(The following is from my monthly newsletter. This series began in March 2022 and has continued for nearly a year, with its final installment in February 2023. Below is the “better” edited version I initially emailed my followers.)
Capturing solar energy means utilizing the sun’s energy and turning it into usable energy for life. Plants are the only organisms on terrestrial earth (aside from cyanobacteria) capable of such a feat.
Ecosystems are Powered by the Sun
Plants capture the sun’s energy through photosynthesis to feed other life forms. They have evolved to turn solar radiation into energy via specialized cellular organs called chlorophyll. Some scientific research has theorized that plants formed a mutual relationship with cyanobacteria billions of years ago. Eventually, evolution turned this relationship into a reduced form of bacteria within each plant’s cells.
Natural ecological evolution has enabled animals to take advantage of the energy provided by the plants by eating them; other animals ate those other animals, and so on. Such is the natural food web, which reflects the energy pyramid we’ll see soon.
As we are in the food production business, we also take advantage of the energy plants provide to feed ourselves and our animals (which will eventually feed us). The caveat is how to capture that sunlight and put it to use. The question is how our management decisions can maximize solar energy capture as much as our ecological system allows.
To achieve that, we need to understand how energy flow occurs.
The energy pyramid
The traditional energy pyramid, as shown above, displays how energy flows upwards at various trophic levels. Plants are the first and bottom level, and decay is the final (top) level. In between is the function of life feeding upon each other, from herbivores to apex predators, including humans.
At each trophic level, energy is lost as heat. That heat is a result of cellular metabolism. Energy is also lost in the expulsion of waste. With a loss of energy, there tends also to be a loss of biomass at each level.
What the traditional pyramid does not show, though, is what happens below ground. Plants not only feed animals above ground by sacrificing their leaves, stems, flowers, and seeds, but they also feed organisms below ground by sacrificing their roots.
As above, so below.
However, this second version of the energy pyramid is still ” outdated.” It is the 2D version that does not show how our management impacts the ability to capture more solar energy—or even less.
Introducing the energy tetrahedron.
The Volumetric Change to the Energy Pyramid
The energy tetrahedron is a new way of looking at the energy pyramid. The tetrahedron changes our view from the 2D “triangle,” where all we see is how energy is lost, to the 3D pyramid (or tetrahedron) that shows us the volume of energy produced for the life of this planet by plants. It still acknowledges that energy is being lost, but it’s a drastic change in perception because now we can see just how management increases or decreases the base (or middle) of the shape by three significant factors:
- Time
- Density
- Area
Suppose we can expand any of the three sides of that tetrahedron. In that case, we can increase the volume of solar energy captured and, therefore, increase the volume of harvestable energy at all levels on the energy pyramid. However, if we shorten any side, we decrease the amount of solar energy captured, decreasing the amount of harvestable energy at all levels of the energy pyramid.
Let’s discuss those three sides and how our management can expand them.
The Three Sides
Time:
The “Time” side of the energy tetrahedron can be expanded by extending the time plants grow throughout the season. The longer plants spend growing, the greater the productivity of the stand. And the greater the productivity of the stand, the more solar energy can be captured.
Lengthening the growing season gives plants more time to grow. The timing of when those plants are grazed and how long of recovery period they get plays a big role. If they’re grazed to where they’re growing even to freeze up and snow cover, they will often remain green even though the cold forces them into a state of dormancy.
What better way to collect solar energy than with green, photosynthetic solar panels, otherwise called leaves? The more leaves there are, the better the solar energy capture!
Density:
“Density” on the energy tetrahedron refers to the number of plants per square foot to maximize solar energy capture, which correlates to the number of leaves covering the surface. The greater the density of leaves, the more solar energy is captured.
Think of it like a forest. In a forest, multiple canopies exist to maximize solar energy capture: trees, shrubs, forbs, and some grasses. The open grassland or pasture will be fairly similar, with canopy layers not as noticeable. We usually lie down on our stomachs to see these layers in a healthy grassland.
The whole premise is that if the stand is dense with lots of leaves and plants, more energy will be captured, which means more forage will be available for the animals to graze on.
Area:
The “Area” on the energy tetrahedron is known as the “leaf area.” Leaf area refers to the surface area available for solar energy capture. Basically, the wider and broader the leaves, the more energy is captured instead of narrow, fine leaves.
To maximize leaf area, plants must be kept in the optimum growth stage (see graph below). This means harvesting plants before they’ve had a chance to go into flower, allowing them time to recover, and repeating the process. Most solar energy capture happens when lots of leaf material is green and present. Little solar energy capture occurs when there’s little leaf material present or when most of that leaf material is browning down and dying.
From the graphic above, our best time to capture solar energy is not when quality or yield is highest but when they both meet at the optimal point. That’s when the plants are in their “Phase 2” stage, where the most leaf material is put out after they’ve surpassed Phase 1 and are nearly, but not quite, ready to start on to Phase 3 of their life cycle.
Remember that grasses and legumes are not the only plants that are great at capturing solar energy. Even weeds are great at it. Even though they’re more unsightly and don’t grow where you want them to, they’re still plants and equally capable of capturing solar energy (and carbon) to feed the soil and animals.
Speaking of feeding biology, for next time: nutrient cycling.