Solar lingo

Now that we get into renewable energy systems, let’s take a quick look at the terminology.

There are solar (or photovoltaic) cells. You typically find 60 cells on residential and 72 cells on commercial solar (or photovoltaic) modules . You can see that our Panasonic modules have 96 solar cells, which makes them a premium module. The module is the fundamental and most visible building block of a solar electric system, and is often referred to as solar panels.

When a number of modules are installed into one power generating unit, it is referred to as a solar (or photovoltaic) array.

As you can see in the pictures below, our system has modules with 96 cells each, and the array consists of 26 modules total.

The solar cells produce direct current (DC). Yet the electricity we use in our buildings is alternating current (AC). To convert the direct current into usable alternating current, we need an inverter.

The direct current from the solar array flows to the inverter, where it is changed to alternating current. The inverter is feeding into our electrical panel (or load center), from where the alternating current can power electrical loads in our home, such as the fridge, dishwasher, vacuum, lights, the TV and radio, our PC’s and laptops, etc.

If the solar array generates more power than we need in the building, it flows from the electrical panel through our smart meter back into the electrical grid. This is possible because smart meters have two channels. Channel A measures the energy flow FROM the grid. Channel B measures the flow of energy TO the grid. Using a smart meter to feed electricity back into the grid is called a grid tied system. Unlike off grid systems, we do not have to rely on batteries. The grid is in effect our battery.

For a grid tied system to operate property, we need to link our solar electric system to the grid of our electric service provider (ComEd). This process is called interconnection, and requires approval from the electrical service provider.

Once the systems are interconnected, we can receive credit for the excess electricity we generate. This credit process is called net metering, which we also need to set up with our electric service provider.

There will be more information on the details of Interconnection and net metering in an upcoming post.

In summary, the key terms to remember when talking about a solar electric system are:

  • Solar cells (PV cells)
  • Solar modules (PV modules)
  • Solar array (PV array)
  • Inverter
  • Electrical panel (load center)
  • Smart meter
  • Grid
  • Grid tied system

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Renewables

We reached the point in our Chicago deep-energy-retrofit where we get to work on the renewable energy component: a solar electric system in our case. Needless to say that we are super excited.

The topic of renewable energy generally creates a lot of excitement and buzz. So let me throw in a word of caution:

If you are on a path to make your home more energy efficient, the renewable energy component should be at the very end of your list. First take steps to reduce the overall energy demand of your home, because this is where you get the biggest return on your investment.

A general rule of thumb that I have come across says: every $1 spent to improve the efficiency of a structure saves $3 to $5 on the cost of a renewable energy system. That said, I did not find any research that backs up this claim.

Nevertheless, it rings probable: I did an initial performance analysis back in 2012 and 2016. I took energy data of a building comparable to ours prior to any energy improvements and compared it to our energy usage. I converted both data sets to a square foot basis to get an apples to apples comparison.

By 2016 we had reduced our heating load by 80%, while our electrical consumption decreased by 57%. And keep in mind that we were still working on the building, meaning that there still were lingering inefficiencies.

The bottom line is a renewable energy system for our house would be 1/2 to 1/4 the size of what it would have been prior to any energy improvements. This translates into major cost savings.

And then there are spatial limitations to keep in mind.

Take a solar energy system, i.e. photovoltaic panels in an urban setting. The panels are typically mounted on the roof. But any given residential roof can only accommodate so many photovoltaic panels.

The lower the energy use of a home, the more likely that the panels on the roof cover the majority, if not all of the energy needs, which again translates into major cost savings.

How do you improve the energy efficiency of your home? I provided some guidelines in the previous post. But there is plenty of more information in this blog. Just search the blog for keywords like “building shell”, “insulation”, “air sealing”, “windows”, “heating”, “space conditioning”, “moisture management”, and “ventilation” and you will find plenty of reading material on energy efficiency strategies.

Ok, the “word of caution” turned into several paragraphs. In the next posts, I will get into the basics of solar PV and our journey to the system installed, including all preparations. Stay tuned!

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How do I start…

… with energy improvements on my home?

This is probably the question I get most often.

Whether you are thinking about smaller improvements or bigger ones, like our deep energy retrofit, here are some guidelines on how to go about it.

The big picture

It is not just about energy improvements, but it is also about where you get the biggest bang for your buck. So let’s take a look at the big picture.

For more data go to: https://www.eia.gov/consumption/

The 2015 chart above from the U.S. Energy Information Administration shows that up to 54% of energy for a single family home can go towards space conditioning (i.e. space heating and cooling). Only 5% of energy goes towards lighting.

If you decide to make your lighting more efficient, i.e. go with all Energy Star LED lighting, I applaud you. However, the total resulting energy savings may be around 1-2%. That’s something you may barely notice on your electrical bill.

If instead you would focus on improvements to your building envelope, i.e. your basement floor, foundation walls, crawlspace, exterior walls, wall penetrations, windows, exterior doors, attic, and roof, you could make a major dent in the 54% of energy that goes towards your space conditioning. This is where you can get a big bang for your buck. And not only that, you likely end up with a home that is a whole lot less drafty and a whole lot more comfortable and healthy to live in.

The bottom line is, don’t focus on the low hanging fruit. Look at the big picture and focus on the energy hogs, such as space conditioning.

Verify and quantify

You decided to not just chip away at your energy use but instead to make a dent, maybe even a really big dent.

Based on the data above, you know that you likely need to focus on your building envelope in order to reduce your space conditioning loads. But how good or bad is your building envelope, and what is the actual space conditioning load for your home?

