Video of Ann Arbor Michigan Solar Roof Installation
Posted by Jon on March 2nd, 2011 filed in Videos From Youtube
I was finally able to get the time lapse video posted to Youtube.com
This was the full roof installation. Before this was done the guys from Select Solar and Generator hung the inverter and set the wiring from the panels to the inverter and from the inverter to the DTE generation meter, and from the generation meter to the breaker panel.
In case you didn’t see it before this is 42 panels, each with a 230 Watt capacity for a total DC power rating of 9,660 Watts.
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A2Energy.org Site Has Energy Saving Information
Posted by admin on May 10th, 2012 filed in General
The Clean Air Coalition teamed up with the City of Ann Arbor to create an information site for energy saving ideas and information for Ann Arbor residents. http://a2energy.org is the site and it has quite a bit of information.
I hope it doesn’t get dragged into the political muck. After spending a few minutes there everything I saw seemed objective and rational.
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We Hit Our Generation Target after Only 351 Days!
Posted by admin on December 28th, 2011 filed in General
Well we did it! We generated as much electricity in 2011 as we consumed in 2010, with five days to spare!
We need to make long term comparisons like this because actual generation depends so much on weather, but a one year mark makes sense to me.
Now e also plan on consuming more electricity in 2012 than in 2011 because we will have a full year with our mini-split heat pumps. But don’t worry. For every BTU from the heat pumps we will use a BTU less of natural gas or wood.
The mini-split systems also provide the benefit of mini-zones. That is, temperature control by room.
For example right now my office is being heated up to be in the seventies. Yesterday morning my wife was cooling our family room down to the sixties. Most of the home isn’t using any energy now and stays in the mid sixties to mid seventies range. In a conventional home heating/cooling system all rooms would typically end up being heated or cooled to the same point.
This video shows a similar system in use in another solar home:
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Solar Scandals, Corruption, and The Green Con
Posted by Jon on October 19th, 2011 filed in General
I just read an article about Michigan’s support of solar companies who have failed. Unfortunate, but not nearly as bad as the Scandals and corruption at the Federal level.
I kind of feel like I know a bit about practical solar installations and I can tell you that I knew last year that Solyndra’s business plan didn’t make sense. Their unique technology never “penciled out”. Never.
I also considered Evergreen and decided to us other panels because the company looked like it was going down hill.
I am not happy that our tax dollars were wasted on those efforts when anyone with an ounce of business sense would not have invested in those companies. It embarrasses me to be associated with this kind of corruption, back-room dealings and scandals.
Here is a recent article about the State of Michigan’s soar flops: http://www.michigancapitolconfidential.com/15889
The companies that were involved in my solar roof are long-term solar manufacturers, making steady improvements in their designs and production. That is really the way it should be.
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Alternative Energy in Southeast Michigan Article in AA Journal
Posted by Jon on March 29th, 2011 filed in General
My mother pointed out this article in the Ann Arbor Journal:
http://heritage.com/articles/2011/03/16/news/moving_forward/doc4d7558da1892a483649282.txt
It discussed David Strenski and the development of the Ypsilanti solar projects. Their website is here: http://solar.ypsi.com/
It sounds like Mr. Strenski has been involved from the beginning and and is very involved in a lot of the Ypsilanti solar projects. No doubt a good person to know.
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Fifth Choice, How Big To Size The Solar System
Posted by Jon on March 1st, 2011 filed in General
Sizing the system will depend on your current usage, the amount of roof space you have, your budget, and how much time you want to spend optimizing the system.
Using the basic numbers from the PVWatts site and from our bill it looked like we would be good asking DTE to approve a 7,000 Watt DC rated installation. A couple of installers confirmed that range should be approved so I knew my baseline at that point.
However, I know the marginal cost of installing a system goes down as the system gets larger. This is a critical point to understand. A number of the quotes I received were derived and justified based on a certain cost per watt. But the actual cost per watt gets lower as the size of the system gets larger. (Think cheaper by the dozen.)
