Researchers from the Southern Institute of Technology in New Zealand, Auckland University of Technology and Auckland University have developed a technique to determine the efficiency of solar-powered parking machines in urban environments.
The scientists said the on-site generation of solar power is crucial to the feasibility of a new generation of sophisticated parking machines that need much more power than traditional systems, with demand estimated at between 500 W and 1 kW. “In running the machines, significant quantities of annual revenue are absorbed, raising concerns about their viability in areas where the parking occupancy rate is small,” they informed.
Small solar panels on top of buildings are a reasonable way to save energy costs, but the group urged developers to allow partial shade at different periods of the day and year for economically viable projects to be introduced. When PV power has to play a part, the positioning of the machines needs to be designed in advance in line with available solar radiation resources and all potential shading factors surrounding it.
The researchers looked at the solar power of 15 parking machines located in Auckland’s central business district. “A 360-degree high-definition camera was used to capture the fisheye images (256 by 256 pixels) from the top of each parking machine’s solar panel,” they said.
They used a magnetic compass to make sure the point of reference for the camera was still in line with the true north.
Each of the 15 apps the sky-view factor (SVF) has been calculated. The less obstructed computers were found to have an SVF of 72% and 62%.
“The sky view was found to be obstructed by 50 per cent or more from all the other parking machines,” they said. “In other words, at any point during the year, these devices will not be able to absorb more than 50 per cent of the diffuse solar radiation.”
Even more disappointing have been the findings for direct beam solar irradiance. Only two computers earned more than 50 per cent annual obstruction time percentage.
The researchers calculated the total irradiation received by each machine over the year, after evaluating diffuse and direct radiation. “Once again, only two machines reached the 2880 MJ / m2 mark, which defines the requirement for installing solar panels, taking into account both the technological and economic limitations,” they said.
The researchers presented their results in the latest publication in Renewable Energy, “Solar Capacity Assessment of Traditional Parking Machines in an Urban Climate”
Source – here