Solar Coffee Maker

Several years ago, I bought a lamp that caught my attention in a garage sale. What impressed me was that its reflector was made of aluminum and had a concave surface in the form of a parabolic mirror. During my initial experiments with this parabolic dish I was able to verify that it has the property of concentrating the sun's rays in a small area and that prompted me to develop the ideas that I will present below.

I love solar cookers. I think they are very useful in environments where there is no electric current or the use of other energy sources is inconvenient. For example, in many places it is forbidden to make campfires, due to the polluting gases that are emitted or for the danger of fire. Hence, the alternative of a Solar Cooker becomes attractive!

In the market there are several manufacturers that have offered us their proposals, such as those that stand out in Amazon, also other creators around the world have shared their designs and experiences .

There is no doubt that we have made a great progress with this technology as it is an effective way to promote a global sustainable development.

Considering this and adding up that I am a coffee lover this idea came to my mind.

Could any of the above solar devices be able to heat a coffee maker of the Italian type and make me a good coffee in environments where I don't have access to the electric current? Sure they can, but those that could achieve it (Parabolic Solar Cookers), at least commercially, are huge to be transported in the trunk of a common vehicle. Luckily, you don't need such a large parabolic concentrator to make 3 cups of coffee.

In this INSTRUCTABLE I am presenting the steps for the construction of a device for making coffee whose energy source is the sun. It is relatively small and is based on an aluminum metallic concentrator, of the parabolic type extracted from a lamp. The design of this device was modeled in FUSION 360. When the modeling it, the materials and tools that I had at hand were considered, which meant a considerable saving in the time of its construction and not big expenses were made.

I hope you like it!

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DARK SUNGLASSES

• Italian Coffee Maker (3 Cups)
• Parabolic dish 450mm in diameter and 110mm deep (a parabolic dish antenna covered with reflective tape could work)
• Five wooden slats, (500mm x 40mm x 20mm)
• Two wooden triangles brackets, (130mm base and 40mm thick)
• Wooden cylinder, (80mm base diameter and 20mm thick)
• Orbital sander
• Sandpaper number (80, 120, 240)
• Measure Tape and marker pencil
• M8 screw (60mm in length), two flat washers and a butterfly nut.
• 15 wood screws (35mm in length, 3mm in diameter)
• Circular table saw
• Jig Saw
• Hand drill
• Drill set
• Phillips screwdriver
• Wood Glue
• Countersink
• Brush and varnish for wood (optional)
• Two M6 continuous thread rods with eight nuts and washers.
• Fan protection grid of a computer power supply
• Heat shrink sleeve

• Mini Wing M6 Internal Thread

Why is it necessary to know the focal length? You will need it to know where to place the object you want to heat. In our case it is a classic Italian coffee maker.

There are several ways to determine the focal length of a parabolic dish. In Wikipedia it is well explained how to calculate it if the following magnitudes are known: parabolic disc depth (D) and its radius (R). I attached an image of when I made this calculation that you might find useful.

Another way to determine the focal length is experimentally. If you have no idea where the focus of your parabolic reflector may be, I DO NOT recommend trying to locate it with the help of the sun as it can be dangerous. My recommendation is to do it at night time, focusing the dish on a distant light source such as a street light lamp. Using a sheet of paper try to achieve the position where the image of the lamp or the light emitted by it, is better defined (concentrated) on the paper. The position where this occurs is called FOCUS of the parabolic reflector.

If you want to use in this project a parabolic dish with displaced focus such as DIRECTV, Dish Network or similar satellite dishes then I recommend this website with excellent information.

Note: Strictly, the three-dimensional shape of the parabolic reflector is called a paraboloid.

Perhaps one of the innovative aspects in this project is the design of the dish support. For the correct operation of this project, it is necessary to adjust the dish towards the sun to concentrate the reflected light in the focus. It is generally necessary to realign the parabolic reflector every 25min, which is a repetitive task that requires a simple alignment mechanism. It requires a system that is able to adjust the TILT and PANNING quickly and preferably without tools, only with the hands. Simply loosening and tightening a butterfly nut, the support I propose is able to adjust the angle of inclination of the parabolic dish from 0 to 85 degrees from the horizontal and a 360-degree rotation coverage, which will allow you to focus the sun at any time of the day and almost anywhere on the planet.

My support for the parabolic dish is made of wood: a material that is relatively easy to work, durable for this function and can be recycled, for example, from PALLETS. Those who wish to build it, can do so even if they do not have “sophisticated” tools. Taking the principles set out here and sacrificing aesthetic details, a similar device could be built with wooden logs, nails and a hammer. The previous idea is very convenient in developing countries where access to energy sources is a big problem and contributes to deforestation, desertification, death by inhalation of pollutants derived from combustion, fires, etc. The design is fully scalable depending on the size of the parabolic dish and its focus. In addition, the parabolic dish could be easily disassembled from the support structure in minutes. During the day, it can be part of the solar coffee maker and during the night or when desired it can fulfill its original function.

Take two of the wooden slats (500mm x 40mm x 20mm) and make a cut of (40mm x 20mm x 20mm) in its central part. To do this, I made the marks and used a table saw to which I adjusted the height of the cutting blade to 20mm. With great care I made several cuts in the marked area until I obtained the desired cut in both wooden slats.

