Wednesday, October 11, 2017

Shining a Light on Roof Solar Panels

Unless individuals make a move, energy alternatives will remain a bit player in addressing the challenges from fossil fuel emissions.  So, we decided to take the leap of roof solar panel installation for our home in Michigan.

Want to see how we're doing: ?

Step 1.  Plans and Contract

Research into solar powering our house started with an online search, followed by an expensive, out-of-state bid in 2016 and a more moderate bid from a Michigan company in early 2017.  Some email exchanges and then a formal proposal that was based on Google Earth imagery of our home (picture below; North is up).  No home visit occurred until later.

The bid is based on one year of electricity use, which, in our case, includes an outdoor hot tub (winter), A/C (summer), electric cooking and baking, but not requiring electric heating of water and air (besides well pump and furnace fan).  The calculation includes efficiency from SSE roof orientation and sun days, resulting in the installation of 30 panels that each can deliver 295W peak.  The total production represent ~100% of our electricity use on a full year basis.  Obviously, more electricity is generated in Summer when the Sun shines for more hours than in Michigan's Winter, while electricity use is inversely proportional to the seasons. Winter days are also affected by sun angle, which is much lower than summer, further limiting unimpeded panel illumination. 
The year calculation is below.

Our local energy company (DTE) only offers an energy credit structure for consumer electricity generation.  This is a key piece to consider before going this route.  Will the company offer energy credit as kWh during summer excess generation for winter use?  Does the company pay for excess energy?  The latter sounds good, but remember that they'll offer less per unit than they charge, and that they may require a long term lock-in rate that does not increase.  The latter is simply a bad deal.

On our area, DTE is an energy credit company, which guides the decision to install panels with power generation that about match our yearly usage.  In fact, the power company approves the maximum installation with this requirement.  Disappointingly, no incentives, credits or benefits are offered by town or state.  Luckily, a federal credit is available, which covers a substantial 30% of the full costs of installation.  Two nice gentlemen from Michigan Solar Solutions ( visited the house for roof and electrical panel inspection, and, after signing some paperwork, left with the down payment that started the process.

Step 2.  Approvals

It took 4 weeks to get approvals in place before installation.  Power company (Detroit Edison), city and township, even the county got involved.  Never seen that many interested parties and rules.  The power company was swift and supporting.  The civic approvals seem to focus on footprint and engineering specs.  The latter reflect the ability of the roof to carry the added load of solar panels, which should be ok for a typical home, and aesthetics.  A final building inspection took another week after panel installation, followed by the energy company's changeover another 2 weeks later.  Quite a few folks visited along the way.

Step 3.  Installation

Electricians and roof installers arrived around 8am and panels were delivered shortly thereafter.  The installation requires two vacant breakers on the breaker panel to connect with a controller unit outside.  This controller, in turn, connects with an inverter on each panel, requiring the installation of a thick wire tube outside the house.  That took about 3-4 hours.  Meanwhile roof workers installed racks to hold the 30 panels.  The panels are connected serial-like, allowing for replacement and additional panels.  A final outdoor switch was installed that cuts the system from the power company meter, as required, and shuts down the panels.  By 5 pm all panels and boxes were installed and running.  Drone camera images are below (courtesy of Jamal Hassunizadeh).

Running does not mean ready for use, however, as electrical and building inspections, and power meter changes are still needed.  The first two took another week and the meter change another 2 weeks.  Meanwhile precious late summer photons remained unused.  The inspections went smoothly.  Lastly the power company guy appeared on Friday afternoon at 5pm (after a couple of phone calls) to reprogram their meter to bi-directional metering.  Then the switch was permanently thrown.

Step 4. On

Remote power monitoring offers addictive opportunity for owners.  Weather has an entirely new dimension and clouds are cursed.  It is clear why they are called solar panels, and not light panels. The gentleman from Michigan Solar Solutions returned for their final payment a couple of days after the system went live.

