Solar power is a relatively new form of energy, commercially originating in Bell Labs in 1954, it’s had an exciting development. Not only has it gotten 10 times more efficient since 1954, but it has also gotten 10,000 times cheaper. Solar energy is important today not only because it is the most economical form of energy, but it also does not pollute the atmosphere like oil, gas, or coal. So, why isn’t solar power the most popular form of energy yet and what does it have to do with ducks?
It’s only been in the last 10 years that the price of solar cells has really fallen due to a 2004 incentive by China that encouraged mass production of solar cells. Other companies around the world had to either innovate or shut down. As a result, we now have improved, cheaper technology.
Of course, price is not the only factor that has been a challenge to solar energy. One huge problem for solar in the past has been the duck curve. What's the duck curve you ask? It's the curve that represents our energy usage throughout the day and how it relates to solar energy throughout the day.
You'll see a dip in energy from non-solar sources needed for electricity in the middle of the day. Why? The sun shines the brightest in the middle of the day and our solar cell technology can produce the most energy then. What's the problem? Other sources cannot ramp up quickly enough to keep up with the increase in energy demand in the afternoon that comes from the sun setting and people getting back home. From the chart above, you can see California’s solar and natural gas crossover, indicating an inefficiency.
So, the problem with solar is that the sun is not always shining on us. When the sun is shining on the solar panels, such as in the middle of the day, there’s an abundance of solar energy. Once the sun sets, there’s no more solar energy produced. That means we have to either find a way to store solar energy, and/or to have an alternative source of energy when we don’t have access to solar power. Right now, the alternative source of energy we’re using for that is natural gas, but it could be another renewable source such as wind, biomass, or geothermal.
The more interesting solution to the sun not always being in the sky for us is to be able to store the abundance of energy generated throughout the day. There are multiple forms of energy storage from short term energy storage that lasts a few hours such as those solar powered lights you’ll see decorating sidewalks in conscientious suburban neighborhoods to long form energy storage for weeks or months.
The current front runner for a solution to store solar energy to be used throughout the day is lithium ion batteries. Lithium ion batteries are significantly better at storing energy and can store more energy than lead acid batteries. Lead acid batteries don’t offer the same energy storage ability as lithium ion, but are currently cheaper. As solar adoption spreads, so has the adoption of lithium ion batteries. The Tesla Powerwall was a big driver in increased funding and study in this area.
The Tesla Powerwall was announced in 2015 and has driven the majority of funding, research, and development in solar storage. Currently, Tesla is on the Powerwall 2, which can hold up to 13.5 kilowatt-hours (kWh) of power. For reference, the average American household consumes about 30 kWh of power a day, so this battery can hold enough charge to power your house for a little more than 9 hours. So we can see that lithium ion batteries are great solutions for residential homes, but what about utility grid scale solar solutions?
Currently, lithium ion batteries are also the most popular and suggested option for utility grid scale solar solutions. Solar plus storage has become more widespread, and pretty much standard to see over the last few years as solar cell technology advances and the price of lithium ion batteries drop. In 2017, solar plus storage solutions accounted for about 4% of solar photovoltaic systems, with NREL predicting 27% by 2023. Just to give you another insight into how solar is growing fast is that we are actually at 26% solar + storage systems already, in 2021.
What are some other solutions to the storage problem for solar energy? Other solutions that have been proposed are using gravity based solutions like pumped hydro, heat based solutions like molten sand, or an augmentation to the storage system originally introduced as a “smart grid” and now called grid modernization in the industry. The smart grid will not only help us with storage solutions, but also allow us to fix electricity distribution problems on the fly.
There are two well known gravity based solutions to storing energy. The most commonly seen and heard of is pumped hydro. Pumped hydro is using two water reservoirs, one low and one high, to store extra energy. Energy generated during the day that isn’t needed is used to pump water from the lower reservoir into the higher one. During the night, when solar energy isn’t readily available, water from the higher reservoir will drain into the lower one, rotating a turbine and generating electricity. There’s also a company called Energy Vault that is creating a “tower of power” gravity based solution, picking up and dropping tons of concrete blocks as a way to store power.
Heat based solutions such as molten salt storage being created by Malta, or storing heated water underground, are based on capturing heat from the sun during the day and turning it into energy during the night. When there’s no energy from the sun, the heat is captured and turned into energy the same way that steam engines work. The most exciting part about heat based solutions is seeing all the different materials that people use: sand, carbon, water, you name it, if it can be heated and stored, someone’s trying to make a heat based solution out of it.
The innovation for storage solutions that is most exciting is the smart grid. Smart grids are an Internet of Things derivative based solution. What makes a grid smart? Great question, it is the ability to send both data and electricity. Some of the inherent advantages of smart grids over the current grid structure include more granularized energy monitoring and metering, and a decentralized platform. By itself, smart grid technology cannot store energy, where it shines is the distribution of energy, fixing blackouts, and managing the operations behind energy storage.
As lithium ion battery prices fall and smart grid technology evolves, the future for solar plus storage solutions looks bright. The smart grid is a great use case for blockchain technology and this 2021 paper shows that the cutting edge of scientific research agrees. As a green energy company built on the transparency of Blockchain, we will be building our own smart grids. Sign up to stay updated with the quest to build 50000 MW of solar power across America by 2030.