Solar thermal, a term meaning of or relating to heat has several solar applications. This page has several sub pages each describing some of the different applications along with basic consumer information. Here is a brief overview:
HOT WATER HEATING
Here we mean domestic hot water backed up by solar heating. This is showers, baths, dishwashing, laundry, etc. It is probably the single most common type of solar installation on a worldwide basis.
This too, involves heating water as a backup for radiant floor heating. Solar water heating can also work with baseboard water heaters and radiant wall panels as long as they are the low temperature European style units. Since radiant heating is a hot water application it is usually combined with a domestic hot water system. These are called combisystems.
HEATING HOT TUB WATER
It is most economical in conjunction with a solar hot water system or combisystem. Older tubs especially, often have big electric bills associated with them and solar can in many instances give a good ROI.
HEATING SWIMMING POOLS
Not a big market in this area, but if someone wants to warm up an outdoor pool during the non-freezing time of year, a very economical type of solar panel can be sized to raise the pool temperature about 15 degrees F. Keep in mind that about 75% of pool heat loss is due to evaporation so pool covers when the pool is not in use are worth the money. Indoor pools are best heated by year round flat plate solar collectors, a more substantial system.
DIRECT AIR HEATING WITH AIR COLLECTORS
Most of the multi collector systems around Durango that date back to the 70's and 80's are of this type. They are actually the most efficient solar application with the highest ROI and one brand which we sell is eligible for the 30% federal tax credit. They can be an excellent auxiliary heat for homes with forced air furnaces. An excellent application is for garages or any kind of shop building where its use is largely confined to the daytime. Call us for a free flyer that we will mail to you.
TRANSPIRED WALL SYSTEMS
For commercial buildings requiring make up air consider a transpired wall system commonly known in Canada as the SolarWall or in the US as the InspireWall. The savings from these systems often make for one of the fastest paybacks in the industry. It is eligible for the 30% federal tax credit and 5 year MACR depreciation, the two combined often being worth 50% of the cost.
PHOTOVOLTAICS VS. SOLAR THERMAL
If you are uncertain which system type is best for you keep in mind that solar thermal systems are often as much as four times more efficient at producing heat than a photovoltaic system producing electricity. This does not mean that a thermal system will cost 1/4 the cost of a photovoltaic system. It does mean that over time it is not unusual for a thermal system to save more money than that saved by a photovoltaics system.
At Solar Today and Tomorrow we are able to do all of the above and will be
happy to come to your home or facility for a free site analysis, no obligation and no
sales pitch, just a friendly explanation of what's possible.
"You pay for a solar hot water system whether you buy one or not."--Tom Lane (2004), author of Solar Hot Water Systems, Lessons Learned 1977 to Today
SOLAR HOT WATER SYTEMS
Solar energy has two basic applications: 1) photovoltaics to produce electricity, and 2) solar thermal or heating. The latter is primarily about heating water and sometimes applications to heat air. This page is concerned with water heating of what we call dhw (domestic hot water) or sdhw (solar domestic hot water). This is the water that is used for the dishwasher, food preparation, laundry, showers, and baths. How much of this hot water can a solar thermal installation in southwest Colorado realistically supply? Easily 80% over a year's time and up to 100% in the summer. That would make solar the primary source of heat with electricity, natural gas, or propane as the secondary backup.
How reliable, efficient, and maintenance free are solar thermal systems?
Let's put it this way: they are not the systems of your father or grandfather. From 1977 to 1986 the solar thermal industry enjoyed a 40% tax credit. Many large corporations introduced systems that didn't work for long--they had design flaws, were too complex or too expensive. A few were effective and are still working today. However much has changed since the solar boom years that ended in 1986 when, seemingly, the energy crisis of the 70's was forgotten and oil was again king and cheap. No more worries. Till now. There is a growing appreciation that fossil fuels are not infinite or cheap to access; and while coal, the direct competitor with most solar applications, is in abundant supply for now, there is a growing concern for its true cost in pollutants and CO2 emissions. In short, no more boom and bust for solar and now that the solar thermal industry is in its second generation, it has grown slowly and steadily in a sensible manner without all the quality problems that went with the aforementioned boom period. Today's solar thermal technology has come a long ways and is truly reliable, effective, and low to no maintenance.
