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The more I think about it, the more I like the idea of ground mounting solar panels.

The two major benefits of ground mounting are optimal tilt / adjustable tilt and ease of maintenance. The only drawbacks I can see are space and cost.

Personally, ground installation wins hands down becuase I could do most of the work. (This negates the cost issue.) Here is a great link to someone who did just that. His total cost was $6500 for a 2150 Watt array, Installed! I too would go the route of wooden frame. I think a solar pergola would be great!

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In case you did not know, I live in Indiana. Not really the sunshine state but we do alright. I was surfing the web and landed on a local COOP page. Hoosier Electric. They have a few solar sites in central Indiana. One is only 15 miles away. (I will have to visit this sometime soon).

Franklin, IN has a 3kW solar installation.

Dubois County, IN has the same 3kW solar installation.

I have been looking at the historical data from the site. Man, do the numbers look good. To get us on the same page, here are two “as perfect” (very sunny days) at two very different times.

Solar output on December 22nd

Solar output on December 22nd

Victory Solar output on June 29th

Solar output on June 29th

Total output for December 22nd was 18.86kW

Total output for June 29th was 20.83kW

The difference is only 2kW yet the total number of hours the sun is above the horizon being 6 hours longer for June! Don’t forget the more direct path thru the atmosphere too.

So what is going on. We know that temperature is a big factor. Also, with that, these panels are pole mounted. No heat trapping roof to slow down the air cooling of the panels. Even still there is something else. These panels are special. Sanyo Bifacial Solar Panels! They convert light into electricity from both sides of the panel! This means if there is snow on the ground the reflected light up into the panels will be converted. Now I am not thinking about putting panels on my roof but instead placing them on my south facing hill. With some white stone underneath I may be able to make this work! I will have to see if I can get some more data. I know the company that installed both locations. 🙂

What is the “edge-of-cloud effect” and how can it cause a solar array issues?

What is it? Well, just as the cloud begins to cover the sun or when the sun is emerging from behind a cloud, there is a sudden burst of energy that produces more power than normal. This is caused by light refraction. Refraction can concentrate the sunlight while the edge of the shadow passes by. The result is a boost in module voltage output. On a day with bright blue skies and fair weather cumulus clouds, the effect is quite noticeable.

So how can you account for this increase in output. Common practice is to add 20% to 25% to the amperage rating of the solar controller. But many controllers today are the MPPT type. They track the arrays Maximum Power Point on its IV curve. As the edge of clouds start causing over-irradiatance. The MPP voltage starts to rise, so too, does the current. The MPPT controller then adjusts the voltage up to correct for this effect.

Take for example a Sunny Boy 5000 Watt grid-tie inverter. The lower the voltage of the array the better the efficiency. Of course the design of an array depends on the solar panels but you should never design around the highest voltage under standard conditions. In this case 480 VDC. Me, I would design around 350VDC to 400VDC under normal operating conditions. This would allow for the MPP to move around where it wants to.

Basically, solar controller can handle brief overages of current, but not voltage. The edge-of-cloud effect is only going to be a problem when it is very cold outside and passing clouds. You can use this sizing tool for SMA Sunny Boy Products. Also, solar panels have a Voc (open circuit) and a Vmp (max power). for a 12VDC panel Vmp may actually be 17VDC and Voc around 21VDC. Since the edge-of-cloud effect normally occurs when the inverter or controller is running you already have some extra wiggle room.

(I guess you could have a rolling black during the day and have your grid-tie inverter shut-off. But then you would also have to have record cold temperatures. But then it would be winter and you would have less transmitted light because it has to travel though more atmosphere at an oblique angle. Plus you would have to have perfectly clean panels. As you can see, not likely to happen any time soon.)

I work with the Solar Power Forum quite a bit. Here lately, many people have asked about making solar panels. While this sounds like a fun project, it will not save you very much money.(If any)

You can buy solar cells from eBay for $2 a watt. This is only get you the material for the solar part of the panel not the frame, glass, bypass diode, or junction box. If you estimate this costs $50 for a 200 Watt panel, then you are up to a $2.25 per Watt.

