Small Scale Solar Arrays

This is a query for information regarding building a very small solar array for my home - something in the 100 - 200 Watt range ( I can't afford to go big right now ). Ideally, I would like something that would be scalable over time, but would be fine even with a fixed capacity system that could be used to offset a portion of my electrical bill.

My biggest challenge seems to be finding <font color="blue">a small intertie inverter in the 100 -200 watt range that won't cost me a few thousand bucks</font>. I could have sworn that they used to sell lower capacity SunnyBoy intertie inverters for a few hundred dollars a year or two ago - Now they seem to cost 10 times that amount. Did I miss the memo here or did the prices on these just balloon up to 10X their original cost during our past two trips around the Sun ?

Anyone have a line on a good source for small entry-level, affordable intertie inverters ? And any other advice that you'd care to offer on starting to build a home array.

Don't have an answer for the small inverter...

An alternative would be to power something directly that can use the energy (fish pond plus battery backup for night operation--if needed) or even take a regular inverter and make your own cutover switch (inverter up, relay engaged to power device, power lost, relay drops to AC line).

-Bill

Mednanu -

I believe the Sunnyboy's have been larger capacity for quite some time (with associated extra cost). I've personally never seen one in the hundreds-of-watts range. Doesn't really make sense for them to make 'em so small.

I agree with Bill here - find something to power directly. My choice would be to power a UPS-type deal for you computer. With 200W and judicious use of the power switch, your computer could be completely solar-powered. That's actually how I started. My computer has been solar-powered for about ten years now. If you use a laptop, you can really stretch the production of your panels. Just get some relatively cheap 12V lead-acid batteries and hook them parallel.

There's a few guys I know of in the south that live off grid. They manage to do OK with only a few hundred watts. Most of them use normal deep cycle storage batteries, and they have minimized their energy use. Small or no TV's, task lighting, skylights, laptops for PC,s etc.

Small installations are easier and cheaper if you are not trying to grid tie the system. You can get a 45 watt solar array from harbor freight for $300 including a charge controller. Add your inverter and battery and you have a small 'free energy' system at just under $7 per watt. You can download the manual at http://www.harborfreight.com/manuals/90000-90999/90599.pdf

You could enhance this setup with an automatic 6 amp battery charger. The charger would cut in when the voltage drops, essentially providing the input for the inverter during extended cloudy days.

I worked at a place with a full time online UPS. The battery bank was under constant charge, and was contantly feeding the inverter. No switching was needed in case of a power failure since it was always running off the batteries. The power was super clean.

The harbor freight unit is not really designed for full time use, but it might work out well for lighting a vacation cabin or a small out building.

Daniel

One thing to be very careful with solar panels and home made power systems is lighting. If you are in a lightning prone area I would prefer to power something outside (like a fish pond or garden path lights) rather than my home computer.

If you are good with electrical, you should be able to find and install the right lightning arresters, ground you system correctly and be pretty safe. If you are not comfortable with this level of do-it-yourself, you may find hiring an electrician a bit too expensive for a small system--if you don't have a friend that can help.

-Bill

Id check out www.homepower.com for ads, suppliers and advice.

Good how-to from 1996: http://www.rain.org/~philfear/how2solar.html

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BB said:...An alternative would be to power something directly that can use the energy....

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While that would make sense for most normal people, I fall into a somewhat different category. I'm such a miser that I've actually gotten my electric bill down to about $5 a month above the $8 monthly flat fee to simply have electricity connected to the house. And that's for a 1400+ square foot house !!! /ubbthreads/images/graemlins/ooo.gif No joke. Only problem is, when I turn the A/C on during these ugly California summers, that e-bill figure jumps to the price of a small car payment. That's actually what I'm hoping to start chipping away at bit by bit. I don't plan on staying in the house for more than another 5 or 6 years and given the huge windows in the house, I wouldn't likely be able to afford ( or recoup ) the investment of buying Pela windows in order to reduce cooling costs. So my thought was to start investing in a scalable Solar array that could reduce my current summer e-bills and be something I could take with me and install into my next abode when the time came.

Even if someone has a line on some plans or vendor for a small intertie kit, I would be more than comfortable making it myself. It's just with the new house payment I'm a little low on funds and couldn't outlay a $20k or even a $5k investment in solar right now. I might be able to squeeeeeze $1k out of my budget but couldn't do much more, hence my desire for a small, scalable system that I could add on to every year. Eventually, my goal is to be all solar & biodiesel powered, but I've got to do it in small enough steps to make it affordable & feasible for my budget.

