Rooftop solar panels have been vying for space with the green roof trend, and for a while there it looked like no roof was big enough for the two of them. Well, that was then. The emerging field of agrivoltaics is getting set to jump from fields to rooftops, and the result could be a proliferation of solar powered rooftop microfarms across the country.
Green Roofs & Rooftop Solar
The idea behind a green roof is simple enough. Instead of finishing off a flat rooftop with a synthetic membrane, you can grow a layer of plants. The vegetation cools down buildings in hot weather, and it can also have a ripple effect on the urban environment by trapping CO2 and preventing storm runoff. Advocates also point out that the living layer helps stretch out the lifespan of the underlying membrane.
Green roofs are typically planted with sedum and other low-maintenance, non-native species. More recently, green roofs have also promoted native species and biodiversity. In Minnesota, for example, researchers have found that several species native to the state’s bedrock bluff prairies are a good match for green roofs.
“Plants growing in bedrock bluff prairies are adapted to growing conditions very similar to those found on many green roofs, including thin growing medium and high exposure to wind, sun and drought,” they note.
The researchers caution that native species in their natural environment can send roots deep into the ground in a quest for water. However, the team also takes note of anecdotal evidence that plants adapt to the rooftop environment, and grow their roots horizontally.
Rooftop Solar Loves Green Roofs
The idea of combining solar panels with green roofs has begun to attract interest, and a solar-plus-green roof study in Australia from back in 2021 affirmed something that ground-mounted solar researchers have already noted: vegetation beneath a solar panel creates a cooling effect that raises solar conversion efficiency, as solar panels function more efficiently in cooler temperatures.
The study was primarily aimed at assessing the urban ecosystem services provided by green roofs. The researchers studied two identical roofs with rooftop solar arrays, one with a green roof and one without. The study produced comparative data on the ability of green roofs to cool off buildings, as well as urban biodiversity enhancements and stormwater retention among other findings.
Things got particularly interesting with the addition of solar panels to the mix. On the plant side, the study found that certain plants grew far better in the shade of the solar panels than they do in other environments. That is consistent with findings in the agrivoltaic field, which demonstrate that some crops perform better in the cooling, protective microclimate created by solar panels.
On the solar side, the researchers calculated that solar panels in the rooftop solar-plus-green roof combination outperformed the solar-only panels by a significant margin of 13.1% overall.
The World Green Infrastructure Network took a look at the study and teased out the symbiotic relationship between energy-saving green roofs and the clean energy from rooftop solar arrays.
“Surface temperatures were greatly reduced on the green roof – in some cases by up to 20°C during summer, suggesting a potential reduction in urban heat island effects,” they noted. “Insulation was another benefit of the integrated system, preventing heat transferring inside the building as well as retaining heat in cooler periods.”
“Overall, the integrated green roof solar PV system outperformed the conventional solar PV system, confirming that green infrastructure is among the easiest and most efficient solutions that, through its multiple benefits, can help make our cities more resilient to climate change,” they concluded.
Large-Scale Rooftop Farming Discovers Solar Power
Meanwhile, the business of growing food on rooftops on a large scale has also begun to take hold. The New Jersey blueberry firm Full Blues, for example, has applied its proprietary growing process to a sprawling rooftop in New York City.
Another example is the award-winning firm Brooklyn Grange, which has established a massive rooftop farm on the roof of the Jacob Javits convention center in Manhattan including an orchard and food forest as well as vegetable crops.
The idea of adding solar to the rooftop farm mix began to take shape back in 2015, when the hydroponics firm Gotham Greens constructed a two-acre system of rooftop greenhouses on a soap factory in Chicago. The company has continued to expand its rooftop farming model since then.
All of this activity has laid the groundwork for introducing agrivoltaic technology to rooftop farming.
For those of you new to the topic, agrivoltaics refers to solar arrays that are designed to accommodate large-scale farming. Initial projects typically involved pollinator habitats and grazing lands. Now the field has branched out into food crops for humans as well as ecosystem restoration.
