Solar Power From Home Curtains

kaliann writes "With the push for more sustainable energy, easy DIY kits for alternative energy sources are likely to become quite popular in the coming years. We may see some big improvements in our ability to 'green up' if these photovoltaic curtains become widely available."

But they only produce power--

they only produce power when the curtains are closed.

Re:But they only produce power--

they only produce power when the curtains are closed.

Right... Right, like you're sitting there posting your comments on Slashdot wiht all the curtains drawn.

Re:But they only produce power--

It also allows you to simultaneously read slashdot and jack off to pornography without the neighbors and mailman peeking in.

Re:But they only produce power--

I don't see the problem. During the summer, the curtains should be closed to block out some of the heat from the sun. During the winter, allowing the sun to heat your home is a more efficient use of that energy anyway.

Re:But they only produce power--

Exactly.

Combine this with either solar hot water heater on our roof, or even more photovoltaic cells, possibly a 2 kw wind turbine and suddenly 50% of you average home power is being used by green energy.

The coming energy crisis isn't going to be solved by any one thing, but dozens of small sub systems that work together. they don't have to be massive farms or fields either. just 30-50% of your home electricity is enough to offset the demand.

Serious flaw

Actually I think they will save more power with the curtains open than closed.

I'm shooting from the hip here but looking at the picture I expect there's a serious flaw here. The Curtains look black so they are absorbing a lot of light energy. We know they are highly inefficient. So they mainly heat your house.

SO in summer time you will pay more in cooling costs than you gain in electricity. Either that or be warmer. Logically you want the drapes outside where they would be amiently cooled.

Now if you draw the blinds and thus it gets darker and you need to turn on a light well. So much for any gains.

Finally most houses are designed to have their windows shaded more or have an oblique incidence in summer time. Thus during the time of maximum sun, and warmth you get the least electricity.

In winter time when the solar flux is less and there will be fewer hours of daylight the direction of incidence will be better. But chances are you'd like the light.

The drapes have no thermal mass so they act like the worst kind of traum wall where they heat up and cool down quickly. No thermal damping.

Seems like archecturally this is a bad idea from the get go regardless of how the solar fabric technology improves. Maybe in northern canada or something it makes sense.

Re:Serious flaw

This is a non-issue. When I was in Spain over a couple of summers, most houses had black-out shades, and many of them were dark in color. Few Spanish houses had AC, so everyone just draws their shades during the day while they are at work, but also during siesta (think nap time). You'd be amazed how much cooler it was with the shades down than with the shades up.

That said, I realize that in the US we don't have siesta, but we do have a ton of work-aholics who don't spend much time at home during the day. I would be more concerned with the reflection from the glass diminishing the efficiency of the curtains. Perhaps putting them on the roof *would* be a good idea.

Re:Cooling the Roof.

Study some heat transfer principles. Depending on their reflectivity, these curtains may cause the roof to absorb MORE heat than the roofing does.

Ideally, solar installations for home use will not transfer heat directly into the house. A curtain laying directly on the roofing surface will absorb some light and create some electricity. However, light and heat that is not reflected will absorb and the greater part will transfer through to the house a large amount of heat. A smaller portion will radiate from the house.

Solar panels are typicaly elevated above the house. The air gap allows the panels to be cooled by airflow.

The actual news here is that they can create solar fabric. I'm sure they can design a roofing system that will use the material to generate electricity while the system maintains an air and water seal and reflectivity of the largest part of the sun's energy.

I have only one question...

Does the carpet match the drapes?

I doubt it...

With the push for more sustainable energy, easy DIY kits for alternative energy sources are likely to become quite popular in the coming years.

Two words. Doubt it. There are all kinds of ways to save money, but most people don't do them. To put it into a computer perspective, how many people do you know upgrade RAM? Out of that many how many do them themselves? How many people upgrade a CPU? How many people salvage CD-ROM drives from old computers? How many save old cases and build computers in them? Very few I would think. Same thing with these, they are a way to save money, but for most people they will just complain about high oil prices, try to get a raise, petition for an increase in minimum wage, repeat. These will be about as popular as running BSD on your toaster. You can do it, it might be cool, but most people don't see the need.

