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This page describes the solar thermal work done on my house to heat water. I mention the choices I made and evaluate performance. |
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This page describes the solar thermal work done on my house to heat water. I mention the choices I made and evaluate performance. |
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After getting solar photovoltaic panels installed, I considered further reducing my carbon footprint by harnessing the power of the sun for heating our water.
In 2011, our old 60 gallon electric water heater started leaking very slowly. At first I thought it was just condensation. But it got worse and worse over time. The yellow energy guide sticker says it uses 4,959 kilowatt hours (kWh) per year. As of May 2013, we pay $0.1287 per kwh using Castlebridge Energy Group as our provider (this includes charges, fees, and taxes). This means that we have been paying about 0.1287 x 4,959 = ~$638 per year in electric bills for our old water heater. The exact number is probably smaller since there are just two of us in the house but for lack of better data, I'm going with the energy guide sticker estimate. We don't know exactly when it was installed but the energy guide sticker quotes energy prices based on 1994. Yes, 1994! It has lasted at least 19 years! Amazing. Hopefully the next one lasts at least as long.  |
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There are many ways to heat water. I considered several options in 2013.
Conventional electric
Solar Photovoltaic with Conventional Electric
On-demand (tankless)
Electric heat pump
Solar thermal
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Having gathered what I deemed all the important information, I was ready to make a decision.
Summary
Longevity
Noise
Protecting the Environment
Payback
Final answer
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You don't put a new solar thermal system on a 20+ year old roof. You get a new roof. When doing so, you have the roofer remove the old roof, inspect it, and make any necessary repairs so there will be no issues in the near future that would require both solar panel and roof removal to fix.
I've had work done by RoofPro in the past. They were prompt, seemed knowledgeable, and got the job done for a reasonable price. Their BBB rating is A+. Two years ago, Adriano Candido reroofed my garage. See Selecting companies and Roof work for more information. He did great work but it's often hard to get him to reply or give me an estimate for a start date. I guess it's because he's good. But I'm too impatient for that so I decided to go with RoofPro. Bradley H. of RoofPro came out. We spoke for awhile. I ordered the CertainTeed Extra Tough (XT) 25 timerbline asphalt shingles. These should last 25 years. It is the same shingle type on my garage. I also got the Leaf Solutions gutter guard which have a lifetime guarantee. I've been fortunate in that I climb up on the roof several times a year to clean out the gutters and haven't had any near falls but I figure my luck will run out. It is a two story drop onto the driveway. I'm not getting any younger so I'd rather not take risks I don't have to. I got this installed both on the roof and the garage. I asked about getting a vent cap but Bradley said I was better off with my attic fan since I have a hip roof which doesn't have much roof line. He said they would install an ice/water shield which will go over the drip edge. During his inspection, he said there wasn't one under the old roof. On May 15, 2013, they finished installing my roof and the gutter guard. Over the next few weeks, I observed the gutter guard during heavy rains. It worked just fine. There were some spots that didn't quite lie flat so Steven came back on July 23, 2013. I don't expect thing to be perfect the first time around but I do expect a good company to follow up to their customer's requests and make things right. Unfortunately, Steven couldn't really see what I was talking about because it was early in the day and the sun wasn't hitting the roof at the right angle. So I sent him a picture taken in the afternoon. 
He replied a couple days later letting me know that he was speaking to his manager to decide how they could resolve this and would get back to me. On September 9, 2013, Steven redid the roof. I asked him what caused the initial job to be bumpy and he said they had a bad roll of felt paper that didn't want to lay as flat as it should. Things looked much better once they were done. Since the new roof and inspection is needed for both the solar thermal panels and the solar photovoltaic panels I purchased in 2013, it qualifies for the 30% federal tax credit. But I'm only going to apply this credit to the cost of the roof, not the gutter guard. The roof costs $5,400 while the gutter guard costs $2,750. So after I filed my taxes, I got back 0.3 * $5,400 = $1,620. |
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On June 20 and 21, 2013, Bryce and another guy came out to do the installation of the solar thermal water heater. This is before Steven redid the roof shingles because the part he worked on was on a different side of the house. On the 20th, Bryce and his team got the collector (solar panel) mounted on the roof, removed the old water heater, and set up the new one, which was much larger than I expected.
Before, I used to be able to squeeze between the water heater and the wall. Now, even an anorexic can't do that. Then, the next day they came back to hook things up. I was pleased with their work. They did everything that Rich said they would do. 