The Colorado solar firm Sandbox Solar has been carving out a name for itself as an agrivoltaics innovator, thanks in part to research funding from the US Department of Agriculture.
One especially interesting project involves a row of greenhouses at the Colorado farm Spring Hill Greens. Sandbox spotted an opportunity to place bifacial solar panels on strips of land between the greenhouses, which was otherwise unusable. The bifacial panels are mounted vertically to catch the ultraviolet light reflected from the greenhouses.
Rooftop Solar & Urban Agriculture
From hothouses and bifacial solar panels, it’s just a short hop over to the rooftop agrivoltiacs trend. The idea has crossed Sandbox’s radar. They have been looking at the rooftop agrivoltaics work of Colorado State University Assistant Professor Jennifer Bousselot, who became interested in field almost by accident. She was irked when another professor installed solar panels right next to her crop research plots, until she found that her plants were thriving in the partial shade.
Bousselot describes rooftop solar-plus-farming as a “mutually beneficial system.”
“Plants evaporatively cool solar panels while solar panels partially shade plants from UV radiation and extreme temperature in the often water limited growing media on green roofs. The protection that solar panels provide. slows a plants’ water use rate, which in turn reduces the drought stress on food crops,” Bousselot has noted.
Last year, a team of researchers in China and Japan modeled the capability of rooftop agrivoltaics to resolve the food-energy-water nexus. They assessed that the city of Shenzhen, China, had enough rooftops to grow enough lettuce to supply the city for a year. The demand on water resources for irrigating such a system would be substantial, though. The researchers also assessed that the rooftop solar panels systemwide would only provide 0.2% of the city’s electricity.
The University of Arizona may have some hard data to contribute in the upcoming years. The school has been working on a rooftop solar-plus-farming project since 2017. The rooftop solar installation was completed in 2020 and they got to the planting stage in August of 2021. Sensors and other data collection instruments were also installed in 2021.
So far the focus is on growing native desert perennials and annuals including milkweed and whitethorn acacia. “The seeds were provided by Strategic Habitat Enhancements, a local, women-owned organization that ensured all seeds were sustainably harvested from around the Sonoran Desert,” the school notes.
Bousselot is also working on a rooftop solar project with urban agriculture, located at Colorado State University’s new Hydro building in Denver, so stay tuned for more on that.
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Photo: The new Hydro Building in Denver will serve as a research site for rooftop solar and urban agriculture (courtesy of Colorado State University).
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FAQs
What are the negative effects of solar farms? ›
The clearing and use of large areas of land for solar power facilities can adversely affect native vegetation and wildlife in many ways, including loss of habitat; interference with rainfall and drainage; or direct contact causing injury or death.
Why don't we use solar energy more? ›– it's because the solar panels we have can only generate electricity when it's a clear sunny day. In order for a home or business to rely entirely on solar power, the owners would need to live in a sunny area and use batteries to store excess energy for cloudy and rainy days.
Is solar power good for the Environment? ›As a renewable source of power, solar energy has an important role in reducing greenhouse gas emissions and mitigating climate change, which is critical to protecting humans, wildlife, and ecosystems. Solar energy can also improve air quality and reduce water use from energy production.
How is solar energy compared to fossil fuels? ›Solar energy is compared to fossil fuels. The greatest environmental impact is achieved by solar energy. Reliable applications are better for natural gas and coal. The effectiveness of solar panels can be between 15% to 20%, whereas coal could reach 40% efficiency and natural gas can reach 60 percent efficiency.
Why do we say no to solar farms? ›Solar power plants destroy wildlife habitat. Perimeter fencing, often 6-feet high and topped with barbed wire, will restrict movement of wildlife in the area.
Why do farmers oppose solar farms? ›Solar farms are a growing trend, but they're not everyone's cup of tea. Many people are against them because they think they take up too much space, they can be an eyesore, and they can impact property values.
Which country gets 99% of energy from renewable sources? ›Costa Rica gets 99 percent of its energy from renewable sources.
