While solar site evaluation tools determine the best location for the solar collectors used in a solar heating or photovoltaic installation, solar simulation software provides the software tools to help design and simulate a solar energy installation and facilitates the design making process.

Three leading companies that offer solar simulation software packages to those in the renewable energy fields are RETScreen International, Vela Solaris AG and Valentin Energy Software.

At the onset of a new renewable energy project, each one of the three companies’ software package allows the user to input information regarding the site’s location and define the energy requirements for the project. The user may then select a template or configuration from the software’s database, and in addition, may select specific commercially available products to be used. The software will generate the simulation evaluation which will include financial feasibility and potential cost savings, calculation of weather data, energy production, expected energy savings and emission reductions of the project.

RETScreen International developed their Clean Energy Project Analysis Software with the input of experts from government, industry and academia from around the world. RETscreen is applicable to various categories of renewable energy, not just solar energy. The software consists of a series of worksheets to be filled in by the user, along with a comprehensive database that is the largest and most detailed of the three software packages. The user may omit any of the worksheets that do not apply to their project. It is suitable for large commercial and governmental projects, although it may also be used with smaller residential undertakings. RETscreen software may be downloaded free from their website.

Polysun Simulation Software was developed by Vela Solaris AG, a Swiss corporation. Polysun Simulation Software is a set of four software programs specifically created for the design of heat pumps, solar thermal, photovoltaic and cooling systems. Each software program is available separately or as a complete set of four. In addition, each program is offered in three user levels, light, professional and designer. The evaluation process provides detailed reports in PDF format, including colorful graphics, and is a significant feature of this software. A Polysun demo copy may be downloaded for examination on the Vela Solaris AG website. Polysun is also available for purchase on the site.

Valentin Energy Software, based in Berlin, Germany, offers two solar energy simulation programs. Their T’SOL software was conceived for solar thermal energy systems, while their PV’SOL is for used in the design of solar photovoltaic systems. Both programs are also available in three user levels, express, professional and expert. The company’s Meteonorm software, a global climate data database, is also available separately. Customized versions of T’SOL and PV’SOL may also be developed by Valentin for individual user objectives. Valentin Energy Software may be purchased through distributors or online on the company website.

What one of these is the best solar simulation software package? Our suggestion is to download the free copy of RETscreen and try it out. If RETscreen does not meet the needs of your applications, then download the demo copy of Polysun and determine if this software is a better choice for your company. In our evaluation of the T*Sol product we found that it didn’t compete effectively with the Polysun for a number of reasons. Most notably was the lack of SRCC certified collectors and standard U.S. components. If RETscreen or Polysun does not provide the requirements that you need, perhaps your company should consider a customized version of Polysun, T’SOL or PV’SOL.

Although the main objective of each of these software packages is to facilitate in the design process, the professional looking reports generated by them will also assist solar energy companies in the marketing of their products to potential customers.

After reviewing dozens of websites, we have come up with a top ten list of our favorite solar water heating installer websites.

Each of these websites has introduced their company to the potential customer with content that is informative, clear, concise and up to date. Each one has provided a description of a typical solar water heating installation, some with illustrations. All of these websites have also included their company’s solar energy credentials and the reasons why they should be chosen as the customer’s installer. Some have incorporated photographs of their recent installations, with customer feedback. In addition each one has presented the information in a professional looking website that is easy for the user to navigate.

Since websites should be designed as marketing tools, each of these websites has been graded on the elements of aesthetics, content and navigation, and have been given a numerical score in each. Additionally each website has an SEO grade based on its grading from the website http://www.websitegrader.com. Having a great looking website is only part of the battle since you need the customers to be able to find your website as well. If you notice our top website isn’t the best looking and also doesn’t have the best content but it does have the highest visibility to the search engines and is passable in the other respects.