I don't think that the power company will allow an intertie of a home made converter. They don't want to rely on your knowlege of electronics design and build to protect their workers.

Daniel

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gadget_lover said:I don't think that the power conmpany will allow an intertie of a home made converter.

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I'm sure they wouldn't want me to do so, but I don't think that they have the power ( no pun intended ) to regulate the electronics kit industry.

Besides, I'm <font color="blue">very well versed</font> with soldering large power handling devices, all the way down to near-microscopic surface mount components on computer logic boards. And <font color="blue">the whole reason I'm researching an intertie inverter</font> in the first place <font color="blue">is to protect the electrical Linemen from getting zapped</font>. I could have just as easily connected my existing inverter directly ( ie - Direct-Tie ) into my house's wiring w/o the power company ever knowing about it. But because I have a shred of ethics ( and a clue on how this stuff works ), I didn't want the 120v AC coming out of my inverter unexpectedly turning into 20kv out the other side of a residential transformer node during one of our rolling summer brown-outs. That would end up frying Linemen.....which is exactly why I'm inquiring about a good, small-scale intertie kit or over-the-shelf unit in the first place. /ubbthreads/images/graemlins/wink.gif

I was no impuning your skills, Mednanu, but you must admit the average person does not have your ability nor understanding.

In my state, there are lots of rules, laws, codes and ordinances that cover electric service. In my area of Calif, you'd be disconnected if the power company discovered an unauthorized intertie.

Daniel

Yeah, I didn't mean to sound terse there. I'm more annoyed at the litany of regulations that CA has on the books which end up causing so much red tape that they actually prevent a lot of progress and innovation from being made in several areas - It just pisses me off to no end ( it's really not meant toward you gadjet_lover ). So when I hear of some other agency that just might want to regulate me while I'm actually trying to follow the whole intent and spirit of the law.... I pretty much have a knee-jerk reflex to tell them to pucker up. /ubbthreads/images/graemlins/wink.gif

But I'm glad you brought up the point about it being dangerous to tie in electrical loads w/o a reliable intertie hook up. A lot of other people out there may not have known that direct-tying their generator or inverter into a home outlet ( especially during a power outage ) has the real possibility of killing an innocent Lineman. Definitely not a good thing to do. That's why I wish I could find or make an affordable intertie system.

Mednanu,

Sounds like you have pretty much nailed the concept of conserving energy (aka, being cheap). And I fear that any suggestions that I would make will be ones that you have already thought of and implemented when practical—but I will give it a shot.

If you don't have double pane windows, I would highly suggest them (or put film and Styrofoam in your windows during the cooling season) would be a big help--even if it just in one bedroom or family type room where you spend the most time.

Also, the standard thing of ceiling and wall insulation will help a bunch--and be relatively cheap if you do it yourself (doing one room at a time is a cheap way to learn--and redo your mistakes if needed).

Any other high-tech solutions such as using a battery bank (24 or 48 volts) and an inverter to power a small air 1-room sized conditioner is probably going to be a wash or a loss by the time you include the costs for the equipment and efficiency losses (assuming you use an AC Line to DC charger to supplement your initially small solar panels).

You could also try other more low-tech type solutions ranging from stones or water barrels in an insulated room/cellar and cool with cold outside air at night, and use that air to cool your house/room during the day, etc…

There are a whole range of solutions out there—I just don't really know what you can use for your home (or even where you live and what temperatures/humidity/etc. you are living with) and what you are willing to try. But insulating one, or a couple of rooms (including installing new windows)—if you can do it all yourself, would be a good place to start. Just double pane vinyl windows and ceiling insulation (with stucco walls) was enough to lower my west facing bedroom's day/evening temperatures by 10-20 degrees (under the outside temperatures—room would get hotter than outside on some days) Fahrenheit here just south of San Francisco (we usually only have 1-2 weeks of 100 degree weather and generally cool nights).

The great thing with installation was that this made the home more comfortable and cheaper to heat for the winter too.

-Bill

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BB said:... Just double pane vinyl windows and ceiling insulation (with stucco walls) was enough to lower my west facing bedroom's day/evening temperatures by 10-20 degrees

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Hmmmm, that's actually an interesting idea. I've been experimenting with a few clear films over the windows, but hadn't heard much about the vinyl window option just yet. Due to the way some of my larger 'picture' windows are recessed, I could probably even install an extra pane of vinyl on the inside of the house and make it an easy upgrade.

