Updated 1/28/01
Introduction to Solar Hot Water Heaters
Comparison - Hot Water Heating
© Copyright 1999 By Charlie Collins From "Ask Mr. Solar" Column Mr Solar Newsletter # 53
Dear Mr Solar-
I am considering installing a solar hot water heating system in our home here in West Virginia and would like to know how you compare the output of the "flat plate collector" to the new Thermomax "vacuum" tube collector. Thanks Jane
Hi Jane
This is a very interesting question as we recently installed a system here at the "Do It" to heat our addition of an indoor pool. We will be updating our Web page with information that I have learned during this experience, which I might add was a real learning curve for both Fran and me. This update will take place over the next couple of months.
As you know, we have sold both; however, as of the first of November, we are dropping the flat plate one and only carrying the vacuum tube type as we feel that it is the best, and the best is all we care to offer to our friends.
In researching, we've found that vacuum collectors are more efficient than conventional type collectors and will perform considerably better in cold, cloudy and windy conditions. Vacuum is the best possible insulation for a solar collector. It also safeguards the collector from moisture and pollutants, resulting in increased durability. A vacuum collector is compact and neat in appearance. The low water content in its system means water will become available more quickly than with flat plate panels. This is particularly beneficial in winter when days are short. The following is a recent report and data that you may find interesting.
The weather data used in this is a set of statistically generated sunlight conditions that quite realistically emulates real conditions. A given month's data is a combination of bright sunlight days, totally cloudy days and partially cloudy days. The table indicates the energy collected per Meter squared for both the Thermodynamics and the Thermomax systems used for this study. The third column is a ratio of energy collected by the evacuated tube compared to a flat plate collector. Note that the evacuated tube collector is approximately 1.6 to 4 times more effective than a flat plate collector and therefore they produced that much more heat for your usage. The higher efficiency results in the evacuated system having a frontal collector area of only 3 square meters compared to a flat plate collector area of 5.96 square meters. Therefore you have to also consider the space available for your installation.
| Thermomax Vac System |
Flat Plate | Ratio Vac / Flat | |
| January | 53 |
12 | 4.08 |
| February | 123 | 54 | 2.28 |
| March | 223 | 116 | 1.92 |
| April | 310 | 180 | 1.72 |
| May | 387 | 232 | 1.67 |
| June | 393 | 243 | 1.62 |
| July | 437 | 223 | 1.64 |
| August | 357 | 223 | 1.60 |
| September | 240 | 84 | 1.94 |
| October | 163 | 84 | 1.94 |
| November | 67 | 23 | 2.91 |
| December | 47 | 10 | 4.70 |
So, we went with the vacuum tubes made by Thermomax; however, we soon realized that our system was greatly undersized due to several factors. As I said, it was a real learning curve for us.
You see, we had a 1100 square-foot room with a pool of approximately 330 square feet of surface area, in addition to wanting to heat our water for our daily usage.
We have learned that it takes: 30 tubes to provide an average family with hot water, 3 tubes per square meter of surface of indoor or covered outdoor pool, and 1-3 tubes per square meter for heating area.
So, this converts into a system that will consist of at 10 times the amount of collectors that we have at this time, as well as increased the storage of our system and get a larger heat exchanger units that will provide adequate heat transfer for our system.
We have since made arrangements with a professional solar heating engineering group, which has helped us redesign our system. They are available to take your plans and design a balanced working system for you, so you will not have to go through the experiences we went through.
We have decided on using a propane heater to heat the water and this only cost us about $3.00 per day or actually it cost $1.00 to raise the heat of our pool 1 degree - so this being much more economical we have gone this route.
So, Jane - we are now in a position to offer you the same service on solar heating that we offer in solar electricity. We want you and all of our friends to be happy with the products that you buy from us, and not be disappointed due to a "cheap" starter system that will not provide you with the necessary heat or power.
Charlie Collins AKA "Mr. Solar"
Solar Hot Water Problems© Copyright 1995 By Charlie Collins From "Ask Mr. Solar" Column Published Daily Spectrum
Question from Elizabeth Mead, Colorado
Question:
I live in a small town in the foothills west of Denver, Co. The house we live in has an active solar hot water system. It is several years old. We had some problems with the circulation pumps. We had those replaced. The pumps worked, but it seems the heat exchanger is plugged. We did find some deposits in the pumps when we had them replaced. I am assuming there are deposits in the heat exchanger also. The repairman seemed to think that there was no way to clean
the heat exchanger because the cleaning agents needed to be corrosive and we could not use anything like that because we don't want it in our hot water system in the house. There was also the chance of causing leaks in the exchanger if we use something to try to scrape out the deposits. We have a 65 gallon holding tank in the basement. When this system worked it was great. I have three daughters, so you can imagine how much hot water we use every day.
