What’s Happening


Thanks for your comment. I hope to post more but I am not sure when that will be. I have more insect photos waiting in the wings.

Lately I have been experimenting with efficient twig-fueled cooking stoves. I am very pleased with the results. Anyone interested can find what I did by doing a search on “rocket stoves”.

I have also been experimenting with regenerative radios, trying to find the one that uses the least power and fewest number of active devices (read: “transistors”) yet performs with sensitivity, selectivity, stability and covering a wide tuning range that includes short wave as well as AM broadcast. Someday I may publish my results. So far, it seems to me that three transistors are the minimum needed for a practical radio. I have been able to get one to run a long time on the power left in a battery that, for other purposes, is essentially dead.

From my organic garden I have been eating strawberries. Also: peppermint, curly dock, dandelion leaves, wild grape twigs and leaves, lambsquarters, winter savory, sorrel, garlic chives, common chives, wild lettuce and green onions. I typically collect a bowl full of an assortment of the above, wash it, chop it up fine, mix it with a bit of mayo, and eat it with biscuits, along with a tea from roasted dandelion roots.

I also love poke. It is very tender and has a delicate flavor. I do not include it in the above mix because it needs to be boiled twice before eating (or so I have heard; being one never to doubt authority, I always boil my poke twice).

I have a potato plant I transplanted when it volunteered in an inconvenient spot. Sweet potato slips are sprouting in the kitchen window. I also have carrots raising their heads in the garden. Carrots are all I deliberately started from seed this year (so far). They are slow growers, but I am faithfully keeping them watered and weeded.

I recently dumped a good bit of compost on the raised bed garden. The compost came from worm bins kept in the basement and an outside compost pile.

I still collect rainwater and filter it with a slow sand filter. I use the filtered water to hydrate the basement worm bins. I use unfiltered water to hydrate the outside bins and keep the seedlings from wilting.

I am still eating last years’ sour kraut from a jar in the refrigerator. It has been several months since I checked what is growing in the crocks kept in the basement. Reluctance to look comes from a little fear about what I might find.

I have not baked sour-dough bread for a while but I know how easy it is to create another starter from whole wheat flower should I ever need to.

I recently learned that the secret to soft biscuits is adding sugar to the dough.

I have not used the solar oven yet this year, mostly due to a sparsity of sunny days. It looks like summer is about to put an end to our rainy season soon, though.

It has been a good spring for wild mushrooms, but I have not found any that I could identify well enough to eat.

I am still convinced we need to take a serious look at true socialism. Obamanomics, the hysteria of media lick-spittles aside, is not socialism.

I might take up oil painting again soon. I did that a bit a very long time ago but have some new ideas about mixing paint that I want to try.

As you see, I keep very busy. Blogging frequently sits on the back burner. Thanks, again, for your interest.


First Multi-Mirror Solar Oven Simulations

by Curlydock
Nov 27, 2007


Results published in previous posts increased confidence in my solar oven simulation program. Those tests were confined to the single-mirror configuration. By keeping things simple, results were intuitively judged. Now it gets more interesting as we encounter kaleidoscopic multi-mirror configurations with results that may challenge intuition but that are, nevertheless, we hope, still accurate.

The number of variables that define the problem make closed form expression prohibitive, at least for me. Thus, my use of simulation.


The oven seems simple enough in that it is composed of two sets of hinged mirrors and a sphere called a “bounding sphere” that stands for the oven cavity. The oven cavity is the part of the oven that gets hot enough to cook food. It is constructed like a small green house, but we need not concern ourself with those details.

The bounding sphere is all we need to know about the oven cavity. The center of the sphere gives the CAVITY LOCATION in EXTENSION and ELEVATION from the “origin”, the lowest point on the vertical R1-R2 hinge. The cavity location is always in the bisecting plane of the oven’s bilateral symmetry.

The radius of that sphere gives the SIZE OF THE CAVITY. Now, to make results easier to compare across simulations, I have normalized all units of distance to the diameter of the oven cavity. So, instead of inches, feet, meters, etc, all lengths are in units of cavity diameters.

I have named the four mirrors of concern: R1, R2, R3 and R4. Hinged on a vertical axis are R1 and R2. R3 and R4 are hinged horizontally. So, we have the two angles: R1–R2 ANGLE and R3–R4 ANGLE.

We will also be concerned with where the sun is in respect to our oven, so we have: SOLAR ALTITUDE ANGLE or elevation; zero degrees on horizon and 90.0 degrees at zenith, and SOLAR AZIMUTH ANGLE. In all runs I presently contemplate, the azimuth will not change, confining the sun to the plane that bisects the symmetry of the oven.

We also have to be concerned with R1 WIDTH and R1 HEIGHT. R2 is always identical to R1 in width and height.

Since R3 and R4 are hinged horizontally, it is confusing to speak of their width and height, so I define the dimension R4 RATIO, the length of the horizontal hinge, as a portion of the opening of R1-R2.

R3 is always parallel to, or in the plane of, the horizon. R1-R2 sits on R3 like an open book with the bottom two corners on the axis of the R3-R4 hinge. Because of this configuration, the reflective part of R3 will always be a triangle with size and shape determined by the width of R1, R2 and the R1-R2 angle. The other mirrors are always square or rectangular.

R4 EXTENSION is how far R4 extends from the horizontal hinge.

Also an input variable is the QUANTITY OF REFLECTIVE PLANES. I can consider four possibilities: R3 only; R1 and R2; R1, R2 and R3; as well as all four mirrors.

I think that about covers the input variables. So far I have not concerned myself with losses based on reflective angles, surface imperfections, convection, conduction, mass, re-radiation, transmission distances, imperfect insulation, etc.


What we get for output is the amount of idealized SOLAR FLUX GAIN on the oven cavity over what the cavity would have gotten directly from the sun without any concentration. This is not a temperature; it is a ratio. The minimum value will always be 1.0 unless the cavity is in shadow or blocked from direct rays, where the value could fall to zero. The maximum value depends on all the inputs.

Because of the large quantity of possible combinations of input variables, I must find a way to lock some of them down so they can be temporarily ignored. That will simplify the problem and help us make sense of where we are in our journey to the “perfect” design. I do not know if there can ever be a proof that a particular design is the best possible one. There might always be a combination of inputs hitherto unconsidered that will yield a greater flux gain than what we thought was the best. If there is such a proof, a bigger brain than my own will need to find it.

That is why I am willing to share my program listing with anyone who is interested and who agrees to keep my program or any derived from it in the public domain, not for profit.

I am also willing to do runs for others who would like to see particular results of inputs meaningful to them. Perhaps they have built an oven or two and want to see what the simulation says about comparative performance. If you are interested, just leave your request in the comments section and I may publish my response or run results in a future post.

Next, some multi-mirror runs:

For the time being I will keep R1-R2 angle at 60.0 degrees. The decision is arbitrarily based on the fact that an oven I built uses that angle. In the long run, there may be a better angle.

Also, for now I keep the width of R1 at 4.0 cavity diameters. I do that because prior runs with R3-only seemed to result in 4.0 as the optimum size for the side of R3, given the R1-R2 angle = 60.0 degrees. The length of a side of R3 is the same as the width of R1 (and R2). Lastly, to start, I make the height of R1 equal to its width.


Chart “nov1029a” shows the effect of cavity extension on flux gain where only R1 and R2 are in play. For these inputs, the best value seems to be 1.4, but it depends on the angle of the sun. By this chart, for sun angles higher than about 40.0 degrees we might want to make the cavity extension less than 1.4 cavity diameters.