My system was operational on June 21, 2013. |
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Near the bottom of the water heater is a round, black display with the words "Grundfos Alpha 15-55F/LC" on it. The reading switches between wattage consumed and gallons per minute. It isn't always displaying. I think it just does when propylene glycol is being pumped between the collectors and the water heater. The wattage indicates how much electricity is being used by the water heater to actually heat the water in the electric mode. This is separate from the amount of electricity used to circulate the propylene glycol. In fact, they are controlled by different circuit breakers. Circulation is controlled by breaker eight in my house while the water heating element is controlled by breaker 16 (prior to December 6, 2013) or breaker 20 (as of December 6, 2013). I can turn off the breaker for the water heater and just let things heat in solar mode on a sunny day. Bryce suggests doing that just to see how long we can get by on solar heating without needing the electrical heating element. As long as the sun is out and the propylene glycol can circulate, it will heat the water. Ideal circulation rate is two gallons per minute with a wattage reading of 17.
There is also a "Winters" pressure gauge near the bottom. It should read about 28 pounds per square inch. This relates to the pressure of the propylene glycol. Also near the bottom is a small white metal tank with the word "Extrol" on it. This is the expansion tank. Near the top is the white Resol DeltaSol AL display which reports several things. Your panels are rated for sustained stagnation, so if your power is out for a period of time, no damage is done to your system. It's a bit hard on the glycol, but as long as you remember to have the system serviced (glycol changed) every 3-5 years, all is well. Roger has been in the business for 35 years so I'm assuming he knows what he's talking about. S3 reading on June 21: 123.0 If we go on vacation, we can turn off the breaker (16) to the water heater heating element. The pump is the thing that keeps things from overheating so breaker eight should never be off. To adjust the temperature of the water, I need to turn the knob above the tank. This ia a grey knob with the words "Honeywell AM-1 Series" written on it. Before turning, I need to loosen the screw in the center of the knob. Turning clockwise (blue arrow) will increase the cold water coming into the tank to lower the temperature of the water while turning counterclockwise (red arrow) will reduce the cold water coming into the tank to increase the temperature. Bryce advised me to put a small container under the propylene glycol relief value which is near the bottom, just below the round, black display. He said that there are a few cases (very few) where propylene glycol leaks out. If it does, call them. The system has a seven year warranty but they typically last 20 years. The long vertical copper pipe can be used to drain the tank. This could be good to get out residue that settles at the bottom but shouldn't need to be done often. I should definitely get the propylene glycol changed at least every five years. This costs $15 per gallon plus $100 for the service call. Our system uses four gallons so that means $160. It becomes corrosive as it ages or is exposed to high heat. Glycols produce organic acids as they degrade, especially when heated. If left in solution, these acids will lower the fluid's pH. With no corrosion inhibitors to buffer these acids and protect the metals in the system, the corrosion rate of a plain ethylene or propylene glycol solution can be greater than plain water - a highly corrosive fluid in its own right. - from "Hydratech - Protect your cooling and heating systems against corrosion" (a broken link as of 2017) The outside of the tank is plastic while the part the inside is steel with a lining of hydrastone on the inside. The propylene glycol mixture gets from the collector to the water heater via an insulated pipe in the attic. 
From the attic, this pipe connects to the basement through a space that goes between the wall in my office and our chimney. There is no way to tell it is even there. |
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On July 19, 2013, my plumbing inspection was performed by John Hidey while my building inspection was performed by Ken Brown. All good to go.
