11 Days of Shade

Well, I'm beginning to think I need to build an Ark!! We've had weeks of rain and finally our hot water use has exceeded system generation capacity. So, I kicked on the electric backup for an hour to bring things back up to temp. Hopefully the sun comes out soon so I don't need to do that again. Back in April I turned off the backup to see how much hot water the system could generate. It's made 100% of our hot water (plus some) all summer long, so I left it off. Based on the graphs I've been keeping, I believe that we'll need the backup turned on full time in early November when the days get shorter and sun low in the sky. BTW, that hour or so ate up 7kWh to get things back up to temp. Glad we're not running that every day!

Commissioning Day and Rebate

Been a while since I posted, but we finally got our final inspection done on June 10 and commissioning/completion paperwork submitted. It's now July 19th and we got our MD Solar Grant check in the mail!! Yay! Next phase is to figure out how to register the system for SREC generation. I believe the system needs to be SRCC certified to qualify. SES has been working on that testing for their system design for a while now and anticipates publication/acceptance this year. This means we'll be able to qualify for the sale of SRECs in MD, further reducing our breakeven timeline and allowing the state power generation entities to get credit for our reduced grid usage.

One Month of Solar

Usually our electric meter gets read on the 14th, which would be today. Since last month, I've been keeping track of daily electric use by reading our meter on the side of the house. It's interesting how aware you become of electric use when you do that.....an extra load of laundry, dishes, etc.... it all adds up. What I'm trying to see is if the effects of the solar hot water system can be seen in the bill... I think they can, and it's more than I expected. Of course there are other factors like weather that play in..but averages speak volumes. I have plotted in excel, every electric bill for this house over the last 10 years (January 2000). For the 28 days spanning 14 February to 14 March the bill has averaged 1537kWh with a low of 1247kWh last year and the runner up of 1290kWh in 2000 when we 1st moved in. This month, the bill was only 1035kWh! The lowest bill EVER for the period since we moved in. That is roughly 17% down from the low and 32.6% down from average.

The days are still pretty short and the sun pretty low in the sky...the system is not supplying all our hot water under these conditions and will only get better throughout the spring and summer. I'm looking forward to seeing if the trend continues.

As for calibration, the control unit is clearly under calculating the kWh generated...by how much I'm not sure. I believe this is because I have the incorrect flow rate programmed into it. As I take more data I'll see if I can predict and back into the correct calibraction factor...for now, it is good enough to tell a good day from a bad day and act as a diagnostic.

System Cost

So, inquiring minds want to know...what did the system cost?

There are a number of ways of looking at that.....so I will just give the simple answer:

$9386.00 installed (out of packet expense)
Federal 30% Tax credit: $2815.80 (received during next tax cycle)
Maryland Grant 20% capped at $1500.00 (received later this year)
Needed a new water heater anyway and was looking at the GeoSpring ($1482.94)

Effective cost $3587.26
7 year payback

The complicated answer includes inflation and electric rate increase. (5.5 year payback)
The deceptive answer also includes your tax rate and treats the expense as an investment (I don't buy into this one <5yrs).

Usage 2-20-2011

It's been a couple weeks and you can see from the graphs, even in February, it makes hot water. I get the numbers from the controller screen, which I log each day. A project for later on will be to instrument the controller...it has a RS485 bus that can be hooked to my computer. The anomale on the 17th was due to a mistake during install where the collector feeds got swapped so the cold water was feeding from the top.....yes, it obviously makes a difference. This was due to a blind run of tubing in the attic and they got mixed up. It was cloudy that day and not obvious when we turned the system on.....but easy to detect once the sun came out.

From Solar Water Heater Data

Slideshow

Here are the install pictures:

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Get your own

Mixing Valve

No one really wants anything to do with 160F+ hot water. So to extend the volume of water available and to ensure only a safe temperature reaches the fixtures a Honeywell AM-1 1043 tempering / mixing valve was installed. This valve sits on the outlet of the hot water heater and mixes cold water into the stream to maintain a preset temperature. The output temperature is adjustable from 70F to 145F. It is set at around 118F right now.

From My Solar Hot Water System

Controller

The system is governed by a RESOL differental temperature controller designed for solar applications. My system uses the DeltaSol AL controller.

