LOW←TECH MAGAZINE English

Low-tech Magazine: The Uncompressed Book Series

Mon, 30 Mar 2026 00:00:00 +0000

Image: The redesigned and revised chronological book edition. Photo: Marie Verdeil.

Between 2019 and 2021, Low-tech Magazine published three books containing selections of articles from the website, spanning 14 years (2007-2021). In 2024, we launched the “compressed edition”, which squeezes the article catalog of the three-volume book series into just one book of 620 pages.

We did this by switching to a smaller font size, downsizing most images, and opting for a two-column layout. I rewrote some articles, especially older ones, resulting not only in fewer pages but also in better articles.

This revised edition of the original, “uncompressed” series is based on the edits made for the compressed edition. However, we increased the font and image sizes and returned to a one-column layout for improved reading comfort.

The book design is a collaborative effort by Laia Comellas, Marie Verdeil, and Johanna Gratzer. Marie Verdeil made the covers, Vaiva Vinskaitė did the typesetting.

Image: The redesigned and revised chronological book edition. Photo: Marie Verdeil.

The books are available in paperback and hardcover:

Paperbacks:

Hardcovers:

Volume IV (2022-2026)

We’re also working on the final edits for Volume IV (2022-2026), expected to launch in May.

Patrons have free access to all ebooks, and early access to print books at a reduced price. They also receive exclusive content, which includes previews of new building projects and behind-the-scenes news.

Our books are also available as epubs. However, the chronological series is still based on the original book edition. We temporary lowered their price and will launch the new versions in a couple of months.

Winter is Coming: Build a Solar Powered Foot Stove

Sun, 16 Nov 2025 00:00:00 +0000

Image: The electric foot stove that we build in this manual. Photo by Marie Verdeil.

We built an electric cube heater, powered by a 100-watt solar PV panel. During the day, the solar panel slowly heats the cube, which radiates heat to its surroundings. Due to its high thermal mass, the object continues to radiate heat for hours after sunset.

Electric Foot Stove

The heat cube can serve multiple purposes. You can use it as a modern variant of a preindustrial foot stove. Put your feet on the cube and throw a blanket over your lap to trap the heat.

Historically, foot stoves contained glowing sintels from the fireplace, but an electric version is safer and healthier. There is no risk for carbon monoxide poisoning or fire. The heat cube contains no flammable materials.

Image: A nineteenth century foot stove. Source: Museum Rotterdam (CC BY-SA 3.0).

You can also put the cube under a table that has a blanket on top, and that is another method to build an electrically heated table. The heat cube can also quickly dry a pair of socks or keep a prepared dish warm in the kitchen or on the table.

Rather than storing electricity from a solar panel in a battery to operate an electric heater at night, the solar panel stores heat in the thermal mass of the heat cube itself. That’s cheaper and more sustainable, because batteries account for 70-90% of the money and energy invested in an off-grid solar PV system.

Heat can be stored for even later in the night by covering the cube with one or more wool blankets.

Image: The heat cube used as a hand and foot warmer. Photo by Marie Verdeil.

Bricks, Mortar, and Tiles

We created the heat cube using inexpensive and simple materials: bricks, mortar, and tiles. The solar panel supplies power to an electric resistance heater, which we made ourselves and which we laid between several layers of bricks. The electric resistance heater connects directly to the solar panel, without a solar charge controller or voltage regulator in between. If you add more solar panels, the heat cube also works in cloudy weather.

Electric Tile Stove

Our heat cube is relatively small (20x20x25cm), but this manual can serve to build a much larger version, which could take the form of an electric tile stove, which could include a heated bench or sleeping platform.

Tile stoves date back to the Middle Ages and accumulate heat from a biomass fire within a stone or brick mass. They are fired only once or twice per day and continue to radiate heat for approximately 12 to 24 hours. However, a tile stove can also work electrically. In that case, there is no need to add a labyrinth of smoke channels that delays the release of heat through the chimney; instead, only layers of bricks with electric heating elements in between are required. Neither do you need a chimney.

Image: A 1920 tile stove in the "Tautes Heim". Source: www.tautshome.com (CC BY 3.0).

Tile stoves are very heavy, and powering them electrically doesn’t make that any better. Once built, they remain in place. Even our small cube heater is not precisely a portable device: it weighs 26 kg. If you want to move it around, it’s a good idea to put it on a wooden board with wheels mounted underneath. Make sure it can’t slide down a slope.

