Solar Energy Panels
Solar Energy Panels are panels that collect solar energy by having a large surface area and sometimes having mirrors or having photoelectric cells within to convert light energy into electric energy. However most solar panels you see on houses are in fact the kind that convert light and heat energy into stored energy by heating water, which can then reduce the cost of heating hot water and using less gas fed resources, giving an overall lower price. These systems are expensive, and the panels can weigh more than 100 lbs each, but the price is declining now that they're widespread in use. The basics are that light energy in the form of heat is collected and concentrated into water that is piped and fed through the panels, and is this stored. This storage can either be separate or a part of the main hot water storage tank system. Some of these systems actually don't use water directly being heated but rather use heat transfer fluid to increase the longevity of the panel.
The usual setup involves the panels that go on the roof (and can heat an amazing amount of water if given the time) in which water is pumped up to from the main water line, it will pass through either two or three panels and is piped into a Solar Storage Tank. This tank will pass water through to the gas or electric water heater as a backup, and there are many shutoff valves in case of maintenance or problems - in addition there are usually two or three emergency steam valves, a water temperature readout and setting, along with other relief valves and systems in place to ensure safe operation, even under freezing conditions so that panels stay working. Furthermore the water that is in the solar tank is recycled through to pump so that it is constantly heated to higher temperatures by passing through the solar panels - an ensuring system that will keep the water hot at all times.