Idea for offsetting solar/wind with grid power...
Idea for offsetting solar/wind with grid power...
(OP)
I'm an auto/mech engineer, and have only had a couple circuits classes, so please forgive me if I'm talking out of my you-know-what. But, easily-integrated 'green' power generation interests me, so here I am, trying to learn...
When a solar panel or wind turbine is added to a home, it's either:
A) Connected to the main supply, allowing all loads to feed off of it, and feeding any excess to the grid. It may have a battery bank between the generator and main.
B) Somewhat like a UPS. Charge a battery bank that feeds a few devices directly, then switches to main when bank dries up.
The idea:
Somewhat like B, only without the batteries. There would be a box that the load device(s) and generator would be plugged into, then the box would be plugged into a standard 110V wall outlet. 100% of the generated power would be used all the time, which would be supplemented by the wall outlet. So, for a 100W load, 10W may come from the solar panel and 90W from the wall, etc, etc.
So, my questions are:
1. Does anyone know of a company that builds such a device?
2. How would one go about building such a device? Is it as simple as just putting the supplies in parallel?
3. Or, is a better/simpler way just to invert the generated DC into AC and plug into a wall outlet? (I've heard this is a bad idea, but thought I'd throw it out there anyway)
When a solar panel or wind turbine is added to a home, it's either:
A) Connected to the main supply, allowing all loads to feed off of it, and feeding any excess to the grid. It may have a battery bank between the generator and main.
B) Somewhat like a UPS. Charge a battery bank that feeds a few devices directly, then switches to main when bank dries up.
The idea:
Somewhat like B, only without the batteries. There would be a box that the load device(s) and generator would be plugged into, then the box would be plugged into a standard 110V wall outlet. 100% of the generated power would be used all the time, which would be supplemented by the wall outlet. So, for a 100W load, 10W may come from the solar panel and 90W from the wall, etc, etc.
So, my questions are:
1. Does anyone know of a company that builds such a device?
2. How would one go about building such a device? Is it as simple as just putting the supplies in parallel?
3. Or, is a better/simpler way just to invert the generated DC into AC and plug into a wall outlet? (I've heard this is a bad idea, but thought I'd throw it out there anyway)





RE: Idea for offsetting solar/wind with grid power...
http://
RE: Idea for offsetting solar/wind with grid power...
RE: Idea for offsetting solar/wind with grid power...
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RE: Idea for offsetting solar/wind with grid power...
In my fan example, the box would be plugged-in between the fan and the wall. It will supply only the load device connected to it.
In A, the generator is connected before the breaker box and feeds the entire house.
The point would be to allow any normal joe to aquire this box, take it home, and plug it in himself, without the need for an electrician, just like a standard computer UPS. He'd only need to get whatever kind of generator he wants, be it a 500W turbine or a 10W solar panel, and plug it in.
In the link I posted, the guy is using a solar panel and an inverter and plugging the inverter directly into the wall socket... This would be ideal, but I'm curious about how the rest of the circuitry would handle it (breaker box, main supply, outlets, etc.)
RE: Idea for offsetting solar/wind with grid power...
The problem is, though, I can't find any inverters that are less than 1KW, or costing less than about $1900. From what I've read, this is due to UL requirements. There used to be one made by a Dutch company (the "OK4U") that was a 100W inverter and could be plugged directly into a wall socket, but due to the UL, it's not legal to sell in the US anymore. If anyone has a resource for a similar product, it'd be great.
This, though, is where the system I described is useful. It's not a grid-tied system, but uses the grid for supplemental power, if the generator can't provide enough. It can't supply a whole house, but could be used for big things like refrigerators and air conditioners, or multiple devices can be run off of power strips.
To put a number on it, say it will handle 500W of power from a combination of two sources, in any ratio of the two.
RE: Idea for offsetting solar/wind with grid power...
If you had a DC powered fan, you could theoretically convert your utility power to DC with a rectifier, then feed that DC into a DC isolator along with your PV source. They will truly share the load without back feeding into each other (that is of course what a grid connected PV system does). This is done on marine systems all the time. The caveat is however, you can't "tell" the load how much to draw from one source or the other, it is going to just try to draw whatever it needs. So if you try to draw more from the PV system than it is capable of delivering, it will overload. That's why in a grid connected PV system, you need to have a PV system capable of powering everything you want on that system.
