Ground mount vs Roof mount?

[bcroe]

How much more complicated / expensive is adding variable tilt to a ground mount?

Tracking is quite a project. My E-W arrangement accomplishes about
the same without the complications. And E-W performs far better under
clouds, tracking can do nothing. Bruce Roe

[vnatale]

The microwave oven was one exercise in cutting down my
electrical vampire loads, which were some 100 devices and
300W, or 2,630 KWh per year. A KILL-A WATT meter will easily
make measurements of plug in stuff. I did design a small circuit
added to the microwave, others might go the replacement Energy
Star route. Things like the furnace, central vac, seurity devices,
doorbell, chargers, wireless phone, computer devices, smoke
detectors, door openers, TV remote monitor and distribution
system, and more have small transformers running 24/7, burning
several watts each. I trimed around 80% of that over time.

The 100A upgrade makes your solar possible. 200A would be
more comfortable, but would would involve the feed wiring and
possibly the PoCo pole transformer, besides the box.

That appears to be a very energy efficient house. Say you use
200 gallons of oil a year, 200 gallons X 0.85 eff X 40 KWh per
gallon = 6800 KWh. If you change to electric resistance heat
with 100% efficiency, you would need that production plus
your electric energy use, from your solar. Heat pumps with
efficiency from 100 to 300 % efficiency will reduce your need.
A mini split heat pump for your 75 F room will be more efficient
than a simple space heater. This if your net metering contract
allows energy collected in the summer to be used one for one
in the winter.

Doing all of what I discussed would be very difficult on a roof
mount. Double sided is for an east-west arrangement. Can work
on a roof, but optimum elevation is likely a lot steeper than your
roof.

The reasons for a 2 sided array here are to get near twice as many
productive hours out if a solar day, and to double the output under
clouds. It sacrifices individual panel efficiency, while maximizing
use of your mounts, electrical equipment, and net metering contract.
It works here by wiring an east facing string in parallel with a west
facing string (individual fuses). Since they do not produce peak
power at the same time, the inverter sees them as just a single string.

Here is a pic of my first 2 sided array, and a graph of more optimized
dual string output, 8 hours of peak production. Bruce Roe

3Direction.JPGNScurJn17.jpg

Again. A lot of different points to respond to here.

1) You are motivating me to finally do something with the microwave. First put a meter on it for several days just to see what its light is drawing. Then make myself remember to turn the strip off after each use.

2) I am looking at a Kill-A-Watt meter on my table that I've had for a number of years. I had bought another one but loaned it to a neighbor and never saw it again. I have bought three of these:

Poniie PN2000 Plug-in Kilowatt Electricity Usage Monitor Electrical Power Consumption Watt Meter Tester w/Extension Cord - - Amazon.com

They came highly recommended on Amazon and were cheaper than Kill-A-Watt. Seems to do just as good a job. Plus it comes with a short cord to plug the device you are measuring into and then the cord into the meter. Makes it easier to plug in some devices rather than going straight into the meter.

3) I have a lot of things that run all the time in. But nowhere close to the devices that you have that have transformers that are constantly running.

Several years ago, though, I did put all my many, many pieces of living room equipment, e.g., TV, amplifiers, that were on "instant on" on a strip that gets shut off when they are not in use. I was shocked how much electricity that saved. Maybe a 20% reduction in total electricity used?

4) All six vendors who quoted me last year gave me a passing grade for the 100 amp service.

5) My house was built somewhere between 1945 and 1955. Several months after I bought it in 1982 I had it insulated - blown in insulation in the walls and the attic. I recently had the inches in the attic raised from 9 to 15.

6) Three weeks ago I had a 6,000 BTU Mini Split installed in each of the two bedrooms and an 18,000 BTU Mini Split installed in the living room to cover the rest of the house. Each of are on their own separate heat pump.

One of the reason that the Mini Split appealed to me was how little electricity they used in comparison to space heaters. I just looked at the old style space heater I have in my bathroom. Top setting 1,500 watts! I had assumed Mini-splits would use even more electricity so was quite surprised when I saw a 6,000 BTU one was in about the 400 watt area?

And, yes, the net metering contract allows excess summer buildup to be used during the following winter.

7) Now that you have shown a picture I am remembering to ask .... how does one put a picture in a post? Once I am able to do that you will see what limited space I do have on the south side of my house. Would not be permitted on the west side of my house since that is the front of my house. The east side would not work because my house would shade it once it reaches a certain time each day.

