Could heliotubes turn any surface into a solar power station–yes
Think of all the small, free-standing structures you see in a given day. Bus stops, small sheds, fixed awnings. They are put there to keep sun (yes and rain, I know) off people. What about the roofs of those structures? Looks like there could be a product that will let us take advantage of a lot of small surfaces and use them as solar collectors:
Soliant’s primary customer is commercial building owners but the company’s product design is flexible enough that it has developed a specialized solar-power generator for car parks, or roofs that shade cars during the day.
“One thing we realized about a year ago was that we could make very large panels, which is something that ordinary solar panels can’t do,” said company CEO Brad Hines.
The company’s traditional “heliotube” concentrator, which is meant to be the same size as traditional solar panels, has 10 tubes that shine light onto solar cells.
To make a product to shade cars it used the same basic design, but by stringing together 16 tubes, Soliant makes the panel a little over 8 feet long, said Hines. The company is planning to ship its commercial products by the end of this year. Source: Solar power while you park the car | Tech news blog - CNET News.com
I know I’m sounding like a broken record here, but it’s these kinds of simple innovations that can add up to the big stuff. Heck I saw one today on GearLive’s unboxing–instead of having a screensaver come on after five minutes, just have the screen turn off then. Simple, easy and will save a lot of power … a lot.
Let’s just brainstorm and think of more things … like what about micro-hydropower generators in downspouts? Out here when it rains, it rains. Why not use the power of the water going down the drain pipe generate a little power. If nothing else they could charge batteries to power outside lights.
Together I know we can work through this.
August 2nd, 2007 at 11:41 am
Interesting thought. Let’s work the numbers (Ohoh, why is it that that always causes problems?).
We’ll assume a one acre [1] area, and 3 inches of rain per day [2].
[1] Yes, I’m an American and we still use these crazy units. But, quite a few housing lots here are still sized in acres or a fraction there of (e.g., 1/2 acre, 1/4 acre, etc.). And, I know that a typical house won’t occupy the entire lot. A house is typically only a small fraction of the lot, but we’ll still use 1 acre, since it provides a reasonable upper bound.[/1]
[2] I’m definitely over-estimating the amount of rain, probably by well over an order of magnitude, even for the Vancouver/Seattle area, but we’ll use this as a reasonable upper bound, too.[/2]
Ok, let’s find out how much water is actually involved. One acre is defined as an area of 66 feet wide by 660 feet long [3], which gives an area of 43,560 square feet. With three inches of rain falling on this area, we come up with a volume of water of 10,890 cubic feet. Translating this into metric, we arrive at a volume of 308.4E6 cubic centimeters (about 308.4 cubic meters). Since the density of water is approximately 1 gram per cubic centimeter, this gives a mass of water of 308.4E6 grams, or 308,400 kg (about 678,480 pounds [5]). That’s a lot of water!
[3] An acre was based on how much a farmer could reasonably plow in a day with a good ox.[/3]
[5] This passes the sanity test, since I remember that water weighs about 64 pounds per cubic foot, so 10,000 cubic feet of water should be about 640,000 pounds.[/5]
Now, we’ll assume the gutters on the house are about 10 feet off of the ground [4], which is a little over 3 meters.
[4] This should be a reasonable value, although two story (and higher) houses will have a greater height.
Now, since energy is force times distance (well, the integral of it, if you want to be technical), and since force is mass times acceleration (of gravity), this means that energy is mass times distance times the acceleration of gravity (We’ll assume that gravity is constant over such a relatively small vertical distance, although if the distance was much greater, we’d have to take in the fact that gravity varies inversely as the square of the distance). So, plugging into E=msa, we find that the energy is:
(308,000 kg)(3 meters)(9.8 m/s**2)=
9E6 J
Now, 9 million Joules sounds like a lot of energy.
And, in most cases it would be. But, to get a better feel for it, let’s convert it into power.
Since power equals energy divided by time:
P=E/t=(9.E6 J)/(1 day)(24 hours/day)(3600 seconds/hour)=
104 Joules/second=104 Watts
So, all of that 3 inches of rain per day, falling on that huge house roof, with an area of one acre, and dropping a distance of 10 feet will produce an average power of 104 Watts (ignoring losses, which are sure to be rather significant!).
Hmm, you know, we could save more power than that just by turning off two lights that we don’t really need.
Dave
August 3rd, 2007 at 7:37 am
Oh well … it was an interesting line of thinking.