Solar Panel Innovation Allows for Plant Growth, Energy Generation Simultaneously

By: Laura Panjwan 

Although solar energy is one of the cleanest and most abundant renewable energy sources available, the space required to install solar systems can be a barrier to its implementation.

In countries where farmland is limited, solar panel insulation just isn’t a realistic option, said Jan Ingenhoff, PhD, a research professor at the Institute of Advanced Technology, the University of Science & Technology of China (USTC).

“If you look at the solar panels that are typically installed on farmland areas, you can’t do much beneath them so farmers have basically had to give up part of their land for this solar panel insulation,” Ingenhoff, in an interview with R&D Magazine, said. “Some farmers are OK with it because they have very large land areas, but in countries like Israel or China, where you have a shortage of land, it is not good to sacrifice that land for regular solar panels.”

To solve this problem, Ingenhoff—along with his colleague Wen Liu, PhD and their team at USTC—has developed the Agriculture Solar Concentrator Photovoltaic, a new type of solar panel system that allows for simultaneous plant growth and solar energy generation on the same land.

The team currently has four working prototypes installed in China, a country in urgent need of maintaining and recovering any agricultural land due to drastic urbanization in the past.

The researchers have two more installations planned for 2019 and 2020, and are moving toward making their system commercially available.

The technology was a 2017 R&D 100 Award winner.

How it Works

The system is based on the concept that plants don’t actually need 100 percent of the light sources the sun provides, Ingenhoff explained.

“Plants need only about 10 percent of the light, some blue and some red light and that’s all. The rest you can leverage for solar energy generation,” he said. “The solar panels could be described as semi-transparent. Some light is going through them allowing the plants to grow, while the rest is used for solar energy.”

The Concentrator Photovoltaic (CPV) setup is collecting specific reflected light for solar power generation. Credit: IAT

The system uses curved solar panels that are covered with a film created by several polymer layers staged together to form a dichroitic multilayer film. This allows the selective transmission of only the wavelengths necessary for photosynthesis and plant growth. All remaining sunlight is reflected and focused to concentrating solar cells for photovoltaic power generation. A dual tracking system ensures that the reflected wavelengths are focused on the concentrating solar cells throughout the day.

The system can also be adjusted for the seasons.

During winter, the generated electricity could be additionally used to supply light to the plants via red and blue LED, while during the summer, when sunlight is vastly available, the split-ratio could be such, that the sunlight can majorly be used to generate electricity, while there is no negative effect on the plant growth.

The way the light is split between solar energy generation and the plants can also be adjusted for specific plant needs, Ingenhoff said.

“We have studied what kind of light different plants need,” he said. “For example tomatoes need a little bit more red light, while lettuce may need a little bit more blue light. You can adjust this very specifically to these plants and what they need. That is a huge benefit for the farmers because some want to focus on strawberries, some want to focus on tomatoes and they can say, OK we need this kind of film system and we [the USTC team] can make that happen.”

Currently, the system can produce approximately 90 watts per square meter of energy, but the researchers are are working to optimize their film to transmit more precisely the amount of light the plants need to increase its energy generation. They expect to soon be able to produce 120 to 130 watts per square meter.

This is slightly short of the 150 watts per square meter of energy that conventional solar panels produce, Ingenhoff said.

“We will be indeed always be a little bit short compared to the regular solar panels because some of the light is used for the plants,” he added. “But the advantage is that you can establish this system on farmland and do both solar energy generation and plant growth so I believe it’s worth it.”

Credit: IAT

Other Advantages

In addition to solar energy generation, the Agriculture Solar Concentrator Photovoltaic can also be used to improve plant growth, especially in drought-stricken regions.

“About five to ten years ago people were a little concerned about letting plants just grow by blue and red light, because your first gut feeling is that the plants need all the light,” said Ingenhoff. “But there have been many studies that plants grow very well and even indeed better with just blue and red light. One of the reason for this is that if you block these near infrared (NIR) and far infrared light (FIR) from reaching the plants, you protect them from the heat, and the water evaporation on the farm is reduced. You have a better growth potential for the plants with the growth system.”

Reducing water use is an especially important issue in countries in the southern hemispheres which face water shortages, as well as China, Ingenhoff noted.

The researchers grew lettuce, cucumber and water spinach with the film covering and without the film and found that the lettuce grew to 17.59 cm with the film and 12.83 cm without, the cucumber grew to 15.50 cm with film and 15 cm without, and the water spinach grew to 12.67 cm with film, and 11.160 cm without.

The Agriculture Photovoltaic (APV) transmitting necessary light for plant growth (blue and red light). Credit: IAT

Next Steps

The team now plans to adjust the current systems in use based on farmer feedback. They also need to assure that the systems hold up long-term without deteriorating, and can be cleaned and maintained easily.