The repairman quoted us a price of $700.00 to replace the exchanger (providing he could find one, as this system is several years old) He had advised me, he had found one in New Mexico for $695.00. That was the last we heard from him. It has been probably two years since then.
Do you know of anything we can use to clean the heat exchanger? If not, do you know of anyone who sells them for older systems? I would hate to think the whole system is shot because of the bad heat exchanger. Maybe there are different types of heat exchangers that would work? I haven't found a whole lot of inf. on these type of hot water systems.
In the future we would like to expand the system to use with a hot tub. (if we every get it working)
Well, thank you for your time. I am glad there is a place to get inf. about solar stuff on the World Wide Web. I haven't had much luck.
Thanks again. I am looking forward to hearing from you.
Mr. Solar:
Hello Eliz - This is a problem that we have also in this area, it is due to a high mineral content in the water and I have found a very simple solution for it. First I would like to say that we do NOT use a solar hot water system for the reasons that you describe, as I know that I can heat water with propane or natural gas for about $25.00 per month for the two of us, and compared with investing in a solar water heating system coasting about $3000.00. It would take 10 years to pay for it, and before that time I would have to replace it. I have gone to a instant hot water system as I find that it is the most economical for our use. I also realize that using a tank type hot water system is very uneconomical as we would be wasting energy having to heat the whole tank. Actually the main reason that I went to a tankless type water heater is so that my dishwasher would not electrically heat the water to do the dishes, very uneconomical when you are solar powered electricity.
I had a problem with my electric coffee pot as it plugged up after several weeks. I realized that it was due to a build up of chemicals and therefore I tried to remove these with vinegar which corrected the problem. I also use the "magic vinegar" in my last rinse on my dishwasher and presto my dishes are shinny.
My propane tankless water heater was not getting the water hot so what I have done is to install a Vinegar cleaning system. By this I mean that I now have a separate holding tank connected to my hot water system at the tankless heater. Every month or two I turn the incoming cold water off and add about a gallon of vinegar to my holding tank. I then open the valves so that the incoming cold water will carry the vinegar through the tankless water heater. I then open the hot water valve, just long enough to activate the heater. I do this several times in order for the vinegar to react with the minerals and clean the pipes.
I suggest that you contact your plumber and local people before trying this as maybe it would not work for you or maybe it may cause problems, all I am saying is that it does work for me. And you may want to try it on your own system, but check it out completely to prevent any problems which we cannot be responsible for.
Introduction to Solar Hot Water Heaters
© Copyright 1992 By Charlie Collins From "Ask Mr. Solar" Column Published 10/18/92 Daily Spectrum
Question: We are very interested in solar HOT water and are confused about the many types, would you explain each to us? Thank you.
Ray & Mary Cowley, La Verkin, Ut.
Mr. Solar: Ray, this is a very timely subject and to do it justice we are planning on spending the next several weeks explaining each type. Heating There are several types and they all have merit. Water is the second largest load of the average home. Solar water heating is an excellent companion to solar electric, but until now has had its share of problems. We have watched the solar water heating for some time and have not invested in solar hot water equipment for the Do It because of the many problems. One of the reasons that solar electric has been so successful is that there are no moving parts and therefore if the system is installed properly with good UL approved equipment by a solar electric professional then it will work for years trouble free. That has not been the case with solar hot water. We will start with the simplest type of hot water system, the bread box and explain all the basic systems that can be customized to fit your needs. Our explanation will end with the Copper Cricket which is by far the best on the market to date. (Update 7/26/95 - Note they are out of business)
Solar Hot water is quite different from solar electric in that you are only heating water and you only can get hot water from your system. In solar hot water you will find that you should have your system checked by a solar hot water specialist at least once a year. The reason that you should do this is because you will find that your pumps may need replacing every few years. You should have your system cleaned and back flushed yearly depending on the amount of corrosion in the pipes to word off future problems.
We understand that approximately half of the older solar hot water systems in this area that were installed years ago may not be working. We feel that this is due to either improper installation or the owners not following a maintenance plan. This plan should include having a solar hot water professional check your system yearly. A solar hot water system differs from a solar electric system in that it has many moving parts and needs to be serviced yearly.
Solar hot water heaters can cost you from $1,000 to $3,000 materials, depending on the type and amount of hot water that you want to use. That may seem as a lot of moneys however your hot water is the most costly monthly expense that you now have. A well designed system properly installed and maintained will give the homeowner years of free hot water.