What would happen if everyone used solar energy? ›It would be a difference of 22 billion tones of carbon dioxide that would not need to pollute the air or cause global warming. This figure and calculation also include the use of fossil fuels in the actual production of the solar panels. In the long run, that figure may drop to zero.
What is the dark side of renewable energy? ›The biggest dark side of renewable energy is likely the amount of space it requires. Each solar farm can produce about 357,000 kWh per acre, but the United States' electricity uses around 4,000 billion kWh each year. So, that country would need to use 11 million acres to get all of our electricity from solar panels.
Are there any environmental drawbacks to solar energy? ›Some types of PV cell technologies use heavy metals, and these types of cells and PV panels may require special handling when they reach the end of their useful life. Some solar thermal systems use potentially hazardous fluids to transfer heat, and leaks of these materials could be harmful to the environment.
Are solar panels worse for the environment than fossil fuels? ›
Solar panels are a great source of clean energy because, unlike fossil fuels, solar energy doesn't produce harmful carbon emissions while creating electricity.
What is better than solar panels? ›Wind turbines can harness up to 50% of energy compared to 20% for solar panels. In fact, one wind turbine can generate the same amount of electricity in kWh compared to thousands of solar panels.
Is solar more polluting than fossil fuels? ›Solar panels, unlike fossil fuels, do not emit pollutants or carbon dioxide into the atmosphere. They also have a negligible environmental impact. According to the U.S. Energy Information Administration, all of the above is true.
Do solar farms ruin farmland? ›The time we live in is an agricultural age, and if you think solar farms would affect your soil, the answer is they won't, and you don't need to worry about that. Solar panels are mostly made of silicon, the most abundant earth element. It plays a crucial role in the growth of plants and vegetation.
Are solar farms a health risk? ›Contrary to common solar myths about harmful chemicals, the materials used to make solar panels are sealed and contained so they do not negatively affect the surrounding area.
Why is solar farming not a good use of agricultural land? ›Solar farming will change the future productivity of the land. Because solar panels only capture 20% of the light for only about 5 hours of the day the rest of that solar energy will pass through to the ground. As a result grasses, broadleaf weeds, and eventually woody shrubs will grow.
Do solar farms devalue property? ›A new study finds that houses within a half-mile of a utility-scale solar farm have resale prices that are, on average, 1.5 percent less than houses that are just a little farther away.
Why is the government paying farmers not to farm? ›Question: Why does the government pay farmers not to grow crops? Robert Frank: Paying farmers not to grow crops was a substitute for agricultural price support programs designed to ensure that farmers could always sell their crops for enough to support themselves.
How much land would be needed to power the US with solar? ›“If you wanted to power the entire United States with solar panels, it would take a fairly small corner of Nevada or Texas or Utah,” he explained. “You only need about 100 miles by 100 miles of solar panels to power the entire United States….
Is it worth putting solar panels on my roof? ›Yes, getting a solar panel system is worth it for the excellent financial benefits and cost savings. However, solar panels aren't suitable for everyone. Residents with low energy needs, low electricity rates, or year-round inclement weather may not save money from a solar system.
What is one negative effect of solar energy? ›
The potential environmental impacts associated with solar power—land use and habitat loss, water use, and the use of hazardous materials in manufacturing—can vary greatly depending on the technology, which includes two broad categories: photovoltaic (PV) solar cells or concentrating solar thermal plants (CSP).
Do solar panels affect homeowners insurance? ›Most rooftop solar energy systems are covered by standard homeowners policies, which doesn't change your insurance plan. However, you may need to increase the amount of coverage on your home to account for the cost of the system which can then raise your premium.
What country is 100% renewable? ›Albania, Iceland, and Paraguay obtain essentially all of their electricity from renewable sources (Albania and Paraguay 100% from hydroelectricity, Iceland 72% hydro and 28% geothermal).
What is the cleanest energy source? ›Nuclear is a zero-emission clean energy source. It generates power through fission, which is the process of splitting uranium atoms to produce energy. The heat released by fission is used to create steam that spins a turbine to generate electricity without the harmful byproducts emitted by fossil fuels.