So, what does a solar domestic hot water system cost?
Here are some facts about cost to consider:
1) The Dept. of Energy says that electricity costs grew 24% in Colorado over the four years before the recession. This is about 5% inflation per year compounded.
2) LPEA says a sdhw system will cost somewhere in the range of $7000 to $12,000. $9500 is a good median number.
3) There is a federal solar water heating tax credit of 30% of the system cost and you can roll it over from one tax year to the next until you use it up.
4) The magazine Journal of Appraisal says that for every dollar saved annually in energy bills with a solar system, $20 should be added to the value of the home. If, for example, you save $500 per year in utility costs, then at a multiple of $20 your home is worth $10,000 more.
5) Your ROI will be 6 to 7%. This is better than most investment vehicles and you have made a meaningful contribution to the health of planet earth, a matter of unquantifiable value.
What about commercial applications?
The tax credit is 30% and the MACR accelerated tax depreciation method can be utilized over 5 years so that the sum of the two could realistically be the equivalent of a 50% savings off the initial cost of the solar system. If you own a car wash, laundromat, restaurant, hotel, motel, or institution you probably use a lot of hot water. Since these types of businesses usually have access to cheap natural gas it might seem at first like solar heating would not be cost effective, but due to economies of scale and the fact that the heating demands are often in real time (less hot water storage required) solar heating can be a good deal even as a replacement for natural gas.
What about tankless water heaters?
These are growing in popularity and it seems that just about everybody asks about them as an alternative. Tom Lane, author of Solar Hot Water Systems says: "Tankless water heaters do save space, but not much energy. Numerous tests by independent third parties, have shown only 10% savings versus conventional electric water heaters and 15% to 20% savings versus energy efficient conventional gas water heaters over a 24 hour period. Most manufacturers of these expensive water heater systems exaggerate the savings. Daily savings quotes of 25% or higher versus modern electric or gas water heaters are simply not true. In 2004, hot water manufacturers were required to add additional insulation to all water heaters, making instantaneous water heater savings more insignificant. Tankless water heaters have serious problems with scaling in hard water areas." So when the true percentage savings of the instantaneous tankless heaters is compared to the 80% for solar, then solar is usually the obvious choice. But if you can't do solar for whatever reason or need to save space and don't have hard water, then a tankless heater might be right for you. A tankless heater could also be the backup for solar.
So there you have it, and the quote at the top of this page makes perfect sense. If we don't buy a solar hot water system, we have as good as paid for one with never ending utility bills and the money that could have gone to our pocketbook is given to the utility company instead. So if you think a solar hot water system will work for you, please give us a call or use the contact page to email us and we will be happy to set up an appointment for a solar site analysis to see what kind of installation is possible.
For purposes of solar, when we talk about radiant space heating we are referring to solar energy to heat the fluid running through the in-floor tubing of a radiant heated structure. It can also apply to radiant wall panels, free standing radiators, or radiant wall baseboard units. If you haven't looked at the Hot Water Heating page you may want to take a look at it because much of its content applies to solar radiant space heating as well. The one big difference between solar domestic hot water and solar radiant is that with the latter there's more of it--more collector panels and more water storage tanks.
How much of the space heating is a practical goal for solar?
With domestic hot water we said that 70 to 80% of the annual requirement is realistically achievable in Southwestern Colorado. Up to 50% to 70% is probably realistic for space heating. It is not practical to provide 100%. The dead of winter has the shortest days for accumulating solar heat, but as we move away from the winter solstice toward spring and fall the days are progressively longer and warmer with solar radiant providing closer to 100% of the heat demand. If we were to size a solar system to provide 100% of the heat on the coldest and shortest winter days we would have too much heat at other times. If we size the system to provide the heat for a sunny average winter day, then over the length of the entire heating season our solar system will have still provided a significant amount of the heating requirement without overheating the system.