You have WAY more available space on your property than do I. My total property is 0.38 acres, I think.

[Mike 134]

From here: What does BOS stand for? — Page #4 (abbreviations.com)

It seems like it could mean close to a 100 different things! Good thing I asked.

I thought it meant Balance of System
Search (portalced.com)

[vnatale]

From the Dummies index, see p. 264 of the 2d. ed., 1st para., 1st word.

Also, see any solar panel data sheet for details and parameters of std. test conditions. I specify STC as identifying the panel power rating as different from other ways of rating a panel which do little more than muddy the water and confuse people and are therefore B.S. The STC method keeps everyone on the same page and is the standard by which all panels are rated and their output measured.

From my version in the book .. nothing in the index:

standalone photovoltaic system, 249
stand-off mount photovoltaic system, 255
static lighting, 129, 354
stationary water, 233
stationary windows, 39
stock portfolio, 10
storm windows, 40, 57
string DC-to-AC inverter, 257–258

First sentence of first paragraph on page 264 is: "The most important consideration is the wire size, and you need to consult
tables in the NEC (National Electrical Code) to determine which sizes work optimally for your application."

I did twice search the PDF for both STC and Standard Test Conditions and came up with nothing for either.

But most importantly ... I do understand your point. Basically want to be to do the proverbial "apples to apples comparison" and not be comparing apples to oranges.

[vnatale]

BoS== Balance of Sale.

From here: What does BOS stand for? — Page #4 (abbreviations.com)

It seems like it could mean close to a 100 different things! Good thing I asked.

[J.P.M.]

Thanks for the quick response. I will officially take that off my list of desired options.

By the way ... I just did a search of the Dummies book and no match was found for either "STC" or "Standard Test Conditions".

From the Dummies index, see p. 264 of the 2d. ed., 1st para., 1st word.

Also, see any solar panel data sheet for details and parameters of std. test conditions. I specify STC as identifying the panel power rating as different from other ways of rating a panel which do little more than muddy the water and confuse people and are therefore B.S. The STC method keeps everyone on the same page and is the standard by which all panels are rated and their output measured.

[bcroe]

I could put a meter on the microwave for a few days to see both how much it uses per minute when cooking plus how much it is using when it is just idle. I do have it on a strip that I could easily turn on and off as needed. I tried doing that but kept forgetting to shut it off.

Was that circuit to automatically disconnect it your own design?

I have a small house - about 900 square feet. When I bought it nearly 41 years ago it had a 60 amp service which was enough. It was half fuses and half circuit breakers. 10 years ago I had it replaced with a 100 amp service. The panel box is huge. I had been only using about 7 circuits until the three newly installed mini-splits each with their own heat pumps each took a circuit. I still have possibly 20 open slots left.

I have an oil furnace. Last efficiency reading I have on it was 2017 when it was at 85%, which is the same as what it had been in 2010.

Since it is usually only me in the house I tend to hibernate in my bedroom during heating season. That lets me keep the house temperature at 60 degrees while keeping my bedroom (through supplemental heat - space heaters) at around 75 degrees.

Doing that leaves me using about 175 gallons of oil year. I only had my 275 gallon tank filled four times in six years.

When you asked: "Have you done this calculation?" I do not know what the formula is to do the calculation.

When you are describing your use of strings ... not clear if you are referring to a roof mount or a ground mount?

Not following making the ground mounts being made double sided? My goal is to orient it south. I'd get nothing from having anything on the other (north) side.

The microwave oven was one exercise in cutting down my
electrical vampire loads, which were some 100 devices and
300W, or 2,630 KWh per year. A KILL-A WATT meter will easily
make measurements of plug in stuff. I did design a small circuit
added to the microwave, others might go the replacement Energy
Star route. Things like the furnace, central vac, seurity devices,
doorbell, chargers, wireless phone, computer devices, smoke
detectors, door openers, TV remote monitor and distribution
system, and more have small transformers running 24/7, burning
several watts each. I trimed around 80% of that over time.

The 100A upgrade makes your solar possible. 200A would be
more comfortable, but would would involve the feed wiring and
possibly the PoCo pole transformer, besides the box.

That appears to be a very energy efficient house. Say you use
200 gallons of oil a year, 200 gallons X 0.85 eff X 40 KWh per
gallon = 6800 KWh. If you change to electric resistance heat
with 100% efficiency, you would need that production plus
your electric energy use, from your solar. Heat pumps with
efficiency from 100 to 300 % efficiency will reduce your need.
A mini split heat pump for your 75 F room will be more efficient
than a simple space heater. This if your net metering contract
allows energy collected in the summer to be used one for one
in the winter.

