Generating electricity from the sun. .
Buying PV panels
My expectation is that the cost of Photovoltaic panels will come down over the next few years when the Chinese ramp up production. I may well buy them direct from China and arrange my own container shipping. Eg Trina Solar
What would be nice is if someone comes up with solar roof tiles that
Rebates and tax credits
To help with the up-front capital costs there are some federal and some local state incentives. You can find what's available in your state at http://www.dsireusa.org/ .
Selling electricity to the grid
It's nice to make your electricity meter run backwards and get a monthly check from the electricity company.
Standing-seam solar metal roofing
I care a lot about not messing up the look of the house. I want the roof to be completely uniform in appearance. That means if using solar on the roof that it has to cover the complete rood including all the way to the edges.
Solar film can be added to standard metal standing seam roofing strips.
$200 per panel 19' long
Flexible Thin Film Solar Panels. 128 watt Solar Panel Laminate 24 volt
Unfortunately Unisolar has gone out of business.
1) The efficiency of peal and stick is not as good as a dedicated panel.
2) They are only rated to last 20 years and will be a nightmare to replace as they are permanently glued to the metal of the roof.
3) Not much if any color choice.
4) They are not made in China so are more expensive.
It actually is not necessary for the entire roof to be solar as long as there is "dummy solar" that looks the same as the real solar. The dummy version can be used at the edges (where cutting and screw holes are needed) and on the north facing roof.
PV and Water Piping
Conclusion for my case
Given the negatives of peal and stick PV laminate for metal seam roofing, and given that I have some spare land on my 24 acre property (although all the trees is a problem), I still favor making a separate single story building shelter using low cost solar panels that I import directly from China.
1) Makes a nice covered car port or workshop.
2) As the roof is near the ground it is easy to replace faulty or worn out panels.
3) Can chose whatever panels are least expensive.
4) Appearance does not matter, ie it does not mess up the look of the house.
5) Easier to wash them (dirt hurts efficiency).
6) More panels can be added over time by increasing the length of the building or by building multiple 200sqft buildings.
Use a simple wooden frame and wood planking covered in Ice & Water Shield to make it waterproof. The panels will keep UV off the waterproof membrane.
Facing south west is likely to be best because I need more power in the afternoons and evening than in the mornings.
It would be nice to use the roof of the planned separate garage block except that I want to use the flat roof for growing vegetables. The wooden solar shelter will likely go over the top of the sand filter of the septic system.
On the main house I chose to use regular metal seam roofing with PEX water piping underneath.
Useful links and notes
Monocrystalline solar panels have traditionally had the highest efficiency rates since they are made out of the highest-grade silicon, but Polycrystalline has now caught up. Monocrystalline solar panels have been thought to live the longest but again things are changing. Nowadays it does not really matter which you choose, it is now about price per watt. Micro-inverters will make sure that not the entire solar array is affected by shading issues with only one of the solar panels.
Worlds largest producer of crystalline solar panels, with more than 10 million PV panels sold in over 80 different companies. To learn more about Suntech Power, click here.
Produces the most efficient monocrystalline solar panels available. They also offer all black panels (no visible metal strips), inverters and monitors. For more information click here.
Produces a revolutionary new thin monocrystalline panel that is heat resistant, even produces in conditions of partial shading, and is highly reliable. It also uses just a fraction of the silicon to produce the same high levels of efficiency. For more information click here.
The largest producer of monocrystalline
and polycrystalline solar cells, which it sells to other solar module
manufacturers. It also produces its own PV solar panels that it sells
primarily in China through its own solar development company Yangzhou
This is the oldest and most developed of the three technologies. Monocrystalline panels as the name suggests are created from a single continuous crystal structure. A Monocrystalline panel can be identified from the solar cells which all appear as a single flat color.
They are made through the Czochralski method where a silicon crystal ‘seed’ is placed in a vat of molten silicon. The seed is then slowly drawn up with the molten silicon forming a solid crystal structure around the seed known as an ingot. The ingot of solid crystal silicon that is formed is then finely sliced ingot what is known as a silicon wafer. This is then made into a cell. The Czochralski process results in large cylindrical ingots. Four sides are cut out of the ingots to make silicon wafers. A significant amount of the original silicon ends up as waste. It costs about 20% more to create solar cells with monocrystalline.
Polycrystalline or Multicrystalline are a newer technology and vary in the manufacturing process. Polycrystalline also start as a silicon crystal ‘seed’ placed in a vat of molten silicon. However, rather than draw the silicon crystal seed up as with Monocrystalline the vat of silicon is simply allowed to cool. This is what forms the distinctive edges and grains in the solar cell. Polycrystalline cells were previously thought to be inferior to Monocrystalline because they were slightly less efficient, however, because of the cheaper method by which they can be produced coupled with only slightly lower efficiencies they have become the dominant technology on the residential solar panels market. In November 2015 Trina Solar announced that it had produced a multi-crystalline cell with efficiency of 21.25%. This should allow them to produce polycrystalline modules with efficiencies between 18-20% a concept that was thought impossible as recently as 2013. Underpinning the new record for p-type multicrystalline solar cells has been the continued quality improvements of multicrystalline wafers that have helped pushed standard 60-cell multicrystalline panels from 240W to 260W in recent years. Polycrystalline are now very close to Monocrystalline cells in terms of efficiency.
A common size is 1640*992*40 which is 5' 4-1/2" x 3' 3' x 1-1/2". Add 1/8" around panels.
Siting and Angle
Solar panels should face true south if you are in the northern hemisphere, or true north if you are in the southern hemisphere. As this is true south you are better off figuring this from Google maps rather than using a compass (which only shows magnetic north/south). If you have trees to the east but not the west, it may be better for you to aim your solar panels slightly to the west. Panels produce less power at higher temperatures so this can mean they work better earlier and later in the day.
Ideally you would use a different angle in the winter compared with the summer, but this is a lot of hassle so I prefer to just stick to one fixed angle all year round.
The angle you want depends on the latitude where you live. I am in the Seattle area which has a latitude of about 47.6 degrees. The following calculations assume your latitude is between 25 and 50 degrees.
If you have a fixed angle mount then the calculation is...
Latitude x 0.76 + 3.1 degrees.
For me the calculated fixed angle is 39.3 degrees.
If you are changing the angle between winter and summer then the
Summer: Latitude x 0.93 - 21 degrees.
Winter: Latitude x 0.875 + 19.2 degrees.
For me that makes summer 23.27 degrees and winter 60.85 degrees.
In the "primarily heating required" climate where I live, energy is actually more useful in the winter. I therefore prefer to make the fixed angle a bit closer to the winter angle than the summer angle. My chosen angle is 45 degrees. Using 45 degrees also makes construction of the platform marginally easier.
For my Seattle latitude the optimum degree angles for each month
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
26 34 42 50 58 66 58 50 42 34 26 18