Our top ten list of solar water heating installer websites is as follows:

#1 ECS Solar Energy Systems, Inc located in Gainesville, Florida
http://www.ecs-solar.com/
Excellent slide show of various types of solar panels installed on homes.
Aesthetics 5, Content 8, Navigation 10, SEO Grade: 91

#2 Dovetail Solar And Wind located in Cincinnati, Ohio
http://www.dovetailsolar.com/index.htm
Extensive “frequently asked questions” area with important information.
Aesthetics 7, Content 10, Navigation 10, SEO Grade: 68

#3 Solar Assist, located in Eugene, Oregon
http://www.solarassist.net/index.html
Impressive photo gallery of recent solar heating projects
Aesthetics 9, Content 7, Navigation 10, SEO Grade: 55

#4 Greenhead Solar, located in Spokane, Washington
http://www.greenheadsolar.com/index.htm
Excellent descriptions of solar panels.
Aesthetics 5, Content 8, Navigation 10, SEO Grade: 52

#5 New England Solar Hot Water, located in Duxbury, Massachusetts
http://www.neshw.com/default.aspx
Informative explanation of solar basics
Aesthetics 8, Content 8, Navigation 10, SEO Grade: 36

#6 Enviro Plumbing, located in Santa Monica, California
http://www.enviroplumbing.com/index.html
Extensive photo gallery including pictures of workers installing panels
Aesthetics 8, Content 9, Navigation 6, SEO Grade: 34

#7 Boston Solar Living, located in Medford, Massachusetts
http://www.bostonsolarliving.com/
Great information on tax credits and rebates
Aesthetics 7, Content 10, Navigation 6, SEO Grade: 29

#8 Creative Solar USA located in Canton, Georgia
http://creativesolarusa.com/index.php
Read an open letter from the company’s founder on why he went green
Aesthetics 9, Content 10 , Navigation 10 , SEO Grade: 18

#9 Aladdin Solar, located in Excelsior, Minnesota
http://www.aladdinsolar.com/home.html
One of the few websites to give estimated solar water heating prices
Aesthetics 5, Content 7, Navigation 9, SEO Grade: 24

#10 Solar Heating Services located in Berlin, Wisconsin
http://www.solarheatingservices.com/index.php
Read interesting case study of one their latest solar projects
Aesthetics 8, Content 8, Navigation 8, SEO Grade: 12

If your solar water heating installer website is on our top ten list, congratulations!

If not, contact us with a link to you website and we will review it for our future top ten lists.

In the last blog I mentioned calibrating the customers expectations by providing them with a simulation showing what they can expect from their system. Occasionally, a customer will not realize the savings they should and they expect you to fix it. Under the right circumstances it is possible to install a solar heating system and see only a small fraction of the savings that should be delivered…

One such situation is when the customer uses a solar tank to pre-feed an indirect gas or oil fired tank that operates as the back-up to their system. When using a boiler fed tank as the back-up, it is possible to intermittently not achieve the desired temperatures in the indirect tank thus requiring the boiler to cycle on. If this is in the summer time when the boiler is only used to service hot water (and not heat the house) this means that all of the losses and waste associated with starting up and shutting the boiler down is still there. How can we eliminate (or at least minimize) the intermittent cycling of the boiler when the solar tank is already hot?

One way to reduce the boiler cycling is to tie the solar tank together with the indirect tank in such a way that any excess heat in the solar tank is shared with the back-up tank thereby reducing the demand on the boiler. This can be accomplished simply with an extra connection between the tanks, a pump, a check valve, and a differential control. When the solar heated tank exceeds the temperature in the back-up (indirect) tank the circulator turns on and causes the two tanks to be mixed together in such a way that the heated solar water moves into the back-up tank. By tying the tanks together in this manner you have accomplished several things including: reduced the firing of your boiler increased the overall efficiency of the solar collectors (by keeping the tanks at a lower overall temperature) significantly reduced the customers overall energy bill in the summer time. made the solar system more robust and resistant to overheating (glycol systems)

While this technique will not hurt in any way it’s greatest benefit will be seen during the summer when the solar system is capable of producing the extra energy. It is possible to totally eliminate the customer fuel oil usage in the summertime with this scenario.

