Cloudy with a Chance of More Clouds

I have posted all my past musings so now I'm posting in real time.  We've had the system for a few days and I've been logging temperatures whenever the solar turns on.  It ran a lot the first few days, but as the water in the tank gets warmer and the system reaches an equilibrium, it turns on less frequently.  Particularly on cloudy days.(Duh.)

One nice surprise is that on sunny days, the system is kicking in way earlier than I expected.  There have been days where it turns on as early as 8:15.  The water at the bottom of the tank is 80 degrees, but the panel, in partial sun, is warmer.

On sunny days, it operates more or less continuously from 8:30 until 3:00 PM.  The highest temperature of water leaving the tank was 107, which means the collector temperature was 115.  The high that day was 76 and there were periods of clouds.  According to the Wayne's Solar sales rep, the collector will reach 140 (which is the recommended max) once the weather warms up and the sun is higher in the sky.

Today is supposed to be cloudy all day so we probably won't get much activity.

Even with the cloudy days, we haven't run out of hot water.  We've been able to use the dishwasher set to normal without it switching to pseudo energy boost.

I will be monitoring electricity consumption.  Because we have a smart meter, we can see a graph of our electric use on an hourly basis.  At this time of year, we average between 1 and 1.5 kilowatts per hour.  I'll post more when I have more data.

System is Relentless

2/21/15

Solar kicked on at around 9:15.  Temp from tank was 78, return was 86. My wife took a shower.  I took a shower.  I turned the recirculation pump on at noon so we could wash the dishes in the dishwasher.  Up to now, we have needed to use the energy boost feature of the dishwasher because the water going to it wasn’t warm enough.  We have a “smart” dishwasher so if you set it to normal and the water isn’t hot enough, it switches to a pseudo energy boost.  Instead of running for 90 minutes, it runs for 168.  Energy boost runs for 132.

After circulating hot water through the house, we turned on the dishwasher to normal.  The water coming in was hot enough so it only ran for 90 minutes.  So far, so good.  Right after we turned on the dishwasher, the solar system stopped sending water to the roof collector.  It is cloudy today so the collector isn’t hot enough.  The last reading I took before the system shut down was tank temp = 83, collector temp = 91.  I hope the sun comes out so we can replace the water the dishwasher used.  Energystar dishwashers are only supposed to use 5.8 gallons of water.  Our GE uses only 3.8 per cycle.  That means we shouldn’t lose too much heat from water replacement in the hot water tank on this cloudy day.

The solar system goes off when it is cloudy but as soon as a bit of sun peeks through, it goes on again.  Fascinating.  It is such a simple design, but is relentless at getting the sun to heat the water.

Installation Complete

2/19/15

9:25 - Air temp is 39 with 25 mph wind gusts.  The techs arrived and assessed the situation.  I think we’re all on the same page regarding what has to be done to finish the job.

11:24 - The panel is on the roof.  Temp is still in the low 40s.  They are now threading the soft copper pipe through the attic to the roof.  Lots of shouting back and forth.  No swearing though.

1:00 PM - The copper pipes have been run through the attic and through the garage attic.  They still have to solder them together and insulate the pipes on the outside of the house.  Temp sensor wire also run.  The panel should be nice and warm by now.

They are now adding the freeze valve and connecting the pipes and the sensor on the roof and connecting the pipes from the soffit to the garage.

3:15 PM - They are done.  Still need to install flashing on outside of house.  System is running.  The tech said it would take at least another sunny day for the system to get up to speed.  He turned the hot water backup a bit higher.  The sales rep will be coming with the inspector sometime and will finalize the FPL stuff.  The Pump is set to go on when the collector temp is 8 degrees warmer than the tank temp and shut off when collector temp is 140.  The LED that indicated that the pump was working turned off at around 3:45.  The collector is mostly in shade at that point.