Next, keeping cavity extension at 1.4 and everything else the same, we do four runs, one for each of four different heights of R1-R2. That results in chart “nov1030” where
red (1) = 4.0
green (2) = 6.0
blue (3) = 8.0
black (4) = 10.0
cavity diameters.


We see gains increasing at higher sun angles as the height of R1-R2 increases. The gain increment decreases so returns are diminishing. At this point I will make the compromise of R1-R2 height = 6.0 and keep that for the next set of runs.

I cannot resist the temptation to add more mirrors at this point. Chart “nov1032” run (1) is a repeat of “nov1030” run (2), for reference. It looks different because the vertical axis of the chart is re-calibrated to cover higher gains.


Note the gain still peaks at about 6.0. That gain makes sense when you consider that two mirrors at a 60.0 degree angle would allow the sun to see six images of the cavity. Run (1) is only with R1 and R2 in play.

For run (2) I merely add reflector R3 to the play, and the results show a significant increase in gain. If we consider that R3 would double 6 images to 12, the gain seen of about 9.0 makes sense, considering some of the images will be partially obscured.

Now we take a lesson from a prior post when we were testing with only R3 and learned that it is best to elevate the cavity somewhat over R3. We do just that in run (3) and see that the gain is even closer to 12.0. Supposedly, the reason is that the images are less obscured when the cavity is elevated.

In run (4) I put R4 in play and made R4 the same size and shape of R1 and R2. It is a handy size if the oven is collapsible and you stack the reflectors for storage. The solar flux gain reached 14.0. One might worry that the simulation is malfunctioning because the flux gain is below 1.0 for very low angles of the sun. More thought reveals that at these low solar angles the cavity and lower part of the oven are in the shadow of R4, so one’s confidence in the program rebounds.

Is this the best design? I doubt it. Only more testing can tell, I guess. At least, it is a benchmark for measuring more attempts.

In a future post I can make the input variables conform to the oven I have actually constructed and see what the simulation says. I will be able to compare a real oven with this benchmark and tell what changes might make it better or worse without getting my hands dirty (not meaning to disparage getting one’s hands dirty).

Last Single-Mirror Solar Oven Simulation Test

by Curlydock
Nov 24, 2007

In my previous couple of posts I showed some of the results of tests of a program I wrote to simulate what I call a “kaleidoscopic” type solar oven. In earlier posts I detail the actual oven I use to bake bread. I wanted to see how to build a better oven of this type, so I wrote the simulation for ray-tracing various reflector sizes, shapes, quantities and configurations.

This post will cover what I hope is the last of the one-reflector tests. I wish to begin tests of two-mirror simulations in the next post.


Graph “nov1026a” shows the results of five runs with a single equilateral triangular reflector in the plane of the horizon. That reflector I frequently refer to as “R3”. Five sweeps of the sun from zero degrees (horizon) to 90 degrees (zenith) are shown, one sweep for each size of R3. The sides are all equal and are measured in cavity diameters. The smallest R3 is 2.0 and the largest is 8.0 cavity diameters on a side. The cavity bounding sphere is represented by the ball that is aways in the corner farthest from the sun when the sun is on the horizon.

Observe that the gain never exceeds 2.0 and never falls below 1.0. This is consistent with my expectations of what happens with only one mirror and increases my confidence in the simulator.

Rule 1026a

Also observe that the increment of improvement in gain decreases as R3 gets larger. Large mirrors increase the gain when the sun is at lower angles but the reflector has to get perhaps impractically large to produce these gains. At solar angles above about 20.0 degrees, it hardly seems worth having a floor reflector larger than 4.0 cavity diameters on a side. This is more than my prejudice up until now, which was that 3.0 cavity diameters on a side was the practical limit. The actual oven I made has only 3.0. So, the next time I build one of these ovens I will probably go with 4.0. It depends on what else we learn when more reflectors are in play.

“Rule 1026a” is, then: the triangular reflector always parallel with the plane of the horizon, that is the one the cavity is above, should be sized to about 4.0 cavity diameters on a side, physical practicality permitting, and probably not less than 3.0.

Now I combine this rule with rule 1010a from the previous post, which said the cavity should be elevated. That results in chart “1027a”:


For this run I kept the mirror sized to 8.0 cavity diameters on a side and elevated the bottom of the cavity from just touching R3 to where the bottom of the cavity is 0.5 cavity diameters over R3. Otherwise the run and chart calibration are the same.

Again, the gain never exceeds 2.0 and never falls below 1.0, which is good.

Also note that elevating the cavity improves gain when the sun is at higher angles. This is consistent with what we learned in the prior post and was to be expected. The simulation still seems to work. For this configuration, with the cavity elevated, the range of sun angles with the maximum gain of 2.0 is much larger.

In a prior post I expressed some doubt about whether the simulation was following the ray trace through an arbitrary number of reflections or breaking off too soon. I later discovered that was indeed a problem. But it only affected simulations of more than one mirror, none of which I had published yet. I fixed the bug and am now confident that I am ready to do multi-mirror tests. In the next post we will see some results using two reflectors. Those reflectors are the ones I have named “R1” and “R2” in prior posts. They are linked by a vertical hinge and open like a book over the plane of R3. R3 will be put aside while we consider only R1 and R2 and will return probably much later when three-mirror tests begin.

More Elementary Tests of a Solar Oven Simulation

by Curlydock

Nov 16, 2007

In the prior post I introduced a test of the simulation using only one plane of the “kaleidoscopic” type solar oven. So far, we have seen the bounding sphere of the oven cavity positioned over one triangular concentrator. That concentrator corresponds to the R3 reflector mentioned in other posts describing an actual oven that I have been using. The R3 reflector is in the plane that appears to be parallel with the earth’s surface and the cavity assembly rests on R3. In later posts we will be considering the effect of the other reflectors: R1, R2 and R4. This post is confined to more implications of the R3 reflector.

Diagrams “nov1007” and “nov1008” illustrate the oven cavity bounding sphere positioned at two different levels over the triangular reflector.

nov1007a.jpg nov1008

The red dots represent the absorption of a light ray on the surface of the bounding sphere. The blue dots represent rays reflected from the surface of the mirror that do not intercept the cavity. The shadow of the cavity can be seen on the mirror. The other dark spot on the mirror is that portion of the mirror where rays are reflected that do intercept the cavity.

This Test

The present question is how the height above the mirror affects the amount of solar flux gain the cavity will receive as the sun sweeps over an altitude angle from zero degrees on the horizon to 90 degrees at the zenith.


Diagram “nov1010” shows the result of four simulated solar sweeps, one for each of four different heights of the oven cavity above mirror R3.

On Units

Unless otherwise noted in these posts, the units of distance measurement will be cavity diameters. I think that is more interesting and informative than using yards or meters, etc. So, no matter what the radius of the cavity is in feet, centimeters, inches or any other unit, it is always 0.5 in cavity diameters. When the cavity rests on the mirror the center of the cavity will be 0.5 cavity diameters from the surface. The lowest point on the cavity, in that case, will be zero cavity diameters from the mirror.

The triangular mirror, R3, seen in the above illustrations and used in this particular post, is equilateral and 3.0 cavity diameters on a side. The cavity CENTER heights used to generate the data for the chart “nov1010” are 0.5 (red), 1.5 (green), 2.5 (blue) and 3.5 (black) cavity diameters. There is one color coded sun altitude sweep for each cavity placement.

