Really new guy

speedshot

Greetings all,

As mentioned I am really new to this, even the subjects discussed are out there to me (so many acronyms!)! Is there a glossary of terms where I can get some definitions and ground work info? I am doing some experimental work with solar now, but want to make more progress in that direction. Living in FL I am gleaning that the roof is probably NOT the best place for the panels. Rooftop temps here can hit 140 degrees F in the summer, not conducive to good energy production (but great for frying eggs!). I have a location to set the panels up that won't subject them to such temps, but need to ask about wire gauge to the controller. The distance to the controller is +/- 50'. The good sun time ranges from 4-8 hours, batteries are deep discharge marine type (sorry), inverter is a 2000/4000 surge (sorry again) and the panels (4 sets of 45 W (mega sorry!)) output 17.4 volts peak voltage. I'll stop blathering so I can find out how ignorant I am now. Hope this gives you a infinitesimal bit of info to go on.

Thanks
Speedshot

BB.

Re: Really new guy

There is the FAQ forum here--The first one is Glossary.

If you are not sure exactly what you want to with solar--there is kind of a "everything solar" list of projects and links here:

Working Thread for Solar Beginner Post/FAQ

You can choose to mount on your roof with 5"-6" air gap (does OK at keeping the panels cool), or you can ground mount or rack on roof mount. It is pretty flexible.

I have a location to set the panels up that won't subject them to such temps, but need to ask about wire gauge to the controller. The distance to the controller is +/- 50'. The good sun time ranges from 4-8 hours, batteries are deep discharge marine type (sorry), inverter is a 2000/4000 surge (sorry again) and the panels (4 sets of 45 W (mega sorry!)) output 17.4 volts peak voltage.

In the FAQ forum--there is a "voltage drop" Excel spread sheet calculator that you can use to to size your wiring for optimum voltage drop.,

Sounds like you are doing an Off-Grid backup system or possibly a Hybrid GT/Off-Grid system.

We can give you the generic rules and formulas--but it may be easier if you give us the Mfg and model of the major components are thinking of using. Different controllers/inverters have differing requirements and it can get confusing when we give non-specific answers.

Once you understand how the facts play with the specific devices--Then it is pretty easy to read the specs. from other manufacturers and see how they would work.

For example, Marine type batteries are a hybrid of an automotive starting battery and a deep cycle battery--It is OK for the "marine use"--but for solar system/inverter use--you should use deep cycle batteries next time. Deep cycle will last much longer (more cycles) before they "wear out".

Another issue is that solar systems do not really generate nearly the amount of power that people think the systems do... For example, 4x 45 Watt solar panels. Assuming 5 hours of full sun (good summer day for a coastal area), from the rating of the solar panels (180 watts) to the charge controller to the battery bank to the inverter to the 120 VAC load--the overall derating/efficiency factor is ~0.52 (yes--you will lose about 1/2 of the energy based on name plate ratings). So--for your system (note: I am being a bit conservative here in my generic answers--but they are close enough to give you a good idea about your system):

• 4x 45 watt * 5 hours of full sun * 0.52 derating = 468 Watt*Hours per sunny day

Now--that is enough power to run your 2,000 watt inverter for:

• 468 WH / 2,000 W = 0.234 hours or 14 minutes per day at full inverter load

Anyway--to help you more--understanding your load expectations, how many solar panels you wish to purchase--use of the system (grid tied, off grid, hybrid GT+Off-Grid), battery bank voltage (12/24/48 volt)--Roughly where you want to install the system (to figure out the amount of sun you receive throughout the year) and such would all be very helpful.

Just to be clear--conservation is going to be key to a good solar installation. Realistically, if you use the system 9+ months of the year for 20 years--your power will cost you $1-$2+ per kWhr--About 10x what your home power currently costs you--so anything you can do to reduce power usage from your solar PV system will save you lots of money (smaller solar system, less costs to build, less costs to maintain).

-Bill

n3qik

Re: Really new guy

speedshot wrote: »

panels (4 sets of 45 W (mega sorry!)) output 17.4 volts peak voltage. Speedshot

If you got them from Harbor Freight, I would return them. They have a 30 day return policy. The panels are ok, controller is fair. I started with two sets.

