Cubes or towers of solar cells that extend into the sky could be the most optimal form factor for future solar photovoltaic energy farms, claim MIT researchers.
While researchers around the world have focused on improving the performance of solar photovoltaic cells and bringing down their cost, little attention has been paid to the best way of deploying these cells. Typically, solar panels are placed flat on a rooftop or on the ground, or attached to motorised structures that rotate to keep the cells oriented toward the sun.
Using computer modelling and outdoor testing of real modules, MIT researchers found that they could boost power output from two to 20 times compared to fixed flat panels with the same base area, by arranging them in three-dimensional cubes or towers.
Handily, the biggest boost in power were in situations which needed the most improvement, such as locations far from the equator, during winter, and on cloudy days.
The researchers firstly used a computer algorithm to explore a variety of different configurations, and developed analytic software to test any given configuration under a whole range of latitudes, seasons and weather.
They then confirmed their model’s predictions by building and testing three different arrangements of solar cells on the roof of an MIT laboratory building for several weeks.
The researchers found that it was more expensive to build these modules, thus making the cost of the energy greater than ordinary flat panels. However, this extra expense is partially balanced but the much higher energy output for a given footprint, as well as much more uniform power output over the course of a day, across different seasons, and when clouds or shadows block some of the light.
These improvements make power output more predictable and uniform, which could make these photovoltaic systems easier to integrate with the power grid.
The main reason for the improvement in power output is the ability to collect much more sunlight thanks to the vertical surfaces of the structures, especially during times when the sun is closer to the horizon, such as mornings, evenings and winters.
As the cost of solar cells continue to decline, cost reductions have to be made to support structures, wiring and installation — currently, up to 65 percent of the cost of photovoltaic (PV) energy is associated with installation, permission for use of land and other components besides the cells themselves. This makes more efficient structures such as this 3D system, with their lower footprint, much more attractive.
The computer modelling shows that more complex shapes will deliver even high efficiencies, but these shapes. Fortunately, the algorithms can be used to optimise and simplify shapes with little loss of energy, revealing that the difference in efficiency between more complex, optimised shapes and simpler ones like a normal cube is only about 10 to 15 percent.
The team analysed both simpler cubic and more complex accordion-like shapes in their experimental tests.
For the accordion-like shapes, the researchers simulated a structure that could be shipped flat, and then unfolded on site.
So far, the team has modeled individual 3D modules. A next step is to study a collection of such towers, accounting for the shadows that one tower would cast on others at different times of day. However, generally speaking, these structures would have a big advantage in any
In general, 3D shapes could have a big advantage in any location where space is limited, such as flat-rooftop installations or in urban environments. By minimising shading effects between towers, it is also possible to use these structures in larger-scale applications, such as solar farms.