Since you made these panel and they will not be UL listed you will not be able to do a grid-tie system. They will not have a warranty. And, you don’t have a warranty on power output. You can still use them for an off-grid system. But, if you mount them to your roof will your insurance company still cover them or your house if they caused a fire for some reason. I think not.

I know of a few places that sell blemished solar panels from Evergreen Solar for under $3 a Watt. You get a full power and manufactures warranty. And they are UL listed so you can claim the FEDERAL TAX CREDIT OF 30%. (USA only) If you use $3 a watt with a 30% credit, you get $2.10 a Watt. Now that cost less then making them yourself.

Don’t waste your time trying to make solar panels. Just buy them. Of coarse you could always just buy brand new Solar Panels . Then you would have full support from the manufacture and the dealer.

North American Board of Certified Energy Practitioners (NABCEP of short), they currently offer a solar PV certification and a solar thermal certification. Soon they will offer a small wind certification. So the question is; if I get one or both of the certification will companies call me with jobs? Currently, Indiana only has five people with either certification. One, person has both. To sit for the exam it costs $400, this includes a application fee of $100.

Disclaimer: NABCEP certification is not a professional license issued by a government agency, and does not authorize a certificant to practice. NABCEP certificants must comply with all legal requirements related to practice, including licensing laws.

This sounds like most other certification boards I know of. No big deal there.

Objectives and Task Analysis for the Solar Photovoltaic System Installer, this is where the rubber meets the road. After looking over the testing requirements, it does not seem be too difficult. Of coarse I would study up on a few areas but overall I feel good about the material.

Requirements/Education, this is where I will run into some issues. Indiana is not know for solar installations. I have the education part covered under subsection e. But, the experience will be a problem. It is a great example of the chicken and the egg scenario.

I do know one of the people in Indiana that has his NABCEP solar PV cert. I think I will send him an email and ask a few more question about the cert. i.e. How difficult was the test! Maybe he can help me with the solar installation part.

So I have an interesting idea. Instead of a huge 5k Watt solar system, what about something smaller. Say a 1000 Watt system. That would only be 5 panels on my roof. I could still get a large inverter and have a medium sized battery bank for backup power. Currently, I have 6 UPS (uninterpreted power supplies). That right I have six.  Each unit uses about 15-20 Watts all dat everyday. I figure that this is about 100 Watts per hour. 24/7 for an entire month is 72kWhrs. Does not seem like much but it is 10% of my “off-season” average. (By off-season I mean no AC or Heat.)

If I subtract the 2.4kWhrs I waste every day from my TED average daily usage I get some thing like 18kWhrs. If the power was out in the neighbourhood and the family watched there usage very close, (Okay, Okay, If I was a drill Sargent!) this number would be much smaller. Since virtually all the lights are CFLs the light load is very small. Then you would have a refrigerator and microwave to worry about. By my estimates I would be looking at 5kWhrs. (Cooking would mainly be done on the LPG Grill.)

What am I thinking? Well, first I was thinking about using Xantrex XW components. I would want to get a XW6048 so all I would need to do in the future to expand is add more panels. I would need an XW solar charge controller. 5 Evergreen solar panel (200W each) 8 Trojan L16 batteries. Installation hardware and Presto! Back-up power. If it was only that easy.

Cost:

Inverter – $3500
Solar charger – $550
Solar Panels – $5500
Batteries – $3000
Shipping – +10%
Installation “Stuff” – +15%
Total = $15600

Don’t forget the federal rebate! (This is the reason for the solar panels in the first place, you don’t have to have them. But then you would not get the rebate now would you. 🙂

New total is $11000.
Fro my other blog post, I determined that for every Watt on my house I should produce 1.2kWhrs a year. I would have 1200 Watts of Panels, so that would be 1400kWhrs. That would equal $140 a year in savings. But the point of this exercise was to provide backup power not offset my entire usage. Every year for the next four years I could add 5 more panels. The only thing I would need to add is another $550 solar controller. Another nice idea is the inverter charger has a second AC input for a generator. I could get a small generator that would run at full power. This would maximize fuel usage and keep the cost of fuel down. It is better to run a generator at near capacity then it is to run it at 30%.