If you are going to put panels on your house roof, MAKE sure they are UL listed.

speedshot

Re: Really new guy

Thanks guys (N3qik and BB) for the info and links, and, yes the panels are HF but they were bought by means of a VERY extensive recycling program. They are good to experiment with and I won't die if a hurricane comes along and takes them away. I can't even say I'm on a shoestring budget, that's too lavish. I have no illusions of running my whole house (or even a large part). I'm just trying to save where I can, with intentions of reinvesting the savings into bigger and better toys. Speaking of charge controllers, I would like to upgrade that aspect. Would I be better off with an MPPT type and just dispose of the ones that come with the panels? I would like to maximize what I can get out of this 'system' lol. It will be a hybrid GT affair since the aforementioned "wind event" could take out our power and in this area we are discouraged from re-energizing the grid by backfeeding our breaker boxes. Thanks again for your patience and wisdom.

Speedshot

BB.

Re: Really new guy

For a small system... I would get the cheapest controller (Xantrex and MorningStar make good quality PWM controllers)--or even keep the one you have for now (as long as it is working) and use the "extra cash" to buy a couple good quality "12 volt" (really Vmp~17 volts or so) solar panels.

Poor solar panels--does not matter how good the controller is--no power is no power. Good solar panels--you can charge with diode and switch if you have too.

Eventually, you will want to replace the HF thin film panels.... Good quality crystalline silicon panels--the same size as your TF panels--Will produce 2x the amount of power for the same area. The crystalline panels are just that much more efficient (with respect to collecting solar energy).

Also--a small, quality genset (I keep giving free advertising for the Honda eu2000i) can be a very nice addition for emergency preparedness.

Most people (not running A/C)--need only a few hundred watts to keep a fridge, fan, a few lights, radio/TV running. The 1,600 watt Honda will supply ~400 watts for 15 hours on 1.1 gallons of gasoline--very quietly.

You 180 watt solar setup will supply somewhere around 468 watts or so for an hour a day of sun...

If your array is approaching the 400+ watt region--then MPPT can offer significant wiring advantages (very handy if the panels are a distance from the controller/battery shed). MPPT can offer a bit more charging power (10-15%) in cold weather-- but are not usually chosen for their power increase. MPPT are great for areas with temperature extremes (very hot/cold temperatures)--gives a a bit more "head room" to ensure proper battery charging.

If/when you get a "nice" PWM or MPPT charge controller--look for those that support a Remote Battery Temperature Sensor--Typically, you will charge the batteries a bit faster and to a higher state of charge. Also--for AGM/Sealed batteries--they are very sensitive to overcharging (hot batteries need lower charging voltages).

Also--the term "GT" or Grid Tied--Typically means a setup where the solar panels + GT inverter actually push energy back into the electric grid. Pure GT only work when the utility power is up. GT shuts down for safety when the grid is down.

Your system is an Off-Grid system... Basically, you have an inverter+battery bank and plug your appliances into the Off-Grid inverter (the standard 120 VAC inverter that we are all familiar with).

At least, that is how I think you are describing your system.

Any power can be a blessing in an emergency--but make sure you budget your power needs realistically based on what you have on site when the event strikes.

-Bill

speedshot

Re: Really new guy

BB. Thanks for your insight and info. Having spent two weeks without power after Ivan came and went I agree wholeheartedly some power is way better than none. Had to take out a white oak with a machete to get the utility to re-fire our house! By experimentation I found out the baby system would run the washing machine till it came to the spin cycle, dead stop. I'm sure the extension cord didn't help. If I can get the fridge "off-grid" I'll be ecstatic. I can absolutely swing the better controller soon but have to ask about how to tie the solar and grid systems together for that one circuit. The fridge is isolated and I don't want to backfeed the panel. The inverter is MSW but I believe it has the capacity (4000 surge) to handle startup loads. What type of shunt or other device do I need so there is a constant supply of power to that circuit? I'll continue to search for the answers on the forum.

Thanks,
Speedshot

BB.

Re: Really new guy

Regarding running a fridge--A basic fridge is around 400 kWhrs per year--or a bit more than 1 kWhr a day. Using a light broken clouds wintery kind of day with 2 hours of full sun equivalent:

• 1,000 Whrs * 1/0.52 off-grid eff * 1/2 hours of sun = 960 watts of solar panels

No longer a small system... 12v Battery Bank assuming 0.85 inverter eff, 3 days of no sun and 50% maximum discharge:

• 1,000 watts * 1/12 battery bank * 1/0.85 inv eff * 3 day * 1/0.50 max disch = 588 AH Battery Bank at 12 volts

A 1,200 watt inverter should be enough to start a simple fridge...

Inverters are not the expensive part of the system--it is the loads that drive the size of the balance of the expensive (panels, battery bank, solar charger, AC backup charger, etc.)...

