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Solar Water Beds for Heating (and Cooling) Living Spaces

written by: •edited by: Lamar Stonecypher•updated: 1/1/2011

Solar water beds for heating and cooling living spaces have been around for some time They consist of large rubber bladders with an absorbent surface that uses the sun to heat the water contained inside. The heat is then transferred into the living quarters of the house.

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    Introduction to Solar Water Beds for Heating and Cooling Living Spaces

    Solar water beds, which are sometimes called solar water bags or solar water bladders, are used to heat water using renewable energy from the sun, releasing it during the night to the living quarters of the house. They can also be used to cool the house on hot days.

    This is an article on renewable energy and in particular the use of solar water beds to heat and cool the living spaces.

    We begin the article with the layout and description of a typical roof-mounted solar water bed.

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    Roof Solar Water Heating System – Overview and Components

    The system consists of three major components;

    • Water Bags/Bladders – the bladders that contain the water are manufactured from pliable materials such as rubber, PVC or a waterproof fabric. They can be completely opaque or opaque with a transparent window to let the suns radiance through to the water. They absorb the heat during the day and release it during the colder nights. They can also be used to convert the system to a room cooler.
    • Insulator – insulation sheets are used to cover over the bags at night to stop any heat loss to the atmosphere. The sheets are also used when the system is in the cooling mode and are normally bi-fold, roll or slide design being manually or electrically operated.
    • Corrugated Roof – being the thermal conductor between the water bags and the inside of the house, this is a load-bearing structure. The corrugations assist in the transfer of heat from or to the bladders. The steel roof should be galvanized or painted with another anti-corrosive coating, and must be in direct contact with the underside of the bladders and the inside of the living quarters.

    A typical roof-mounted system is shown below. (Please click on the diagram to enlarge the image.)

    Typical Roofmounted Water Bag Solar Heating System 

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    Solar Water Bed Heating System – Operating Principles

    The solar water bed works on the principle of using the renewable energy from the sun to heat water contained in a water bag or bladder.

    In a roof mounted system, the sequence of operation is as follows:

    1. Heating Mode

    During the day the bladders are exposed to the sun, absorbing the energy and heating to the water inside. At night the insulation sheets are drawn across the water bags, preventing heat loss to the atmosphere. The heat from the bags is transferred through the steel roof into the living quarters of the house.

    2. Cooling Mode

    In the cooling mode the insulation sheets are drawn across the bladders preventing the sunshine from penetrating bladders, and keeping the water relatively cool.

    The heat is prevented from entering the house by the insulation sheets, with some heat being extracted from the interior of the house, through the steel roof, and absorbed by the water, cooling the living quarters.

    Reference Webs:

    1. Skytherm Solar: Rooftop water bag solar heating and cooling.
    2. Solar Mirror: working principles of water bag heating and cooling.
    3. Blacksun Journal: Solar House