On August 5, I noticed a sound that occasionally came from the water heater. I hadn't heard it until then because I was sleeping in the downstairs bedroom when my in-laws visited. It sounded like a mix between clicking and water dripping on plastic. But there was nothing leaking that I could see. It occurred about once every two minutes. It wasn't loud, but considering everything else was pretty quiet at that time of night, it was noticeable and made it difficult to sleep. I did not hear that sound in the morning. Roger and Bryce think it is the expansion tank and that it can be relieved by running the hot water for awhile. I notice the sound more on sunny days. Eventually, it ceased occurring. On October 6, 2013, our house was recognized as one of several on the "4th Annual Maryland Tour of Solar and Green Homes." This means it was listed in a booklet and open to the public for the afternoon. What makes our home green? We use solar photovoltaic panels, a solar thermal water heater, a geothermal heat pump, rain barrels, extra insulation in the attic, composting, and a pellet stove which burns fuel made from sawdust and other wood waste. All this in a home built in 1952! The event was a success. I had about 25 attendees, mostly neighbors, co-workers, and kayakers, and there was never any down time. It lasted from 1100 to 1800. I've lived in Maryland since 1995 and the 2013-2014 winter was the coldest I've ever experienced. How effective was our solar water heater during this time? Much of that depends on if there was snow covering the collector. On February 27, 2014, it was cold and sunny. There was no snow on the collector. The outside temperature was 35 degrees but the temperature in the collector was 125 degrees! Inside the tank, it was 122 degrees. So indeed, even on cold days, as long as it is sunny, our solar thermal water heater can operate in solar mode, though I have no doubt it also gets some help from the electric heating unit. Just how much help it gets, I don't know. I would prefer that the electric heating element receive its power from an electric wall socket rather than be hardwired. Then I could use a Kill-A-Watt electric usage monitor to measure its energy consumption. On May 11, 2014, I turned off breaker 16 again. In a normal year, I think we could have turned it off a couple weeks prior but it has been a pretty wet spring so far. On October 3, 2014, I turned it back on again. So during the time in between, our water was heated entirely through solar energy. The following year, I tried this again but on the day after spring (March 21, 2015). That was too soon. I tried again on April 11, 2015. This was a good time for the changeover. However, we had a very dark early June. After about five days of heavy cloud cover and/or rain, I had to turn breaker 16 back on, June 5, 2015...at least until the sun came out again. In August 2015, I stopped getting hot water. This was very unusual since normally, I don't have to turn on the electric breaker to the heating element until October. Checking the system on a moderately sunny day, the temperature in the collector (COL) read 220 while the temperature at the top of the tank (S3) read 89. I reached out to Erin at Solar Energy Services on August 9, 2015 to inform them of the problem. Peter came out on August 20. He found that the system was low on glycol. The pressure gauge should have been at 35 pounds per square inch (give or take 10, depending on the time of the year) but it was not. Below 25 is a problem. Expect lower pressures in the winter and higher in the summer. He checked for a glycol leak but didn't find one. He tested the remaining glycol for acidity but found that it was fine. He refilled the glycol and things were fine after that. The system holds four gallons of glycol. On August 24, 2015, I noticed a small puddle of glycol under the gray expansion tank for the circulator. Glycol was dripping out the bottom. I checked the sides and they were dry so I'm pretty sure it was only coming out the bottom. The pressure read slightly lower than previously. I turned on the electric heating element for the water heater and reached out to Erin again. On September 4, 2015, two guys came out to fix the leak. They increased the pressure of the glycol and found a pinhole leak on the lower side of the expansion tank. They replaced it and recharged the glycol to 34 psi. Around October 1, 2015, I turned on the breaker for the electric heating element on the water heater. Normally, I would have waited until longer but we were getting a lot of clouds and rain from hurricane Joaquin. On February 14, 2016, the sun was shining brightly and the air temperature was around 20 degrees. But the temperature in the panel (collector) was 110 degrees! On April 14, 2016, I turned off the breaker for the electric heating element on the water heater. On September 26, 2016, I turned on the breaker for the electric heating element on the water heater. We had a very rainy week then. On January 22, 2017, the glycol reading was 22 psi, which is about what it read when I reported the leak in August 2015. I expect that the pressure reading might be a little lower in the winter but at the time, the air temperature was 50 degrees and the temperature in the collector is 60 degrees so conditions were rather mild. I reached out to Solar Energy Services. After a couple of days, with no reply, I sent a follow-up email saying "PLEASE REPLY." Then Erin M. replied and scheduled a technician to come out. On January 27, 2017, Bruce came out. The glycol reading was still at 22 psi, but he said with a house with just one story, that's sufficient to run the glycol. As long as the psi is at least 20, the glycol should continue pumping. He talked with his boss, who indicated it doesn't seem abnormal to have lost that much psi over the 15 months since it was last refilled to 35 psi. You can hear the glycol running when the temperature in the panels is high