Ray, according to the department of Energy the American people use on the average of
10 to 20 gallons of hot water each day. What we will give in these articles is an
outline of the various types of solar hot water heaters. However should you wish
to have a properly designed system please let us know how many people in your family
and we will be happy to have our trained solar Hot water associate meet and design
a great system for you. We suggest that you wait until after these series of
articles have beep printed so that you will better understand Solar Hot Water.
Bread Box Hot Water Heater
© Copyright 1992 By Charlie Collins From "Ask Mr. Solar" Column Published 10/26/92 Daily Spectrum
Question:We are very interested in solar HOT water and are confused about the many types, would you explain each to us? Thank you.
Ray & Mary C., La Verkin, Ut.
Mr. Solar: Ray, this week we are going to explain the simplest type of solar
HOT water heater, the bread box. This is the simplest of all solar water heaters.
They consist of a black painted water tank placed inside of a insulated weatherproof
container with the sun facing side covered with a transparent service. The side that
is facing the sun is usually painted black so that it will also absorb heat and help
increase the heat in the tank. The water then moves through the pipes into the standard
water tank as someone turns on the hot water.
The major advantage of this type is that it is a very low cost and the materials usually cost between $500.00 and $800.00 plus the installation. Since it has no motors or other moving parts it is completely non polluting. The major disadvantage of the bread box type of solar hot water heater is that it has a tendency to loose the heat at night as well as freeze on very cold nights, unless it is drained.
Ray, in the weeks to come we will discuss several other types of solar hot water
heaters.
Question:
We are very interested in solar HOT water and are confused about the many types,
would you explain each to us? Thank you.
Jim S Mr. Solar: Ray, we will continue our outline of solar hot water systems
and this week we will discuss theromsyphon Solar hot water systems. They operate in
the principle that the natural convection of liquids to collect solar heat. As you
know liquids expand when there is a rise in temperature and therefore the worm
liquid is lighter than the cold and therefore rises.
In designing a theromsyphon Solar hot water system it must be designed with the
storage tank above the collector to operate efficiently.
Basic Passive Solar Hot Water System
© Copyright 1992 By Charlie Collins From
"Ask Mr. Solar" Column Published 11/1/92 Daily Spectrum
Apple Valley, Utah
The sun strikes the solar collector and the warm water exits the collector "D" and into the water tank storage tank at "E". Then when someone turns on the hot where tap it leaves the tank at "F". The cold water then enters the loop at "A". As the water in the collector becomes hot it will automatically leave the collector at "D" and more water will be drawn into the collector at "C".
This system is a little more complex than the bread box , however remember that the collector must be below the storage tank to operate correctly. The major advantage of this type is low maintaince, no operating cost and is reliable. However it should be back flushed and treated yearly to prevent scaling in the pipes. One major disadvantage is that this system tends to freeze in the winter. The cost of this system for the equipment runs from $500.00 to $800.00 for a single panel set up.
Ray next week we will discuss the closed loop system using antifreeze in the system
which will prevent freezing.
Question:
We are very interested in solar HOT water and are confused about the many types, would
you explain each to us? Thank you.
Ray & Mary C., La Verkin, Ut.
Mr. Solar: Ray, we will continue our explanations of solar hot water systems
and this week we will discuss a simple active solar hot water system. This is a
much more complicated system, however many people have installed them and do
enjoy using them trouble free. It is very important that you have a solar water
heater professional install and check them yearly so that you to will enjoy using it.
Active Solar Hot Water System
© Copyright 1992 By Charlie Collins From
"Ask Mr. Solar" Column Published 11/8/92 Daily Spectrum
As you will notice by the drawing the cold water enters "A" and the hot water exits through "F" from your hot water heater. This water is pumped "P" through a heat exchanger which is a copper coil surrounded by antifreeze solution that has been pumped from your solar collector. The main advantage is that the pumps are controlled by heat sensors and therefore there is no heat loss from your hot water at night as in the basic passive ones.This pumping can be set up with solar electric panels which when there is no sun they do not pump as there is no electricity. This system must be checked yearly as it has several moving parts.
A major advantage of the active system is that the collector is mounted on the roof
above the water tank and it is more efficient for year around water heating. This
system can easily be expanded to a drain back system which means that when the
when the system shuts off then automatically the fluid from the collectors will
be drained into a holding tank. The price of this system is about $1500.00 for
parts for a single collector. As pointed out this is for the materials only and
does not include hooking in to your system or other labor.