8:44 PM - I noticed that the temp outside was down to 38, so I checked the controller.  All 3 LEDs were on, which means that the freeze protection circuitry is working.  When it gets close to freezing, the system sends warm water to the collector to keep it from freezing. As I watched it, it shut off.  So far, so good.

2/20/15

7:00 AM - 29 outside.  Three LEDs are on.  I checked the roof.  The other valve drained the water out and there is ice on the gutter.  The antifreeze protection is working.  I’m going to monitor the LEDs today to see how much heating we get from the sun.  High today is only supposed to be 50.

8:45 AM - OMG.  2 LEDs are on and it’s 36 outside.  My wife took a shower this AM and used a few gallons.  The panel is mostly in the shade but it’s warm enough to have the water be heated.  Using an instant read digital thermometer, it looks like the water leaving the tank is around 62 - 63 degrees.  I’m going to keep a log to see what it does today.

I talked to the sales rep.  The city inspector is coming today.  If flashing isn’t needed, we should be OK.  The flashing should be ready next week.  The rep is coming on Monday to finalize FPL rebate stuff.

11:15 AM

The city inspector came.  Looked at the tank.  Checked for leaks and signed off.

12:45 PM

Air temp: 49.  Water temp out of tank = 98.  Temp back to tank = 109.  Encouraging.

3:00 PM - one LED lit.  The last reading was temp out = 105, temp in =112.  It will be interesting to see what happens tomorrow.

Incomplete Installation

2/18/15

We ran out of hot water this morning.  After some googling, I found out that the tank we have will only provide 40 gallons of hot water when it is running solely on backup because it only has one heating element.  Regular hot water tanks have 2 heating elements. I sure hope once the solar system is up and running that this doesn’t happen again.

This experience led me to do some research on heat loss.  If we get cloudy days, how long will the water in the tank stay warm?

According to one site, “due to advanced insulation technology, water heated by the sun can remain hot for up to 80 hours after being exposed to sunlight.”

In the owner’s manual for the system we are getting, it states: “During normal operation, without any use of hot water, your solar storage unit should not lose more than 2 degrees per hour.”  That sounds overly conservative to me based on a formula for heat loss at Build it Solar, which is one of the most useful web sites on residential solar energy.  I think I am doing these calculations correctly, but I was an English major so there are no guarantees.

Heat Loss = (Area)(Tin - Tout)/(Rvalue), where Area is the area of the inside of the tank, Tin is the temperature in the tank, and Tout is the ambient room temperature where the tank is kept.

The Rheem tank we are getting has an R factor of 17.3. The area inside the tank is 38 sq ft.  Assuming a temperature in the tank of 120 degrees and room temperature in the garage of 60, you get the following:

Loss = 38(120-60)/17.3

Loss=131 BTU/hr

A BTU is the amount of energy needed to raise (or lower) the temperature of one pound of water by 1 degree.

1 gal of water = 8.3 lbs

80 gals of water = 664 lbs

664 BTUs are needed to raise temp in tank 1 degree.

664/131= 5.06  hrs to lose 1 degree based on the above calculation.

If you assume other factors for heat loss and take a more pessimistic scenario, we could postulate a loss of 180 btu/hr.   Then

664/180 = 3.7 hrs to lose 1 degree

Based on these calculations, it would take 3.7 to 5 hrs to lose 1 degree if temp in garage is 60.  In 15 hrs overnight, the loss should only be 3 to 4 degrees.  Of course these calculations don’t account for cold water entering the system so they would be best case.

If you use the 2 degrees per hour loss mentioned in the owner’s manual, that would be a loss of over 1300 BTU/hr, which seems high.  According to the formula, the R value of the tank would only be 1.7, which is basically uninsulated.  Like ROI, my heat loss numbers have a wide range. Experience with the system will be the true test. However, since we don't have any experience with the system, I spend a lot of time doing theoretical work that may, in the end, be totally off.

Here is some more information about how warm the solar collectors can make the water from Blue Pacific Solar, a California vendor.  

