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To catch the rain cover.png You made it happen! Get a paperback on Amazon or digitally at

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Building a very hot parabolic solar cooker using pedal power tools.
Notice how the focus is the same for the various parabolas.
Aleiha's parabolic solar cooker. The paraboloid is an interesting shape with some amazing qualities. It has the power to concentrate light, electronic waves, sound, etc. to its focus at the center. To find the focal point of a paraboloid, one must use the formula, y=p*x^2, where p is a constant. The variable y is the depth of the dish, and x measures the distance from the center axis to the maximum circumference of the dish. You have to pretend that there is an x axis going through the center of the base of the dish and a perpendicular y-axis passing from the center of the base of the dish to the focal point. The two numbers, x and y, represent a point on the paraboloid, and from that, you are able to determine where the focus is.

Parabolic cookers have been used for centuries now. The idea to concentrate light using curved mirrors was developed by the Greeks, Aztecs, Incas, Romans and Chinese. The Incas used bronze and gold for their mirrors and they built structures that were several stories high. This technology seems to have appeared around the same time for each of the civilizations. It is thought that Archimedes harnessed the technologyW to defend Syracuse from invading Roman fleets in 212 BC.

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CCAT pedal powered innovations

Years of pedal powered innovations from CCAT, all in one place.

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Community action news

Piccadilly Gardens, Manchester.jpg
Mar 21 Greater Manchester is setting out its ambitions to become one of the leading green city-regions in the UK and Europe, at today's inaugural Green Summit [1]

Mar 19 London news: London’s first eco-friendly, human-powered gym is opening [2]

Mar 15 California news: How Cooperation Richmond is empowering marginalized communities to build an equitable economy [3]

Mar 7 Climate action UK: UK carbon emissions in 2017 fell to levels last seen in 1890 [4]

Mar 1 South Africa: Cape Town’s water crisis shows the reality for cities on the front line of climate change [5]


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Helen Keller
The mystery of language was revealed to me. I knew then that ‘W-A-T-E-R’ meant the wonderful cool something that was flowing over my hand. That living word awakened my soul, gave it light, joy, set it free.

Helen KellerW
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Hot topics / In the news

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Planted cattails at Millcreek greywater
Greywater, sometimes also spelled as graywater, grey water or gray water, is all of the effluent water from a household, such as water discharged from lavatories (bathroom sinks), bathtubs, showers, clothes washers, and laundry trays. Greywater is not wastewater from a sink used for food preparation, or water closet (toilet) wastewater.

The water leaving our homes carries nutrients and value. It may also contain pathogens, and/or harsh chemicals and care should be taken with it. However, it is not a great risk compared to blackwater (sewage).

Redirecting the water we use for tasks such as showering allows us to reclaim some of that value to grow plants and recharge the water table. It may be necessary to choose our soaps and detergents more carefully, if we use the greywater for watering and fertilizing plants.

Main portal: Water
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Engr305 Appropriate Technology Projects: Below are selected service learning projects from Engr305 Appropriate Technology, which is a course on appropriate technology at Humboldt State University taught by instructor Lonny Grafman.

AEF food dehydrator

A solar dehydrator to help preserve surplus crops  
AEF greywater

Greywater system at the CSA, Arcata Educational Farm  
AEF informational kiosk

An earthen informational kiosk  
AEF photovoltaic system

Modified off-grid photovoltaic system  
AEF solar water heater

Improved solar water heating system  
AEF spiral herb garden

Restored the existing herb spiral  
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