# Is solar cost effective?



## SE18 (Feb 21, 2008)

I searched thru forum and mostly found solar related to lighting or something.

Yesterday, got a flyer from Harbor Freight, showing solar panels $169, reduced from nearly $300 (probably b/c no one is buying them?). Anyway, says you also need a 12v battery and something else, inverter? Said to put out 45 watts.

I have some water pumps used for my canals on my railroad and wanted to use solar to remove myself from the grid so that's my impetus.

Anyway, here's my questions (and I suppose there are many variables). It would be cool to hear from someone who actually uses solar.

Factors to consider.

What's the break even point? (cost of purchase minus cost savings)?

Should one perhaps wait until solar or battery technology improves before making a purchase?

Other variables might include sunlight (I get fun sun in afternoon in summer but almost none in winter, for solar to work, does actual sun rays need to hit the panels? My solar lights just need light to activate at night, not direct sun).

Will the HOA approve of panels; lots of them?

How should one shop for them? Buy the most expensive ones?

Your ideas appreciated.

Dave V


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## Dwayne (Jun 10, 2010)

My future home/cabin is going to be offgrid. In a nutshell you gather energy from the wind and sun, send it to a battery bank, feed it through an inverter for AC for power. The trick is to be frugal with your loads so as to not deplete the batteries. Solar panels and wind generators provide a trickle charge to the batteries. 

In the Kenworth I drive I run a 1500 watt inverter. Once I run down the truck batteries I have to crank the Cat engine to recharge the batteries. It all comes down to frugal energy management. Demand can't exceed supply.


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## kormsen (Oct 27, 2009)

the problem with all "alternative" energy systems is the storage of the energy. 
down here in (very) rural Paraguay, people use sunpower. but only where no powerlines can be laid for reasonable costs. 

if you want to have a system, that works when the powergrid goes down, buy a generator. 
if you are far away from the grid, sun- and/or windpower might be the right thing. 
experience tells, that sun paneels serve for about 20 years. good batteries for five years maximum. 

so, you might compare the price for the solar system, plus the price for four or five sets of batteries with the cost for 20 years of the amount of energy it could produce.


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## SE18 (Feb 21, 2008)

so it seems there are way too many variables (besides the ones I mentioned, those mentioned by kormsen, life of components purchased), to give a simple answer to the question on cost. 

I suppose if it were cost effective for the many variables, then everyone would be doing it and it would be a no-brainer. 

Seems it's not a zero-sum gain, which I suspected.


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## post oak and otter lake (Dec 27, 2007)

When I lived in El Paso [think desert] 25 years ago, solar power water heaters were being advertised everywhere. The estimated time to recover investment was 3 - 5 years. This was in an area of sunlight 360 days a year and some of the highest electric rates in Texas. I know solar component have been improved since then, but still recoup time is something to take into consideration. 

Roger


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## jgallaway81 (Jan 5, 2009)

Solar components have also dropped in construction costs drastically since they began to trickle into the civilian community.


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## SE18 (Feb 21, 2008)

Posted By jgallaway81 on 05 Aug 2010 11:45 AM 
Solar components have also dropped in construction costs drastically since they began to trickle into the civilian community. 
Since you mention civilian community, you are implying that the military has used them previous.

I just happen to have a 1957 photo from Popular Science, showing a solar-powered helmet used by the US Army to power its radios. Just thought you might like to see. Unfortunately, the technology doesn't seem to have advanced a whole lot since...


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## Chrisp (Jan 3, 2008)

Hello Dave - I think the main issue you'd have with solar for your canal/aquaduct system is adequate head/lift, which requires a lot of power and therefore larger panels and greater expense. You could try some of the small solar water circulators to prevent algae and help with local current flow - this would be a cheap experiment. 

Based on my experience with the solar panels on our house, you need enough sunlight to see a faint shadow to generate decent current. You would likely get circulation for your canals during daylight hours, just have a large enough collection pond to hold the water from the higher water features when the pump is off. Wintertime would freeze over or you could drain everything.