To take your single load idea one more expensive step further however, you could do the DC route mentioned above, forgo the PV system inverter (since DC is what PV panels actually produce anyway), have a smaller inverter at the load so then you are back to being able to use an AC fan. But now your cost for one fan power system has become extreme.
RE: Idea for offsetting solar/wind with grid power...
It's a nice idea but I haven't seen anyone building solar or wind inverters that will work standalone without batteries.
RE: Idea for offsetting solar/wind with grid power...
I did a little more research this weekend and found that Tripplite (and probably others) makes a PDU/ATS with multiple AC inputs. In a sense, this is what I'm looking for. It has a primary and a secondary AC input, with the secondary as the backup. When the primary supply cannot supply enough power, it switches to the secondary. In my case, the primary would be the solar panel/generator. If the power from the panel drops, it'll switch to grid.
The only problem I see is this: If the load is 100W, but the panel is only outputting 20W, then it will switch to grid, and ignore the panel until it comes back up to 100w. Without some sort of battery to capture the power that isn't being used, it's just wasted.
So, at this point, it's not highly viable... My solutions end up being one the two existing mainstream solutions, or converting AC to DC, combining with DC, then converting back to AC, as jaref suggested (unless I'm running everying DC).
RE: Idea for offsetting solar/wind with grid power...
Had sun? Reduce your household consumption! Worked really, very well.
The power companies looked at this and I'm sure extrapolated to the extreme of every tom-dick-and-harry doing this and promptly pulled out their trump card "safety" and killed every maker of these devices, almost overnight.
It was really very unfortunate.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Idea for offsetting solar/wind with grid power...
I subscribe to my electric company's 'green generation' program, which costs me about an additional $10/month from the additional per-kWh cost, but at least they're required to give me my energy from a 'green' source.
RE: Idea for offsetting solar/wind with grid power...
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Idea for offsetting solar/wind with grid power...
The key is that the power flow from the grid tie is one way. The power company cannot say a thing about this. The box just allows the alt source to supply all it can to supplement the grid source.
It certainly is possible to build just such a thing for 1kw loads in the $1000 dollar range.
You need to stay away from grid tie inverters because the power companies will allways have a legitimate and convieneient disagreement with them.
But making devices that supply primarily from alt sources and then supplement with grid in a one way arrangement cannot be argued with by the power companies.
RE: Idea for offsetting solar/wind with grid power...
120V from grid rectified to HV DC bus.
Alt energy source is boosted to supply HV DC bus.
Inverter from HV DC bus to output sockets.
Incorporate a switchover mechanism to feedthrough grid
power directly bypassing the inverter when no significant
alt power has been available for some time limit.
Wheres my soldering iron?????
RE: Idea for offsetting solar/wind with grid power...
RE: Idea for offsetting solar/wind with grid power...
http://
but, they were selected by Costco to sell systems to Costco members:
http:
Anyway, about $30K, installed, along with direct hookup for net metering:
http://
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RE: Idea for offsetting solar/wind with grid power...
A real cheapo method,(that would violate the above premise), would be to just run the solar to an inverter that runs the Plugged In and if it becomes insufficient just switch via a relay. It could probably happen fast enough to not be noticed by most devices.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Idea for offsetting solar/wind with grid power...
high dc voltage input 100-200V
How about doing the switchover with zero crossing solid state relays. The switchover would occur as soon as the inverter and power line were in phase. Note there is no time limit on this operation so one could wait for the inverter to drift into phase then switch. I want to avoid the blinking lights problem.
RE: Idea for offsetting solar/wind with grid power...
Don't you think it would simpler to simply design the inverter to sync its output to anything that it's connected to?
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RE: Idea for offsetting solar/wind with grid power...
yes your probably right. However remember if the inverter actually output 59.9 hz it would sync up in about 10 seconds.
I doubt if production tolerances are very tight. But of course you could have the occasional perfect unit that actually had problems syncing.
To me this concept has enormous power to enable people to incorporate Alt energy on their own without red tape interference.
I think we engineers should start a sort of open source project with the design being public domain.
The goal is to create a box. Plug this into the household power then plug a subset of the household loads into the device and thereafter these household loads are incapable of
distinguishing the source of power and therefore the human users also cannot tell. Then attach whatever alt sources you can afford and this box will transfer the power when available and required.
