Proposal for solar panels on our garage

[Lsbcal]

Yes, I've seen some of this as well. And an old thermal solar installation that was almost completely blocked by trees 10 years later.

Some opinion piece some where(it was a while ago) mentioned that if we are going to give subsidies for solar, it ought to at least be based on actual production, not installed capacity. That would eliminate some of this incentive to install as many watts as possible for the subsidy.

-ERD50

So there are no building codes and inspections for solar installations?

 

[Markola]

Residential installs fail at all levels, compared to larger industrial/commercial installations). For residential, there is no economy of scale. Every site has to be analyzed, permitted, transfer switches installed, a crew has to get set up, and on to another place for each small installation. The roofs are steep and dangerous for the crew. The roofs are almost never at the optimal angles and/or free of shade (and future shade from growing trees). It's a stupid thing for the government to promote.



Put panels on a large flat roof (school, big box store, etc) and you have one crew working the same job for much longer, one site review, much safer working on flat roofs, easy to place at the proper angle and avoid shade. Residential in comparison is just wasting the valuable resource of the panels, which are very energy intensive to produce.

That makes a ton of sense.

 

[ERD50]

So there are no building codes and inspections for solar installations?

I'm not sure what you are asking? More context please.

-ERD50

 

[Lsbcal]

How could someone mistake the location of a solar array? Shouldn't codes force a decent location away from trees and wrongly facing roofs? Shouldn't installers be required by codes to somewhat optimize an install?

 

[NW-Bound]

There are codes and inspections. However these only apply to safety issues. Each piece of equipment must be UL listed, for example. Wiring and grounding must be done to codes, etc...

It is hard to mandate certain orientation of the panels, or levels of shading by trees, or neighbor's roofs. Most of the orientations I have seen are suboptimal. How suboptimal is permissible? You will have to analyze the system output over a 12-month period, in order to cover all sun angles.

 

[ERD50]

How could someone mistake the location of a solar array? Shouldn't codes force a decent location away from trees and wrongly facing roofs? Shouldn't installers be required by codes to somewhat optimize an install?

What NW-Bound just said.

Also, there are a lot of shady (pun intended!) installers. As long as some [-]clueless[/-] uninformed person is paying for (part of) it, the installer will put in the panels. If the installer says "hey, this panel will be shaded most of the day, doesn't make sense to add it", they lose the sale on that panel. But we, the taxpayer get to pay for some of it anyhow. It's ridiculous.

Happens a lot. Maybe not quite so egregious as that as often, but I'd say the vast majority of residential installs are producing less energy than the equivalent dollars invested in a commercial scale installation. It's a waste.

-ERD50

 

[OldShooter]

How could someone mistake the location of a solar array? Shouldn't codes force a decent location away from trees and wrongly facing roofs? Shouldn't installers be required by codes to somewhat optimize an install?

I can't speak to solar specifically, but the codes are not leaders. They are followers, attempting to keep up with new technologies* to maximize safety and construction quality. Hence, when new they are to a degree a guess. Then, as experience is gained, they are updated to reflect the new knowledge. I't bet that if you looked at the code relating to wooden house foundations, you'd see a decade or two of evolution from revision zero.

So maybe the codes "should" deal with location (I don't know) but it doesn't surprise me at all that maybe revision zero didn't.

*I have served on three national standards committees and have seen this first hand.

 

[NW-Bound]

And then, there are times you intentionally allow a certain level of shading in exchange for being able to mount more panels. Here's an example done in commercial installations.

Panels are mounted in rows, facing south, tilted to the sun ray, which of course is not vertical. The tilt angle is obviously a compromise, because the sun angle varies with the season. You may want to optimize it for overall annual production, or to maximize production for either summer or winter, while reducing the output at other times of the year.

And then, the rows of ground-mounted panels must have a certain spacing, in order to keep a row from shading the one behind it. If you space them at the correct distance far apart for the low angle of the winter, then you have fewer panels for the same area. What if you intentionally crowd them a bit closer than the optimal distance, knowing that you give up a bit at the early and late hours in the winter, at which time the panels don't get much light anyway? This allows you to mount more panels for the same area.

And then, there are panels specially made so that they don't lose a lot of output if they are partially shaded along the bottom edge in the early and late hours. I did not know about this type until I happened to see some surplus panels sold in the retail market. These are not intended for residential installations, obviously.

Commercial installations do a lot of optimizations, because they know what they are doing. Home owners usually know diddly-squat.

 

[NW-Bound]

It's good to know the OP is not in Alaska. Solar panels don't work too well there.

Even at summer solstice, when you have nearly 24-hour sunlight, the sun angle is very low, and worse, it runs around the horizon. You need to mount the panels on a tracker that turns 360 degrees in azimuth to chase the sun as it runs around you.

 

[finnski1]

First, chop down some trees and burn them for heat. Then, you have a clearing for your ground mounted solar array. Problem solved.

I love ground mounted arrays. Wish I have a bigger lot than what I have right now. It's easier to build, easier to wire up, and to protect from strong wind, does not mess up the roof. What's not to like?


PS. You may even be able to use the downed trees for lumber to build the mounting frame for your array. Beautiful.

Fair enough. But did I mention it is A LOT! of trees. Heck even to do a roof version I would still need to cut down quite a few trees. Living in southern NH isn't the ideal solar location but it would work reasonably well. The last 12 months my total usage was only 4080 kWh or 340/month with a low of 231 in May and a high of 575 in Aug. Last years annual bill was $889 or $74/month. I only get a reasonable payback period if I were to do the purchase and install myself. Because I am picky and a serious DIY 'er that is what I would do anyway

 

[NW-Bound]

PVWatts calculator at nrel.gov says that a standard 320W solar panel tilted up 45 deg will produce about 1 kWh/day in the winter, and 1.35 kWh/day in the summer, in Manchester, NH.

Just about 15 panels will get you all that you use. But of course that's on the average because there will be cloudy or snowy days when you get zilch.

I can get new panels in town for 15 x $150 = $2,250. You can now get a 6-kW inverter/charger along with a 13-kWh lithium battery for $6,100. The rest is lumber, wiring and miscellaneous hardware.


PS. Once you have the basic system, additional solar panels bring a very good marginal return for more kWhs, but you need to find ways to use the extra power during the day, else you will need more battery. For example, I run the pool pump during the day, and also the water heater. The water heater is turned off at night, and coasts until the morning.