Green Solar Cafe – renewable energy and green construction

Reducing Energy consumption to Maximize Solar PV system efficiency

Part II of solar PV design Guide:

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

Before you start shopping for 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, and as a result you will need a smaller Photovoltaic System.

On average, every dollar you spend on reducing resources consumption, will provide 2 dollar 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 long time ago as these have been available for years. Benefits include reduction in electricity use by 3 time. Service life of SFB is… well, i have a bunch of them that are 3 years old, and I have not had to replaced 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 retailer 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 it’s 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. 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 sky-rocketed in the last couple of years. Mine definitely have 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 solar heat gain. Even light-colored asphalt shingle 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 you 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 ground-mounted array), your firs 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 you 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 metal roofing 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 on the exotic side, as well as the more expensive options. If you look 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 ration is more than that of Uni-Solar’s PV modules.

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

Planning a Solar PV system

Solar electricity is probably the most expensive form of electricity, yet it is very popular due to some constrains associated with other forms of renewable energy. Wind power for example requires 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 requires as water stream or a river nearby your house or building, which also limits it’s use to certain situation. Solar on the other hand can be installed almost everywhere, as long as there is unshaded southern exposure and adequate installation area. Solar PV can be installed on the ground, on the roof of a house, barn/garage, sky-scraper or a warehouse. It can be installed in urban environment – grid-tied, as well as on a remote unpopulated island – off-grid.

With Solar you also have a variety of architectural styles, panel types and mounting methods available. Most popular (yet, least efficient) is to mount mono or poly-silicon solar panels right to the asphalt shingles roof, using mounting rails and brackets.