The Solar Sweeps

These “altitude sweeps” are not the natural movements of the sun, so don’t be confused. The sweeps begin at the lowest point on the horizon and end at the highest point in the sky, or the zenith, at 90 degrees. The point on the horizon, zero degrees, where the sweep begins, is always in a vertical plane that bisects an angle of the triangular reflector.

The reason for this type of sweep is to see how the more complicated mirror arrangements respond to different solar angles, all of which keep the sun in the plane that bisects the symmetry of the concentrator arrangement. The purpose was to have a standardized sweep with which to compare different arrangements under any solar angle that might happen no matter what the season, location on the earth, or time of day, given that one could always adjust the oven so the sun is in that bisecting plane. Such an adjustment would not change the fact that R3 is in the plane of the horizon; it would merely rotate R3 in that plane. The tests to see how the simulated oven responds to a natural solar transit will probably be some of the last tests.

Rule 1010a

Now back to chart “nov1010”.

Note that when cavity height is lowest, 0.5, which corresponds to touching the mirror, the gain never reaches the greater levels it does when the cavity is elevated from the mirror. This is the reason for placing the inverted glass bowl underneath the oven cavity assembly, as seen in my prior posts detailing an actual solar oven. The lower bowl elevates the whole assembly a bit. I was never quite sure just how much it should be elevated but now it seems my simulations may help to determine this.

So, Rule 1010a for building kaleidoscopic solar ovens is: elevate the cavity over the mirror that is parallel to the plane of the horizon instead of letting it rest on it.

Next, we see just how much elevation is best. The above graphs suggest that the best cavity elevation will depend on the solar altitude. The angle of the sun is constantly changing; so, if we can figure out a way to easily adjust the cavity elevation about every twenty minutes, that would optimize flux gain at all times. Such a rig might be more complicated than the extra flux gain is worth, however.

Diagram “rule1010a”, seen below, might be used in the design and operation of a one-triangular reflector solar oven with an equilateral shaped mirror three cavity diameters on a side. It probably would not work for baking because the flux gain would never exceed 2.0. It might be useful for proofing bread dough or keeping a plate warm. It might also apply to ovens with more reflectors, but we have to wait to see what more tests produce to be sure.


This diagram allows us to determine the best cavity height above the reflecting plane for any given altitude angle of the sun. I gathered the data for the diagram from repeated runs with the simulation program. That these curves seem to make sense to me reinforces my confidence in the accuracy of the program so far (no guarantee, of course).

The runs show rather broad peaks. That suggests that a particular cavity elevation would work well for a wide range of solar angles without need to re-adjust the height. For that reason, the diagram “rule1010a” shows a region instead of a line. The acceptable region is in yellow-green between two limiting lines. The limiting lines represent the points where the solar flux gain has dropped to 0.9 times the peak value seen in the sweep. The graph seems to indicate that for solar angles below about 25 degrees there is no need to elevate the cavity at all. The flux gain might be very low, but elevating the cavity will not help.

How to Apply Rule 1010a

Here is an example of the use of diagram “rule1010a”:

Suppose the sun is at 70.0 degrees above the horizon. Find 70.0 degrees on the horizontal axis of the chart. Follow the vertical from 70 degrees up until it just reaches the green region (the first limiting line). Follow the horizontal from that point to read the cavity height. That yields about 0.70 cavity diameters.

Continue on the 70.0 degree vertical until the green region just ends (on the other limiting line). Following the horizontal from that point yields about 2.9 cavity diameters.

Therefore, the maximum gain will be when the BOTTOM (not the center) of the cavity is between 0.70 and 2.9 cavity diameters from the surface of mirror R3.

If the cavity is 12.0 inches in diameter then 0.70 cavity diameters represents 0.70 X 12.0 = 8.4 inches. Likewise, 2.9 cavity diameters X 12.0 inches per cavity diameter = 34.8 inches. At these points the gain will be about 9/10 what it would be at the peak.

To find the height corresponding to the actual peak, you can use the average. In this case, the average cavity height is (0.70 + 2.9) / 2.0 = 1.8 cavity diameters, and 1.8 X 12.0 = 21.6 inches.

In the morning and evening hours the sun is not so high and the cavity will not need so much elevation. Even if the cavity elevation is not optimum, the losses will not make the oven useless, it will probably just take a little longer to cook something. Also, when we start adding the other reflectors R1, R2 and R4, the gain will be considerably beyond 2.0, so some small maladjustments will be even less of a problem.

Initial Test of Solar Oven Simulation

by Curlydock
Nov 15, 2007

The diagram labeled “nov1002” displays a rudimentary test of my solar oven simulator. From this I hope to begin to see if the program is behaving correctly.


The oven cavity is seen as a ball above a triangular mirror.

A cross section of the solar flux is seen in yellow above right.

Any ray absorbed by the cavity is drawn in red. This could be either a ray directly from the sun or a ray reflected from the triangular mirror.

A ray reflected from the mirror that is not absorbed by the cavity is drawn as a short light blue vector. Any time a vector is drawn, the direction is indicated by the small ball at the end, which could be interpreted as an arrow head.

To reduce clutter in the diagram, the rays reflected and lost to space are drawn very short. They appear as a sort of light blue haze over the triangular reflector. You can see the “shadow” of the cavity on the mirror. Rays that neither hit the cavity nor the reflector are not drawn at all.

The program calculated the solar flux gain in this case to be 1.974359. This means that the cavity received almost twice as much solar radiation as it would have without any reflector at all. This is precisely what I would expect. The flux received by the cavity directly is doubled by the presence and proper placement of the mirror. The cavity would “see” two suns: one directly and the other reflected. Reciprocally, the sun would “see” two cavities, also one direct and one reflected. The analytical solar flux gain is two.

The theoretical flux gain without any reflector would be exactly one. That would be the minimum ever seen. Any properly directed reflections will increase that. The flux gain is calculated by dividing the quantity of rays absorbed with mirror concentrators in place by the quantity that would be absorbed directly from the sun when there are no mirrors. The simulation counts the rays and calculates the gain.
To see the importance of mirror orientation, we next consider what happens when the sun is at different angles, everything else remaining the same.


Diagram nov1003 shows how the flux gain drops to nearly unity when the sun is at a very low angle. The reason is that the triangular mirror is not of infinite extent. If it could be made large enough, we could get our gain back up to two. Thus the physical trade-off for the solar concentrator with the sun at small angles to the surface.


Diagram nov1004 shows the other extreme. Here, the sun is nearly at the zenith, but again the gain has dropped to nearly unity. This time the reason is that the cavity obscures the sun’s reflection. Where the cavity would “see” the sun it now only sees itself. The sun can only see the direct image of the cavity. The reflected image of the cavity is mostly hidden from the sun by the cavity itself.

These preliminary results continue to indicate that the simulation is correct.

Next, we can have the simulation sweep the solar altitude angle from zero degrees (on the horizon) to 90 degrees (at the zenith) and graph the flux gain against the solar angle. The triangular reflector is in the horizontal plane and therefore parallel with the horizon.


Diagram nov1005 shows the results of just such a sweep. We see the flux gain peaks at 2.0 broadly when the sun is around a 50.0 degree angle and falls to unity when the angle of the sun is either much more or much less than that.

In conclusion, the program I wrote to simulate some types of solar ovens seems to be working so far. I do still have reservations. There is more testing to do.

