Tag Archives: solar power

632. Dam Gravity

M. Rehemtulla for QUOI Media Group

Tuesday morning. When I wrote these posts about two weeks ago, I mentioned PG&E. Guess what? They just announced that tomorrow my county is slated for a possible shutoff of power because of projected high winds. Even if that doesn’t happen, a regular power outage is likely. While you are reading this, there is a good chance I will be reading a book by sunlight through the window, because I won’t have any electricity to power my computer. I would find that ironically amusing, except my stove and refrigerator also won’t be working. At this moment I might be eating cold beans out of a can.

Additional, 6 hours later, it is now almost certain that we will be blacked out, and that it might well last up to five days. Posts come to you from WordPress, not directly from my computer, and I have a month of posts in the can so, see you later. Now back to what I already wrote.

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This is a continuation of last post. What does a kid with a toboggan have to do with solar energy storage, you ask? You’ll find out by the end of the post.

If you have any science background at all, please forgive the next few paragraphs as I set things up for something you may not know.

A battery does not hold electricity like a can holds Coke. The electrons which are present inside the battery do not go into your device. They travel from the (-) pole to the (+) pole, and essentially the same electrons are there in a discharged battery as are in a charged one.

It is the flow itself which powers your device. The flow is caused by chemicals inside the battery changing from a high energy configuration to a low energy one. This is true of the lithium ion battery that just burned up your hoover board, and equally true of the car battery in your great-grandad’s 1950 Nash Rambler. Such batteries are recharged by running electricity back through them to return the low energy chemicals to a higher energy state.

In other words, batteries don’t store electricity, they store energy. Chemical energy, and there are many other ways to store energy besides batteries. Let’s look at one.

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Last post I invited you to take a trip with me from the California foothills toward the coast. Now we have dropped down out of the brown hills, have crossed the hot, flat, agriculturally green Central Valley, and suddenly our car turns its nose upward because we have reached the Coast Range which stands between us and the ocean. We are on Highway 152 and to our left is the imposing dam of San Luis Reservoir.

Everyone knows the story of rainfall on mountains. California lives on it. Sunlight on the Pacific raises moisture which gets an uplift first by the low Coast Range and then by the High Sierra. The west side of the Coast range and the western Sierra foothills get winter rain in moderate quantities, and west side of the high Sierras gets a big dump of snow which melts in spring to fill reservoirs all over the western foothills, providing irrigation and electricity to California.

The eastern side of the Coast Range and of the Sierras get squat.

Where San Luis Reservoir is located, there isn’t enough local rain or snow to fill it. Water is brought to it by a system of canals, accumulated in the forebay and pumped up into the reservoir.

Sounds goofy, right? The dam exists to harvest in spring and store for summer, water that has already passed thorough the other reservoirs and would otherwise go to the ocean. Of course it’s controversial; everything related to water in California is controversial.

So what does this have to do with solar cells on the roof? San Luis Reservoir not only stores water, it is essentially a giant storage battery for electricity.

When the water arrives at the forebay, it is pumped, by electricity, up about 320 feet into the reservoir. When it exits the dam to be used, it passes through a hydroelectric generator, recouping much of the energy originally used to lift it. It isn’t 100% efficient system, but nothing is.

Batteries store energy by chemical change. There are innumerable other ways to store energy, many of them new, complicated, expensive, and with unknown dangers. Carrying a load uphill to store gravitational energy, and getting that energy back when the load comes down is old, simple, and well known. Kids have been doing it with toboggans ever since there have been snow, toboggans, and kids. (See, I told you I’d explain that photo.)

In California, people have been doing the same thing for a hundred years or more in tankhouses, water tanks attached to houses which allow gravity flow so you don’t need to turn the well pump on every time you open a faucet. The one shown here even used wind power to get the water out of the well and up into the tank.

This was done for the sake of the water, but it could as easily be done for the sake of storing energy. With twin tanks, one high and one low, there would be no reason to “use up” the water. It could even be structured in tandem with the house’s normal water usage.

