Les Mer

Archive for the ‘Diverse engelsk’ Category

Hot water is not taken for granted everywhere in the world. It demands a lot of energy and in some countries this often means burning coal or wood. Another alternative is to take advantage of the sun. A normal plastic water botle of 10 liters covered in black can be heated to just above 80 degrees C before the plastic starts to melt down. Even 60 -65 degrees is enough for geting safe driking water. Water heaters does not have to be very complicated. A black botle is enough to get water heated up to 45 degrees. A small reflector at the base can heat it to about 60 degrees C. Leave and forget the botle a few hours, come back and voila! – there is hot steeming water!

This botle heater keeps the botle in a 45-50 degrees position. In this way you can heat the botle from any angel.

A black

Here is another variation:

Heating water demands a lot of energy. Why use valuable electrical energy, when the sun can do the job? In the end of the day you have hot water for every purpose you want. We found that our children enjoy this very much. In our part of the world we are now approaching the dry cold season and tap water is usually quite cold. If the whole familiy wants to take a hot shower, there might not be enough water in one botle, but then we just add more botles.

Se referanse : Botle Heaters

This time I wanted to get to the real thing. I found some people who where willing to put it together and after a week they came back with a brand new solar cooker. I wanted the solar cooker to be done locally to stimulate local business. This was just the first model we tried out, and there should always be room for improvements. But I was very happy that this first solar cooker turned out to be succsessful. After cooking and tasting the food with my friends it turned out to be a very nice experience.

The interest in this type of cooking is now growing and the women are posing all their questions.

Se referanse : Solar Cooker locally build

Lately I have tried to build some of the 3D models based on 2D printouts. Of course it is possible to put the models out in the STL format and send them over to the folks at CAD span. But the price tag is still a bit heavy. As I am on a low budget, I found it therefor more helpful to make the models in 3D on my computer and then project them piece by piece onto a 2D format. On a small scale base, they then can be printed out on a ordinary printer before being glued and put together in its ordinary 3D shape. The process is fast and easy and reliable for the small scale models. The 1:1 scale is a challenge. The printing can be done using a software like Posterize. This handy software let you print out images in any dimension. I tried up to 60 pages to get the full scale model. This was then transfered to cheep aluminum or other materials to get the reflector designed. The challenges that arises are linked to the functionality of the models. I found that even though it works well on a small paper based model, full scale models with other material, gave me quite a different picture. My software does not allow me to test out or analyze the functionality, it just gives the geometry. The geometry can look nice but it should not be a big surprise to anyone that reality always is more complex than our designed models! They often gives me small surprises based on details that gets bigger in a full scale focus, or the way material change based on the dimension being used. Bigger models demand another level of support and structure than small models.

Still by making the models as accurate as possible in the design process, and then making some small models, a lot of problems can be found and corrected before going full scale.

Se referanse : 2D design for 3D models

There seems to be an widespread confusion about how solar rays reflect in an cone. If sun rays was like water, it is easy to believe they would “fall” down the tube and end up at the bottom of it. This is certainly not the case. Sun rays reflect on a surface (generelly) with the incomming angel equal to the outgoing. To understand what I mean take a look at the illustrations here:
This has some very strange consequences, and some of these are very important for us constructing solar cookers. The rays of the sun will eventually bounce back if the cone is too long. This does not hold true only to very wide cones as someone might belive. It is also true to very very steep cones. In other words in nearly any cone, the rays will eventually bonce back if the cone is long enough. Does this affect your solar cooker? Most likely not, but if you want to lear more, take a look at the examples here.

Se referanse : Does the rays of the sun bounce back in a steep cone or not?

This week I am presenting what I for the moment is calling Conical Ground Cookers. I called them Ground Cookers because they rest on the ground or very close to the ground only supported by a little stand for tilting purposes. Many of the photos in this series show also how the sun reflects in the parabolic structure. The biggest model is 130 cm off the ground, (this is with a with of 145cm). With this model I think it is most convinient to bring food in from the hole at the base of the parabol. This was originally meant to allow for tilting, but can also be used for adjusting the hotpot in the middle. In the albums this week you’ll find several different variations based on the same model. Some differences are related to how I have made the cut of the parabolic cooker. Other differences are related to size. Someone suggested a smaller model would be nice, and so I did. The latest model has a hight of 50 cm and a with of 75 cm. This allows for a hotpot of about 20 cm with, wich in most cases should be ok.

The Conical Cooker is also called a Fresnel Cooker. (http://solcooker.tripod.com/solar5.htm) Others have also suggested a Compound Cooker, as the focus is a low and the parabolics very deep. The one I am presenting this week is made up of 8 cones + the base. Normally a Conical Cooker would have 1-9 cones, but Conical Cooker with more than 20 cones is not impossible. The more cones, the smaller the focus and the hotter it gets. It provides a very hot focus, but is more difficult to cut aut and put together. The advantage is that they can be much bigger and still keeping the focus on hotspot. This is the opposite of parabolic sectors that gets wider and wider the further from the center and thuse loosing some of their effect. The only way to eliminate this problem is to add more sectors or wings. Conical Cookers comes in two different models based on the cones. The Cones can be constructed with the idea of a) sharing the same with or b) with the idea of covering the same area of sunlight each cm. In the album this week (http://solarcookers.ning.com/photo/albums/8-cones-conical-cooker) the conical solar cooker is made up with cones that gets wider and wider the further they are from the center. For the cones this does not hurts their effect. It is simply to compensate for the fact that the parabolic is geting steeper and steeper. Each cone is covering the exact same area as the other cones in the parabolic structure.

The fun thing is that conical cooker can be cut out and put together from one singel sheet of paper, metal or or other types of materials. Try it out, even from a A4 paper with some aluminum foil glued to it, it is a fun experience!

