Editing Solar thermal collector (section)

=== Applications ===
The main use of this technology is in residential buildings where the demand for hot water has a large impact on energy bills. This generally means a situation with a large family or a situation in which the hot water demand is excessive due to frequent laundry washing. Commercial applications include laundromats, car washes, military laundry facilities and eating establishments. The technology can also be used for space heating if the building is located off-grid or if utility power is subject to frequent outages. [[Solar water heating]] systems are most likely to be cost effective for facilities with water heating systems that are expensive to operate, or with operations such as laundries or kitchens that require large quantities of hot water. Unglazed liquid collectors are commonly used to heat water for swimming pools but can also be applied to large-scale water pre-heating. When loads are large relative to the available collector area, the bulk of the water heating can be done at low temperature, lower than swimming pool temperatures where unglazed collectors are well established in the marketplace as the right choice. Because these collectors need not withstand high temperatures, they can use less expensive materials such as plastic or rubber. Many unglazed collectors are made of polypropylene and must be drained fully to avoid freeze damage when air temperatures drop below {{convert|44|F}} on clear nights.<ref>Tom Lane, Solar Hot Water Systems, Lessons Learned 1977 to Today p7</ref> A smaller but growing percentage of unglazed collectors are flexible meaning they can withstand water freezing solid inside their absorber. The freeze concern only needs to be the water-filled piping and collector manifolds in a hard freeze condition. Unglazed solar hot water systems should be installed to "drainback" to a storage tank whenever solar radiation is insufficient. There are no thermal shock concerns with unglazed systems. Commonly used in swimming pool heating since solar energy's early beginnings, unglazed solar collectors heat swimming pool water directly without the need for antifreeze or heat exchangers. Hot water solar systems require heat exchangers due to contamination possibilities and in the case of unglazed collectors, the pressure difference between the solar working fluid (water) and the load (pressurized cold city water). Large-scale unglazed solar hot water heaters, like the one at the Minoru Aquatic Center in Richmond, BC operate at lower temperatures than evacuated tube or boxed and glazed collector systems. Although they require larger, more expensive heat exchangers, all other components including vented storage tanks and uninsulated plastic PVC piping reduce the costs of this alternative dramatically compared to the higher temperature collector types. When heating hot water, we are actually heating cold to warm and warm to hot. We can heat cold to warm as efficiently with unglazed collectors, just as we can heat warm to hot with high-temperature collectors.{{citation needed|date=January 2021}}