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Study: Grid-Tied Solar Still Outperforms Solar with Storage, and Politicians Should Take Heed

Posted by Matt Power, Editor-In-Chief

Feb 1, 2017 8:27:15 PM

Yes, the world needs better batteries, but the possibility of freedom from the grid should not become an excuse for dismantling net metering.

A Univ. of Texas at Austin Cockrell School of Engineering report just published research suggesting that home batteries for solar create more GHG emissions than grid-tied systems.solar grid connected.jpg

Here’s an excerpt:

[Researchers] found that storing solar energy for nighttime use increases a household's annual energy consumption — in comparison with using solar panels without storage — because storage consumes some energy every time it charges and discharges. The researchers estimated that adding energy storage to a household with solar panels increases its annual energy consumption by about 324 to 591 kilowatt-hours (8 to 14 percent). Source

This should come as no surprise. Even when batteries and inverters reach 100 percent efficiency, batteries are unlikely to match the grid in terms of ecological impact. They’ll still have limited lifespans, and require resource-intensive materials such as lithium to construct.

We need better batteries, yes. But right now, there’s a gold rush mentality as companies worldwide rush to create a power storage economy. Behind this rush is innovation—longer lasting cells, infinitely more sophisticated charging—but the other part is uglier. It’s the political threats to net metering coming from utilities and climate-denying politicians.

Evolution, Not Panic

A mainstream move to onsite storage should “unfold” as a backup plan for net-zero and off-grid homes first—not rush in to fill an emergency need for homes suddenly cut off from net metering. And when I say cut off, I mean that literally. Many grid-tied systems today automatically shut down when the grid goes down, to avoid backfeeding solar power into a broken power line, so often, having a battery storage system is an “either or” proposition. This is the way my system from Revision Energy in Portland, Maine, works. Either you’re plugged in to the grid, or you can’t access your battery bank. I’m sure there are costly, custom solutions out there. But they’re not the norm.

Despite that surmountable drawback, it’s easy to understand why interest in battery storage is surging. For homeowners who have $30,000 worth of panels on their roof, the end of net metering in their state could be a devastating financial blow. They are left with three options. Absorb the loss. Sell the panels. Or add battery storage. This is not hypothetical. In December, Arizona canceled its net metering program. Fortunately, they left in a “grandfathered installation” clause that protects homeowners with panels already installed. Citizens in other states may not be so lucky.

The grid has the advantage in that it is ALREADY BUILT and available to homeowners at no additional cost. Each solar installation acts as a tiny power plant, feeding clean, low-cost power into the existing grid. This forestalls construction of dirty power plants for the utility. And let’s face it, in the near future, utilities will likely redefine themselves as energy managers, not power providers.

Surge Protection

The market for solar is surging. To keep doing so, net metering is key. Storage is a big added cost for homeowners leaning toward PV. Battery systems such as Powerwall2, said to be coming to market this year, start at around $5500, plus installation. Adding 30 percent to the cost of a solar array could slow down adoption quickly. And that’s assuming a single battery pack is enough to power the home.

At present, home storage systems account for a tiny percentage of installations. But as I’ve written before, when describing my own thought process regarding solar (see p. 48). In my own home state of Maine, our anti-solar governor, Paul LePage, has threatened to undo our highly successful net metering program. The loose cannon occupying the White House also could decide to to tear up existing federal tax credits for solar, making net metering even more essential to the solar transition.

There are other wild cards, as well: The soaring popularity of electric cars offers tantalizing storage options for home solar. Plug in your car and you have a ready-made portable battery. Of course, if you drive in the yard from work with an empty battery at 5 p.m., those panels won’t have time to store any energy for overnight use.

Pressure to roll back net metering is likely to continue, until utilities find their new place in the smart grid future. In this rocky transition, we need to to weigh in strongly and vocally in favor of continuing solar net metering, at least for the next decade or so. After that, perhaps new advances in batteries will vastly extend their duability, reduce the number of high intensity resources in their making, and "close the circle" on their life cycle.

Freeing the Grid: Net metering & interconnection from Freeing the Grid on Vimeo.



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