What did you pay per sq/ft on your vinyl windows, and did you cut them to size or need to custom order them ? That just might be a do-able suggestion.

Mednanu

I am not sure—but we may have a miss-understanding… The vinyl windows I am talking about are "Vinyl Framed Glass Window Units" and are usually used to completely replace the entire existing wood/aluminum/steel windows.

There are storm windows (in colder parts of the US—but not where I live) that can be added as an extra pane. I don't know if these are fitted to the exterior or as interior units—but you could probably get Lexan or Plexiglas sheets and build your own interior units (with approximately 1/2 to 3/4 inch air gap—don't go too large as air currents will start and you will loose more heat). You could also get reflective film from a hardware store and apply to the glass window and probably cut some solar gain/loss too.

Here is the information for replacement windows that I did on several of my homes and talked relatives into doing on theirs too.

I have tried several places but ended up at a Home Depot "PRO" store and bought good quality double hung windows because:
<ul type="square"> [*]Manufactures came and went with brands I have bought vinyl windows before--Picked Milgard+Home Depot as something that would be around for awhile for warrantee (breakage and moisture leaks are not uncommon problems).
[*]Good Pricing and OK service
[*]Got "Low E" glass for no extra charge—did not bother with Argon filled.
[*]Reasonable delivery charges.
[*]Automated computer configuration for each window (20 windows on my home)--tried other stores that did this manually and got different quotes and messed-up purchase orders for factory (approximately 4 week delivery, IIRC)
[*]Did it myself (one guy helping) and saved what seemed to be 1/2 the cost vs installed price
[*]Picked vinyl over aluminum framed—had an apartment with double pane aluminum and the tenet thought the windows were leaking because of so much condensation from humidity.
[*]Chose the Milgard brand because it had a "slopped sile adapter" (piece of aluminum angle) that filed the gap under the new window frame when installed in the old double hung window location.
[*]Paid their installer to measure the windows (and give an installation estimate) so that I could have an idea of how they sized the windows (but they may not give you the measurements—had to look over the shoulder of the counter guy to get the measurements (and I found a 2" error on one window made by the installer)…. So ALWAYS TRIPLE CHECK YOUR MEASUREMENTS—you will be responsible for any errors.
[/list]

Had a broken window during installation (chip/weakened glass during mfg?) and dented screen. Was very easy to get free replacements through HD.

I found that replacing old double hung windows was very easy—If you have other styles such as sliding aluminum and/or stucco—it will not be nearly so easy. With myself and one other person, we installed 20 windows in less than two days (two story home). My suggestion is to leave the exterior stops of the old double hung windows in place. Caulk the backside of the stops and slide the new window from inside of the house and press out (I had to trim the interior sile to allow the window space to tilt in).

I chose the double hung because it is easy to replace either window as a tilt-out unit if broken (simply order a replacement assembly and pop-in the new one). Other styles see to require you to remove the entire window+frame assembly if the non-operating glass was broken. I have not tried taking a broken window to a glass shop--so I don't know if you can get a cost effective fix without going back to the factory--you will have to ask that question if it bothers you.

A double hung window was about $100 per window more than a single hung (I don't remember now--but it was probably something like $300-$350 for a 2.5' by 3.5' sized window. Not cheap--but no wind leaks/noise, and (pleasant surprise) a substantial outside noise reduction (used to have a drummer who lived next door to us).

We just moved into a 65 year old 2 story home that was drafty and cold--I choose to bite the bullet and put in new windows (installed myself) and insulate the walls/ceilings (contractor ripped out wall board on exterior walls to install fiberglass bats and new dry wall/trim) (I will do between the ground floor joists, probably myself, later this summer).

Plus a new hi-eff gas furnace (the old one was shot).

To be honest, I don't know that all of this will save enough energy to be cost effective (I would guess that I would have to save $500-$1,000 per month in energy at current prices to have a 5-10 yr payback and I have never paid much more than $100 per month in power in my last home and a long term average of $50/month for a family of 4). But this house is much more pleasant to live in now--is pretty much 68 +/- 2 degrees F over the last month with little more than opening or closing a couple of windows to regulate the temperature (and I added a new operable sky light over the stairwell--this was expensive but really brought light into the darkest part of the home and allows me to quickly vent heat on a hot day). My other splurge was to replace a pair of French doors with double pane doors (and much better weather stripping).

Note that the weather has been cooler and wetter than normal so far this spring—we had a few warmer days but have not had extended hot spells yet.