In future posts I hope to show the results of adding more reflecting flux concentrators. The flux gain will go up much more quickly with each added reflective plane as each added reflector exponentially increases the number of images (as in a kaleidoscope) while the increase in the number of mirrors is only linear. But limitations due to image obscuration, as we have already seen here, will subtract from the advantage of adding more reflectors, producing diminishing returns.

Some factors that affect real physics of multiple reflections I am going to ignore. I feel they would add a great deal of complexity without proportionally increasing the accuracy, at least for my purposes.

One of these factors is that every time a light beam is reflected, there is some loss. The amount of loss depends upon the angle of incidence. In my program, so far, this type of loss is not deliberately encoded. I assume no such losses.

Another factor is that no real reflector is perfect. Imperfect reflective surfaces will throw the light ray off at a non-ideal angle. Nor do I try to account for this effect.

Another factor is that I have some doubt about whether my program, as it is currently written, will ray-trace beyond about 4 or 5 reflections. I am not sure if this is true or why it happens if it does occur. I am keeping a look out for the effect but am not letting this doubt stop me from reaching for some results.

There may be other factors that have escaped my wildest dreams; who knows?

This work I put in the public domain for purposes of information and I do not claim it is perfect and suitable for just any application. If you are interested in seeing the listing, I am willing to share it. I can post it later.

Kaleidoscopic Solar Oven Temperature vs Time

by Curlydock
Nov. 13, 2007

In my previous post, on September 27, 2007, I went into detail describing the “Kaleidoscopic” type of solar oven that I have been using to bake bread.

image 93

Now I post the time versus temperature for an actual bread baking episode. The episode occurred in Jefferson County, Kentucky, USA, on a day in October, 2007. There had been a recent rain and the cloudless sky was unusually clear and free of haze. Starting at 10:55 AM EST, the bread baked to completion in about an hour. The maximum temperature recorded, between the black lid and top glass bowl, was 320 F (160 C). Just as I removed the bread, I saw the temperature was 325 F and probably still climbing. The ambient temperature was 64 F at the beginning and 70 F at the end.

The results are tabulated and graphed in the next image:



10:55 AM ___ 64 F ___ not recorded ___ start baking

11:05 AM ___ 64 F ___ 240 F (116 C)

11:15 AM ___ 64 F ___ 275 F

11:20 AM ___ 66 F ___ 280 F (138 C)

11:30 AM ___ 68 F ___ 290 F

11:34 AM ___ 68 F ___ 300 F (140 C)

11:44 AM ___ 69 F ___ 308 F

11:56 AM ___ 70 F ___ 320 F (160 C) ___ condensation seen

12:06 AM ___ 70 F ___ 320 F ___ good odor, end baking

The optimum design for this type of oven is a fascinating problem. I wonder if 60 degrees is the best angle for the vertical axis and what the best sizes and proportions are for the reflecting panels. I am pretty sure it would be pointless to have the width of the vertically hinged panels be either more or less than three times the diameter of the oven cavity, for example. But I would like to have some way to test these personal prejudices.

To that end, I have given in to the temptation to do a detailed theoretical analysis. My way of doing this is to write a computer program that uses something like “ray tracing” to simulate the oven, allowing me to more easily see how different configurations affect the solar flux concentration. That program is pretty much finished and I hope to post some of the results in the near future.

Kaleidoscopic Solar Oven / Cooker

by Curlydock

One of my earliest installments dealt with the theory of the best angle to use with the reflecting planes of the solar concentrators of the Box-type solar oven. Since then, I have come to prefer what I call a “Kaleidoscopic” type solar oven.

I feel I have many reasons for this preference, but the most important is simplicity or ease of construction. Roughly speaking, the 3-D description of a Box-type oven takes about 20 vertexes and 32 lines. For the Kaleidoscopic type, it is 8 vertexes and 11 lines. So the Box type is about three times more complicated than the Kaleidoscopic type.

image 92

Image 92 shows the Kaleidoscopic oven I used to bake many loaves of genuine sourdough bread over this past summer.

image 91

Image 91 shows a not-fully-risen loaf before baking. I consider it fully risen when the top of the loaf reaches the top of the bowl. The bread bakes in the oven-proof glass bowl which sits in the oven cavity. The cavity is detailed later.

image 82

image 83

Images 82 and 83 show a finished loaf.

image 89

Image 89 looks into the front of my Kaleidoscopic oven. Most of the essential parts are seen. Missing is the glass bowl that would sit inverted over the top of the black lid. The oven cavity is shown in position and ready to receive the bowl of dough.

The reflective concentrators are in four planes. Two that I will call R1 and R2 form a vertically hinged unit that opens like a book and sits at a 60 degree angle. The hinge for R1 and R2 is made with strapping tape. The oven cavity just touches R1 and R2 and sits on R3, which is a separate unit the shape of a triangle.

The R3 angles are all 60 degrees and the length of each side is three times the diameter of the oven cavity. R1 and R2 are as wide as the sides of R3 and considerably taller than that.

R4 is also a separate piece and extends from the open edge of R3 as if it were hinged horizontally to R3. It could be permanently hinged but I feel there is no need for it. A pole pivots from the outer edge of R4 and fixes on the ground. It is used to set the angle of R4 so that the oven cavity is the brightest you can make it. If the wind is not blowing, gravity and the angle adjustment pole will keep R4 in place.

If there is wind, then I fasten all the sail-away reflective panels to the table with shoestrings. The cardboard from which R1, R2 and R4 are made is reinforced along bottom edges with narrow wood strips and package sealing tape. The shoestrings go through holes punched in the cardboard, around the wood strips, and through the mesh of the table top.

The weight of the oven cavity keeps R3 in place.

When the wind is very strong I use sandbags to hold down the table legs.

Here is a diagram comparing the Box and Kaleidoscopic type solar cooker / ovens and labeling of the concentrator panels I have been describing:

oven types diagram

The Box type has only one side glazed. That is the side where the solar flux enters the box. The other five sides have to be well insulated to keep the heat in. The maximum reachable temperature will depend a lot on the effectiveness of this insulation and the quality of box construction.

The Kaleidoscopic type does away with this particular need altogether by making all sides glazed. So, solar flux would enter all around the oven cavity, in theory. In actuality, this will not be perfect. The reasons have to do with the positioning of the oven cavity among the reflecting walls. Some positions are better than others.

Here is a detailed semi-exploded diagram of the oven cavity:

oven cavity diagram

The oven cavity works like a green house to trap the heat from the focused solar flux. The ideal would be a series of concentric spheres. The outermost sphere is transparent glazing that passes light. The next sphere is an insulating jacket to keep the heat, for which a vacuum would be best but air is easier. The next inner sphere is flat black metal which absorbs light and converts it to heat. This heat ideally accumulates in the central sphere where the food cooks in its container.

The ideal is approximated here by the use of oven proof glass bowls and a stainless steel metal mixing bowl.

The outermost sphere consists of two glass bowls: (1) is inverted on top and (4) completes the bottom half.

The insulating air jacket is made by suspending the metal radiation absorber bowl (6) on a ring (7) cut from a double layer of heavy corrugated cardboard. The ring rests on the lip of outer glass bowl (4). The lip of the metal bowl (6) makes a snug fit in the ring (7) so that the metal bowl will not fall through. The metal absorber does not touch the outer bowls anywhere. It only touches the cardboard ring. The ring and air jacket are poor conductors of heat. They confine most of the heat to the cooking area.

The metal radiation absorber bowl is a stainless steel mixing bowl painted flat black on the outside with the kind of paint that withstands heat, or the paint you would use on a charcoal grill. Let the paint dry, cure under heat and air out for several days before using it for cooking. You probably would not like paint flavored bread.

