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Exploring solar for my home

Updated: Jul 22, 2023

I began exploring solar power generation for my home after convincing myself it was time to jump in and purchase an electric vehicle. My view on the carbon footprint of power generation has evolved over my academic career in teaching and research. The fact is that there is a carbon cost for everything in our lives and we consciously or unconsciously choose to pay it. One of my favorite examples which I shared with my students in my lectures is that in the production of a 9 Oz cup of coffee, about 3 Oz of oil is used. A rough estimate is that 3 Oz of oil is about a half pound of carbon dioxide equivalent. The simple truth is that food production uses oil. Modern farming technology requires tractors, combines, harvesters, pesticides, dryers, fertilizers etc., all of which consume fossil fuels. To put it in another way, you would be hard pressed to find something we own, touch or use that doesn't use oil or has a carbon footprint. This reasoning also holds for power generation technologies. There is, what I will call, "a carbon investment" that is required to bring a power generation technology into service.

In a previous blog I introduced the concept of an energy multiplier for power generating technologies, which I called the energy "Q" value. In a nutshell it is the expected energy production over the lifetime of the power source divided by the energy investment required to bring that power source into operation (such as mining materials, transportation, processing, construction etc.). Currently, most of this energy investment uses fossil fuels so there is an associated "carbon investment" (or footprint if you like) to build a power plant and make it operational. When Tushar Ghosh and I wrote the Energy Resources and Systems books, listed on my website, over 15 years ago, solar photovoltaics had a Q value of less than one, wind power was about 2, and natural gas fired power plants, coal fired power plants as well as nuclear power were about 5. As photovoltaic cell technology improved over the years its Q value increased. I last looked into photovoltaic cells 6 years ago and its Q value improved to about 1.03 for commercially viable systems.

I explained in a previous blog why I chose to purchase an EV at this time. To summarize, the city of Columbia has a very good strategic plan for implementing renewable energy. That means that even though most of the electricity on Columbia's grid is still generated with fossil fuels, a larger percentage year after year will come from renewable sources and some will be purchased off the grid where a fraction will be generated by Ameren's nuclear power plant. Yes, a "nuclear power plant"! Remember, I am a nuclear engineer who chose to go into the field 50 years ago because I am an environmentalist who believed it was critical to develop non-carbon based energy sources. Nuclear energy is one of the best ways to limit carbon production.

As previously stated, everything we own has a carbon cost. An electric vehicle still has a "carbon investment" which is no better than the "carbon investment" made in producing a gas powered automobile. However, I look at it this way, if you consider that anything that uses energy will have a "lifetime carbon multiplication factor". This means that you will produce carbon no matter what fuels the car and you use carbon when you maintain it. The question then becomes, what type of vehicle will have the lowest carbon impact over a lifetime. My reasoning for choosing an EV is that it will use less carbon over its lifetime.

Why am I now considering a home solar power system? I am still looking at the "carbon investment". If the present state of technology hasn't changed in the past six years since I last looked at the "Q" value for solar plants, it would still be 1.03. This is still a 3% savings. This "Q" value assumes a lifetime of 25 years. However, it appears that 25 years may be too conservative. It is probably higher. Anything beyond 25 years is very good. An additional consideration is that higher temperatures during the summer will put a strain on the electrical grid. Since I believe that climate change is real, this is a consequence that will only get worse. Regular brownouts and blackouts are a real possibility in the future. Anything that will reduce the strain on the electrical grid is good. A further consideration is the cost savings. Right now the payback on a home solar system is between 7 to 10 years. If you take out a loan to pay for the system, you can mostly pay off the loan from the reduction in monthly electric bills. Plus, electricity rates will only rise in the future. For example, this fall Columbia will impose a 7% increase in its electricity rate. If I find that I can put in a solar system, and I am able to get a fixed rate loan, then my payment will be fixed. So, I will not have to worry about future electricity rate increases. Right now I think the benefits for looking into solar are worth it. Plus, when I charge my electric vehicle, I know where the energy comes from. I can live with that.

A resource for calculating greenhouse gas equivalencies-

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