Solar Water Heating PanelsLike I said in class, there is a law in Israel, forcing most buildings to have solar water heating panels installed on the rooftops. The structure is made out of two main parts - the water container and the sun panels. This panel is mostly made out of metal, except one side, which is either glass or see-through plastic. A winding water pipe runs through the inside of the panel, on top of a black background. In israel, the panels are set on rooftops, facing south, where they catch the maximum amount of sunshine. How Does it work? Water from the home is connected to the pipe inside the panel, the other side of the panel is connected to the cylindrical water container. Because of the dark color, as the sun hits the panel, the pipe heats up, as well as the water inside of it. The container is placed in a higher position compared to the panels, so that when the water heated up in the panels become hotter than the water in the container, there is an exchange, so that the hotter water goes up to the container. If the container is located in a lower position compared to the solar panels (such as in highrise apartment buildings), a special circulation force is activated. The water container has another opening, from which hot water flows into the home. image Why? As a result of the Energy Crisis in the 1970's, this law was enacted. The world energy crisis broke out after the Yom Kippur War (1973) in the Middle East, when the arab countries all decided to substantially lower their oil exports to the western countries, raising the oil prices significantly. The arab counties drew an ultimatum for the western world to put pressure on Israel to go back to the 1967 borders (pre-Yom Kippur war). The price of oil quadrupled by 1974 to nearly US$12 per US gallon. Very informative article here. Solar water heating panels account for 4% of the total energy consumption of Israel. HowStuffWorks - thorough explanation about how solar cells work. The short explanation: solar panels use photovoltaic cells which convert light into electricity. Photovoltaic (PV) cells are made of semiconductors (such as silicon). When light strikes the cell, a certain portion of it is absorbed within the semiconductor material. The energy of the absorbed light is transferred to the semiconductor, which knocks electrons loose, allowing them to flow freely. PV cells also have one or more electric fields that make sure the electrons freed by light flow in a certain direction. This current can be used as a source of power in electric circuits. Ordering Parts Item Voc Isc (mA) Watts Dimensions Price 04-1193 .55 450 .24 1" x 2.5" $1.60 04-1189 .55 600 .33 1.6" x 2.5 $2.00 04-1194 .55 1200 .66 2.5" x 2.5" $2.90 04-1195 .55 2200 1.2 2.5" x 5" $3.45 04-1196 .55 4100-4500 2.3 5" x 5" $8.50 LINKS: Biodesign - from Tom's links. DIY PV project descriptions. |