Doing all of what I discussed would be very difficult on a roof
mount. Double sided is for an east-west arrangement. Can work
on a roof, but optimum elevation is likely a lot steeper than your
roof.

The reasons for a 2 sided array here are to get near twice as many
productive hours out if a solar day, and to double the output under
clouds. It sacrifices individual panel efficiency, while maximizing
use of your mounts, electrical equipment, and net metering contract.
It works here by wiring an east facing string in parallel with a west
facing string (individual fuses). Since they do not produce peak
power at the same time, the inverter sees them as just a single string.

Here is a pic of my first 2 sided array, and a graph of more optimized
dual string output, 8 hours of peak production. Bruce Roe

3Direction.JPGNScurJn17.jpg

[J.P.M.]

Another unknown acronym for the uninitiated! "BoS"?

BoS== Balance of Sale.

[vnatale]

These days, not very, and probably impractical from a reality standpoint.
Given the problems and required maintenance associated with tracking systems as well as a general violation of the KISS principle as well as the decrease in panel prices over the years, the no brainer part is that while a tracking system may increase the specific output of a system (in kWh/yr. per installed STC kW), the same output results can be obtained by simply upping the fixed array size. Also, a tracking system's costs/installed STC kW may well put it beyond cost effectiveness for the application.

STC == Standard Test Conditions. See the Dummies book.

Thanks for the quick response. I will officially take that off my list of desired options.

By the way ... I just did a search of the Dummies book and no match was found for either "STC" or "Standard Test Conditions".

[J.P.M.]

How common is sun tracking?
Vinny

These days, not very, and probably impractical from a reality standpoint.
Given the problems and required maintenance associated with tracking systems as well as a general violation of the KISS principle as well as the decrease in panel prices over the years, the no brainer part is that while a tracking system may increase the specific output of a system (in kWh/yr. per installed STC kW), the same output results can be obtained by simply upping the fixed array size. Also, a tracking system's costs/installed STC kW may well put it beyond cost effectiveness for the application.

STC == Standard Test Conditions. See the Dummies book.

[vnatale]

Ground mounts will be easier to service/maintain/clean, they can use sun tracking upgrading will be easier and cheaper and a lot more scaleable assuming you have the space. Yes, if the ground is surrounding by tall buildings/trees/mountains then of course that scenario it wont be suitable but that also applies to roof mounts.

How common is sun tracking?

This seems to be the only vendor offering something in my area and the company owner has already stated in an email to me that I am a fair distance away from them: Tracker mounted backyard solar panels VT NH MA | Solaflect Energy

Vinny

[vnatale]

I disagree there is an "overwhelming" advantage. Ground will often produce more than roof-mount, but BoS costs are much higher. And I've seen a few examples where PVWatts estimates were lower for ground mount than roof. Roofs, being higher up, get less indirect shading.

Another unknown acronym for the uninitiated! "BoS"?

[vnatale]

Probably helpful for DIY, but being off grid is a lot of ongoing work and maintenance that's usually more effort than a part time job. It's a different ballgame than grid tied.

As soon as I finished reading the Dummies book last night I started reading that one. However, I think it may be the most poorly written book I have ever read in my life. It possibly could have been written in a different language then poorly translated to English. But it did go into a lot more substantial depth than the Dummies book in all the details of the components of a solar installation.

[vnatale]

You're welcome. Keep learing.Your biggest enemy will be your lack of education.

After page 85 and until page 250 the book went into a rather large diversion into a lot of uses for solar aside from a whole residential solar installation. A lot of it was somewhat interesting but of marginal value in understanding a whole residential solar installation. Finally on page 250 there was one chapter on whole residential solar installation followed by another chapter on how to deal with contractors. Those were the most valuable chapters in the book.

On page 275 there was nearly a full page box titled "Common Terminology". It started off with: "You’ll need to understand some basic industry terminology in order to work with solar PV systems" It then listed these 8 terms: Load, Volt, AC, DC, Ampere, Resistance, Watt, Watt-Hour.

I may have no solar experience but I have had decades and decades of exposure to all those electrical terms and was quite familiar with all of them.

Brings to mind a discussion I had with an electrician one day who was clearly not understanding all the terms.

I asked him why he was configuring some lights to use a certain voltage or amps. He told me he was doing so because then they'd use less electricity. He did not understand when I tried to explain to him that raising one was going to lower the other because the light was still going to draw the same amount of watts no matter how much he raised or lowered either the amps or voltage. Watt used, of course, is how the light usage ultimately gets billed.

