Whale algorithm to integrate rooftop solar with air source heat pumps

Researchers led by the Shandong University in China have applied the whale optimization algorithm (WOA), which mimics the social behavior and hunting technique of humpback whales, to combine PV power generation with air source heat pumps assisted by solar thermal collectors.

The WOA is inspired, in particular, by bubble-net feeding, which is a complex, cooperative hunting strategy consisting of a highly synchronized set of behaviors that involve communication and cooperation, demonstrating signs of high social intelligence. It comprises three operations to simulate the search for prey, encircling prey, and bubble-net foraging behavior of humpback whales.

“Two optimization variables, Spv and Sth, are involved in the optimization search process, and the whale optimization algorithm has obvious advantages in terms of solution accuracy and convergence speed compared to meta-heuristic algorithms such as particle swarm and genetic algorithms,” the researchers explained, noting that this algorithm also offers the advantages of fewer parameter settings and better optimization seeking ability.

The scientists developed an optimized version of the WOA, which they say enables maximizations of PV power generation for heat collection and reduces grid dependency. It is reportedly able to identify the optimal area ratio of the solar energy systems needed for the system configuration. “The installation area of photovoltaic modules and collectors will not only affect the power side, but also affect the thermal side,” they emphasized.

Using the PVsyst software, they tested the proposed approach assuming the combination of PV, solar thermal energy, and heat pumps in a high-rise dormitory building located at the Shandong University's campus. They found that the optimal solution would be deploying a 315 kW rooftop PV system, solar collectors with a daily heat collection of 3502.72 MJ, and an air source heat pump as an auxiliary heat source. “With the optimal ratio, the system can gain up to $82.44 per day of operation,” the academics stated.

The analysis showed that the heat provided by the heat pump and the solar collectors is able to equal the building's heat consumption, and that PV power and grid electricity can meet the building's power demand throughout the day, while also powering the heat pump.

Considering the current tariffs the Chinese authorities pay for surplus power injected into the grid, the academics conducted an economic analysis of the proposed system and found it provides clear benefits. “The initial investment is larger than the conventional system, but the later operating costs are significantly lower than the simple solar water heating system,” they said.

They introduced the new algorithm in the study “Research and analysis of energy consumption and energy saving in buildings based on photovoltaic photothermal integration,” published in scientific reports. “The results of the example show that the roof of the building has significant benefits in environmental protection and investment recovery period when the photovoltaic photothermal system with the optimal area ratio is installed on the roof of the building,” they concluded.