Biogas Backpacks

January 7, 2015 by kris de decker Filed Under: Biogas, Energy, Random

biogas backpacks

Katrin Puetz saw the potential of biogas for rural communities while doing her master’s thesis at a university in Germany. She wondered how to do the “last mile” of distribution from a central digester site to someone’s home. She came up with the biogas “backpack” — a sturdy bag to transport the gas.

Since then, she’s created a full line of products for villages to use biogas locally. First there’s a 2 x 5 meter bio-digester “system” for 44 pounds of cow dung a day. It’s a tank with an outer tent covering. Then, there are the packs which hold 1.2 cubic meters of biogas at a time (6 kilowatt-hours of energy or enough for four hours of cooking). And there’s a simple stove and several other parts.

The bag has a valve that attaches to the stove with a hose. Villagers place a rock or plank of wood on top of the bag to push the gas out. The bag presents no explosion risk because it is isn’t pressurized, Puetz says. “You can put the bag on an open fire and it will take 15 to 20 seconds to even melt the material. It is a very heavy duty material. And even after you’ve melted a hole the gas will come out and slowly flare off, because biogas needs to be mixed with air to be flammable,” she assures us.

Read more at Co.EXIST: These hilarious inflated backpacks are actually delivering cheap local energy to the rural poor. Picture: (B)energy. Previously: Gas Bag Vehicles.

Photographs of American Indians

January 6, 2015 by kris de decker Filed Under: Biodiversity, History, Random

photographs of american indians

“First People” hosts a large and wonderful collection of American Indian photographs online, dating from the late nineteenth and early twentieth century. Aside from the portraits (which include, among others, the Edward S. Curtis archives), there are picture galleries of tepees, boats, pottery and basketry.

Previously: Walter McClintock’s glass lantern slide collection of the Blackfoot Indians. [Read more…]

The Big Velomobiles Graphic

November 22, 2014 by kris de decker Filed Under: Bicycles, Bikes, Pedal power, Random, Tricycles, Trikes

velomobiles graphicMads Phikamphon from Denmark published an infographic depicting 27 velomobiles with their specifications and performance. It’s a handy overview for those who are considering to try one of these vehicles that blur the lines between cars and bicycles. The infographic was originally published at Cykelvalg. We leave the word to Mads:

“Most people consider velomobiles as a rather new invention, but the first velomobiles were actually invented much earlier than most people think. In the 1930s you could buy a set of instructions to build your own “Fantom” – a velomobile for 2 persons made out of wood. Thousands of copies of the instructions were sold, but few bikes were built and soon the velomobiles were all but forgotten as cars got more and more popular. It wasn’t until the oil crisis in the 1970s that velomobiles again started to get some attention. A well recognized velomobile from that time is the “Leitra” that remains a popular model amongst many velomobile enthusiasts.”

“As you can see in the graphic below, there are now lots of models to choose between if you want a velomobile, although almost all of them share quite a few characteristics: 3 wheels, an aerodynamic body and room for just one person. Thanks to the aerodynamic body a velomobile is also the fastest HPV or Human Powered Vehicle around. In 2013 a “Velo X3” velomobile reached an amazing 134 km/h (83 mph) and many people expect the “Arion” velomobile to go even faster when it’s ready for testing in 2015. The only big problem that remains is that all the models are rather expensive. No velomobiles are being mass manufactured, so the price of a new velomobile remains at least $3000.” [Read more…]

Don’t Heat your Room with Tea Candles

November 19, 2014 by kris de decker Filed Under: Heating appliances, Random

hoax te candle heater

Friends and readers keep sending me links to a “low-tech” heating system in which tea candles heat a combination of ceramic flower pots. It seems you all need a course in thermodynamics, so let’s start with some basics:

1. First law of thermodynamics: you can’t create energy out of nothing, (and you can’t destroy it). This means that placing two ceramic pots on top of four candles does not increase heat production. You get the same amount of heat if you burn four candles without the pots.

2. Now imagine heating your room with four tea candles.

3. Get more tea candles. One tea candle can produce around 30 watts of heat, which means that you need at least 20 to 30 tea candles to heat a very small room (and replace them every 3 to 4 hours).

4. You have now built a small fireplace using tea candles. However, it isn’t running on wood but on petroleum — the stuff paraffin is usually made of. And above all,  you have built a fireplace without a chimney. Chimneyless fireplaces are very efficient, but they’re not so healthy and that’s exactly why the chimney was invented. Connecting your tea candle fireplace to a chimney will solve the indoor air pollution issue, but unfortunately 85-90% of the heat will then escape through the chimney. So you need more candles.

5. Forget tea candles, get some thermal underwear.

Pedal Powered Farming

November 15, 2014 by kris de decker Filed Under: Farming, Pedal power, Pedal powered machines, Random

culticycle pedal powered tractor

The Culticycle is a pedal powered tractor that can cultivate, seed, spray, or pull gear for most low horsepower tasks. We talked about the first prototype almost two years ago. A new version has now been released, built around a modular tractor frame. Tim Cooke explains us how it’s built and how it works:  [Read more…]

Different Types of Windmill Sails

November 1, 2014 by kris de decker Filed Under: Random, Wind Power, Windmills

different types of windmill sails compressed 700 pixels

François Porcher has translated our 2009 article “Wind Powered Factories: History (and Future) of Industrial Windmills” (“Des fabriques mues par le vent: histoire (et avenir) des moulins à vent“) and sends us the image above to complement the illustrations. For a high-resolution image, go here. More articles have been translated to French and other languages.

Previously: