Solar Hot Water<br />Noel Montiel<br />Justin Thomasson<br />
Solar Batch heaters<br />ICS (integrated collector storage)<br />A container is placed in an insulated box, cold water is pumped into the bottom of the system and hot water drains off the top into the bottom of the backup water heater which causes hot water to be pushed out into the house to be used. Potable water is heated directly, making this an open-loop system. No pump is used to move the water from the collector so it is passive. Commercially manufactured batch heaters come at a relatively low cost, and are popular in moderate climates were hard freezes are not an issue.<br />
Thermosyphon system<br />Another simple passive system and probably the most well known is the thermosyphon. The tank must be located directly above the collector, as the system works on the principal of heat rising. It comes in both open and close loop systems depending on your climate. In an open-loop version potable water enters at the base of the collectors and rises to the tank as the sun heats it up. In closed-loop variants an antifreeze solution is used in the closed solar loop and freeze- tolerant piping is used for the potable water lines. The advantage this system has over batch heaters is that hot water is readily available at any time because the solar heat is stored in a well insulated tank.<br />
Open-loop Direct system<br />This system is used where freezing never occurs. It is the most simple an active system. A standard 52 gallon electric tank can be used with a 40 square foot solar thermal collector. The tank is usually used as storage for preheated water, feeding an existing back up water heater. An air vent is added at the high point of the solar collector to purge air. The pump can be as little as 10 watts. A snap switch sensor can be installed to limit the temperature the tank reaches. <br />
Pressurized Glycol Systems<br />In this active, closed-loop system, incoming potable water is routed to the solar storage tank, but never into the collectors. A water and antifreeze mixture circulates from the collectors through a coil of pipe in the solar tank, and then is pumped back through the collectors. (In most climates, a 50/50 propylene glycol and water mixture will keep collectors from freezing.) The potable water is warmed by heat transfer through contact with the pipe.<br />These systems require an expansion tank and a few other auxiliary components for filling, venting, and maintaining the system. A definite advantage to antifreeze systems is that the collectors can be mounted anywhere. These systems are pretty much the only choice in very cold climates.<br />
Close-loop Drain Back Systems<br />This system requires the least routine service of any active system. The fluid used for heat transfer is distilled water and requires almost no changing. When at rest the solar collector is empty and the distilled water drains to a reservoir tank. When turned on the distilled water is pumped back through the collector and heat exchanger, passing heat to the water in the solar tank. The collector must always be higher than the storage tank, and there must be sufficient slope to ensure against freezing pipes. This system is effective and reliable, work great regardless of climate and can operate around 20 years without service. The downside is that larger pumps are usually necessary.<br />
Solar Hot Water System Components<br />Solar Collectors- Where the water is Heated<br />Collector Mounting System- how the collector is mounted<br />Solar Storage Tank- Insulated Water storage tank<br />Water Pump- used in active systems to circulate fluids<br />Heat Exchanger- Used in close-loop systems where one fluid transfers heat to another without contact.<br />Expansion Tank- used in close-loop systems to account for gas expansion in the sun.<br />Controls- in active systems using pumps, whenever the collector is hotter than the storage tank, the pump should be on and the system circulating. When the tank is hotter than the collector, the pump should be off, controls take car of that.<br />Isolation Valve- Isolates the solar tank in case of a problem.<br />Backup Water Heater- ensures hot water regardless of sunshine.<br />Tempering Valve- saves you from water that got to hot.<br />
Conventional Heaters<br />#1 household energy consumer is the hot water system<br />Most expensive household appliance is a conventional hot water system<br />35% of household cost is dedicated to hot water<br />Produce 4-4.5 tons of greenhouse emissions each year<br />
Benefits<br />3.5 to 4.5 thousand dollars<br />Savings from 300 to 800 dollars a year <br />The average buy back time is approximately 6 to 7 years<br />
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