My desire was to utilize the maximum amount of the DTE renewable energy credit which paid $2.40 per DC watt, and also size my system so I wouldn’t need to come back later to add additional capacity. (Which would probably cost a lot more money per watt.)
I also knew that we currently use wood as our primary heat source and that as we get older we might want to use it less. And, we are planning on installing some super efficient mini-split heat pump systems to supply heat and air conditioning in the future.
I did some basic heat energy calculations and determined that our electric energy use could easily increase by 25 to 30% over the coming years as we used less wood and more electricity for heating.
So, I targeted a larger system for my proposal to DTE. I spoke to a couple installers who agreed it made sense to plan this way. The target number I ended up with was a 10,000 watt DC system.
I also have a 3,000 square foot roof so I know that about 1,500 square feet is facing South West. That gave me 1,500 square feet to play with which would turn out to be plenty to install our system.
Note that there are at least two different ways to describe the power capability of a solar system:
1. The maximum possible output of the solar panels themselves. (This is referred to as the DC Watts output or the “Nameplate Watts.”)
2. The maximum possible output of the system. (This is referred to as the AC Watts output.)
So I targeted a 10,000 DC Watt system, knowing that it would rarely if ever be possible to actually get a full 10,000 watts of output from that set of panels because it would take perfect conditions as far as the sun’s location in the sky, the temperature on the roof, shading, and the weather.
I ended up with what Detroit Edison called a “9.66 DC/ 8 AC kW Solar System” on my roof. And, today as I write this there have been a couple minutes where conditions have been good enough to hit the 8 kW level of system output, so I can confirm it is actually working as designed.
Since DTE is currently paying $2.40 per DC watt after installation, this means that when the installation was complete and had met all the approvals, DTE would write me a check for $23,184 to help pay for the system. (And after a few nervous weeks I actually did receive it!)
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Fourth choice: Lowest Solar Panel Operating Temperature
Posted by Jon on February 8th, 2011 filed in General
The fourth choice will actually determine what type of solar panel plans will actually work. As it turns out, the popular solar panels are polycrystalline. And this cell technology has a negative output voltage vs. temperature coefficient. Another way to state that is that the voltage gets higher as the temperature gets lower.
Believe it or not this is a very critical design parameter. Systems that are designed for use in Florida can self destruct when they are installed in Michigan because the Florida design would probably assume the lowest operating temperature of around 25 degrees. Here in Michigan sometimes get sunny days with below zero temperatures. This difference can raise the output voltage enough that the rest of the system is at risk of failing.
So in our case we needed to do some research to find the historic low temperatures and make some assumptions about low temperatures when sunlight would be hitting the panels. The record low temperature going back eighteen years waas -22 degrees F. And that would have been at night when the solar panels wouldn’t be generating any voltage. We chose to design our system based on a lowest possible temperature of -14 degrees F.
This design choice is particularly interesting when you realize that two of the system quotes we received were actually improperly designed for Michigan installations. I spoke to another engineer-homeowner who installed solar panels in 2010 and he also received proposals that had this same design error. So, be careful with this!
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Second Choice Grid Tie Solar Panels or Battery Charging Solar Panels
Posted by Jon on February 8th, 2011 filed in General
So we have chosen to do solar electric on our Ann Arbor home, the next big questions is which type of topology. That is: Solar panels connected to inverter connected to the utility grid or solar panels connected to a charge controller connected to batteries, connected to an inverter connected to the home electric system.
In the grid tie arrangement the utility company acts as the power storage eliminating theu don’t have need for batteries.
The downside to a grid tied arrangement is that if the utility company power actually goes out, the solar panel/inverter system shuts down. So you don’t have any kind of back-up power in a standard grid tie system. (The practical solution for this concern is to just have a back-up generator. )
The upside to a grid tied system is that you don’t have batteries to pay for or maintain. Having enough batteries to power a household for a couple days in case of cloudy weather can cost several thousand dollars. And those same batteries may need replacement in four to six years.
In fact, the cost of batteries and battery maintenance alone makes battery charging systems really only suitable for locations without grid power available.
Also, utility rebates and tax incentives are only available with grid-tie systems.
So the second choice ends up being fairly easy. A grid tie system it will be!
