SOLAR HOT WATER
FREQUENTLY ASKED QUESTIONS
How Much Energy Can I Save?
Solar hot water heating is the most common and popular way to use
solar energy. You can reduce the amount of energy you use
to heat hot water by 60% by installing on of these solar systems.
How Does It Work?
The way it works is quite simple. What Solar Energy Solutions
does is install two 4' x 8' solar panels on your sunny South or
West facing roof. Then we install an 80 gallon solar preheat
tank which as the name implys, simply preheats the water using the
solar panels before it goes into your existing hot water tank. So,
when you turn on your hot water faucet, instead of sending freezing
cold tap water into your existing hot water tank, you send preheated
water from your new 80 gallon solar preheat tank. This vastly
reduces or eliminates altogether how much energy your existing tank
uses to reach its desired temperature.
Does It Matter What Kind Of Hot Water Heater
I Currently Own?
It really doesn't. If it is an 'on demand' hot water heater, you
just have to make sure it is 'solar compatible'.
Where Will The 80 Gallon Preheat Tank Be Located?
Ideally, the 80 gallon solar preheat tank is located as close to
your existing hot water heater as possible. However, it can
be located on the opposite side of a basement or even on a different
floor. Some systems even have the 80 gallon solar preheat
tank mounted up on the roof.
How Hot Will The Water Get?
The temperature coming out of your 80 gallon solar preheat tank
varies according to the time of year and hot water usage.
Homes generally save about 100% of their hot water energy needs
in the summer, 60% in the spring and fall, and 40% in the winter.
This is a huge energy saving considering hot water heating is the
second largest energy drain a house suffers from.
So .. Can I Heat My House With Solar Panels?
Sadly, households cannot be heated using solar panels West of the
Cascades because that time of the year, when you need the heat most,
we have our greatest cloud cover and the sun in lowest on the horizon.
What Are The Different Systems You Install?
Solar Energy Solutions, Inc. carries and installs three of the most
popular system configuration for heating hot water, the Glycol system,
the Drainback system and the Thermosyphon system. All three
configurations have passed the 40 year test of time. This
is truly a remarkable feet when one considers all of the systems
that have come and gone during this same period of time.
Which System Is Best?
The thing to remember about solar hot water heating is that no system
configuration is perfect. All system configurations have their
own little things that make them better or worse than other system
configurations. We have yet to discover a system configuration that
is perfect in all ways.
What Are The Differences?
With the Glycol and Drainback system configurations there is a heat
transfer fluid which is circulated from the solar preheat tank to
the solar panels and back. The heat is transferred from the solar
panels to the solar preheat tank using a pump and a differential
controller. The controller has two sensors, one is located
sensor is located by the solar panels and the other by the cold
spot of the solar tank. If the controller senses the
panels are warmer than the tank it automatically turns on the pump.
The pump circulates the heat transfer fluid which extracts the heat
from the solar panels and puts it into the 80 gallon solar preheat
tank. The Thermosiphon system configuration works a bit differently
and is discussed after the Glycol and Drainback systems. What
makes it great is that it does not use any pumps or controls or
even electricity at all. That’s because it is a passive
solar hot water heating system.
Below are descriptions of the three kinds of solar
hot water heating systems Solar Energy Solutions, Inc.
advocates, carries and installs.
GLYCOL SOLAR HOT WATER HEATING SYSTEMS
Glycol solar hot water heating systems may currently be the most
prevalent system configuration installed today. The
reason for this system configurations prevalence is due to its lack
of solar loop plumbing specificity and ease of installation.
Most commonly these systems will consist of two 4 x 8 solar collectors
and an 80 gallon solar preheat tank. There are some variations
of this, but this is the most common setup. Glycol systems
allow for the greatest amount of flexibility in the plumbing of
your solar system from the solar preheat tank to your solar panels.
In other words, the plumbing from the solar preheat tank can go
over hill and dale, inside the house, outside the house, do loopty
loops if so required, because the fluid in the pipes can’t
freeze. The heat transfer fluid is a non-toxic, propylene
glycol and is freeze proof.
The advantages of the Glycol system other than the
ease of installation and flexibility in plumbing scenarios are that
it puts out the greater energy yield than other system on a yearly
basis and, it doesn’t make any more noise than your refrigerator.
The only down side to this system is it has a built in maintenance
schedule. Every 8-10 years the glycol needs to be switch out
for new glycol and the expansion tank replaced. This service
call currently costs between $400.00 and $600.00.
We install the SunEarth panels along with the Rheem
80 gallon solar preheat tank. SunEarth calls their glycol
system, "The Solaray".
You can view The Solaray by clicking
here.
If you want SunEarth Panel information click
here.
Then, if you are really technically oriented you could look at the
install manual by clicking
here
DRAINBACK SOLAR HOT WATER HEATING SYSTEMS
The Drainback system configuration is probably the most
maintenance free of any system configuration. Most commonly
these systems will consist of two 4 x 8 solar collectors and an
80 gallon solar preheat tank. There are some variations of
this, but this is the most common setup.