Re:I doubt it...

1) I've replaced all my bulbs with compact florescents.

2) I've replaced all the bulbs at both my parents' houses with compact florescents.

3) I've put smart strip outlets on my entertainment center in the living room, and the tv/dvd/roku box in the bedroom so everything is only on when the TV is on.

4) I've replaced desktops in the house with laptops (big energy saver there)

5) My favorite: I converted an old diesel generator to run on biodiesel/waste vegetable oil/etc. It's set to run in the morning about 30 minutes before I get up. It's coolant runs through a heat exchanger to preheat my water to about 100-120 degrees for the shower (in the event it's not running, a tankless hot water heater does the work). The power is fed back into my utility.

Some of us are trying the best we can =)

Re:I doubt it...

One other thing -- how come I've never seen, anywhere, the idea of putting a hydroelectric turbine in a sewer line?

I once worked in a office full of civil engineers so perhaps I can answer that question, here goes...

There is one point that should be understand right off the bat and that is that any time a generator is introduced into a system where current, water, sewage, or energy flows freely a load is induced upon the system and the total energy outflow is reduced (i.e. the velocity of the outflow is slowed by the generator as the generator converts that energy into electricity or perhaps a water wheel is turned in which case some of the energy of the outflow is being converted directly into mechanical work). I realize that this is a very rough description of the physics, but would the thermodynamics geeks please cut me some slack? Thanks.

Now, the typical sewer lateral (the pipe from your home or building to the main in the street) has an average fall of 1/2 percent over the distance that it travels to the main or just enough to ensure that the raw sewage makes it all the way to the main without backing up in your lateral. It might be possible to introduce some sort of turbine in there but there several problems:

1) Raw sewage tends to be sludgy with lots of trash, hair, and other assorted junk that is just perfect for chocking or clogging your turbine (this might be less of a problem if you are only talking about the outflow from your home, but it is still an issue).

2) As previously mentioned there is barely enough fall to ensure that the sewage makes it all the way to the main without obstructions (and the turbine is an obstruction) so any back pressure will back up your sewage.

3) Digging a ditch for your lateral with greater average fall is possible but the main sewer line is only so much deeper than the street surface so practically speaking how much extra slope could you fit into the distance between your home and the street? Probably not enough to increase velocity substantially and thus not enough extra energy to convert to electricity with a turbine.

4) Greater slopes mean higher velocities and ultimately higher pressures and higher pressure pipes and turbines are always more expensive (just ask the guys who run oil and natural gas pipelines). In fact, they used to hydraulically mine [wikipedia.org] gold in California using pressurized jets of water at lethal force from slopping troughs over long distances into ever narrower pipes fed from upstream rivers and streams.

To sum up: There is not enough useful energy to extract from your out flowing sewage over the distance from your home or building to the sewer line in the street to make the generator worth a crap (pun intended), it would probably just back up your sewage lateral and even if you had a very large property there probably isn't enough difference in slope between your toilet and the street to build up enough energy to make it worthwhile unless you have a very large property and your house is built on top of a hill our mountain. There is also the problem that toilet flushes are very sporadic in most residential situations so even more energy will be lost to spinning up the turbine on each flush as opposed to keeping a spinning turbine going. Basically, in most cases it just wouldn't be worth it.

Two ways to look at this...

Summer months in the Desert: Closing drapes helps keep heat out, solar technology helps to power the Air Conditioner.

Non-summer months everywhere else: Close the curtains to power the lights that you need because the curtains are closed.

Call me when it's cheap

The killer app for renewable energy will be to get the cost down.

Once it makes economic sense for me to go green, I will, but in the mean time much as I want to save the planet and everything I have bills to pay :-(

Great

Now I just have to block out the sun to get light in my room.