[vnatale]

You are going down the same energy saving trail as me. 100%
solar electric was achieved 9 years ago. Getting numbers on everything
reveals a lot. A meter connected for a month revealed that the 4
decade old electric range was using far less than 1% of my energy.
The microwave was an efficient cooker, but its clock was a vampire
load using more energy in a year than the short time cooking. The
cure was a circuit to electrically disconnect it from the outlet 7 min
after it finished cooking and the door was closed. It stayed at zero
energy until the next time the door was opened.

Finding and replacing older inefficient appliances really helps.
Chasing down vampire loads on some 60 circuits here turned up
half a hundred things that could be improved.

Your 100A service and transformer size are a limit, but possible
with the size equipment you are looking at. My situation is similar,
but the numbers are about 2 X yours at this originally all electric
home built in the 70s.

Sizing my max Solar output at 15KW, was based primarily on the
heat load over a year. I knew how many gallons of propane were
consumed in a year, and a gallon has the energy of 27KWh. But
electric resistance heat is near 100% efficient, and the furnace was
less than that, so I needed to generate about 25KWh from solar
to replace each gallon of propane. PV estimates indicated I would
be a bit short, but the plan was to buy the energy shortfall while
continuing to try and improve the efficiency of the house. My chart
says about 40 KWh have the energy of a gallon of oil, do not know
the efficiency of your furnace. Have you done this calculation?

The efficiency gain was done here several different ways. One was
to use (6) heat pumps to boost heating efficiency to anything from
100% to 400%, depending on how cold it was. There are a few
really cold days when the heat pumps drop to 100%, but overall
there was a big surplus. It was sufficient that I was then able to
maintain a shop well above freezing all year, and a quite comfy
working 65F most months.

The other improvement was to boost solar energy collected. Peak
power was limited to the same above, and also by my net metering
contract and inverter size. What was not limited was how many
hours I could collect solar energy. Normally peak power only lasted
several hours around solar noon. But I replaced a string facing south,
with a pair of strings facing east and west. First the east panels
deliver energy from the morning sun, then the west panels deliver
afternoon energy. With an elevation of near 57 degrees, the power
(limited by the same string inverter) is about the same but for twice
as long.

This scheme gives a big increase in energy collected without an
increase in peak power. It is also quite effecive in increasing output
under clouds of varied density. It reduces the effectivness of the
cheap PV panels, but greatly increases the utilization of all the rest
of the system. Even the ground mounts, which may cost more than
their panels, can be made double sided for considerable economy.

I am finding, my mini heat pumps are excellant for drying clothes
hung in front of them, receivng a lot of use in the winter when outdoor
lines are unusble due to the weather. So much so, I am considering a
couple of short lines to be easily hung near each mini. I do have an
unvented heat pump clothes dryer, but it tends to run too cool for the
job. Its virtue is not sending a lot of heat outside, the heat pump seems
redundant in that all heat remains in the house and and largely in the
machine. For summer of course clothes dry outside. Bruce Roe

A lot to respond to here!

I could put a meter on the microwave for a few days to see both how much it uses per minute when cooking plus how much it is using when it is just idle. I do have it on a strip that I could easily turn on and off as needed. I tried doing that but kept forgetting to shut it off.

Was that circuit to automatically disconnect it your own design?

I have a small house - about 900 square feet. When I bought it nearly 41 years ago it had a 60 amp service which was enough. It was half fuses and half circuit breakers. 10 years ago I had it replaced with a 100 amp service. The panel box is huge. I had been only using about 7 circuits until the three newly installed mini-splits each with their own heat pumps each took a circuit. I still have possibly 20 open slots left.

I have an oil furnace. Last efficiency reading I have on it was 2017 when it was at 85%, which is the same as what it had been in 2010.

Since it is usually only me in the house I tend to hibernate in my bedroom during heating season. That lets me keep the house temperature at 60 degrees while keeping my bedroom (through supplemental heat - space heaters) at around 75 degrees.

Doing that leaves me using about 175 gallons of oil year. I only had my 275 gallon tank filled four times in six years.

When you asked: "Have you done this calculation?" I do not know what the formula is to do the calculation.

When you are describing your use of strings ... not clear if you are referring to a roof mount or a ground mount?

Not following making the ground mounts being made double sided? My goal is to orient it south. I'd get nothing from having anything on the other (north) side.