Category Archives: renewable energy

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 did I miss this?

On a deep energy retrofit like ours, the clock is always ticking. Not only was it ticking, recently the alarm went off too: I have known for a number of years that I had till this year (2016) to install renewable energy components and claim the juicy 30% Residential Renewable Energy Tax Credit.

pv-panels-01

We are interested in a photovoltaic and solar hot water system. Knowing that the time to claim the tax credit was running out, I took the first steps of organizing the project and was surprised – pleasantly surprised:

The tax credit has been extended. With limitations, but still, it has been extended.

The government actually got something done! Wouldn’t you think that’s BIG news? I can’t believe that I missed this.

“Note: The Consolidated Appropriations Act, signed in December 2015, extended the expiration date for PV and solar thermal technologies, and introduced a gradual step down in the credit value for these technologies. The credit for all other technologies will expire at the end of 2016.”

Source: Energy.gov

The good news: The Residential Renewable Energy Tax Credit for photo voltaic and solar hot water system was extended until 01-01-2022.

The bad news: The Residential Renewable Energy Tax Credit for fuel cells, wind turbines and geothermal heat pumps is still running out at the end of this year (2016).

“A taxpayer may claim a credit of 30% of qualified expenditures for a system that serves a dwelling unit located in the United States that is owned and used as a residence by the taxpayer. Expenditures with respect to the equipment are treated as made when the installation is completed. If the installation is at a new home, the “placed in service” date is the date of occupancy by the homeowner. Expenditures include labor costs for on-site preparation, assembly or original system installation, and for piping or wiring to interconnect a system to the home. If the federal tax credit exceeds tax liability, the excess amount may be carried forward to the succeeding taxable year. The maximum allowable credit, equipment requirements and other details vary by technology, as outlined below.”

Source: Energy.gov

But – the clock is still ticking. Here is more fine print: If you would like to claim 30% of the Residential Renewable Energy Tax Credit on photovoltaic and solar hot water, you have until the end of 2019. From 12-31-2019 till 01-01-2021 the tax credit for systems placed in service is reduced to 26%. And for systems placed in service between 12-31-2020 and 01-01-2022, the credit is further reduced to 22%. Once you’ve missed this last deadline, you are left hoping for another extension.

You can access details about the Residential Renewable Energy Tax Credit here:
http://energy.gov/savings/residential-renewable-energy-tax-credit