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hewhocaves
2005-Mar-23, 07:09 PM
So I've been thinking about solar power and the problem of getting enough photovoltaic cells on your roof to power your house without worry. I read somewhere that a roof can supply something between 75 and 100 percent of your power dependign on your efficiency and use. Obviously, you'd ideally want to produce something like 125% - 150% of average use, cause you're going to have cloudy days, winter, etc... and you want a little backup. So with current tech, it looks like you would need to toss cells somewhere else in your yard.

Of course you could fill your front yard with cells as well, but the wife might be upset if you dig up the roses.

An interesting place to put cells, i think, would be where you put your feet - i.e . sidewalks. think of all the miles and miles of sidewalks in a small town and how much of the day they spend jsut reflecting sunlight back up. Talk about waster space!

Obviously a PV cell would have to be more rugged if you were to walk on it (and push carts, wagons, etc...), but that strikes me as an engineering problem, rather than a technology problem.

And think of some of the other places you could toss cells. the grassy centers of interstate highways for example.

Any thoughts, suggestions?

John

Nicolas
2005-Mar-23, 07:13 PM
Problems with sidewalks:
*A thick glass protection layer reduces efficiency.
*Dirt reduces efficiency
*shadows of houses
*unreliable amount of sunlight: people walking over them, cars parked on them, cafés placing chairs and tables on them...

The grassy centers of highways would be a better choice. You'd have to take care that drivers aren't blinded though. As this is further away from houses, you'd have some minor transport losses.

Just some quick thoughts.

hewhocaves
2005-Mar-23, 07:37 PM
all good points.

I was thinking of a grate more than glass for strength, but I don't know which way the tradeoff might be best. Regardless, yes, you are still going to lose efficiency.

*I'm not sure how much dirt will play into it (dust, etc...) how much does it affect panels in the southwest? I do agree that you would want to sweep the walk reguarly (maybe even vaccuum it or hose it down)

*the shadow problem doesn't bother me too much because a) im thinking as a suburb idea b) on new houses you could orient the walk and the house to minimize it and c) don't you have the same problems with the roof?. But yes, you would want to keep the sidewalk clear, not only from the house, but trees, etc...

*people, cars, etc... again thinking of the suburbs, have you seen the length of the driveways in some of these "McMansions"? Plus, these houses also have four and five car garages. As for people walking over them, don't you occasionally get bird shadows over roofs?

the blindness issue is probably the largest one. not just on roads, but people walking down the sidewalk. you would definately want to some up with something that doesn't blind yet still keeps a reasonable amount of light going through.
another problem would be slipping. slippery as glass is a pretty apt description. fixing that problem would prolly kill some efficiency.

John

Nicolas
2005-Mar-23, 08:23 PM
Some of the problems would indeed be solved in suburbs, but then why not put the panels on dedicated areas when there's enough place already?

Van Rijn
2005-Mar-23, 08:29 PM
So I've been thinking about solar power and the problem of getting enough photovoltaic cells on your roof to power your house without worry. I read somewhere that a roof can supply something between 75 and 100 percent of your power dependign on your efficiency and use. Obviously, you'd ideally want to produce something like 125% - 150% of average use, cause you're going to have cloudy days, winter, etc... and you want a little backup. So with current tech, it looks like you would need to toss cells somewhere else in your yard.


The key problem is cost. The cost of PV is many times that of conventional electricity. It isn't unusual to use tracking systems - things that look a bit like an artificial tree - to maximize power production. If the panels were cheap, you could start using them in other ways. But that isn't going to happen any time soon.

Then there is the question of where you live. You want places with more sunlight, and if you have snow you have to get the stuff off somehow. And solar is a low density energy source. If you only power lights and modest appliances, your roof, at sufficient expense, and if at the proper orientation, can handle the job. If you have an electric stove, oven, a good sized family, lots of audio video equipment, etc. the roof won't be enough unless you have one VERY large roof. Don't even think of heating your house this way. And then you either need to store the power or use the local grid for backup. As long as a modest number of people use solar, and if the law requires it, the power company will allow you to use them for backup at cost, but they would prefer to pay you wholesale rates for your electricity and sell you electricity at retail rates. If PV electricity becomes popular, the rules will change, and backup will cost more.