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De-centralized power and feeding the grid

Bert Bates
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Sheriff

Joined: Oct 14, 2002
Posts: 8883
    
    5
From the "wouldn't it be great?" dept.:

Wouldn't it be great if neighborhoods had their own clean power sources for electricity? They could use the power directly, and when not being totally used they could feed the grid for credit? Even if such power sources only supplied some fraction of the neighborhood's need, wouldn't it still be great?

The line of research that most interests me is solar power, more specifically some sort of solar system that can be constructed at the "medium technology" level. By "medium technology" I mean technology that many small, independent companies can create. Perhaps more than you could create in your garage, but less than requires some big mega-corporation's infrastructure.

I recently read an awesome book (well, I thought it was awesome), called "Sustainable Energy: Without the Hot Air". I'm not an expert in these technologies, but it seemed to me that the author took a very objective, dispassionate look at all of our options. Here's a link:

http://www.amazon.com/Sustainable-Energy-Without-Hot-Air/dp/0954452933/ref=sr_1_2?s=books&ie=UTF8&qid=1284137330&sr=1-2

One of the things that I took away was that because of the U.S.'s wonderful southwestern desert region, we should get a lot of our energy from solar power, and more specifically from mirrors. To that end I've been noodling along, researching a two-piece solar system:

1 - medium tech mirrors
2 - some sort of stirling engine

It seems like there are medium or even low tech ways to build fresnel mirrors, I'm still searching for that mythical 1-5 hp stirling engine. I've even considered whether, on a local basis, steam engines could be resurrected?


Spot false dilemmas now, ask me how!
(If you're not on the edge, you're taking up too much room.)
Pat Farrell
Rancher

Joined: Aug 11, 2007
Posts: 4659
    
    5

Problem with solar power (other than raw cost of the solar panels) is that the places with lots of sun and space don't have many people. You need the power near where the usage is. Moving power tends to be very expensive. Moving it a long way has losses to deal with, but the biggest cost is the NIMBY factor. Not in my back yard. No one wants to see power lines, and no one will live under them.

Same problem with wind power.
Ryan McGuire
Ranch Hand

Joined: Feb 18, 2005
Posts: 1013
    
    3
Bert Bates wrote:
1 - medium tech mirrors
2 - some sort of stirling engine

It seems like there are medium or even low tech ways to build fresnel mirrors, I'm still searching for that mythical 1-5 hp stirling engine. I've even considered whether, on a local basis, steam engines could be resurrected?


Shirley you've seen this book: How I built a 5 Hp Stirling Engine. I see in the description of that book the following:
There isn't quite enough detail on the drawings to simply build an engine directly from the book, but a good machinist should be able to fill in the missing details.

Is that where your "mythical" description came from?


It would seem to me that stirling engines are the way to go over steam. If I understand correctly, they have a lower cost per kWh than steam engines. Also, on the face of it, it seems that stirling engines would require less maintenance, since you only have to worry about a heat supply but NOT a water supply. (You may want to water cool your stirling engine, but the water would be recirculated as opposed to consumed.)

This coming from someone that has never had to maintain either type of engine.
Collin Dugas
Ranch Hand

Joined: Jul 10, 2009
Posts: 91
As Pat mentioned moving power from where it is generated to where it is required is one problem.

Also, if this ever achieves any scale then we need to worry about keeping the volume in limits. The power grid is not an elastic system where we can take and put back as much as we use or generate. It can fluctuate only within a range.
Bert Bates
author
Sheriff

Joined: Oct 14, 2002
Posts: 8883
    
    5
About "moving power"...

I am admittedly on thin ice here, I haven't done much research on this point... but I thought that for much of the U.S., the "grid" is mandated to accept power from individual homes. In other words, assume a homeowner has solar panels or some such, and is also on the "grid". Whenever the homeowner's solar panels produce more power than the homeowner needs, the homeowner is free to push the excess power onto the grid and get a credit for that.

No doubt the "grid" itself loses a lot of efficiency as it moves "power" from spot to spot, but that seems besides the point when discussing everyone's individual ability to feed it (the grid).