If only there was an easier way...

I don't buy that we have a land shortage.

I know we're at a point where solar is looking like a good investment. Still... Isn't it easier for a solar contractor to just make large solar power plants to supplement the grid than worrying about the specifics of installing home to home?

I'm all for the day when I can offset my electricity bills a small amount because I have my house decked out in solar material... I'd rather just have cheaper electricity though especially in the near future. Plugin, hybrid cars are going to start sucking on the power grid. If we don't add more solar or nuclear plants to the grid, we could see an electric shortage in the form of higher prices for one.

Oh and I'm still bummed about the study the government is doing to make sure solar is environmentally friendly. I mean, isn't the waste output from coal plants harmful to the environment? If we had the option to cut that waste back, aren't we helping the environment?

Anyway, the future looks bright to me. The US economy is holding even though it has taken some hits. If we can just get to a new era in surplus solar energy, we can get into some really interesting solutions to getting off oil. Some people think it will be hydrogen. Some people think it will be electric cars. I'm not sure which is going to take off in the long run. I think it is going to be hybrids that make the most initial impact because they don't have the limitations of the electric car's maximum range. For electric cars to have a long range, gas stations will have to be refitted with a tool to swap out battery arrays. Hydrogen faces a similar challenge in that it'd need special fill up stations too. Plug in hybrids work off traditional gas stations.

I like Nanosolar's approach because it is so high tech and also economically feasable. Still low tech solar options such as parabolic mirrors to focus sunlight and run steam turbines could be good at first. I think we have a lot of unused land on Earth, and the faster we can cover it, the faster we can have surplus energy. Surplus energy makes transportation costs go down so you can travel all that you want even if you're poor. And even more interesting is that surplus energy lowers the cost of transporting food, so impoverished people can be supplied better. Oh yeah, and surplus energy also means that everything is cheaper so people have more disposable income which incidentally, also helps poor people.

Re:I don't buy that we have a land shortage.

I think we have a lot of unused land on Earth, and the faster we can cover it, the faster we can have surplus energy.

Great attitude. I am no environmentalist or anything, but even I realize that humans have already had a HUGE impact on Earth. The Fish and Wildlife Service [fws.gov] reports 1238 endangered species in the US alone.

I agree that solar power is great, but how about we try to use existing surfaces such as high rise buildings, as someone else mentioned. How about those hybrids use solar car sun shades to charge the battery while your at work? I think a little thought would be better than just sucking the earth dry.

Worthless article

Unless they post the watts/hr it can produce under normal conditions. Its like seeing a car in a car lot without a price on it... You just keep on rollin. Seeing this 'form of energy coolness' seems worthless without some type of qualitative evidence. I want to see the watts/curtain/hr.

Don't you think...

Does anyone else think it strange that we use power-consuming devices to illuminate the interior of our houses and other buildings when we built them with a large covering over the top that blocks out the daylight by design? Seems it might, just possibly, be a bit more practical to design them so we don't block out the light in the first place. We westerners consider ourselves "high tech". Ha! An advanced technology would use daylight directly during the day and store the excess for use at night.

Re:Hey.

Actually, RMIT (a tertiary institution here in Australia) recently announced that one of their new buildings will be solar-powered thanks to the glass on the buildings [news.com.au]. From the article: blah blah blah "with an outer skin of 16,000 sand blasted glass cells, some of which will be photovoltaic solar power collectors to help shade and power the building."

Re:Hey.

The panels turn transparent when they come in contact with water [rmit.edu.au], so it's mainly for when it's raining (I suppose there are other, far less peaceful circumstances in which water can hit them). Otherwise they're translucent.

Re:Hey.

I have to admit, solar shutters make more sense.

This wouldn't be bad as a DIY project for a sun-facing wall that gets too much light, though. Or a porch, to power the porch lights (like a solar lantern, but bigger).