Solar Oven vs. Foot Stove

This solar-powered cube heater forms part of a larger collection of devices that we built, including a solar powered oven and a solar powered coffee maker. They are all based on direct solar power and heat storage rather than electric energy storage.

All these devices are inspired by tile stoves. However, while the solar oven and coffee maker are designed to keep the heat inside, the cube heater is designed to radiate heat outwards. Therefore, it is the only appliance that has no thermal insulation. That also makes it easier, quicker, and cheaper to build than the others.

Thermostat

The heat cube we built works without a thermostat. Because it has no thermal insulation, there is little danger of overheating and damage to the electric resistance circuit. It’s the room that gets warmer: the cube continues to radiate heat into its environment and maintains a steady temperature. Furthermore, the sun goes down every evening, cutting off the power supply.

However, overheating could occur when you charge the heater with one or more blankets on top, effectively adding insulation, or when you operate it on grid power using an AC/DC converter. To avoid this, you can add a thermostat, which turns off the power source when the surface temperature exceeds a preset limit.

A thermostat can also be helpful when the heat cube surface becomes too hot to touch with bare skin. However, you can also wrap a blanket around it or make a fitting cover, similar to the ones used for hot water bottles. Installing an on/off button provides you with a manually operated thermostat.

What You Need

Six bricks. We used refractory bricks (also known as fire bricks), which are used in high-temperature environments. Refractory bricks are made of silica and store thermal energy very well. However, regular bricks work as well, because they withstand temperatures much higher than those reached in the cube heater. Just make sure the bricks have a 1:2 size ratio, allowing you to create a pile with alternating brick layers.
Mortar. We used regular construction mortar, which can withstand temperatures up to 300°C. Refractory cement combined with sand and water could also work. However, it’s not a requirement because the heater doesn’t reach a temperature of 300°C.
Electric resistance heating element. We made a 100-watt electric resistance heater, which we fixed in the mortar between the bricks. It’s made from nichrome wire and heat-resistant electric cables. See our separate manual.
Tiles. We used ceramic tiles to cover the sides and the top of the cube, and a thicker floor tile at the base. The tiles radiate heat, waterproof the structure, and help to keep it together.
Adhesive mortar. To paste the tiles to the bricks.
A fuse. You add this in the positive wire between the solar panel and the heat cube. Its Amps rating should be slightly higher than that of the heating element. Read more about fuses.
A thermostat (optional). In contrast to the other devices in this collection, the heat cube does not have a thermal switch and thermal fuse. You could add a thermostat to regulate the temperature of the heat cube (see our manual on building an electrically heated table).
An on/off switch (optional). Add this when you don’t have a thermostat.

Image: Step by step instructions to build the heat cube. Illustration by Marie Verdeil.

Building steps

Cut a large and thick floor tile into a square. Its dimensions should be bigger than two bricks lying side by side. We have more information about cutting tiles in the solar oven manual.
Prepare the heat-resistant circuit of 100W. Since we have three layers of bricks, we prepare two separate strands of nichrome wire to evenly spread the heat. One strand goes between the first and second layers of bricks, and the other between the second and third layers. Solder both strands to heat-resistant electric cables. Next, connect these heat-resistant electric cables in parallel. To decide the length and the thickness of the nichrome wire, and other building steps, consult our separate manual.
Prepare some construction mortar following the package instructions. Apply some mortar to the bottom tile and place your first brick on top of it. Add some mortar on the inner side of the second brick before pressing it next to the first brick.
Add a generous amount of mortar on top of this first level and place the first part of the resistance circuit, ensuring the nichrome wires are spread evenly, don’t cross, and remain in the center. Take care that the nichrome wire doesn’t come closer than 5 cm to the sides of the cube, otherwise the surface becomes too hot.
Cover with more mortar and layer a second level of two bricks, perpendicular to the first one.
Place some mortar on top of the second level before laying down the second part of the circuit. Make sure the ends of both circuits are on the same side of the cube and that the heat-resistant cable ends extend at least 5 cm beyond the cube. We will connect them in parallel later.
Place the last layer of bricks, perpendicular to the second level. Use the leftover mortar to fill the holes on the edges of the bricks.
Wait 24 hours for the mortar to cure.
Solder the two separate circuits together in parallel, ensuring there are a few centimeters of space left to extend the circuit with regular cables later.
Prepare some adhesive mortar and cut the tiles for the five sides of the heating cube (except the bottom).
Drill two holes for the cables through the tile on the side where they stick out.
Apply generous amounts of adhesive mortar on all sides and cover the surface. Let it dry according to the mixing instructions.
Once dry, apply grout in between the tiles’ edges.
Connect regular electric cables to each strand to create a power supply cable. We made it 1m long. Optionally add connectors at the end of each cable. The simple resistance circuit has no polarity.