A solar collector consists of a network of pipes through which water is heated. Collectors come in various sizes, with 4 by 8 feet the most common. On a typical summer day (sunny and warm), the fluid in the collectors reaches 140°F to 180°F. On a clear winter day (sunny and cold), it can reach 120°F to 150°F. When it´s cloudy and warm, collectors can reach 70°F to 90°F, and when it´s cloudy and cold, 50°F to 60°F. As long as the temperature in the collector is greater than that of your incoming cold water (usually about 50°F), your solar hot water system is saving you energy.

I hope they can finish the installation tomorrow.

Installation Day

2/17/15 Tuesday

Installation day.  Unfortunately, it is supposed to rain this afternoon so the install may not be completed today.  Two techs arrived at around 10:15.  They turned off the water supply to the old tank and then drained the old water tank and cut off the pipes.  They figured they could at least get the tank installed today.  I verified that they were going to install the recirculation system.  In our house, we waste a lot of water waiting for it to get hot.  Wayne’s Solar also installs water recirculation systems that deliver hot water to the taps almost immediately.  There are some trade offs.  With these systems, you waste less water, but you increase your energy usage slightly. 

However, because our water will soon be provided by solar heat, the increase in energy usage is minimal.  

One guy worked on the tank and the other guy climbed up on the roof to figure out where the best placement of the panel would be.  He is drilling and installing the brackets to support the panel. I hope the rain holds off for a while.

1:00 PM - They are just about done with the tank and the rain has started.  The pipes are running up to the ceiling and the guy is working on them in the garage attic.  They said they will need an electrician to install an outlet for the pumps.

2:30 PM - The techs said they did all they could today.  We have hot water and the circulation system is installed, but without electric, we can’t test it.

3:00 PM- I called the sales rep and left  voicemail re the electricians.

3:30 PM- The electricians showed up and installed an outlet in the ceiling.  I turned on the circulation pump and tested hot water in the kitchen.  Very fast.  I turned it off.

4:00 PM- The sales rep called to verify that the electricians showed up.  He also said that the rain screwed up all their install schedule and that they couldn't finish until Thursday.

My wife and I had discussions about how to setup the water recirculation system. She wants immediate hot water any time throughout the day. The system comes with a timer that you can set to turn the recirculation on or off. I suggested we just turn on the system at certain times during the day. The more the system runs, the more energy it uses. Once the solar is up and running, we will have to figure out the best way to set the system up. We usually take showers in the morning. We have low-volume shower heads, but if you turn the shower on, it is usually warm by the time you are ready to step in. We don't really need the recirculation in the morning.

ROI and Metal Men

2/9/15

The HOA application was approved.  We are scheduled for the install on 2/17/15.

2/12/15

I occasionally get emails from FPL about energy use and conservation. Today I got one with a question posted by a consumer: How much does it cost to heat hot water?  Here is the answer:

That's a great question, and the answer may surprise you. The average FPL customer living in a single family home with two people uses 2,200 kilowatt-hours (kWh) throughout the year to heat all of their water when using a traditional electric water heater. At FPL's average residential electric rate of just under 10 cents per kWh, that’s approximately $18 each month, which is under $220 a year. Of course, it varies according to the number of people living in your home.

It's good to know how much you spend on water heating if you need to replace your water heater now, or in the future. Keep these options in mind when shopping for a new one:

• The space-saving, instantaneous water heaters, also known as tankless water heaters, can cost approximately $200 per year and save you up to 10 percent compared to a traditional electric heater.  Be aware upgrading your electrical wiring may be required.
• The new generation of heat pump water heaters can cost less than $100 a year and save you up to 60 percent compared to a traditional electric heater.
• Solar water heaters can typically save 50-85 percent depending on storage tank size and daily hot water usage.

It will be interesting to see what we save once the system is in place.

