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The EROI for solar electric panels of 6.7 seems low. At a minimum there should be a lot of room to increase the EROI of these panels by optimizing the production process. And that figure is probably based on the standard 5 hours per day of effective use for fixed solar panels. With feasible tracking systems 5 hours could be increased to 7.5 hours averaged yearly. That should be a 50% increase, which could bring the EROI to 10 for existing panels.

Also the time over which energy is returned from solar panels is often not adequately accounted in many measures. Energy Payback Time is the primary original merit factor, but Richards and Watt argue for use of energy yield ratio, EYR, instead, as it allows capture of the full lifetime of the panel. With 30 year lifetimes EYR can increase to >13, especially in areas of high insolation.

"It is not necessary to have hope in order to persevere."

by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Mon Jul 22nd, 2013 at 10:14:52 PM EST
... but by their nature, a meta-study of Solar PV EROI will lag technological progress, since it has to cover a sufficient period of time to collect an adequate number of EROI studies, and then it goes through its own publication process, which also takes time.

Just as with the EROI on Wind Power, I am taking it as a conservative floor estimate on EROI of the technologies over the coming decade rather than as a center-point estimate. That is, after all, the crux of the argument: that if we pursue the Steel Interstate now, we won't be left stranded because we banked on forthcoming successful technological research and development that never took place.

Contra that "what if the current technological progress hits a roadblock and this is the best we get" challenge, based on what we already know about technology we already have, we in the US can be confident of the technical feasibility of a renewable, sustainable Electrical power supply with an EROI of 13 or better, which is comfortably above the threshold of the EROI "cliff".

At the same time, petroleum and near petroleum substitutes continue to advance toward that cliff.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.

by BruceMcF (agila61 at netscape dot net) on Mon Jul 22nd, 2013 at 11:01:32 PM EST
[ Parent ]
I will also note that the effective EROI of the portfolio might be increased by surrendering some of the solar component EROI by fixed installations that orient the solar panel to the southwest (in the Northern hemisphere) or northwest (in the Southern hemisphere) if that results in an average power generation curve that better matches peak consumer demand, if that means less of the portfolio energy production is lost in storage conversions.


I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.
by BruceMcF (agila61 at netscape dot net) on Mon Jul 22nd, 2013 at 11:28:08 PM EST
[ Parent ]
Or develop cost effective tracking ability for the panel arrays.

"It is not necessary to have hope in order to persevere."
by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Tue Jul 23rd, 2013 at 02:54:37 AM EST
[ Parent ]
Cost of panels could well drop faster then labor cost of maintenance of tracking.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.
by BruceMcF (agila61 at netscape dot net) on Tue Jul 23rd, 2013 at 08:02:06 AM EST
[ Parent ]
To elaborate on that comment ...

This point is drawn from a paper about how many analysis of grid integration of sustainable, renewable power both exaggerate the problem and lay the blame for the inflexibility of "baseload" production at the feet of the sustainable, renewable power, when the inflexibility is the fault of the baseload power generator.

From the perspective of a member of a sustainable, renewable portfolio, the greatest benefit of solar PV is in the provision of peak power, and in most countries, the daily average power peak tracks the peak of daily average solar availability.

So the problem of optimizing a fixed location for delivery of power for sale to the grid is a different problem from optimizing a fixed location for delivery of power to a bank of batteries in an off-grid installation.

Even with a simple rotator tracking system, the optimal vertical angle of the solar array for the power needs of the grid may well not be the same as if optimizing total power delivery.

In other words, the assumptions by which simulations maximize simulated power production by the solar cells may also simultaneously make the challenge of integrating the solar cells into grid supply more difficult than it need be. A reorientation that improves the value of the power supply to the grid would reduce the individual EROI but either, if it allows less fossil fuel back-up, reduce total climate impact or, if it allows less storage to be used, increase the total EROI of the sustainable, renewable, energy portfolio.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.

by BruceMcF (agila61 at netscape dot net) on Wed Jul 24th, 2013 at 09:45:08 AM EST
[ Parent ]
I have done some analysis of the solar potential of the roof of my shop. Removing some trees to the south west of the shop would keep the roof in sunlight from 9AM to 4PM even on the winter solstice - 7 hours. A compound tilt mechanism that tilts the entire array up 20 degrees on the west in the morning and in the east in the evening, combined with individual panel tilt of up to 15 degrees in either direction would keep the entire array in its optimal zone for five hours a day and allow the array to operate at > or = to half efficiency for another two hours per day. But the ability of the existing structure to support such a system and the durability and maintainability of such a structure over 20 years of wind and rain by myself is highly questionable, given my present age of 70. :-) But it would offer about a third more generation which would be highly significant for off grid type applications. Too bad the wind resource is not greater locally.

"It is not necessary to have hope in order to persevere."
by ARGeezer (ARGeezer a in a circle eurotrib daught com) on Wed Jul 24th, 2013 at 10:42:48 AM EST
[ Parent ]
... "for off grid installations".

For off grid installations where the solar power is feeding a battery bank, increasing the performance of the solar panels on a marginal sun day can be a quite important benefit, since marginal sun days often come one after the other, and too many in a row can deplete the battery bank.

For on grid installations, given that wind power and possibly run-of-river hydro is likely offsetting your drop in daily solar peak supply, better to just have an UHVD line to a grid that has an independent complement of sustainable, renewable resources so that you can buy some from them when you are short ... because then you can sell to them when you have a surplus.

Which makes the simplicity of a fixed installation oriented to the average best performance for the needs of the grid quite appealing.


I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.

by BruceMcF (agila61 at netscape dot net) on Wed Jul 24th, 2013 at 11:48:28 AM EST
[ Parent ]

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