The whole key to this is that it is imperceptable to the user and the utility cannot complain and it allows the substituting of alt energy for grid energy.
This is the missing link.
What do you guys think????
RE: Idea for offsetting solar/wind with grid power...
If the UPS and its load are large in relation to the alternate energy source most of the energy from the alternate source will be utilized.
Automotive type lead-acid batteries have some flexibility in the charging voltage. The two charging voltage levels will only allow grid charging when the alternate energy source is insufficient to carry the load.
This scheme should allow almost full utilization of the available alternate energy and avoid the safety issues inherent with feeding alternate energy directly into the grid mains.
You can probably go with an off the shelf UPS. Change out the batteries for larger lead acid batteries and adjust the maximum charging voltage. Disable the bypass mode or use logic to inhibit bypass when the alternate energy supply is above a set minimum level.
respectfully
RE: Idea for offsetting solar/wind with grid power...
If you tried to store all the generated power, you'd need a truckload of batteries, which is hardly economical nor exactly low maintenance.
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RE: Idea for offsetting solar/wind with grid power...
RE: Idea for offsetting solar/wind with grid power...
It does make very poor use of the potential of the alt source but in our current situation it seems like pain free (other than cost) systems don't exist.
If the loads were selected based on daytime usage maybe it could someday pay off. ( televisions, computers, refridgeration...)
Just think if one day some wise guy really makes solar panels cheaply then this would become much more attractive.
One possible usage is pre-heating the incoming water in a seperate tank before it reaches the main water heater. This would allow some energy storage and usefullness as hot water is a major draw of electrical energy.
RE: Idea for offsetting solar/wind with grid power...
What's wrong with net metering? You get to sell your electricity at premium rates and buy it back at a lower rate.
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RE: Idea for offsetting solar/wind with grid power...
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Idea for offsetting solar/wind with grid power...
http://www.kepco.org/news/netmetering.html
This should not be an allowable argument. How would they adress a person who gets most of his power from alt energy and then occcasionally buys some from the grid. They clearly cannot oppose this on some moral/legal ground. They can make a claim that they have fixed costs from providing the availability of power and they would be right to charge enough to keep suppply available.
If this argument is allowed to prevail it means there will be no independent power production because everyone has to buy their share in order to keep the infrastructure operating. In other words their monopoly is a neccessity.
Doesen't sound like the free market to me.
Oh I forgot that only applies when you loose your job or pay high prices at the pump.
RE: Idea for offsetting solar/wind with grid power...
To address another thing...
I use solar merely as an example. Obviously, it doen't work at night when most people are actually at home. But, during the heat of the day, it can offset the power needs of a refrigerator, window A/C, fans, pumps, etc. etc. Basically, all of the stuff that needs to run even when no one is home.
However, my thinking doesn't stop there. Since any dc supply can be easly plugged in, it will allow people to develop new, novel ways of generating electricity. For instance, I saw on Instructables.com that, as a school project, someone made a wind generator out of a Pringles can. It doesn't produce a lot of power, but they're really cheap to make, and a small farm of them on an outdoor balcony could be a decent contribution.
But there's also a lot of other things you could build... What about power generating exercise equipment? Or scavenging power from heat sinks? Or even mini water turbines on shower heads and faucets...? The ideas are endless, but there's no suitable way to implement all of these tiny ideas so that they can actually be of benefit past a science experiment.
That type of ingenuity, and the fact that to offset a little bit of power wouldn't take a lot of money in the DIY world, would really get this idea off the ground on a larger scale. Right now, to even get in the game takes a huge investment. With this 'box' you have a choice between the commercial panel/generator route, or the diy route.
One thing to remember is that this isn't supposed to be a whole-house system; each 'box' is only supposed to offset a few devices, or basically replace only a single wall outlet.
RE: Idea for offsetting solar/wind with grid power...
Note the page on the fight with the power company.
Where the poco makes its real intentions abundantly clear.
http://www.solarwarrior.com/
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Idea for offsetting solar/wind with grid power...
I agree that a "box" with this functionality would open up many opportunities for alt energy. However to make this thing power real loads with the necessary source transfer capability means it will not be cheap. Even the parts cost will be in the range of $200.00. I still think it is a worthwhile project.