The team is currently working to expand the use of their system outside of Asia and are working speaking with potential clients in Spain as well as the National Renewable Energy Laboratory (NREL) in Colorado to set up joint actives and new prototypes.

Decreasing the cost of the system is also a goal of the research team, said Ingenhoff.

“We need to understand how the cost could be brought down when you install the system in larger areas. At the moment the cost is OK, but when we want to promote this product on a larger scale we will need to bring the cost down. We are working on making the film more cost effective so that more people can utilize it.”


This New Solar Farm Combines Clean Energy and Beehives

Using the space around the solar panels as sites for 48 hives, the Eagle Point solar farm is using its land to save pollinators and help local agriculture.

Photo: Pine Gate Renewables

By: Adele Peters

At a solar farm surrounded by orchards near Medford, Oregon, native flowers are beginning to bloom between the solar panels, and 48 beehives sit at the edge of the field. The solar farm, called Eagle Point, is now the largest “solar apiary”–a solar energy project designed to benefit pollinators–in the country.

“For me, it comes from a place of wanting to change the culture of solar and really taking into consideration more than just the panels,” says Julianne Wooten, environmental manager for Pine Gate Renewables, the North Carolina-based solar power company that developed the site.

In 2017, the company began working on a new project to keep land productive at its solar farms, reintroducing native plants, and, in some cases, working with farmers or ranchers to plant crops or graze animals around the panels. A nonprofit called Fresh Energy helped connect the company with a local beekeeper who happened to be looking for a new home for some of his hives. (This isn’t the only smart combination of clean energy and agriculture: a solar farm in Japan is growing mushrooms under the panels.)

For pollinators, sprawling solar plants can provide space for much-needed habitat. (By the spring of 2019, when the new native plants are more established, the Eagle Point solar farm will offer 41 acres of new habitat.) For nearby farms growing crops that rely on pollinators–at a time when thousands of wild pollinators are at risk of extinction, and beekeepers are still struggling to maintain their populations of honeybees–this type of project can also play a role in supporting the food supply.

For the owner of a solar farm, seeding fields with native flowers and grasses has a higher upfront cost than at a typical installation; Pine Gate also worked with experts in restoration to ensure that they were making changes that were ecologically sound. But roughly a third of the maintenance costs of a solar farm can come from managing vegetation. Depending on the location, grass growing under panels might need to be mowed eight times a year. Shifting to natural vegetation can reduce that to one or two times a year, and should save the company money over time.

“It is more expensive on the front end, and I think that’s why it’s hard to gain quick traction within the industry,” says Wooten. “People want to see that it’s going to work out.” The company partnered with the National Renewable Energy Lab to study the project, and the federal lab will install test plots at Eagle Point and at some of the company’s other sites to study the native vegetation and crop performance, ultimately sharing results with other solar developers to improve industry standards.

“One of the goals of the project is to create a database that can be utilized by other developers to show them what native species will thrive in a given area and really further the industry,” she says. One recent study estimated that existing and planned solar plants are near more than 860,000 acres of farmland that could benefit from better access to pollinators. “If this became even remotely the norm, the amount of habitat that these solar farms could provide to these pivotal parts of our economy could be really big, especially as solar continues to grow.”



Improved Forecasting Of Sunlight Could Help Increase Solar Energy Generation

The Sun is becoming an increasingly important source of clean electricity. Accurate sunlight forecasts being developed by A*STAR researchers could greatly improve the performance of solar energy plants, making it a viable alternative to carbon-based sources of power.

A photovoltaic power plant can cover up to 50 square kilometers of the Earth’s surface and can generate up to a billion Watts of electricity. This capacity depends on the amount of sunlight at that location, so the ability to predict solar irradiance is crucial for knowing how much power the plant will contribute to the grid on any particular day.

“Forecasting is a key step in integrating renewable energy into the electricity grid,” says Dazhi Yang from A*STAR’s Singapore Institute of Manufacturing Technology (SIMTech). “It is an emerging subject that requires a wide spectrum of cross-disciplinary knowledge, such as statistics, data science, or machine learning.”

Yang, together with Hao Quan from the A*STAR Experimental Power Grid Centre and colleagues from the University of Tennessee at Chattanooga and the National University of Singapore, has developed a numerical approach to weather prediction that efficiently combines multiple datasets to improve the accuracy of solar irradiation forecasts.

Hourly changes in the atmosphere, annual changes in the distance between Earth and the Sun, or 10-yearly changes in the Sun’s internal cycles can all alter the amount of sunlight that reaches the Earth’s surface. These changes occur on very different time scales, and so conventional forecasting methods model variability at different timescales separately, which makes computer processing easier. However, these methods rely on a simple addition of forecasts, with no weighting that makes more use of better forecast sub-series. Moreover, the forecasts they generate are only accurate on the timescale of the original series.