I was lucky in finding a black metal cooking pot lid (2) that just fits over the lip of (6) and rests on ring (7). There are cake or pie tins that might also work if painted black on the outside.

Bowl (3) holds the food or bread dough. It does not have to be transparent. I have been using oven proof glass but recently found a ceramic bowl that should also work. Another metal pot identical to (6) would fit snugly and maximize cooking space and thermal conduction to the food, but I have not tried that yet. In fact, I suppose you could do without (3) altogether by putting the food in the radiation absorber bowl (6). But, since (6) is not easy to get on and off ring (7) and the cardboard of (7) should not be washed or get wet, I decided to use another bowl to hold the food.

On my wish list is some kind of thin wire handle to make food bowl (3) easier to get in and out of metal bowl (6). The handle would need to quickly and easily connect and disconnect from the edge of the food bowl and not compromise the thermal seals around the edges.

The whole cavity needs to be somewhat elevated so I put it on a transparent pedestal made by inverting the smallest glass bowl (5) near a corner of the bottom reflector, R3.

Most of the glass bowls I found and purchased as a nested set. I think perhaps the largest, (4), was not part of that set and had to be separately purchased, but I am not sure.

Why Kaleidoscope

To study the effect of the focal positioning and the angle of R1 and R2, etc., I decided to research the geometrical and mathematical aspects of multiple reflections in mirrors. From that, I realized the kinship between kaleidoscopes and this type of solar cooker. The next pictures should make the relationship obvious.

Fascinating as it was, I thought it might take too long, so I did an empirical study with a scale model instead of the exacting thought experiments. I gathered some pieces salvaged from a broken mirror (never throw anything away), tape, and construction paper. Also, I borrowed a large bead from a trusting and tolerant friend.

Image 74 is an overview of the apparatus:

image 74

The bead stands for the oven cavity or focus.

The mirrors that hinge on a vertical axis stand for reflecting planes or solar concentrators R1 and R2. R3, seen here on the bottom, will be moved in and out. R4 is not shown here but will be seen later.

image 57

image 60

image 61

image 62

Images 57, 60, 61 and 62 show how the number of reflections of the bead increase as the angle between R1 and R2 decreases. This inverse relationship says to me that the narrower this angle the better as far as solar flux concentration.

Surely, the more images of the bead (oven cavity) the sun “sees” then the more solar flux will concentrate on the bead.

But there are several trade-offs.

As you can see, the ring of bead reflections gets gradually larger as the angle decreases. To compensate for this, the sizes or areas of R1 and R2 need to progressively increase. At some point R1 and R2 are too large and cumbersome.

image 63

Image 63 shows how adding one more mirror, representing R3, doubles the number of bead images. Note how one of the images is lost because it is shadowed or hidden by the actual bead.

image 73

Image 73 shows how images are partially obscured when the bead is not elevated:

This is the reason that the oven chamber is elevated a bit by bowl (6).

image 72

Image 72 shows how the bead image count can be at least doubled yet again by adding the mirror that stands for R4. But, as the count and complexity of reflections increase, more and more images are obscured. There seems to be a threshold of diminishing returns.

image 66

Image 66 shows the concentrators at work. I used flash, which, I belatedly realized, is probably not good for a digital camera in a setup like this. Fortunately, perhaps most of the energy focused and dissipated on the bead instead of getting back into the camera lens.

If bead were bread, it baked.

How I Use the Kaleidoscopic Solar Oven

I use an angle of 60 degrees between R1 and R2. There may be a better angle. I have not tried others yet. I adjust the table orientation and the angle of R4 about once every 15 or 20 minutes. This needs to be done more often when the sun is high in the sky.

I frequently measure a temperature of 280 F between the top glaze bowl (1) and the lid (2), depending on the time of day. Morning hours, with the sun at a lower angle, seem to make the oven hotter than do the noon hours, probably because of the reflection obscuring effect already mentioned. Elevating the oven cavity even more when the sun is high in the sky might make the oven even hotter, but I have not needed to try that yet.

Either time of day works fine for baking my bread. The recipe for one loaf of sourdough calls for 45 minutes at 350 F in my conventional oven. I can bake 3/4 of that recipe in the Kaleidoscope solar oven in around 90 minutes. The crust browns nicely, especially on the top.

You might be tempted to let the finished bread cool just a little bit in the oven. But don’t do that. And don’t be fooled. The oven gets very hot. Be careful not to burn yourself.

While the oven is cooking, the moisture escapes as steam. As soon as the oven starts to cool, that moisture condenses on the lids and runs down to collect on the corrugated cardboard ring. The cardboard ring may dissolve if it gets wet. But, it can withstand the highest temperatures of the oven just fine. The high temperature helps keep the ring dry. As soon as I finish baking, I dump the bread on a rack to cool.

After a bit of practice, you can tell when the bread is finished baking by how it smells around the solar oven. Also, you will begin to see condensation on the inner side of glass bowl (1) when the bread is ready.

Outside of baking sourdough and cornbread, I have not yet cooked other things in this particular oven / cooker. I wonder if the condensation will be more of a problem if, for example, I make soup. I don’t know yet.

A Note on Construction Technique

Many instruct builders of these types of ovens to glue the aluminum foil to the cardboard with diluted white glue. I no longer do this.

I believe it is sufficient to bend the foil around the edges of the corrugated cardboard and fasten it in the reflective plane about every square foot using brass plated paper fasteners. Insert the fasteners through small holes prepared with a knife blade. These fasteners can be found where you get office supplies. They look like tacks with points that can be spread apart. This is much easier than working with glue. It is easy to repair.

But the main reason I do it this way is that the foil is easily removed from the cardboard when time comes to recycle them both. My red worms can eat the cardboard but the foil might not be good for them and would not be wanted in the vermicompost.

I do use white glue or carpenter’s glue to bond cardboard to cardboard where a panel needs more strength or a flap needs to be made rigid.

image 93

Best Solar Oven Reflector Angle installment II by curlydock

In the first installment, I mentioned that I built a device for measuring the best angle for a solar box oven reflector. This is a description of that device and how it is used.

fig 7
The device has three physically coupled sub-units: a miniature solar box “oven” with one reflector, a protractor for measuring the reflector angle and a pinhole “camera” for aligning the device properly with the solar rays. The substrate is made of foam-filled poster board held together with plastic package sealing tape. The reflector is aluminum foil glued shiny-side out. Black gaffers tape and black permanent marker were used to control undesired light reflections.

fig 1
Box “Oven” sub-unit

The miniature box “oven” is not really an oven, but it is similarly constructed. It has a cube volume of 5 cm on each edge. The reflector is a square of 13 cm on each edge. Instead of measuring internal temperature, as in an oven, we will use a photocell driving an electrical meter to measure light intensity. Temperature measurements take too long to stabilize. The photocell I used was scavanged from a defective solar powered calculator. I coverd it with a piece of paper to diffuse and reduce the amount of light. An analog meter was used because a digital meter makes it too difficult to search for a peak response. One has to wait too long for the digits to stabilize.

fig 3
Protractor sub-unit

A clear plastic protractor is taped to the device. It is used to measure the angle of the reflector after the peak light response is found.

fig 2
Pinhole “camera” sub-unit

The pinhole “camera” is not really a camera. But it does focus an image of the sun on a screen. When the device is properly aligned so that the solar rays enter the box aperture at a 90 degree angle, then the sun’s image will be seen in the center of a cross-hair that is drawn on the projection screen. For this to work, much care needs to be used in the construction of the device so that all the edges are straight, corners are square and lengths are accurate. Use a sharp knife to cut the poster board. The lens of the camera is a pinhole in a piece of aluminum foil. Most of the foil is covered with flat black fabric tape to keep light reflected from that surface from getting in the oven and causing an error in the reading.

fig 6
How to Use the Device

1. Align the whole unit with the sun so that the image of the sun, a tiny white dot, is in the center of the target cross-hair.

