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Stuart Davis

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since Nov 25, 2011
Santa Cruz Mountains, CA
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Recent posts by Stuart Davis

Hi Jerry, It is an advantage to use a pure sine wave inverter from the standpoint that it will run any kind of load. Pure sine wave inverters are more efficient as well. You’ll get more out of your battery bank and solar modules as a result.

Some inductive loads will not work well with a modified sine or square wave inverter because of the higher frequency harmonics of a modified sine or square wave. These high frequency waves cause heating in the core material of most inductors/transformers that are designed for use at 60 Hz. For example a step down transformer in a piece of equipment would likely get hot and eventually fail if ran on a square wave. Many AC motors accept the AC power directly without any filtering or conditioning and therefore being inductive devices may be damaged and fail prematurely. I had a blender fail prematurely due to overheating as a result of running from a modified sine wave inverter. I’m not sure I would take a chance on a frig with a compressor motor. At times we have no way of knowing what the electronics of a particular device is or what kind of load or motor is inside the device.

In general switching power supplies have no problem with a modified sine wave or square wave. Most all our electronic devices such as computers, TV, and the like are based off of switching power supply technology these days so if that is what you will be running from the inverter you should be fine. However, if you will be running a microwave oven or any AC motor device it may not work because you have no way of knowing how the signal is conditioned before leading to the motor or inductive load of that particular piece of equipment. By not using a sine wave inverter there is a chance something will be damaged. While running devices pay attention to how hot they get. For example, on power tools the motor is exposed enough to feel if it is getting hot. If it is getting hot, don’t use it on the modified sine wave inverter. The reason the inductive load fails is because the insulating material in the coil of the inductor gets so hot it melts. Then shorts result. Some motors and transformers can run hot no problem, but this heat is another source of inefficient use of your battery bank and solar modules.

Hope that helps.
Hi everyone. I'm so looking forward to the solar workshop, meeting everyone, and helping with Paul's empire.

My family and I have been living off grid for 15 years. I have developed some electronics through that time to make off-grid life easier and get better use and work done from the power produced from photovoltaic and micro-hydro systems.

Permies has a great solar forum. Check it out. Please let me know if you have any questions before the workshop.

Hope to see you there.

P.S. You too can get PUMPED UP with a Fresnel lens.
4 years ago
Yes, replicating turns something small into something big. My point was a positive perspective on the concept. Erica’s point was the negative result of the same concept. The fact is, we humans have been mucking around for a long time on this earth. Is it wilderness after we have been in it?

What is wilderness anyway? What Bill didn’t know about the wilderness is that it was likely altered by human activity. We now know, from research and books like 1491 by Charles Mann and Tending the Wild by Kat Anderson, that what Europeans perceived as wilderness, when arriving in land that was new to them, was actually a human altered environment.

As far as leaving things alone or not, I am in agreement with folks like Joel Salatin, Wendell Berry, Allan Savory and others. We need more people on the land. We need more stewards of the land. Leaving the land alone is not necessarily a solution. Of course we should start with the land that is obviously damaged by us. There is an abundance of it.

The problem has not been that we are on the land and use the land. The problem has been the mentality in which we are here. Are we here to conquer, extract, and leave? Or, are we here to practice good husbandry, nurture, and stay?

It is true, as Bill says, when referring to wilderness. There is too little of “it” left, whatever “it” is. We think we know it when we see it. It just may not be.
I like the way this chapter started out “…, I often find I have the only decently dirty fingernails”. I feel the same way. Sometimes when I am at the office in a meeting, I notice I forgot to clean my fingernails from working on my place. I then tuck my hands under the table and look around to see that other people’s hands are fine and soft, sometimes with nails too long to be used for any kind of meaningful physical labor. Such is life for now in this corner of the world.

This chapter does not deal much with legal aspects and what can go wrong, but Erica’s comments clarify this. Much of what is contentious about permaculture is in this area. Aside from roads, we mostly are interested in using earthworks to control flow of water and to contain water. It was good to be reminded of other uses such as shelter, noise and wind breaks. My grandmother said the warmest house she ever lived in was sod. Some of the earth shelter structures of the past such as the native American round houses and sod houses of pioneers are fascinating and could have some relevance with respect to the newer structures such as wofati and more resent building methods and materials.

A great deal of the trouble with earthworks have to do with the scale. “Small is Beautiful” as Schumacher would say. For example, in California where I live, much benefit could be achieved by many small ponds (earthworks) high in the water shed where water flow volume is low as we continue to lose snowpack due to a warming environment. However, in the past, the mode of operation was to build a few large dams to meet water needs which resulted in huge environmental cost and fish species loss. Also, harnessing the flow of large volumes of water leads eventually to major disasters. If one does have the benefit of a sizable river or large volume of water flowing (seasonal or otherwise) through their land, it is wise to divert a small portion by way of earthworks in different places rather than try to harness the total flow in one place by way of earthworks.

