Reflections on Solar Panels

An earlier version of the following was published in the Cranbrook Daily Townsman, Wednesday June 2, 2010. 

Renewable energy sources have been touted as essential alternatives if we are to wean our power-hungry society from petroleum based sources. However, these sources are not always as ‘green’ as they initially seem, often coming with unforeseen side-effects.

Wind energy has tremendous opportunity, but people next to wind farms report they are not ideal neighbours. Initial concerns over the effects of rotor blades on migrating birds may not be as severe as feared, but bats around wind farms in the Pincher Creek, Alberta area are highly susceptible to the microsite low pressure zones created by the wind mills and their lungs literally explode under certain conditions.

Ethanol was praised as a renewable gasoline saviour. Then someone did the math and found that six times more energy is required to grow the corn and process the ethanol than comes out the other end. A net cost to energy is not sustainable.

More recently, research out of Hungary, published in the journal Conservation Biology* raises concerns over solar panels emitting “polarized light pollution.”

The researchers examined the effects of solar panels on aquatic insects that are attracted to polarized light. These include mayflies, stoneflies and others that lay eggs in water where their larval stages develop. To the eternal glee of fly fishermen everywhere, the adults then emerge from the water, mate and lay their eggs back in the water to start the cycle anew.

The insects rely on smooth water to reflect polarized light as an indicator of suitable habitat to lay eggs. Previous work has shown that other surfaces reflecting horizontally polarized light, such as dry asphalt, dark coloured cars and even shiny black tombstones, are mistaken as suitable locations for insects to lay eggs.

This creates an “ecological trap,” a situation where novel (usually human-caused) environmental conditions lead an animal into situations that are counter-productive before evolution has a chance to catch up. Ecological traps are usually a behavioural phenomenon, where an individual makes a poor choice based on a long legacy of adaptation through natural selection. Nevertheless they can result in severe threats to animal populations.

The paper found that black surfaces of photovoltaic solar panels emit near total polarized light, much more polarized than water. This can lure aquatic insects to select these artificial surfaces over adjacent natural water bodies. The result is reproductive failure of eggs laid on artificial surfaces, death from exhaustion as the female tries to lay her eggs in “water” and increased risk of predation.”

However, the good news is that solutions can be found. Mortality in bats at the Pincher Creek wind farms has been reduced by up to 60% if the turbine blades are slowed to almost motionless during times of low wind. 

For the solar panels, the researches found that framing and partitioning the black solar panels with a white non-generating surface significantly reduced the attractiveness of the panels to insects.

Although gridding reduced the energy generation capacity of the solar panel in proportion to the amount of panel area lost, the benefits far outweigh the cost. A 1.8% reduction in generation capacity significantly reduced the attractiveness of the panel to susceptible insects 10 to 26 fold. The researchers noted, “the cost of effectively eliminating the attractive effect of polarized light pollution… amounts to a relatively small drop in performance of solar panels.”

Neither I nor the researchers are suggesting we scrap solar panels. Their potential remains vast. Further, not all solar panels need to be modified. Only where large solar farms are deployed in areas with limited water or where rare insects susceptible to "polarized light pollution" occur should precautions be likely necessary.

A better lesson is that keeping an open mind toward unintended consequences is important.

* A review of the paper in Conservation Biology was posted on Conservation Maven, May 5, 2o1o. Here.