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    Solar power

    Floyd
    Floyd

    Posts : 4104
    Join date : 2010-04-16

    Solar power Empty Solar power

    Post  Floyd on Sun Jul 25, 2010 3:47 am

    Solar Power
    http://www.lowimpactliving.com/pages...ts/solar-power

    What's
    not to love about solar power? It's free, clean, and available every
    day. And you don't have to live in California or the Australian outback
    to harness the power of the sun. The costs of solar systems have come
    down 80%+ over the past two decades, and as more consumers take to solar
    the costs are falling still. There are a variety of solar power options
    available, and it's important to understand the benefits and costs of
    each option.

    how solar power works
    Solar power is produced by
    using photovoltaic (PV) cells to capture the energy of the sun and
    convert it into electricity. The basic unit of the system is the solar
    cell, which are connected together into modules. PV cells are comprised
    of semi-conductors, most often made of silicon (like the chips used in
    computers). The semiconductors absorb power when they are struck by
    light. These modules or panels of PV cells are what you see installed
    typically on the roofs of homes and businesses. The electricity created
    by the solar system is DC or direct current, and the electricity we use
    in our homes is AC or alternating currents. Thus solar systems include
    an inverter which changes the DC current into useable AC current.
    Installing solar systems is a complicated technical process and most
    people will benefit by using contractors skilled in solar technology and
    electrical installation.
    Find a solar installer in your area.

    home solar power systems
    There
    are two main forms of solar systems for residential use: the “grid-tie”
    system and the “off-grid” or stand-alone system. In a grid-tie system, a
    home has solar cells but is still connected to the local power grid.
    The home solar system includes solar cells installed on or near a home
    that collect the sun's energy and convert it into DC electricity. Then
    the inverter converts the DC power into AC power, which can then be used
    directly in your home.

    Electricity produced by the solar cells
    that is not used immediately in the home is returned to the power grid.
    When this happens your electricity meter literally spins backwards as
    you are passing energy to the grid. You are also building a credit on
    your power bill. This is called “net-metering”. The benefit of the
    grid-tied system is that it does not include expensive batteries to be
    installed in your home for the storage of power; the grid acts as the
    storage system and your home and the grid exchange power as you need and
    produce it.

    Off-grid or stand-alone systems are typically used
    in remote locations where standard grid-based power is not available.
    These systems are more expensive, but do allow for complete electrical
    independence. These systems require deep-cycle batteries for storing the
    electricity as well as a charge controller to assure the flow of
    electricity from the cells does not over-charge the batteries.

    For
    a solar system to work well it needs an unobstructed view of the sun.
    In the United States, typically the best orientation for solar panels is
    to the south as the sun is in the southern half of the sky (lower in
    the winter and higher in the summer).

    Solar panels can either be
    attached directly to a slanting roof, or bolted onto frames on flat
    roofs. If your roof is not a good option, then panels can also be
    mounted on the ground. They can either be placed on a fixed mount frame
    or on a “tracking mount” that follows the sun across the sky.

    For an excellent consumer guide to selecting and purchasing the right solar system, please visit http://www.nrel.gov/docs/fy04osti/35297.pdf

    For more detail on how solar power works, please visit: http://www.solarelectricpower.org/in...&display=facts

    solar water heaters
    A
    solar water heating system is fairly simple. You install solar panels,
    typically on your roof, and the sun heats the panels. Then these solar
    collectors heat a fluid in pipes held in the interior of the panel
    boxes, and that fluid is transported into the house where it heats water
    in a storage tank. The system can include a pump which circulates the
    transmission fluid from the roof to the water tank and back again, but
    pumpless systems are also available. In areas where freezing isn't an
    issue, systems can heat your water directly. In most places a type of
    antifreeze is used and the fluid and water do not mix.

    One
    convenient and less expensive option if you live in a warm climate is a
    solar batch collector. Water is simply pumped up to a solar storage tank
    on the roof and heated by the sun. Then you just use the hot water as
    needed. (But you need to make sure you have a roof that is strong enough
    to support the weight of the stored water and the tank.) These units
    cost less than $1000. Another great way to save energy and money if you
    are a pool-owner is to use solar power to heat your pool. Find a solar
    installer in your area.

    solar power costs and pay-back periods
    The
    cost of a solar system depends on the size of your home, the
    orientation of your property, and your electricity needs. But for a
    standard medium-size house it can run from $20,000-$40,000 before
    rebates.

