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July 10, 2009 @ 4:18 pm
Solar Did You Knows

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Did you know that virtually any building can be a (albeit small) carbon-free solar power plant using currently available technology? By connecting to the grid, an individual home or commercial/industrial building can distribute excess energy from its solar panels. There is an enormous amount of unused solar energy hitting the Earth – maybe you’ve heard this statistic: each day, enough solar energy reaches Earth to meet U.S. energy needs for one year. The untapped potential of this energy is huge, but solar panels aren’t very efficient and were always very expensive to install until recently…
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Have you heard of SunEdison? They have built a revolutionary business model that enables them to install commercial/institutional solar systems for no upfront cost to the customer. Using a Power Purchase Agreement (PPA), the customer receives predictable electricity pricing whether drawing all its needs from the panels or the traditional grid. If expanding the clean energy infrastructure wasn’t enough, these installations also take advantage of tax credits and other incentives to minimize energy prices. Lastly, they will pay you (in the form of rebates) for excess electricity – i.e. distributed generation – that is sold back to the grid. For individual homeowners, a company like Akeena Solar and Solar City can provide similar benefits (although installation costs can only be deferred, not $0)

How does the sun create energy anyway?
The sun is largely made of hydrogen and helium gas and its massive gravity creates intense pressure inside its core that fuses hydrogen atoms into helium. This nuclear fusion produces massive amounts of energy through a chain reaction of immense heat that discharges photons that are then absorbed into gas molecules which heat neighboring atoms to the point of re-emitting photons and continuing the cycle. Finally, the energy is radiated from the sun’s surface in the form of light and heat. Most of the heat dissipates in space but we receive a continuous stream of light that takes about 8 minutes to arrive on Earth.

How do we convert this energy to something we can use?
There are four primary ways to take advantage of solar energy: 1) photovoltaic (PV) cells and 2) solar thermal systems produce electricity while 3) active solar collectors and 4) passive solar design produce heat.

  1. PV Cells: These power the traditional arrays or rooftop panels most people are familiar with. Two layers of a semiconductor material such as silicon or cadmium telluride absorb energy from the sunlight and excite electrons to generate an electric voltage and current that is carried by tiny wires to an electrical circuit. The solar module or panel is designed with enough cells wired in series to produce the voltage and current. Alone or as part of an array, the modules are ultimately connected to an inverter that converts their Direct Current to Alternating Current we can use in our homes, offices, schools, etc.
  2. Solar Thermal Systems: This method is a simpler and more efficient way to make solar power, especially on a larger scale. Essentially, an array of mirrored solar collectors is designed to mechanically follow the path of the sun and focus sunlight on a receiving tower to heat a liquid. The super-heated liquid then generates steam to turn a turbine that produces power, much like traditional power plants minus the burning of fossil fuels and ensuing pollution.
  3. Active Solar Collectors: Usually mounted on rooftops, these are essentially glass boxes with dark metal plates inside that absorb and heat up air or water that is flowed through the collector. The warm air or water is then distributed throughout the building just like it would be by a traditional furnace but without the electricity or fuel needs.
  4. Passive Solar Design: Indoor spaces can be heated simply by letting in as much sunlight as possible through windows. The building becomes a giant solar collector that allows the sun to heat the walls and floors inside the building to radiate and retain heat within it.

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