Agrivoltaics: What Crops Grow Best Under Solar Panels?

This project follows the Scientific Method. Review the steps before you begin.

Selecting and Preparing Your Plants

1. Select species of garden fruits or vegetables that grow well in your climate, such as tomatoes, lettuce, strawberries, etc. Ask an adult for help or ask for advice at a local nursery if needed. Some libraries also offer free seed packets and even gardening classes. Depending on the amount of time you have available for your experiment, you can either germinate seeds or purchase starter plants at a nursery or hardware store. 
2. We recommend doing the experiment with your plants in pots rather than planting them in the ground, so you do not have to worry as much about weeds. 
3. Depending on your climate, the plants you select, and the amount of rain, you may need to water your plants.
4. If you are in the northern hemisphere, the sunniest location would typically be on the southern side of a house or building, unless trees or other buildings in the way cast shade. 
5. You may need to consult a local nursery or read the instructions on seed packets to determine how many hours of sunlight per day are considered "partial shade" for specific plants. This location may typically be on the east or west side of a house or building, so it receives only morning or afternoon sunlight, not both. You could also use a large object (such as a piece of plywood or outdoor furniture) to create shade.
6. Before you start your experiment, decide how you will evaluate growth for each plant species, and when you will end the experiment. See the Science Buddies Measuring Plant Growth resource for some ideas. At minimum, we recommend recording the following for each plant during your experiment. Record your data in a table like Table 1 for each plant.
   1. Weather conditions each day
   2. Amount of water applied each day
   3. Plant height over time
   4. Number of fruits or vegetables produced over time
   5. Weight of fruits or vegetables produced by the plant
   6. Other observations may depend on your plant species. For example, discolored leaves could indicate that the plant is unhealthy. 

Growing Your Plants

1. Follow the instructions on your seed packets or plants to plant them in pots. Some plants may come in starter pots from the store (Figure 2), and others may need to be transplanted to larger pots. You should have six of each type of plant. Label your pots so you can keep track of your data later (e.g., Lettuce Full Sun #1, Lettuce Full Sun #2, and so on).

Image Credit: Ben Finio / Science Buddies

Figure 2. Basil plants in starter pots. A piece of plywood provides extra afternoon shade for three of the plants.

2. For each type of plant, place three pots in a location that receives full sun. Place three pots in a location that will only receive partial sun (Figure 3).
   1. Check the seed packet/plant instructions for the definitions of full sun and partial shade (hours of sunlight per day).
   2. Make sure both locations will receive the same amount of rainfall. For example, do not place three of the pots directly under a tree or on a porch for shade if this means they will receive less rain. 

Image Credit: Ben Finio / Science Buddies

Figure 3. Two sets of three tomato plants. The plants on the left side of the image are on the south side of the solar panels and receive full sun all day. The plants on the right in the image are on the north side of the panels and only receive afternoon sunlight. (Note: these plants are planted in the ground instead of in pots.)

3. If needed, take steps to protect your plants from pests (bug netting/spray, fencing, etc.).
4. For each plant, each day:
   1. Record the weather conditions.
   2. If you water the plants, apply water in measured quantities, and record the total amount.
   3. Measure the plant's height (the distance from the ground to the top of the plant).
   4. Count the number of fruits or vegetables growing on the plant.
   5. If any of the fruits or vegetables are ripe, harvest them and weigh them.
   6. Record any other observations you make.
   7. Apply any other care needed by the plants, such as removing pests.

6. Keep making observations for as long as you have available to do your experiment. Depending on the time you have available, you may need to make your final observations and measurements before the crops are fully mature (for example, before tomatoes are fully ripe).
7. For additional measurements, you may need to remove the plants from their pots at the end of your experiment (for example, to measure dry plant mass by drying the plants in an oven, or to measure the plant roots, as described in the Measuring Plant Growth resource). Record these observations separately for each plant. 

Analyzing Your Data

1. Once you have collected all of your data, compare the full sun vs. partial shade conditions for each plant species. For example:
   1. Calculate the total weight of the fruits or vegetables produced by each plant. 
   2. Calculate an average weight for the full sun plants and the partial-shade plants for each species.
   3. For each plant species, make a bar graph with the average total weight on the y-axis and the shade condition on the x-axis.
   4. Repeat this process for other metrics that you measured (plant height, etc.).
2. Compare full sun vs. partial shade conditions for each plant species.
   1. Did any plants perform better in partial shade than in full sun?
   2. Did some produce more fruits or vegetables overall?
   3. Did some require less water?
   4. What other comparisons can you make?
3. Based on the results of your experiment:
   1. Which crops would you recommend be planted on an agrivoltaic farm?
   2. Which crops should be avoided?
   3. How could you improve conditions on an agrivoltaic farm for plants to grow even better?