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Solar Water Heaters

physics project on the difference between solar water heaters and gas water heaters

dexter calhoun

on 17 February 2010

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Transcript of Solar Water Heaters

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Solar Water Heaters
What is it you may ask?
Advantages & Disadvantages
Prices & Operating Expenses
Different Types of Heaters
Solar water heaters, also called solar domestic hot water systems, can be a cost-effective way to generate hot water for your home. They can be used in any climate, and they receive their power from the sun, so the fuel to use this kind of system, is free.
Solar water heaters
include storage tanks, solar collectors,
and a back up storage tank; just in case of
cloudy days and for increased demand.
Two types of systems: active and passive
Active: have circulating pumps and controls on the system
Passive: they do not have circulating pumps and controls
Some solar water heaters are either two-tanked or one tanked.
Two tanked: one tank preheat heats the water in the tank, then after its heated, it enters the conventional water heater, and thus hot water is made.
One tanked: the back-up heater is combined with the solar storage in one tank.
Three types of solar collectors are used for residential applications:
Flat-plate collector: Glazed flat-plate collectors are insulated, weatherproofed boxes that have a dark absorber plate under glass or polymer covers. Unglazed collectors, used for solar pool heating, have a dark absorber plate, made of metal or polymer, without a cover or enclosure
There are two types of active solar water heating systems:
Direct circulation systems
Pumps circulate household water through the collectors and into the home. They work well in climates where it rarely freezes.
Indirect circulation systems
Pumps circulate a non-freezing, heat-transfer fluid through the collectors and a heat exchanger. Examples of heat-transfer fluids are: air, water, Glycol/water mixtures, Hydrocarbon oils, Refrigerants/phase change fluids and Silicones. A heat exchanger transfers solar energy absorbed in solar collectors to the liquid or air used to heat water or a space. Types of exchanges are air-to-liquid or liquid-to-liquid. Heat exchangers can be made of steel, copper, bronze, stainless steel, aluminum, or cast iron. Solar heating systems usually use copper, because it is a good thermal conductor and has greater resistance to corrosion. This heats the water that then flows into the home. They are popular in climates prone to freezing temperatures.
There are two basic types of passive systems:

Integral collector-storage passive systems:
These work best in areas where temperatures rarely fall below freezing. They also work well in households with significant daytime and evening hot-water needs.

Thermosyphon systems:
Water flows through the system when warm water rises as cooler water sinks. The collector must be installed below the storage tank so that warm water will rise into the tank. These systems are reliable, but contractors must pay careful attention to the roof design because of the heavy storage tank. They are usually more expensive than integral collector-storage passive systems.
Passive Systems:
Advantages: Cheaper to run, More maintenance free than active systems, can be more reliable and may last longer
Advantages of ICS system: perfect for areas where the temperature rarely drops below freezing
Advantages of Thermosyphon: works in all climates

Disadvantages: less effective than active systems
Disadvantage of ICS system: Not a good choice in cold climates.
Disadvantages of Thermosyphon: none
Active Systems:
Advantages: Way more efficient than a passive system
Advantage of direct circulation: Great for areas that don’t experience freezing temperature
Advantage of indirect circulation: Only choice you have in areas where temperature gets to freezing or below.

Disadvantages: more expensive to run, more maintenance problems due to the pump system needed to operate.
Disadvantage of direct circulation: If mercury levels fall too low, then it could create problems
Disadvantages of indirect circulation: None
Advantages of Solar Power:
Solar power panels can be used for a very long time, usually estimated around twenty years of continual usage before the need will arise for replacement. This means that once installed, there is very little maintenance involved, beyond possible battery replacement for models that use them. Also, unlike the installation and use of diesel or gas power generators, solar panels are completely quiet while supplying electricity to the home. So over time the solar panel system will save the owner extra money because owners will no longer have to spend so much on high electrical bills.
Disadvantages of Solar Power:
The big disadvantage about solar power is the initial price, which typically is about $32,000 for the proper installation to the home. And once installed, the system is there for good - if you decide to move, the system cannot come with you - it becomes a permanent fixture of the home. Also, if the need ever arises for the replacement or repair of roof tiles, the panels will need to be taken down, the repairs to the roof made, and then the panels reinstalled by a qualified electrician.
Solar water heater: Standard Water Heater:
Free energy from the Sun Costly gas or electric

Annual operating cost: $50 Annual operating cost: $500+
Storage Capacity: 80-120 gal Storage Capacity: 40-50 gal
Life expectancy: 15-30 years Life expectancy: 8-12 years
Lifetime operating cost: $1,000 Lifetime operating cost: $10,000
Does not pollute environment Depletes fossil fuels
Increases equity in your home No added value to your home
25% return on your investment No return on utility payments
Protection from future increases At mercy of utilities/government
Hot water during blackouts. No hot water during blackouts
Dexter Calhoun
PAP Physics
Integral collector-storage systems: (ICS) or batch systems feature at least one black tanks or tubes in an insulated, glazed box. Cold water passes through the collector that will preheat the water, and then continue to a conventional backup water heater, thus making the source of hot water. Should be use only in mild-freeze climates because severe, cold weather could freeze the outdoor pipes.
Evacuated-tube solar collectors: feature parallel rows of transparent glass tubes, within each tube; they contain a glass outer tube and metal absorber tube attached to a fin. The fin’s coating absorbs the solar energy but doesn’t allow radiative heat loss. U.S. commercial applications use these types more often than others.
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