2. Adjust the angle of the reflector for a peak response in light intensity.

3. Read the angle of the reflector from the protractor.

4. Repeat the first three steps several times and compute the average of the readings. The average will be more accurate than any single reading.


I took five readings. They were: 118, 121, 120, 122 and 121 degrees. The average is 120.4 degrees. Converting that to “reflector angle”, as defined in the first installment, gives: 180.0 – 120.4 = 59.6 degrees.


The result for the best angle for a solar box oven reflector being 59.6 degrees is only 0.4 of a degree away from 60.0 degrees, the angle used in many actual designs. The spread between the largest and smallest measurement was: 122 -118 = 4, or +/- 2 degrees. In the first installment, I wondered if the reflector angle (90 + 45) / 2 = 67.5 degrees might be a better angle than 60.0 degrees. But 67.5 falls significantly outside the result of 60.0 +/- 2.0 degrees. So, for whatever reason, 60.0 degrees appears to be the best angle.

The reason for this might be found in a more complicated analysis taking into account such things as the fact that much of the light entering the box oven comes from directions other than directly from the sun. Any reflector in this type of design will not only concentrate light coming from the sun but also block the entry of refllected and diffused light from other parts of the sky and terrain.

In a subsequent experiment I covered the reflector with a sleeve made of flat black paper. I could slide the sleeve up and down to test the effect of reflector length on the outcome. The results were still consistant with 60.0 degrees as long as the reflector was at least as long as the box aperture was wide. When the reflector was a fraction of the box width, these were the results:

fraction ; best angle

0.333 ; 55.0

0.625 ; 56.0

0.833 ; 58.0

1.000 ; 60.0

>1.000 ; 60.0

My intention is to use the best angle I found for each of the four reflectors in a pyramidal consentrator design. I have almost completed that oven and will test it soon.

Published in: on October 29, 2006 at 12:55 pm  Comments (48)  

Best Solar Oven Reflector Angle Installment I by curlydock

I wondered what the best angle for the flat solar concentrator or reflector of a box-type solar oven is. So, I conducted a little thought experiment.

figure 8

Fig 8 is a diagram containing three solar ovens, each with a reflector at a different angle. I will define the “reflector angle” as the smallest angle the reflector makes with the plane of the oven window while the reflector surface is exposed to the sun.

Oven A has a reflector angle of 90 degrees. At this angle, the reflector surface does not engage the sun, so it cannot increase the sunlight falling on the box-oven window. It is clear that an angle greater than 90 degrees will cause the reflector to shade the window, obviously not what we want.

Oven C has a reflector angle of 45 degrees. None of the sunlight reaches the oven window because all of the light is reflected parallel to the surface of the window. Also, as the angle becomes smaller than 45 degrees the sunlight is increasingly reflected back toward the sun itself instead of through the window. We don’t want that either.

So, the best angle must be between 45 and 90 degrees. Oven B has a reflector angle of about 60 degrees. I believe most designs use this angle. This angle is between 45 and 90, but is it really the best? Consider the simple average of 45 and 90. That is (45 + 90) / 2 = 67.5 degrees. The difference between 60 and 67.5 of 7.5 seems considerable to me. Might it be better to use 67.5 degrees as the relfector angle of a solar box oven?

This simple thought experiment ignores many complicating issues. It assumes the surface of the window is kept perpendicular to the solar rays. That is not absolutely necessary and may not be true in actual use. But, for the sake of analyis I let that be a constant. Most light is transmitted through a window when the incident rays are at 90 degrees. As the angle becomes more acute, less light is transmitted because it is lost by being reflected away.

That more light is reflected as the incident angle gets smaller has implications for the reflector as well as the window. It suggests that reflectors work better at smaller incident angles. However, as the incident angle diminishes, the reflector must get progressively longer to intercept the same amount of light.

Another assumption in this experiment is that it is conducted deep in outer space. That is not obvious, is it? In fact, only in outer space would all the solar rays arrive at the oven at the same angle. On the surface of our planet, there is a good chance a solar ray will arrive at our oven at almost any other angle than directly from the sun itself. There are many reasons for this. One is the atmosphere which refracts the sunlight. There are particles and clouds that diffuse and reflect the light. Many reflections can occur from the planets surface, some of which are very strong if the surface happens to be a body of water. (This suggests to me we should always paint the outside of a box oven flat black and then wrap the oven with something like bubble wrap.)

Also, real mirrors and windows have imperfections. In a more sophisticated simulation one might take those imperfections into account.

The fascinating complexity if this issue prompted me to build a small device I could use to empirically measure the best reflector angle for a solar box oven. Using the device resulted in a best angle of 59.6 degrees, close enough to 60 degrees! In another installment I hope to describe how that device was constructed and how it works.

Published in: on October 24, 2006 at 12:06 am  Comments (88)  

Personal/Planet Sustainable Survival Practice

If the world changes for the better, it will be the result of decisions made by individuals on a personal level. If we wait for salvation from government or corporate sources, it may never arrive. Many of us have been waiting too long. Now it may be already too late to save the planet. It comes down to you and me.

There are many things each individual can do. Sustainable technologies exist that can be used on a personal and local level. Many of these methods seem old and simple, as indeed they are. Others are not so primitive but are very healthy, like the democratic medium (so far) of the Internet.

Technology is not evil in and of itself. The problem is that science and technology have been hijacked by greed. But there are other ways to use technology.

Here is a list of things we can practice. It is incomplete. I deliberately leave out things like carpooling, walking, using public transportation, etc., because they have been flogged to death elsewhere. Other things, like the root cause of the planet’s problems, even the greehouse effect, being due to overpopulation, and the need to therefore limit our numbers, should be obvious to anybody who wakes up and starts to genuinely seek answers. Overpopulation is not a looming problem. It has been with us too long already. Instead, I list viable methods many people may have never given serious thought to.

Some are methods old to the planet, almost extinct, but new to the modern slaves living in a brainwashed stupor. Try what you can from the list. Add to the list if you can. Research, experiment and let the world know what you learn. I am trying to do the same.

I hope to go in greater detail in later installments.

Intensive gardening

Grow an intensive raised-bed vegetable garden organically. I was elated to learn there is even a way to reap from your garden in the cold of winter. This winter will mark my first winter gardening.

Instead of chemical fertilizers, pesticides and herbicides that have to be manufactured, purchased and transported, use organic fertilizer from your compost or worm bin. Instead of tap water, use water from your rain-barrel in your garden. It will be better for the plants because it is not chlorinated. You will save on your waterbill. The planet will benefit because energy was not expended processing and getting that water to you.

Insecticides kill not only bad insects but good insects. Good insects do pollination, eat bad insects, help in composting, and condition soil naturally for permeation by air and water.

Herbicides kill plants other than the ones targeted, Even weeds are useful to the organic gardener. Many weeds are edible and nutritious. Weeds are a green manure. Roots of some weeds bring valuable nutrients from deep in the soil where other plants could not reach. Composting these weeds releases nutrients on the surface where the plants we cultivate can use them again.