Se referanse : Conical Ground Cookers

Some solar cookers take their name from the cooking space, others, like pannel cookers, take their names from the type of reflector being used. Again other, like solar grills and solar parabolics may take their name from how the reflector is curved, if it is a deep curve of shallow curve. To help myself and maybe others too to get things straight, I have made a proposition for terminology to classify solar cookers. I know there are some classifications out there already, but the subject is probably far from clear.

Solar Grill
A cooker with a very shallow reflector would normally be called a solar grill.

Deep Solar cooker.
A cooker with a deep curve would sometimes be more of a cooker. I suggest to simplify this to use approximately 0-45 degree for the grill, and 0-80 degrees for the cooker.

Box cooker.
Traditional box cooker on the other hand takes their name from the cooking spot, but represent anyway an continuation of the parabolic curve, as the reflectors can have no more than 45 degree. Box cookers without reflectors are also possible, here the name is perfectly understandable.

To simplify the task I limit the scope to cathegories depending on type of reflectors and cooking spot. The reflector in the other hand is divided into four cathegories depending on shape, curve and the shape and size of the elements of reflections.

In my view, the solar cooker could take its names from many different cathegories depending the type of specification. I am giving three examples here of well known solar cookers, and indicating what specifies each one of them. As you probably see, more than one yes, in each cathegori, indicates sub variations and gives a possibility to classify these variations.

Number of variations based on the standard Solar Grill will normally be:
2* 1 * 4 * 2 *2 = 32 variations. A possibility to name each variations should then be possible.

Many more types than the standard three mentioned below, and could probably be classified according to this therminology and system. It should also be possible to find and evaluate new types of solar cookers based on this classification.

You find my proposition for classification in pdf format in the forum.

Note: this is not a final classification, but a proposition open to discussion and change. This dicussion should contiune, but this was anyway my 10 cents.

Se referanse : Classification and Therminolgy for solar cookers

Allong with many other sites, we are happy to annonce that we got an inspirational third price on the contest. Diplomatically we shared the price with some other sites.

The entries were judged mainly on three things: #1. Was the web page pleasant, with good navigation, good spelling, and a good attitude? #2. Did somebody REALLY use a solar cooker? Photos were very important! #3. Did this web page make us want to leap up and cook something using the sun? (#1 was not as important as
#2 and #3!)

Here is the full list: Make sure to pay them a visit!

http://solarcooking.wikia.com/wiki/Solar_Fryer

Mueller’s Website
mueller-solartechnik@gmx.net

Global Crisis Solution Center with Morgan
http://globalcrisis.info/solarcooking.html

Ron N. & Fun Panel!
http://sites.google.com/site/suncookers

Basshunter’s Page
http://www.freewebs.com/howtosolarcook

Jon’s Website
http://trumpetsrock.weebly.com/solar-cooking.html

Caltosy’s Website
http://caltosy.googlepages.com/solarcooking

Second Place was shared by

SolarGourmet with Michael
http://www.solargourmet.de/

and

Going Solar Now with Tracy
http://solorcooking.blogspot.com/

First Place went to Michelle & Jonathan of Greenjoyment.com.

Special thanks to http://solarcooking.org

Congratulation to the winner !
- and we promise to come back stronger next year with nice full working models and solar cooking food!

Se referanse : Third Price to solarcookers.ning.com at Solar Cooking Web Page Contest!

Today I added a new design to support development of a cheap but hopefully fairly effective solar grill for developing countries. I think that I one day also can get to build it, but some more reflections needs to be done. The intention with this parabolic design was partly to adjust the form to materials easily found in developing countries, partly to find a design that can be tilted by its own shape. The metal plate is 1*2.5 m and is sold for 10 Euros in Congo-Brazzaville. It is not perfect but fairly reflective. I have provided a image to show how to cut it. It should also be possible to use 250 small square mirrors 10*10 cm. This is more expensive, and a bit complicated, but more effective than using the metal plate. For the support I am using a wooden frame divided into segments. The wooden frame also provide tilting functionalities, but will be developed further. An alternative is to use a metal stand. Both ideas are displayed in the photo album “Parabolic grill on wooden frame” .

Se referanse : Parabolic grill on wooden frame for developing countries.

While there for a couple of years back was hard to find new projects about solar cooking, today you will find them easily on the net. Solar cookers are coming together from all over the world helping each other out with ideas and their newly gained experiences.
Solar cookers today have started to find their proper shapes and forms thanks to years of experience. Yes, it is true they are coming in many different shapes and fashions, and it can be a bit confusing to tell the difference between them. But if we want to put it simple, they can be classified into three main categories.
We have the solar grill, the panel cookers and the solar stove or box cooker. We can explain the difference between them related to how the reflectors are placed .The box cooker is placed below the reflectors and needs to be well isolated. It uses normally 1 to 8 reflector plates to gain heat. The solar grill is placed above the reflector, or between the sun and the reflector and uses a parabolic shaped reflector to gain heat. This generates normally more heat quicker and therefore isolation is not required. We might explain the flannel cooker as sort of combination of the two above. The food or the hotpot is placed on the ground or just above the ground with reflectors surrounding it, over it, and sometimes also under it. Explaining the difference can also be done related to a parabolic curve, as the three main types are using different zones of the parabolic shape.
If you consider buying or making a solar cooker, take your time to find out what you really need. Do you want to cook food fast with high temperature? Do you have plenty of time, or do you wait eagerly for your food to be ready? Do you want something cheap and simple to heat water, something more advanced? Not all these questions need to be answered before you begin, but taking a look of the different illustrations on this page can help you decide what you need. Also if you want to construct a solar cooker for yourself, it is not too difficult. Check out this site, it might turn out useful to get going!

Se referanse : How to find your ideal solar cooker?