Is there a web location for people to gather and pursue projects like this??
I am already working on a block diagram for how I imagine the device to function and will welcome all the eng-tips feedback I can get.
There could be a real market for this device given the fact that it allows alt energy to be utilized without all the usual problems. ( No financial payback, just satisfaction )
Lets get started
RE: Idea for offsetting solar/wind with grid power...
RE: Idea for offsetting solar/wind with grid power...
For starters a 40% energy loss! They have lousy charging efficiencies. Someone lays out $300 for a 40W panel and then from then on it acts like a 25W panel? Yuck. The need to replace the battery every few years.. Yuck. The system costs more. Yuck. The system is heavier. Yuck. Bulkier. Yuck.
I like the aforementioned suggestion of converting the Line power to DC feeding instead a (small)capacitor bank. Next an inverter stepping the solar power up to a slightly higher voltage also charging the capacitor bank. If the solar is available it trumps the line power. An inverter is fed from the capacitor bank.
The user would select a device that always runs or runs a lot during solar hours and plugs it into the inverter's output. This would effectively remove that device or some part of it from the daily utility charge realm without back feeding.
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Idea for offsetting solar/wind with grid power...
AC--->Rectifier--->|
|--->Capacitor--->Inverter--->Load
DC---------------->|
Or:
AC--->Rectifier--->|
|--->Inverter--->Load
DC--->Capacitor--->|
RE: Idea for offsetting solar/wind with grid power...
There's a lot of details that might also go into the Line to CapBank aspect. Another words not just rectifiers.
This is certainly a much higher tech project than a feed the power to the Grid job...
Keith Cress
Flamin Systems, Inc.- http://www.flaminsystems.com
RE: Idea for offsetting solar/wind with grid power...
htt
RE: Idea for offsetting solar/wind with grid power...
If you ripped out the battery, and plugged in your DC generator (with sufficient voltage control), you'd be all set. The only head-scratcher I see is, what happens if you have your DC generator connected and there is no load? It's unclear to me what happens to a wind or solar generator if no load is attached.... overvoltages might be a problem....
Seems to me the best way to start tinkering with this would be to go buy a cheap APC UPS. There's some available on ebay for $15-20.
RE: Idea for offsetting solar/wind with grid power...
I'd think you want a load that draws more power than the renewable source can provide. You use an AC-DC-AC inverter as the basis. Then, you add a DC-DC controller that pushes as much renewable energy as possible into the DC buss of this inverter. The DC buss of this inverter will simultaneously get the extra power it needs from the line. I think maybe this is what you were hinting at Keith in your description?
Switching between the two sources would be a waste of the potential capability of the RE in my opinion.
RE: Idea for offsetting solar/wind with grid power...
How bout a small Ni-Cad pack like used in Hybrid Cars.
It even comes complete with a marketing hype built in.
"Hybrid Solar Power System"
Let the investors form a line to the left.
I have to disagree with Lionel. My main concern is that the line supply system not waste so much power when the alt source is idle as to render the whold think a wash.
Switching to direct line power without processing it during down time is a necessity to avoid the (80-90)% maximum effeciency when the power is processed.
My implementation.
Power Transformer with three isolated 120 VAC windings chosed for effeciency. The AC main is switched into one winding by a relay controlled by the system. The alt source feeds an inverter that connects to winding 2. The output to the load comes from winding 3. This gives you the isolation for safety. When the alt source is available the relay opens the mains winding and supplies via the inverter winding.
The control system has to monitor the available alt energy and decide when it can switch as well as redundant safety measures to make sure the alt source doesn't feed the grid through the transformer. Also zero cross switching of the relay would be nice.
RE: Idea for offsetting solar/wind with grid power...
RE: Idea for offsetting solar/wind with grid power...
I'd be curious to see some preliminary data comparing the required RE source vs the possible savings achievable when suppling some typical house loads.
RE: Idea for offsetting solar/wind with grid power...
--> lots of available sunlight
late afternoon --> tons of household load
--> little or no sunlight.
Anything that doesn't involve net metering or some daytime industrial load is economically and environmentally a poor investment. Why incur the environment cost of a 5 kW solar panel, only to drive a measley few hundred watts of average household load during the day?
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RE: Idea for offsetting solar/wind with grid power...