Image: Six bricks form the main mass of the heat cube. Photo by Marie Verdeil.

Image: All bricks are fixed to each other with a mortar layer that also has the electric resistance heating elements inside. Photo by Marie Verdeil.

Image on the left: Tiling the heat cube. All tiles are provisionally taped around the bricks. Image on the right: Grouting the cube. Two holes in the side made to let the cables pass through. Photos by Marie Verdeil.

Credits:

Concept: Kris De Decker
Design: Marie Verdeil
Construction and documentation: Marie Verdeil, with assistance from Hugo Lopez.

How to Brew Solar Powered Coffee

Sun, 09 Nov 2025 00:00:00 +0000

Image: The solar powered coffee maker that we build in this manual. Photo by Marie Verdeil.

There are many different methods for making coffee, some more energy-efficient than others. However, there are no coffee makers that you can power with a small solar PV panel. For example, a commercially available 12V DC drip coffee maker requires a solar panel of 300 watts to brew coffee and keep it warm.

The key to making a more energy-efficient coffee maker is insulation. Regardless of which conventional coffee maker you purchase, it will typically have little to no heat insulation, and most of the heat generated by the energy source will be wasted into the environment. Therefore, we made an insulated solar electric coffee maker ourselves.

Our coffee maker operates on the same principles as our solar-powered oven and runs on a 100W solar panel. We embedded an Italian coffee maker—a moka pot—in a mortar slab, surrounded by cork insulation and a layer of ceramic tiles.

We embedded an Italian coffee maker—a moka pot—in a mortar slab, surrounded by cork insulation and a layer of ceramic tiles.

Image: Connecting the coffee maker to a solar panel. Photo by Hugo Lopez.

Image: Cross-section of the coffee maker. 1. Tiles, 2. Cork, 3. Mortar. Illustration by Marie Verdeil.

The cooker has an electric resistance heating element integrated inside, which is directly connected to the solar panel without a battery, solar charge controller, or voltage regulator in between. Although it’s solar-powered, the coffee maker can be located inside your kitchen or next to your bed—only the solar panel needs to be outside.

Although it’s solar-powered, the coffee maker can be located inside your kitchen or next to your bed—only the solar panel needs to be outside.

The moka pot was invented in 1933 and uses pressure rather than gravity or a pump to brew coffee. It consists of a bottom chamber (a boiler that acts as a base), a funnel filter with a plate and a rubber joint, and an upper chamber where the coffee is collected. Just before the water boils, the steam increases the pressure inside the heating vessel, pushing the water through the filter and the ground coffee. The moka pot is an energy-efficient appliance, comparable to a pressure cooker for food.

How to brew solar-powered coffee

Once the solar panel receives sunlight in the morning, the coffee maker will start heating up. Consequently, if you put water and coffee in the machine in the evening, the sun will brew your coffee in the morning. Coffee is often a collective beverage and our coffee maker is most practical when several people use it. The first coffee takes roughly one and a quarter hours to make. However, once the mortar slab is warm, subsequent brews take only 20-25 minutes.

Preparing the coffee works similarly to a regular moka pot. You unscrew the top part and remove the funnel, fill the bottom part with water until the valve, place the funnel back, fill it with ground coffee, and then screw the top part back on. To serve the coffee, you unscrew the top part using the longer handle we attached to the moka pot. The handle was inspired by the Arabic raqweh.

Image: Unscrewing the top part of the moka pot. Photo by Marie Verdeil.

Image: Preparing coffee. Photos by Marie Verdeil.

Image: Serving solar-powered coffee. Photo by Marie Verdeil.

Our coffee maker is the first insulated cooking device we built, and there is room for improvement. It doesn’t produce the characteristic gurgling noise when the coffee is ready, probably because the temperature isn’t high enough.