Yang and the team developed a framework that reconciles the different timescales by forming a temporal hierarchy that aggregates forecasts obtained at different timescales, such as high-frequency, hourly data and low-frequency, daily data. “Temporal reconciliation is a type of ensemble forecasting model that forecasts the next day’s solar generation many times, separately, using data of different temporal granularities, hourly, two-hourly, and daily,” explains Yang. “These different forecasts are then combined optimally through statistical models to produce a final forecast.”

The researchers tested their numerical weather prediction method using data from 318 photovoltaic power plant sites in California over a year. Their temporal reconciliation method was shown to significantly outperform other numerical day-ahead forecasts.


Move Over Elon: Global Energy Prize Goes To Australia’s Solar Guru

UNSW professor Martin Green, who revolutionised photovoltaics, says sun’s power is ‘the best option out there’

By: Sophie Vorrath

‘We’re looking at hitting a terawatt of solar production in 2024,” says Australia’s prize-winning photovoltaics expert Prof Martin Green. Photograph: Pablo Blazquez Dominguez/Getty Images

The “father of PV” – University of New South Wales professor Martin Green – has become the first Australian to win the global energy prize from a shortlist that included Tesla’s Elon Musk.

UNSW said Green had been selected from 44 contenders from 14 countries by a committee of leading scientists to share the $820,000 prize with Russian scientist Sergey Alekseenko, an expert in thermal power engineering.

It said Green was honoured for revolutionising the efficiency and cost of solar photovoltaics, and making it the lowest-cost option for bulk electricity supply.

Green, the director of the Australian Centre for Advanced Photovoltaics, is a leading specialist in both monocrystalline and polycrystalline silicon solar cells.

In 1989, his team supplied the solar cells for the first photovoltaic system with an energy conversion efficiency of 20%. In 2014 he headed the development team that first demonstrated the conversion of sunlight into electricity with an efficiency of 40%.

Green also invented the PERC solar cell, which accounted for more than 24% of the world’s silicon cell manufacturing capacity at the end of 2017.

The research group he founded at UNSW – the largest university-based PV research group in the world – is broadly credited with driving the enormous reductions in costs in solar PV, largely through the work of Green’s students in establishing manufacturing centres in Asia.

“Not everyone would agree with that attribution,” said Green in an interview with RE on Friday, adding that Tesla’s Musk would have been his pick for the prize for his crucial work of putting electric vehicles on the agenda.

Green was keen to pay tribute to his UNSW solar stablemates, Zhengrong Shi, who left Australia to form Suntech Power in the US, and Stuart Wenham – the “Einstein” of the solar world, who died, aged 60, in December 2017.

“In particular, Stuart created this computer program that was a virtual production line,” Green told RE. “That overcame the language barrier in training hordes of Chinese engineers in setting up these [solar PV] production lines.”

Some 15 to 20 years later, and the global growth of solar PV – now the cheapest new form of energy generation – has soared beyond virtually all predictions.

“If you look at the figures from the last few years, growth has consistently stayed at around 40% a year,” Green said. “If it keeps growing at that rate, we’re looking at hitting a terawatt of solar production in 2024.

“Even if it slows to growth of 20% a year, we are on track to reach production levels of a TW a year in the late 2020s. And that’s the area where you can really start cutting greenhouse gases.”

And that’s what it’s all about – a cheap transition that does not cost more and in fact will likely deliver savings – although some people, and some governments, prefer to remain none the wiser. Which is why awards like this one are so important.

“I think [this is] a good opportunity to get across the message that things have changed with solar and that it’s the best option out there,” Green said. “That’s an important message to get out.

“There’s a growing consensus that we’re going to get most of our energy out of solar down the track. It’s not a matter having to help solar along. It’s not about removing the last remaining barriers – and getting out of the way of [renewable energy].”

Green said removing barriers often meant changing regulations to make them consistent with a solar type of future, as well as overcoming political resistance in places like Australia and the US.


The Case For Pursuing Clean Energy Through Systems Thinking

By: Richard Piacentini

Denmarsh Photography/Phipps Conservatory 

The Center for Sustainable Landscapes (CSL) generates all of its own energy and treats all storm and sanitary water captured on-site. An integral part of the Phipps visitor experience, it is the only building to meet four of the highest green certifications: the Living Building Challenge; LEED Platinum; WELL Building Platinum; and Four-Stars Sustainable SITES.

Everything is connected. That is to say, nothing happens in a vacuum. More than 2,000 years ago, Aristotle postulated that nature abhors a vacuum. Nature, like all things, work in systems, where everything is connected.

