Newbie to PV... with a question

[Zaphod Beeblebrox]

I currently have water heating panels on my roof for my pool.  I would like to add panels to generate a hybrid-gridtie solar electric system.  Anyone have any thoughts?

[kitno455]

thoughts, uhm, yeah, the two systems are completely unrelated, if you've got enough room on your roof?

allan

[Zaphod Beeblebrox]

I know they are unrelated... I was thinking of something like mounting the cells over top of the heat exchanger...

As for room on the room... well, there is the problem

I'm just starting to look into this.  I have a 5k inverter and I am looking at getting some batteries and panels to start to play with this...

[Zaphod Beeblebrox]

Another Question as I read through the posts on this board...

If you use a Charge Controller, does it charge the batteries directly (DC-DC)?

So you don't need a 1/2 wave rectifier to charge the batteries, or is it a 1/2 wave?

Can you hook a panel directly up to the batteries to charge them?

[kitno455]

blocking the light to the heat exchanger will help how?

pv panels need to be cooled, especially if you use a mirrored concentrator. i suppose you could combine the two. but without the concentrator, i dont think enough heat gets to a covered exchanger.

allan

[MelTx]

 NuBee I dont have a lot of time in on PV either.But they all put out D.C and you hook them directly to the batts, you dont use a rectifier.Or if you are going to use a controler, go to the batts, through it.Most factory made PV cell have a blocking diode built in that keeps the batts from draining back thru to the cells at night.

                                    Hope this helps some. MelTx

[Zaphod Beeblebrox]

I have one that is just black plastic piping, no mirrored concentrator.  It's a 2 inch pipe on top and bottom with a series of small pipes running between the two 2 inch pipes.  

I was thinking I could mount the cells to the top of these, but doesn't sound like that is a good idea.  I think I may need to step into this slower...

[Phil Timmons]

Yeah "the not related" portion (and the [relatively] high entry cost of a serious operation) of PV cells are why I am tending to just route around them.  Still doing some design studies of direct solar heat to electricity -- ie Solar Boiler => Generator.

When you consider that heat (space heating and water heating) is the major power consumer in many house and small business applications, and there is no direct fallout of heat from PV it does not make a lot of sense.  The boiler rigs throw off enough "waste" heat electricity generation, that it is directly useful as a domestic heat source.

[Dreadstar]

 I assume there is a pump on your hot water panels you could get a small panel to run that atleast.

  I have seen the hot water panels surrounded by solar panels on some installations so as long as you have some roof space you could put up a few panels. Grid tie is nice but  you could always do what i am doing. AC power for the things that require more than i can produce with my 220watt array. the dc power for things that i can use instead of AC

Such as 12vdc cfl and LED arrays and some fan arrays i made to replace the 2 20" box fans that i had running almost 12 hours a day combined waste of those 2 units was 2.124khw a day. New DC fan arrays draw 20watts each move 519cfm @ 12vdc they actually run at 13vdc avg so they move even more air.

Not everyone can jump into solar and put up a 4kw array. It would be nice but alas. Space available to install them and the $$$$$ it takes to do it. Big bite.

But there is always space for atleast 1 panel even if you have to trot it out into the yard every after noon and charge a battery that is connected directly to it. Don't really need a charge controller for that just a cheap dvm to monitor the battery voltage. If nothing else you could use it for charging other rechargeable batteries off a small inverter or dc to dc converter.

More RE less fossils.

[georgeodjungle]

and not to mention how poor pvs are for an investment..

and grid ties are a vary vary bad investment.

other than that,yep you could make your own power.

[Zaphod Beeblebrox]

Okay.. Man this is a complex subject.  Thanx for all the comments.

I have spent alot of time reading up trying to catch up!

Here is what I am thinking...

I have a 5000 Watt inverter (nothing fancy) already which will pull over 300 Amps at full load.

I'm thinking of getting six 12v, 94 Amp/hr batteries for 564 Amp/hrs of run time which would be 6748 Watts need to fully charge the batteries...

So, doing the math... I would need 6, 100 Watt panels to charge the battery array.

I have a 12 foot x 24 foot area I can install panels on that faces south, I'm looking for array's that will fit in this area right now.

Next problem... I'm in HOT HOT HOT Florida... What about keeping the batteries cool?  Everything I look at says they need to stay from 70 - 85 degrees F.  Do I need to air condition them?  Can I just blow DC fans over them?  I assume that they cannot go in my house because of the out gassing, and I think I would be defeating the purpose of the array if I had to run the AC to cool the batteries!

Anyone had to deal with this yet?

 

[John II]

I know that technically if you handle things correctly, it should be safe to put batteries in your house, garage or basement. There are methods of providing ventilation for them such as a sealed cabinet with a dryer hose vent and small fan, to actual small tubing running to each battery cap. There is also a product I think they call "hydro caps" This is a special battery cap that combines the gassing and coverts it back into water which drips back into the battery. Using these you rarely have to top your batteries off with water.

You'll have to check with your battery manufacture's web site, but I think batteries can tolerate hotter conditions, but it de-rates their usable capacity.

