Total Solar Solutions

Ok, let’s say you’re interested in installing a solar grid into your home, but you have a moderate budget.  To begin with, you may only want to initially spend what you pay for power on an annual basis.  For my three-level townhouse, I was paying on average $125 per month to the power company, which works out to $1500 per year.  So, what can $1500 get you?

To get the most bang for your buck, let’s look in the 50-100Watt category for solar panels.  They’re moderately priced and still practical.  The GEPV-50 50Watt Solar Module, 12VDC will run you about $345 plus shipping. The next higher model is the 100W 12VDC and that one costs about $700.  You’re going to want a decent deep-cycle 12V battery with at least 100Amp Hours of run time, so the Concorde PVX-890T Sun Xtender 12VDC 102Ah is a good choice at $350.  Mind you this is a heavy battery at 62lbs but it’s right in the middle of the range of batteries that Concorde offers.  Next you’ll need a battery charger and an inverter.  12VDC battery chargers are available for about $180 and a 150W inverter can cost as little as $170.  Now you add in all the extras like mounting hardware, cables, etc. and that can run up at least $300.  So….

            Solar Panel:      $700

            Battery             $350

            Charger            $180

            Inverter            $170

            Accessories      $300

            Total Cost       $1700

We’re a little over budget, but not overly so.  You can knock this down by shopping around a little bit, but just be careful not to limit your system too much. 

Now the question is, what can you do with this system? 

Well to start with, the 100W solar panel chosen here has a Vmp (Max Voltage) rating of 16.1VDC which gives you 6.2A output at maximum.  At 12VDC, you’re getting 8.33A, so let’s split the difference and call it 7Amps. At 7Amps it will take about 14.5 hours to fully charge a dead battery of 102AHr.

Wait, 7Amps output looks familiar…oh yes, that was the power requirement we calculated earlier in order to run a laptop for 40 hours a week.  How about that? 

Conclusion:  For about the price of a laptop computer you can buy a solar powered system that will supply enough power for a work week, given a few variables.  Economical?  Some say it is. They say that the amount of carbon emissions saved from something as simple as operating a laptop computer is well worth the cost.  There are a lot of variables in doing these calculations so before you go shopping, really take the time to plan out what it is you want the system to do and also plan in the ability to expand your grid when you have the opportunity in the future.

September 10th, 2008 | Tags: battery, budget, charger, inverter, laptop, power, shopping, solar grid, solar panel, Watts | Category: How to articles | Leave a comment

I’m writing the next article now, it’s going to be about how to get a solar grid started on a budget.  We’ll look at how far you can get on a budget of $1500 and how much power you can get out of that system.  I’m also working on power calculator templates that you can download from the site here and use for free.  They are in Microsoft Excel format.  One will help you figure out the solar panels needed to run a known appliance, and the other will tel you how much power you will create by inputing the traits of the devices in your system.   Check back soon….

September 9th, 2008 | Tags: budget, excel, power | Category: Coming up | Leave a comment

Which is right?  What’s the difference?  Well, first think of each of the solar panels as a battery.  Wiring them in series (or end to end connecting one positive terminal to one negative terminal) will result in more voltage output.  This is the same as putting AA batteries in your camera or flashlight.  The amount of current stays the same as the rating of each battery but you add up the voltage of all batteries and that’s the output. 

Wiring the panels in parallel (connecting all positive terminals together and all negative terminals together) will provide the same voltage output into your battery bank, but will increase the current to equal the sum of all the individual panels.  This way you’re getting more ‘umph’ so to speak into your battery bank at a steady voltage.  So the answer is…Parallel.

Solar panels wired in parallel

September 8th, 2008 | Tags: battery, parallel, series, solar panel, terminals | Category: How to articles | Leave a comment

I thought I’d share here a little information on the characteristics and terminology used when discussing solar panels.  When shopping for solar panels, the characteristics you are usually looking for include the output rating, physical size and weght of the panels. 

As we have discussed in the previous article, the output characteristics you need to know about the panel are the ratings in terms of Watts, Volts and Amps.   Typically you will see Volts abbreviated as VDC or Volts Direct Current.  Sometimes you will see the Volts and Amps abbreviated in different ways for different reasons.  For example, Vmp = Volts at Max Power, and Voc = Volts at Open Circuit.  Also, you will see Amps or current described as Imp for Current at Max Power and Isc for Current at Short Circuit.  In some applications it is important to know these max power ratings.  You may have a device such as a motor of some kind that will, at times, draw more current and require additional power when it’s working hard.  Therefore, you will need to know if your solar panel is capable of creating enough power for that surge. 

You will typically see solar panels grouped in terms of Watts and Volts.  This is done for convenience sake so you can quickly find the group of panels you need to match the power requirements of your grid and to match the input requirements of your batteries.  Once you find the group of panels that fit your needs, then you can look to the differences in size, weight and of course cost.   Hope this helps!

September 8th, 2008 | Tags: amps, power ratings, solar panel, vdc, volts, Watts | Category: How to articles | Leave a comment

Step 1 Calculate your power loads (Power used by your appliances). 

