Cheap solar ovens from recycled cardboard boxes

[opsec]

This I am interested in...

[Mike]

I wonder if a giant fresnel lens mounted on the roof of a car and aimed at a large canister of water would generate enough steam power to push the car. Any thoughts?

http://www.jc-solarhomes.com/solar_energy_facts.htm

4. ENERGY IN SUNLIGHT: The energy from the sun  varies from place to place and is very dependent on weather conditions. Without an atmosphere 1.4 KW/m2 per hour is available, but with an atmosphere we can only count on 1KW/m2 per hour in the absence of clouds. So, if asked how much 3 hours of sunlight on one square meter is worth what would you say?

5. $ VALUE OF SUNLIGHT $: How much is one hour of sunlight on three square meter worth? Let’s see, if we’re talking about electricity and we say that electricity is worth $0.10 per KWH than 3KWH’s are worth $0.30. The problem is that PV panels have a radiant energy conversion rate of about 20% or less so three hours of sunlight on one square meter of a solar panel is worth less than $0.06

How about heat? How much is 3 hours of sunlight on one square meter of a solar collector worth if we’re talking about heat? Well 1KWH = 3400 BTU so 3KWH = 10,200 BTU.  Since one gallon of fuel oil contains 150,000 BTU 10,200 BTU’s are the equivalent of .07 gallons of fuel oil.

Comment:
Say the lens covered the area above the car & was always shifting for maximum collection.
lens area: 10'X6'=60sq'=5.6sq.m.

100% efficient energy collection would be 5.6KW/hr =19,000BTU/hr is roughly equivalent to .13 gallons of fuel oil per hour.

Offdalip?  Comments? Corrections?

[Beeherder]

 

Astonished!! Thank you that one went immediately in my Favorites and out to a selected list of friends within moments of discovering it.

Nice physics! Maybe a tracked vehicle (think RR)? Larger collection surfaces that could be interconnected in strings to move heavier loads.

[opsec]

Back to the drawing board...

[Beeherder]

 

Hey, sorry i called you a froggy, its clear you are a nut hugging squirel. So where do you want to hop to next there fella?

Wonder if there is a place for urban people transport systems based on power collectors attached to rear of the passenger compartment? What if each passenger had there own power module and that was the fare to ride? Is there economy of scale to work with here?

How about robotized warehouse/storage retrieval units programmed to step and fetch-it? Could they be compact and light weight enough to attach a power module to or maybe even have power modules parked throughout the facility for the little robot to swap with when its charge runs low? (no human safety factors to accomodate should reduce weight significantly)

just jumpin around outside the box her boss

[Dame]

Is beeherder a cowboy?  home....home...on

[wander]

I set this up today. I tried 3 seperate ways of doing it.

My test involved placing a wireless thermometer in a metal pot with lid. I put the oven bag over the pot, but it was a little on the small side so it wasn't fully enclosed. But it did create an airtight seal...

First I started at 10 AM with the pot, and there wasn't a lot of sunlight. Temperature got up to 120 degrees, not bad for first attempt. Pot was hot to touch, but could be handled.

Second attempt I started at 1 PM with the pot, a ton of direct overhead sunlight. Temperature exceeded my thermometers ability to read it, presumably 250 - 300 degrees. Pot was too hot to touch.

Third attempt I was at 4 PM, losing direct sunlight and slightly overcast.  Temperature was 150 degrees. I also attempted this with a bread pan and thermometer instead of pot.

Lessons learned:
1. Direct overhead sunlight has the greatest effect. Cloud and leaf cover have huge, immediate impact on temperature, probably due to lack of insulation.
2. Cooking receptacle seems to have a large impact as well, need something with a good amount of insulation and conductivity. Keeping the air sealed inside the pot may have had an impact, but not sure yet.
3. Wear sunglasses when handling the reflector in direct sunlight.

I'll try again tomorrow if weather is good.

[opsec]

I can't help but wonder how that dutch oven would perform. Do you have a dutch oven you could try this with?

[Beeherder]

 
from my rusty memory: one joule of energy is used to raise one cubic centimeter of water, one degree centigrade from strarting temperature of 20 C. Please offer corrections or refinements as needed.

How long does it take to bring a half liter of water to a full boil?

Which cooking utensil boils the water fastest?


i hate horses, horses hate me so cowboy i am not. Wandering loose on the open range sounds appealing though.

[wander]

Weather is nice today but I'm not really up for experimenting.

Opsec - that was my first thought - a dutch oven would be perfect I think! I don't own one but I intend to get one.

[B-Lue]

I have a Sun Oven (not cardboard and not cheap).  Folds up neat.  Kinda heavy, but durable and tiltable.  It works well with my cast-iron dutch oven.  I've got some lightweight "graniteware" but I like the cast-iron better.  I've baked cake, made rosemary chicken and roast-beast in it.  The food doesn't scorch or stick, so there's little need to stir.  If you open the plexiglass lid the steam roils out and the temp drops.  On a bright day it'll make it to 350.  Haven't tried to time water to boiling in it. 

[Beeherder]

 
And another bolt of brilliance out of the B-Lue. The only reason i suggested the boiling water experiment was for comparison of the different approaches. I had hoped that this comparison activity would give a reasonable expectation of which would be more effective. Kinda figured the Dutch Oven would win but maybe not at boiling the quickest who knows yet? If there is no scorch or sticking rregardless of which

Sounds like you have this down already. Baking a cake, wow. So maybe it would be interesting to know how well the $12 version works compared to the "(not cardboard and not cheap) Sun Oven". Seems like having a means to cook that does not necessarily require fuel in the traditional sense would be a very good way to be prepared.

[opsec]

Don't forget to get a woodstove too.

[B-Lue]

Oh I think the timed water-boil is an excellent idea, I just haven't done it.  Another  thought would be to compare sustained internal temp after removing the vessel from the solar-box.  Got a remote control meat thermometer that might help with metrology.  That way we could have meat AND potatoes on the same day.

I have that li'l pot belly railroad stove, but still need flu pipe & other hardware.  BF regards it as "decor".
It's okay... See?  You're not the only ones who think I'm silly.
:) 

[Beeherder]

 
Where i live the woodstove is not an option. A cooking woodstove, now that's an option. My little closed box woodstove with the flat top will heat the entire house, first and second floor even when its on the second floor. Use it all the time to evaporate water througn a teakettle during those low humidity winter months. Have cooked on it when electric fails but its not a cookstove.

The wood pile is a perfect example of 3 is 2, 2 is 1, and 1 is none. If i don't have at least one more year of wood on the wood pile when burning season ends in April/May then i start gathering wood in May. When there is more than a year on the pile it waits until about now for me to strart the gather. So now I'll cut those long logs gathered for free as opportunity presented, to length and start the circular saw on those free pallets still left from last year, and add them to the now cleaned  up wood coral. I drive T posts with the correct spacing to slip pallets over the posts and hold upright. Place the semicicular wood coral on the down side of the slope about 5 feet below the ridge line, place more pallets on ground between the coral and the ridge. Fill the coral with cut, split wood before November 1. For now here's hope the neighbor with the 35 ton splitter remember how much he likes my bread.

Sorry if that's an of topic ramble.