Solar power is on the upswing. In 2023, 407–446 GW of solar power was installed globally, bringing the total to 1.6 TWdc. To put this into perspective, this was 55% of new power capacity added to energy production. For the first time, a renewable energy source contributed the most to new capacity. In 2024 so far solar is 75% of new capacity. In the US this was 60% of new power generation (capacity is the potential to make energy at any given time, while generation or production is the actual energy produced). In 2023 solar made up 5.5% of world energy production.

The reason for the increase in solar is that it’s the cheapest form of new energy. According to the International Energy Agency (IEA), solar electricity costs $30–60/MWh in Europe and the US, and $20–40/MWh in China and India. Solar is also the safest, with the fewest numbers of deaths per TWh produced (0.02, compared to the worst, 32.72 for brown coal). Because solar is clean and environmentally friendly, making solar cheaper and more efficient will only enhance its advantages. As is often discussed here, there are other considerations to the overall strategy of energy production, such as intermittency, grid storage, and grid upgrades, but we are not close, at least globally, to running into significant issues. We can take solar from the current 5.5% to at least 30% without too much issue, and can push higher with some infrastructure investment.

Along the lines of making solar power better and cheaper – let’s talk about Luminescent Solar Concentrators (LSCs). If we want to make solar power more efficient there are a few approaches. We could make the conversion of photons to electrons (the photovoltaic effect) more efficient. Right now commercial silicon solar panels have an efficiency of 22-24%, which is pretty good. The theoretical limit of silicon is about 29%, and newer materials, like perovskite, have an even higher potential efficiency.

Another approach is to have some kind of layered solar panel, where each layer may have efficiencies in the 20% range but the different layers have different peak efficiencies in terms of wavelength (color) of light, and there are multiple chances for each photon to be absorbed and converted into energy. Yet another approach is a solar collector – bringing more photons to the photovoltaic cell. Mirrors, for example, are an efficient way of redirecting light to a photovoltaic cell.

LSCs are a method of solar concentration. They use luminescent material to absorb light and then re-emit that light (luminesce). This has several advantages. First, LSCs are efficient at collective diffuse light. Solar panels work best with direct light, and the more direct the better. This is why there is a huge advantage to orienting a panel toward the sun, and for large installations even following the sun with movable panels. But LSCs don’t care – they can collect diffuse or scattered light from any direction with equal efficiency. They can then re-emit that light at a specific wavelength (color), and that light can be directed through a process called total internal reflection. This is like a fiber optic cable, where all light that hits the interface at the surface of the cable is reflected internally, so it travels down the cable and never leaves it.

What this means is that you can have a system of LSCs that are arranged to gather diffuse or direct light from any direction. These LSCs then give off light which travels down a fiber to a photovoltaic where the light is made into electricity. The LSCs are semi-transparent and can be of different colors. If you are thinking of a frond of leaf-like LSCs, then you are on the right track. LSCs are like leaves, and they can be arranged just like leaves, connecting to central fibers and brining energy to the photovoltaic device. In fact, trees have evolved to have a very efficient arrangement of leaves. They absorb light, but also scatter light so that it can be collected by other leaves.

LSCs can already be cost effective, compared to solar panels. They are cheaper to make – mostly just glass or plastic with a luminescent covering. PVs, by contrast, are relatively expensive for the same surface area. So it is more cost effective to have cheap LSCs covering a wide area and bringing light to the more expensive PVs. They also avoid the need for expensive tracking systems. Further, they can be made to be more modular, easier to upgrade and replace. The cost competitiveness improved further with larger area covered, and greater variability in light intensity and scattering.

LSCs are still on the steep part of the technology curve. A recent study presents ways to make them even more efficient, by reducing the size of each LSC and bunching them in a leaf-like structure. The hope is that this approach will make LSCs more scalable, cost effective, and efficient. There already is an LSC industry, but it is small compared to the PV industry. We may, however, be getting close to a shift.

It’s possible that in the future we will not have large fields of solar panels tracking the sun and collecting energy, but fields of artificial trees covered with leaf-like LSCs collecting sunlight and directing it down to their trunks where PVs turn the photons into energy.