PV - Batteries - DC generator coupling for islanded operation

Hi everybody!
Planning to build a house with no grid connection and an LPG tank for heating, HDW, cooking purposes and a small DC air conditioning system for modest day use (house internal layer has high heat retention rate) during 1 - 1,5 month a year.
I wonder if it's possible to connect to the PV - Charge controller - Batteries system a DC generator (like www.alpha.com/index.php/outside-plant-power/generators/item/alphagen-dcx-3000 or www.whisperpower.com/4/2/285/products/generators-(programmable-rpm)/dc-generator-24v-300a-mobile.html). Without taking into consideration the specific size of PV system, battery system and loads (planning to adjust the PV and Battery system capacities according to needs cause I have the possibility to order them quickly.
The question is how to connect such (or any other) DC generator (variable speed permanent magnet) to the the DC bus bar and what components would I need (apart PV, battery set, inverter and generator)for following scenarios:
1. charge the battery bank only;
2. charge the battery bank and power the load through the PV inverter at the same time;
3. power excessive load with the battery bank in parallel.
The priority list:
1. keep the batteries charging cycles correctly in order to maximize the their life cycle;
2. have the possibility power the peak loads at any time.
I wonder if this is a feasible system?
Any help would be desirable
Planning to build a house with no grid connection and an LPG tank for heating, HDW, cooking purposes and a small DC air conditioning system for modest day use (house internal layer has high heat retention rate) during 1 - 1,5 month a year.
I wonder if it's possible to connect to the PV - Charge controller - Batteries system a DC generator (like www.alpha.com/index.php/outside-plant-power/generators/item/alphagen-dcx-3000 or www.whisperpower.com/4/2/285/products/generators-(programmable-rpm)/dc-generator-24v-300a-mobile.html). Without taking into consideration the specific size of PV system, battery system and loads (planning to adjust the PV and Battery system capacities according to needs cause I have the possibility to order them quickly.
The question is how to connect such (or any other) DC generator (variable speed permanent magnet) to the the DC bus bar and what components would I need (apart PV, battery set, inverter and generator)for following scenarios:
1. charge the battery bank only;
2. charge the battery bank and power the load through the PV inverter at the same time;
3. power excessive load with the battery bank in parallel.
The priority list:
1. keep the batteries charging cycles correctly in order to maximize the their life cycle;
2. have the possibility power the peak loads at any time.
I wonder if this is a feasible system?
Any help would be desirable
Comments
What is the AC inverter you are using, does it not include a AC/Gen powered charger ?
|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
If you have a 24 volt system I would say just get the 24v generator and hook it directly up to the bank that way you can take care of bulk charging. A simple generator isn't going to provide full range battery maintenance but it will keep the batteries charged.
Solar hybrid gasoline generator, 7kw gas, 180 watts of solar, Morningstar 15 amp MPPT, group 31 AGM, 900 watt kisae inverter.
Solar roof top GMC suburban, a normal 3/4 ton suburban with 180 watts of panels on the roof and 10 amp genasun MPPT, 2000w samlex pure sine wave inverter, 12v gast and ARB air compressors.
And here is the solar radiation for Almaty Kazakhstan:
http://solarelectricityhandbook.com/solar-irradiance.html
Almaty
Measured in kWh/m2/day onto a solar panel set at a 47° angle from vertical:Average Solar Insolation figures
(For best year-round performance)
-Bill
Planning to buy 72 cell modules of 300 Wp, starting with 10-12 modules in parallel and battery lead acid flooded batteries of 12 or even 6V connected in series of 48V, with total capacity of 150-160Ah. To the average DoD of 50%.
mike95490 What the arc you mean - do you mean start surge? I hove to study if that is the problem.
Looking for a simple 6kW china made inverter and to cuople the DC generator with the DC bus bar. No battery charging function.
Instead to use a separate DC-DC charger.
Thank you Bill for the information, I got some historical data on radiation from local weather station, perhaps for the horizontal surface and no information on measuring unit calibration, cleaning etc.
Question still open:
Is this a feasible system?
What components would I need (apart PV, battery set, inverter and generator)?
What kind of issues can arise during the operation?
Thanks for any info/help.
In general, no, the system you have proposed is probably not feasible (i.e., it will not function to the "capabilities" of the various pieces.