Power and Energy

Energy is the ability to do work.  The unit is Watt-hour, meaning one Watt of electrical power, maintained for one hour: 1 Wh of energy.  Power means how fast the energy can be used, so it is energy over time; the unit is, thus, Watt.  A 30W lightbulb describes power, while energy consumed is a function of the time one uses that power.  Running a 30W bulb for 2 hours means 30*2=60Wh.  Have a look at this site for more explanation:

Today, our system of 30 panels is, for example, producing 5.5 kW, with an installed max of (30*295=) 8.85kW. In one day, it produces, say 30 kWh, which well exceeds our average use, but not by much. On a dreary and foggy day, the panels are producing a few hundred W only.  As the fog dissolves, this quickly moved into kW, peaking in the middle of the day when the sun is at its maximum.  Below is an annotated example record from the last 2 weeks of September.  Power generation should vary by season, peaking in late spring and summer.

A few surprises

Living in an area with frequent power outages, the panels will not supply energy to the home when the electricity grid is down.  This has to do, I was told, with frequency variations from consumer-grade generators and converter panel electronics that require active lines outside the house.  Glad we kept the generator for more than just nightime outages.  When, in the future, reasonably-priced batteries become available, the panels will be able to power the house without grid connection, after additional rewiring of charged batteries.  Note to Elon Musk: hurry up.

Installation of panels and electrical wiring took a day, but approvals and inspections drag on.  It took >8 weeks from signing the contract to operating the system.  The key step, energy company switch to solar metering, took another 2 weeks after all installation and inspections were done.  These permissions and visit scheduling alone are reasons to use a licensed contractor instead of managing installation oneself.

After a week the system went down (see image above).  A visit by the installer the next morning (quick response!) confirmed my suspicion that the problem was the home breaker box.  Ironically, the only part not new was the culprit, and an easy fix.

What about cost?

I am not sharing the actual cost of our installation, as this varies by size and region (and is nobody's business), but, based on our yearly electricity use and kW/h rate of DTE, we should see a positive return on investment after 10-12 years.  Clearly, this is not an investment strategy, but a moral choice.  The investment return calculation does not include price increases in electricity delivery (shorter return years), nor income loss from interest/investment of the money, or non-warranty repairs (longer return years).  Warranty should cover any malfunction for 6-10 years (depending on item), except for natural events like falling branches/trees, wind and hail, which are under the home insurance (with deductible).  We removed one set of branches that were overhanging, limiting two end panels' production.

The turnkey price of installation comes with a 30% federal rebate that is processed with that year's federal taxes (or prorated).  In shameless Michigan, no other incentives are offered, not even tax-exempt parts and installation.  A haircut has no taxes, but renewable energy does.

Stay tuned for a cost efficiency update in a few months, power production and any hiccups along the way.

[Follow Ben van der Pluijm on Twitter: @vdpluijm]


Andrew Dorsey said...

It's my understanding that while each module is connected in parallel , the individual cells within each of the 30 panels are in series. Which means the current output is only as good as the worst cell. In the drone image, it looks like the panels in the bottom left get some shade from the tree. Wouldn't this render a panel or two useless for part of the day, and drag down total output? Or am I seeing shade that isn't there, and it's just a darker blue reflection.

jim Morgenstern said...

I have been contemplating an installation similar in size to what you did.
* I found great disparity in pricing between national company ($45K), local company ($28K), and doing my own contracting ($22K). Is this what you found too ?
* Did your property assessment and taxes go up as a result of this 'home improvement'? If so, how much. For me, living in Ann Arbor proper, this is the deal killer at the moment; I believe my property tax increase will take a significant portion of the savings.



Ben van der Pluijm said...

Cells are in series with power cumulative into inverter, so lowest producer does not limit other panels.
Drone was taken at 7pm to limit glare. Daytime production varies by panel as sun rises and sets, and trees create shade. Individual panel production will be added to blog at later date.

Ben van der Pluijm said...

Jim- pricing varied, with local company offering reasonable rate relative to self-contracting; out-of-state bid was much higher. Also local company has greater incentive and is able to be more responsive.
Not sure about property tax increase, but I believe that township taxes differ from city.

PsychedelicPictures 421 said...

Hi, We also just recently had 30 solar panels installed on our roof through Michigan Solar Solutions. We have had a very positive experience with them. Although we were a little surprised how many inspections had to be done :) Currently we are waiting on DTE to to do their part to switch the system. It has been almost 3 weeks since the electrical inspection. Wishing DTE was a little quicker in their response time.

Buy Home Solar Panels said...

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