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## SE18 (Feb 21, 2008)

thanks; btw, now that I think of it, I do happen to have a solar powered floating fountain from Harbor Freight


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## SE18 (Feb 21, 2008)

http://www.harborfreight.com/floating-solar-fountain-pump-91962.html


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## takevin (Apr 25, 2010)

Why would say that, when your off the grid, you dont pay simple as that. Best thing to do is talk to several professional companies that do this type of work to get a better idea of what it takes.


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## ralphbrades (Jan 3, 2008)

I live at 57 deg north in the cold wet rainy UK.... I find that solar is *useful* -rather than being cost effective. I have a "summer house" where the lighting is powered by a solar cell array hung of a nail in the fence and it has a DAB radio with a solar cell fitted to it, (it replaced the wind up one). My wife would like a solar "water feature" to compliment her rockery -but I am sorry for obvious reasons I cannot tell you how noisy it is. There are also solar path lights for use in the evenings. In my case is it cost effective -I would say no. However the ease of simply sticking it in the ground or hanging it from a nail beats the irksomeness of having to rig up RCBDs and water proof cable glands et al to supply power to the garden. regards ralph


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## RimfireJim (Mar 25, 2009)

Posted By SE18 on 05 Aug 2010 05:55 AM 
What's the break even point? (cost of purchase minus cost savings)?

Should one perhaps wait until solar or battery technology improves before making a purchase?

Other variables might include sunlight (I get fun sun in afternoon in summer but almost none in winter, for solar to work, does actual sun rays need to hit the panels? My solar lights just need light to activate at night, not direct sun).

Will the HOA approve of panels; lots of them?

How should one shop for them? Buy the most expensive ones?

Your ideas appreciated.

Dave V 

In order of your questions:

1. Can't answer that one without knowing the cost ($/kW-hr) of your electricity, your expected usage, and the total cost of the solar power system.

2. Probably not going to be any significant improvements in the near future. How long are you willing to wait.

3. Power is proportional to the sine of the angle of the sun's rays to the panel. Sun perpendicular to panel (noon): sine of 90 degrees=1=max output. Sun at 45 degrees (9 am, 3 pm, approximately): sine of 45 degrees=.707=70% output, roughly speaking. More info can be found at U.S. Solar Radiation Resource Maps Are your existing lights solar powered, or just a solar sensor that turns them on and off?


4. Only your HOA can answer that one. Read your CC&Rs.

5. I have no idea, except that you can be very sure that anything from HF is going to be the absolute cheapest materials. There's only one reason they can sell a die grinder for $7.99.


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## jgallaway81 (Jan 5, 2009)

Posted By SE18 on 05 Aug 2010 12:54 PM 
Posted By jgallaway81 on 05 Aug 2010 11:45 AM 
Solar components have also dropped in construction costs drastically since they began to trickle into the civilian community. 
Since you mention civilian community, you are implying that the military has used them previous.


I actually was reffering to NASA's use of solar panels on the original SkyLab and several different satelites, as well as the Russians... I beleive their Soyuz capsule generated at least part of its onboard energy from photovoltaic panels.


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## Tom Bray (Jan 20, 2009)

Solar always seems to be an interesting option. I try to provide a short tutorial on what is involved. 

At work we have several systems that run off of solar power. A single panel, depending on its dimensions will put out between 45W and 120W when in direct sun. The system I designed uses 7.5W continuous (in round numbers: 550mA at 13.8 V). The panel we are using, which is smaller than I originally calculated we need, puts out 90W in full sunlight. The battery has a capacity of 104 AH. The system is supposed to survive up to 3 days without any usable sunlight over the lifespan of the battery. With the 90W panel, it is overkill here in the south, while up north it may not be quite adequate in some places. 

For this little system, you can figure between $500 to $750 for the panel, around $200 for a solar rated battery, and possibly another $200 for the electronics. You will have to put the battery and electronics in something if it is outside so figure another $100 for that. Solar systems scale fairly linearly, twice the capacity will require twice the panels and batteries, the electronics will also go up somewhat as the size increases. 

The panel needs to be mounted so it can see sunlight as much of the day as possible. Height isn't an issue but you want it high enough so you don't walk into it and animals can't walk on it - I would say at least 8 feet off the ground minimum. Normally it gets pointed south with around a 45 degree angle, depending on where you live (there are charts available for figuring this out - 45 degrees should be the worst case and is optimized for winter sun angles). Some solar panels may be damaged if they get partially covered with leaves or dramatic shadows. They also won't look through trees that have leaves on them (don't laugh, we had a customer install a system that way - worked great all winter, seemed to have a bit of a problem when spring arrived). 

