The solar oven is for cooking food in a pot
using the sun as a source of heat, and is designed for ease of use.
The solar oven has to be easy to use, so it should not require
adjustment as the sun moves across the sky. This calls for an
elongated reflector that continually reflects sunlight on the pot for a
span of one hour. This feature calls for a greater reflector
height than other designs, and greater heat retention. The walls
are made thick with anti-convective insulation, and the top is a double
paned glass with vacuum between the panes. The inner wall surface
absorbs visible spectrum and emits infrared, although most light is
incident on the pot. Between this inner wall and the insulation
layer is an air gap with infrared
reflection back to the inner wall. The outer wall surface has
low infrared emissivity. The pot itself should absorb visible
spectrum and have low infrared emissivity.
The insolation time is the time the sun takes to traverse the
reflector, about one hour. A cover constructed the same as
the walls but extra thick in insulation covers the glass top for
retained heat cooking, adding another two hours cooking time. A
built in compass allows for proper oven
alignment with the sun at the start of cooking. The reflector
long dimension is oriented east-west and the oven is tilted toward the
equator with the pot suspended inside. The reflector frame has
braces to ensure that it
withstands wind and rain.
Electric cooking pads are typically 2.5kW. Given the
insulation the retained heat solar cooker can probably get by with
1/5th of this, or 500W. Solar insolation is typically 1kW/m^2, so
the reflector area needs to be 1/2 m^2 over the width of the pot.
Most likely a parabolic shape about one meter long, 1/2 meter wide and
1/2 meter high will suffice.
The reflector as viewed from the sun looks like so:
Initial heatup reflector (i) has extra reflector area to bring the food
in the pot (p) up to cooking temp. As the sun moves from left to
right the reflector area reduces to that supplied by side reflectors
(s) for maintaining the cooking temp.
The pot rests on a flat metal grill supported by a horizontal metal rods
on two sides that form the axis to support the reflector/container
assembly and allow rotation angle for seasonal movement of the
sun. Clamps keep the assembly fixed at the desired angle.
The rods afix to vertical wood struts to support the entire unit above
the ground to allow the reflector/container rotation and for protection
from ground moisture. The reflectors are hinged to allow closing
up for storage and tolerance of high winds. The reflectors are
made from sheet aluminum and are kept polished for high
performance. The two-paned vacuum glass pane is commonly found as
energy-efficiency building windows.
A retained heat oven cooks food by retaining heat in the food for the
cooking interval. The food is placed in a covered pot and heated
conventionally. When the food reaches cooking temperature the pan
is transferred from the heat source to the retained heat oven.
The retained heat oven is made from another pot or container that is
about three inches larger in diameter and about five inches deeper than
the cooking pot. The cooking pot will rest on a one inch layer of
insulating material, e.g. perlite, in the bottom of the
container. The pot with lid should rise up to four inches below
the top edge of the container. With the pot at this level, a
vertical slot is cut in the side of the container for the pot's handle
to protrude through.
Put the layer of insulation in the container bottom. Then wrap
the cooking pot bottom in aluminum foil, shiny side out, to form a foil
liner shaped by the pot. Put the foil liner/pot in the center of
the container on the insulation bed. Cut the foil top edge to be
2.5 inches higher than the container top edge, and fill in the space
around the foil liner with more insulation to the container top
edge. Fold the foil to cover the insulation, tucking it in along
the inner edge of the container, with the top surface of the foil at
the same height as the top edge of the container. The cooking pot
with lid should rest in the foil liner four inches below the top edge
of the container. A bowl shape is made out of foil, this time
using three layers, by placing foil in the container above the pot,
extending to the inner edge and up vertically all around as with the
previous foil liner, but this one extending up a distance equal to the
pot radius plus a couple of inches. Insulation is placed in this
foil bowl up to the top edge of the container. The foil is then
folded down to enclose the insulation with the extra foil collected in
the center into a handle for placing the top in and out of the
A solar distiller produces purified water from almost any source.
