Solar Power International 2015 Pre-Event Showcase - Page 10

in South America, a forward military operating base in South Asia, or a remote vacation resort in Canada might all have microgrid electricity supply as their common denominator despite their substantial differences in geography and purpose.

The second solar electricity revolution

With these developments, grid-tied and off-grid solar diverged down two paths. The first focused on technological and economic improvement to the panels and modules needed to collect and harvest solar electricity, while the second made comparable progress in the power conversion electronics and energy storage methods required for off-grid operational success.

Not surprisingly, solar electricity’s growth in the developed world heavily favored the grid-tied model with its relatively simple systems consisting of solar panels and an inverter (and later multiple microinverters). Still representing the majority of residential and commercial PV/solar systems in use today, grid-tied types can offset utility electricity use, sell back to the local power grid, and take advantage of all government, regional and utility-based incentive programs to ensure that their owner/operators maximize their return on investment.

But as grid-tied solar became more widespread, its impact on grids and energy scenarios—and its inherent limitations— increasingly became more of an issue. Consider, these regional examples:

• California: now representing over half of the entire United States PV solar market (SEIA, 2013), California also has that country’s most aggressive renewable energy goals: a state mandated 33 percent of electricity from renewable sources by 2020, up from the previous requirement of 20 percent, and primarily from solar and wind, excluding hydro. But adding that much power from renewable sources that fluctuate widely can create grid instability, and will—California state experts predict reliability problems as soon as 2015 if the trend continues and conventionally-fueled power plants have to keep making up the difference caused by renewable’s inherent intermittency when the sun isn’t shining or wind isn’t blowing. As the Wall Street Journal reported last year in

California Grids for Electricity Woes, “many of the solar and wind sources added in recent years have made the system more fragile, because they provide power intermittently"

• Hawaii: because island utility power is invariably diesel-generated, it is very expensive as that fuel must be transported to local power plants. After years of providing incentives for solar electricity, the utilities are beginning to pull back on them, fearing the much-publicized “death spiral” where more solar users means that utilities must pass on their fixed electricity generation costs to fewer customers. This results in higher prices and creates even more “grid defectors” as the utility’s remaining customers discover that even with limited or no incentives, solar for self-consumption is a financially-attractive option. This, in turn, raises electricity prices even more and encourages more defectors, exacerbating the effect.

• Germany: as the most solarized country in the world, Germany is now faced with mitigating against potential “grid collapse” under the right conditions. As former U.S. Department of Energy undersecretary David Garman and Samuel Thernstrom of the Energy Innovation Reform Project noted in a recent article, “the strain is beginning to show…there are increasing reports of challenges resulting from wind and solar across the grid, including frequency fluctuations, voltage issues…anxious operators are concerned about potential blackouts.”* To address the problem, the International Energy Agency estimates that Germany will need to invest nearly $100 billion in power transmission and distribution upgrades over the next decade.

This is an excerp from Optimizing PV Systems - Energy Storage published by World Of Photovoltaics. You can read the full e-feature here

ximum system voltage below either 600 V

energy storage FEATURe continued from page 8