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Third Choice. String Tie or Microinverter
Posted by Jon on February 8th, 2011 filed in General
So we’ve decided to install a grid tied system to take advantage of the utility and government subsidies and not have to deal with batteries.
The next choice is microinverters or strings.
String systems have a number of solar panels connected in series much like a flashlight might have two or three 1.5V batteries connected in series. In series connections the voltages add. So a flashlight with 3 1.5V batteries has a total of 4.5V to the bulb. In a solar installation a set of 13 solar panels might be connected in series. If they each put out about 30 Volts then the sum would be 390V. Many solar panels have about 200W of power output under full sun so that might mean that the panels produce a current of about 7 Amps. (Assuming 210 Watt panels.)
If you need more power than 390 V at 7 Amps, (2,730 Watts), then you need to add additional strings. You can’t practically mix string voltages so this makes it a little difficult to design and build. In our example you have a choice of a 2,730 Watt system or a 5,460 Watt system or a 8,190 Watt system. Trust me, it starts to get a little complicated.
Also with a string system the whole string can be negatively impacted if one panel has a problem. For example if a shadow from a tree is over one panel that will limit the output from the whole string, even if the other panels aren’t shaded.
The alternative that has just been practical for the last few years is having an inverter connected directly to each panel. One inverter per panel. The output of the inverter is the 240VAC that can feed back into your breaker panel. These inverters that mount on the back of the solar panels are called microinverters. The most popular one is from Enphase.
Up to 15 of these can be grouped together on one circuit, and there is basically no limit to how many groups you can have.
This is a very flexible alternative because with microinverters you can start with just one panel and one inverter and build from there.
Again since I have a background in power supply design I found these systems fascinating. There were just two problems:
1. I am concerned about the long term reliability of that many power converters in that extreme environment. Roof temperatures in the summer can get quite high and obviously during the winters they can get quite low. And that temperature swing will be happening every 24 hours for the next twenty/thirty/forty years. (Solar panels can easily last 40 years, however their output will drop some over time.)
2. I wanted the option of doing something else with the power from the panels at some point in the future. (This is a geeky engineer thing most people probably won’t care about.)
The microinverters do cost a bit more on a per Watt basis, but the installation is easier so they end up fairly close in total price.
In the end we decided on a string tie system with three strings of 14 panels.
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The First Choice. Hot Water or Electricity?
Posted by Jon on January 26th, 2011 filed in General
Today’s post is about selecting between a hot water solar collector and a photoelectric solar collector, and the decision points involved in doing it.
When deciding on what sort of solar collector to deploy we considered cost, efficiency, return on investment, convenience once the installation was complete, and impact on the appearance of our home.
First we considered the cost. We could install a basic solar water heating system for a couple of thousand dollars by doing the work ourselves. A solar electric power panel system would cost in the range of $2,000 for a small system self installed all the way up to $60,000 for a professionally installed system. But we found that in order to take advantage of the tax and utility company bonuses we would need to have installed by a licensed contractor.
Efficiency relates to how well the system turns the sun’s heat energy into usable energy for our home. In this area the solar water heater is much more useful, being able to convert about 90% of the sun’s rays into heat energy. Today’s solar electric systems range from 12 to 20% efficient.
The return on investment can depend a lot on how an installation is done. In our case we already have a quite effective water heater so even if we did install a great solar preheating system it still couldn’t save us that much money. (A water heater also needsa backup system in place anyway for over cast days.) On the other hand we can certainly use an inexpensive source of electricity and after the various incentives it looked like we would be at break even for our electric roof in about four or five years. As far as the convenience, both solar electric and solar hot water systems take a little continuous maintenance. The hot water system would take more, especially in the summertime when they can overheat.
Since the south side of our house is the front of the house the appearance of a solar collector became an important consideration for us. Neither type of system could be hidden, but we were more comfortable with flat panel collectors for this reason. If it had been on the back of our home we would have seriously considered vacuum tube hot water methods.
When all the ideas were evaluated we decided that a large solar electric collector was right for us. I hope this article was at least somewhat helpful.
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