25-09-2013, 04:01 PM
Hot Water and Solar Hot Water
Water and Solar Hot.ppt (Size: 2.28 MB / Downloads: 23)
Household Hot Water
Hot Water consumption – 20 gal per person per day
Daily basis for showers and baths, for washing dishes and clothes, as well as other purposes.
For a family of 4, it will consume around 200 gallons of oil a year (assuming a 70% efficiency).
About 25% of home energy consumption
Water is typically heated by a variety of fuels (oil, natural gas, propane) and also by electricity. All these methods use up valuable natural resources and create significant pollution.
Solar hot water is a viable option..
Solar Hot Water
Will supply about 75% of your hot water needs over the year if sized properly.
Almost all solar hot water heaters use an auxiliary backup system when the sun is insufficient.
Other Applications of Similar Technology
Pool heating
Space heating of buildings
Absorption air conditioning
Concentrating collectors for high temperature water for industry uses and for power production
Thermosyphoning Systems
The main advantages are the lack of a pump and electrical energy savings. In warm climates, the tanks can be outside on the roof above the collectors. On slanted roofs, the tanks can lie horizontally on the roof itself.
Active Solar Hot Water Systems
Collectors
Solar water storage system
Pump(s)
Heat exchangers
Controls
DIRECT where water is pumped directly through the collector and back into the storage tank,
INDIRECT where an anti-freeze fluid is pumped through the collector, and heats water in storage by means of a heat exchange coil
Types of Active Systems
Direct systems use only water in the collector. These are typically the draindown and the drainback systems.
Indirect systems use anti-freeze circulated in the collectors. Some of these systems use standard pumps, and others use PV or solar-powered DC pumps to circulate the anti-freeze. These are typically called closed loop systems.
But Non-Optimal Siting OK
Not highly sensitive to the exact orientation and tilt of the collector.
The collector could tilt between 30 and 50 degrees, or the orientation could be off from south by + or – 30 degrees with little loss (< 10%) over the year.
Collectors may also be mounted at an angle to the roof, although this is less aesthetically pleasing. Ground mounting is ok, too.
Solar Concentrating Collectors
Concentrating solar collectors focus the sun’s rays on a line (in a parabolic collector) or to a point (in a spherical collector). In both cases, the temperature of the receiver (the metal component enclosing a fluid) gets very hot. This is not needed for household use, but is desirable for certain industry needs and for producing electricity by running steam turbines.