1 kw solar panels

Re: 1 kw solar panels

Just to give you some numbers to hang your hat on...

I like to start with the battery as the "heart" of your system. Generally 5% to 13% rate of charge from your solar array to the battery bank is a good range. If the system is used lightly (weekends, summer evenings, etc.), then 5% rate of charge can work. If the system is used heavily, then you should be looking at a 10-13% or so rate of charge (less baby sitting of loads vs sun, quicker to recharge next sunny day, etc.).

So, for a 10% rate of charge with 1,000 watts of panels using other rules of thumbs:

• 1,000 Watt array * 0.77 panel+controller derating * 1/0.10 rate of charge * 1/14.5 volt battery charging = 531 AH @ 12 volt battery bank

Of course, if you chose a 24 volt battery bank, you would have ~266 AH @ 24 volt battery bank. Same energy storage, roughly the same costs, just at 24 volt DC (and 1/2 the current) as 12 volt bank.

Now, what does that give you... If you assume 2 days of "no sun" and 50% maximum discharge, then your 120 VAC storage would be:

• 531 AH * 12 volts * 0.85 inverter eff * 1/2 days of storage * 0.50 maximum discharge = 1,354 Watt*Hours = 1.35 kWH per day nominal 120 VAC energy per day available from battery bank

How big of AC inverter... Roughly, C/8 would be a good nominal maximum continuous discharge rage. And C/2.5 would be the recommended maximum surge current (starting well pump, etc.)--This is for a flooded cell battery, but is also very conservative for AGM batteries too. And a "good inverter" can usually surge around 2x its maximum continuous load. So:

• 531 AH * 12 volts * 0.85 inverter eff * 1/8 hour discharge = 677 Watt "nominal maximum" inverter
• 531 AH * 12 volts * 0.85 inverter eff * 1/2.5 hour discharge * 1/2 surge derating = 1,083 Watt "nominal maximum useful" inverter

And how much energy from the solar panels can you get... In much of the US, we get about a minimum of 4 hours of "noon time equivalent sun" per day for ~9 months of the year...

• 1,000 Watt array * 0.52 end to end AC system efficiency * 4 hours of sun per day minimum for nine months of year = 2,080 WH per day ~ 2.1 kWH per day minimum

Now, look at your loads. Do you need 12 VDC or 24 VDC? Do you need AC power, and if so, how much (Kill-a-Watt type energy meter). Does it look like the above system will meet your needs?

Will you need a backup genset + AC charger?

A Honda eu2000i will run a 45 amp or so 12 volt AC Iota charger (22.5 amp or so at 24 VDC battery bank). If you assume a 10% or 20% rate of charge, then:

• 45 amp * 1/0.10 rate of charge = 450 AH @ 12 volt battery bank
• 45 amp * 1/0.20 rate of charge = 225 AH @ 12 volt battery bank

It would be a bit small for a 531 AH battery bank--But if you do not need to use a generator very much and can live with longer generator run time, when needed (typically dark winter days), I probably would still start with the eu2000i and a 45 amp Iota charger.

A 55 amp Iota charger may work--But I would talk with NAWS or ask on the forum if anyone here uses 55 amp 12 volt Iota with their eu2000i.

The above is just a starting point for a suggested design. Check the above against your needs (and wallet) to see if everything will meet your requirements. If not--Then start adjusting (your loads, your solar hardware). It is cheap and easy to do that now on paper -- Vs later when you have the hardware.

-Bill

Re: 1 kw solar panels

Is this the Inteli-power you have?

http://www.progressivedyn.com/prod_details/rv_conv/rv_converter_pd9245c_2.html

I am not sure--I did not see any detailed specifications--But since you have one already--Why not try it and see if it works well for you (monitor battery bank voltage/current when charging, check specific gravity of the battery cells with a hydrometer to see that they are being properly charged, etc.).

Are you going to run this with Utility power or using a generator (brand/model?)?

-Bill

Re: 1 kw solar panels

oadkins wrote: »

What makes the Honda eu2000i better than the same size generic gen.

A standard generator (really a gasoline/fuel combustion engine driving an Alternator) requires the motor+alternator to run at a fixed RPM (3,600 RPM or 1,800 RPM typical for a 60 Hz 120/240 VAC output).

This type of "genset" is simple, cheap, and pretty reliable. However--It does make it less fuel efficient at less than ~50% of rated capacity. Because the genset needs to turn at a fixed RPM (to maintain 60 Hz)--At less than 50% of rated output, fuel flow (gallons per hour, etc.) remains about the same (down to zero power output).

The Honda and other "inverter/generators" use a "wild frequency" alternator. Basically, the Engine RPM is no longer fixed at 3,600 RPM, but can go faster or slower--And the Wild AC is sent to an internal AC inverter that converts the variable frequency/voltage to 120 VAC @ 60 Hz power.

At lower power usage (1/4 power or so), the generator can run much slower, quieter, and more fuel efficiently. At >50% rated power, the advantages of the inverter/generator are not really that much.

Drawback is that at low RPM (1/4 or less), the genset does not have much "surge capacity" and if you throw a heavy load on the generator, it may take a few seconds to increase engine RPM to support full rated output (they have an "ECO Throttle" switch so you can run the Genset at full RPM for heavy/surging loads.

The Honda and Yamaha inverter generators tend to be quieter (more baffling) and pretty rugged/reliable units if you change the oil and perform recommended maintenance. There are some folks here that are running the Honda eu2000i generators around 6,000 hours now. >2,000 hours should be pretty common. A lot of the "cheap and noisy" gensets have problems making it past 100-500 hours before something breaks.

The Honda eu family generators are not really worth rebuilding when they wear out or something major breaks (they are designed to be inexpensive).

Battery Charging can be very hard on generators... It is pretty easy to load up a genset with a fixed load from the battery charger and run it for 3-8 hours at near rated output (deep discharged large battery bank will draw constant current from AC battery charger for many hours). Most non-commercial generators are designed to run residential loads which tend to be fairly light loads with occasional surge current (starting refrigerator, compressors, well pumps, etc.). Running non-commercial generators at over ~80% of rated output for many hours--They can have cooling/overheating problems in the engine and/or alternator+AC wiring.

For smaller power needs--The inverter-generators can be more nice and fuel efficient. And many people still have a 5kWatt or larger genset to run the shop loads, well pump, etc. for limited time.

Running a genset that will go ~4-9+ hours while outputting 400-1,600 Watts (enough to run a home in an emergency, or recharge a smaller battery bank), vs running a 7kWatt genset that will drink around a 1/2 to 1 gallon of fuel per power.

If you need 3.5 to 7 kWatts of power, then a 7 kW genset may be the solution. But if you only store 10-20 gallons of gasoline for emergency power--The Honda can give you 5-20 days of emergency power. The 7kW will go through that amount of fuel in 1-2 days (then what--Does the local gas station have power? Does it have fuel? Can it get get deliveries, etc.).

-Bill