A 36 sq ft distiller can produce from 2 to 5 gallons of purified water
per day. The distiller is a box about 2" deep, the front face
glass, the bottom metal with charcoal black pigment adhered with
suitable binder. The box is sealed and insulated to keep a high
temperature inside and on the bottom. The glass is
single pane as it need to be the cooler surface inside. The box
is tilted toward the sun, and the feed pipe runs across the top edge
inside bottom dribbling the water pumped from the input tank so that it
flows down the bottom and returns to the input tank. To evenly
spread the water, the feed pipe hole spacing is closer at the end
farthest from the input hose. The input water flowing down the
distiller bottom evaporates and
condenses on the inside glass surface where the output water flows down
to a collection pan across the bottom and to an output tank. The
front face glass has to be supported to avoid breakage from
rain/hail/snow. The box has to be supported to prevent wind
damage. The pump has the have a sufficient input filter, cleaned
regularly. The inside bottom surface has to be cleaned regularly
to remove the minerals and debris from interfering with the thermal and
flow characteristics. The inside glass surface, trough and pipes
have to be cleaned regularly with disinfecting alcohol.
A solar water purifier kills microorganisms in water supplies. The purifier consists of two glass plates separated
by a stainless steel ribbon near the perimeter of the plates, with water inlet at bottom and outlet
at top. The rear plate outside surface is painted with high temperature flat black paint. The painted
surface is then covered with aluminum foil. Behind that is a 1/2 inch air gap and anti-convective insulation.
In front of the front plate is a two-pane low-e cold-climate glass window and the gap is sealed with low-conductance seal
between it and the front plate to prevent air entrance there. The gap keeps the high temperature of the
front plate from affecting the low-e window system. The purifier is mounted for maximum sun exposure.
The water is pumped through at an appropriate rate to heat the water to 160F for thirty minutes.
for the desired time before it exits the purifier.
We purchased a 5.1 cu.ft. chest freezer and converted it to a refrigerator by taking the temperature adjust panel out
and adjusting the coarse temperature screw under the thermostat attached to the panel. A chest conserves energy
in comparison to a conventional refrigerator because the cold air tends to stay in the chest when the lid is open.
We use two cardboard boxes, stacked inside, with lids which further help contain cold air. Condensation has to be wiped
off the walls and bottom, and the boxes have to be dried, on a weekly basis. It is important to unplug the power cord
when opening the panels on the chest freezer, and when the coarse temperature screw is adjusted, it is important to coat
the screw head with light strength thread locker, making contact with the thermostat housing to secure the screw.
For your bathroom, mount a wood ring the shape of the top surface of the toilet bowl to give it an extra 3/4"
depth so the standard 7 quart plastic potty buckets straddle the toilet bowl without hitting bottom. The toilet water valve
can be turned off so the bowl remains mostly empty except when guests need to use the toilet in the regular way.
One potty bucket for pee and one for poo. The top kept on the bucket keeps in the smell. Empty and rinse once a day. Mix pee
with 4 parts water and pour it on the ground under plants that need nitrogen, that is anything you want to grow vegetatively,
as opposed to flowering/fruiting. The poo bucket should get a bottom layer of leaves or paper to keep the inside plastic surfaces
clean. More can be piled on top to eliminate sight/smell. If pee has to mix with poo, just use extra leaves/paper.
The poo is emptied into the middle of a one year compost pile, under the top layer. The bottom of the pile is a thick 6" to 12"
layer of leaves (or other dead plant matter). You can put vegetable scraps in this pile and even meat, oily food, even dead animals.
It needs adequate leaves mixed in, and moisture. Leaves piled on top keep the smell and moisture in. Cover it with a tarp
in extra dry/wet seasons, and leave it exposed in moderate dry/wet seasons. Start a second pile when the first is 3 feet
high, and let it sit for one year. Then it should look/smell like rich garden soil - excellent fertilizer! See the
Humanure Instruction Manual
Note that the one year compost pile is anaerobic
while a compost pile that contains only carbohydrate plant materials is
and finishes much faster.
We have a regular gabled house with a gabled front porch and a large concrete patio. The rear of the house has one continuous gutter.
We plug one downspout and let the other drain onto the patio. We have ground gutters at the edges of the patio catching the water
draining off the patio. From those the water flows in a short ground gutter to the underground catchment tank. The advantage
of the underground tank is the tank and the ground gutters do not present practical/aesthetic obstacles and the disadvantages are
the need to dig a hole and the need for a pump. The front of the house has separate roof gutters because the porch gable faces front.
A ground gutter connects the two and then runs to the front catchment tank. A debris filter and simple overflow spout is attached where
the feed gutter enters the tank. See Comparing Rainwater Storage Options
A manual laundry setup eliminates dependence on energy-consuming and costly conventional laundry equipment. It is especially valuable when the laundry setup must be kept outdoors in a humid climate where the electronics of conventional laundry equipment is vulnerable to humidity.