In some ways, with specialized batteries (like LiFePO4 or other Li Ion type), you could get some higher surge power from a small battery bank--but for most homes, this is not how a system would operate (6 kWatts, then shutdown from dead batteries in 30 minutes).
Mike is probably talking about your usage of DC gensets and switches... DC current is much more difficult to switch without drawing large arcs. DC arc welders are common for a reason--They are great at making sustained arcs.
This is a neat example where you have everything identical except one example with AC power and the second with a rectifier and DC power through the switch instead.
In any case, we keep coming back to how much power you need, and how you use it (day/night/shop/home/etc.).
If we use our typical Off Grid cabin/home rule of thumbs... A 160 AH @ 48 volt battery bank would be good for:
- 1,600 Watt AC inverter
- 3,200 Watt Surge (starting well pump as an example)
- 1,600 Watt of Solar Panels (rough maximum recommended)
- 160 AH * 48 volts * 1/20 hour discharge rate * 0.85 inverter efficiency = 326 Watts of AC power for 5 hours per night for 2 nights average load
- 1,600 Watts * 0.52 off grid system eff * 3.5 hours of sun per day = 2,912 Watt*Hours of AC power per "average" day (enough ot run a small, very efficient home--Refrigerator, LED lighting, laptop computer, washing machine, "off grid friendly" well pump, cell phone charging...
Most people when they first get involved in solar/off grid power tend to underestimate their loads and overestimate how much power a pure off grid solar power system and supply (for a "reasonable" amount of money).There are options (common suggestion is a small solar+battery system for overnight lights, computer, cell phone charging, TV, etc. loads) and a generator for daytime loads (washer, well pump to cistern, vacuum cleaner, shop tools, electric cooking appliances, etc.).
I am very "big on":
- Define your loads
- Reduce your loads and go back to one (conservation)
- Paper design of a balanced system (Loads->battery bank; Battery bank->solar array/backup genst/etc.).
- Pick hardware and batteries to support those needs. Estimate total costs. Review #1 and #2 before buying anything
- Buy stuff.
-Bill|| Midnight Classic 200 | 10, Evergreen 200w in a 160VOC array ||
|| VEC1093 12V Charger | Maha C401 aa/aaa Charger | SureSine | Sunsaver MPPT 15A
solar: http://tinyurl.com/LMR-Solar
gen: http://tinyurl.com/LMR-Lister ,
1. I'm I right - the arc problem is not solvable even for 48V system? Consequently is it better (more efficient) to get couple of "genverters" like i2000EU or i3000? Same question: is it possible to use those genverters for charging (through AC/DC charger) and power AC loads at the same time?
2. It is not a problem to increase the 48V battery capacity up to 320 even 400Ah and the PV array to 20-22 units. But I don't wont to get an over-sized system, so the significant part of solar energy will not be used. Is it a stupid idea - to increase the battery system so one part of it could charge other part and work for the load?
3. Regarding loads - I don't have yet exact equipment list with specifications, can enlist common main apparels and differentiate usage time:
regular every day and night use
- home heating and water supply pumps bout 6-8 pieces;
- invertor refrigerator and freezer(trending more for a separate freezing and cold rooms);
- thermo pot, coffee machine;
- kitchen blender;
- multicooker;
- microwave;
- hair dryer;
- 3 TV sets, 2 PCs, Hi-Fi amplifier, LTE modem, phone and tablet chargers.
regular (3-4 times a week) use only sunny days:
- invertor direct drive washing machine;
- iron;
- vacuum cleaner;
- air compressor;
- water pump;
- meat hasher;
not regular (not more than 2 times a month):
- different electric tools.
I know that the total load is very high and some of them has the automatic switching and working regulation, but as I said I'm ready to upgrade the system. Also I think I have to to plan loads connection according to available mount of energy and develop some rules and habits for it.
Last good news I have learned (not yet officially approved) that I can connect to the 10kV grid which is 500m far from my land plot and next year there will be special connection tariffs for farmers (the land has such designated purpose). Regular price is about 800$ per kW + equipment and works. So if the total grid connection budget will economically make sense - I will do it.
Sure it will be more reasonable to have a grid connected PV, battery, generator system, and opt for time differentiated rates. As I calculated the cheapest energy is the night tariff, then the PV energy, then generator energy, then stored energy. Anyway I'm considering the PV-battery-generator system as a pure investment asset (I know that such property will be more attractive on the market).