Solar hot water refers to water heated by solar energy. Solar water heating systems are generally composed of solar thermal collectors, a transfer fluid system to move the heat from the collector to its point of usage, and a reservoir or tank for heat storage and subsequent use.
Technology definitions
(As per Eskom Terms of Reference)
Absorber: The part of a Collector that absorbs solar heat energy and transfers it to the water either in the Collector or in the storage tank.
Close coupled system: A SWH system where the tank and the heat collectors are located directly next to each other, with the tank being on top of the collector/s.
Collector: This part of the system absorbs the solar radiation from the sun, converts it into heat, and then transfers the heat either through a Themosiphon process (High pressure or Low pressure systems), or via a solar pump system to the storage tank / geyser where cold water is heated (High pressure systems). (Tasol prefers Evacuated Tube collectors, see 1.7 )
Direct system:The water in the SWH collector is heated and this hot water (also referred to as “potable water”) is transferred directly into the tank.
Electric geyser: This is a conventional water storage heater (geyser) that is not specifically designed for Solar Water heating purposes.
Evacuated tube collector: These collectors have multiple evacuated glass tubes which heat up solar absorbers and, ultimately, solar working fluid (water or an antifreeze mix -- typically propylene glycol), in order to heat domestic hot water. (Wikipedia)
Expansion tank: Takes up the overflow created when the heat transfer fluid (glycol) expands.
Freeze resistant: A system that has passed the SABS freeze test and can be used in areas known to have frost.
Heat exchanger: A device that transfers the acquired heat from itself to the water through a separating wall.
High pressure: Any SABS certified/approved system that operates above 100kPa and works in conjunction with a pressure valve.
Indirect system: SWH system where a heat exchanger is heated by the sun and then this heat is transferred to the water heating it indirectly.
Low pressure: Any SABS certified system that operates below 100kPa.
Pumped: A SWH requiring a pump to circulate the water.
Split system:The tank and the collector are separate.
SWH Tank: A water storage unit, SABS approved and have been tested with the rest of the system, being sold to the customer as a unit.
Thermosiphon: This system includes a tank, collector and Geyser Wise Controller. The tank is mounted above the collector, outside on the roof. As the water in the manifold section of the collector gets warmer, the water rises and mixes with the colder water from the tank, eventually heating all the water to a higher temperature. This natural phenomenon is called the thermosiphon effect. These systems operate on the difference in densities of hot and cold water. The hot, less dense water rises to the tank and is replaced by colder more dense water from the bottom of the tank. No external pump system is required.
Timer / Controller: A device fitted to the Distribution Board to control when a heating element may or may not be switched on and for the purpose of the Demand Side Management programs, implemented by ESKOM to save electricity demand during peak times. There are minimum specifications stipulated for these units(refer Appendix E).
Collector panel: The component of SWH system that absorbs the incoming solar radiation in order for the thermal energy to be transferred to the water. There are two types, the flat plate and the evacuated tube. The flat plate has copper tubes that is encased in a frame and covered with glass. The evacuated tubes has a vacuum in between the two glass tubes that prevents heat from leaving the collector via the glass. The anti-reflecting coating prevents electromagnetic radiation from being reflected out of the collector. This technology is discussed in the next section.
PV Panel:Photovoltaics or PV for short, is a technology that converts light directly into DC electricity.
