonal energy storage and reduce the levelized cost of energy in homes.
Researchers at Metropolitan University of Toronto have proposed combining hydrogen fuel cell systems with rooftop photovoltaic generation in building applications.
They tested the configuration of such a hybrid system in the BeTOP laboratory, located on the universitys Toronto campus, to obtain information on the possible application of hydrogen as a seasonal storage strategy in buildings.
The proposed system includes photovoltaic panels, an alkaline electrolyzer, a compressor, a gaseous hydrogen storage unit, a fuel cell system, inverters and a control system that regulates the distribution of energy within the system. The building also houses aerothermal heat pumps for heating and cooling, as well as a hydronic underfloor heating system.
“The photovoltaic system generates the electrical energy, and the control unit monitors whether the energy produced can cover the building load, including the heating and cooling demand provided by the aerothermal heat pump system,” the scientists explain. “In case of surplus power generation, the electrolyser unit produces the hydrogen and, on demand, the stored hydrogen is transferred to the fuel cell unit that generates electricity to cover the power deficit of the system.”
The hydrogen generated by the electrolyser unit is stored in a gas tank at a temperature of 20ºC and is then used by the fuel cell depending on the buildings electricity demand.
The group modeled the hybrid system with the TRNSYS program, which is used to simulate the behavior of transient renewable systems, and used the response surface method (RSM), which is often used to predict the relationships between several explanatory variables and one or more response variables, to simulate the performance of the proposed system.
The analysis showed that the electrolyzer operates with lower efficiency during the winter, due to low levels of solar radiation, while in summer it reaches maximum production, with a state of charge (SOC) of the system that increases significantly between May and August.
“The results indicate that the hybrid system in June and July has its minimum dependence on the grid, with only 33.2 kWh and 41.3 kWh of electricity use from the grid, respectively, while in December, more than 88% of the required load must be supplied by the network,” the researchers explain.
The simulation also highlighted the need to store photovoltaic electricity through electrolysis in the summer period, since solar energy generation exceeds the necessary building load by 2.5 times.
“The results indicate that the electrical energy produced by the fuel cell in the summer period corresponds on average to 31% of the electrical production of the photovoltaic cells,” the research group stressed. “It is also worth mentioning that the higher amount of energy production by the fuel cell in January compared to that of the PV system is attributable to the initial level of the hydrogen storage tank at the beginning of the simulations.”
The academics also found that the ideal system configuration for the selected building would require 39.8 m2 of solar panels integrated with a 3.90 m3 hydrogen storage tank. They also found that the hybrid system can achieve a levelized cost of energy (LCOE) ranging between $0.389/kWh and $0.537/kWh.
The novel system is described in the study “ Net-zero energy management through multi-criteria optimizations of a hybrid solar-hydrogen energy system for a laboratory in Toronto, Canada ” solar-hydrogen for a laboratory in Toronto, Canada), recently published in Energy and Buildings .
“It will be useful to carry out a comparative investigation between the techno-enviroeconomic performance of this study and the alternative of using battery energy storage systems (BESS),” the scientists note, referring to the future direction of their work. “This analysis can also be extended to the case of employing both hydrogen storage and BESS with appropriate economic optimization to minimize the aforementioned costs.” |
