The Polls Are In

A couple of weeks ago, I asked folks what they wanted from an upcoming post: solar power on farmland, laws about Lunar mining rights, or laser enhanced rockets. The winner is...

A TIE

Solar Power on Farmland and Laser Enhanced Rockets received equal interest. Consequently, I will be doing posts on both. Today we will be looking into making solar power production more symbiotic with farming.

Agrophotovoltaics is a relatively new field of development in the world of renewable energy production. For those of you who are language geeks, you might infer from the name agrivoltaics that it deals with agriculture (farming) and photovoltaics (one of the types of solar electricity energy production). For the rest of you, I hope that this cleared things up. The motivation behind agrivoltaics is relatively straightforward. Traditional commercial-scale solar farms are optimized to do one thing—converting sunlight into electricity. The efficiency of large scale solar farms comes with the trade-off that the land devoted to electricity production can't really be used for anything else*.

As our planet heats up, farmers are faced with the question. What will they do with fields that have climates that no longer match the crops they've grown historically? For many farmers in California, they are making the choice to replace some of their plant-based crops with solar farms. While adding tradition solar capacity to farmland is a great way for these farmers to gain a new source of revenue while reducing water consumption, there are some trade-offs.  

Many traditional solar leases require that farmers sign a 20-year contract—the average life span of a solar farm. For the life of the lease that farmland cannot be used for any other purpose. The 20-year contract is generally considered a good deal for both parties. The farmer has guaranteed lease revenue and the solar company knows that the land will be useful for the operational life of the solar panels. During dry years, where farmers are unable to irrigate all of their lands anyway, the acreage devoted to a solar farm is a boon. Revenue will continue to be earned even if plants don't grow. In wetter years, with good crop prices, farmers may lament the unavailable acreage that could have increased their revenue that season.

Famers who implement agrivoltaic systems on their fields can exchange higher upfront costs for a guarantee that every acre of useable land that they had before installing solar panels is still available for the life of their installation. The risk associated with using agrivoltaics over utility photovoltaics should not be taken lightly. Current published materials indicate that the cost of installing an agrivoltaic to be roughly the same as installing rooftop solar on a home, about $3/watt installed. Depending on how you model the upfront/operational costs of an agrivoltaic system, the cost efficiency for farmers will vary drastically.  

Assuming an installation cost of $2.58/Wac installed (the current low end for electricity installation costs) and using Dr. Ramon Sanchez's solar calculating tool,** we can estimate that farmers and customers would need to buy the electricity wholesale at $0.113/kWhr. The upper bound installation cost of $3.38/Wac would leave us with an estimated wholesale value of $0.148/kWhr. When you consider that the average consumer only spends $0.1332/kWhr on electricity, it becomes more difficult to make a simple recommendation to use agrivoltaics, unless you get clever***. Traditional farming requires a lot of energy in the form of fossil fuels used to move tractors and other equipment, a farmer who embraces local energy production and storage could look at their costs in a very different way. Instead of looking at their solar installation as a way to make money from the sale of electricity on the wholesale market, they could see as a way to reduce the impact on the variability of fuel oil prices.  

Manufacturers are already starting to sell electric tractors. As time goes on, farmers who embrace solar will be able to have a more consistent energy budget for their farm in the form of the mortgage for their solar installation.  

Other potential benefits of an agrivoltaic installation include providing a scaffolding structure for robotic farming technologies. Companies like FarmBot are working hard to make robotically enhanced garden beds that will automatically handle the majority of a garden's lifecycle. The scaffolding structure of the agrivoltaic system could very readily be designed to act as a structural trackway for robotic arms to move across a field, optimizing plant growth while minimizing the number of labor hours needed from humans.  

There is one more idea I wanted to share, but as this article is already rather long, I felt it would be better to give the idea its own post. That being said, the core concept is right below.

• Inflatable algae greenhouse for producing biofuels during the winter months

(I hope you're intrigued, any questions and feedback are welcome)

*There are some options for doing a few other things on commercial solar fields. As an example, you can graze animals off of the grasses that grow around the panels.  

**These calculations were done for San Juan, Puerto Rico (I had some old models from a class project I did last week). For a region with less sunlight, the cost of production would be even higher. We are also assuming a DC to AC conversion efficiency of 82.5%

***If you assume that the agrivoltaic systems are being built to sell electricity wholesale because you need to pay a grid operator to transmit your power to other consumers a lower wholesale cost is important. On the flip side, it is worth noting that the current cost for installing agrivoltaics is heavily impacted by the generally custom nature of the frames used to mount the panels. In theory bulk manufacture of agrivoltaic scaffolds designed to make installation more affordable could lower the effective cost of electricity production.