Ian Williams's posts

Hello Everyone!

For those who didn't know, right now the Solar Decathlon (www.solardecathlon.org) is on the National Mall in Washington D.C. This is an international competition with schools from the US, Canada, Germany, Spain, and Puerto Rico. All houses are powered entirely by the sun.

I just returned from a trip to visit my school as well as see everything else, and I must say that it is amazing. The technology is impressive, the architecture is incredible and just wow... the competition started last Sunday, and will end this Friday with the winners announces on Friday as well.

I highly recommend you attend this, if you are able. The next competition will take place in 2009. Well, this is all from me.

Have a great day to everyone

Josh,

I am a little curious as to was exactly is the bulk of your 48KWh a day? also, to remember that for every 1 dollar you spend on energy conservation, you save an average of 5 dollars on the cost of the pv system.

Its great to hear that your new home will incorporate LED's and the such, but keep in mind the simple rule stated above, and it may help in your decisions.

Ian

Yes, very much so.

AGM batteries, because they are a sealed battery, can be stored in any orientation. These batteries also have little risk of the release of large quantities of hydrogen gas, if they were to be damaged in such ways. The ones that release hydrogen are the flooded lead acid type batteries, but remember they only burp when you hurt them in some way (over charge, too hot)

Hope this helps,

Ian

Jenn,

First off, I love your idea.

Now down to the details. If using 25 amp hours at 12 volts, 300 watt/hrs a day, and with a decent amount of sun, it is very doable. If you were to use a 20 watt panel, phew, you would require 15 hours of sunlight a day. Unfortunately, this is a little hard to do. If you were to up the wattage of panels, lets say to 50 watts, then you would only require 6 hours of sunlight a day, which in your location in the summer is a definite amount. In addition to the panel, you will also need a Charge Controller to protect the battery from over and under-charging. I recommend Phocos
http://store.altenergystore.com/Charge-Controllers/Solar-Charge-Controllers/Pwm-Type-Solar-Charge-Contollers/Phocos-Solar-Charge-Controllers-Pwm/Phocos-CML10-2-10A1224V-PWM-Charge-Controller/p1013/
and I also use the 15 amp model of the link above. If you already have the battery, then you are close to being ready to go.

As with any Renewable Energy system, it's better to put more money into efficiency than into generation. But with you using it for camping, that may be harder and what I've described should work.

Hope this helps,

Ian

Quick question that have been wondering about,

I have a 12V battery, but I forgot the exact specs of the battery that was given when I bought it. My question is, how many AH's are there when the battery gives a 23 Amp average for 150 minutes? Am I correct in saying there are  57.5 AH's available?

Thanks for answering my little question.

Ian

Murray,

Yes it does mean that you have 1440 AH of storage after you ran both banks in parallel for a total of 1440 AH @ 12V.

Ian

Murray

I can help with the AH capacity but not the inverter/charger.

You are correct in wiring up the 6 batteries in series for your 12V, which means that your AH capacity won't change. The 8 Hr capacity of 720 AH means that if you completely discharged the battery over an 8 hour period, it would deliver 720 AH's, then it would have nothing left to give. Now, if you were to discharge them at a faster rate, you would get less than 720 AH, and if you discharged them slower than 8 hrs, you would get more than 720 AH.

Just a reminder that when stringing together batteries, you either add voltage or amperage, not both at the same time. So you correctly ran the 6 batteries in series for your 12V, which meant that your AH capacity didn't change. And of course the flip-side would be that you wired the batteries in parallel to have 2V with 6 X 720 AH of capacity. Also, remember that when you multiply your voltage times your amperage, you get your wattage. So 12V times 720 AH is about 8640 Watt Hours of storage, and a tag along with that is to remember to try to never consistently drain the batteries below 50% capacity. So don't use more than 4.32 KWh's of energy.

I hope this has helped. And again, I am not sure about the inverter/charger. Someone else to lend some advice? 

Have a nice day, Ian

Assuming both panels are the same wattage and same type; to wire two, 12V panels to get 24V, just run either the positive or negative wire from one panel to the opposite wire on the next panel. Ex. red to black. As far as any breakers, you wont need any between the panels, but most likely between the panels and battery. Hope this helped

Ian Williams

I would have to agree, the forums are a great thing, and that learning about all of this is a lot of fun. As for that poor, lonely 7th panel, i like your idea of getting another to even it out. its good that you saw an ammeter deflection of 2.5 amps for the one panel, means everything is working at 12VDC, now to just wire in parallel and series and viola! Have fun, and i hope it works.

