Solar PV and cool roofing

Reducing Energy consumption to Maximize Solar PV system efficiency

Part II of solar PV design Guide:

As a rule  of thumb, an average house in the US will need about 5 kW solar system to become self-sufficient and  independent of grid electricity. As another rule of thumb, an average Solar PV system installed in the US is about 2.5 – 3 kW, and you still have to buy about half of your electricity from a local utility company.

Before you start shopping for a Solar PV system, you will need to do some homework, and it is also in your best interest to do the preparations, which will reduce your energy use. As a result, you will need a smaller Photovoltaic System.

On average, every dollar you spend on reducing resources consumption will provide 2 dollars in savings. Things you can and should do to reduce your energy consumption (even if you do not plan to have a solar system installed):



  1. Get small florescent light bulbs – you should have done it a long time ago, as these have been available for years. Benefits include reduction in electricity use by 3 times. Service life of SFB is… well, I have a bunch of them that are 3 years old, and I have not had to replace a single one of them yet. I bought mine for $0.50 each, 4 years ago, from Ann & Hope in Cumberland, RI, and some from Building #19. You should have some similar discount retailers near you.
  2. Replace your inefficient appliances with new Energy Star certified ones. Do your research on energy savings. I calculated that if I replace my old fridge with a $200 new Energy Star fridge, I will recoup its cost in 1 year, as it contributes probably half of my $40 monthly electric bill. You can go to a Sears Appliances Outlet and buy brand new stuff for almost 50%  off in store prices.
  3. Insulate your home! Over 80 percent of homes built before 1960’s do not have any insulation. If you increase your insulation from a 3-r for a standard stick-construction walls with no insulation, to lets say 13-r by having a blown-in insulation installed, you will reduce your heating and cooling bill by 25 to 30 percent. Do the same to your windows. If you still have old, drafty single-pane windows, replace them with at least an Energy Star certified double-pane with Low-E film. the best option is to have a Triple Glazed, 2x Low-E, 2x Argon or Krypton gas premium window, that can go to almost 10-r value. Insulate your doors with weather-stripping. A lot of cold air enters the house through the doors, especially, if there is no second door. If you make your home super-insulated, your heating/cooling bill can be reduced to almost 10% of its original amount. That is a 10 times reduction, for which you pay only once, and it will save you money for years to come!
  4. Install Low-Flow shower heads and 1 gallon per flush toilet. Whether you are a landlord or a homeowner, your water bill has probably skyrocketed in the last couple of years. Mine definitely has gone up 30% in last 3 years.

Have a Cool Roof installed

While most heat loss in the winter occurs through the windows, in the summer, most of the heat gain occurs through your roof. Most homes in the US have an asphalt shingles roof, which is not only bad for the environment, but also contributes 90% of the solar heat gain. Even light-colored asphalt shingles attract solar radiation, transfer it into the attic and also act as thermal mass, by storing most of the heat gained during the day, and keeping your attic steaming hot at night, making the AC work around the clock.



Whether you do or do not plan to have a Solar PV system installed (be it on the roof of your house or a ground-mounted array), your first concern must be to reduce your energy use. This is especially true if you actually plan to have a solar electric system installed. A cool roof can reduce your Cooling cost by 25% or more and can help you trim your solar PV system requirements by as much as 1 kW. At $10 to 12 per watt of solar PV system, you are looking to save $10,000 to 12,000 before any incentives or tax credits.

Choices of Cool Roofing for Residential and Commercial use

A good example of a cool roof would be a Metal Roof coated with Kynar 500 Cool-Roof certified reflective coating. You have a variety of architectural styles and choices of metal available to you. From Standing Seam to Aluminum shingles, to Steel Slate or Tile impression to Heavy Cedar shake, Spanish Tile, etc. As for material, your two basic choices are Steel and Aluminum, with Zinc and Copper being the more exotic, as well as the more expensive options. If you are looking to integrate Uni-Solar Thin Film laminates to Standing Seam metal roofing, you want to go with a steel panel, as aluminum’s expansion/contraction ratio is more than that of Uni-Solar’s PV modules.

If you own a home or building with a low pitch or a flat roof, the most economical and greenest choice for you is to use a IB CPA/PVC single-ply membrane, which has a Cool roof acrylic coating, featuring over 90% solar reflectance. IB roof is also a long lasting membrane that features hot-air welded seams. The welded seams create a permanent bond between two sheets of membrane, effectively eliminating the possibility of a leak.

Planning a Solar PV system

Solar electricity is probably the most expensive form of electricity, yet it is very popular due to some constraints associated with other forms of renewable energy. Wind power for example requires an adequate amount of land and the turbine must be located above the trees and surrounding structures. This limits the use of wind turbines mostly to rural areas. Small hydro-electric systems require a water stream or a river near your house or building, which also limits its use to certain locations. Solar on the other hand can be installed almost everywhere, as long as there is unshaded southern exposure and an adequate installation area. Solar PV can be installed on the ground, on the roof of a house, barn/garage, skyscraper or a warehouse. It can be installed in an urban environment – grid-tied, as well as on a remote unpopulated island – off-grid.





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