Would I do it again? Yes—without hesitation. But I am planning on living here for many years to come. I would not do this for someplace where I was only going to be there for a few years (at least, not the whole home—may be a couple of rooms though).

You can experiment on your home. If I was trying to be cost effective, I would insulate the ceiling (for the whole home if possible) and change to double pane windows first (at least in the rooms were I spent the most time). If you have a newer home, some of the big home centers have stock sizes of vinyl windows that may fit your existing window—if you only want to retrofit one room and see how it works, this may be a good way to go for a first try.

Insulating the walls can either be done by blowing in insulation (two inch holes all over your walls—with unknown voids—I was told by other contractors that they would see a maximum of 50% coverage when they tore into existing walls to remodel) or ripping out the existing plaster/drywall and installing new bats. We chose the latter but it is much more expensive (2-3x??), messy, and time consuming. You probably should count on redoing your floors with option #2. And when you do option #2, you probably will want to do new electrical—if it is an old home, and fix broken joist, that sewer pipe, replace iron water pipes, etc…. It never stops.

One last suggestion, don't use Silicone Window Caulk—Even if it says it is paint-able. It will not take paint well. There is another type of caulk—something like "butyl" something or another that is made for windows. This stuff will last a long time too and it is paint-able.

Again, without knowing the age, condition, and location of your home—take the above advice with a grain of salt. I hope that the above helps.

Sincerely,
-Bill

Privacy mirror film will push the LIGHT back out of a window, and therby cool the room. and it doesnt HAVE TO be stuck on the window (after time that stuff is very hard to remove)
smoke films on the inside are useless, just heat up the glass, or the film instead of the room, but reflecting the 500W of heat that can come in 5 feet of window can save loads of AC.

running a AC off the solar is tough, dang ac take not only major juice, but a huge starting load. i played with Peltier, which could work as a micro air conditioning, and it was not so great either.

i think the key to solar AC is going to be motivating volitile gasses with the HEAT from the solar energy, instead of trying to poorly convert a entire rooftop to run a bad efficency short cycle compressor air conditioner.

Mednanu
did you know that in your quest to grid tie (reverse meter) you actually have to match thier sinewave too :-( Syncronized.

these inverters chargers, and grid tie systems are huge walking heat syncs, a tribute to thier grand efficency. why cant they make silicoln parts that Suck Heat as thier losses , instead of pumping it out in mass. /ubbthreads/images/graemlins/wink.gif

VidPro,

The solar grid tie inverter I will have installed is around 94% efficient--not bad at all (150 watts of loss on 3kW of power). It is hardly worth trying to capture that waste heat on a cold winter day.

Xantrex 3kW Grid Tied Inverter

Your comments on keeping solar radiation from entering the house in the first place are absolutely correct. Adding shade (trees, awnings, etc.) are also good options. Making sure that you use CFL's and keep overall power use low helps too (such as venting your stove/kitchen and/or only cooking big meals when it is cooler to keep heat out of the living area during the hot part of the day, etc.).

Regarding matching the sine waves to the utility... Technically, not matching the sine wave current gives you a poor power factor but an inverter will work OK

In newer computer/electronic equipment power supplies (over ~100 watts or so--don't recall exactly) having Power Factor Corrected supplies is mandatory for many countries. And is just good sense because of I^2R losses associated with the higher current of non-linear and poor Poor Factor equipment (for non-technical folks, think of hooking a big Cap or Inductor directly to an AC outlet--basically the utility is supplying current but can't charge for the power because there is no work being done--current is +90 or -90 degrees out of phase with voltage and no work is done--except for I^2R heating losses--everything works fine, but the utility supplies current without being able to charge for its full value, i.e., work--big industrial sites, like refineries, will pay penalties for power power factors--utilities have capacitor banks that they can switch in and out to handle AC and irrigation loads during the summer).

All that said—it is still not safe or wise to connect a home made inverter to a utility even if it was designed well. The other part of the "contract" is that the company goes through regulatory testing and ongoing manufacturing safety controls (with companies such as UL—Underwriter's Laboratories) to ensure continuing safety and compliance with the requirements.

<font color="red">Disclaimer: Below is a suggested way of doing a cheap and dirty grid tied power. I have used elements of this before without any problems—but I have not done this as a grid tied power system. And therefore, the following is placed on this board for discussion and experimentation purposes only. As with all grid tied systems, there are inherent dangers and unknown effects and consequences that are not addressed by the following. Anyone wishing to experiment with the following system is entirely responsible for the legality and safety of their system. </font>

All that being said—there is one sneaky (and, I believe relatively safe and legal) way of putting power back into the AC mains. This would be the Motor/Generator set. Basically get a DC motor sized for your solar array and connect it to any normal AC induction motor (not synchronous or AC/DC brush motor or true AC generator) and connect the AC induction motor to your AC lines through a relay that is controlled by your solar panel output (or some other sensor to make sure that you are generating positive energy and not just spinning everything from the AC Line).