2/15/15

The solar system we are getting has an 80-gallon storage tank. Our current tank is 55 gallons. Consequently, we need to make room in the garage for the larger tank. Today, we cleaned out the garage so there would be enough room for the new tank.  This entailed disassembling a metal shelf that was held together by screws that had been painted over and were stripped.  I suppose I could have just put the 7-ft shelf out at the curb for trash pickup. But we have guys in our town who drive around on the night before trash day and take metal for recycling. They wouldn't be able to take such a large shelf so I had to use a saber saw to cut it up. Trash pickup is Tuesday. I put the pieces out on Monday at around 4:30. By 5:30, they were gone.  We are ready for the install.

Carbon Footprint and Other Matters

2/6/15

We decided to go with Wayne’s Solar.  I called their rep, asked a few more questions about how the freeze protection works, and asked for the next step.

Here is what he told me: First, I needed to register online for the $1000 rebate with FPL and get a reservation number.  In January, FPL had $1.6 million available for hot water systems.  They still have $1.58 million as of today.  FPL also provides rebates for photovoltaic systems, but those funds are gone within a day. The FPL website says they will provide the number in 3 business days.  I got my number within 4 hours.  I emailed the number to Wayne’s and they will start the ball rolling for the permits. FPL is very efficient.

For my HOA, I needed to fill out a form that included the name of the installer and business license and insurance information.  I also had to make best efforts to ensure the solar collector couldn't be seen from the street.  In our case, we had no choice due to a very tall magnolia tree next to our house.  The system had to go in the back.

2/8/15

I was still curious about ROI. After more research, I found the Florida Solar Energy Center calculator that lets you calculate your potential savings and ROI on solar based on the efficiency of your system.  The Florida Solar Energy Center website is a great resource. They have a list of certified Florida solar systems to choose from.  According to this calculator, the system we are buying will save between $170 - $234 a year on electricity and will provide 81% of the energy we need for hot water.  ROI is 15-17 years. Internal rate of return is 8.4%.  The system will reduce our carbon footprint by a over a ton of CO2 per year.

Solar systems are also eligible for a 30% federal tax credit but because I am retired and have little taxable income, these credits were no help.

According to the Nature Conservancy’s carbon footprint calculator, our family of 2 produces 45 tons of CO2 per year.  The US average for 2 people is 53 tons.  The world average is 1 ton.

Sun Position Apps

2/5/15

Before I decided which vendor to use,  I wanted to get better information on the position of the sun throughout the year.  Both reps assured me that the roof location would be adequate, but I wanted to double check.  This site has some good information on figuring out the position of the sun throughout the year, but it was all manual.  I figured there had to be an app that could do what I wanted. Google’s app store had 2 free apps, Sun Surveyor Lite and Sun Position Demo.  I wanted an app with augmented reality. Augmented reality takes advantage of your phone (or tablet’s) camera, magnetometer, and GPS.  You point the camera at the sky and the app shows you the sun's path and where it will be during the day. You can see where the sun will be on any day, at any time.

Sun Surveyor’s Lite version does not have augmented reality.  You pay $6.49 for that feature.  Sun Position Demo had augmented reality, but only for the current date and time.  I loaded both apps on my old Acer tablet.

Sun Position gave me a hint of what augmented reality could do.   I could get it to work for about 5 seconds and then a message popped up telling me I needed to recalibrate.  To recalibrate a tablet’s magnetometer you wave it around in figure 8 patterns.  With Sun Position, I was doing this way too often for it to be of any use.

Sun Surveyor Lite has a dynamic map that shows you where the sun is for any date.  I didn't have any calibration issues and decided to make a leap of faith (based on reviews) and purchase the full app with the augmented reality.  I figured it was only $6.49 and if it didn't work, that wasn't much money lost especially if it gave me good information about the utility of the $5000 system I was planning to buy.  To make things even better, the app was also on the Amazon Appstore and I still had a bit of money left over from a gift card so I could get it for free.  I downloaded Sun Surveyor and went to work.  The app worked fine. I can see where the sun will be in the sky for any date and time.