Ian

Larry, okay, i think your problem is an easy fix. yes, the VOC needs to be greater than the nominal charging voltage. after you upgraded your entire system to 24V, i think you may have forgot to wire the panels for 24V. your reading of 21VOC is a perfect indication that the panels are still at their 12V setting. wiring them in series then parallel for your 24V nominal and approx. 42VOC, will allow the cx-20 to start to charge the batteries. That should do it! have fun, and i hope this will help. Good day.

Leesa,
     not sure as to what, exactly, your asking. Yes they do have solar powered backpacks with built-in batteries. one popular one is called Voltaic and is made by Voltaic Systems( www.voltaicsystems.com ). there are directions on the web to build your own solar powered backback. i hope this is the answer you were looking for. have a nice day

hey, kinda confused here. in a battery bank set-up, if its being charged and discharged regularly, how far should it be allowed to discharge on a daily basis? like, if 50AH are taken each day, should the bank 250AH so its only 20% discharged or should more or less leniency be given?

Tim,

Good news and bad news. The good, you are on the right path. Having that said, here is the bad. I've seen and read on solar shingles (uni-solar, the actually shingle looking panels), and in the end, they are more of a losing battle. Unfortunately your area, about the same as mine, doesn't get a lot of solar radiation. If you on purpose or accidentally chose to use amorphous silicon, i don't know, but its a good choice in areas with less total irradiation. the main problem with the solar shingles is that they are expensive! (not that much else isn't) but at $7.33 a watt, and only for the panel, that already makes it less feasible. For as gorgeous and well made as they are, they just don't make sense. I do not know much about the Sharp 62W panels, but from the look, they're quite similar to the uni-solar shingles. the panels that i do like however, are another uni-solar product, their roof laminate. the only drawback to these laminates are that they require a 15.5" wide metal sheeting on the roof. but i like the wide sheets better than the shingles, personal opinion.

Now onto the cost, as with all RE endeavors, the monetary payback is not immediate or even soon. over 20 years, in the better of locations. now this of course can be affected by incentives, special loans, and other tax breaks, and of course, a reduced energy bill and possible selling back extra power to the grid. If your so inclined as to the actual energy payback, its only around 2 years w/ uni-solar products.

Finally, if your association is cash-strapped, this may not be feasible. not to discourage you at all, but money is fortunately your biggest enemy. one thing to consider doing, is to maybe go with a roof structure that could be built upon in the future, using solar PV panels to generate electricity. if this is more appealing, then i recommend the 15.5" metal sheeting, and the hope of adding to it later. If you could do it, I'd try to convince those in your neighborhood of ALL of the benefits of such a system, even a small one (less than a kW). once installed, it can always be added upon(except for certain inverters), and expanded once the money is available, and such structure would have electricity whenever the sun was shining.

I hope i have been of some help as far as advice and not so much on the #'s end of it. whatever you decide, do so with confidence and support RE wherever possible.

Ian Williams

im asking because ive gotten my dad interested in solar, and now, after loosely rigging up our newly built shed (gallery pics), he is thinking of taking the entire garage in the house off the grid(baby steps). for loads, it will most likely be limited to 4 12v lights, hopefully cf, and then to an inverter for light power tools and the sort. he found a 1.5 kw mod-sine inverter from some catalog that he's going to purchase shortly, and wants to possibly use it in this app. i think 1.5 might be overkill but he wants it just in case he needs a larger circular saw or possible space heater. okay, so a straight 12v system. a mppt controller may be out of the question for now, but definitely a possibility in any larger system in the future. as of right now, we dont have another CC or inverter, only in the smaller shed. this is just in the pre-planning stages. what did you mean by "just try to keep it under 3 series strings in parallel"?? thanks   Ian

Thanks James, one more question. what is the most efficient way to wire-up 2 12v batteries in series for 24vdc but then draw only 12vdc for the inverter? im kinda confused on how to charge at 24 and draw all batteries equally at 12v. thanks again

I'd go with the uni-solar just because of their ability to generate power in less-than-ideal lighting conditions, being your shade, clouds, bird droppings, and whatever else you will encounter on the sea. As for cost, yes, they have a higher $/watt but when you factor in that they can produce, on average, 2 hours more per day than mono or poly crystalline, they can actually pay for themselves faster. I hope this has been helpful.

I'm thinking of using a large battery bank and i was wondering it it would be more pratical/economical to design a full 24V system or to use a voltage converter to go from 12V to 24V?

My opinion, go for it. going through my first winter w/ solar, even at low watt's, its amazing how much the a-Si panels will kick out. One thing to keep in mind though is that the snow will reflect more sunlight than just standard, there by increasing the actually temp. of the panel and the quantity of light to convert. That will give you a higher output, so keep that in mind when choosing the components of your grid tie system.

One more thing, id strongly recommend using a back-up battery bank and inverter, you know, just in case(or even as a primary source).

FYI, im a little over an hour south of Imlay City, just to give you a location reference. Have fun!