Monday, April 18, 2016

Green Energy Rain or Shine, Night or Day: The Future of Solar Energy

By Andrea Lang, Energy Fellow

Science is trying to remedy one of the most often cited downsides of solar photovoltaic energy, its intermittence. That is, solar panels do not generate energy at night, and operate less efficiently in rain, fog, or cloudy weather. This intermittence can lead to significant problems for grid operators trying to balance production and demand, because as solar output drops off, more traditional sources of energy must quickly “ramp up” production to compensate for that loss of electricity production. Since it takes time for fossil fuel-fired plants to ramp up that production, grid operators have a hard time meeting demand if too much solar production drops off at one time due to weather or time of day.

But, if there’s one thing science teaches us, it’s that just because something is a problem now doesn’t mean it always will be. And happily, scientists are already hard at work and making progress to address these issues with solar energy. Here are just a few of the extremely useful (not to mention nifty) projects scientists and engineers are working on right now that will hopefully lead to consistent, constant, and –most importantly–renewable solar photovoltaic energy.

Graphene Solar Panels: Rain or Shine

Widely reported last week, Chinese engineers announced that they are working on a way to generate electricity from rain that falls on solar panels by using graphene, a two-dimensional sheet of carbon molecules arranged in a honeycomb pattern (pictured right). Graphene has very high conductivity, resulting in a large amount of electrons flowing across its surface. The researchers propose to take advantage of the positive ions present in trace amounts of salt in rainwater, which form a double layer with the graphene electrons. The difference in electrical potential between those two layers (the positive ions from the rainwater and the electrons flowing through the graphene), with the water in between, creates a type of “pseudo-capacitor” which can generate electricity. 

In addition to this recent development of generating electricity from rain using graphene, the material also has long been thought to be the key to making solar panels more efficient. The main trouble with graphene is that it’s been inefficient (and therefore expensive) to produce in large quantities. However, just as the technologies to apply graphene are evolving, so is the technology to mass-produce it. Scientists at the Massachusetts Institute of Technology announced improvements in graphene production technology last summer. Although these technologies are in the development phase, they represent a promising start in terms of generating electricity from solar panels, rain or shine.

Space-Based Solar Power: Night or Day

On Earth, night always rolls around eventually and eliminates electricity generation from solar panels. But space doesn’t have that constraint. That’s why scientists have been exploring the possibility of collecting solar energy in space and literally “beaming” it down to Earth.

Space-based solar collection would work by launching solar collectors into low orbit, and then using either laser or microwave beams to transmit that energy back down to Earth, where it would be collected and added to the grid.

However, space-based solar collectors are likely to be very expensive. Not only do scientists have to perfect the technology to make them work, they have to develop the technology and spend the money to launch them into space. According to the Department of Energy, it would cost in the tens of billions of dollars to assemble, launch, and operate a solar collecting and beaming satellite.

However, if the technology can be made cost-effective, space-based solar energy has other benefits besides the ability to collect solar energy day or night. First, a significant amount of solar energy is lost by the time the sun’s rays penetrate Earth’s atmosphere and hit land-based solar panels, even when it isn’t a cloudy day. By collecting that energy before it is lost in the atmosphere, space-based solar energy collection would be much more efficient. Second, land-based solar collectors, especially utility-scale arrays, occasionally come into conflict with aesthetic, natural or cultural resources. Space, though, is literally wide-open, so space-based solar collectors won’t have to compete with other valuable resources. 

As these exciting new technologies continue to develop, the potential is clearly there to overcome the obstacles posed by widespread solar deployment. These are just two examples of many technologies in development that can help solar energy become more efficient, constant, and reliable.