The Drainback system uses the same SunEarth solar
panels, same 80 gallon solar preheat tank, controller, sensors,
valves and gauges as the glycol system. What makes the Drainback
system different is its freeze protection. The Drainback system
freeze protects itself by draining all of the solar heat transfer
fluid (in this case distilled water) into a separate 10 –
15 gallon Drainback tank. When there is a heat gain to be
had, the small circulating pump turns on and pumps the heat transfer
fluid form the 10 – 15 gallon Drainback tank, up to the solar
panels and then back down to the heat exchanger on the solar preheat
tank. When the pump is not pumping, all of the
heat transfer fluid automatically “drains back” into
the 10 – 15 gallon Drainback tank.
The Drainback system configuration, unlike the Glycol
system configuration, requires a great deal of solar loop specificity.
The solar panels actually have to be mounted on the roof so as to
give them a slight slope. As a matter of fact, the entire
solar loop plumbing from the solar tank to the panels, needs to
be plumbed giving the pipe a certain degree of slope or fall.
This is essential to this system configuration as this system’s
freeze protection is all based upon the entire solar loop plumbing
line and solar panels being completely devoid of the heat transfer
fluid during freezing temperatures. It is the rigid
technical specification of this slope that prevents the Drainback
system configuration from being installed in many homes. Often
times it is impossible to get the required solar loop plumbing slope
needed, thus eliminating the Drainback system configuration as an
option.
There are a couple of other disadvantages to the
Drainback system configuration. The Drainback system makes
more noise than the Glycol system. The sound it makes is most
like the sound of popcorn popping on a stove. It never happens
at night, but if you are sensitive to noise you will definitely
hear it in the day if you are anywhere near the drain back tank
while the system is running. The other disadvantage to the
Drainback system configuration is that its annual energy yield is
about 200 kilowatt hours less than the Glycol system.
However, the Drainback system configuration has
no built in maintenance schedule at all. We have seen these
systems running maintenance free often time for 20 – 30 years.
This is incredible and certainly makes it worth thinking about.
You can see the SunEarth Drainback system,
which they call, "The Cascade" by clicking
here
If you want SunEarth Panel information click
here
Then, if you are really technically oriented you could look
at the install manual by clicking
here
THERMOSIPHON SOLAR HOT WATER HEATING SYSTEMS
Thermosiphon Solar Hot water Heating Systems are, “Passive”.
This is to say that no electricity is used to heat the water in
the 80 gallon solar preheat tank. With the Thermosiphon systems
instead of having the 80 gallon solar preheat tank installed near
your existing tank, the 80 gallon solar preheat tank is mounted
on the roof above the panels. To see a picture of this system
click here: The way these systems work is by plumbing your
cold water to the 80 gallon solar preheat tank on your roof, and
then back down to your primary hot water heater. The solar
tank on your roof is heated by the solar panels mounted right below
it. The solar panels have a heat transfer fluid in them, propylene
glycol. When the sun strikes the panels it heats up the glycol.
The hot molecules in the glycol then rise to a heat exchanger that
is actually wrapped around the outside of the 80 gallon solar preheat
tank on the roof. This kind of heat rise is called thermo
siphon, or stratification. All the solar heat gain going into
the 80 gallon solar preheat tank is being done through natural laws.
Heat rises cold falls. To better understand this concept
click
here.
The Thermosiphon solar hot water heating system
is perfect for folks who can appreciate its passive nature.
It is also best used in situations where there is a big demand for
hot water.
One disadvantage to the Thermosiphon system is that
it has no brakes. What this means is if you are away in the
middle of the summer you will either have to cover the system up
to turn it off, or, except the fact that it will blow its temperature
and pressure relief valve, thus harmlessly releasing hot water on
to your roof until, it has cooled off sufficiently. And speaking
of cooling off… the potable plumbing which goes from you
existing tank to the 80 solar preheat tank on your roof is also
susceptible to freezing during very, very, very cold stretches of
weather. The pipe will not burst because we use “PEX”
piping for this application. PEX pipe is burst proof.
But, the possibility does exist where an ice blockage in the plumbing
could develop if it got cold enough. This would mean no hot
water coming out of your hot water faucet. But, once again,
this is really no big deal. We install a bypass valve.
So, all you would have to do is flip a single valve and presto,
you would be back in hot water. We super insulate the plumbing
on these systems and have not had a pipe freeze, as just mentioned,
since 1996. There is one last thing to consider with the Thermosyphon
system. The 80 gallon tank on your roof has a wet weight of
1,000 pounds. This means some structural adjustments will
have to be made. This could mean doubling up the rafters or
posting down to a load-baring wall… no big deal really.
All of this said, the Thermosyphon system is probably
the most commonly and popular of solar hot water heating system
configurations in the World. This is because it is passive.
The manufacture we have chosen to represent for this system configuration
is Solahart. Solahart is probably the largest distributor
of all solar hot water heating systems in the world.
You can visit their web site by clicking
here
The system we install is the Free Heat system.
You can see this by clicking
here
We like this system because of the 10 year warranty.
In the past 20 years we have install a bunch of Solahart systems.
They are probably the favorite for folks who like do-it-youself
projects.
No matter what system configuration you choose,
you will get decades of maintenance free use and loads of free hot
water!
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