Apr 09 2013

Assessing Solar Energy

I’m a big fan of solar energy, and specifically photovoltaics (PV). The earth is bathed in free clean energy, far more than we need to run our civilization, and all we have to do is harvest it. But, of course, it’s not that simple.

There are many ways to calculate the efficiency and effectiveness of PV technology. One way it to calculate its cost-effectiveness compared to other forms of energy. The bottom line for any consumer is this – if you install PV in your residence, what is the total cost of installation and maintenance compared to the cost savings of the energy produced?

You can also think about the energy efficiency of PV – what is the total energy cost of manufacturing, maintaining, and disposing of PV across its lifetime compared to the amount of electricity it generates.

Another way to think about solar energy that I had not previously considered, until a recent study was published on the topic, is the net energy costs and production of the entire PV infrastructure. If you consider the world-wide PV industry, how much energy has it consumed compared to the amount of energy generated by installed PV?

You may be surprised to hear that we are just now (probably) crossing the threshold where solar energy is producing more energy than it consumes.

A study by Dale and Benson and published in Environmental Science and Technology analyzed the energy inputs and outputs of the entire solar industry and concluded that as recently as 2010 solar energy was a net energy consumer. They calculate that there is a 50% chance that in 2012 solar power crossed the line to producing more energy than it consumes. They further conclude that the net energy deficit produced by the solar power industry will be paid off by 2020.

Therefore, we can assess PV technology on an individual, societal, and global scale. If I am deciding whether or not to install PV on my rooftop the factors to consider are this – what do the PV panels cost to purchase, install, operate, and maintain, what is their longevity, are there any rebates or incentives available in my state, how much sunshine does my house get, how much electricity will the PV produce, and how much does my electricity cost? This all calculates to the bottom line – when will my investment likely be paid back in energy cost savings?

We can also take the global view as in the current study, which affects decisions about where and how to create PV infrastructure. Essentially what this means is that we should focus our efforts on promoting PV in those areas where energy efficiency is going to be the greatest. This may not be the same areas where cost effectiveness for individuals is greatest.

For example, a high sunshine state with low cost existing electricity may not be as good for the individual, but is optimal when considering the total infrastructure. Therefore government incentives may need to be higher in those states.

I was unclear on one point from the article – did they consider the energy cost of PV R&D? I wonder how much of a contributor this is. Perhaps it is minor enough to ignore.

In any case, taking the long view R&D is worth the investment. PV technology is improving incrementally every year. I follow science new pretty closely, and I think I can say without exaggeration that hardly a week goes by without a publication about some potential advance in PV technology. Perhaps we won’t have the dramatic sudden breakthrough we would like to have, but slow steady progress adds up over time.

Scientists are developing new materials, new manufacturing techniques, and tweaks to existing techniques that add efficiency, increase durability, ease installation, and lower production costs. While efficiency of conversion of sunlight to electricity is the sexiest feature we look for, the cost (both dollars and energy) of manufacturing is perhaps the most important.

The final question, which I can only touch on in this article, is this – what are the key barriers to expanding the solar infrastructure? I hear two answers – cost effectiveness or political will. The latter is primarily determined by the current cost of electricity production. As long as relatively cheap electricity is available from fossil fuel or other types of energy plants, they will crowd out solar.

Those who believe it is more a matter of political will argue that the current situation is mostly the result of priorities – subsidizing the fossil fuel industry vs investing in solar research and infrastructure. Germany is offered as an example of this, as they have invested heavily in solar power. They currently generate about 3% of their electricity from PV.

Given the rate of technological advance in PVs it seems likely that projections of cost and energy efficiency of PV are going to get significantly better. If we make it a priority, by somewhere between the middle and end of this century we could be living in a solar powered world.


Note – Some of my thoughts above are based on a conversation I had recently with my brother Joe who works in the energy efficiency industry.

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