Power usage is calculated based on watt hour or ampere hour. During the day whatever you use to power pumps and such while the sun is up won't be used to charge the battery. Also if it is cloudy, only a fraction of what the panel can generate will be available. So, with a 90W panel you have approximately 6.5A at 13.8V available when the panel is in full sun, it will be some fraction of that for hazy or cloud covered days. I use the 13.8V because less than that starts sharing power with the battery which will the set the output voltage. The panel will follow the output of the battery if it can't supply enough power to maintain the battery and power the load by itself. 

For reasonable battery life you should plan on only using 50% of its capacity under the worst case conditions. With 104AH that leaves you with around 50AH. If the panel can put out 6.5 AH, in the course of an 8 hours of usable sunlight (this is a very optimistic number), you can get 52AH of charge - pretty much matches the battery capacity. So if you could count on 8 hours of full sun, you could use around 50AH over the course of a 24 hour day and the battery will remain reasonably charged. That would give you approximately 2A continuous that you could use. If you can shut things down at night, that reduces the need for battery capacity. Lets say you decide that from 10:00 PM to 10:00 AM you shut down all the pumps and lights. That means that you would have 4A for every hour of operation. 

If you live somewhere like Seattle WA or Buffalo NY, you will only see a fraction of this capacity. There is a number called insolation which is the equivalent amount of sunlight a geographical area gets per day and is measured in hours of full sun. What it works out to is that over the course of 12 hours of potential sunlight, you see on average, the equivalent of so many hours of sunlight. You can find these charts on the web for various cities around the world. Note that if the number is 3 hours of insolation, that means that over 12 hours you will get the equivalent of 270WA out of your 90W panel for a particular day. Note also that this is an average number, you may get more or potentially a lot less for any period of time so you may need to be flexible on how you allocate power for everything. 

Each 90W to 120W panel is good for one battery. Adding another panel and battery will double your capacity. 

Note that the calculations I used in this are not necessarily what you would want to use to design a system. There are more variables that you need to take into account, climate plays a significant role, and how you calculate battery capacity may be different than how I did it. 

I hope this helps. 

Tom


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## SE18 (Feb 21, 2008)

thanks, all for your insights. I've got a really high roof and it has an extreme slope on it. The only place I can get full sun for most of the day would be about 30-40 feet up on that roof. Installing it might be problematic.


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## Chucks_Trains (Jan 2, 2008)

I was wondering what if you used wind & solar power combined? 

Say like a 12 volt windmill to help power some 12 volt batteries? 

Sun could also help charge some 12 batteries. 

Maybe also use a 12 volt pump for your rr needs? 

With a 12 volt solar/windmill battery setup could probably also power the layout if using track power and/or power a few light bulbs??..Just a thought.


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## Tom Bray (Jan 20, 2009)

My only concern with wind power is that the mechanical portion seems to be a continuous problem. I have only occasionally seen a wind turbine actually spinning, it just seems like they are always broken or disabled. 

Tom


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## tacfoley (Jan 3, 2008)

Posted By jgallaway81 on 07 Aug 2010 06:59 PM 
Posted By SE18 on 05 Aug 2010 12:54 PM 
Posted By jgallaway81 on 05 Aug 2010 11:45 AM 
Solar components have also dropped in construction costs drastically since they began to trickle into the civilian community. 
Since you mention civilian community, you are implying that the military has used them previous.


I actually was reffering to NASA's use of solar panels on the original SkyLab and several different satelites, as well as the Russians... I beleive their Soyuz capsule generated at least part of its onboard energy from photovoltaic panels. 

In space there is no atmospheric attenuation to reduce the effectiveness of the truly direct sunlight impinging on the solar panels. They are 'looking' directly at the solar radiation, not getting a fraction of it through an atmospheric soup that increases in density and refractive index the nearer you get to the surface. 
...and even so they still have Stirling engines as stand-by generators.

tac
www.ovgrs.org
Supporter of the Cape Meares Lighthouse Restoration Fund


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## RimfireJim (Mar 25, 2009)

Posted By Tom Bray on 09 Aug 2010 09:58 PM 
My only concern with wind power is that the mechanical portion seems to be a continuous problem. I have only occasionally seen a wind turbine actually spinning, it just seems like they are always broken or disabled. 