What is the most renewable country in the world? ›The same report shows the largest producer of “clean” energy is Norway, where 99% of the energy produced comes from renewable sources.
What if everyone had rooftop solar? ›Cover that in solar panels, and you would produce about 1,400 terawatt hours of electricity each year—about two-thirds of which would come from small residential buildings. The total production is equal to nearly 40 percent of the total electricity currently sold by utilities in the US.
What is the future lies in using renewable energy? ›Renewables are set to account for almost 95% of the increase in global power capacity through 2026, with solar PV alone providing more than half. The amount of renewable capacity added over the period of 2021 to 2026 is expected to be 50% higher than from 2015 to 2020.
What would happen if we left our solar system? ›"Earth would fly into interstellar space until captured or swallowed by another star or a black hole," Ceriotti said, adding that were Earth to leave the solar system, it would probably result in the decimation of much — if not all — of the planet's life.
What is the country that uses the most solar energy? ›China- 392 GW
China's solar prowess is staggering. With a whopping 392 GW, the country is the largest producer of solar energy in the world. In the first six months of 2022, the nation has deployed more than 30.88 GW of Solar PV systems.
The industry standard for most solar panels' lifespans is 25 to 30 years. Most reputable manufacturers offer production warranties for 25 years or more. The average break even point for solar panel energy savings occurs six to 10 years after installation.
What is the future of solar energy? ›
Photovoltaics (PV) and concentrating solar power are likely to continue to grow rapidly—the National Renewable Energy Laboratory (NREL) projects solar energy could provide 45% of the electricity in the United States by 2050 if the energy system is fully decarbonized—and technology costs are projected to continue to ...
What is the most harmful non renewable energy? ›Fossil fuels—coal, oil, and natural gas—do substantially more harm than renewable energy sources by most measures, including air and water pollution, damage to public health, wildlife and habitat loss, water use, land use, and global warming emissions.
What is the number 1 renewable energy? ›Solar energy is the most abundant of all energy resources and can even be harnessed in cloudy weather. The rate at which solar energy is intercepted by the Earth is about 10,000 times greater than the rate at which humankind consumes energy.
What is the most powerful renewable energy source? ›They lessen our reliance on fossil fuels, which contribute to global warming and air pollution. However, they are influenced by the weather, and their energy is more difficult to store. At present, wind power is the most efficient method of sustainable energy production.
What is the carbon footprint of making solar panels? ›Here are the most common energy sources and the amount of CO2 that's emitted in order to produce them: Solar panels produce 50g of CO2 during manufacturing. Natural gas produces 117 lbs of CO2 per million British thermal units (MMBtu) during extraction and production. Oil (petroleum) produces 160 lbs of CO2 per MMBtu.
Why is there a need to avoid even the use of solar energy if it is avoidable? ›Answer: The one environmental downside to solar technology is that it contains many of the same hazardous materials as electronics. As solar becomes a more popular energy source, the problem of disposing the hazardous waste becomes an additional challenge.
What is a safe distance to live from a solar farm? ›Because of that, experts recommend living at least 2 kilometers (about 1.2 miles) away from a solar farm.
Why can't we switch to renewable energy? ›This is primarily because the technology has taken time to develop in order to produce large amounts of clean energy, and most of our engines and systems were developed to run off of fossil fuels.
Why solar cannot replace fossil fuels? ›However, unlike fossil fuels, wind and solar can only generate electricity when the wind is blowing or the sun is shining. This is an engineering challenge, since the power grid operates in real time: Power is generated and consumed simultaneously, with generation varying to keep the system in balance.
What are the long term effects of solar energy? ›As a renewable source of power, solar energy has an important role in reducing greenhouse gas emissions and mitigating climate change, which is critical to protecting humans, wildlife, and ecosystems. Solar energy can also improve air quality and reduce water use from energy production.
What is the main disadvantage of solar panels? ›
Solar energy systems can generate electricity in any climate. One of the disadvantages of solar energy is that it's subject to temporary weather disruption. Cloudy days reduce the amount of electricity you produce. Cold, however, doesn't affect productivity.