I submit that a good engineer could turn this into a cheap, simple, and easy way to harvest solar power all day and use it all night, without frightening Mother Nature. You would simply use excess solar electricity to pump water upward all day, and drain it back through a turbine and generator that night.

How much water, how high would we have to pump it, how much would the raised tank cost? Would it be practical? Would it make money for the ones who provide the system? Who knows; that’s for some young engineer is search of a project to determine. Will it be you?

Since I didn’t invent this technique, I can’t ask for royalties once you perfect it. I will, however, expect a finder’s fee.

And if any of you out there know of someone who is already doing this, I would love to take my tongue out of my cheek and hear about it.

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631. To Grid or Not To Grid

Although I fully believe in it, I normally steer clear of talking about global warming, wind and solar power, and the impending end of civilization. There are plenty of sources for that, and I don’t want to get caught channeling PBS.

However, speaking of PBS, there was a bit about the problems of energy storage as part of the solar solution yesterday (Sept. 27) that made me realize I knew a few odd things from a few odd sources that were worth sharing.

I live in California, in the foothills of the Sierras. PG&E provides my electricity, but every time it rains more than a tenth of an inch, my power goes out for six hours. This has been true for decades, not just since PG&E went bankrupt for its role in recent fires and told us all that it was going to shut our power off every time the wind comes up.

It’s enough to make you want to go off the grid.

We’ve all grown up with the grid — even me. The first house I remember, about 1950, had no plumbing, no running water, and an outhouse out back, but it had electricity coming in from elsewhere through the wires. Consequently, I can’t honestly tell Lincolnesque tales of reading by a coal oil light (except when tornadoes took the wires down).

The history of the grid goes back to Tesla and Edison fighting the battle of AC vs DC, and continues through the REA. (That’s the Rural Electrification Administration which brought electricity to isolated farms throughout America in the thirties.)

The grid is wonderful; it has given us our present level of civilization.

The grid is terrible. It is a dinosaur, completely out of date and tying us to the mistakes of the past.

As is so often the case, both of those statements are true. No one decided to choose centralized production of electricity with a massive distribution system. Its alternative, dispersed production, was simply not an option in the past.

That is no longer the case. A system of solar power through electrovoltaic cells can now be built one roof at a time. (There are other alternative sources of electricity, but I’m only going to talk about one in this post.)

There is a big problem, though. Solar cells only generate sufficient power during reasonably sunny days. There is also a solution, but it is only going to work for a few years.

In today’s installation of rooftop solar cells, homes mostly draw on the grid at night and “turn the meter back” during the day. Quite clever, for now. It amounts to using the grid like a giant storage battery. But if enough rooftop solar installations try this trick, daytime generated electricity will become essentially a waste product from the viewpoint of the owners of the grid.

Of course you could have a mega-array of solar cells in America lighting up India at night, and a similar array in India lighting up America at night, but that’s turning the grid into a GRID. It’s good science fiction, but not very practical.

If you want off the grid — and eventually the grid will want you off, if you are a daytime energy generator — you will have to find a way to store your daytime energy for night time use.

Storage batteries are heavy and expensive, not only in the owner’s dollars but also in terms of world resources. They also blow up. I’m not just talking about lithium ion batteries; car batteries blow up too from time to time.

If you could invent the perfect battery — light, safe, cheap, environmentally friendly, capacious — it would make you more money than cold fusion.

If you could invent both, you would solve all the world’s problems except overpopulation and religious strife. You could run for God and probably win.

Heinlein invented the perfect battery, the Shipstone, and built a whole universe around it, but it’s harder to do in the real world.

Coming back down to the individual home owner, what is needed is a non-battery source of energy storage to make those solar cells practical.

I have an idea! Actually it isn’t mine; it already exists, and I can point to it.

Hop in the car with me and let’s take off for the coast. I drive by something every time the foothills get too hot and I need a Monterey fix down by the ocean. I’ll show it to you.

We’ll go there Wednesday.