I’ve been interested in green electricity for years. When I was 12 my parents got me a K-nex building set that came with a motor and a tiny solar panel. You could snap the pieces of plastic together into all kinds of creations from a stationary dipping bird to a little drag racer. All you had to do to make them move was plug the solar panel into the little motor and get some sun. I was endlessly fascinated by this and was always trying to figure out how to use the tiny solar panel to run other things.
In the case of my K-nex, the solar panel plugged directly into the motor. If the panel was in sunlight, the motor would run, and if it wasn’t, the motor would stop instantly. The electricity wasn’t being stored. This is one of the fundamental challenges with most types of green electricity even at the grid-level. When you plug your toaster into the wall and turn it on the power it’s consuming has been generated at exactly that moment by the electric company. In almost all electricity grids around the world, electricity is delivered on-demand. There is no storage.
This is actually a very complicated thing when you think about it. All the toasters out there, in all the homes and businesses consume some amount of electricity. The power plant running that grid needs to be able to supply as close to that total amount as possible. Too little and the voltage available will drop. Too much and the voltage may damage equipment. Too little voltage happens all the time, especially in summer when people are using air conditioners on a hot day. This condition is commonly called a “brown out”. To correct a brown out condition, a the grid operator must increase power available to the grid. This can be done in many ways including shunting electricity from nearby grids, bringing auxiliary nuclear, natural gas or coal plants online or incentivizing customers to use less power during peak demand conditions.
This is a major management task and in New England, it’s handled by an organization called ISO New England. They actually need to predict what the electricity demands will be each day and tailor the mix of available electricity to meet that need as closely as possible. Remember that there is no storage on most electrical grids, so if generation stops, power stops instantly. You can actually watch this operation in real time for New England at https://www.iso-ne.com/isoexpress/. Pay particular attention to the system load graph. Notice how they have a predicted demand and how close they’re able to keep generation to that demand.
You should also notice that the demand changes significantly throughout an average day. Most types of power generation cannot be easily shut off completely (such as at night when demand is low). This means that the generating stations operate 24/7 even if there isn’t demand. This is why electricity costs can fluctuate depending on the time of day. The price for off-peak power at night is lower to incentivize usage.
How does green electricity factor into all of this? With traditional forms of electricity generation (coal and natural gas mostly) the amount of power being generated/delivered can be controlled to a fairly large degree. Need more power? Burn more coal. Need less power? Burn less coal. Pretty simple. Green electricity (wind, solar, tidal, etc) cannot be controlled in such a way. The two exceptions to this are hydroelectricity and nuclear, though both of those have pretty significant environmental dangers/drawbacks. If it’s a hot summer day, and more electricity is needed on the grid, you can’t just ask the sun to shine brighter or the wind to blow harder.
So in reality, there was never really a green electricity shortage or problem using it. We certainly have the technology. The issue has always been one of storage and the fundamental way our electric grid was designed from the beginning. Without a way to store electricity to buffer the low periods of availability, most green electricity generation is poorly suited to how we operate our electric grids. Recently this issue has been getting some attention and research is being done into how to accomplish this storage. In limited situations, grid-level battery technology is almost to the point of being feasible. One older method of providing on-demand auxiliary power is actually a form of energy storage: pumped hydro.
Pumped hydro works by using electricity during times of excess to pump water up to an elevated storage reservoir. This water is then released back down when needed to provide an extra boost of generation. This works very well but is highly dependent on the local geography. When I was a kid, we used to go on school field trips all the time to a pumped hydro facility (the largest in New England) in Northfield, Massachusetts. They pump water from the Connecticut River up to a reservoir on top of Northfield Mountain. If you live nearby, I highly recommend checking it out. They have a visitor center that explains how it works and you can do an easy hike to the top of the mountain where the reservoir is located. Read more about the facility here: http://www.wbur.org/bostonomix/2016/12/02/northfield-mountain-hydroelectric-station