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).
Wednesday, February 23, 2011
Sunday, February 20, 2011
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.
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| From Solar Water Heater Data |
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.
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| 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.
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| 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.
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| 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.
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| From My Solar Hot Water System |
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