Pat Farrell
Rancher

Joined: Aug 11, 2007
Posts: 4659
    
    5

Bert Bates wrote:but I thought that for much of the U.S., the "grid" is mandated to accept power from individual homes. In other words, assume a homeowner has solar panels or some such, and is also on the "grid". Whenever the homeowner's solar panels produce more power than the homeowner needs, the homeowner is free to push the excess power onto the grid and get a credit for that.


I believe that is state-by-state. I know California law requires this. I do not think it is widespread.

Today, the peak load for power is during the day in the summer, when everyone has the A/C on, and at night in the winter, when all the electric heat is on. Solar power won't do much for the night time load. It could help the daytime A/C load.

The US 'grid' is woefully under maintained. None of the power companies have any incentive to invest in it, so they have not. Before we could expect the grid to move even a fraction of the load from places with wind or sun to where its needed, we would need to spend billions. It would be nice to make the grid smarter while we are at it, but that will cost billions more.

There is a bit of the classic tragedy of the commons here about the grid.
Ryan McGuire
Ranch Hand

Joined: Feb 18, 2005
Posts: 1013
    
    3
Bert Bates wrote:About "moving power"...

I am admittedly on thin ice here, I haven't done much research on this point... but I thought that for much of the U.S., the "grid" is mandated to accept power from individual homes. In other words, assume a homeowner has solar panels or some such, and is also on the "grid". Whenever the homeowner's solar panels produce more power than the homeowner needs, the homeowner is free to push the excess power onto the grid and get a credit for that.

No doubt the "grid" itself loses a lot of efficiency as it moves "power" from spot to spot, but that seems besides the point when discussing everyone's individual ability to feed it (the grid).



My understanding matches yours, Bert.

But I think a spectrum of scenarios is being discussed here. In a fairly densely populated area, such as a city, a suburb or even a non-wilderness rural area, individuals feeding a few kWh per day into the grid is no big deal and there's little if any loss to speak of. It sounds to me like Pat and Colin are talking more about something like a large solar panel farm in the middle of the desert or maybe a "field" of wind turbines a couple miles off shore. In those cases the total distance and/or the number of "hops" from producer to consumer may make the process inefficient.

As for Colin's "elastic" comment...
Huh, I guess I never concerned myself with the possibility of me producing more power than CEI (Cleveland Electric and Illuminating) could take in. I'm sure there is indeed such a limit, but I'd be surprised if I ever come close to it. Then again, maybe the system is less elastic than I thought. Now that that's on my radar, I'll definitely look into the specifics before firing up my corn husk powered stirling engine.

I imagine that IF I were ever going to produce more power than the electric company could handle, we'd work out some sort of arrangement ahead of time where they install the necessary equipment to handle what I produce. Surely they can't complain about getting power from equipment they don't have to pay to maintain. ...it seems to me.

But again, I think we're each thinking about slightly different scenarios.
Bert Bates
author
Sheriff

Joined: Oct 14, 2002
Posts: 8883
    
    5
Again, not well researched, but I thought that the grid had been moving lots of power around for a long time? (Enron?) Again, no argument that the grid needs lots and lots of TLC - billions doesn't seem unreasonable - but I wonder if that's not necessary regardless of whether homeowners are feeding it or not?

So I think the tragedy of the commons perspective can be very useful, and I'm sure it's useful in general when looking at how the U.S.'s infrastructure needs a lot of help, but that discussion seems mostly tangential to the grid feeding issue.
Pat Farrell
Rancher

Joined: Aug 11, 2007
Posts: 4659
    
    5

Bert Bates wrote:Again, not well researched, but I thought that the grid had been moving lots of power around for a long time? ..... billions doesn't seem unreasonable - but I wonder if that's not necessary regardless of whether homeowners are feeding it or not?


The grid has moved power from a few point sources to a modest number of distribution stations for a very long time, many decades. Having lots of generation points is a whole new thing.

