Rooftop Solar Planning in Southern Maryland

Sulfur wrote: »

I have a somewhat similar system to what your proposing, see signature below. I have been happy with SMA so far except their real time trending capabilities are weak. If you are capable of installing it yourself, I highly recommend it since it will cost about 1/3 as much or less. I bought Sharp panels on Ebay and inverters on Ebay, one used one new old stock, all have worked great. I bought some of my panels from mlsolar on ebay, I was pretty happy with that seller, I bought some others from a different seller that I did not care for. Golf cart batteries at Sams club, Sunny Island from SolarHome. I have an all electric house (in MT), so I use a lot of electricity (probably 24MWh annually).

I have 2 strings of 14 panels on a roof at 17 degree angle and 2 strings in the yard at 32 degree angle. You can see production stats for my system at link below. I grew the system a bit so it was not complete till May of this year even though I started making power in 2012. Sunny Island is usually turned off so there is almost no data for that hardware. Sunny Island and batteries in my system are only used if the grid goes down. Are you planning to want to be able to produce and use power when the utility grid is down?

http://www.sunnyportal.com/Templates/PublicPageOverview.aspx?page=6c250b01-cc65-45fb-b2ba-844482f3f367&plant=fcd8d862-94dc-4111-8afe-94093c625323&splang=en-US

Do you get snow where your at? If so, there is a lot to be said for putting the panels on the ground. The max I have seen my system produce in a day is 100 kwh, a marginal day like today it made 18 kwh. One thing I like about SMA is that, on or off grid, the panels and inverters can feed my house with 240VAC without going in or out of batteries. I have fed the house off grid with 10,000 watts without pulling anything out of the batteries, but I was able to make the System choke trying to start the 4 ton heat pump because the compressor in rush current load was too much for the batteries and SI to handle even when the rest of house was not using much power. Luckily I have a wood stove, so if grid is down I can heat whole house with that since my solar system will not start heat pump, I could get 2 SI's and it would probably work but it is not worth it to me, I know how to burn wood fine.

westbranch wrote: »

Sealing the duct work? get the silver duct sealing tape , a bit pricey and seal every join you can find, especially the ends, then go around and use the back of your hand to see if you got them all.

Hardest to do is where a round duct comes out of a square one...fidgetty

Blackcherry04 wrote: »

Well with Grid Tie, You have to think two ways. If you have a outage will the PV panels be compromised and the GT unusable. If it is then you need a plan B and C. There is a new SMA Inverter 5000TL-US inverter will have a built in Up To a 1500 watt output when the sun is shining and the grid is down. This output could be used to charge a set of batteries that you could bring on-line with another Inverter at night or the sun is not shining.

My Plan says the PV will be compromised, so I have a stand alone Inverter a small set of batteries ( 4 GC-2's ) and a Honda EU 2000. I can charge during the day and run some loads and run the Inverter at night with essentials ( Refrigerator & and a couple lights ). The Inverter is a 3000 watt, to large for that size battery bank, but the Inverter is just the Catcher for the loads. It has Generator Support and can supplement the Generator when necessary.

All that said, If the 5000TL-US inverter was available, I'd of bought one and had it in my plan.

Sulfur wrote: »

I used painted lumber for my roof mounted panels as well, but the aluminum systems are surely better and look cooler. I only plan to be in this house another 15 years and I am confident they will last that long if I keep the exposed wood painted. My roof panels face a deep valley, so looks are not important, no one sees them.

My panels are B grade, they are great in my opinion. The 300 watt panels will likely be larger unless they are significantly more efficient, which I doubt. The bigger and heavier the panel, the harder it is to physically wrestle up to your 25' roof, but they can be done. Mine were heavy too by the time I attached some lumber to them, which was before I put them on the roof. Roof mounting was MUCH faster for me than the yard panels since I did not have to build a structure that would resist blowing away.

take good measurements of the roof and do a layout of both size panels, see what fits best. Keep in mind you still need to be able to walk up there, unless you plan on renting a manlift, which may be smart since your roof is so high.

The battery system I have is small, Sunny Island recommends minimum of 100Ah capacity, mine is 208Ah @48VDC. I just keep a Iota float charger on them and keep the SI turned off. If I had a house that was off grid all the time, I would install a much larger battery bank. I installed a 200A manual transfer switch so I can isolate my whole house from the utility grid and power all circuits with the solar system off grid, rather than just critical loads, this is not the norm I would say. When on grid, the Sunnyboys will turn off with loss of grid, when transferred to the Sunny Island, the transfer switch isolates from the grid. SI has limited current capacity through its isolation relay, this is why I did it this way.

Regarding your question about feeding house directly with 240VAC, most hybrid systems feed power into batteries and then invert to 240VAC, there are more losses with that method, so if your planning to be on grid most of the time, then SMA may be a good choice. If the grid goes down, my system does require interaction from me since my transfer switch is manual, most hybrid systems switch automatically, the SI will also switch automatically if you limit the circuits that are backed up and have them passing through the SI all the time. I am about to build another solar system at my cabin and will use this more traditional method at that site for phase 1, which is only 14 panels.

If you plan to install the system yourself, hopefully you have access to a good electrician for advice, also read the installation manual carefully before you buy anything, so you understand everything very well. I am an engineer and brother is master electrician, it has been fun science project. It is not that complicated to install, system design probably takes more thought. You may want to post details of system design on this forum for people to poke holes in before you buy stuff, you might get some good ideas that change your design.

Blackcherry04 wrote: »

One thing I do in your case is to address your heating costs. I'd get a HVAC contractor out to come up with some suggestions they would stand behind. There many Thermostats that have many more options since you house was built for instance, that allow more adjustments to customize it more for your home. I added 6 remote sensors that average the temperature, that made a big difference in mine for $30 each.

Blackcherry04 wrote: »

Sounds like your covered there, it was just a thought. Even though it doesn't fit you, a lot of people that read this it might help them.