Tom 
If that were true, there would be a lot of dead cattle and sheep in the western rangelands! Wind-powered water wells (windmillls) have been used for decades for stock watering, and are still in use in some places, but not nearly as common as they once were.
I would say that most of the electrical wind turbines I see just west of Palm Springs, CA are turning when I pass through that area, which admittedly is not very often.


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## RimfireJim (Mar 25, 2009)

Here's an interesting article on some advances in solar cells: http://arstechnica.com/science/news/2010/08/new-solar-cell-uses-heat-to-beat-theoretical-limits.ars


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## SE18 (Feb 21, 2008)

Jim, 
Facinating. If great minds working on creating computer viruses were as enthusiastic about solar... 

I'm curious, after reading that article. If, says, that solar heat capture were located near sea water, say, along a desert coast, then the heat could also be used to heat sea water, creating steam power, which could be piped; could also create desalization; could help areas like s. calif & mideast 

Dave


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## John J (Dec 29, 2007)

I know of two people who are 100 % solar. I know one guy who built a cocrete house and burried it. 95 % of the house is under grond. He is 100 % solar. I know a lot of people who heat water using solar. WE in AZ are in a ideal spot for Solar. There is a large solar panel array near the Univeristy of AZ. They are buillding a large solar generating plant here in AZ but I fotgot where. 

JJ


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## Tom Bray (Jan 20, 2009)

I know that out west solar and wind power is a big deal. The climate and such make them cost effective and work well. Growing up and spending a major part of my adult life around the Great Lakes has meant that solar power is not very cost effective. I always thought that wind power would be a reasonable alternative but I haven't heard of it being cost effective in that region. 

Down here in Central Alabama, solar power seems to work pretty well, we get a lot of sun year round. The biggest issue is that in the summer the temperatures can get up there and that is hard on the batteries. I haven't seen very many modern windmills down here though, of course that doesn't mean there aren't any. There are a fair quantity of old unused windmill towers that have wells sitting under them though which I assumed were abandoned when electricity was made available at a reasonable cost. 

Taking into account where I live and have lived, solar and wind power doesn't have a payback that can be justified. If it costs $1500 to build a system that would allow me to run the water and the layout off the grid, it won't pay back that cost in electricity savings in a reasonable time. An extra cost that often isn't factored in is that the batteries will need to be replaced every 3 to 5 years to keep the system operating reasonably efficiently. For me, another significant issue is the environmental cost to build a solar panel and battery system in the first place and how long does it take for the system to pay back that cost. 

Tom


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## Mike Reilley (Jan 2, 2008)

There is another aspect of adding solar voltaic panels that needs to be understood....hooking it to your house IF you house also has power fed to it from the power grid. There's a LOT of expenses associated with doing that which are beyond the array, converters, and batteries. Here in San Diego you must also install a costly control system to protect the linemen that work the power lines. You can't have a roof top solar system pumping electricity into the grid (for which you get paid at the rate you pay for electricity...currently about 30 cents a KWH here in San Diego)...without a mechanism that shuts YOUR home system off from the power lines when they drop the load on the power lines to do maintenance. If you don't have this, your solar generated electricity can electrocute the linemen even if they have shut off their service to the lines.

The same kind of switch is needed when you add a generator to your house...cept here, in the case of solar power, it's far more sophisticated...and costly. Folks should look into the cost of this addition as I've heard with the permits and labor and equipment costs, it's half the total cost of a solar


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## JackM (Jul 29, 2008)

Just for fun I'll toss out the OTHER kind of solar engery - hot water. I can never remember what it's called. My house has a Solaron (brand name, long out of business) panel on the roof. It's about 4x 8 feet and is hardly noticeable on my house. Apparently it was installed sometime in the 70s - think Jimmy Carter era. Under the plastic panel is a sheet of black plastic (think Hefty bag), then a grid of plastic pipe. Fluid in the pipe warms in the sun and circulates thru a heat exchanger. An electric fan blows warmth into my livingroom.