Also, not all water evaporates. Therefore, cleaning involves placing the base under the tap, letting water run in, shaking, and then turning the coffee maker upside down to empty the base. That’s a bit impractical, because the appliance weighs 10 kg.

Because the coffee collects in the upper chamber, it is not kept warm by the mortar slab and the cork insulation. We solve this by wrapping one or more towels around the top part to keep it warm. Alternatively, you could incorporate heat insulation into the design, for example, with a tea cozy.

What you need

Image: The moka pot that we started with. Photo by Marie Verdeil.

Moka pot. Choose the size you need. If you get a second-hand device, make sure that the rubber seal is still in good condition. Also, ensure you can easily take off the handle to replace it with a longer, straight handle.
Mortar. Any construction mortar will work. Make sure it’s not too coarse. Read more about mortar in our solar oven manual.
Metal reinforcement. We pour quite a big chunk of mortar, so we reinforce it with a metal mesh to prevent it from breaking. We use a frying sieve. Chicken wire mesh shaped in a cylinder will work as well.
Cork. For thermal insulation, we use cork sheets available at home decor shops.
Tiles. Read more about tiles and tiling in our solar oven manual.
Chimney. Because the water chamber of the coffee pot is sunk in mortar, you need a way to maintain an opening around the valve to release pressure if the coffee maker overheats. We use a metal pastry bag tip, but any metal tube will work. You can also cut a piece out of an aluminum can and roll it up.
Nichrome wire, heat-resistant electric cable. These are the components for building an electric resistance heater (see our separate manual).

Step 1: Thermal mass and electric resistance heating

Image: Step-by-step instructions (figures 1 to 9). Illustration by Marie Verdeil.

fig. 1 — Start by making a mold for the mortar base. Since the moka pot is circular, we decided to shape our cooker’s heating element into a larger cylinder. Get a wooden board. Use a plastic sheet to form a cylinder and tape it to the board with duct tape. We use an old plastic office folder and shape it around a round cork pad that we place on the wooden board.
fig. 2 — Prepare some mortar and pour a layer of about 2 cm at the bottom of the mold. Let it cure for a couple of hours.
In the meantime, prepare your electric resistance circuit based on the instructions in our manual. We made a circuit with two nichrome wires in parallel (2 x 64 cm) for a resistance of 3.2 Ohms at 18V. It draws around 5.5 Amps.
fig. 3 — Make two holes in the plastic mold to weave the heat-resistant electric cables through. Distribute the resistance wires evenly on the surface of the mortar layer. Make sure they do not touch each other.
fig. 4 — Prepare some more mortar and pour it on top of the first layer so that the electric heating circuit is completely submerged.
Add the metal mesh. Gently press it into the mortar. Ensure it doesn’t touch the nichrome wire and that there is sufficient space in the center for the pot to fit. Add a bit more mortar if necessary so that the mesh is trapped at the bottom. Wait for a couple of hours for it to set.
fig. 5 — Cut the chimney tube at an angle to fit snugly around the coffee pot valve while pointing up. Attach it to the moka pot body with hot glue or clay to ensure it stays in place while pouring mortar. It will later be submerged in mortar.
fig. 6 — Place the coffee pot on top of the mortar layer, in the center. Remove the handle; otherwise, its tip would get stuck in the next mortar layer. We’ll replace it with another handle later in the building process.
fig. 7 — Prepare more mortar and pour it into the mold, around the coffee maker. Fill the mold up to the screw rim of the coffee pot. Let the mortar cure for at least 24 hours.
fig. 8 — Once hardened, remove the plastic mold sheet.
fig. 9 — Let the base dry for an additional 48 hours. Position the base on top of a grid to allow the bottom to dry as well. The mortar should feel completely dry to the touch.

Image on the left: The mold for the mortar slab. Image on the right: The electric resistance heating next to the mold in which the mortar is cast. A metal mesh sieve acts as a reinforcement inside. Photos by Marie Verdeil.

Image on the left: The electric resistance is embedded in the mortar. Image on the right: The moka pot, with the original handle removed, in the mortar slab. The chimney is glued to the base. Photos by Marie Verdeil.

Step 2: Insulation

Image: Step-by-step instructions (figures 10 to 15). Illustration by Marie Verdeil.