Plus, the system is not supposed to be able to use 5kW supplies, or even 1kW supplies. In MOST situations, you're not going to pull near 1kW from a single outlet. It's supposed to use a 50-200W max alt. supply to supplement, NOT replace grid usage.
Also, it's not meant purely to be used with solar. It's supposed to be used with any dc source, 'alternative' or not. You can charge a battery in your car on your way home from work and plug it in if you wish. As long as it's 12V, it'll work. Wind, water, solar, even human powered generators can be used. It's not limited to just solar.
-----
With that said, yet again...
peebee- Yes, it basically is an online-UPS. I just didn't know they existed.
http://ww
So, in this setup, as long as the charger and alt. source would play nicely together, it should work. The battery would act as the 'balancer' of the alt. source and AC source.
The only problem is the efficiency of doing it this way. You'd have to bank on the alt. source making up for the inefficiency of converting the AC, and then some. Though, check out the description of the 'delta converter' in that link as well.
For example:
Consider a 100W load. Inverter/Converter efficiency is 80%. Alt. source is supplying 50W to inverter.
100W/0.8 = 125W needed going into the inverter.
125W-50W = 75W needed from converter.
75W/0.8 = 93.75W needed from AC Source.
So, based on this scenario, we end up saving 6.25W on a 50W alt. source supply. Not exactly ideal. Efficiency is going to be key. At 90% C/I efficiency, we save closer to 32W, which it in the ballpark of being viable.
RE: Idea for offsetting solar/wind with grid power...
I meant to add to my description a method for the grid to supplement the alt source that feeds the inverter. The control system would determine when to give up on alt power and use grid.
If people bought systems like this just as a hobby thing or a feel good greenie thing it could make a difference. The key is reliability and no wear out items (batteries).
Long after the glow wears off the system could be quietly doing its job of harvesting a few thousand watt-hours a day and causing its user no inconvienence.
Saving a bucket of coal or gallon of oil or milligram of nuke per day.
RE: Idea for offsetting solar/wind with grid power...
RE: Idea for offsetting solar/wind with grid power...
I don't have process recipes for solar cells, but if you assume 5 hrs of diffusion furnace time per lot of wafers, 100 wafers/lot and 1700 wafer total to get 7 m^2 of yielded solar panel, at 50 kW furnace power, you'd consume 4317 kWh in the manufacturing of the solar cells.
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RE: Idea for offsetting solar/wind with grid power...
You would need an on-line and off-line mode. The UPS would run on-line only when there was enough RE available to make it save evergy vs just using line power. Sure, your numbers show that a 90% inverter section would work but only when you have 50W of RE available....what about when the RE available drops to 20W?
Put a 100W "RE Box" by your entertainment system and it would save the standby power for the TV, AV receiver, cable box and DVD player. So, you save say 20 watts = probably about 5kWh a month....this would be a waste of the 250W solar panel needed to make full use of the 100W "RE Box" when that equipment is on during the day.
The example of powering the fridge. Just what percentage of the time during the day does a fridge run? Say it's 1 hour during daylight hours. Then your 500W panel will only save you at most 0.5kWh a day....basically a waste of a 500W panel.
I'm not saying it's a bad idea but it would have to be properly applied. People just hap-hazardly slapping these boxes onto different loads without understanding the applciation will be a total failure and actually be the opposite of green power once manufacturing energy is accounted for. Might make for a warm-fuzzy good feeling but not much else.
Remember, you're calling this a plug-in UPS like box. So, it can't be powering different loads all over the house. It will only be powering the loads at one wall plug.
RE: Idea for offsetting solar/wind with grid power...
How bout this scenario.
Box powers Entertainment center and TV in a home where there is daytime occupation. Both stay on a good portion of the day and the alt power is utilized at 50%.
It would fall to the user to understand and apply the thing effeciently.
IRstuff
You used a panel area of 7 meters ^2. This seems a bit oversize for a 300W collector. Tell me if I am wrong.
What if it were scaled up so that a house essentially had two groups of outlets. One group would be used for really high demand items. (vacuum cleaner,microwave,hair dryer...) the other group would be used for low demand and releatively constant loads. (TV,computer,lighting...) and run through a power box of the sort we are discussing.