enough to turn it on (12 degrees higher than the temperature at the top of the tank) by listening to the gurgling in the one horizontal pipe near the bottom of the tank while turning off the one yellow value to the left of it. Bruce checked on the roof and in the attic, and it all seems normal with no leaks. He refilled it to 35 psi. He noted this on the side of the tank, along with a note that the glycol was changed out 15 months ago. In a normal situation, the glycol won't need to get changed out for five years, but if there are issues, it should get changed out in three years. He seemed to think our situation is normal. I tried to drain the sediment in the tank but couldn't figure out how to do so. There is a spigot on the side of the tank near the bottom but that only drains incoming cold water, not what is in the tank. Bruce said that this tank does not need to be drained of sediment due to its construction. I find that hard to believe. On April 9, 2017, I turned off the breaker for the electric heating element on the water heater. I had to turn it back on after several days of no sun but once the sun came out, I turned it off again. The spring of 2017 is starting out rather dark. I turned on the breaker again on October 14, 2017. On February 11, 2018, my shower was getting cold. After I got out, I checked out our water heater. It reported the following at 2055: S3: 102.5 I was told 125 is ideal. The device that pumps glycol to the panel (solar collector) was showing 14 watts and 2 GPM. I had never seen this on at night. It wouldn't make sense since the pump should only run when the temperature in the panel is hotter than the temperature in the water heater. I also noted that some dark liquid had dripped below the pump monitor though I don't know when. This isn't too unusual. The pressure gauge showed 30 psi which is good. The following day, Norma contacted Solar Energy Services to come out and take a look at things. Someone wasn't available to come out until February 21. On that day, Chris inspected the water heater and replaced the glycol. The dark liquid I observed leaking was dirty glycol. When it gets old, it doesn't transfer heat as well. He inspected the heating element and the panel. All good. He adjusted the settings to give us more hot water. He could not explain why the glycol would be pumping to the panel at night. I had him put this in his notes. He worked for about 2.5 hours. We were billed $440.50 ($150 per hour for labor). This seems like quite a bit considering I'm not convinced they found the problem. I had only had the system for five years. I might see if another company can change the glycol for cheaper next time. I'm not totally certain but I think the problem with the pump running at night might be connected to the fact that we have Peak Rewards. This allows BGE to turn off our water heater during the winter to reduce the demand for electricity. Allowing them to do this saves us $6.25 per month that we are under Peak Rewards. But by turning off the heating element, it might trick the system into using the pump instead. Peak Rewards was eventually discontinued in April 2021. I turned off the breaker for the heating element on April 19, 2018. As of January 1, 2024, our solar water heater has been working fine. I have not have the glycol replaced again. I expect I will once I find the system doesn't work so well between late spring and early autumn when the electric heating element (breaker 16) is turned off. |
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The system became operational around noon on June 21, 2013. Naturally, a lot of energy (either solar or electric) was needed to get the cold water in the tank hot. But after that, it went into more of a maintenance mode. Of course it takes a lot less energy to keep something hot that is already hot than to heat up something cold. So for the first day and a half, I really don't care how much energy the system used or how much it saved me.
What I do care about is how much energy was used starting at the end of day two. On the evening of June 22, 2013, the Resol DeltaSol AL display let me know 39 kWh of electricity was offset since the system was activated. This means that if an electric water heater was used, I would have paid for 39 kWh but instead, this electricity wasn't needed since solar provided the energy. On June 24, 2013, I shut off breaker 16 which powers the electric heating element in the water heater. Thus, the only heat being generated is a result of solar energy. Due to some mix-ups in turning breakers on and off, I ended up not being certain of exactly when I was not able to obtain sufficient hot water without using the electric heating element but I estimate it was sometime around early October. On August 5, 2013, I started measuring the energy usage of the pump that circulates the propylene glycol mixture from the collector to the water heater. Since I was not using the electric heating element at that time, all the electric energy used for creating hot water was monitored by a Kill-A-Watt electric usage monitor. See my August 23, 2013 entry under Electricity Offset. Electricity offset
Actual payback
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Recall that the return on investment for the solar thermal water heating system was largely based on the future value of SRECs, which was unknown at the time of purchase. In hindsight, 7.5 years later, SRECs still have considerable value. Over 10 years, the solar thermal water heating system will have yielded 2.256 * 10 = 22.56 SRECs, worth approximately $185.10 * 10 = $1,850.
This means the net cost for the Solar Energy Services AET/Vaughn solar thermal water heater after 10 years is $7,900 - $2,370 - $500 - (10 * $185.10) = $3,179. With this updated information, I now revise what I wrote in Payback. Recall that after five years, I paid $440.50 to have the glycol replaced. This cost averages out to $88.10 per year: |