Click here for a sample drawing

I am a strong advocate of the work that the SRCC (solar rating and certification corporation) is doing in testing and certifying solar collectors but….  There are a number of factors that can have a significant impact on the certified performance that aren’t published in their certifications and can lead to significant differences in performance as well as longevity.  Below are a few things that have a significant impact on the performance of the solar collector that currently aren’t reported:

1.  Glass

1. Hardiness – as part of the certification process the solar collector glass has to undergo repeated thermal shocks to insure that it doesn’t fail.  It is commonly understood that in order to pass this test the solar collector glass must be tempered.  The tempering process is expensive for glass manufacturers and leads to significantly higher glass prices for the collector manufacturer.
2. Transparency – when the solar collector s are tested for certification they are tested as a whole and the transparency of the glass is not measured separately.  There are two steps that can be taken to increase the thermal transmission of the glass.  The first is going with low iron glass.  This is the most common grade of glass that is used in solar collectors.  The second step that can be taken is going with an anti-reflection coating on both sides of the glass.  This coating allows low angle light to pass through the glass rather than be reflected by it.  Unscrupulous manufacturers could substitute tempered, low-iron, anti-reflection glass for their certified collector (they are only required to produce 5 samples) and then use standard float glass to supply there everyday production.  This higher performing glass would give them a significantly higher performance number from the testing but then they could cut the cost of their glass by 75% by going with standard float glass for their production.

2. Absorber

1. Thickness – as a rule the thicker the absorber sheet the greater it’s ability to carry heat (less thermal resistance).  Unfortunately, a thicker sheet costs more to produce.  Currently, the published data does not specify at what absorber thickness the collector was tested so again an unscrupulous manufacturer could substitute a thinner material once they have received their solar collector certification with higher numbers.
2. Riser quantity – the shorter distance between the fluid channels (tubes) the less heat is lost.  The number and spacing of the tubes is not published.  It is possible (and has been reported to have happened) where a manufacturer increases the spacing between there tubes to save money on the solar collector and the contractor/homeowner are none the wiser since they are sold the solar collector based on the SRCC solar collector rating.
3. tube thickness – in order to pass the rigorous 160 psi standard required for open loop collectors manufacturers can reduce the wall thickness of their copper tube once the certification has been achieved.  This will save the manufacturer money but diminish the expected life of the collectors

Random variation

1. Every process has natural variation including the production of a solar collector.  Currently, the SRCC (or there certified testing labs) tests only 1 collector (from a batch of 5) to determine what the published data for that collector and manufacturer will be.  Even their testing procedures have variation in them (this has been much discussed in the industry).  With only taking a single sample you could infer that Michael Jordan either never missed a shot or never made one (both equally wrong).  Without several data points it is easy to see how seemingly identically constructed collectors have widely difference performance numbers.

So all I have shown is that unscrupulous companies can (and will) take advantage of the system but what can we do about it?

I would recommend that we convert the current system of 1 scheduled inspection every 10 years to one where the certified manufactures pay an annual fee for the testing that will be done that year.  The samples to be tested would then be pulled randomly from the manufacturers on the list based on surprise audits.  This would serve the purpose of leveling out the costs associated with the testing process (fees would be annual based on the number of models needing testing and therefore your chance of being selected in a given year), eliminating the complaints of back-logs in solar collector testing because you would have your certification by paying your fee until your solar collector is inspected,  and freeing the solar collector performance numbers from the influence of gaming that I discussed above.

(the bottom of my tank)

Contractor leaves the job site satisfied that they have done a good job installing a solar hot water system only to be called back 2-4 weeks later to be told that the system doesn’t seem to be heating the customer’s tank.  The homeowner has been keeping a detailed log of the temperatures in the tank as well as on the roof and shows you a log that never shows the tank
sensor getting hotter than 105 degrees. They say the system has been running and they haven’t noticed anything else unusual but clearly the system isn’t working properly with the solar only getting the tank this hot.  What went wrong?

A modern differential control operates by measuring the temperature (via a temperature probe) in the bottom of the tank (T2) and the solar collector temperature at the outlet of the collector array (T1). Hot water tanks are constructed so they introduce any cold water into the bottom of the tank primarily via a dip tube that carries the cold water from the connection on
the top of the tank to the bottom of the tank. The Steca 0301U differential control (which represents greater than 50% of the control sales in the U.S.) only comes equipped with two sensors although it can take a third. In this case what the homeowner is seeing as the tank temperature is actually the temperature at the bottom of the tank (T2) where any cold water entering the tank is mixed with the solar heated water in the tank. The stratification in the tank allows the homeowner to have access to hot water (120 degrees +) at the top of the tank while only seeing “cold” water temperatures on the readout for the bottom of the tank.

solution: Supply the homeowner with a third temperature sensor that would then be mounted to the top of the tank showing what temperature the tank is actually delivering.