Solar Off Grid System - Specs

Go to the market place with this specification, looking to install solar + storage of 10-20kW.

+ storage of 10-20kW.

Units gentlemen...kWh

The rating of the panels needs to be 10-20kW. How much storage is up to the original poster.

I would say 20kw should cover it...and 4 days worth of battery storage, depending on the critical nature of the application...

http://www.alibaba.com/showroom/20kw-solar-power-generator.html

Don't skimp on batteries!!! Buy the best you can possibly find. Figure battery costs at 3 x panel costs, minimum. Actually, it doesn't matter whether you buy cheap batteries that have to be replaced every 2-3 years, or high-end batteries that can give you 5-10 years of reliable service (assuming you have them installed in the right environment, and are very conscientious with charging cycle control and battery maintenance over the lifetime of the batteries). Over the life of the system, your batteries are going to cost you about 3 x (minimum) the cost of the panels.

The sun shines 9 hours a day, which means you might get six hours a day of usable power. What is the solar insolation in your location?

You need approximately 20% more charging capacity than the load you will be taking from the system.

You are looking at roughly 130 kW-hr of consumption. You need a minimum of about 155 kW-hours pumped in to your batteries. Let's assume you are fortunate enough to have solar insolation on the order of 300 Watts per meter squared. This suggests a minimum of about 86 meters of panels, with no safety factor to account for cloudy days.

Cloudy days can significantly increase the capacity requirements in most parts of the world (the Sahara, or the Death Valley in California may be exceptions to this). If you expect 20% cloudy days, then multiply everything by 1.3. Unless, of course, you can tolerate some down time with your air conditioning systems.

Assuming you can buy panels at about $100 per meter squared (about what we pay locally), you are looking at a minimum of $8,600 worth of panels. Adding the cost of the batteries, you are looking at about $34,000 for a bare-bones system, with maybe another 10% for electronics. Say $40,000 for a bare-bones system that will give you about 20 years of service, more or less.

Yes, these are back-of-the-envelope calculations, but I have found they are within 10% of the actual cost of a system. Depending on where you are located, you may find some variation due to market factors.

Now, compare this to the cost of a 10kW diesel generator, and the cost of fuel over the life of the project (be sure to include the cost of delivering the fuel to the site, which can be a significant cost factor). You might understand why solar has such a problem competing with diesel powered generators in off-grid situations.

PFR-

Seems our responses are pretty complimentary- my "back of the envelop" numbers are pretty close to yours...

It just occurred to me that you possibly meant Peak load, not daily load, which is useful for equipment spec (you must be able to deliver peak loads, but not useful for system sizing. Have you built a consumption model to come up with daily watts required, and is that 5380?