New Study Examines Impact of Big Solar

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A new UK report looks at the effects of solar parks on the local environment. Can large arrays provide benefits beyond clean energy production?

Environmental Research Scientists at Lancaster University and the Centre for Ecology and Hydrology recently released Solar park microclimate and vegetation management effects on grassland carbon cycling which appears in the latest edition of the journal Environmental Research Letters. Researchers monitored a large solar park near Swindon for a year. Swindon is located in Wiltshire, South West England, 70 miles west of London. The report describes the findings of the first detailed study of the impact of solar parks on the environment, providing vital information for establishing land management best practices at the ever-growing numbers of central-station solar facilities.

The report’s authors, Alona Armstrong, Nicholas J Ostle and Jeanette Whitaker write that “Solar parks may have consequences for microclimate, C cycling, biodiversity, water, soil erosion, air quality and ecosystem energy balances…These impacts may occur at the regional scale, but the physical presence of PV arrays may also promote within solar park variation in climate and ecosystem function. The physical presence of solar parks will impact solar radiation fluxes (and thus temperature), wind speed and turbulence (and thus the exchange of biogenic gases and water vapour) and the distribution of precipitation within the solar park. Given the climate regulation of ecosystem processes, resolving the impacts of PV arrays on the soil and near surface climate within solar parks is essential. The spatial and temporal dynamics of solar park-induced microclimates on ecosystem processes is likely to be different to projected climate change…Further, solar park management, in particular that relating to the vegetation (i.e. seeding, mowing, grazing and fertiliser addition), will be a strong determinant of ecosystem response.”

Some of the results were unsurprising, for instance, they found that soil and air temperatures in the areas shaded by the solar panels were significantly cooler than in the areas between rows which received direct sunlight. Cooling of as much as 5 degrees Centigrade under the panels during the summer was recorded, with effects varying depending on time of day and time of year.  On the other hand, the results of studying the vegetation under the arrays brought more unexpected results.  According to the study;  “The PCA-GLM (Principal Component AnalysisGeneralized Linear Model) results indicated that vegetation metrics and wind speed (which governs CO2 exchange between the leaf and atmosphere…) were more strongly correlated with CO2 fluxes than climate or soil factors. This indicates the pivotal role of vegetation, and thus the importance of vegetation management in the shorter term and vegetation change in response to the microclimate induced by the PV arrays in the longer term, in influencing C cycling at solar parks.”
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The report concludes that; “Land use change for energy generation is accelerating, with the growth of solar parks predicted to continue globally. The effects of this growing land use change on plant–soil processes, which underpin key ecosystem services, is poorly understood. In this study we show that PV arrays can cause both seasonal and diurnal variation in the ground-level microclimate to a magnitude known to affect terrestrial C cycling. We also observed significant differences in above-ground biomass, plant diversity and ecosystem CO2 fluxes which were associated with the vegetation management and microclimate. Given the quantifiable differences in plant–soil C cycling presented here, we argue that there is a critical need for a systematic assessment of the impact of solar parks on ecosystem functioning and the potential to exploit the induced-microclimate effects for co-benefits. For example, the production of crops under PV arrays in locations where solar radiation receipts currently prevent it. Solar parks contribute to climate change mitigation by providing low carbon energy, but the wider environmental costs and benefits need to be taken into account, to ensure they are deployed sustainably.”

What the authors are telling us, is that under current mono-crop conditions, the areas under solar parks (as they are known in the UK) or solar farms are actually losing their ability to capture and store carbon. However, by taking the researchers advice and varying design and plant species, the shaded areas might actually have the potential to increase carbon capture. Depending on the local microclimate, there may be huge potential to grow carbon sinking plants in the cooler, shadier areas under the solar array. For instance, a Swedish report discovered that in the northern  boreal forests is captured by fungus, rather than the trees themselves. Another report from Researchers from the University of Texas, Boston University and the Smithsonian Tropical Research Institute ran computer models on data from more than 200 soil profiles from around the world. They found that soils dominated by ecto- and ericoid mycorrhizal (EEM) fungi contain as much as 70% more carbon than soils dominated by arbuscular mycorrhizal (AM) fungi.

As we can see, fungi play an important role in the carbon cycle, the biogeochemical process by which carbon is taken from the air and captured in the soil. Globally, soil is the biggest single terrestrial reservoir of carbon, far more than the amount of carbon contained in living things and in the atmosphere combined. And where do fungi prefer to grow?  In cooler, shadier areas.

By adding diversity to the ecosystems surrounding large, central station solar arrays, it may be possible for system designers to utilize the types of concepts made popular in permaculture to create solar farms that are truly farms… producing not only energy, but also an array of perennial crops that are both useful in the short term as well as beneficial in the fight against climate change.

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