Running (8) 120w solar panels with no battery

[lonewolf2koc]

Providing that the sunlight availability is excellent only during the duration of the load (~11a-4p), is it possible to feed about 800W of panels directly to a 80A PMM controller -> 1000W DC-AC inverter and also direct 12vdc out to the loads? The loads I'll be using are: LED TV, lights, laptops, fan, fridge (12v). Prior to this I'm also feeding the 12vdc out directly to a 175 Ah AGM battery. But this is my 2nd system and I don't have the funds to get that battery. Also, there's a limited lifespan on those AGM batteries. Trying to avoid batteries as much as possible. Just solar panels and the load directly. This is of course limited to only good sunny day weather. If it's cloudy or rainy, I have to use generator or grid power and switch over via a manual transfer switch.

I found a reasonably priced 80A controller: https://www.amazon.com/dp/B01CSDYFA...lid=1URI1L4EVFJQG&coliid=I1SMIRHFLU465Q&psc=1

This should provide plenty of future panels expansion.

 

[highdesertranger]

what's your plan to run the refer overnight? without a battery none of those things you listed is available at night? if I had a TV and lights I would be using those at night not when the suns up. I don't quite understand when you say you already have a battery but you don't have the funds to get that battery. I am confused, not that hard to do. highdesertranger

 

[BradKW]

You're basically talking about what's called a grid tied system. I spent some time looking at one with a guy who installs them, and each panel had a mini inverter built into it. You probably need to do some research... not sure if grid tie can simply be converted to off grid when you get a battery...

 

[ZoNiE]

There are some inverters out there designed to do this, but they do need some battery connection to run properly to handle surge loads like motor starts... I saw them at the InterSolar show, can't remember the brand. Will post if I find the info.

You will have no power at night...

You really need a battery bank.

 

[lonewolf2koc]

what's your plan to run the refer overnight? without a battery none of those things you listed is available at night? if I had a TV and lights I would be using those at night not when the suns up. I don't quite understand when you say you already have a battery but you don't have the funds to get that battery. I am confused, not that hard to do. highdesertranger

This is a unique situation where I'm not completely off the grid. There are times where I park my minivan in the city. My electrical needs are completely off the grid, grid and off-grid (hybrid). I have full access to solar panels on the top of the house roof. About ten 120w panels to be exact. It's kind of wasteful of not tapping into it during day time. Another big problem I have is the pesky insect, particularly spiders. Once I open the front window to let the cable run into my van, those baby spiders will appear the following week. But I wired the solar panels through a firewall rubber insulation from the rear window. There I tap in 5 more flexible panels at 100w each. So when I'm in the metro area, I'd tap in the power from my van and roof into the garage to work. When I go to remote areas, I simply disconnect via MC4 connectors and there I'm 100% off grid. I'd say most of the time I'm in metro areas and not taking advantage of the free solar panel access is wasteful.

I realize that 12v AGM battery investment is extremely costly. I read at another forum where you'll have to pay 5-10x more for battery usage at night. There is a finite amount of cycles that can be used. For a daily load of ~200w, a single VMax 175W died out on my after 7 hours through the inverter. To prolong battery life, you'd only want to discharge about 25-35% max. Now I'm discharging it at 80-90% every night. In about a year or so, will have to spend ~$480 more for a new one. I'll be testing 12vdc loads directly soon to extend the runtime. DC-AC inverters are not the best when it comes to maximizing every Ah on the AGM battery. During off-peak sun hours (5p-10a), I'll use a manual transfer AC transfer switch that will switch from the 80A solar controller and the residential shore power. But when I'm in an off grid situation, I have to use the battery since there's no shore power at all. Another purpose here is to minimize tier 2 pricing structure that the utility company is charging. Tier 2 gets really expensive. I'm not planning to resell the power back to the power company. That itself is a big hassle (permits, fees, etc).

 

[Trebor English]

This sounds like disconnecting a car battery with the engine running.  In the car electrical system the battery provides stability.  When a cloud comes by the no battery solar system output will either drop to a lower voltage or go off.  After the cloud goes by it will restart all the motors at the same time many times before it succeeds.

Maybe get a cheap "deep cycle" battery.  Walmart sells 24 sized batteries at 3 different prices.  The most expensive weighs quite a bit more than the cheapest.  It is better but not good for lots of deep cycles.  As the sun goes down, turn off the loads.  On rainy days, keep everything off.

 

[skyl4rk]

A PWM controller is designed to turn unused electricity into heat (once the battery is fully charged). I would use a PWM controller for the full wattage of your system 8 panels x 120W = 960 W -> 960 W / 12 V = 80 amps. The 80A PWM controller (rated) should handle it, just make sure the PWM controller has good ventilation. It would also be beneficial to your system to use a load such as a fan, fridge, or cooler in peak solar radiation hours. That would reduce the heat build up in the PWM controller.

 

[highdesertranger]

I still don't understand what it is you are trying to do. first off though stop discharging your battery 80-90%. frankly I can't see how you are using that much power with the things you listed. highdesertranger

 

[lonewolf2koc]

I still don't understand what it is you are trying to do. first off though stop discharging your battery 80-90%. frankly I can't see how you are using that much power with the things you listed. highdesertranger

All I'm trying to do is capture the sun's free energy during peak solar hours without going trough the battery. My load is about 120-180w (going through an 1000W PSW inverter.) I'm seeing about 18-25A of solar output from the 6 120w panels. When the peak solar hour is over, I switch back to grid power via an AC transfer switch. In other words, the solar panels are generating live power for a 4-6 hours peak sunlight period only then I switch back to the metro grid when there's not enough output from the panels. But I'll not connect to the AGM battery unless in emergency situation (to prolong the service life).