Our manual laundry setup consists of a pair of 17 gallon Behrens hot-dipped galvanized wash tubs, a manual-crank wringer, a frame to hold the washtubs and wringer, and a Behrens 12 inch washboard. The wash tubs are roughly 24" diameter, and 12" high. The frame is made from pine 2x4s (1.5" x 3.5") with the following members:
- 2x 51" horizontal beams (holding two wash tubs & mid legs in between)
- 2x 18" end cross beams (attaching horizontal beams and end legs)
- 2x 15" mid cross beams (attaching horizontal beams and mid legs)
- 1x 12" top cross beam (spanning mid legs and holding wringer assembly)
- 4x 16" end legs
- 2x 36" mid legs
- 1x 15" x 5" x 0.6" wringer board
These are screwed together with 2.5" galvanized wood screws. Four bolts are fixed to the wringer board with tee nuts and extend 2" below, through holes in the top cross beam, and fastened with wingnuts, for each washing. Between washings, the wringer is dismounted and stored with the wash tubs and washboard under roof, while the frame sits outside permanently.
We ended up with a near-black asphalt shingle roof on our house in a very hot climate here in Central Florida and felt like we needed to change the roof color to help reduce the house interior temperature. The roof temperature regularly reaches over 130F because it can easily burn one's hand. We chose latex elastomeric roof paint and applied it with a 3/8" thick roller. We wanted to avoid bridging paint between shingles to allow for moisture drainage, but it was only practical to avoid bridging above/below shingles (2-3 shingle gap), not side-by-side shingles (1 shingle gap). We left an unpainted 1/4" space between these above-below shingles, which probably helps improve the aesthetic.
By touch, we could tell the difference in roof temperature between black and white shingles as we progressed. We estimated the white shingle temperature at 90F and the black shingle temperature at over 130F, so a conservative estimate of 30F difference. Remaining to know is how long the paint will last on the roof. The paint manufacturer claims a 10 year lifespan but that is on a flat roof, not a gabled asphalt shingle roof. We estimate the shingles have another 15 years lifespan, although we expect when painted white its lifespan will increase to 20 years, if the paint can hold out.
Excluding Little Creatures
Excluding little creatures, including rodents, insects, and molds, from the interior of a home requires patience and more.
To exclude rodents from the attic space we seal all gaps/holes larger than 1/4" everywhere from the top of the roof to the ground, using roofing tar, mortar, caulk and screen in appropriate places.
To exclude insects from inside the home, we seal all gaps/holes down to as small as practical, usually with caulk or spackle. This includes gaps around plumbing pipes, any holes in walls hidden inside cabinets, and behind fixtures including electrical outlets, along floor/wall seams, and even gaps between and among cabinets that can serve as hiding places. We carefully seal all windows and doors, keeping the threshold scrapers in working condition. We have storm windows and doors which we believe help in exclusion.
We remove individual stray ants we see inside. We suspect this helps stop them blazing trails for the ant army to follow into the home.
We deal with mold by keeping windows closed during humid periods and open during dry periods, with the help of indoor/outdoor humidistats. We lower 60% indoor humidity to 50%, and lower if possible. We open the blinds during the day to allow maximum UV to reach the indoor surfaces for mold mitigation. We capture as much direct sun as possible to warm the home in the cold season and we angle the blinds to reflect most of it back out in the hot season. We close the blinds at night when the lights are on to avoid attracting insects and we try to open them after we turn out the lights to help cool the house in the hot season.
Oil & Wax Wood Finishes
We use oil & wax finishes for unfinished wood items such as furniture, bowls and utensils, with excellent results. We use walnut oil, either food grade or cosmetic grade because it is a drying oil, or at least semi-drying, which minimizes substances sticking to it, and maximizes its stability. Oil brings out the color of the wood by increasing contrast between lighter and darker grains while adding moisture and stain resistance, and a matte texture making scratches, dents, and finish touch-ups less noticeable. We usually add three coats of oil, allowing it to cure at least two days between coats. We use caranuba wax because it's more sustainable and less exploitive than other available waxes. Wax provides a shiny transparent finish and extra moisture and stain resistance. We apply wax, like shoe polish, to table tops after curing a single application of oil.
2005, 2006, 2007
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