7/20/2015: Guest blog from Ken — solar panels

We decided to get solar panels installed on our house.  These are the PV (Photo-Voltaic) panels which generate electricity, as opposed to another type of solar panel which uses sunlight on black panels to just directly heat up water in pipes.

The next decision was whether to purchase the panels, or to lease them.  Leased panels might be an attractive option because the company offering them would install them for next-to-nothing, they own the panels, you get the benefit of buying fewer kilowatt-hours from the electric company, and the company gets the SREC (Solar Renewable Energy Credits) from the electric company.  We decided to purchase our panels because A) We get the SREC credits, in addition to the lower cost (since we’re purchasing fewer kilowatt-hours) and B) they become an asset for the house when it comes time to sell the property. (Those who lease might be able to take the solar panels to their next residence).

It took a couple of visits for folks to get all the measurements they needed, take photographs of the roof, the electrical service panel, etc, etc. Basically gather all the data they needed to put forth an educated estimate.  Drawings were made back in April, and since a bunch of weight was going to be added to our roof, a professional engineer needed to sign off on the drawings to say that our roof wasn’t going to collapse under the weight of panels, gadgets, wiring, in addition to the typical snow and ice.  (The company took care of all this.)  Originally, there was quite a backlog of installations to be done, and we were initially told July, then August.  Fortunately, sometime in June we got word that there was some time available for a crew from North of Boston to do the work, so it was scheduled for July 2.

Installation typically would take about two days.  Our install started on the Thursday before July 4th weekend.  No one worked on that Friday, so they returned on the following Monday to continue work.  I say ‘typically’ because: Our house, on the South-facing rear roof has a dormer over a 3rd floor bathroom.  The roof over this bathroom has a very shallow slope.  When the roofing was recently redone, the surface of this roof was done as a rubber roof, instead of shingle.  (We’d found out in February that shingles on this shallow slope had helped ice dams form and water enter our home uninvited.)  The Solar Panel Company can and does install panels on rubber roofs – but for whatever reason, they didn’t get some part(s) in time before starting our installation, so they needed to return on a third day to finish mounting panels on this middle-dormer-shallow-sloped roof.  Nothing had been left exposed or at-risk during the interim.  I don’t know whether it could have been completed in only 2 days, had the necessary parts been on-site.

I think of the installation as two halves that met in the middle.  As a crew of roughly 3 people worked on the roof of the house mounting rails and related hardware on which to mount the panels, an electrician worked in the basement mounting the inverter and related accessories, and running wires which eventually met up with the first team.

solar1

The gadgets-and-gizmos-a-plenty:

Let’s start at the top and work our way down.  We have 16 panels on the roof: 4 on the middle dormer, and 6 on each side.  Each pair of panels has an ‘optimizer’ connecting them. The job of the optimizer is to keep a panel(s) which might be covered by shade or otherwise not being very productive, from negatively affecting the productivity of the entire set of panels. I.e. if 3 or 4 panels are covered with shade or snow, or got broken by a falling pterodactyl, the other panels can still provide useful amounts of current. So: 8 Optimizers (all mounted on the roof, under the panels). Also on the roof is a ‘Gateway’, which talks to the optimizers, and receives commands wirelessly from a control panel on the corner of the house.

The current that comes from the optimizers is all joined together (well actually, in two halves.  I’ve got a + and – for the 1st eight panels, and a + and – for the 2nd eight panels), but all this current comes through one hole in the roof (probably about an inch in diameter) into my 3rd floor closet.  From there (inside appropriate conduit) it goes to a decent size breaker box on the wall of the closet, perhaps a little less than a foot square, maybe 3” deep.  This is so that if ever a worker needs to trouble shoot the system, they don’t have to climb on the roof to de-energize the rest of the system.  The generated electricity can be safely shut off from the comfort of the third floor closet.

Behind this junction box is a hole in the wall, where high-voltage DC wires start their route (again, within appropriate flexible metal conduit) following a plumbing vent pipe, down three floors to our basement, where it then goes across the ceiling to the inverter.

The inverter is a fairly sizable box which must be mounted at least 3′ above the floor (for flood-paranoia reasons) on it’s own portion of wall space. It can’t be mounted under a basement window (for other moisture-related-paranoia reasons*).  Connected to it are two smaller boxes.  One is a meter, which will show how much power the panels have generated over the lifespan of the system.  The other is a pretty simple shut-off. I’ll describe more about shut-offs later.  The large inverter box also has a small screen on which I can check the status of various parts of the system.

solar2

Hanging below the DC Disconnect is what looks like a shiny soda can.  Think of this as a mondo surge suppressor.  In case the panels on the roof get hit by a bolt of lightening, this will keep that from damaging anything else in the system – or the house.

Now we finally get to some useful stuff.  From the inverter, power (now Alternating Current, matching the rest of the electrical service in the house) now runs to the breaker panel in the corner of the basement.  Get that? “TO the panel”! That’s the good and exciting part!  I now have a double-sized breaker in the panel which connects (or not) the generated power to the rest of the service. “A-Ha,” you say, “Another shut-off?” Yup – get over it. There’s more to come.  Also at the bottom of my breaker  panel is another new shiny-soda-can/lightning arrester; so lightning that hits the AC side of this system doesn’t feed back into the inverter and damage it that way.