To automate the switching between utility power and off-grid inverter is done with a "transfer switch"... The transfer switch will connet the loads either to the AC mains or the AC Off-Grid inverter SAFELY.

There are manual T.S. and various types of automated Transfer Switches.

And you can get inverters and inverter/AC chargers that have internal AC Transfer Switches.

You can use an external transfer switch to connect your backup AC genset into your home too... Lots of options.

What is it you are looking for...

=Bill

speedshot

Re: Really new guy

Thank you BB you continue to nail my informational requirements with amazing alacrity. I know these are "baby steps", but you have to crawl...I have an idea for a "Rube Goldbergian" (?) charging device I am going to build. Very much appreciate the emphasis on safety. My sponge is full for now...time to digest!

Thanks
Speedshot

BB.

Re: Really new guy

Speedshot,

To keep things clear in your mind--if you are going for emergency power (i.e, a battery bank)--think of the battery as the heart of the system and everything else hangs off of it...

Size the battery bank for your load requirements. Then sized the solar panels to keep up with charging the battery bank (i.e., replacing the energy taken from the bank by your loads). The solar charging is one type of charger; and you have the option of an AC generator driving an AC to DC battery charger (or even surplus DC gensets from the military/telcom industry, etc.).

As a first aproximation--design your loads/inverters to run from the battery. Then design and wire charger 1 to the battery bus bars, then charger 2, etc.

Each set of wires/cables going to (or from) the battery bank shoud be protected by an appropriate sized fuse/breaker. For some loads, like an Inverter... You may wish to use a breaker and/or fuse+heavy duty switch to turn off the inverter when not needed.

There are a few rules of thumb when sizing stuff;.. But the are staring points to make initial sizing easier and can be adjusted for other good reasons.

The loads are key... They drive everything else. And the battery is what you have to "take care of"--improper charging or too much loading will kill them relatively quickly (in weeks or months)...

-Bill

speedshot

Re: Really new guy

Bill,

Reader's Digest condensed version, Fridge is 6.5 Amps @120 volts. My pitiful math says 780 watts (?). Inverter is the Harbor Freight special 2000/4000 Chicago (China) Electric, batteries two Champion 31C (925 CCA). The fog has cleared enough to see I don't have the panels to keep this charged. The run from the panels will be 50'+/. I need to prioritize my expenditures very carefully, so I guess the question is, where to from here? Sounds like a better charge controller is in order to get the most from the panels I have. Or maybe I'll build a bike generator and tell all 6 (!) of my kids it's time to ride to play their video games!

Thanks,
Ted

Photowhit

Re: Really new guy

About that long run...

If you can create a berm shelter, kinda a hill around the batteries to keep them cool, I'd recomend placing the charge controller and batteries and inverter under the panels.

Even without the berm shelter if you can keep them in a box in the shade of the panels you might be OK, the trick is that heat shortens the life of batteries, (seperate area for Charge controler and inverter as they may spark and they warm up a bit)

Run AC the 50', BTW I still use the 50' shore line to run electric to my cabin in Missouri, just another thing I haven't gotten around to..., see if you can find an old shore line (what people use to run electric to their boats) they tend to be heavy lines mine's just 10 gauge some run heavier! (mines under 5 inches of snow right now)

HB has cheap 12 gauge extention cords but a shoreline is designed to live outside in harsh salt air.

BB.

Re: Really new guy

Ted,

Unfortunately, it is not that easy... What you really need is a Kill-a-Watt meter -- good for both measuring watt*hours for estimating your emergency power use--but also good to use around the home and nail down where all of your electricity/$$$ is going.

You have to measure peak load (for the fridge, the starting load--kill-a-watt is not fast enough for that), average load (modern energy star fridge may be around 120 watts for the compressor, and another 500 watts for the defrost heaters), and total energy used--such as in 24 hours. For example, a fridge will run for 30 min on, 30 min off:

• 120 watts * 24 hours per day * 50% duty cycle = 1,440 Whrs per day = 1.44 kWHrs per day

The problem with using a DVM to measure voltage and current (I guess that is what you did for 6.5 amps)--Is that for AC you have to worry about the phase relationship between the voltage sine wave and the current sign wave... Basically, inductive loads like a motor tend to draw their current "out of phase" with the voltage wave form (current lags voltage). That is represented by Cosine (Degrees) of phase lag of the current.

If your remember your physics--Voltage and Current are really "vector quantities" and you need both amplitude and direction to "do the math".