Over a period of a month, the extra 5-6 hours of solar generation from the 6 panels (~900W@full sunlight capacity) add up to about $60-90 in power saving. Over a year, it'll add up almost a grand that I don't have to pay to the power company. The costs for the panels are ~$200 x 6, MC4 cables, transfer switch, 170 aH AGM batt. It'll take me about 2 years to break even. The thing is that if I don't do anything, I'll constantly pay the utility. But at least with the solar option, it'll be beneficial after the 2 years break even period. Hopefully, the six 150w panels has a service life for at least a decade. If I need 400W, I'll double from 6 to 12 (150 W) panels.

 

[lonewolf2koc]

I still don't understand what it is you are trying to do. first off though stop discharging your battery 80-90%. frankly I can't see how you are using that much power with the things you listed. highdesertranger

I think the answer to my problem is a cheap grid-tie inverter.

https://www.amazon.com/gp/product/B00RX3YF12/ref=ask_ql_qh_dp_hza

This pretty much eliminate the need for battery or transfer switch. Any suggestion or tips on grid tie inverter? I never used one. This will be the first.

 

[skyl4rk]

The grid tie inverters that I have seen do not allow any power to flow if they are not connected to 120VAC

 

[highdesertranger]

oh we are talking a grid tie system in a house. I thought we were talking a mobile system. my bad. highdesertranger

 

[Mobilesport]

what's your plan to run the refer overnight?  without a battery none of those things you listed is available at night?  if I had a TV and lights I would be using those at night not when the suns up.  I don't quite understand when you say you already have a battery but you don't have the funds to get that battery.  I am confused,  not that hard to do.  highdesertranger

You could put the refer on a very cold setting during the day and then thru the night when you don't have electric it would stay cool thru the night then do it all over again the next day , depends what you have in the fridge though. 
 I do that alot if I'm going to be working on my interior I get my fridge real cold then take it out and sit it in my storage all day unplugged , 10 hours later I pull out a cold pop

 

[blars]

PWM controllers put out pulses of full panel voltage alternated with nothing. They depend on the battery to smooth the output power. MPPT puts out less extreme pulses, but still counts on the battery for smoothing.

 

[GotSmart]

All I'm trying to do is capture the sun's free energy during peak solar hours without going trough the battery. My load is about 120-180w (going through an 1000W PSW inverter.) I'm seeing about 18-25A of solar output from the 6 120w panels. When the peak solar hour is over, I switch back to grid power via an AC transfer switch. In other words, the solar panels are generating live power for a 4-6 hours peak sunlight period only then I switch back to the metro grid when there's not enough output from the panels. But I'll not connect to the AGM battery unless in emergency situation (to prolong the service life).

Over a period of a month, the extra 5-6 hours of solar generation from the 6 panels (~900W@full sunlight capacity) add up to about $60-90 in power saving. Over a year, it'll add up almost a grand that I don't have to pay to the power company. The costs for the panels are ~$200 x 6, MC4 cables, transfer switch, 170 aH AGM batt. It'll take me about 2 years to break even. The thing is that if I don't do anything, I'll constantly pay the utility. But at least with the solar option, it'll be beneficial after the 2 years break even period. Hopefully, the six 150w panels has a service life for at least a decade. If I need 400W, I'll double from 6 to 12 (150 W) panels.

I just cant start to explain how wrong your thinking is on so many levels.  

Voltage differences, power fluctuations, Power used by different appliances.  Cost of equipment.  And so on and on and on~~~

A system, designed for the home, grid tied, runs just over $2,000 per KW of power.  The larger the system, the lower the cost.  That has a rough return on investment of perhaps 7 years.  These are rough amounts.   Tax rebates, specific electric company rebates, fees, and the cost of installation all have an effect on this number.

 

[lonewolf2koc]

I just cant start to explain how wrong your thinking is on so many levels.  

Voltage differences, power fluctuations, Power used by different appliances.  Cost of equipment.  And so on and on and on~~~

A system, designed for the home, grid tied, runs just over $2,000 per KW of power.  The larger the system, the lower the cost.  That has a rough return on investment of perhaps 7 years.  These are rough amounts.   Tax rebates, specific electric company rebates, fees, and the cost of installation all have an effect on this number.

I'll try out the small scale grid tie inverter (1000w) for $130 to see how it goes.

 

[GotSmart]

I'll try out the small scale grid tie inverter (1000w) for $130 to see how it goes.

Where are you getting your prices?

What brand and type of equipment?

 

[lonewolf2koc]

Where are you getting your prices?

What brand and type of equipment?

Solarepic Grid Tie Inverter 1000w Stackable w/ MPPT 20-45v Input 110v Output

https://www.amazon.com/gp/product/B01846NGNO/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

At $130, it's worth the try to save a few hundred bucks a month on power bill.

 

[GotSmart]

Best of luck on the permits.

 

[skyl4rk]

I looked into a grid tie inverter. One thing that makes sense is to have a lot of solar panels on a vehicle or trailer, that way the assessor doesn't add the value to the home and increase the property taxes. However, our electric rate is relatively low at the moment (about $0.10 per kWh) and much of the cost is based on monthly fees which don't go down if you use less power.

It would really make sense to have a large battery bank in the home and use a whole house inverter, and charge the batteries from solar. That way you can go completely off grid.