Dec 2020, PV Mag: Researchers in Norway have mapped all cropland areas that were abandoned between 1992 and 2015 and found that the vast majority is suitable for PV and bioenergy deployment. Around 30% is located in Asia, followed by the Americas, with a 28% share, and Africa, with a percentage of 22%. Europe and Oceania had shares of 20% and 5%, respectively. Optimal combination of bioenergy and solar photovoltaic for renewable energy production on abandoned cropland, published in Renewable Energy, the research team initially identified, through the European Space Agency (ESA) Climate Change Initiative Land Cover (CCI-LC), around 83 million hectares of abandoned cropland between 1992 and 2015. 68% is considered optimal for solar and around 25 million hectares (32%) for bioenergy, with the former having the largest share in energy generation, at around 91% (article below).
Also: A 2019 study finds that if less than 1% of agricultural land was converted to solar panels, it would be sufficient to fulfill global electric energy demand.
The most productive places on Earth for solar power are farmlands, according to an Oregon State University study. The study, published in the journal Scientific Reports, finds that if less than 1% of agricultural land was converted to solar panels, it would be sufficient to fulfill global electric energy demand. The concept of co-developing the same area of land for both solar photovoltaic power and conventional agriculture is known as agrivoltaics.
“Our results indicate that there’s a huge potential for solar and agriculture to work together to provide reliable energy,” said corresponding author Chad Higgins, an associate professor in OSU’s College of Agricultural Sciences. “There’s an old adage that agriculture can overproduce anything. That’s what we found in electricity, too. It turns out that 8,000 years ago, farmers found the best places to harvest solar energy on Earth.”
The results have implications for the current practice of constructing large solar arrays in deserts, Higgins said.
“Solar panels are finicky,” he said. “Their efficiency drops the hotter the panels get. That barren land is hotter. Their productivity is less than what it could be per acre.”
For their study, OSU researchers analyzed power production data collected by Tesla, which has installed five large grid-tied, ground-mounted solar electric arrays on agricultural lands owned by Oregon State. Specifically, the team looked at data collected every 15 minutes at the 35th Street Solar Array installed in 2013 on the west side of OSU’s Corvallis campus.
The researchers synchronized the Tesla information with data collected by microclimate research stations they installed at the array that recorded mean air temperature, relative humidity, wind speed, wind direction, soil moisture and incoming solar energy.
Based on those results, Elnaz Hassanpour Adeh, a recent Ph.D. graduate from OSU’s water resources engineering program and co-author on the study, developed a model for photovoltaic efficiency as a function of air temperature, wind speed and relative humidity.
“We found that when it’s cool outside the efficiency gets better,” Higgins said. “If it’s hot the efficiency gets worse. When it is dead calm the efficiency is worse, but some wind makes it better. As the conditions became more humid, the panels did worse. Solar panels are just like people and the weather, they are happier when it’s cool and breezy and dry.”
Using global maps made from satellite images, Adeh then applied that model worldwide, spanning 17 classes of globally accepted land cover, including classes such as croplands, mixed forests, urban and savanna. The classes were then ranked from best (croplands) to worst (snow/ice) in terms of where a solar panel would be most productive.
The model was then re-evaluated to assess the agrivoltaic potential to meet projected global electric energy demand that has been determined by the World Bank.
Higgins and Adeh previously published research that shows that solar panels increase agricultural production on dry, unirrigated farmland. Those results indicated that locating solar panels on pasture or agricultural fields could increase crop yields.
Co-authors on the recent study were Stephen Good, an assistant professor in OSU’s Department of Biological and Ecological Engineering, and Marc Calaf, an assistant professor of mechanical engineering at Utah State University.
Elnaz H. Adeh, Stephen P. Good, M. Calaf, Chad W. Higgins. Solar PV Power Potential is Greatest Over Croplands. Scientific Reports, 2019; 9 (1) DOI: 10.1038/s41598-019-47803-3
Oregon State University. “Installing solar panels on agricultural lands maximizes their efficiency.” ScienceDaily. ScienceDaily, 8 August 2019. <www.sciencedaily.com/releases/2019/08/190808123842.htm>.
Dec 09, 2020, EMILIANO BELLINI, PV Mag
Scientists from the Norwegian University of Science and Technology (NTNU) have assessed the potential for PV and bioenergy deployment on recently abandoned cropland, at a global level.
In the study Optimal combination of bioenergy and solar photovoltaic for renewable energy production on abandoned cropland, published in Renewable Energy, the research team initially identified, through the European Space Agency (ESA) Climate Change Initiative Land Cover (CCI-LC), around 83 million hectares of abandoned cropland between 1992 and 2015. “We identified abandoned cropland by tracking grid cells transitioning from cropland in 1992 to any non-cropland (and non-urban) class in 2015,” the academics specified. “In other words, abandoned cropland includes all grid cells that were registered as cropland in 1992 and not [as cropland] in 2015.” Cropland grid cells that were transformed into urban land were excluded from the survey.
The Norwegian group used the Global Agro-Ecological Zones 3.0 (GAEZ) modeling tool of the Food and Agriculture Organization (FAO) to identify the cropland suitable for bioenergy production and chose three types of perennial grasses, known as switchgrass, miscanthus, and reed canary grass, as the best options for the future deployment of bioenergy due to their high yields, low cost, and environmental co-benefits.
The potential for PV deployment in these areas was assessed through data from the Climate Model (CMCC-CM) atmosphere-ocean general circulation model developed by research institute Centro Euro-Mediterraneo sui Cambiamenti Climatici. These data were then combined to find the optimal distribution of the two energy sources in an analysis that was not only based on energy potential and yield but also included biophysical aspects, local land use, administrative contexts, and socio-economic feasibility constraints.
According to their findings, of the 83 million hectares identified, around 30% is located in Asia, followed by the Americas, with a 28% share, and Africa, with a percentage of 22%. Europe and Oceania had shares of 20% and 5%, respectively. Different reasons may cause the abandonment of these areas, like topography, geophysical constraints, the decline in soil quality, and land degradation among different environmental, socioeconomic, and political factors. “Nevertheless, socioeconomic drivers are of larger importance,” the scientists highlighted.
The potential for bioenergy in the identified areas was estimated at 35 exajoules (EJ) annually, while that of PV was calculated at around 179 EJ. The academics stressed, however, that the extent by which PV performs better than bioenergy differs regionally, with the latter performing better in the tropics compared to higher latitudes. The best locations for bioenergy were found to be in South America, Africa, and South East Asia, while those for PV, although more scattered than those for bioenergy, were identified on the east coast of South America, Central America, parts of Africa, mid-Europe and South East Asia. “The lowest PV yields are found in Scandinavia and North America,” the Norwegian group stated, adding that 75 million of the 83 million hectares originally identified by the survey are really suitable for solar and bioenergy. Of this portion, around 53 million hectares (68%) is considered optimal for solar and around 25 million hectares (32%) for bioenergy, with the former having the largest share in energy generation, at around 91%.
“By only considering the potential primary energy output of each renewable energy option, the PV potential far outcompetes the one of bioenergy crops at a global level,” the researchers concluded. “However, the consideration of different biophysical and socioeconomic factors provides a more realistic comparison [of] deployment potential.” According to them, the combination of these two energy sources in the identified areas can provide a higher level of development compared to considering their deployment as separate cases.