Why (Else) is Xcel Energy Trying to Axe Minnesota’s Community Solar program?

Date: 29 Apr 2015 | posted in: Energy, Energy Self Reliant States | 0 Facebooktwitterredditmail

In a filing Tuesday (April 28), Minnesota’s largest electric utility announced unilateral action within the next 30 days to reduce development under the state’s community solar gardens program by 80%, from nearly 560 MW to 80. It’s the latest in … Read More

Beyond Utility 2.0: Part 2 “The Present”

Date: 29 Apr 2015 | posted in: Energy, Energy Self Reliant States | 0 Facebooktwitterredditmail

Aggressive state policy and cost reductions for clean energy have created two business model crises for electric utilities: stagnant sales and exponentially rising production from distributed renewable sources. This is the second of four parts of our Beyond Utility 2.0 to Energy … Read More

Small-Scale Solar Contributes 13% of New Power Plant Capacity in 2014

Date: 10 Mar 2015 | posted in: Energy, Energy Self Reliant States | 0 Facebooktwitterredditmail

The growth of solar has continued at a furious pace, with a new record of 6.2 gigawatts installed in the United States in 2014. But the bigger tale may be the persistent growth of small-scale solar, on residential and non-residential … Read More

Why Are Residential PV Prices in Germany So Much Lower Than in the United States?

Date: 20 Sep 2012 | posted in: Energy, Energy Self Reliant States | 5 Facebooktwitterredditmail

Earlier this week, Lawrence Berkeley Labs released a marvelous comparison of residential PV costs in Germany and the United States, finally putting some detail to an enormous gulf in costs (nearly $3.00 per Watt).  The following chart (from page 35 … Read More

Solving the Local Clean Energy Puzzle

Date: 6 Apr 2012 | posted in: Energy, Energy Self Reliant States | 1 Facebooktwitterredditmail

In this April 2 presentation to the Pedernales Electric Cooperative of Johnson City, TX, ILSR Senior Researcher John Farrell discussed how solving the clean local energy puzzle requires much more than a consideration of cost per kilowatt-hour. Instead, cooperatives, municipal … Read More

Solar PV Economies of Scale Improve in 2010

Date: 15 Sep 2011 | posted in: Energy, Energy Self Reliant States | 2 Facebooktwitterredditmail

Installed costs for solar PV have dropped and economies of scale improved significantly in 2010, opening the door for much more cost-competitive distributed solar power. 

The data comes from the 4th edition of the excellent report from the Lawrence Berkeley Labs’, Tracking the Sun (pdf) and shows the installed costs for behind-the-meter solar PV projects in 2010.  The following merely copies Figure 11 from that report, showing the average installed cost of “behind-the-meter” solar projects in the U.S. in 2010, by project size.

This is useful and shows the significant economies of scale for solar PV in 2010, but the history is important.  For context, the following chart shows the 2010 data along with the 2009 data from Lawrence Berkeley Labs, with the grey shaded area indicating the cost decreases.  The 2010 installed cost data from the California Solar Initiative (red) is also shown, helping validate the LBNL data.  The last data point from the CSI is an outlier likely due to having too few projects in that dataset.

Two things are clear from the new data.  First, installed costs have dropped significantly, by $1 per Watt for residential-scale solar PV and by nearly $2 per Watt for megawatt-scale projects.  We can also see more clearly how the economies of scale of solar have improved, as well.

The unit cost savings between the smallest and largest solar projects (1 MW and under) jumped from $2.80 to $4.60 per Watt, a change in relative savings from 30 percent to 47 percent.  Economies of scale were also much greater for mid-size solar (30-100 kW), with the percentage savings over the smallest projects rising from 21 to 35 percent.   The following chart illustrates the change in economies of scale, showing installed costs as a percentage of the cost of a 2 kW system.

Instead of having relatively little economies of scale for solar PV projects larger than 2 kW, the 2010 data confirms that the unit cost of solar does continue to fall significantly as solar projects grow up to 1 megwatt (MW) in size.

Unfortunately, LBNL did not have sufficient data to provide context for economies of scale for larger distributed solar projects (1 to 20 MW), with only about 20 datapoints.  However, their finding was that these larger crystalline solar projects cost between $4 and $5 per Watt, showing small but significant scale economies.

