These attention-grabbing installations generally have a sturdy metal, plastic, or stone base that extends up and out into “branches” on which solar panels are mounted. Beyond this basic structure, there is great diversity in the design of solar tree units, reflecting innovative responses to particular environments, climates, and local energy needs.
One of the most recognizable collections of solar trees in the world is in Singapore, where in 2012 the National Parks Board unveiled Gardens by the Bay, a remarkable botanical project that included an installation of 18 artificial solar-powered Supertrees towering up to 150 feet high with canopies resembling upside-down umbrellas. These colorful steel trees not only generate solar energy, but help regulate temperature, collect rainwater, and serve as vertical gardens for flowers, ferns, and climbing vines.
How Does a Solar Tree Work?
The solar tree’s photovoltaic “leaves” absorb sunlight, converting it into electricity that is conducted down through the trunk-like central pillar of the structure to an internal battery. Many designs feature rotating panels that can move throughout the day in order to capture the greatest amount of sunlight.
While most solar trees don’t generate an amount of energy comparable to a rooftop solar system, some designs are surprisingly powerful.
Solar trees are utilitarian stand-alone energy generating units that help power homes, businesses, and public services like lighting and electronic device charging. But the power generation potential of solar trees is relatively limited, and their primary purpose is to raise public awareness about renewable energy by getting people to notice and interact with solar in new ways.
In comparison to other kinds of ground-mounted solar panel installations, solar trees don't require much land. They make solar energy generation possible in land-scarce areas that can’t support vast solar canopy arrays, as well as places that lack sufficient rooftop space for panels.
In addition, solar trees create shade to help counteract the urban heat island effect and provide shelter in inclement weather such as rainstorms and heatwaves, creating greater urban resilience in the face of climate change. They also enhance public spaces and amenities, providing charging stations, powering streetlights, and contributing clean electricity to homes or commercial facilities.
At present, solar trees aren't designed as large-scale solar projects, which limits their ability to contribute to the low-carbon energy transition. Still, their striking and varied designs are attention-grabbers. This makes solar trees effective at showcasing and thereby educating people about solar energy, or promoting a business or organization’s commitment to renewable energy.
Present solar tree designs often serve as a supplemental rather than as a primary energy source—their energy generation is limited compared to other forms of solar, and they are significantly more costly per unit of energy produced. Future design innovations may bring prices down and increase energy generation so that solar tree products make up a greater share of total solar capacity and have increased value beyond green marketing or educational demonstration projects.
Solar trees of the future have the potential to provide power in remote rural communities or other off-grid locations, powering lights, cookstoves, and some appliances in lieu of dirty energy sources like polluting gas-powered generators and charcoal-fueled fires. Likewise, some forward-looking cities are already combining solar trees with other forms of solar energy to meet their facility energy needs. In 2016, Las Vegas, Nevada became the largest city government in the United States to run entirely on renewable energy, which included solar trees installed around City Hall.
One interesting technology that could lead to further innovation in solar trees involves the development of lightweight plastic alternatives to silicon PV panels.
These so-called organic photovoltaic technologies (organic because they contain carbon molecules) were on display at the Expo Milan in 2015, where the German firm Schmidhuber presented solar trees shaped like sprouting plants with flexible, hexagonal plastic solar panels forming “membrane”-covered shelters that also generated light. In the future, these plastic solar panels could be used in lightweight solar trees designed for places where much heavier silicon panels wouldn’t be safe or feasible.