Basically, the way this works is that your induction motor starts and will run the motor/gen set at ~1,725 RPM or so (consuming AC power). Now, power up the DC motor with the solar cells and start driving the induction motor at over 1,800 rpm (probably at 1,875 rpm or what ever the inverse of the name plate of the induction motor is).

This works because there is a magnetic field in the armature of the AC Induction Motor induced by the rotating magnetic field of the external stator that was setup by the AC mains. And it is safe because if the AC mains fail, there is no current/voltage to maintain the fields and the output will drop to zero until the AC mains are turned on again (this is not an AC generator and there is no "self exciting" of the "generator" for it to generate power in the absence of AC line power. You would also need to understand the DC side of the circuit and make sure that any DC voltage generated by motor/gen set does not damage your solar cells.

The down sides of the above—probably terribly inefficient (probably in the 50% range) and I would want to experiment on making sure that the system behaves safely in an AC Mains brownout/power loss situation. Also you would have to make sure that the control circuit is setup so that it only runs when positive work is being done by the solar (monitoring RPM is greater than 1,800 RPM, or output current, or estimated based on Solar Power input). The advantage is that this system would work for any home made power source (wind, hydro, bio-fueled generator set) without costly electronics and can be built from scrap yard components.

That all being said, this is based on how I have generated 3 phase AC power for large mills and lathes in a business that only had single phase power available (you hook up a 5 HP 3 phase Y 3,450 RPM wound motor to your single phase power, give it a spin with a small motor to get it rotating, then hit is with the single phase AC power. You connect this 3 phase Idler motor to the reset of the 3 phase equipment in your shop… Actually works very well. I am sure that the generated phases are not great, but you could not tell the difference when running equipment up to ~2.5 HP. You need to make sure that any control circuits are connected to the "true" single phase power and not to the generated third leg.

-Bill

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BB said:...I am not sure—but we may have a miss-understanding… The vinyl windows I am talking about are "Vinyl Framed Glass Window Units" and are usually used to completely replace the entire existing wood/aluminum/steel windows.

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Awe, dang. And here, I was hoping that you had discovered an option that I totally hadn't heard of before. But.....I just might experiment and see how an extra double pane of acrylic ( with a very small air gap in between ) applied over the inside of the glass pane might be able to act as an extra heat barrier.

Your A/C motor hack sounds like an intriguing idea. I might be able to play with an IC and some coils to try to simulate the role of the A/C motor just for research's sake. But I too wouldn't want to risk the life of someone working on those residental lines unless I had thoroughly vetted the idea with a lot of research first. ....But, it sounds like a very nifty and ingenious hack at first glance. /ubbthreads/images/graemlins/grin.gif

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VidPro said:......running a AC off the solar is tough, dang ac take not only major juice, but a huge starting load.

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That's the whole beauty of an intertie inverter - the A/C doesn't run directly off of the solar array but can draw on grid power for those high amp startup and operating loads, then allow the solar panels to 'pay that energy back' into the system, over time, while the A/C unit is off. It also allows one to offset the operating cost of all of the other electrical appliances in their home w/o going through the hassle of putting them on their own loop. Other than the safety it affords the electric company's Linemen, this sort of give & take between the grid and the array allows me to scavenge engery that would normally be wasted once a simple battery system had reached full charge and could no longer accept any more energy from the array.

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VidPro said:did you know that in your quest to grid tie (reverse meter) you actually have to match thier sinewave too :-( Syncronized.

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Yes, actually I did. And quite frankly, designing a circuit that will be able to align both its phase and exact frequency to match the grid's sine pattern is beyond my current electrical engineering skills, hence why I'm more than happy to concede and buy a kit or a pre-fab unit. /ubbthreads/images/graemlins/wink.gif I don't mind soldering it up, SMD's and all - I just don't feel that I could do an adequate job designing that type of circuit from scratch at this point.

Mednanu,

You don't want a very small air gap either--I forgot the exact size, but 1/2-1" is the approximate range. If the gap is too large, you will get convection currents and lower the insulation value. Also, watch for moisture--you can get dry rot if you are not careful (in cold weather).

-Bill