Obviously not the solution for everyone. I, for one, have a tree to the south, which would likely displease the new solar curtain overlords.

What would be a cool application for solar fabric is a canopy (say, for an outdoor market). That could provide shade while powering lights or electronics (like cash machines) in the stalls. Or self-lighting party tents.

Re:Hey.

Why curtains?

1. Because most people already have windows in their living space, and
   
2. use curtains or blinds to block them at certain times.
   
3. Curtains wouldn't require any extra installation hardware if the existing rod is strong enough,
   
4. They wont make the outside of your house look ugly.
   
5. They would be more portable than a solar panel installation on the roof.
   

Is that enough?

Why not something that's, you know, outside where the sun can get it.

And hail, errant footballs, vandals...

Glass blocks light, light that can't be seen.

They still let in plenty of light than can be used for generating solar power according to my calculator.

Re:roofing shingles or roofing tiles

As with seemingly everything, it's already been done [google.com].

Unisolar has been making these shingles [altersystems.com] for years. Maybe others are too now. I don't know much about them, just read about em online.

-Matt

Re:Oh, the myth of Solar.

Nasch already took care of some of your illogical arguments... but you've made other assumptions that are just plain wrong or at best outdated.

20% efficiency on a solar panel is not uncommon. In fact, you can buy 28% efficient solar panels (as long as you don't live in the US *grumble*). Over their lifetime, of course that rate is going to fall, but it will still remain a bit above 20%.

Given time, that efficiency is only going to improve. Both of these factors right there shoot your 600M^2 theory to shit.

Using you and your family as an example, your average 1.4KW usage could be dramatically reduced without impacting your quality of life in an appreciable manner. I know this is so because I've done it myself. It takes some will power and awareness of what power you are actually using, but it can be done fairly painlessly. You can start by replacing your incandescent bulbs with CFL or better yet with LEDs. One of the largest single power draw in a home is from all the light bulbs. Reducing that can cut your monthly average quite a bit.

You need to turn off stuff you aren't using. Putting things into standby is not turning them off... in fact, many appliances and electronic gadgets don't even HAVE an off switch, they go into standby. So that means you have to unplug them. That's a pain in the ass. However, a simple solution to this is to plug everything you use for a particular activity into a power strip... when you're done, turn the power strip off. This overcomes the leeching power used by wall-warts, as well as gadgets and electronics that go into standby mode. Yes, you may have to wait a few seconds longer for something to power up, but it's not a huge deal.

Another big energy saver is to replace your windows. If you have contractor grade windows in your house, you are leaking energy like a sieve. Replacing your windows with high quality double or triple paned, krypton filled windows with insulated frames will save you a TON of money and energy for cooling and heating.

Do you have an ancient refrigerator? If so, it's probably drawing 2 to 3 times the amount of energy a modern refrigerator uses (or more if it's REALLY old). Might be worth it to replace it.

Do you leave your computer on at night? Turn it off, or at least put it in standby. My system, at idle, draws about 600w, when it's in standby it drops to about 30w. That's a HUGE savings on a month or yearly basis. If you're on Slashdot, chances are you've got multiple computers - I think you see where that's going. If you're using an old computer as a Linux router or something we are all fond of doing - stop. Old computers are incredible power hogs. A cheap wireless router that you can load new firmware onto will suck a fraction of the power, produce a fraction of the heat and noise. It's nice to think you're recycling your computers, but it's costing you more than they are worth in power per year, for sure.

There's lots of things you can do to reduce your power consumption. You can take your 1.4kw to 800kw fairly easily I suspect. That almost halves your 600M^2, coupled with the fact that you can buy efficient PV panels, now you only need about 200M^2. The average house has that much roof space that's likely suitable.

Even if you don't, as long as you are offsetting some of your power needs, it goes a long way to helping bring about a more energy efficient future.

Is it going to be uncomfortable? Probably a bit, but not cripplingly so, and once the "new" way sets in, it will seem silly that we didn't do it a long time ago.