Here in Western New York, I don't need it in summer, it's helpful in Spring and Fall, and would be more helpful in winter if we had more sun than we normally get. Unfortunately, the blower is pretty inaccessible, so I have no way of knowing whether running it costs more than what I save in being able to leave the gas furnace off while I'm at work. On a reasonably sunny day, it'll run (off and on) from about 9 AM to 4 PM.

I suppose it's cost effective for me, since it came with the house. Wish I could put an ammeter on the blower and do some calculatin'. I've often thought it'd be great to get one of those photovoltaic panels up there to power the fan and have a self-supporting system.

JackM


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## wchasr (Jan 2, 2008)

Jack, 
That sounds like the best idea yet! That type of system would not be too tough to rig now with the proliferation of swimming pool solar panels liek what you describe. 

Chas


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## lownote (Jan 3, 2008)

Being a historian, solar gets me thinking about Edison vs Tesla. Edison wanted to use DC. Tesla argued for AC. AC won out largely because it can be transmitted long distances without major losses, and we developed a power grid that favors large central plants and miles of wires. If DC had won out we might have had a model of individual home generators. Just as every house in the cooler parts of the US has a furnace, so every house might have a generator, powered by oil or coal or gas. 

Right now we have AC coming into the house, and most of the stuff we use has to convert it to DC. Solar panels have to have a DC to AC converter, then your household appliances convert it back to DC. How much efficiency gets lost in that process? I wonder every time I feel how warm power supplies and wall warts get. If Edison had won out over Tesla...


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## JEFF RUNGE (Jan 2, 2008)

Lownote, I think you can make a rough estimate of efficiency by measuring watts in vs watts out.


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## rmcintir (Apr 24, 2009)

It is interesting that diesel locomotives have used DC traction motors until fairly recently. With better control electronics, AC motor drives are an excellent choice for their adhesion characteristics and number of units required. AC locomotives are more expensive but isn't that the case with all newer technologies?

So back on topic (?), in many locations the major electrical draw is from motors, yes I'm more familiar with Florida. While the rest of the country heats itself with gas or even coal, perhaps oil even?!?, FL does it with heat pumps which are powered by motors (AC motors). Yes, some people have heat strips but they are dropping off as they install high efficiency HVAC systems. The same goes of course for summer cooling. It is interesting that significant power consumption in FL also comes from water heaters and pool pumps. With improvements in motor efficiency (AC) these two have improved. Wait you say, water heaters? New technologies actually allow high efficiency heat pump technology to heat your water, while also cooling your house or perhaps your garage in some cases (I'm going to do this). OK, my water heater might suck a bit in the winter months but it certainly isn't any worse than what I have already, resistance heat year round, plus I'm cooling my garage in the summer, big plus for "guy" projects in the man cave. BTW, solar water heaters in the winter really have problems at critical times (morning), even in FL.


So, while Edison and Tesla had a falling out and Edison didn't recognize (or rather benefit) from the efficiencies of AC power distribution, WE continue to do so. I do agree that the technology curve for some mobile uses of small power generation have serious benefits to go with DC right now, (G scale trains







, and maybe cars) but I think we have been WAY ahead of the game having benefited from Tesla's wonderful invention of AC power distribution, and on a side note radio control (c1898). I am very grateful that Tesla's AC distribution won out over DC. Centralized power it seems is what everyone wants today but really went against the grain at the turn of the century (in more ways than one).


I'm all for independence from any centralized, controlling force but the AC vs DC decision was capitalism at its best. Sadly, Tesla gave up his AC patent royalties to Westinghouse to keep the company alive and ended his days in relative poverty. 



Now we have the ability to create distributed AC generation using inverters. Power where it is used, not centralized! As things improve the inverters used to match power phase with the grid will become less expensive and have a life expectancy greater than 10-15 years. Yes the solar panels may last 20-25 years but expect to spend quite a bit of money on a new inverter before that. Competition drives down costs and promotes efficiency and hopefully reliability. I hope we all see this again, even if we don't always recognize it.

I'm planning on using the Florida sun to power my locos (harborfreight) and a few other things soon. Who knows, maybe I'll even contribute to the smart grid soon!


russ

p.s. The most efficient measures are those where you turn off the power to things you're not using, like wall warts just sitting plugged in.


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