I realize net metering and using the grid as a storage is the most sensible and usefull thing to do. However the utilities are never going to allow this on a large scale. Unless there is government intervention to require them to make it easy. However this would be a infringement of the "free market concept" and a "government intervention" and as we are told every day this would bring on the collapse of society. So a solution to incorporating alt energy into household usage has be a "go it alone" type thing as there will be no help establishing a cooperative arrangement whereby sytems trade power. That is my angle of attack. I would like there to be a way to use alt energy without batteries as they are a source of major enviromental concern and the only way is for the system to power the loads and pull what is necessary to make up for the shortfall from the grid.
RE: Idea for offsetting solar/wind with grid power...
spdracer22
I wouldn't worry about circuit classes. If Engineering Economics wasn't required where you went to school I would find a class and take it.
The money for the system(s) your talking about would get a better return in several scheems. The money spent on a home solar array or windmill would have faster return on insulation upgrade, triple pane windows etc. A kilowatt that is never generated is just as good as one put back on the grid.
RE: Idea for offsetting solar/wind with grid power...
If there is a 20 year investment recoup time and a 12 year production energy recoup time, why even pursue solar on any scale in the first place? If we could solve all of our problems by replacing windows and upgrading insulation (which, by the way, can have many disadvantages, as well), why are there any efforts at all for alternative energy?
I, for one, don't use my AC except for on the hottest days in the middle of the summer when I'm actually inside, instead opting to open windows at night and closing and covering them during the day. So, cooling costs me effectively nil, except for the small window fan I use to circulate air into the house at night. I use natural gas to heat my home and water, which is effectively green anyway.
RE: Idea for offsetting solar/wind with grid power...
"the argument for this device is not to save money; it's to help save the environment..." that's a good ideal but in practice not many people want to spend their own disposable income to do it. They will pay higher utility bills ( because there always going up anyway), they will recycle pop cans etc.
I personally am not going to spend 2 or 3 grand on a system to save a KWH a day. That won't even pay the intrest on the loan.
RE: Idea for offsetting solar/wind with grid power...
Solar energy, without some sort of buffer, simply follows what you can get from the sun. The peak total radiant power from the sun is 1120 W/m^2 at the equator; at the peak temperature point of the day, it's less than half that value. Only 1/2 of that power is usable in a solar cell; the rest is ouside of the responsivity of the cell.
Now, you need to account for the conversion efficiency of the system, which will be around 15% net. That means that a square meter of panel will net you 42 W, under those conditions. Therefore, 7 m^2 will only net you 294 W in the afternoon. At the peak, you'd get double that, so about 600 W, but your A/C probably wouldn't even kick in until 5 pm or so, to cool the house down for when you get home.
And that's with the max solar constant day. You'd need even more area to account for a typical day, or a partially overcast day. Southern Cal, whil it gets lots of sun, the sky isn't really all that clear. Much of the junk in the air will reduce the surface solar energy.
As for why doing it at all, it's the realization that fossil fuels will run out within the next century. It'll probably take us 20 to 40 yrs to develop a really efficient solar panel. Current technology barely gets over 15% to 20%, which is then further reduced by the converter efficiency. With a variable, and light, load, the converter may get less than 70% efficiency.
It's taken more than 20 yrs to get solar cells up to the current level of efficiency. Without a majot breakthrough, we're pretty much topped on with the standard photovoltaic solar cell. That would be the argument for starting now. By using the current technology in places that can really take advantage of the minimal efficiency, we can potentially postpone the depletion of our other fuel sources, allowing us more time to develop a better technology, assuming that it's even possible.
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RE: Idea for offsetting solar/wind with grid power...
How much would it cost to put a corrigated aluminum roof over my existing roof? I would space the new roof about 4" over the existing roof. How much AC energy would it save?
My point is you use your limited resources to same the most energy the cheapest. For me and my limited budget a mini-solar/wind system ain't it.
RE: Idea for offsetting solar/wind with grid power...
I checked a spec for a panel
Evergreen solar PVEC115 dims (62.5 X 25.7) inches
This works out to 1.03 M^2
Its rated at 115 watts.
I know they fluff their numbers with ideal situations but shouldn't one expect at least 70% of this or 80 W.
Do you see a discrepancy here or maybe they fluff their numbers even more than I expect.
RE: Idea for offsetting solar/wind with grid power...
http://www.solardepot.com/pdf/EG_EC-100_120.pdf
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