I agree that we need a smart grid, the question is how pays for it and what is the political pressure to cause the change?
John Eipe
Ranch Hand

Joined: May 23, 2008
Posts: 215
It's high time the masses became aware about energy conservation. As stated above, solar energy is a good source in tropical countries. In my father's native village people are still uneducated but a few who comes out educated and they do what they can.

Check attachment.
PS: I don't personally know anyone in the picture.



[Thumbnail for images.jpeg]



www.cs-repository.info
David O'Meara
Rancher

Joined: Mar 06, 2001
Posts: 13459

Thanks for saying Enron before I did. In some ways the problem with the power system in the USA may be due to them. I do know however that individuals selling excess power back to the grid is possible in many countries including Australia and Germany. @see microgeneration.

The specifics on the network change required is beyond me, but behaviour of power production is significantly differently during peak and offpeak periods and it helps for stations to have additional production during peak and hence pay more for this. Counties also have separate peak and offpeak pricing encourage some activities to move to these periods. The enumeration for microgeneration matches accordingly.

Rather than reselling to the network it is possible to store the power locally, but advice I was given is that the price and lifespan of batteries makes this prohibitive and the chemical make up is also a deterrent for those doing it for the environment.

Going back to my Mechanical Engineering days, the Stirling engine is typically a fixed speed, fixed power engine. Since this was not as good a fit for general use as the internal combustion engine, it doesn't get used much.

The main issues are the internal fluid (helium is best but leaches through the metal) and the heat exchanger. There are better and more exotic options for the second part than when I looked at them, but from memory the heat change should be long lasting so the cost would be low when amortized over the life of the engine.

Balance was also an issue and s mate did Honors research on a design that rattled less, but less of an issue since they usually sit one the ground. They also have less parts than other engines and are typically much more reliable.
Bert Bates
author
Sheriff

Joined: Oct 14, 2002
Posts: 8883
    
    5
David,

Sounds like you know a lot about this stuff!

First off, I recently read that they're making some real progress using flywheels to store energy. I could imagine that being medium-tech, but maybe not.

Also, I'd appreciate it if you could share some links or suggestions along the lines of steam or stirling or other "heat" engines...

Thanks,

Bert
Pat Farrell
Rancher

Joined: Aug 11, 2007
Posts: 4659
    
    5

Bert Bates wrote: I recently read that they're making some real progress using flywheels to store energy. I could imagine that being medium-tech, but maybe not.

The concept of using a flywheel to store energy goes back a long time, ancient Greeks or maybe earlier.


Its low tech to make a wheel out of iron or steel and spin it to a few thousand RPM for storage.

Its high tech to make the wheel out of ceramics or carbon fiber, and spin it to many hundred of thousands of RPM.
David O'Meara
Rancher

Joined: Mar 06, 2001
Posts: 13459

Nothing official, but happy to start searching. Something I have been considering for ages and just thinking about over time. Sounds like a common passion! I hadn't considered stirring engines and flywheels though.

My own thoughts on energy generation were broader but less targeted. Solar and wind are common sources of energy but water down a drain pipe can be tapped too

The thing I like about the sterling engine is that it could potentially be set up to tap waste heat and return some as reusable energy.

I also love the flywheel idea since research has been put into them in recent years to assist in storing and releasing energy in hybrid and electric cars. I had been looking at solutions like using potential energy from raising and lowering weights.

Rather than direct storage I was also considering using generated energy to offset other energy use. One example is pumping water into raised water tanks. While the water could be poured out and used to run a generator, the main purpose is to provide water pressure, and using local generated power saves pumping water into the tank using network electricity.
Pat Farrell
Rancher

Joined: Aug 11, 2007
Posts: 4659
    
    5

David O'Meara wrote: One example is pumping water into raised water tanks. While the water could be poured out and used to run a generator, the main purpose is to provide water pressure, and using local generated power saves pumping water into the tank using network electricity.


There are a lot of utilities, at least in the Eastern part of the US that do this on a large scale. They have dams and pump water up during off-peak times, and then let the water down, and power generators during peak times.
Bert Bates
author
Sheriff

Joined: Oct 14, 2002
Posts: 8883
    
    5
Pumping water makes sense. Somewhat relatedly, I have a friend in Colorado who's looked into putting a micro-dam on a small stream on his hilly property.