I decided to climb up on the roof and make a table of sun position for the first of each month.  The table would show when the sunlight hit the roof and when the sunlight was no longer on the roof.

The readings taken from Sun Surveyor are very encouraging.  From March until October we should get 6 to 8 hours of sun.  December is the worst with only 4 - 5 hours.  It will be interesting to see how accurate my projections are.

The Beginning

This blog details our experience with installing a solar hot water system.  Initially, I'll be posting from a log I kept. Once I catch up, I will be posting in real time

January 25, 2015
Heating water can account for 25 percent to 30 percent of the average home's energy. Reducing energy consumption also reduces your carbon footprint.   Depending on who you talk to, a solar hot water system can save you 50 to 95% of the costs to heat water. After doing some research on solar hot water heaters, I thought it might be feasible to install one on the roof of our townhouse.  Florida gets a lot of sun and it doesn't get too cold in the winter.  Freezes are rare.  The research says we needed 5 to 6 hrs of sun between 10 and 4.  If you don’t get enough sun, you need bigger collector panels.  

It is hard to pin down exactly how much you will save with a solar hot water system. There are a lot of variables including your geographic location, collector efficiency, location of the collector, how hot you set the temperature, and how much hot water you use.  Various estimates say that solar can reduce hot water costs by 50-70% in the Northeast and up to 95% in Florida.  Your mileage may vary.

Our electric water heater is in the garage.  I thought the garage roof right above the heater would be the ideal spot for a solar panel.  Wrong.  In January, this area has sunlight from 9:30 to 11:45, shade from 11:45 until 2:30, and sun again from 2:30 until 4:30. There is no sun at the best time of day.

Undeterred, I took a look at the east facing roof at the back of the house.  I observed when the sun was hitting the roof and kept a log.  The result: In January, there is full sun from 10:30 - 3:30.  Not ideal, but good enough.  I then spent a few days trying to figure out if there would be enough sun the rest of the year and it looks good.  This site has some good information on figuring out the position of the sun throughout the year.

February 4, 2015

After my preliminary research, I spoke to 2 local vendors: Wayne’s Solar and Solar Fit.  Wayne’s sales rep was able to explain clearly their direct circulation system,  He also climbed into the attic to see if it was feasible to run the pipes through the attic at the back of the house, out through the soffit, and down through the garage roof.  He said it was feasible and gave me a quote for $4795.  FPL (our local utility) offers a $1000 rebate for solar hot water so the net was $3795.  Solar-Fit’s rep gave me a nice overview of their passive system and their direct circulation system.  The passive system was less expensive, but if you had a few cloudy days in the middle of the winter, the passive system would produce water colder than the water coming into the house, which isn't very efficient.   Solar-Fit’s price was $5950. When I told the rep that I could get a comparable system for around $5000, she dropped the price to $5500 and said that was her best offer.

Both proposed systems use a 4x10 foot flat-plate collector mounted on the roof, an 80-gallon storage tank, a controller to sense the temperatures at various points in the system, and a small pump to move water from the storage tank to the collector when the temperature in the collector is warmer than the temperature in the tank.  Both systems had protection against freezing, which doesn't happen very often in this part of Florida, but it happens enough that the systems need freeze protection.

I got into a discussion with the Solar-Fit rep about solar hot water systems’ ROI.  A few months ago, FPL did an audit of our electricity use and determined that in a typical month, water heating accounted for 30% of our total electricity cost.  Cooling and heating accounted for another 30%, and appliances and lighting made up the remaining 40%.  Our bills run around $100 a month, which means that, according to FPL, our hot water costs are about $30 a month or $360 a year for a family of 2.  On a brochure the rep gave me, the costs used in their example were twice mine.  The brochure assumed an 80% savings. However, during our discussion, she assumed $40 per month and a 95% savings.  Needless to say, there are contradictory numbers when it comes to ROI.  The system will pay for itself anywhere from 7 to 15 years depending on electricity rate inflation and whose numbers you use.