solar setup

rudybell

hello 
i have a very good roof to instal solar
actually i can instal 57 solar panels so 17kw
i want to be 100% independant
i'm gonna instal a heat pump for my pool
i wondering wich kind of battery bank do i need
i'm planning to instal 57 REC solar panel and 2 solaredge inverter

somebody can help to understand the best option to be 100% efficient

mvas

rudybell said:

i'm gonna install a heat pump for my pool
somebody can help to understand the best option to be 100% efficient

You can start here ...
Determine how many kilowatt-hours your heat pump will consume each day?

Photowhit

You don't start with, I'll install all I can and it'll be enough, start with how much energy you use!

I take it you are currently connected to the grid? Your statement should tell you how many KWh's you use each month. Better yet get a print out of how much energy you use each month. You may be able to do this online.

Understand that 'off-grid' electric will almost certainly be much more expensive than the grid electric! Also understand that you are talking about a huge system! It will likely require some very large 2 volt cells, or 2 or more large forklift batteries!

Photowhit

I went to check out the Solar Edge inverters, it appears they are designed for grid tied system? Do you intend to be Independent of the grid?

BB.

Just to give you an idea of what is possible with Grid Tied solar. Guessing a fixed array in Mesa AZ tilted 33 degress from Horizontal
http://www.solarelectricityhandbook.com/solar-irradiance.html

Mesa
Average Solar Insolation figures

Measured in kWh/m2/day onto a solar panel set at a 57° angle from vertical:
(For best year-round performance)

Jan	Feb	Mar	Apr	May	Jun
4.94	5.55	6.48	7.10	7.03	6.76
Jul	Aug	Sep	Oct	Nov	Dec
6.21	6.01	6.39	6.02	5.35	4.78

If you have a 17 kWatt array:

• 17,000 Watt array * 0.77 panel+controller deratings * 5.0 hours per day sun (winter typical) = 65,450 WH per day = 65 kWH per day (~1,964 kWH per month)
  
• 17,000 Watt array * 0.77 panel+controller deratings * 6.0 hours per day sun (summer typical) = 78,540 WH per day = 79 kWH per day (2,356 kWH per month)
  

Now--The details matter. You need to check with your power company and see what plans they allow for Grid Tied solar power... More and more, utilities are starting to push back on what where, customer friendly (i.e., subsidized) billing plans--And more and more to less friendly plans (pay you $0.05 per kWH and charge you $0.10 to $0.20 per kWH). And in some cases, making GT systems all but illegal. Also, many companies have a break point at ~10 kWatt solar array--Over 10 kW, may be a commercial install that have other requirements.

And, GT solar systems (in general) do not supply emergency/backup power. If your utility power fails (car hits pole, wind blows down power lines), GT solar power will turn off too.

If you wanted a battery backed power system with a 17 kWatt array. You would probably need around a 6-16 kWatt AC inverter, and a battery bank of:

• 17,000 Watt array * 0.77 panel+controller derating * 1/48 volt battery bank * 1/0.10 typical rate of charge = 2,727 AH @ 48 volt battery bank

Or roughly 2 strings of 24x 2volt cells like this (48 batteries total):

Surrette Battery - 2 Volts, 1300 Amp-hours $454.00 each

Voltage			2 Volts
Series			4000
Ampere Hours @ 20 Hour Rate			1300 Ah
Weight			125 lb / 56.70 kg

And a typical design of 2 days of stored energy and 50% maximum discharge (i.e., power failure and stormy weather):

• 2,600 AH * 48 volts * 0.85 AC inverter eff * 1/2 days storage * 0.50 maximum discharge = 26,520 Watt*Hours per day ~ 27 kWH per day (equivalent to ~796 kWH per month)

And the daily power output from an off grid system would be:

• 17,000 Watt array * 0.52 typical off grid system eff * 5.0 hours of sun minimum per day = 44,200 WH per day ~ 44 kWH per day (~1,326 kWH per month)
  

My first suggestion--Do not purchase any solar equipment yet. Wait until you understand your loads/energy needs and do a couple paper designs for your system first (and check out what is allowed by your utility and city).

Second, I would get a whole house energy monitoring system--Something like this:
http://www.theenergydetective.com/

In general, you are probably paying around $0.10 to $0.20 per kWH -- It is not unusual for somebody to pay (all costs, battery/equipment maintenance/replacements) closer to $1 to $2 per kWH (you may get as low as $0.50 per kWH if you get good prices and very closely manage your loads--And do not have any "oops" that kill a battery bank).

My suggestion--First do all you can with conservation. Lots of insulation in the attic and walls, Energy Star rated A/C and heating systems, look at heat pump water heater(s), Energy efficient appliances (refrigerator/freezers, TV/electronics, LED lighting, etc.). Shading of windows from summer sun, use solar thermal for pool heating. Multi-speed pool pump (most pumps are larger than needed for general circulation).

If you end up with a very well sealed home, look at an HVR or EVR energy recovery system:

http://www.greenbuildingadvisor.com/blogs/dept/musings/hrv-or-erv

In general, it is almost always more expensive to generate electricity than it is to conserve it.

For an older home that nobody has worked at conserving--It is possible to save upwards of 50% off your electric/utility bill. Newer homes that already have lots of insulation and you do not "waste" power--25% is probably still doable.

Energy usage is a highly personal set of choices... What works for me in a mild climate may not work for you in high desert.

-Bill

Estragon

If the heat pump is for pool heat, using part of the roof for solar thermal collectors would likely be cheaper and more space efficient than pv. You could still do pv for circ pump and other loads.