Thinking small and replicating what works is the way to go. Distributed small diverse is resilient. Mollison states “Small earthworks are so immediately effective…” (top of p. 228).
Okay, I admit, I skimmed this chapter. I have referenced this chapter in the past to get information about soil rehabilitation. I planted some of the things that were mentions such as daikon radish, comfrey, and various legumes. Had some success, but much failure as well with having to deal with the number of critters in this area (i.e. birds, wood rats, rabbits, deer). Yes, I know, I need to start harvesting them as well.

Most everything I do now I cover with some form of protection, however this means I can’t deal with large spaces. I seem to have good results with broadcasting seeds where some native plants are already established. The established foliage seems to hide enough of the seeds and the young spouts to help them into maturity.

Fact is, there are so many other good books and sources of information about soils that I prefer to reference them first. Example, I just heard a great interview of Elaine Ingham in which she claims that there is no earth structure within the United States that is deficient in minerals. All we need to do is get the right microbial activity going in the soil and the minerals will then become soluble in a form of which the plants can absorb them. For me that sounds pretty cool. Mineral additives can get to be very expensive. Check it out. Frank Aragona has got his podcast going again. Good stuff!
While Mollison does not mention the uses of a Trompe anywhere in this book, it may be worthwhile to bring attention to the Trompe for this chapter. Mollison did talk about the Trompe in some video lectures. This device amazed me as it is a very elegant way to produce compressed air with no moving parts other than the movement of water. There are few that live in areas with sufficient moving water and drop in elevation to use a Trompe, still it is something for a permaculture designer to be aware of.
The discussion of windbreaks and shelterbelts in this chapter was particularly meaningful to me having grown up in the Midwest. I remember as a child some of the beautiful shelterbelts that were then mature that must have been planted right after the dust bowl years to aid in keeping the soil in place. By the time I was growing up not many farmers or ranchers seemed to think it was very important anymore. From what I could tell, few new shelterbelts were being planted and few are today. Perhaps government programs related to this activity were dropped. Too bad.

While Mollison went on at great length about windbreaks and shelterbelts, there is one aspect of them that I have not seen mentioned in any permaculture literature that I have come across. Mollison does make brief comments about drifting snow, but does not discuss it in depth. However, this relates to the use of shelterbelts in snowy prairie like, windy areas such as the Midwestern area of the United States.

In the wind, blowing snow will as easily go up hill as it will down hill. Shelterbelts have a capacity to catch a tremendous amount of snow out on the prairie. Following the principle of slowing the flow of moisture across the land, a good permacultural practice would be to position the shelterbelts high on the land such that the collected snow when melting in the spring would soak into the soil as it moves down hill. Catchment dams and ponds could also be positioned higher up on the topography as a result of the shelterbelts being higher.

It would be great to see some permaculture folks in the Midwest experiment with this concept. This would be of most advantage in the rolling hill type geographies on the prairie. If anyone has heard of example of this please share. I suspect this has likely not been put into practice because neither Mollison nor many other permaculture practitioners to date have been working in snowy prairie like locations.
I was glad to hear of the “catch up week” as I too was finding it hard to get through this chapter. I have always understood the concept of edge. Pattern seems more mysterious. I much appreciated the videos that others posted. Thanks. For me, it helped clarify a few things. It seems that patterns are the result of some rule, law or process that takes place and therefore (in my opinion) the pattern may not be as important as the rule followed or the process developed.

For example, if one does swales on contour, a pattern emerges that can be quite beautiful but the designer did not necessarily think about the pattern but thought more about slowing water across the land and proceeded with a design based on this.

Another example is the spiral galaxy or vortex ring. If Mollison explained the underling law behind why a galaxy is shaped like a spiral, I missed it, given my lack of being able to focus on this chapter. However, a vortex and galaxy shape results from the law of conservation of angular momentum.

Here is another related video that hopefully will result in some insight into this chapter.
(if this link puts you into the Mechanical Universe main menu go down the page to lesson 19. Angular Momentum. Other lessons may apply as well such as lesson 16. Harmonic Motion)

I can think of at least one very purposeful good use of a vortex in permaculture - the vortex filter commonly used in aquaponic and pond systems.

While reading this chapter I was thinking of all the other stuff I needed to get done and I did learn some new things. However, I could not help but think that if I took the time and calm my mind there might be some very profound insights I could uncover. Perhaps I will revisit this someday in a more settled state.