Waste less Solar

[mettleramiel]

I don't have the best set-up for my solar panels. I have about 300w going into a 225ah battery bank. Since my wife and I are gone all day, we use the power generated at night and then top the batteries back up while at work on the weekdays, and on a weekend if we are home, we will use the power as it's coming in. It's not the most ideal since we may use up lots of power one night and then have no sun for a few days. The real problem I have, though, is with all of the power that I'm wasting.

During the day, the charge controller will taper off as the batteries get full, like it should, but all the potential power that I could be getting is wasted. Here it will be a bright, sunny day and only 1 amp will be flowing when I could be getting much more. Is there some way I can use this wasted energy? I know a dump load controller will do it, but I'm in a basement suite and don't really have anything like a water heater to dump to. Is there maybe a controller out there that can store the power in capacitors (shot in the dark) to charge later or something? I don't know, I just hate having all that energy go to waste.

[ghurd]

More battery.  A lot more battery.

Batteries store power best.

G-

[richhagen]

There are many schemes for storing energy besides batteries.  Unfortunately, not many of them are well suited to storing large amounts of energy for long periods of time in a garden apartment.

I have about the largest capacitor bank of anyone I am aware of, although there are probably people on here with larger banks, but I am not aware of it.  My capacitor bank is 110 Farads at 64.8 Volts, and if you were to buy it retail it would cost a few thousand dollars retail.  Even if you could utilize every Joule of energy that that bank can store, you would only  have about 64 Watthours of energy, equivelant to using about 5.3 amp hours on a 12V battery, and much less than what you already have.  The reality is that for me, I can only use about two thirds of that storage which falls in a useable voltage range for me.  In short, storing the energy in capacitors for you is likely impractical.  

You are using your batteries to store power, batteries are less than ideal, and this is a bit problematic for you.  If batteries were perfect, and did not self discharge, you could just get a larger battery bank.  Unfortunately, all batteries self discharge to some extent.  The larger you make your bank, the more energy you will lose to this self discharge.  You will have to figure out the optimum battery bank size which may be a bit larger than what you have, I am not sure, but batteries are likely the best option for your described situation.  Rich

[scottsAI]

Mettleramiel,

So much about your situation is unknown, so we must guess.

Basement apartment.

Run washing machine on a timer, while the power comes in on a sunny day.

Many dishwashers have a delay timer, set to run during the day.

Etc.

If above is not practical, how about as heating in the winter? Air coil heater as a load dump. Controllers to do this are inexpensive. Run a window AC unit in the summer to cool the place down. (load dump!)

Have fun,

Scott.

[Colaman]

I've a regulator here (a conergy SCC vision) that has an 'excess energy' output.It comes on when the batteries are fully charged and can be used to turn on extra loads.

My suggestion :

Get a 12V fridge/freezer. Fill with drinks (or things that don't mind getting warm). Power the fridge whenever the batteries are full, giving cold beers for 'free'. IF you keep enough in there, (I know, it's hard....) they'll stay cold for quite a while with the power off.

Keep a few beers in the normal fridge for cloudy weather. :-)

[Opera House]

If you are handy, work up a pre heater tank for water heater.  300W won't do much heating water even if you devoted all of the power to it. For that reason, it would have to be don really cheap.  I do run a freezer/fridge on just 150W of panels as a dump load.  It comes on at a set voltage and runs for 10 minutes.  That is just about enough to cool drinks.  This year I have doubled my panels and will have to get more creative.  Really, batteries are your best option and then find uses you really want.

[zeusmorg]

 There are a lot of schemes to better utilize excess energy.. the most efficient is to use it as it's coming in. However that is not always practical.

 In your case, it would probably be easiest to add more storage capacity. The trick here is to make sure you don't go too large. You do want to hit float occasionally.

 Some people set up a secondary bank. When the first is fully charged, the dump kicks in to the 2nd bank. This can be a good use for batteries nearing end of life. If you don't use it, it's wasted anyway, is the thought.

 Look into Ghurd's dump load controller, it's probably the sweetest thing here. Cheap, simple and effective. I believe it can be found in the classified section.

 You can look at what you can use the extra power for in the day. Charging station, etc. If you put your mind to it, i'm sure you can find a way not to waste too much of your excess.

 

[TomW]

Ghurds' stuff can be found on his site:

http://ghurd.info

Pretty good guy for a dozenaire. I like poking him since he got rich off his circuit empire but he ignores me.

Just FYI.

Tom

[ghurd]

I spread all my money around on the floor and rolled around in it the other day.

My wife came home and said "Put those pennies back in the roll!"

G-

[thirteen]

Maybe you have already done this. Isolate the power to your power using items. A switch to shutoof all power when you are gone or not using them.  Most items still use power in there systems even tho they are shut off. It might be some help when days are cloudy and it will conserve your energy usage. As others have said more battery bank or look into helping some one else use you extra power. Just some ideas

[Jeff]

Again, another vote for Ghurd's dump load controller here. You can get used 55 gallon drums in pretty good condition for 15$ or less. Then 12 volt water heater elements in almost any size you please at any place that sells RV/camping stuff. I would clean the barrel thourougly, give it plenty of time to dry, and I've found the larger cans of zinc chromate apray paint primer in auto stores to treat and seal the inside. 1 can put 3 good coats on mine, and I've done two metal one's like that. The metal one's are easier (and safer) for adding those 12v heating elements. Insulate it as much as you can (I have R-34 on both of mine, not counting the sheetrock around the two of them.

Once you get to the point you can get all that water up to 110-140 degrees F, you can use that as storage to use for just about anything. I plan on using it, and/or compressed air to heat ammonia to drive a small shaft & flywheel assembly at 200 RPM. Perfect for another small genny you would use on a windmill, but don't have high enough average wind speed in your area. With 110 gallons of water, you wouldn't need to worry about adding a 3rd dump load any time soon.

It sounds like you could use at least double the amp-hour battery storage too. Most "small" systems most people now would say are in the 400-600 amp-hour range. Run more "stuff" from those batteries & inverter, and enjoy the lower electric bill!

[Bruce S]

Tom;

 I agree. Since G- controller can be "adjusted" to different battery voltages. It can be a good fit for "wasted" power.

AND he's so modest about his product ))

He'd probably even assemble it for just a few pennies more for those less inclined.

One thing that can help is to pipe the dump off to say a bank of rechargeable AAs, this bank can be a few as 4 and and many as couple hundred?

AND who can't use a few extra rechargable AAs :-)

NTL (wonder what happened to him?) use to take the cheapest PVC pipe and build light sticks out of rechargeables. That ultra-thin copper wire would go right up into the pipe, and he'd just stick a dollar store switch on it and tape it down.

Cheers, gotta go get the snow blower ready for the white stuff CO. is sending our way:-/

Bruce S