My favorite lines of thinking center around low or medium technology because I'm a de-centralist by nature, and also because it would be great if solutions could be offered around the world. So for instance, I do have plans for making a very low tech Fresnel mirror that is supposed to do a decent job of making a heat source. Now I just want something useful to point it at
David O'Meara
Rancher

Joined: Mar 06, 2001
Posts: 13459

You want something that can run on ambient heat? This could be your primer.
http://www.thinkgeek.com/geektoys/science/9e84/
Chris Baron
Ranch Hand

Joined: Mar 21, 2003
Posts: 1049
Here is an article about Feldheim, Germany's first completely energy independent village.

Feeding the grid was pushed through here by the Green Party against a cartel of energy suppliers that shared the grid. It was political possible with the amplitude front against nuclear power throughout society and as i read here, on the typology of the existing, connected grid. Now it's possible that everybody can sell energy. The houseowner with solar panels on the rooftop, a farmer who generates power from biogas. There are even business models where investors hire a rooftop, install their solar cells and sell the energy for a fixed price. In my opinion that's the best idea politicians had in a long long time. The drawback is that we subsidize the market for sustainable energy with higher bills for conventional electricity.

Regarding the storage of energy: what's wrong with batteries?
I think for homeowners it's best to have a mix. A well insulated house, a small windgenerator and solar panels. I personally find small geothermal installations fascinating. Just with a ~1.5 meter deep hole you can have the supply of a constant base temperature and you only have to balance the delta to the comfort temperature (coldness and warmth). I really fell for these baskets.
Pat Farrell
Rancher

Joined: Aug 11, 2007
Posts: 4659
    
    5

Chris Baron wrote:Regarding the storage of energy: what's wrong with batteries?

Just about everything. For starters, they are all made with toxic and often lethal materials. Then there is the minor engineering fact that they provide a small amount of power over time, whereas peak load needs are lots of power right now. No battery can deliver that. Then you have to look at their low power density per cubic foot/meter. The list goes on and on.

Batteries are great for small amounts of power where portability is king. If you want even a modest amount of power, you need huge and heavy batteries (look at any car battery). There is no portability in solar, wind or hydro power, they are fixed, batteries are a poor fit from a simple engineering view, let alone economics.
Chris Baron
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Joined: Mar 21, 2003
Posts: 1049
Ok,
but assumed that you have an extra 12V circuit in your house they should be OK with the power supply. I'm talking about lamps and other devices that consume low energy and are cheap to buy. Of course there are a all kind of stuff available for motorhomes and yachts but those are usually expensive. The rest like the fridge or a washing machine could be powered conventionally until there is a good heat engine available. And regarding toxics: the solar battery chargers are very similar to car batteries and almost maintanace free.
Pat Farrell
Rancher

Joined: Aug 11, 2007
Posts: 4659
    
    5

Chris Baron wrote:And regarding toxics: the solar battery chargers are very similar to car batteries and almost maintanace free.


"Chargers" don't store power. All batteries are full of toxic chemicals. Some take very little maintenance, but they still wear out, and then you have to get rid of them. Plus mining the toxic chemicals is another concern.


The battle of DC power vs AC power was done at the end of the 1800s and into the early 1900s. Running DC around your house is an engineering disaster.
Chris Baron
Ranch Hand

Joined: Mar 21, 2003
Posts: 1049
But for car batteries exists a recycle system too. Actually all batteries have to be returned here. And i think it's still better and cheaper than rising a huge water tank and buying a generator.
Pat Farrell
Rancher

Joined: Aug 11, 2007
Posts: 4659
    
    5

Chris Baron wrote:But for car batteries exists a recycle system too. Actually all batteries have to be returned here. And i think it's still better and cheaper than rising a huge water tank and buying a generator.

Depends on the scale. Car batteries are lead and acid. The lead is very toxic. The acid will burn through your skin. Managing them is not easy. We live with them for cars, because we have, as a society, decided that we want cars, and the environment be damned.

