This Is What I Mean When I Think Of A ‘Solar Farm’

These days, a ‘solar farm’ generally means a field that grows electricity.  And generally, moderate to large PV arrays are considered an industrial use of the land, instead of or competing with food production or other use.

Of course, that doesn’t have to be so. 

This month Kirk Siegler reports about a successful ‘solar gardern’ truck farm in Colorodo [1].  The field features widely separated rows of PV panels, with commercial vegetables growing in between.  The gaps are large enough for tractors to access.

This layout is a compromise between the supposedly competing uses for the land.  The solar array is much less dense than the usual industrial layout, so there is less maximum theoretical output per square kilometer.  At the same time, the crop areas are also less densely planted than usual, and the soil and crops are partly shaded by the PV arrays.  The maximum theoretical food production is less than a single use field would be.

The game is, of course, for the combined electricity plus food crop production to be economically sustainable, and, indeed, profitable.  So, how’s it going?

In this case, the combination seems to work pretty well.  The electric production is connected to the local Grid, so the field generates income pretty much whenever the sun in shining.  Not as much as a single use solar layout would, but way more electricity and income than a field of kale.

At the same time, the vegetable production is solid.  In fact, the partial shade seems to help the plants, and definitely reduces evaporation and the use of irrigation water.  Maybe not as much food production per acre as a denser layout, but more food per unit of water is a very, very important metric in Colorado and most places.

And there are synergies.  The evaporation of irrigation water cools the PV panels, which (at least slightly) increases their efficiency.

I’ll note that there are additional refinements that might be done if they are not already happening.  For one thing, areas not used for crops (i.e., under the PV panels) can be let go to native plant species and possibly for pollinators and other helpful animals.  

The electricity production opens the way to electrify more of the farm operations, including especially, the vehicles.  We can look forward to the day that harvest and delivery to consumers will be done with electric vehicles, vehicles charged at the farm.  The PR advantage is obvious.

This particular farm is notable because it is otherwise conventional.  As far as I can tell, they use standard PV arrays, and the same crops as before.  The main technical move is the designed shared use.

The good news is that, if it works in this case, then specialized PV systems (e.g., more transparent panels) and specialized crops will work even better.  We have not really begun to select and breed plants for this slightly special niche.

What can go wrong?  Well, for one thing, the profitability of this field depends on grid connectivity. Colorado has pushed very hard to require the utility grid to buy solar power from small producers including this farm.  Other jurisdictions are less friendly and even hostile toward such connections, so replicating this case depends heavily on local and regional politics. 

Many farmers and rural communities are less than enthusiastic about wind and solar installations in former farm fields. I think industrial generation systems are viewed as competition to agriculture, and perhaps displacing rural farming culture with something new.  Multiple use layouts like this Colorado farm seem to address these concerns, at least as far as rational economics are concerned.

Overall, this is the kind of thing I would love to do, if I were a young farmer or solar developer!

I’ll throw in one more idea, for free.  As electric vehicles proliferate, there will need to be charging stations everywhere, notably including rural roads and highways.  So every filling station should contract with local farmers to buy electricity right out of the field to charge up the EV chargers.  Might not even need grid connectivity in some cases, if there is enough PV within easy reach of the highway.

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1. Kirk Siegler, This Colorado ‘solar garden’ is literally a farm under solar panels, in NPR News – Energy, November 14, 2021. https://www.npr.org/2021/11/14/1054942590/solar-energy-colorado-garden-farm-land