HoSa Solar SK-01 User manual

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SOLAR PARABOLIC COOKER
SK-01
USER MANUAL
HoSa Solar Ltd * Kocherinovo 2640 * 57B N.Vaptzarov St.
tel. [phone] * е-mail: [e-mail] * www.hosasolar.bg

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Attention! Directions of this manual must be observed! The proposed solar
parabolic cooker is intended exclusively for personal use. Suitable only for
cooking (by heating, boiling, steaming, frying, baking). Any other usage of the
solar cooker is inconsistent with its purpose and can lead to damages or injuries.
Producer and importer are not liable for damages and injuries caused by an
inappropriate usage of the solar cooker.
Basic parameters of the SK-01 model:
- Diameter of the reflector: 140 cm
- Depth of the reflector: 47 cm
- Focal length: 26 cm
- Opening (aperture): 1.54 m2
- Average power: 1000 W, for solar radiation 700 W / m2
- Maximum power: 1500 W, for solar radiation 1,000 W / m2
I. Description.
SK –01
The solar parabolic cooker (SPC) utilizes the fundamental property of the
parabola - the sun rays that fall parallel to the axis of the reflector, after
reflection pass through the focus of the reflector. Thus, SPC concentrates power
in a small space area (focus).
Metal vessel (pot, pan) placed in the focus area absorbs radiant energy

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concentrated there, heats up to a high temperature and thus the process of
cooking food is being accomplished.
The reflector is made out of 24 aluminum sheets, each two opposite forming a
parabola. The surface layer of the aluminum sheets is mirror polished, therefore
having a high mirror reflectivity with respect to the solar spectrum.
The reflector is supported by a steel stand, which provides its rotation in
horizontal and vertical plane to follow the daily movement of the sun.
Relevant to the functioning of the SPC is only direct solar radiation - measured
in W/m2. That is radiation reaching the solar cooker as a beam of parallel rays
directly from the sun. The device operates only in clear weather and light
clouding. Thick clouds suspend it.
The maximum efficiency of SK-01 and every other SPC is achieved by the
simultaneous fulfillment of the following four conditions:
- clear and dry weather;
- the sun is around its climax - which occurs at noon;
- the reflector is so aimed that its axis is parallel to the sun rays;
- the reflecting surface is clean.
II. Usage requirements
The conversion of radiant energy into heat energy for the needs of the user is
carried out successfully only by observing certain requirements.
Deployment of the solar parabolic cooker
1. SPC must be placed on a stable and even basis.
2. SPC should be placed in аprotected from the wind site. Owing to the large
area of the reflector, the pressure of the wind on it could be significant. If no
protected area is available, further strengthening is necessary.One way to do
that is at least 3 sandbags, each 20 kg, placed so as to ensure the stand and to
prevent rotation and twisting of the reflector by the wind. Another way is
rivetting to a concrete base.

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It must be remembered that no reinforcement can protect SPC from stormy
winds.
Material of the cooking vessel
Cooking vessels should be metallic. The high thermal conductivity of metals
allows to heat up the entire vessel, although the focused light falls only on part
of it. Plastic pots are not allowed.
All vessel parts should be metallic, including handles. Plastic handles are
unsuitable as concentrated rays may melt them.
In SPC could be used any traditional metal cooking vessels that are being sold
everywhere. It is advisable to be thick-walled with thermo-bottom. Also could
be used thin-walled enameled pots, in which case it must be remembered that
there is a risk of burning and scorching and special attention during cooking
process is needed - stirring the food or shifting the pot from focus.
Color of the cooking vessel
Unlike the conventional cooking apparatuses, in SPC the vessel color influences
the duration of the cooking process.
Vessels are recommendably painted black outside, in order to absorb more
solar energy. The vessel painting inside is not relevant. If black vessels are not
available, standard oven spray blacking could be used for that purpose.
Focusing
Focusing of a SPC means targeting the reflector to the sun in such a way that the
axis of the reflector is parallel to the direct sunlight. When this is fulfilled, the
bright spot of the focus falls within the supporting grid area.
Focusing of SK-01 is performed using a directional pin (DP). DP is mounted