    However, many state and local governments offer
    incentives for solar installation that can significantly reduce the
    costs. Rebates coupled with federal tax credits can knock thousands off
    of your initial investment, sometimes cutting it in half! Be sure to
    check with your local government for these offers. To see a list of
    state and local incentives please visit: http://www.dsireusa.org/

    One
    way to cut the cost of a solar electric system is to reduce your
    electricity use before installing the system. Such measures as replacing
    light bulbs with compact fluorescents and upgrading old appliances can
    cut your electricity use (and also your solar investment) in half.
    You'll spend a bit of the savings on the new items, but you'll have that
    brand new stainless refrigerator you've been craving too. Low Impact
    Living's In-Home Environmental Assessment program will help you
    understand what cuts can be made before you go solar and therefore save
    you thousands of dollars - click here and sign up to receive more
    information.

    You can also finance solar installation using home
    equity. This approach offers the possibility of making you “cash flow
    positive” from day one, especially if you live in an area that has high
    power prices, good exposure to the sun, and solid local rebates.

    If
    the cost of a full house solar system is daunting, a very attractive
    option can be heating your water with the power of the sun. A solar
    water heating system will save a typical California family $1000 in
    power costs. The payback period on these units is typically under five
    years.

    Other great lower-cost solar options are distributed solar
    applications. You can get attractive solar lights to illuminate your
    yard or garden. You can also power a nice fountain or heat your pool
    using solar energy. See great low-cost solar options.
    __________________
    Floyd
    Floyd

    Posts : 4104
    Join date : 2010-04-16

    Solar power Empty Re: Solar power

    Post  Floyd on Sun Jul 25, 2010 3:47 am

    From recycled TV Lens!

    6-8 thousand projected for a production system

    http://peswiki.com/index.php/Directo...l_Solar_Design

    but

    This is something people with basic skills can build themselves with a little determination and research!

    Charles Shults' Fresnel Solar Design

    A 60"x40" lens has an area of (60*0.0254)*(40*0.0254) = 1.55 m^2

    Solar constant is 1340 W/m^2, but at the surface, due to scattering it's more like 800 W/m^2 on a sunny day.

    Incoming power = (1.55 m^2) * (800 W/m^2) = 1240W, which is what he says (1.2 kW).

    But
    absorption of this energy isn't perfectly efficient; the target has
    some reflectivity and also emits heat via thermal radiation.

    So, actual available heat energy will be smaller than 1.2 kW, but I'll ignore that in case the lens is bigger than 40" tall.

    I'll go with 1.2 kW of available heat energy.

    Water from the thermal panels is at most at 180 F = 82C

    Energy required to bring that water to 100C = (100C - 82C) * (4.186 kJ/kgC) = 75 kJ/kg

    Latent heat of vaporization of water = 2260 kJ/kg

    So, it takes (2260 + 75) = 2335 kJ per kg of water boiled.

    Density of water is about 1 kg/liter

    This means that the most water this system can boil is

    Volume per unit time = power / energy per unit volume

    = (1.2 kJ/s) / (2335 kJ per liter) = 0.514 ml/s (0.017 ounces per second, for the Americans)

    That's
    a very small amount of water. Even if there were no thermal losses
    after the steam generator, there's not much steam power available.

    Sorry.

    It would be better to consider a Sterling engine, or maybe thermocouples, with that sort of power output.

    A
    relevant example: boil a pot of water on a small stove burner. If you
    push down on the lid, the steam hisses out. Is it enough to run a useful
    turbine? No; but the power is about the same as the Fresnel system
    (bigger, actually).
    __________________

    This is the energy of the moment FREE energy :

    http://www.ethosfreeenergy.com/disco...rnative-answer

    Hydrogen
    makes an excellent fuel because it works well as an energy carrier. in
    fact, hygrogen is so effective at carrying energy that it has been used
    to power the rockets that are sent to space by NASA since the 1940.

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