The dreams continue. I wonder if I could get a deal at solarhome.org?

If I manage to get to below 500kWhrs a month, what would it cost to put solar panels on my roof? Assuming I have enough roof space, the going ball park cost per watt is $8-$10 Watt. According to PVWatts I need about a 5,000 Watt system. PVWatts is a great tool! I will use $9 a Watt. 5000 Watts x $9 x 0.7 (Federal Credit) = $31,500. Think of its as buying as car. But in ten years the car will be worth virtually nothing and the system will still be worth at least half of its installed value. And to top it off the system will be making you money! In my case not as much as some. (My rate is about $0.10 a kWhr.)

PVWatts assumptions.

De rating factor of 0.80
Array Tilt of 45 degrees.
Array Azimuth of 200 degrees. (House does not face due south)

The output from PV Watts is (“Year”, 4.36, 5973, 595.81). The middle number is a yearly output of kWhrs. This number divided by 12 is about 500 kWhrs.

This would be a grid-tie system. So I would not be able to “ride out” a storm with lights if the power fails. The power very rarely goes out, but it would be great if I did not have to worry about outages. But, grid-tie usually yields higher efficiencies. If the state offered some additional incentive I would seriously consider a solar system. The next power reduction upgrade is a new Heat Pump. This will replace the Gas Furnace and the AC unit. I currently have a 80% efficient Gas furnace and a SEER 10 AC unit.

As per a previous blog, I know that the 160 mile battery pack will need about 400kW Hours. This calculation will use the average solar insolation value and power would be supplied through a grid tie system. The 400kW hours was an inflated number to begin with. For a grid tie system, I will use 95% efficiency.
At my location, I have an average of 4.6 sun hours (Latitude -15). I need to make 400kW hours / 0.95 = 420 kW hours. I need to generate (420kW hours / 30 days =)14kW hours a day. What size array do I need? (14kW / 4.6 hours) I need a 3kW array. The generic installed cost is about $8 a watt for a grid tie system. A system would cost me $24,000 installed. Then take 30% off of that in the form of a Federal rebate. You get  $16,800. Not bad. The simple payback would be 47 Years. Maybe if you sized a system for the car and the house, the cost per watt would reduce to a more reasonable number. Say $6 per watt (I laugh to myself and say no way.) Then the cost would be $12,600. Even better! But just remember, this is at today’s energy rates. Who knows what they will be at in the future.

Solar calculators, as I am learning, are all about you typing in all available information you have about your own solar home project, then the calculator will return detailed cost estimate information. Some of them are more generalized to just give you a ballpark price. Others are mind-bogglingly complicated, taking into account your area of residence and what rebates/incentives are available to you and how that will impact the price of your project.

Some will tell you the available sunlight in your area based on your latitude and longitude.

Here are a few we found (there are at least 10 really functional and free solar calculators to be found online):

  1. Solar Water Heating Calculator: Solar water heaters are a great way to get into the solar lifestyle. This tool can tell you how your current heater is performing and whether or not you will save money using solar.
  2. Solar Position and Intensity Calculator: This crazy creation is brought to you buy the National Renewable Energy Laboratory. Given your location, this calculator can show you everything from the time of sunrise and solar elevation to the solar azimuth angle and about 30 other desired outputs.
  3. PV Watts Calcualtor: This is for people who’s current photovoltaic systems are tied into the ‘grid’. Dollar value and energy production are the big draws here. But make sure you know your current cost and have all the system details.
  4. Sun Chart Program: This is from the University of Oregon and can tell you, based on your position, hours of usable daylight for solar power purposes.
  5. Solar Collector Efficiency Calculator: From Build It Solar, this tool does exactly what it says, but be prepared to know the technical details of your system…