Hot water represents the second largest energy consumer in American households. A typical 80 gallon (300 l) electric hot water tank serving a family of four will consume approximately 150 million BTUs in its seven year lifetime. This will cost approximately US$3,600 (at US$0.08 per KWH), not accounting for fuel cost increases. Then it will be replaced by another one just like it. Hmm. Maybe we should rethink this...
Generally accepted rules of thumb for solar thermal collector sizing based on your climatic region:
- In the Sunbelt, use 1 square foot (0.09 m2) of collector per 2 gallons (7.6 l) of tank capacity (daily household usage).
- In the Southeast and mountain states, use 1 square foot of collector per 1.5 gallons (5.7 l) of tank capacity.
- In the Midwest and Atlantic states, use 1 square foot of collector per 1.0 gallon (3.8 l) of tank capacity.
- In New England and the Northwest, use 1 square foot of collector per 0.75 gallon (2.8 l) of tank capacity.
Based on these rules of thumb, a household of four with an 80 gallon (300 l) tank will need approximately 40 square feet (3.7 m2) of collector in Arizona, 55 square feet (5.1 m2) of collector in South Carolina, 80 square feet (7.4 m2) of collector in Iowa, and 106 square feet (9.8 m2) of collector in Vermont.
For an excellent primer on solar hot water heaters go to: Solar Hot Water: A Primer
For an excellent introduction go to: How It Works , Solar Hot Water Basics ,
Solar Hot Water System Types: Advantages & Disadvantages and
What parts make a Solar Hot Water Heating System?
We offer two different Solar Hot Water Systems
Thermosyphon Systems
They are easily recognizable because the tank must be located directly above the collector.
Thermosyphon systems work on the principal of heat rising. Most open-loop systems are for nonfreezing climates only, potable water enters the bottom of the collector and rises to the tank as it warms. In colder climates these same systems TYPICALLY require an antifreeze solution, such as propylene glycol, is used for a closed solar loop adding freeze-tolerant piping, such as cross-linked polyethylene (PEX).
Alternative Energy Discount House systems (sold on this website) have several improvements over this as we use high quality welded, high conductive metal to transmit the heat into the storage tank instead of troublesome liquid such as glycol. PLUS our systems are "Closed Loop System" (water never runs through anything but FOOD GRADE material) as above, but WITHOUT THE DISADVANTAGES!!
In addition to this: our systems offer heat preservation layer between outer tank and inner tank. So neither pressure water tank or non-pressure water tank will freeze. This makes this system THE IDEAL SYSTEM.
Our pressurized systems are made for the higher pressures of city water systems. If you are "off-grid" using lower psi pumps you can use our "Non-Pressurized" (read: Low-Pressurized) systems and save money in the process!
These units can be used in freezing temperatures as well as tropical ones!
The advantage of this system over the batch heater is that solar heat is stored in a well-insulated tank, so hot water can be used any time, without the penalty of overnight losses.
The following illustration includes the primary components of any thermosyphon system.
Open-Loop Direct Systems
Most "Open Loop Direct Systems" are used in tropical settings where freezing never occurs and is the simplest of the active systems, our Flat Panel System comes with two freeze preventers.
Our systems offer heat preservation layer (rock wool).
These Flat Panel Systems offer yet another protection. Pressure! At 87 psi (pounds per inch) water has yet another freeze prevention mechanism.
These units can be used in freezing temperatures as well as tropical ones! This makes this an IDEAL SYSTEM.
One is the A standard, 52-gallon (200 l) electric tank can be used, teamed with a 40-square-foot (3.7 m2) solar thermal collector. Normally the electric element is not hooked up, so this tank becomes a storage tank only, for preheated water feeding an existing backup water heater.
We recommend hooking these simple yet powerful solar system into your current hot water heating system. The common system is a TANK which can now be used as a backup to your solar. Just by connecting the SOLAR HOT WATER to your current tank's COLD INPUT.
An air vent, automatic or manual, is installed at the high point of the solar thermal collector to initially purge air. The pump, a small circulator pump using as little as 10 watts, can be powered directly by a 10-watt PV module, or a thermostatically controlled AC pump can be used. A snap-switch sensor can be installed to limit the temperature the solar tank reaches. Standard snap-switch sensors are available for 160°F or 180°F (71 or 82°C).
The following illustration includes the primary components of any open-loop direct system.
