Andrew Gentile: Solar energy has a big carbon footprint

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This commentary is by Andrew K. Gentile of Sheffield, a self-employed electrical engineer.

Solar is an inherently inefficient energy conversion technology, and yet it provides over 19% of Vermont’s electricity. The state’s long-term plan is to be 90% renewable by 2050, a goal that doesn’t address the fact electricity produced from solar is about three times more expensive than from hydrocarbons.

Photovoltaics is an extremely valuable technology for certain applications, such as in the arid West, where solar can offset midday air conditioning loads. Solar can also provide power in remote locations, such as boats, airplanes, and for Vermonters living off-grid. For such applications, nothing competes with solar.

Despite these benefits, it is hard to argue that solar panels are cost-effective or environmentally friendly.

Solar panels are non-dense energy sources, requiring many times more land and material per generated kilowatt-hour than a natural gas plant. An electric tea kettle powered by solar would use 189 pounds of material and 80 square feet of surface. The materials — mostly silicon, aluminum, copper and silver — have to be mined, refined, processed, assembled and shipped, all of which are energy-intensive processes. Most of these materials are nonrecyclable and end up in landfills.

When you buy a solar panel, or anything mining-intensive, you are mostly paying for the energy that went into making it.

Our present desire for a clean environment driving us toward renewables was preceded by a similar desire decades ago, which then drove us to impose prohibitive restrictions on mining. As we find ourselves ironically transitioning to a very mineral-intensive world of solar panels and batteries, those mining restrictions further our dependency on foreign sources.

China produces 80% of the world’s polysilicon, and 75% of all solar panels. China burns diesel for mining equipment, coal for electricity, and heavy fuel oil for transoceanic shipping.

To achieve “green” status, the panel should be able to generate enough emission-free electricity to pay for its own production, and enough again to replace itself. If it generates only enough to pay for itself, then you have a net gain of zero. Instead of creating a solar panel, you could have generated electricity by burning the fossil fuels used in making the panel, and you would be in the same place.

How much electricity can a solar installation generate? Look it up using PVWatts, a photovoltaic estimator created by the National Renewable Energy Lab. Based on location and kW of panels you have (or intend to have), PVWatts will calculate how many kWh your panels are likely to generate in a year.

For Sheffield, Vermont, as the location, and 10kW for the size of the array, the result is 11,929 kWh per year, slightly more than the average home uses annually. For comparison, the same array would generate 17,644 kWh in Phoenix, Arizona.

At 16 cents each, the 11,929 kWh would earn $1,909 per year. This calculation is based on an avoided cost, meaning that the electricity generated by the panels offsets your electric bill, in which case you are getting paid back at the same rate you pay for electricity. If your system generates more than you use, the excess gets paid at a net metering rate, which is less than your billing rate.

At today’s prices, the 10kW array would cost about $38,500 installed, resulting in a payback period of over 20 years, and it would take 40 years for the panels to generate enough income to replace themselves.

The more expensive your electricity is, the less time it will take to pay back the cost of the panels. The average lifespan of a panel is 25 years.

Solar panels require fossil fuels for their production, and they typically don’t earn enough to replace themselves. So why are they considered green and renewable? If the panels cannot earn more money than was spent purchasing them, then buying the panels is no different from prepaying for electricity, except that the prepayments are going to fossil fuels burned in China.

Fortunately for buyers, the discouragingly long payback period on solar has been alleviated by large government subsidies. The federal government offers a tax credit to reimburse for up to 30% of the installed cost of solar. Efficiency Vermont also offers subsidies, and the state offers a property tax exemption. About 40% of the actual cost can be offset by subsidies, making solar an “affordable” option.

And while subsidies help homeowners, they don’t help the environment, and they hinder the transition to renewable energy. Hiding the true cost of solar helps us to pretend that it is cost-effective and that we don’t need to find a better solution. If solar was a sustainable energy option, it would not require subsidies.

If we simply used fossil fuels more efficiently instead of throwing money at solar, we would spend less money on energy, create less waste and pollution, be less dependent on China, and we’d probably end up burning less fossil fuels. The money saved could be invested into renewable energy research, or safe nuclear, leading us to a viable solution that is actually sustainable, renewable and clean.

By not openly addressing the shortcomings of solar, the experts promoting it are doing a disservice to the renewable energy transition. When solar can be used to power all the mining, refining, processing, assembly and shipping of the panels themselves, then it will be truly renewable. Until then, it’s just a hiding place for carbon.

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Pieces contributed by readers and newsmakers. VTDigger strives to publish a variety of views from a broad range of Vermonters. More by Opinion