Can a solar radiant and domestic hot water sytem be combined? They most certainly can and are sometimes called combi or hybrid systems. The two combined should be cheaper than the two summed separately, a good reason to do both.
What does a solar radiant system cost?
Maybe two to three times the cost of a simple domestic hot water system as discussed on the Hot Water Heating page with a median cost of $9500. It's like buying a new car, the big difference being that this "car" earns or saves a lot of money over time. There are several variables that determine the cost, the most important being your home's heat loss in btus, space available for heat storage and collectors, and finally your budget. After your site analysis, we will work up a bid/proposal along with a financial analysis. The 30% federal tax credit also applies to residential solar radiant just as it does to solar domestic hot water. With commercial there is also the MACR depreciation over 5 years for a total tax equivalency of about 50% off the cost.Can a solar radiant and domestic hot water sytem be combined? They most certainly can and are sometimes called combi or hybrid systems. The two combined should be cheaper than the two summed separately, a good reason to do both.
What if I don't have enough room on a south facing roof for all the solar collectors needed to do the job?
If you have a suitable location on your property you might want to consider a ground mount. In our climate the structure should be elevated on concrete columns a suitable height above snow accumulation (2 or 3 feet). An underground trench is dug, insulated piping is installed, and the heated fluid is piped back to your home. While a roof mount is often ideal, some roofs and attics make for such a challenging installation that a ground mount is sometimes actually cheaper and easier to install. Snow can also be quickly and easily removed after a snowfall.
Are all solar thermal collectors the same?
No, there are two types. One type is the flat-plate collectors that look like roof skylights. Evacuated tube collectors are the other type. These are cylindrical tubes of glass with the air removed to create a vacuum around the heat absorber, a metal plate and tube running down the center of the glass tube. Because of the vacuum very little heat is lost from the absorber back into the atmosphere as is the case with the flat-plate collectors. Primarily for this reason evacuated tubes are more efficient than flat-plate collectors during the winter and might be the better choice for radiant heating. They can also be used for solar domestic hot water. There are pros and cons to both and we would be pleased to discuss these with you if you want to learn more.
How does solar radiant compare with ETS (Electric Thermal Storage) heating units?
These are popular in this area and are available through LPEA. They have bricks in them that are heated with electricity at LPEA's off peak rate under its TOU (time of use) program. The bricks then become the heat storage material as opposed to solar radiant's water in a tank. The heated bricks can then exchange their greater heat with the heat of the fluid in the radiant tubing to keep it at the desired temperature. The off peak rate might seem pretty good, but it's a little more complicated than this because many other electrical activities in the home will probably be powered at the on peak rate. This means that about 44% of the total energy consumption has to be at the off peak rate just to break even with those who don't go with the time of use program. For a house 2000 sf to 2500 sf a large ETS unit hooked up to the radiant system can cost $10,000 installed. How does this compare to the cost of a solar radiant system? If you had a combisystem (domestic hot water and solar radiant combined) that cost $20,000, the difference is $10,000. Now subtract the 30% federal solar thermal tax credit to arrive at $14,000 which means the solar system costs $4000 more in this example. But with the ETS unit you pay for every kwh while the solar system could easily be saving you $1000 a year! In just 3 or 4 years the price difference in the two systems would be paid for with solar system savings and now its free money from then on with the solar system. However, with the ETS units you still just pay and pay albeit at a lower rate. Also because of the greater annual savings with solar over ETS the home equity increase with solar is greater. Clearly solar radiant is the better choice.
Similar in shape and size to hot water flat plate collectors, those that are wall mounted can use an integral fan to take air from the home, heat it in the collector, and return it into the house. The fan can be dc powered by a small photovoltaic panel eliminating the need for a wiring run and a circuit breaker at the load center. A roof mounted system of several collectors can provide air flow to attic duct runs and make a large contribution to your home's space heating. Note the photographs below.
REFURBISHING AIR COLLECTOR SYSTEMS
We also refurbish whole house systems. Note the photographs. This house, with a system from the 1970's, derives most of its space heating from the integrated air collectors.
Air collectors have the highest return on investment (ROI) of all the different types of solar systems if they are offsetting propane or electric heating.