Agrochemicals leave residues harmful to people and planet. The use of these oil-based products destroys life in the soil. After the abuse stops, soil takes years to recover.

The agribusiness soil is merely a dead thing used to hold the plant upright, and it is barely good for that. The ability of the soil to hold water is degraded, making plants more susceptible to drought. Soil erodes and these chemicals run off as pollutants when it rains. This runoff is toxic to life in rivers and the ocean. The need for irrigation is greater, but irrigating with ground water is also harmful, causing salt-accumulation toxic to even the cultivated plants.

Let’s about-face, people. This is literally a dead end.


Maintain a compost pile. You can use local inputs costing nothing: lawn clippings, fallen leaves, cardboard, paper, kitchen scraps, weeds (carefully), manure from herbivores, etc. Do not use dog or cat manure because it may harbor disease that infects humans. I live in the city, so I also do not put dead animals in the pile.

There are several ways to compost, broadly known as hot and cold methods. A hot pile happens when the “greens” and “browns” (nitrogen and carbon sources, respectively) are mixed in proper proportion, the pile is not too small, has the right amount of moisture and is turned inside-out and upside-down frequently. Hot piles reaching about 140 F will sterilize many seeds and diseases.

Cold piles are piles that are missing some of the needed ingredients or methods that make a pile hot, but cold piles work too. A cold pile may not finish composting until more than a year has passed. A proper hot pile may be finished in only weeks, depending on what is in it.

A partially finsihed pile may be sifted through a metal screen or mesh. What ges through the screen may be useable but may have more weed seeds that are viable if the pile has not cooked hot enough. Even a cold pile can eliminate seeds, though. I have observed that conditions in a cold pile are ideal for seeds to sprout. But, once they sprout, the seedling will die if it is too deep to get light. And, if it sprouts on the surface, one pile turning will put the seedlings deep in the pile where they quickly become green manure!

As with worm bins, the compost bin will not stink or attract pests if it is done properly. Bury fresh kitchen scraps deep within the pile so they will not attract rats, dogs, etc. If your pile is in the city, you may also want to keep herbivore manure (from cows and horses) out of the pile, merely to control odor. You can use, instead, what is called “green manure”, which is typically a living plant that is freshly cut: grass clippings, weeds, etc.

Composting with worms

Vermiculture is another good basement project. Use earthworms to compost kitchen waste. Cut-up cardboard and newspaper are fine worm bedding. That makes less waste to burden landfills or be recycled outside your home.

When I tried this, I was not prepared for the incredible reduction in volume of the kitchen scraps after they were worked by the worms. They tranformed into little black dots, worm poop! The scraps and bedding became virtually unrecognizable as anyhthing other than good dirt. I was also amazed that I could detect no odor whatsoever from the liquid that drained from the worm bin, worm pee! It took my bin about a full year to mature to this level. That was a bit longer than I expected but I suspecct I did not start with as many worms as I thought I purchased. It’s hard to tell, and I was not about to actually count them. That would have stressed them after already being stressed by shipping.

I use this leachate and vermicompost to fertilze the organic vegetable garden and make potting medium for seed germination.

Composting with worms is not hard to do. Properly done, there is no sigificant odor and no problem with flies.

Water collecting

Use rain-barrels to collect water. This lessens energy use and load on municipal sewer and water supply systems.

Mosquitoes cannot use the barrel to multiply if it is properly constructed and screened.

If the barrels cannot be kept in the shade, the chance of becoming sour or stangant is reduced by periodically dipping out and pouring back some of the water. This gets more oxygen in the water, which is especially important on hot days. A simple trick to maintain freshness is to use an aquarium air-stone and pump in each problem barrel. The amount of electricity used is negligible. You might even find an air pump that will run off an electric solar cell. The brighter the sun, the faster will the pump oxygenate the water; no need for batteries or charging circuitry.

Do not drink rain water unless it has been sterilized by boiling. Remember that it came from your roof where it has probably carried down dissolved bird and squirrel droppings, dead insects, etc.

However, it is better than tap-water for watering your garden because it has no chlorine. You can wash the car (if you must have one), water the lawn, etc., saving money on your water bill. It is soft water because it has not run through the limestone of earth. Once boiled, it is good for washing where you need soft water.

If you don’t like the suspended particles that made it through the screen, a sand filter can be used to remove the particles.

Water filters

You can use sand filters to clean your rain water. There are several types of sand filter.

A coarse filter will quickly remove visible floating things.

The other, the slow-sand filter, is very special. It is a self-healing living organic filter that is capable of making water very clean indeed. It filters water at microsopic level, even removing diseases that affect the roots of plants. The fact that it is a self-contained organic niche with living things in symbiosis puts it, to my mind, in the same class as other personal survival technologies, like the worm comosting bin, the starter used in sourdough bread and the fermentation that makes wine and cheese.

As in the organic garden itself, the substrate becomes populated with beneficial organisms, leaving no room for harmful organisms to grow, even feeding off of them. It is interesting how this theme keeps recurring in the organic world.

The slow-sand filter works by allowing water to very slowly seep through a bed of sand. The filter is not viable until a community of living things inhabit the filter from the surface to several inches below the surface of the sand. They live on whatever they mangage to filter out of the water.

I use an air-lift water pump, driven by an aquarium air pump, to oxygenate and constantly circulate water in the filter, even when the filter is not being used. Also, some s-bend plumbing I use to keep the surface of the head water at least an inch above the surface of the sand at all times. This helps to keep the filter in good health. The life under the surface of the sand will die if it is allowed to dry even a little. But, even if that happens, after restoring the water level and allowing a few days or weeks of circulation, the filter will self-heal!

My first filter ran for over a year. I have never had a filter clog, but it is supposed to be possible. To clean the filter when it is clogged, stir up the surface to suspend the detritus in the head water. The sand quickly falls back. Dip off and discard the muddy looking stuff. Then wait several days as the surface heals.

The slow-sand filters I made produced pristine looking water with no coloration or visible suspended particles. I would not drink it, however, without boiling it. It may be perfectly safe, but I will not take a chance until I have more practice in this method. Someday, I plan to have the before-filter and after-filter water samples tested in a lab. But even if that sample tested clean there is a chance that a later sample would not be clean, especially if the surface of the sand was disturbed in some way after the sample was sent to the lab. The living surface of the filter may easily be damaged if, for example, plumbing going through the surface moves a little bit. So, everything should be rigidly constructed. I made my fliters using plastic storage containers like clean new 30-gallon trash bins and another out of a plastic container meant for holding long rolls of wrapping paper. A better idea, probably, would be to make the filter out of concrete or ferrocement.


Plants need physical support, correct temperatures, air movement (oxygen and carbon dioxide), water and nutrient salts to survive. They don’t really need soil if they are in a protective environment or enclosure.

You might grow a year-round garden in your basement. There are hydroponic techniques that do away with the need for high-tech. Many plants can be grown in plastic gallon milk jugs without air pumps and without water pumps.

If needed, these jugs can be insulated agains temperature fluctuations by covering them with papiermache (more planet friendly than Styrofoam). It surprised me just how little flour it takes to make the glue used in papiermahe. Paper and plastic jugs are given a new life instead of being discarded.

The trick of doing hydroponics without the need of redundant water pumps and power supplies is to gradually reduce the water / nutrient level as the seedling grows. When the level is 5 or 6 inches below the top of the root system, keep it there. If it rises above that level again the plant will drown! The upper roots become what is known as the “O” roots, or oxygen roots. The roots still in solution are the “WN” roots, or water / nutrient roots.