What happens, it looks like you may be drawing more power than you really are... It is sort of like pulling a car with a rope. If you stand in front of the car, all of your strength goes into pulling the rope in the direction of travel. If you pull from 45 degrees, only a part of your force goes in pulling the car forward. The rest goes into pulling the car side wise to travel--which does no work at all (but you still need a stronger rope).

The Cosine (phase angle) is also known as the Power Factor.

For older refrigerators, the Power Factor may equal 0.65 -- So what you think is power may be:

• Power = Voltage * Current (the "usual" power equation)
• Power = Voltage * Current * Cos (phase angle) ("real" power equation
• Power = Voltage * Current * Power Factor ("real" power equation)
• 120 volts * 6.5 amps = 780 VA (Volt Amps)
• 120 volts * 6.5 amps * 0.65 = 507 watts

You need to know watts to plan how much energy you are taking from the battery bank.

And you need to know VA (Volt Amps) to size the inverter and generator.

The battery "feels" the Watts as power it needs to supply. The wiring/inverter/genset behaves according the the VA (really the current--in phase or out of phase current still can heat the wire and pop fuses).

Any way--not knowing you refrigerator--I don't know if you have a very large fridge that will take a lot of power; or a fridge that happen to turn on its defrost heaters when you did your power measurements, or if it has poor power factor.

If it is an older fridge (10-20 years old or more)--they can really suck down the energy in a home. A good reason to put it on a Kill-a-Watt meter to see if it needs replacing with a more energy efficient unit.

I know you are joking about the bike generator--but before you do something terrible to your kids--at best they will only be able to output 50-100 watts for 20-40 minutes at best... Not very much useful energy (yes--we have been asked that question before).

Regarding the Inverter... That is probably a MSW inverter (Modified Square/Sine Wave Inverter)... Basically, a square wave is fed to your 120 VAC 60 Hz devices... About 80% of the items will work fine. And about 10% may die an early death (small wall wart transformers, some small AC power bricks for appliances, some motors--i.e., some refrigerators, etc.).

True Sine Wave Inverters are more expensive--but for long term use (cabin, off grid home, etc.)--highly recommended. Some folks use a big and cheap MSW for well pump. And a smaller but expensive TSW for home electronics...

All About Inverters
Choosing an inverter for water pumping

Lastly--you have a fairly long run of 50' from the panels to the charger/battery shed. For longer distances (especially for 12 volt battery banks)--you need a MPPT type charge controller (nicer but more expensive than a PWM type solar charge controller). It lets you run up to Vmp=100 volts for the panel to shed run. And efficiently down convert to charge the battery bank.

All About Charge Controllers
Read this page about power tracking controllers

My recommendations:

1. Measure/Estimate your daily minimum loads. For now, assume 400-800 watt average 15 hours per day (fridge, lights, radio, tv).
2. Get a Honda eu2000i 1,600 watt Inverter/Generator (quiet and fuel efficient). If 400 watt load 15 hours per day--plan on 1-2 gallons of fuel per day (use fuel stabilizer for 6-12 fuel storage). 2 weeks = 14-30 gallons of fuel storage.
3. If you have a well pump--get a cheap 5kW genset to fill holding tank and only run when water is needed (noisy, sucks fuel).
4. Next, get a battery bank and good AC battery charger to run your loads. Run the generator to charge the bank during the day. Run the inverter/battery at night for light loads.
5. Then--get solar panels to charge the battery bank... You don't have to get all the panels at once--but the more you get, the less fuel you will burn.

Problem is that solar power only makes/saves you money if you use it 9 months out of the year... An off-grid emergency power system is sort of a waste--except those few days/weeks of the year when it really is nice

But--a fuel efficient genset and stored fuel is probably more cost effective.

Then you look at a Hybrid GT system (inverter with both Grid Tied and Off Grid capabilities). The Xantrex XW system is very nice... But you are looknig at just $3,000 for the Hybrid Inverter/Charger. Add a good sized battery bank and genset. Then add solar panels and charge controller... Not cheap.

The GT connection allows to use your solar power "cheaply" and efficiently all year round (if utility allows 1 year net metering) and can provide power when the grid is down in an emergency (giant solar powered UPS).

If you have propane or can store diesel--and use more power (say want to run AC)--then you really should look at alternative fueled Prime Power gensets (probably 6kW and above). These will also work well with the Xantrex XW Hybrid inverter nicely too (with or without solar array).

In the end--your power needs and free cash are doing to tell you what is most cost effective for you.

-Bill

n3qik

Re: Really new guy

speedshot wrote: »

batteries two Champion 31C (925 CCA).

Did a quick search, the only thing that I found was that these are for Mack trucks.

I guessing they are starter batteries.