In addition to all this, I now have two more small boxes mounted on the outside of the house, in the corner by the electrical service.  One is a simple, grey service disconnect box, similar to the one by your typical air-conditioner condenser outside your own house. The other is a small panel for monitoring and controlling the stuff on the roof. Most importantly, this control box can be used to remotely turn off the panels on the roof. (Yep, I know… wait for it. There’s more.)

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Alright, so just how many ways can all this new technology be kept from being productive? Or in simpler terms, how to turn it on?  Well, I can’t really. Not yet. I’m still waiting for N-Star / EverSource to come and replace my current (pun not intended) meter with a “Net” meter.  Not ‘net’ as in the ‘internet’.  But ‘net’ as in “accounts for all the pluses and minuses.”  The meter I have now (like any meter that any house without solar panels would have) is only smart enough to account for power being supplied to the house.  Not only does my meter not understand if I provide power back to the grid, but I would actually get charged for it! I.e. If I generate more power than I need at any given moment, not only would I not get credit for supplying it to the grid, but my meter would mistakenly think it’s going in the other direction and the electrical company would think I’m using their power, and charge me for it.  Hence I haven’t ‘turned on’ my system yet, since I’m waiting for a meter that can tell the difference between power I’m buying and power I’m supplying.

When I do, I’m told can turn on all these switches in any order, but here’s the list I’ve come up with:

1)  Third-floor closet DC Junction box – This is already connected and will stay that way unless/until service personnel deems it necessary to disconnect the power generated by the panels from the wires leading to the basement.

2)  Inverter switch – rotates a quarter-turn to let the DC power from the roof supply lines into the inverter.

3)  Breaker in my breaker panel – needs to be ON to allow the AC power from the inverter to connect to the rest of my house (and the grid).

4)  Disconnect mounted outside the house needs to be ON, just like #3. The difference here is that this disconnect is readily available to the fire department or other first responders if they deem it necessary to use.

5) The Control box outside the house (next to the Disconnect) needs to remotely tell the optimizers to start letting through the power made by the panels.  This box is important because even if the first responders use the adjacent disconnect to turn off the inverter, there can still be dangerous voltages on the roof, and in the wires leading to the basement!  If firefighters are heading up to my roof to save my life, limb or property, nobody wants them getting a fatal shock.  This control box is capable of a “Rapid shutdown” where the control box sends a wireless signal to the ‘Gateway’ on the roof, which in turn tells the optimizers to stop energizing the DC side of this system (between the roof and the inverter in the basement).

Other tidbits:

– If there’s a power outage, guess what?  I lose power.  “It takes power to make power” said one of the installers. “Um, I uh… ok.” said I (I’m paraphrasing, but not by much.)  I think there are electronics inside the inverter that need – ironically – to be plugged in to the supplied service.

– I’m not storing any power in batteries.  If I make less power than I’m using then I buy what I need from the electrical company to supplement it.  If I make more than I need, then the excess goes to the grid, and I get credit for it.  Effectively, the electrical company acts like my batteries; I take from it when I need to.

– Soon I should get pointers to a website(s) where I can monitor my production, broken down panel by panel.  It uses data from the new meter in the basement, and I think it might be possible to engage and disengage the system from that interface.  It’ll generate pretty graphs for me and show me what credits I’ll be getting from the electrical company.

– The fact that our panels aren’t visible from the street is a fortunate coincidence. The rear of our house faces south – the direction facing the sun most often.  If our house had been on the other side of the street (or I suppose, located in the southern hemisphere) then the panels would be a permanent part of the aesthetic of the front of our house.

– We got our roof redone prior to installing the solar panels.  The original impetus for this was the ice dam damage cause back in February. However, if the panels went on while we still had a few years of life in the roof shingles, then at some point the panels would have to be removed (for the roofers) and then re-installed.  Since we’d purchased the panels that would be an added expense.  Those who lease panels can probably get their company to remove & reinstall panels for free for re-roofing purposes.

– When the roof was done, we had 3 skylights removed, including one on the 3rd floor.  We found the skylights to be great at letting heat out in the wintertime, almost as good as they were at letting solar energy heat up our rooms in the summertime to make our air conditioning work harder.  This wasn’t the type of solar power we wanted. By getting rid of the skylight on the 3rd floor, they were able to fit 2 more solar panels on the roof.  (Also: no more skylight-related leaks in the kitchen!)

– The control panel mounted on the outside of the house needed to be (wait for it…) plugged in.  I now have the exterior power outlet that I’d been intending to install for the past 5 years.

– In between the installation and the replacement ‘Net’ meter, we got a visit from the City electrical inspector. Everything passed.  Scheduling such visits is usually a bit of a nuisance, but it worked out well this time.

– The new meter in the basement and the Disconnect outside the house each have a small padlock to protect curious people from harmful voltages.

– Red stickers abound, warning all who approach about dangerous voltages, letting electricians know that some conduit contains DC instead of AC, and that there is potentially more power at the service panel than one might think.

– If you like numbers, the solar company that installed everything estimates that the system will produce roughly 4500 kilowatt-hours per year.

– If you want to know more, find me at the next block party; I’ll be happy to chat.

* I say ‘paranoia’ with tongue-in-cheek. Obviously, if the National Electrical Code deems such things necessary, I’m sure there were plenty of examples of scary experiences leading up to the rules.  Since I don’t claim to know more about electricity (in this context) than the folks who wrote that book, I’ll be abiding by all their suggestions.

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