We insulate the mortar slab with a 2 cm thick cork layer on all sides (including the top and bottom). We use rectangular and circular cork sheets, 4 mm thick, which means we use five layers.

fig. 10 — Layer 5 circular cork pads for the bottom part. Use wood glue to secure them together.
fig. 11 — Use another five cork pads for the top. Cut out a circle in the middle, about 2 cm wider than the coffee pot, so that there is room to add a plaster protection to the cork. Glue them together.
fig. 12 — Start cutting and layering cork sheets around the cylinder, using painter’s tape to keep them in place. In each layer, make two holes to weave the electric wires through.
fig. 13-15 — Before adding the last sheet, decide where you want to route the cables from the electric heating resistance. You can cut away a path into the last but one layer of cork to allow the wires to pass. We let them out at the bottom. Add the last sheet of cork (fig 15.). Use some tape to secure it.
At this stage, you can run a test. We used water only, in order not to stain the cork with coffee. Test how long it takes for the water to reach the top chamber.

Image on the left: Cork sheets on top of the finished mortar slab. Image on the right: The device is covered in cork and ready to test with a wattmeter. Photos by Marie Verdeil.

Step 3: Tiling

Image: Step-by-step instructions (figures 16 to 21). Illustration by Marie Verdeil.

We chose to cover our coffee maker in glazed tiles. They are waterproof, easy to clean, and commonly used in kitchen furniture, walls and counter tops. Tiles are easy to adapt to various shapes and are aesthetically pleasing. Furthermore, they are easy to obtain and tiling doesn’t require expensive tools.

fig. 16 — First, prepare the surface for tiling. Adhesive mortar doesn’t stick well on cork, so start by covering the cork with plaster. We used plaster bands, similar to those used for medical casts. The bands also help to keep the cork sheets together and fill the air gaps. At this stage, protect the coffee maker with painter’s tape to prevent it from getting plastered.
Leave the plaster to dry for 24 hours.
fig. 17 — Once the plaster has dried, you can tile the surface. We found vintage glazed tiles on the street that we cut into strips and sanded off their sharp edges. For the top part, we use tile fragments from tiles that shattered during the cutting process. Mix approximately a cup of adhesive mortar for walls (which is stronger than adhesive mortar for floors). Using a spatula, spread some mortar at the back of each tile before pressing it against the cylinder. Leave a gap of a few millimeters between each tile for grouting. Repeat this process for the top, and ensure the chimney entrance remains clear. Leave everything to dry as indicated on the mortar packaging.
fig. 18 — Now it’s time to grout the tiles. The aim of grouting is to seal the joints between the tiles to avoid moisture and dirt getting in. Mix the grout with water following the instructions on the package. With a scraper, or an old plastic card, press the paste in between the tiles. After about 20 minutes, clean up the excess grout with a damp sponge. Smooth out each grout line with a wet finger or sponge. Leave everything until it’s dry.

Image: Tiling the plastered surface. Photos by Marie Verdeil.

Step 4: Finishing touches

fig. 19 — Add a handle. Remove the original handle of the moka pot, as it has a vertical design that would get stuck in the mortar. Replace it with a horizontal handle, which gives leverage to screw and unscrew the top chamber and helps to serve the coffee. We made a handle out of wood and attached it with a bolt and nut to the coffee pot using the metal attachment welded on the cylinder. A length of about 20 cm is ideal. Use strong wood because the handle needs to withstand significant stress.
fig. 20 — Wiring. Extend the short heat-resistant cable with a longer 1.5 mm² regular electric cable. Use shrink tape to prevent water or coffee from coming in.
Base. Add a 20 mm thick wood base and cork layer to the underside of the structure. It creates room to lift the coffee maker more easily, and protects the tiles from damaging the countertop surface.
fig. 21 — Done! Brew your first solar-powered coffee.

Image: The coffee maker is finished. Photo by Marie Verdeil.

Other ideas

You could also fit the coffee pot in mortar in an existing box, like an old wooden crate or a scavenged metal drum. Instead of tiles, you could use other kinds of coating with a cement, lime or plaster base. You could also decide to integrate the pot in the kitchen furniture counter.

Credits

Concept: Kris De Decker, Marie Verdeil.
Design: Marie Verdeil, with input from Anna Mareschal de Charentenay.
Construction & documentation: Marie Verdeil, with assistance from Hugo Lopez.
Thanks to AkashaHub Barcelona for the workspace. Living Energy Farm & Cal Poly for their pioneering work on insulated solar electric cookers.