I stopped my basement hydroponics garden because I became concerned that the HID (High Intensity Discharge) lamp, was using more energy or electricity than could be justified given the amount of food that was produced. But, you can also do hydroponics outdoors during the summer in a screened area. Perhaps you could do it on a roof where it would supplement instead of compete with the organic garden growing in your yard.

If you are growing large plants, like cucumbers or tomatoes, you will need a larger container than the milk jugs. The larger the water / nutrient container, the less often you will need to monitor and adjust the temperature, pH, nutrient and water levels. If you don’t want to use plastic, because it is a product of crude oil, you might build the nutrient tanks using ferrocement.

If you don’t want to use chemical nutrient salts, you can try organic compost tea.

Edible weeds

Carefully educate yourself on what “weeds” you can eat.

Beware: some are poisonous or should only be used after special preparation. Don’t collect plants that were growing next to a busy road where they may have been contaminated by automotive emissions or dog or cat excrement and urine. Be aware that many places have been used as toxic waste dumps. Try to learn the history of the area where you collect. Where has the water been that feeds the area?

What I do is let selected “weeds” grow where they volunteer in my garden. I cultivate them by weeding the weeds, you might say. You may or may not want to make green manure out of them before they go to seed. If a tasty weed goes to seed, the seedlings might make a nice salad when they sprout! Be careful, it is sometimes difficult to properly identify seedlings. Some of the weeds I have tried are extremely delicious. Some are said to be more nutritious than fresh produce from grocery stores. If it should ever come down to it, knowing what “weeds” you can eat may save you from having to go dumpster diving.

Solar cooking

Use solar ovens for baking and cooking.

I was amazed at how easy it is to do this. My very first attempts: baking cornbread and hard-boiling eggs, were entirely successful. It took about 3 hours for each, but I might not have needed to let the eggs take that long. More practice will tell.

These ovens or cookers can be made simply from cardboard boxes, newspaper, aluminum foil, white or wood glue or glue made fom flour, turky oven baking bags, a dark cooking pot that fits inside a covered glass casserole with a lid, and perhaps some of the flat black paint used on cooking grills. There are several types you can construct.

Wood cook stoves

When the sun is behind clouds, you can cook on an efficient wood-burning cook stove.

“Efficient” is the key word here. Through complete combustion, an efficient stove converts all the fuel to heat, water, carbon dioxide and little else. You can par-boil your poke salet with mere twigs for fuel. There will be little smoke or pollution. This is important to me because my lungs are especially sensitive to dirty air.

The stove is made efficient by skill in operation and attention to certain design elements. It needs a flue length and cross section that is able to supply enough air for complete combustion. Without a flue, you could use an electric fan to force the air through, but why use a high-tech fix when a low-tech one works fine?

Also, complete combustion requires high temperatures. The combustion chamber needs to be insulated so heat stays in the chamber. You can use wood ashes for insulation, but it takes perhaps too long to accumulate the ashes. You can also use perlite (heat-expanded siliceious rock) or vermiculite for insulation. My experimental stove was made of perlite held together with refractory cement.

Don’t worry about contributing to greenhouse gases by burning twigs. The carbon in the twigs would go back to the atmosphere as soon as the twigs decayed. The real culprit in greenhouse gases is the burning of fossil fuels like coal and oil. The carbon in fossil fuels stays right where it is until some selfish ignorant monkey burns it.

Preserving food

Preserve food with solar dehydrators.

I have yet to try this, but it is on my plate. I believe driers can be designed in a way to work even in fairly humid environmnents.

This preservation technique requires no high-tech refrigeration. Like solar cookers, driers can be built from cardboard boxes. Neither does it require the purchase of jars and lids, as canning does. Dried food takes less storage space. It weighs less, very good if you’re traveling. I hear that the flavor of some foods improves when the food is dried.

Sourdough bread baking

Bake your own bread.

Particulardy, learn sourdough baking. Using sourdough eliminates a commercial input: yeast. Instead, wild yeasts from the air or the grain itself or even from the human body (the origin is uncertain) in symbiosis (that word again) with bacteria leaven the bread. The sourdough starter takes only flour, water and waiting. Visual and olfactory clues let the baker know when the starter is ready for making bread. The starter is alive, like the slow-sand filter, and must be kept fed and comfortable. It needs more flour and water on a daily basis at room temperature, or a weekly basis if kept in a refrigerator.


You won’t need light but you do need relatively cool and stable temperatures to grow sprouts, another good candidate for basement gardening.

Sprouts are cheap when you grow them yourself. It is said they are more nutritious and more easily digested than cooked seeds and beans. Since they don’t need to be cooked, energy is saved.

You don’t need big sprouting jars, unless you are going into production. If you have several small glass jelly jars, the sort of thing that might end up in a landfill or be re-cycled, you can have an assortment of sprouts at different stages of growth. That will give you just the amount of very fresh sprouts you want each day without the need to refrigerate anything.
Rinse the sprouts seversl times a day in cool water to help them breath and keep them from becoming rancid. Except for the smallest seeds (use a screen or strainer for those), hold your clean hand over the mouth, turn the jar upside down, and drain through your fingers until the water just stops dripping. Return the jar to an upright position and cover loosely with an over-sized non-metalic lid. Be sure flies and gnats cannot get to the sprouts.

If the sprouts smell bad, which might happen on hot summer days, feed them to your worms and start over after sterilizing the lid and jar in boiling water.

Enough mung beans to just cover the bottom of the jar will eventually grow to fill the whole jar!


These personal/planet survival methods are interwoven in many complex and beautiful symbioses.

I used the slow-sand filtered water initially to supply my basement hydroponics experiment. I use the water to hydrate my worm bin when it needs it. I mix flour with the water to make or feed the sourdough starter. Baking would surely sterilize any pathogen that the slow-sand filter may have missed.

I eat vegetables from the organic garden. Scraps feed the worms. Worms produce fertilize for the garden. The circle is complete. There are many other cycles. That is the way nature evolved to work. We should study and nourish these cycles instead of breaking them.

If you want to learn more about any particular practice, search the Internet. Some of the information may be ambiguous or just wrong; time for an experiment! Share what you learn! I plan to continue doing the same. I may not update my blog as often as some do because I will be spending time and energy gaining the experience to share when I finally return to the keyboard. However, I do hope to go into greater detail on some of these methods in future installments.

We can discover an alternative to the way that the world is now organized by man. We get to know the new-old survival technologies. They will help us survive on both the personal and planetary scale. Many of these methods are in reach of even those who are financially burdened. Knowing what weeds you can eat will keep you out of the dumpster. An efficient wood cook stove will not pollute the air or contribute to greenhouse gases and will cost only twigs to operate. With or without the cooperation of government and corporations, practice can renew and sustain our hope of survival.

Practice is so full of surprises that you are never bored. You discover a non-toxic fatigue, but no burnout and no spiritual or emotional damage. You discover something hard to explain but feels ancient and deeply right. The Green Man is waiting in the composting leaves for the next cycle.

You begin to understand how we are misled about our proper role on this planet because the resulting confusion is so profitable for a few. You discern the true meaning of freedom and how liberty is being lost today. Practice will heal your broken lifeline to the living planet. Practice insures your life means something more than that of being a corporate or government slave.

Down with noise, slavery, speed, greed and competition. Up with communication, consideration and cooperation. We can do it.