At Phipps Conservatory and Botanical Gardens, we have celebrated the beauty and importance of the natural world for 125 years and look to it now as inspiration for using systems thinking as a way to help solve the critical challenges that affect us all and provide us with solutions, such as adopting clean energy.

When facing a challenge, we have a tendency to address the symptoms,such as climate change and cancer, rather than the root causes which are often related to our disconnect from nature, our lifestyles and our unsustainable use of natural resources. Addressing symptoms is fragmental and only works in the short-term, as it never corrects the underlying cause. When we strive to understand the interconnectivity of whole living systems, we can appreciate our part within the larger natural and social systems in which we are nested. Only then we can catalyze real and meaningful long-term change.

In her work, regenerative business advocate Carol Sanford describes four paradigms for interacting with the world.

In the extractive model, it is all about “me”; the individual doesn’t care who or what they hurt to get what they want. The world is seen in fragments … there for the taking. This is colonialism.

In the less-bad model, we see a shift in thinking from “me” to “us”; an individual in this paradigm sees the world as fragmented but recognizes the fragments as interconnected and tries to stabilize them. This is where the environmental movement began, as exemplified by the “reduce, reuse, recycle” hierarchy and the first green building certification systems.

The do-good model is also about “us” but recognizes reciprocity; an individual in this model sees the world as fragmented but interconnected and tries to improve it. Some later iterations of green building programs fit this model.

The final paradigm is regenerative. It is about “us,” and seeing the world as a whole interconnected system rather than separate fragments. In a regenerative world, individuals move beyond thinking about themselves in isolation to see the larger social and natural systems that we collectively need to survive. This is the paradigm we need to adopt for the long-term health of ourselves and the planet.

Phipps Conservatory and Botanical Gardens embraced a 100 percent renewable energy philosophy in 2005.

When Phipps Conservatory and Botanical Gardens opened in 1893, most people thought there was no limit to the amount of natural resources we could use or the amount of pollution we could produce. In fact, people thought that humans would conquer nature. Our original conservatory is a great example of that type of mindset; a single-paned glass building designed to grow tropical plants in a temperate climate — from an energy perspective, this is one of the least efficient buildings imaginable.

In the 1990s, Phipps endeavored on a multi-phase master plan to renovate and expand the campus. Through each project, starting with building a Welcome Center, we identified the systemic implications of our actions and evolved our approach. We learned about LEED and discovered how much buildings contribute to the amount of energy and water we use and the pollution we produce.

For over a century, we had been talking about the importance of the environment, so why shouldn’t our buildings reflect that ethos?

This thinking informed the next projects in Phipps’ transformation: the Tropical Forest Conservatory, a giant glasshouse that has no greenhouse effect and is 100 percent passively cooled, and LEED Platinum production greenhouses. Next, we built the Center for Sustainable Landscapes (CSL) a net-positive energy and net-zero water building. The defining standard for the CSL is the Living Building Challenge, which is systems-based and embraces the idea of regenerative thinking. The CSL is remarkable, and five years later, it is still the only building in the world to meet the requirements of the Living Building Challenge, LEED Platinum, WELL Platinum and 4 Stars Sustainable SITES.

Too often, we focus on first costs and fail to align our actions with our values. Take the CSL for example: It cost about 20 percent more than a cheap big-box type of building and not much more than a typical office building; however, it is a much healthier place to work and, in the long run, it will last longer. It uses only a quarter of the energy of a building of comparable size and it generates all the energy it needs onsite without any combustion. It also frees us from the uncertainty of the market, easily outperforming a conventional building in the long run.

We recognize that we operate within living, dynamic, nested systems and that we make reciprocal, mutually beneficial interactions with the larger and lesser systems in which we are nested every day.

This systems-based way of thinking is used to review and design all of our projects, programming and operations. From adopting 100 percent renewable energy campus-wide in 2005 to defining new, socially responsible investment guidelines last year, Phipps is committed to understanding our role in nature and in developing the capacity in everyone we reach to make sustainability a defining component of their lives.

We will not conquer nature. Even if we could, it would be self-defeating, considering human and ecological health are one and the same. We must rethink the status quo and change.

It is not a technology problem and it is not a cost problem; we have the ability and means to solve many of our human and ecological health problems today. We have the capacity, but it is a question of whether we have the will to move beyond short-term symptomatic thinking and do what we know is right. From 2005 to 2016, Phipps reduced carbon dioxide emissions from our buildings by 56 percent per square foot, twice as much and twice as fast as the Paris Climate agreement.

When we have the focus and will to lead the way through regenerative systems thinking, our actions will provide a healthier planet for ourselves and all of the other species that share it.