From My Solar Hot Water System

The controller measures the temperature of the panel on the roof and compares it to the temperature at the bottom of the tank. If the roof is 12F hotter than the tank, the pump will circulate warm water from the roof to the tank. When the difference shrinks to 5F, the pump stops. This cycle continues until the top of the tank reaches 160F, after which the system enters a stagnation mode where no pumping occurs.

The system will exit stagnation if tank temp drops below 156F, or if the roof temperature exceeds 240F. The latter is to protect the system from boiling or the glycol from getting heat damage. If the roof is too hot, the system will periodically pump short periods to try and keep it cool...if the storage tank gets to 190F the whole system shuts down. The system is sized so that the tank can hold all the BTUs generated by the collector in a day if the starting temp of the tank is 160F. So, it should never shut down unless there is a problem.

At night, if the tank is still above 160F, the system will run to let the excess heat radiate to the night sky until the tank is at 160F. This ensures there is enough capacity in the system to hold the next days heat.

The Pump and Controller

Attached to the front of the tank is a Grundfos UPS 15-58 pump. This is a pretty standard cast iron pump for hydronic heating applications that has enough 'head' to ensure good circulation of the fluid at high temperature. It is a three speed pump (selectable) with integrated check valve. On the high setting it achieves about 2gpm flow rate in this setup. It can be isolated from the system using two big ball flange valves for maintenance. The system fill ports and expansion tank can also be seen in this picture.

From My Solar Hot Water System

The Tank

Down in the basement is where the hot water tank resides. Originally, I was not looking for a solar system, but for a stone lined hot water heater to replace my 11 year old unit. I wanted a stone lined tank because they basically last forever. As it turned out, Solar Energy Services, Inc. is Vaughn's mid-Atlantic dealer. Vaughn Corporation is located in Salisbury, Massachusetts and makes hydrastone lined water heaters. For my application, we chose a Solar SEPCO 120gal tank with electric backup and single 20sf heat exchanger. This tank is more than enough to meet my family's needs for hot water without the solar input to it. With the solar panels connected, it should make about 70% of the hot water I use from the sun, greatly reducing my electrical use. Here is a picture of the installed system in my basement...the large white tank is the Vaughn solar tank. The big blue tank is my well pump pressure tank and not related to the solar install.

From My Solar Hot Water System

The System

Before too much time passes by I should take the time to describe the system. It was designed and installed by Solar Energy Services, Inc. They have a lot of experience with solar systems in the Maryland area and were great to work with. They were on site just a couple weeks after contracting with them and the crew took two days to complete the install. On the 1st day they swapped out my old water heater for the new one with a heat exchanger and installed the panels on the roof. The second day they connected the closed part of the system between the exchanger and the panels and activated the system. (more on that later). If I had to do it again, or for anyone else that is interested, I would highly recommend Solar Energy Services, Inc.

Now for the system. At the heart of the system are two solar collector panels manufactured by Alternate Energy Technologies, LLC. AET is a Florida based company that has been at the forefront of flat panel technology since 1975. Inside, they use Thermafin copper welded collector fins. For my installation we used a pair of AE-32 panels. These are 4x8 panels providing ~60 square feet of absorber area. The SRCC rating for these panels is here: http://securedb.fsec.ucf.edu/srcc/coll_detail?srcc_id=2002001E .

Here is a neat video describing the 'Thermafin' manufacturing process:

The Sun Came Out

Whoohoo! The sun came out today and the collector ramped up to 110F. It was nice to see the pump pumping and the tank slowly warm up. Controller claimed only a couple KWH generated today, but it was below 32 this morning and only reached 40 or so. Pump seems to be short cycling in these conditions...maybe pumping to fast? I might try the medium speed setting to see if the system behaves differently. It's a Grundfos three speed with an external speed switch, easy to switch.

Day One

Well, here we are, starting down the path of installing a solar hot water system. After a lot of reserach on the web and determining that it would really break even in a few years we decided the time was right. The Federal 30% credit and the Maryland State 20% grant makes systems like these financially viable. I plan on posting info on our system search, system design, photos of the install, and system data as I get it. As of now, the system is only half installed.