It’s time to find out. Commission a home energy audit. A professional energy auditor will visit and inspect your home, analyze your utility bills, and may run several tests such as a duct, furnace, and blower door test.

For more information on home energy audits go to: https://www.energy.gov/energysaver/home-energy-audits/professional-home-energy-audits

The energy audit report will point you to the areas where energy improvements can be most effective. The most significant recommendations will probably point you to building envelope improvements, such as insulating, air sealing, door or window replacement, etc.

With this data and recommendations in hand, you can begin to strategize.

Weatherization

You have a choice. Even basic insulation along with good air sealing (also called home weatherization) can save you an “average of 15% on heating and cooling costs (or an average of 11% on total energy costs)” according to Energy Star information.

For more information go to: https://www.energy.gov/energysaver/weatherize/air-sealing-your-home

Depending on how handy you are, weatherization can become a DIY project or you can hire a weatherization specialist that does the air sealing and insulating for you. If you hire someone, make sure that you contractually set performance goals based on the home energy audit. This means how much more air tight the house should be after the improvements and what cold spots should be eliminated with insulation. And at the end, go and verify. In other words, have your energy auditor come back to test that the performance goals are met.

Energy model

You want to aim higher and save more? Good for you!

In this case I recommend commissioning an energy model, which your home energy auditor could provide. And if not, he or she can probably recommend someone. We commissioned an energy model in the planning phase of our project, which guided us through the decision making process.

An energy model takes a wide variety of building variables into account (type of windows, type of insulation, building exposure, air tightness, etc.) and predicts the energy load of your home. By adjusting the variables (i.e. thickness of insulation, type of windows, level of airtightness, etc.) you can see how the energy load of your home increases or decreases.

Say you want to decrease the energy load of your home by 50% or more, which puts you into the realm of deep energy retrofits. The energy model will help you to determine how to get there. It tells you what level of air tightness you need to achieve. It tells you what levels of insulation values you need, and where. It tells you what performance targets your windows and exterior doors should meet. And so on.

Decreasing your energy by 50% or more will involve major remodeling as you probably have to work on all exterior walls and the roof from the inside, the outside, or both.

Sounds daunting? Well, it can be. But there are silver linings here too.

Major remodeling allows you to get to all those quick fixes and deferred maintenance items that have been causing problems and eating money for years. And of course, you are left with major energy savings.

Take our deep energy retrofit. A preliminary analysis in 2016 showed a 80% reduction in our heating needs, and 57% reduction in our electrical use in 2012.

Be picky with your contractors

You will need help from various building trades with a deep energy retrofit. I highly recommend relying on contractors that specialize in energy improvements, or that are at least familiar with the topic. Working on energy improvements, such as in a deep energy retrofit, takes a very different mind set compared to regular construction, as the installation and construction processes often vary from the old norm. A recipe for disaster is a contractor that is set in the old ways, because that is how he/she has always done it.

Don’t tiptoe

Aiming high, such as with a deep energy retrofit, may seem expensive and overwhelming. You may think you should start in small increments instead.

Please think again.

Going about your improvements incrementally, each step in the process seems less overwhelming and less expensive. I’ll give you that. However you keep tiptoeing around big ticket items and associated savings (such as the above mentioned space conditioning). And you will likely end up undoing some of your own work along the process.

In the end, you may have spent cumulatively more on incremental improvements than on a deep energy retrofit with far less energy savings than you would have had if you didn’t tiptoe..

Learn how to operate your home

Owning a home, energy efficient or not, requires you to know how to operate it.

It is similar to owning a car: If you want to drive, you need to know how to start your car, how to steer it, how to accelerate and brake. You need to know what kind of gas you need, how to put gas in the tank, check tire pressure, check oil levels, etc.

The same is true for a home, in particular if you like to maximize your energy savings. You need to know when to change or clean which filters and when to schedule service appointments for what equipment. You will have to program and monitor your thermostat and other monitoring equipment. You should become familiar with the basics of indoor air quality (IAQ) and learn the basics about moisture management.

Owning a home is not a hands-off operation! There is no chauffeur. You need to drive if you intend to maximize your energy savings, assure the durability of your home and systems, and maintain a healthy and affordable living space.

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Container framing

Now that I managed to get some daylight into the container, I thought of the best way to store equipment and materials. To maximize the space, I needed to hang things on the inside walls.

That was easier said than done, considering that the walls are steel. And I did not want to put screws or any other kind of fastener or any holes through that steel wall.

The idea that emerged was to frame the inside with a few two by four studs that would provide the support for hooks and other things I may want to attach to the walls. And it turns out that a two by four fits rather nicely into the ribbed indentions of the container walls.

To hold the stud in place, I screwed a small block at the bottom into the wood floor. I used another stud across the ceiling and attached it to the two by fours in the walls with an angle iron. This horizontal piece is basically a blocking at the top that secures the framing firmly into place. Certainly firmly enough to hold my ladders.

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Painting the container

I finally had my container shed, but it was super dark inside, even with both doors wide open in the middle of the day. The rust-red paint on the inside seemed to absorb most of the light that gets in.

That had to change. I was not in the mood for rummaging with a flashlight through the back of the container each time I had to get something out. I wanted a lighter and more reflective color on the inside, such as white.

Yet I was not in the mood to paint the inside with a brush or small roller. So I went ahead and invested in a small paint sprayer that I also could use for other projects later.

Using a paint sprayer was a smart move, if I may say so, turning this painting project into a really quick job. And the result delivered exactly what I had hoped for – some more light that would allow me to find things even in the back of the container.

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