Once you build the lake or huge water tank, its very environmentally friendly. Water is not used, just moved. Sure the motor to pump, and the generator to recreate waste some power, but the whole point of the process is to keep the main power plants running at their optimum efficiency. The power to pump up the water is free, as it comes from the process of making the main power plants more efficient.

I think you need to do a bit more research.
Chris Baron
Ranch Hand

Joined: Mar 21, 2003
Posts: 1049
Yes, i think it really depends on the scale. You talk about terraforming and i talk about a little off grid house on a euro-sized piece of ground

What do you think about the stirling heat engine, Pat?
Paul Anilprem
Enthuware Software Support
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Joined: Sep 23, 2000
Posts: 3334
    
    8
Being self sufficient in power is something I have been thinking about since quite some time. I truly salivate over the options that folks in US/Europe have for producing their own power - from sterling engine, solar panels, geothermal cells, to what not.

In India, the constraints are really severe, in terms of cost/availability of raw material, access to any machining workshop, or just plain geography. So I have had several ideas but I could never go from idea to implementation because, in my mind, I try to play the devil's advocate and in the process it turns out that idea is impractical or theoratically impossible.

I have one idea that I would like to implement but I don't know how to work out the theoretical aspects of it so that I can determine whether it is viable or not before moving to practical implementation. May be someone here can shed some light:

The idea:
The only thing available in India in abundance is Sun (well, atleast 9 months in a year) and I have used a simple Solar Cooker quite a bit to cook food. It is not instant but you can easily cook things like rice, meat, lentils, vegetables etc in 3-4 hours. (The cooker uses only one 2x2sq ft regular mirror. That's it.) I know that using more number of even simple mirrors (not even concentrators), the tempratures in a closed container can be increased even above 100C.

As shown in the attached image, I want to circulate water real fast so as to drive a small turbine. Water would be heated at the ground level using Sun's heat. It will be connected to a cooler on the top of the building. So as water at the ground level heats up, it will be forced to travel upwards in one direction (using the unidirectional valve). It will be cooled at the top and flow downwards from the other end. This flow of water will cause the turbine to turn and produce electricity.

Solar water heaters already work this way, and I am only trying to extend the idea.

Question: How do I calculate various parameters such as Temprature difference, pipe diameter that will be required to produce a steady flow. For example, if I want to generate say 100 Watts/Hr, then what must be the temprature difference and the size of the water pipe that would be required?

I do feel that it wouldn't work. But how do I theoretically prove that it wouldn't work? Any ideas?




[Thumbnail for waterflow.PNG]


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paul wheaton
Trailboss

Joined: Dec 14, 1998
Posts: 20721
    ∞

What about converting your driveway and part of the road in front of your house into a solar collector? Apparently, the cost of asphalt is so high now, that using a type of roadway solar panel might be cheaper - and provide power.

http://www.tinygreenbubble.com/eco/environmental/solar-energy/item/981-follow-the-solar-brick-road


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Pat Farrell
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Posts: 4659
    
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Paul Anilprem wrote:Question: How do I calculate various parameters such as Temprature difference, pipe diameter that will be required to produce a steady flow. For example, if I want to generate say 100 Watts/Hr, then what must be the temprature difference and the size of the water pipe that would be required?


This is the kind of stuff that a mechanical engineer does all the time. You start with energy into the hot array, factor in the efficiency, and calculate the net heating per square foot/meter of the working fluid (water here). The heating energy will raise the mass of the water an amount of degrees, its a trivial algebra equation with the right coefficients. Of course, its energy over time to raise a mass of water delta T degrees over time. Warm fluid (air, water, etc) are lighter than colder, so you just have to run the pipes uphill.

You can calculate the change in weight (delta pounds or delta newtons) from the difference in temperature. Subtract out a suitable lose for friction, and you have the "head" or pressure delta. That is what you have to drive your engines, woolen mill, etc.

But unless you are heating it a lot, your "delta T" will be pretty small, so your pressure difference will be very small, and your free energy to drive the turbine will be vanishingly small.
 
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