To do this I made a mark 20mm from the top end of the wooden slat and 20mm from one side. Using a hand drill and an 8mm diameter drill bit, I made the hole. I would have preferred to do it in a drill press but I didn't have one. The hole was not completely centered, but it has no relevant importance for its operation. Optionally, you can reduce the end of both slats with a sander and sandpaper number 80-240 giving them a rounded appearance.

The coupling would look like a cross, where a slat goes into the cut that was made to the front leg in step 3. I made two 3mm through holes at the back and center of the front leg. Later, I countersunk the beginning of the holes so that the screws penetrated into it and were not exposed. I covered the joint with wood glue and using a Phillips screwdriver I screwed both pieces together.

Mark the center position of one of the slats by its widest part and make 2 through holes, 3mm in diameter. Using the countersink, make a cavity where the heads of the wooden screws enter. Place some wood glue and screw the horizontal leg to the front leg.

The wooden cylinder I used was an 80mm based diameter and 20mm thick. These dimensions were appropriate for the type of parabolic dish I had, but they may vary depending on the type of reflector you have. I cut it from a piece of wood 20mm thick from where I also extracted the wooden slats declared in the list of materials. Using the orbital sander and starting with 80 grit sandpaper until 240 sand, I gave the piece the desired finish. I liked to give this piece a round shape, but if it is appropriate to make it rectangular, it can also work. Later, I marked the central position in this cylinder and made a 3mm through hole in this piece. As in previous steps I placed some wood glue around the hole I had just made, and then screwed it to the rest of the structure.

The focal length of my parabolic dish is 115mm from the deepest part of the disc and vertically outward. I cut the extension arms 200mm long. To each of these, I made 2 through holes for the widest part separating them15mm from two of its ends. They were countersunk after that. As in previous steps, I used wood glue and screwed them into their positions.

I used two triangular brackets, 130mm long and 40mm thick. These pieces would provide some structural rigidity and guarantee a right angle at the junction made in step 8. If this angle is not straight, it would offer difficulties to place the front support where the Italian coffee maker and perhaps other kitchen utensils would be placed. To these I made 2 through holes and countersunk them. I placed wood glue in the area of the joint and screwed them into their positions.

Remember step 3 where we made the cavities to two of the wooden slats? We have only employed one of them. This remaining slat will be the back leg. The cavity we made in step 3 to this one is so that it can be completely folded over the rest of the parabolic dish support structure. The joint must not be completely fixed and the union screw must be tightened leaving some margin for this operation. Flat washers should be placed at each end to prevent damage to the wood during the tightening-loosening operation. If you have a “butterfly or wing” nut, this process will be much easier. Optionally, you can varnish the entire structure as it will give the structure a better finish and moisture resistance.

This step concludes the construction of the wooden support. It is necessary to create the other metallic support where the Italian type coffee maker will be placed.

The parabolic reflector that I used originally had three holes in its central part. Using these holes, I was able to screw the parabolic dish to the wooden circle of the support.

This support must be made of metal since the parabolic dish is able to easily burn any wooden object that is placed in its focus when it points towards the sun. My proposal is two threaded rods that would hold the fan grid. The rods must pass through the two holes of the extension arms that was built in previous steps. The central part of the grid should be placed on the focus of the parabolic dish. The union between the rods and the grid must be made by nuts.

One of the rods was left larger and the surplus bent 90 degrees to be the tilt adjustment hand. It was also covered with a piece of heat shrink sleeve.

Once you adjust the tilt and panning of the parabolic dish, then you must adjust the angle at which the grid is horizontal.

Wear dark sunglasses during the entire test. First, do not forget to fill in the
bottom part of your Italian Coffee Maker with water up to the safety valve. Second, put some coffee powder on the filter basket. After that, place the Italian Coffee Maker on the metal support and then adjust the tilt and panning, making sure that the bottom and / or sides of the Italian Coffee Maker are well lit with the light that is reflected in the parabolic dish. When you place the object you will notice a great glow. That area will be warming up immediately.

Note: Even if you don't see the hot zone when there are no objects in the spotlight, high temperatures will develop in that area, in the order of 280 degrees Celsius or higher, avoid running your hand through that region.

In my tests I was able to make a coffee in just 12 minutes. Not bad for such a small dish. Depending on the sun conditions in your area and the characteristics of your parabolic dish, these values may be better!

Like a gas cooker, you can adjust the temperature reached to a lower value if only the position of the support changes slightly, decreasing the amount of light that hits the object to be heated.

Dark metal surfaces will heat up much faster than polished metal surfaces, so keep that in mind.

If you have completed all the steps and followed my recommendations you should already have your own small, portable and very powerful Solar Coffee Maker. I must admit that at the beginning I had doubts about the results I was going to get when I set out to carry out this project, but when I made my first coffee with this device, I felt very satisfied with the results and I knew that I had done something positive. I also believe that from an educational point of view it could be built in a school environment and encourage the spirit of protection that our planet needs so much.

If you have at least 30min of good sun a day you can carry out this project!

Times are changing and "everything points towards the Sun". Maybe when you see a satellite dish, a pot lid or a lamp reflector you will put aside for a moment their regular uses , and consider making your own version of this project . Good Luck!