Determine the amount of watts of power that each appliance requires for its use.  In this example, we’ll use a laptop computer.  My Dell laptop here says on the sticker on the back 19.5Volts, 4.62Amps.  Do the little math here using the formula provided earlier and you get a power requirement of about 90Watts (per hour) of power.

Next determine the amount of hours per week you’ll want to run the appliance.  Let’s call it 5 hours per day of use for the laptop, times seven days per week is 35 hours per week.  Round it up to 40 hours just to be sure and multiply that times the amount of Watts per hour from earlier and you get 3600Watts/week of power required for the laptop.

Step 2 Select a Power Inverter

As we talked about before, you have to work backwards in creating your power grid.  So the next step back is the power inverter.  This is the unit that converts DC power into AC power.  They are rated in terms of Watts of output as well as Volts DC input.  For this example, a 12V DC battery will be supplying power and we’ll need to convert it to 110V AC.  Our laptop here will need at least 3600Watts of continuous power per week and 90 Watts of power per hour.

Step 3 Determine your battery bank size

Next determine the size and number of batteries needed for your system.  Most batteries are rated in terms of volts DC and Amp hours (length of time to discharge the battery’s power).  To calculate the optimum battery needed follow these quick steps:

1         Find the Amp hours per day needed by your system.  This is the 3600Watts / week divided by 12VDC = 300Amp Hrs per week.  Divide this by 7 days and you get 42.8 Amp hrs per day.

2         Multiply 42.8 Amp hours per day by the number of cloudy days per week in your area.  Let’s call it three, so 3 cloudy days X 42.8Amp hrs per day = 128.4 Amp Hrs per day

3         Divide that number by .8 to leave an extra 20% margin of power in the battery and you get about 160 Amp hrs per day.  This is the approximate optimum rating of the total battery bank you will need. 

4         You can now use this number to determine the amount of batteries you will need in the system.  If you select a battery that has an output rating of 100 Amp hours per day, divide this into the final number from step 3 and you get 1.6 – round that up to 2 and you now know you need two batteries.  On the other hand if your selected battery is rated at 200 Amp hours per day, you will only need that one battery.

Step 4  Find the right Solar Panels

Now let’s determine the output requirements for your solar panels:

1         Start again with the Amp hours per day needed by your system, in this case 42.8 Amps per day.

2         Then calculate:  (Amps hours per day  X  1.2 (for battery loss) ) /  Average # of sunny hours per day  =  Total Solar Array Amps required.  In this example we’ll assume 7 hours of sun so we come up with a total of 7.33Amps output required by our solar panel. 

With this information we can search for a panel.  Sometimes they are listed or categorized in terms of Watts (7.33Amps X 12VDC = about 88Watts).  Panels with this output can range in price from $300 to $600 depending on the brand. 

Now that we’ve done the math, next step is to go price shopping and develop out budget.  That’s coming up next!

August 27th, 2008 | Tags: amps, batteries, calculations, inverter, solar grid, solar power, Watts | Category: How to articles | Leave a comment

August 26th, 2008 | Category: Uncategorized | Leave a comment

Ok, so you want to install some solar panels on your home to provide electricity in some way, but you don’t know where to start.  Ironically, you have to think backwards to come up with your solution.  By this, I mean first you have to determine the purpose behind using the solar power in your home/RV/Boat.  What is it that you want to power?  Is it just the kitchen appliances, or your home computer, or maybe just the outdoor equipment such as your pool or sprinkler system? 

Once you quantify this, you do the calculations to determine the power requirements in Watts.  Yes, you have to do a little math, but don’t worry, it’s very easy.  Here’s the one formula you need to know:                      

Watts  =  Volts  X  Amps

Said another way:         Volts  =  Watts  /  Amps             or:                Amps   =  Watts  /  Volts

Later on we’ll go through some examples in suing these formulas.

Another question you’ll have to ask yourself too is this; do you want a constant, steady supply of power or will you just need the short time use of the system?  This will determine if you need to charge one or more batteries or if you can simply plug the solar panel directly into your appliance.  Making use of batteries will cost you more obviously, but it is the most practical way to use solar power which obviously can only be harvested during the day.

If you use a battery bank there are some other pieces of equipment you’ll need of course.  The solar panel(s) will connect to your battery.  To better take care of your battery and prolong its life, it’s a good idea to install a charging unit between the solar panel and the battery.  The battery will output an average of 12VDC, but you may need to convert this to 110V AC for your needs.  To do this you need something called a power inverter.  This converts DC power to AC and you can usually plug your appliances or extension cords directly into them.  The small ones start out cheap, about $35 or so and go on up in price from there. 

Depending on the size of your power grid you may want to install some safeguards such as those in your home now…fuses and breakers that work to protect your appliances from burning up.  Finally you’ll need to run the power cables wherever necessary.  Make sure you get the right size cable for the job.  Grab your tape measure and start determining in feet/yards how much cable you’ll need.

Whether or not you end up doing the work here yourself to install your system, at least you will understand how it works, its limitations and what it will cost.  In the next article we’ll go through a couple of examples to determine the right equipment for you and then figure out its cost.

August 22nd, 2008 | Tags: battery, grid, power, power inverter, RV, solar home, solar power, Watts | Category: How to articles | Leave a comment