The lesson is that solar economies of scale seem to be improving as the U.S. market matures, good news for distributed solar to compete with peak electricity prices on the grid.

[note: for more context, see the previous post on 2009 solar economies of scale]

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Clean, Local Power for Kentucky

Date: 31 Aug 2011 | posted in: Energy, Energy Self Reliant States | 0 Facebooktwitterredditmail

In August 2011, ILSR Senior Researcher John Farrell gave this presentation to a group of rural utilities and environmental organizations in Kentucky.  The slides illustrate the enormous renewable energy potential in Kentucky and the cost-effectiveness of clean, local power in … Read More

Lost in Transmission

Date: 25 Jul 2011 | posted in: Energy, Energy Self Reliant States | 0 Facebooktwitterredditmail

Update 7/26: One commenter asserts that the loss figures offered by the original author may be relevant in India, but do not reflect the U.S. grid, where losses total around 7%.  EIA data seems to reflect this [xls].

Can transmission losses completely offset economies of scale for solar power plants?  An article in Renewable Energy World argues against the building of multi-megawatt (MW) solar PV instead of on-site or local PV systems.  In particular, the author writes:

The biggest problem with the multi-MW solar PV plant is that it loses 12-15 percent of expensive power as it passes through a series of power transformers. PV solar inverters generate power at 400 [Volts] three-phase. In large plants, this power is first boosted to 66 [kilovolts] or more with several power transformers and then stepped down to 400V with another string of transformers to suit consumer requirements. In addition, there is a further transmission loss of 5-7 percent in the power grid. Why suffer an avoidable 20 percent loss of expensive solar power?

…There is thus no ‘scale advantage’ in large PV solar plants. In reality, all multi-MW plants are basically clusters of several 500-kW plants since solar inverter capacities are limited to about 500 kW and no more. Why not have one hundred 500 kW plants instead of one giant 50 MW plant?

With 20% of the power from a large-scale solar plant lost in transformers and power lines, it could seriously alter our previous analysis of solar economies of scale.  Here are the original charts, with the first chart shows our original analysis of solar economies of scale, with strong savings for scale for new projects (as reported by the Clean Coalition):

The next chart shows the economies of scale in the German rooftop PV market, as reflected in their feed-in tariff rates.  The percentages show the price in each size tranche relative to the price for the smallest rooftop PV systems.  Once again, there are significant savings for scale, especially when going from a project 100-1000 kW to one that is 1 megawatt or larger (15 percent).

But if there is a 20% power loss for the voltage stepping and transmission for larger solar projects, then when it comes to delivered power, small projects may perform better.  Let’s assume that projects 1 MW and larger require the voltage step and transmission (and incur the losses), whereas smaller plants do not.  The following two charts illustrate the difference.

The first chart takes the Clean Coalition (green line) data from the Solar PV Economies of Scale chart and calculates the levelized cost of the power from each size power plant based on the sunshine in southern California.  For the largest size solar power plants, the cost is adjusted for the losses due to transmission and transformer stepping.

As we can see in the first chart, the losses from transmission wipe out most economies of scale for large-scale solar, making 1 MW and larger solar PV plants equivalent to on-site solar power from a 25 kW solar PV array.

We can similarly examine the effect in the German case.  Here the government sets the price paid for solar by size class, and since it’s based on output at the power plant, large-scale plants that have transmission losses get paid for their entire power output, regardless of how much usable power reaches customers.  The following chart shows what German customers effectively pay for solar, assuming that 1 MW and larger facilities all experience the 20% transmission losses explained earlier.

 

As we can see in the chart, the cost of transmission can wipe out the economies of scale in installed costs, making large-scale solar comparable to solar PV of 30-100 kW, but without the same transformer and transmission losses. 

It may be true that the installed costs of solar PV continue to fall as projects get larger, but it’s clear that relying on the price of solar at the power plant does not accurately reflect the cost to the grid or ratepayers. For some size of larger power plants (1 MW? 5 MW?), the lost power from stepping up and down voltage through transformers and from transmission may largely offset the economies of scale from building a larger power plant.

Rather, mid-sized solar (or specifically, projects that can connect directly into the distribution system without changing the voltage) may deliver the best cost per kilowatt-hour.

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