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Building-integrated Photovoltaic




Building-integrated photovoltaics (BIPV) are increasingly incorporated into new domestic and industrial buildings as a principal or ancillary source of electrical power, buildingsolar.com: Building-Integrated Photovoltaics , Wisconsin Public Service Corporation, accessed: 2007-03-23. and are one of the fastest growing segments of the photovoltaic industry. Terrasolar , accessed: 2007-03-23.

The idea behind BIPV is to reduce the installed cost of a PV system by making a Photovoltaic Module in the form of a building element such as a roof tile, roof membrane or facade panel. In general BIPV modules are designed to look nicer.

These special BIPV modules are incorporated into the roof or walls of a building by standard construction methods (with additional electrical connections required). Roof tiles and roof membranes with integrated PV cells can now be purchased. With the exception of Japan, where a combination of government incentives for PV and a high proportion of new houses being prefabricated allowed BIPV to be a part of a substantial number of new homes, substantial progress of BIPV has been restricted by the relatively high cost or limited availability of BIPV modules. The French government put in place a large subsidy for BIPV modules v standard modules in 2006. This is expected to stimulate BIPV installations in preference to standard modules.

BIPV Arrays can also be retrofitted into existing buildings.


COSTS AND INCENTIVES

See Also: PV financial incentives


In some countries, additional incentives are offered compared to stand alone PV. Only in France is the premium enough to make a substantial difference.
  • France + EUR 0.25/kWh

  • Italy + EUR 0.04-0.09 kWh

  • Germany + EUR 0.05/kWh (facades only)



ROOFS, FACADES AND WINDOWS


BIPV modules come in several forms.

  • Flat roofs

  • ---The most widely installed to date is a thin film cell integrated to a flexible polymer roofing membrane (Sika, Alwitra).


  • Pitched roofs

  • ---Modules shaped like a multiple of roof tiles, including Solar Century (.uk) Marley, Imerys, BP Solar, Powerlight (CA)

  • --- Solar Shingles are modules shaped like shingles, incorporating a flexible thin film cell


  • Facades

  • --- Special building elements designed to receive modules are also available e.g. a sandwich element composed of two metallic corrugated and ribbing sheets and, inside, of high-density Polyurethane foam. The panel has a profile specifically designed to insert a custom-made photovoltaic module, considering the indispensable ventilation requirement on the rear surface of the module. Through the interstice an optimal level of working temperature is ensured for the system and the different thermal expansions are respected.


  • Glazing -transparent modules based on architectural glass elements

  • --- with crystalline silicon cells (in the UK from Romag)

  • --- with very thin amorphous silicon (Schott Solar 'Asithru', XsunX)



BIPV ON HOUSES


Solar Shingles are solar cells shaped like shingles, and can be installed on any normal roof. Solar panels are collections of solar cells to form rectangular sections, but usually require a frame or structure to be mounted on top of an existing roof.

When a roof is covered with these Photovoltaic (PV) solar cells, it can generate electricity from sunlight. Some people use this to generate their home’s electricity, or at least a portion of it. In addition to being in a sunny location, a solar roof is ideal in the following situations:

  • When the house in need of electricity is in a remote location, and is not connected to the power grid.

  • When electricity prices are high, and the owner wishes to offset a portion of the cost of the electricity bill.


A house that is not connected to the power grid is called “off-grid”, and therefore uses an off-grid configuration for their solar roof. Inverters change the electricity produced by the roof to the voltage and frequency needed. These are machines that are placed inside the house. The house uses only the electricity produced by the roof.

A house that is connected to the power grid is called “on-grid”, (grid-tied, grid connected) and therefore uses an on-grid configuration for their solar roof. When the sun is shining brightly during the day, the solar roof provides most of the power for the house, and the extra power is drawn from the grid, lowering the amount of electricity bought from the grid. If the roof is fairly large, or the house uses little electricity, and the roof produces more electricity than is used by the house, extra electricity can be sold back to the grid, with certain utilities. The connection to the grid requires a special meter which can run forwards and backwards (net metering) and if a feed in tariff is paid an additional meter to measure PV production is needed.

The cost of covering a typical American house's roof with solar panels is $15,000 to $84,000 USD. A portion of this price may be reimbursed by the federal and state governments to provide incentives to use "green energy". Technologically and financially speaking, it would probably be best to initially install enough panels to reduce purchased electricity so that the net monthly usage is close to the lifeline. Lifeline is generally around 300 kWh. So, this means if a household used around 600 kWh a month, it would be wise to buy enough panels to generate around 300 kWh a month. This gives the fastest return on investment and also gives a chance to upgrade later with better technology (eg. 40 % efficient panels compared to the existing 10-20 % efficient panels).

Use California as an example...the marginal rate goes from $0.11 - $0.13 - $0.23 - $0.32 - $0.37 per kWh. Most households would hover around the $0.13 and $0.23 per kWh. This makes it fast for you to recoup your investments - especially during hot summers when the household electric powered A/C is on.

There are also many solar housing projects that go hand in hand with charity organizations, allowing these homes to supply their own electricity to further reduce monthly payments for families in need. US companies such as Pacific Gas and Electric (PG&E) have partnered with Habitat for Humanity to provide complete solar grids for a such housing projects. PG&E Solar Project . There are also other solar projects,like this one in San Francisco San Francisco Solar , as well as independant efforts that are trying to make a difference by raising funds to get more of these solar homes built Solar Fund Raising Effort . With no moving parts, and long life spans, a donated PV array on a home has the potential to reduce monthly bills and sell electricty back into the grid to fund future projects. More often builders are including rooftop solar panels/shingles. Lennar plans 1,254 more solar homes In the United States a survey showed that a majority thought it should be an option for all new construction. Survey: Solar wanted on new U.S. homes From an energy standpoint, rooftops are underutilized real estate. Solar breakthrough


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