The big thing to check would be to make sure the battery installation meets all necessary codes for your house insurance.

I'm sure that an air conditioner would defeat your purposes and would draw immense amounts of power.

John II

[henjulfox]

Slow down on the math.

Your batteries will hold 6768 Watt hours. First of all you can't use all the watts

without destroying the batteries. For long life you only want to use 20-30% of

capacity. The lower you discharge them, the shorter the life. Same principal with

heat - more heat lowers the life. But I'll bet if you put a thermometer on the floor

of your garage you'll find it's not as hot as you might think. It's August now -

December is coming fast.

So you've got around 1700 watt hours of capacity. That's 1700 watts for 1 hour or 1

watt for 1700 hours or any combination in between. Same math for the panels. A 100

watt panel will charge them in 17 hours, 200 watts in 8.5 hours. Panel, wiring,

battery and inverter inefficiencies all subtract from your useable power - all

together probably pushing 50%. There is a thread currently running regarding PV

panel efficiencies.

The load you hope to run dictates the quantity of panels you'll need and the length

of time you want to keep the load running between charges determine the battery

bank you'll need.

-Henry

[Zaphod Beeblebrox]

Thanx...

Okay, 1700 watts, 12.75 amps of AC power at 120 volts (assuming 90% efficiency on the inverter).

In the summer months we get about 10 hours of good sun.  Winter probably more like 6.  

So, I am looking at needing somewhere around 300 watts on the panels.  In the winter time then I would get 1800 watts to the batteries, keeping them charged throughout the day.

I would like to begin with running a refrigerator on my inverter.  I have heard that there are some issues with motors burning out because the sine wave is 'approximated'.  Any thoughts on that?

My garage is 90+ degrees during the summer.

[Zaphod Beeblebrox]

I think I can put them in the garage, Which is already vented (Gas appliances) and augment with some fans to move air around and cool it off.

[ghurd]

Maybe check a solar insolation chart for hours of sun.

Those numbers seem kind of high.

[henjulfox]

1. Careful about those gas appliances. They frequently have a pilot light. Open flame and hydrogen venting from a battery don't mix well.
   
2. Sorry to keep knocking down your power but... 10 hours of sun dosen't mean 10 hours of panels putting out their rated capacity. Hold up a piece of paper, pretend it's your panel and your eye is the sun. Now turn the paper at an angle. The whole paper is still exposed to the sun but it's blocking less of the light. Blocking less light means generating less electricity. Top of my head I would guess your 300 watts of panels would generate 1500-2000 watt/hours of electricity on a summer day without a cloud in the sky.
   
3. I have 800 watts of panels on the roof. During the summer I can run my refrigerator and a house circuit. During the winter just a house circuit.
   
4. Lastly, the dirty little secret we all know and hate to admit. For what I've spent on my panels, batteries, inverter, and misc I could have bought a new refrigerator, the electricity to run it for 10 years, and have some left over for beer. The answer to the obvious question is that it's a hobby of mine. I get as much pleasure out of messing with my system as the next guy gets with his boat, or golf lessons, or dirt bike. At least my hobby gives me a little bit of payback.
   
   

-Henry

[steak2k1]

Lastly, the dirty little secret we all know and hate to admit. For what I've spent on my panels, batteries, inverter, and misc I could have bought a new refrigerator, the electricity to run it for 10 years, and have some left over for beer. The answer to the obvious question is that it's a hobby of mine. I get as much pleasure out of messing with my system as the next guy gets with his boat, or golf lessons, or dirt bike. At least my hobby gives me a little bit of payback

No truer statment.  but it is the satisfaction of providing your own power.  At this stage I have done a similar project with a tent trailer as a start in RE.

2 X 50W panels in parrallel, sun guard controller and armed with an 800w inverter. allows me to plug in my Bar fridge (not a pelltier chip type), make icecubes and camp pretty darn near anywhere for at least 10-12 days as long as good sun is avail.  Good batts are a must.  Not automobile but true deep cycle style.  Mine are 6V Trojans (T105) 110 AH cap ea in series.  The panels don not really keep the batts always fully charged but certainly extend my camping time significantly.  Switching from an Igloo 12V cooler to using a bar fridge has reduced my power usage also as it is an actual compressor type and works quite well while giving me much greater refridgeration capacity.

Suggest to stay away from 12V RV type of batt group 27 I think they are...just a poor compromise between SLI (Start - Lights - Ignition ), types and deep cycle.  6V or if you can, find some good used 2 volt batts...that is for sure the way to go.

Suffice to say, what I spent on panels/controller/wiring, inverter and my batts....will take at least 10+ years to pay for.  However now camping is "free" and I also have the benefit of camping where I please at low cost per night ($ 15/night on avg) as opposed to $ 35+ a night with electricity/water/sewer type RV park with everyone crammed in like a sardine can.!!

rgds,

stk

[Zaphod Beeblebrox]

I'm looking at getting into this as a hobby as well.

Been thinking about a sterling generator as well... Hmmm...

Just would be nice to a) have something to lower my dependance on Progress Energy and b) a backup in case of another Hurricane!