Thinking in terms of energy return on investment


When evaluating renewable energy options, people often focus on the mere fact that a given technology, be it wind, geothermal, or solar, produces renewable energy. What is given less attention is the energetic cost of building that piece of technology or the energetic costs of managing that piece of technology. The lifetime cost of the equipment from an energetic perspective, so to speak.

As wind and solar power come onto the grid, issues related to intermittency and the need to store power on the grid are becoming increasingly important. A group of authors at Stanford’s Global Climate and Energy Project have just completed a paper looking at the most promising technologies for storing solar and wind power. The authors wanted to know which renewable energy source provided the largest energy return on energy investment when one considered the reality that the technology has to be paired with some form of grid storage. Effectively, which technology made the best energy return on investment when paired with battery storage.

The paper concludes that solar and not wind power makes sense energetically when storage costs are considered. Interestingly, the energetic cost of building a wind turbine is actually lower relative to solar panels. But what the authors wanted to know was whether the energetic cost of curtailing (shutting down) solar or wind power, because the grid can’t take the excess power, was more or less than the energetic cost of storing that power in batteries. It was in the case of solar but not for wind. Moreover, among 5 battery techs tested, lithium ion provided the best energy return on investment.

Wind is still a much cheaper technology than solar but perhaps this study will cause utilities to consider curtailment and energy storage costs when evaluating a technology.

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