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parallel to the axis of the reflector. Therefore, if DP makes no shadow, it
means that the reflector is properly directed (focused)!
Improperly focused reflector: Properly focused reflector:
the directional pin makes a shadow! the dirpin makes no shadow!
Another visual criterion that the cooker is properly focused is the presence of a
bright spot of concentrated light on the cooking vessel.
In general, focusing the reflector requires rotating in two planes: horizontally
(from left to right) and vertically. In practice, however, for a certain time
interval around noon point, it is enough the rotation to be performed only
in a horizontal plane - from left to right! This due to the fact that during that
period the sun changes only a little its height and therefore the focal spot
remains within the reach of the vessel only by rotating in a single plane. For
example, for the latitude of 42°N (the latitude of Blagoevgrad and Rome) in
summer months, between 11:00 h and 15:00 h, it is sufficient the reflector to be
rotated only horizontally!
Adjusting the position of the reflector is necessary to perform every 20 minutes.
Safety precautions when operating parabolic solar cooker
1. SPC should not be shifted during operation. Only activities related to
refocusing and adjusting are permitted.
2. Within a radius of 3 meters around SK-01 should not be kept flammable or
easy-to-melt materials. The concentrated power of the device in contact with
paper, cardboard, wood, plastic can lead to a rapid ignition and material damage.

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Items of plastic material could be melted. Leaves and fruits of fruit-trees or
garden plants within the scope of the reflector could be burnt and turned black.
3. Wear sun glasses because of the danger of blinding.
4. Wear tight, bright clothes. Loose sleeve clothing not recommended because of
an ignition danger.
5. Don’t seek the focus location with bare hand - risk of burning. Always use a
suitable object made of metal or wood.
6. Pot handles are heated up to high temperatures. Always use mittens,
preferably of cotton. Artificial fibers are easily melted.
7. The solar parabolic cooker should be operated mostly from behind the
reflector.
8. The solar parabolic cooker should not be left unattended during operation.
9. When not in use, cover SPC or turn its back to the sun.
10. In windstorm or hail, SPC must be removed to a protected area. If not
possible, at least dismantle the reflector and place it upturned on the ground.
11. When SPC is housed behind a transparent screen (window, transparent
plastic wall, etc.), do not keep it turned to the sun because of the risk of damage
to the surrounding objects.
Maintenance
1. The reflecting surface must be kept clean - as to extend the life of the unit and
to not reduce its reflective ability. For cleaning use a soft cotton cloth, ordinary
detergent and lukewarm water.
2. Rotating parts of the SPC must be regularly lubricated.
III. Combined usage with a fireless cooker
A fireless cooker (FC) is the perfect addition to the solar parabolic cooker.

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HoSa Solar Ltd. offers fireless cookers of own production (see detailes in
www.hosasolar.bg ). Both photos show the model "Grossi", whose outer
dimensions are 563 x 422 x 330 mm.
The operation principle of the fireless cooker is simple: a pot filled with
preheated liquid food - soup, stew, etc., is inserted into a heat-insulated box, so
achieving two things:
keeping the meal warm for hours;
if the preheating temperature is above 90 °C, the meal is not only retained
hot, but also cooked in its own heat.
Cooking sequence: a pot is filled with food between 50% and 80% of its
volume, then boiled on the solar cooker between 1 and 20 minutes depending on
the dish, then moved to the FC and covered with special insulating pillows.
Finally the lid is closed.
Advantages of the combination “parabolic cooker –fireless cooker”:
- FC gives an answer to the eternal question about solar cooking: what to do
when there is no sun! If the weather is getting poor (clouds, strong wind) -
solar cooker ceases work, but then the pot is transferred to the FC and the
cooking process continues;
- FC unlike SPC: does not need supervising; is used indoors and needs a
small space; burning and scorching is not possible.
- FC increases the cooking capacity of SPC: in good weather the solar cooker
together with the fireless cooker can prepare up to three dishes
simultaneously. For example, the first two dishes could be in pots and placed
in FC; the third dish could be prepared on SPC and could be placed in a pan.