Is there an alternative to solar? ›Besides the seven energy sources listed above, other alternative energy sources include geothermal power, wave energy, hydroelectric energy, solar thermal energy and even space solar energy. Geothermal energy is that generated in the earth and harnessed, while wave and hydroelectric energy harness the power of water.
Why are solar panels not used more? ›Why Doesn't Everyone Have Home Solar? Once solar technology became efficient enough to reliably generate enough power for the average homeowner to consumer, the adoption of solar exploded in 2008. This rapid growth is the primary reason most homeowners in California have not gone solar.
What is the biggest fossil fuel polluter? ›Transportation (28% of 2021 greenhouse gas emissions) – The transportation sector generates the largest share of greenhouse gas emissions. Greenhouse gas emissions from transportation primarily come from burning fossil fuel for our cars, trucks, ships, trains, and planes.
Is nuclear cleaner than solar? ›This is because it is a source of low-carbon energy that contributes to the production of low-CO2 electricity. It emits 70 times less CO2 than coal, 40 times less than gas, 4 times less than solar energy, 2 times less than hydroelectricity and the same amount as wind energy.
How long does it take for solar panels to be carbon neutral? ›Solar panels must be carbon neutral before they can be carbon positive and offset their carbon footprint. This process takes between 1 to 3 years on average, depending on the quality and condition of your solar system, as well as the amount of electricity generated.
How far away from solar farm is safe to live? ›Because of that, experts recommend living at least 2 kilometers (about 1.2 miles) away from a solar farm.
Is there any danger living next to a solar farm? ›Electricity from solar panels and transmission to the power grid emits extremely weak electromagnetic fields. Exposure to low-level electromagnetic fields has been studied extensively, and there is no evidence that it is harmful to human health, according to the World Health Organization (WHO).
Do solar farms ruin farm land? ›The time we live in is an agricultural age, and if you think solar farms would affect your soil, the answer is they won't, and you don't need to worry about that. Solar panels are mostly made of silicon, the most abundant earth element. It plays a crucial role in the growth of plants and vegetation.
What is the main con of solar energy? ›| Advantages of Solar Energy | Disadvantages of Solar Energy |
|---|---|
| Decreases use of non-renewable resources | High upfront costs |
| Reduces power bill | Sunlight dependent |
| Energy independence | Space constraints |
| Long-term savings | Environmental impact of manufacturing |
What are the two main disadvantages to solar energy? ›
High initial costs for material and installation and long ROI (however, with the reduction in the cost of solar over the last 10 years, solar is becoming more cost feasible every day) Needs lots of space as efficiency is not 100% yet. No solar power at night so there is a need for a large battery bank.
Do solar panels affect home insurance? ›Most rooftop solar energy systems are covered by standard homeowners policies, which doesn't change your insurance plan. However, you may need to increase the amount of coverage on your home to account for the cost of the system which can then raise your premium.
Do solar farms damage the soil? ›Only a minute amount of aluminum is released into the soil from a solar system, and it has not been shown to have any negative impacts on the earth. Though solar systems are safe to have around crops, they're also a great way to help prevent land degradation while still making good use of overworked fields.
Do solar farms pollute? ›Solar energy technologies and power plants do not produce air pollution or greenhouse gases when operating. Using solar energy can have a positive, indirect effect on the environment when solar energy replaces or reduces the use of other energy sources that have larger effects on the environment.
How hot is it above a solar farm? ›Findings demonstrated that temperatures around a solar power plant were 5.4-7.2 °F (3-4 °C) warmer than nearby wildlands. The result demonstrates that there are potential heat costs to generating green power although the added heat dissipates quickly and can't be measured 100 feet away from the power plants.
What is a con to solar energy on the environment? ›- Excessive land use, land degradation, and habitat loss.
- Hazardous material extraction and disposal.
- Life-cycle greenhouse gas emissions.
An average home needs between 17 and 21 solar panels to fully offset utility bills with solar. The number of solar panels you need depends on a few key factors, including your geographic location and individual panel specifications.